Home

LLG User Manual v2.50

1. MM 260 Features ED 260 CHAPTER 44 Sample Problem 19 3D CurrentS nsssssssssssssnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn nnmnnn 263 Input Sheet Main Page cccceccecceesneeeeeeeeeeeaeeceeeeeeceaaeseaeeeseaaaecaeeeeeaaaesaaeeesaaaeeseaeeeeeaaaeseaeeeseaesesaeeeessaeeeseneees 263 Input Sheet Layer Properties Page 263 Position Dependent Sheet Main Page and Params Page 263 Input Sheet Current Properties Page eterni nnne nnns nrnr nenne sintesi intent nens sentent 264 FOIS a TEE 264 CHAPTER 45 Sample Problem 20 Media iii e tton o Eheu eu ene tek a eaa esa a o pasa porno EE 267 Input Sheet Main Page cccccceccceceeeneeceeeeeeeeaeeceeeeeceaaeeeaeeeseaaaesaaeeeesaaaesseaeeeseaaeesgaeeecesaaeseaeeessaeseseeeeessaeesseaeees 267 Input Sheet Globals Page and Materials Page sessi 267 Input Sheet say ers Page n oii edi edt ti Re n EIER Ne Tb eB EEN 267 Position dependent Properties eseesesessessseseeeseeeeeeeeee eene tenen enn nnn nennen n tnnne een e 267 ESAS p pL 268 CHAPTER 46 Magneto Optical Simulations Supplement ecce eere erret 269 Installation InStr CtlOns uL eO ee ARA 269 Theory of Opera ui D du i dabo xe loath desc dog Eeer Hoe ipee Du eu eaten Le dte uci furias 269 A A EE T TEE P E E T TEA A P E EA ET E E E T E T 269 2 spin Model ER 270 Initiating a Magneto optical Calculation in UO 271 Specify an MO Calculation vis 1 ien ina
2. FIGURE 57 Input Data Sheet Hysteresis Non uniform Page You can select either a uniform hysteresis loop Hys U Page a non uniform hysteresis loop Hys NU Page a time dependent h field Time Dep H Page or a moving media problem Shields Page These are mutually exclusive only one mode can be used for a given problem 18 128 LLG Micromagnetics Simulator User Manual Chapter 18 Inputting Data Into LLG Hysteresis Non Uniform SPECIFYING HYSTERESIS FIELD SECTIONS To specify hysteresis field sections 1 E UU Check the Non Uniform box to enable Non Uniform hysteresis fields Use the arrows or the Field Section Specified edit box to indicate a field section starting with the first Enter the starting Limit 1 and ending Limit 2 field values for the indicated Field Section into the edit fields Enter the Number Of Field Points for that section While editing the Hysteresis Field Sections you can click DELETE SECTION to remove field points from the hyster esis loop To remove all the specified hysteresis sections click the Clear All button THE NEXT THREE STEPS MUST BE FOLLOWED PRECISELY OR YOUR INPUT WILL NOT TAKE EFFECT 5 8 You MUST load the Field Section by clicking the LOAD SECTION button Each section must be loaded since the same controls are used both to examine and to modify the field values Once you have loaded a section it is auto matically plotted in the OpenGL window Incre
3. DESCRIPTION VARIABLE LIMITS Loop Direction x y z gt mi 10 lt m lt 1 0 Hy hys Hy hys 1010 lt Hy hys lt 101 Hy hys Hy hys 1010 lt Hy hys e 0919 Hz hys Hz hys 1010 lt Hz hys lt 10 Hysteresis Points Nhys 3 lt Nhys 16384 LLG Micromagnetics Simulator User Manual 17 123 Chapter 17 Inputting Data Into LLG Hysteresis Uniform Main Globals Materials Boundary Computation Initialize Fields Current Layer Props Layer BCs Notes Batch Sf HysU f HysNU A HI 2 FMA v Shields n l Name Output File CH Hysteresis Field Viewing Options 3D Field View With Lines 2D Field View r Rotational T orque Magnetometer Loop Props gt Uniform Rotational C Cw COW n loops 1e et 2K Torque Magnetometer Props Torque TotalAngle of Scan degrees 350 0000 Projection xy 1 0000 0 0000 0 0000 r Maximum Uniform External Field Mei MES Gad Vedk 0 0000 Hx De 10000 10000 ee rds diae Ne desi 50000 Hy Oe 10000 10000 EE teg ge 0 0000 Hz De 10000 10000 Hysteresis Points Hmin Hmax NEE 11 Points 3 101 Accept Changes lt Main Control 3 Reject Changes FIGURE 54 Input Data Sheet Hysteresis Uniform Page SPECIFYING A UNIFORM LOOP 1 Check the Uniform box to calculate a uniform field points are uniformly distributed hysteresis loop This is t
4. FiLE TYPES LLG Micromagnetics Simulator supplies you with sample files in each format as well as master input files that contain all of the start up information necessary for initiating an LLG calculation These files are loaded or saved at different points in the input simulation and review phases The files are either ASCII or binary ASCII files can be edited in LLG s File Editor or Microsoft s NotePad The input pages use the standard Windows Explorer interface to search for all files Type of Data File Format Input Output Access Bitmap bmp Output Toolbar and Drop down Me Input Specifications lg param nput Input Control Direction Cosine lg dom nput Output Input Control Convergence Data llg conv Output Input Control Material Properties Io material nput Output Material Properties Pos Dependent Mag Fields lig inputhfield nput Output Boundary Conditions Hysteresis Field Profile lg hysfield nput Output Hysteresis Hysteresis Field amp Mag Io hys Output Hysteresis Magnetization Masks lg mask nput Output Mask and View Magnetic Field lg hfield Output Views Graphical Animation Movies lg movie nput Output Movie Playback Position Dependent Parameters llg_postion nput Output Position Dependent Color Map File lg colormap nput Output Color Wheel Index Shape File lg shape nput Output Position Dependent FIGURE 2 LLG File Types BITMAP BMP These binary files can be saved through the Tool Bar or the
5. FIGURE 86 Standard View Options FIGURE 87 Magnetization Direction Cosine 23 168 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation FIGURE 88 Magnetization Direction Cosine 3D Cone FIGURE 89 Magnetization Direction Cosine Arrow Slice X Domain FIGURE 90 Magnetization Direction Cosine Domain LLG Micromagnetics Simulator User Manual 23 169 Chapter 23 Simulation FIGURE 91 Magnetization Direction Cosine 3D Arrows rura wr DEE y X Mz Ms X MyMs 2 X MxMs X Mx Ms FIGURE 92 Magnetization Direction Cosine Contour and Bitmap You can superimpose 3D cones with shading and texture on a bitmap The procedure is as follows Thanks Tony a select bitmap mode b check the 3d check box c change orientation to theta 0 0 and phi 270 0 exactly d check arrow overlay e check cones f turn on the OGL lights This procedure will make attractive 3D shaded cone overlays atop the bitmap images 23 170 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation RESIDUALS CHANGE ITERATION With the Change lteration option you can visualize the vector field whose projections are the normalized residual vec tors along the three Cartesian axes The residuals are the result of the minimization or integration process and are defined within LLG as the vector difference between the current iteration s magnetization direction cosine
6. LLG Micromagnetics Simulator User Manual 14 111 Chapter 14 Inputting Data Into LLG Layer Properties EF Hysu HE HysNU l TimeDepH w Shields Main Globals Materials Boundary Computation Initialize Fields Curent Layer Props Layer BCs Notes Batch a Properties Of Ms emu cm 3 800 0 P m N Layers Ku2 erg cm 3 1000 0 Kud erg cm 3 1 Layer 0 0 8 0 Thick nm Kc era cm 3 0 0 mi 0 0 uerg cm 1 050 Aij uerg cm Ks erg cm 2 0 1 050 2 Rho uohmem 8600 2 1 050 2 ER AMR Ratio 0 012 Bilinear Biquadratic GMA Polarization 0 000 2j 0 000 0 000 0 000 Anisotropy Type Easy Axis Sl Be aise IX e Easy Axis Direction Cosines UNIAXIAL one vector Ax 1 000 Ay 0 000 Az 0 000 Easy Axis Direction Cosines CUBIC two vectors Ax 1 000 ay 0 000 az 0 000 100 Ax 0 000 ay 1 000 Az 0 000 010 Layer T WEE Material s Accept Changes E Main Control C 14 X Reject Changes FIGURE 51 Input Data Sheet Layer Properties Page 14 112 LLG Micromagnetics Simulator User Manual Chapter 14 Inputting Data Into LLG Layer Properties DESCRIPTION M emu cm VARIABLE M emu cm LIMITS 0 0 lt M 108 Ky erg cm Kyo erg cm 1010 lt Kuo 1010 Kya erg cm Kya erg cm 1010 lt Ka 101
7. Maximum Temperature K Laser Pulse Timing Rise Time ns Fall Time ns Peak Time ns End Time ns Laser Pulse Position width xo nm Yo nm Ro nm Velocity Vx nmns Temperature Pulse View Pulse View Pulse Tend pa K X Cancel FIGURE 153 Position Dependent Sheet MO Functional Temperature Probe Page LLG Micromagnetics Simulator User Manual 46 273 Magneto Optical Simulations Supplement Ts Eos CES cce E Qe Toti YN UPS MURS where 1 t t pe 1 E e peak for t lt Tpeak and oa Tpeak O T faa LES _ e Tra Tong T2 for Tpeak lt t lt Tena The input variables are obtained from the dialog as Ambient Temperature K Tamp Maximum Temperature K Tmax Rise Time ns 71 Fall Time ns t2 Peak Time ns Tpeak End Time ns Tenal Xo nm Xo Yo nm yg Ro nm Ro and Velocity nm ns vo In order to view the temperature pulse profile in time click the View Pulse button READ FiLE CONTAINING TEMPERATURE DATA When you click the Read Temp button you will prompted to enter a file name Then you will be offered the following dialog with options for processing your temperature data Remember since you are reading files not specifically designed for LLG you are responsible for ensuring that the file is properly formatted and that the data that you specify about this file in the dialog below is correct Custom MO Ancillary Input
8. a 1 1 A Ae AA LIT spp sd FIGURE 3 Journal Viewer Main Page OPENING AN OLD JOURNAL FILE To open and view an old journal file either click the Open File icon or select File Open from the drop down menu to activate the open file dialog The suffix for journal files is llg journal Select the file that you want to view to it load it into a journal file One journal file is shown below e The first left hand column contains the numbered journal entries e The second column contains the file s date and time of creation e The third column contains the file path name e The last fourth column contains the title line extracted from the file if it exists The title is the character string that is entered at the top of the Main Input Page 4 34 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files e Print the formatted journal file by clicking the Print icon amp LLG Micromagnetics Simulator Journal Viewer LLG Journall lig journal y File Edit View Format Window Help Dele H la 8 212 81 Base File Name g r u gl LLG Micromagnetics Simulator Journal Viewer Thursday July 26 2001 Complete File Hame Sample GS untitled E lg v2 0 workuntitled lig param untitled Tuer O workwuntitled Io param BatchTest lg v2 0 workBatchTest Io movie Samplet E Tuer OJworktestiSample Io movie Sample1 4 Odeg Sample15 Tllg v2 O workitestisample15 llg mov
9. LLG Micromagnetics Simulator User Manual 6 75 Chapter 6 Inputting Data Into LLG Main Clicking Accept Changes for Your Input to Take Effect EXCEPT for the Main Page you MUST click the Accept Changes button on each input page for your changes to take effect Since all of the Input Pages exist concurrently LLG needs some way of knowing that you intend the changes to be made to the LLG data Data I O in the Man Input Page is used to specify input data files and output data files SAVING DATA I O FILES When you load save the input parameter file when you complete data specification all output files are automatically created with the root name and appropriate file suffixes When you do not save or load the input files you are prompted by LLG for the required file names It is always desirable to save the input data files with new file names prior to starting a new computation The parameter files contain a complete ASCII representation of ALL input data Refer to Chapter 4 on Loading Saving llg Files for information on reading input and saving output files e Read Input Files Read Input Specify llg param file for input e Save Input Files Save v1 Input Specify llg param file for output v1 file Disabled in v2 50 e Save Input Files Save v2 Input Specify llg param file for output v2 file e Specify Output File Names Angle Config Specify llg dom file for output e Specify Output File Names Convergence Specify llg
10. Write Header String LLG Micromagnetics Simulator User Manual 4 43 Chapter 4 Loading Saving Files m fileStdio WriteString m strVersion n0 m strBuffer1 Format 966i966i966i m pLLG m nX m pLLG m nY m pLLG m n i m fileStdio WriteString m strBuffer1 n 0 Write Data for t Int k 0 k lt m pLLG m nZ k for t Int j 0 j m pLLG m nY j for t Inti 0 i lt m pLLG m nX i m nOffset OffSetComputer i j k m_strBuffer1 Format 15e 15e 15e 15e 15e 15e m pLLG m pX m nOffset m pLLG m pY m nOffset m pLLG m pZ m nOffset m pLLG m pHbcX m nOffset m pLLG m pHbcY m nOffset m pLLG m pHbcZ m nOffset m fileStdio WriteString m strBuffer1 n 0 m fileStdio Close return TRUE Arbitrary H Field Files t BOOL CDatalO WriteArbitraryFieldFile2_01 t_pChar pFileName t_pDouble pX t pDouble pY t pDouble pZ Open File if m_fileStdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate amp m fileException FileExceptionHandler amp m_fileException return FALSE Write Header String m_fileStdio WriteString m_strVersion n 0 m strBuffer1 Format 966i966i966i m pLLG m nX m pLLG m nY m pLLG m n i m fileStdio WriteString m strBuffer1 n 0 Write Data for t_Int k 0 k lt m pLLG m nZ k for t_Int j 0 j m pLLG m nY j for t Inti 0 i lt m pLLG m nX i m nOffset OffSetComputer i j k m
11. CHAPTER 1 LICENSE AGREEMENT AND HELEASE NOTES Rotational Loop LICENSE AGREEMENT Read this entire license agreement before using LLG Micromagnetics Simulator and its documentation hereafter collectively referred to as LLG If you are not willing to be bound by the terms of this license agreement promptly return LLG and its associated documentation to Michael R Scheinfein and your money will be refunded Program License Agreement Michael R Scheinfein Licensor has worldwide rights to copy publish sell license and distribute LLG You assume responsibility for the selection of the program to achieve your intended results for its installation and subsequent use and for the interpretation of the computed results Although every effort has been made to insure the stability and accu racy of the results produced by LLG Licensor is not responsible for any inaccuracies or errors produced by the user or through programming errors Grant of License Licensor hereby grants to Licensee nonexclusive single use license to use LLG upon the terms and conditions con tained in this agreement e You may use LLG on a single workstation owned leased or otherwise controlled by you You may copy LLG for backup purposes in support of your use of LLG on a single computer or workstation e You may transfer LLG and license to another party if the other party agrees in writing to accept all terms and con ditions of this Agreement If you tra
12. Global Spin Torque Accept Changes Material Main Control Selector Eme 2 Reject Changes FIGURE 36 Input Data Sheet Globals Page 7 80 LLG Micromagnetics Simulator User Manual Chapter 7 Inputting Data Into LLG Globals UsiNG THE MATERIALS DATABASE TO SELECT PARAMETERS There are two methods for using the Materials Database for entering parameters INPUT SEQUENCES FOR MATERIALS DATABASE Recommended Path Globals Tab Material Selector Materials Tab 1 Click the Globals tab 2 Click the Material Selector button to access the Materials Database to select parameters 3 Enter your data see the next chapter on Materials 4 Click the Accept button which returns you to the Globals Page 5 Enter data into the Globals Page if you Wish click the arrow to the left of Properties Of to enter a title for your material 6 Click Accept Changes which returns you to the Main Page Click the Material tab to access the Materials Database to select parame ters Enter your data see the next chapter on Materials Click the Accept button which returns you to the Main Page Click the Globals tab Enter data into the Globals Page f you Wish click the arrow to the left of Properties Of to enter a title for your material Click Accept Changes which returns you to the Main Page With the recommended sequence on the left in the t
13. Hy pys1 1010 T 2 ps Hy hys2 Hy hys2 1010 lt Hy hys2 S 109 Hy hys2 Hy hys2 AO lt Hy nys2 S 10 Hz hys2 Hz hys2 1010 Ha pys2 1010 Time Interval Steps Steps 1 Steps 16384 Time Interval Specified Tsect 1 Tsect S 16384 ac Fields hx hy hz hx hy hz 1010 lt hx hy h 10 ac Time t to ty to 1 ty to 16384 ac Frequency and Phase bc Oo lt bc lt 10 0 Time ps Step T 0 01 T 108 LLG Micromagnetics Simulator User Manual 19 131 Chapter 19 Inputting Data Into LLG H t and FMR Main Globals Materials Boundary Computation Initialize Fields Current Layer Props Layer BCs Notes Batch Jf Hell F HysNU A H 0 FMR v Shields n Read Save Time Dep Field 1 0 Files SA de x Name Output File Read Input File Save Input File v 1 0000 0 0000 0 0000 ret i EM Ee Der Gi 7 0000 Y 0000 E 0000 b 0 00000 i 0000 0000 c 0000 Hx Hy Hz T 1 ps 0 0 0000 0 0000 0 0000 T2 ps of 00000 0000 0 0000 TimeDepField Time Interval Steps 2 Scale Pos Dep Field Clear All Time Interval Specified 1 0 Intervals Loaded LOAD SECTION D Time Loaded ps Time ps Step Accept Changes M i 5 Reject Changes FIGURE 60 Input Data Sheet Time Dependent H Page 19 132 LLG Micromagnetics Simulator User Manual Chapter 19 Inputting Data Into LLG H t and FMR SPECIFYING PROJECTION DIRECTION The hysteres
14. FEATURES Structure 150 nm x 150 nm x 10 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 15x 15x 1 Material Permalloy Relaxation Time Dependence Initialization Negative X in the X Y plane Hysteresis Time Dependent Field 100 ps rise time to 500 Oe fast 40 250 LLG Micromagnetics Simulator User Manual Chapter 40 Sample Problem 15 Magnetization Dynamics In Permalloy Platelets NOTE In the graphic below the interplay between the energy components and the energy pump into the system of the applied field is visible 6e 10 5e 10 4 4e 10 4 P E 3e 10 4 2 2 2 2e 10 4 gt 2 2 te 10 4 LLI 0 EY 1e 10 4 2e 10 T T T 0 500 1000 1500 2000 Time ps FIGURE 143 Time Dependence of Energies in Fast Rise Time Switching Field LLG Micromagnetics Simulator User Manual 40 251 CHAPTER 41 Sample Problem 16 Solid Pyramidal MFM Tip iji III tie fi Vite j VI N N V I LOEGOCOCOEOEO OREO iis i II This sample problem illustrates the simulation of a solid MEM tip s magnetization INPUT SHEET MAIN PAGE 1 2 3 Initiate an LLG computation Enter the dimensions of the problem X nm is 200 nm Y nm is 200 nm and Z nm is 200 nm Enter the discretization for the problem N is 20 Ny is 20 and N is 20 INPUT SHEET COMPUTATION PAGE 1 2 3 4 Click the Computation tab Check Time Faster and enter 2 0 ns for the ps
15. Hj 108 OPTIONALLY REMOVE EFFECTIVE FIELD COMPONENTS The Demag Exchange and Anisotropy components to the effective field can be removed by checking the appropriate check box This allows analytic treatments of micromagnetics to be compared with results from LLG since demagneti zation fields are rarely if ever included in analytic treatments 12 104 LLG Micromagnetics Simulator User Manual CHAPTER 13 Inputting Data into LLG Current The Current Page is where you specify input currents Input current can be specified to flow in two or three dimen sions For two dimensions the current is injected along one axis of the structure The current that flows along each cur rent filament is a result of computing the series and parallel resistance along the straight paths to the other end of the structure Current will flow only along the specified axis When 3D currents are required LLG computes the current flow using finite differences 3D current requires complex data specification and memory must be committed A description of the variables is given below and a view of the Input Data Sheet Current Page is shown on the following page DESCRIPTION VARIABLE LIMITS Current uA Le 0 0 lt ly 106 ac Current uA lac 0 0 lt lap lt 106 b Current Frequency 1 ps b 0 0 b 106 c Current Time Shift ps C 0 0 c 108 t ac Start Time ty 108 lt t lt 10 t ac St
16. The Color Table allows you to select separately the number of active regions Level 2 through Level 4 the angle to start end that region center and the color Color 1 through Color 5 to interpolate to at that direction cosine 1 Check a Level box 2 Click a Color box which redirects you to the OGL Color Sheet Color Page just described 3 Select a color from the Color Page 4 Click the Table tab to return to the Color Wheel Table The selected color is automatically loaded into the Color box for the selected Level The color table itself can be shifted with the slider at the bottom left Once you find your favorite color table selections save them for future use Color table files can be Saved or Loaded by clicking the appropriate button You must click the Apply or Reset button to activate a new color table for the actively selected OGL view Please note that the direction cosine range must be monotonically increasing i e 1 0 Level 2 Level 3 Level 4 Level 5 1 0 LLG Micromagnetics Simulator User Manual 5 67 Chapter 5 LLG Environment OGL INFORMATION SHEET The OGL Information Sheet provides utilities and information about your system These features are provided for con venience and offer no extra features beyond those of Windows NT There are five sub pages 1 Info 2 Disks 3 Output 4 Clock and 5 Calculator You can toggle between the pages by clicking the appropriate tab OGL INFORM
17. e The media Mg saturation magnetization e The media thickness T nm e The transition width W nm e The transition length L nm When the media is scanned in front of a sensor you must specify the following e The direction in which to vary the position X Y or Z The minimum position Min nm e The maximum position Max nm e The number of Steps used to complete the movement Please remember to click the Accept Changes button to record your changes to LLG s internal data structures 20 136 LLG Micromagnetics Simulator User Manual Chapter 20 Inputting Data Into LLG Shields DESCRIPTION VARIABLE LIMITS Shield Attributes for both shield above and or shield below in appropriate column Distance to Shields Ds 0 0 D 106 Shield Thickness nm Ts 0 0 T 108 Distance 0 gt Shield Edge X Dxjert 0 0 lt Dy ter lt 108 Distance Nx gt Shield Edge X Dx right 0 0 D ign lt 109 Distance 0 gt Shield Edge Y Dy front 0 0 lt Dy front 10 Distance Ny gt Shield Edge Y Dy back 0 0 lt Dy pack S 10 Permeability Mu MuO u 0 u 108 Response to Model atan Media Charge Il To X Y or Z X Y or Z X nm X 106 X 106 Y nm Y 106 v lt 106 Z nm Z 106 Z 108 Scan Media Min nm Min 106 Min lt 106 Scan Media Max nm Max 106 lt Max 106 Scan Media Steps N OS
18. oooocconccccnnocccncoccnononannnnanc nono nnnnnn cono nora nr rra nennen rens nnne en 176 reds ES 178 Time Dependent Field H t Current i t and FMR Visualzaton n 178 Movies Page niste Rp eot pe Heap tere eee pe ea iuter een Ene d t Du e POT 180 Saving a Movie to Disk ona Efe te pe He DH excu eed LESE EC EE e EO D e ROT ede 180 Saving Domain States during a Hysteresis Loop eene nennen nennen nennen inns nnne 180 ell el d mE 181 Fields Page uuibunderut guten pee Ee name eee EE 182 B Probe Page C et 183 Closing Down a Calc latior 2 ien ee edet iddesi dea cava gae Set ERR Uca PER use ce RET aede eed rusa 183 Guidelines for Running LLG Simulations enne eene nennen nnns etri innen 184 Guidelines for Setting up Problems and Decreasing Computation Time 185 Movie Page Simulate a Movie Option sess eene nsn nnnr inns nnns sen nensis nns 186 Batch Mode Processing reete eh ee aeu e eate etate pte ec reb espe dad 187 Setting Up the Batch Mode Executable enne en nennen nr intrent nnn nr seiner inneren nen 187 Loading Batch File utr orte reete eie ear pp a i pek UR 187 Clearing a Batch NI nennen nennen trend nennen inns 187 Elle ERT 187 Pausing a Batch Mode Calculation iieii iaeiiai a a nr Nai aa 188 Monitoring a Batch Mode Calculation sessi cnn rca crac 188 Setting Up a Batch Mode Process enne eterne ns near 188 Edting Batch Files EET 188 Externally Controlling Batch Mode Processi
19. 4 Initiate an LLG computation Enter the dimensions of the problem X nm is 640 nm Y nm is 320 nm and Z nm is 30 nm Enter the discretization for the problem N is 64 Ny is 32 N is 3 Check the Layers box INPUT SHEET LAYER PROPERTIES PAGE 1 0 6 No bk ab Click the Layer Props tab Enter 30 into the Layer T nm box Click the Material button Select Permalloy from the Materials Page and click Accept Click the LOAD LAYER PROP button Click Accept Changes Check the Pos Dep box under Structure Properties Check the Commit Size box which enables the Mask and PosDep buttons Click the PosDep button which brings up the PosDep Input Sheet position DEPENDENT SHEET MAIN PAGE AND PARAMS PAGE 1 Left click on the graphics window to enable the drawing tool Use the drawing tool to make a circle in the center of the structure as in the figure above Select All Layers Click the Params tab Check the resistivity Rho box and enter 999999 LLG Micromagnetics Simulator User Manual 44 263 Chapter44 Sample Problem 19 3D Currents Check the box next to the drop down menu and select a color Also you MUST check the CO box in the Graphics Control for the color to appear in the graphics window Click the OGL Props tab then click the Modes tab to access this feature Right click on the circle and select Fill Region with Parameters This sets the resistivity in the hole Save an Ilg_postion file and Cl
20. Uniaxial U or both U C When the system is not layered see below the anis tropy is uniform throughout the simulation structure e For Uniaxial anisotropy the Easy Axis Direction Cosines are enabled Enter the direction of a vector along which the easy axis will be oriented For this you need to enter one vector or direction only You need not normalize the vector you can enter components between 1 and 1 as the program does this for you For example if you enter 1 1 and 1 click Accept Changes exit and re enter the page the selections appear as 0 57 0 57 and 0 57 e For Cubic Anisotropy the cubic options are enabled This is somewhat more complex since a plane or two direc tions must be specified You must enter two orthogonal vectors because the symmetry is perfect cubic The pro gram will set them to Ax Ayo Ay Ay Az1 Az 0 The third vector is defined internally from the cross product In principle you can define any direction as long as the orthogonality condition for the cubic case is fulfilled e f you select C U both options are enabled and must be defined SPECIFYING THE EASY Axis X Y Z AND ANY You can specify the direction of the easy axis using either the X Y or Z buttons or by selecting the Any button and entering the vector s direction in the easy axis direction cosine vector A directly CONVENTION FOR BULK INTERFACE AND SURFACE ANISOTROPY COEFFICIENTS When the anisotropy coefficients are posi
21. 3 Click Accept Changes to log your changes INPUT SHEET TiME DEP H PAGE 1 Click the Time Dep H tab 2 Check the Time Dep Field box to activate the time dependent fields 3 Enter 100 into the Time Interval steps edit box Leave the Time Step ps at 1ps This will be the rise time for the field that is 100 x 1ps 100ps 4 Enter 0 0 Oe and 500 0 Oe into the H T 1 ps and H T 2 ps edit boxes respectively These are the fields at t 0 and t 100 ps respectively Click the LOAD SECTION button to log that section into the data structure Increment the Time Interval Specified to 2 Enter 1900 into the Time Interval ps edit box This will be the rise time for the second part of the field interval Enter 500 0 Oe and 500 0 Oe into the Hy T 1 ps and H T 2 ps edit boxes respectively no change These are the fields at t 100 and t 2000 ps respectively 9 Click the LOAD SECTION button to log that section into the data structure 10 Click Accept Changes to log your changes Run the problem COMMENTS Use the 2D Graphics utility see page 31 to load Sample15 llg conv file On the y axis check E total E exchange E anisotropy E demagnetization and E external You will see the subtle interplay of the energies as the problem drives towards a solution Also note that as the field is increasing in time the total energy is not constrained to decrease until such time as the field is turned off or maintained eonun
22. ACOEF M LJ K Graphical Animation llg movie Type Format Where Prompt Suffix Variables LLG Movie File Unformatted BINARY Movie Dialog Load File lg movie IO MOVIE VER integer currently 6 identifier NX integer number along x direction NY integer number along y direction NZ integer number along z direction HCOUNT integer number of movie frames FRAME integer number of the frame HX double precision hysteresis field in Oe along x HY double precision hysteresis field in Oe along y HZ double precision hysteresis field in Oe along z MX double precision remanence along x direction MY double precision remanence along y direction MZ double precision remanence along z direction HHYST double precision magnitude of field in Oe MHYST double precision magnitude of remanence along field MR RES double precision resistance in ohms MR VOLT double precision voltage in volts ANG_X double precision magnetization direction cosine x ANG_ Y double precision magnetization direction cosine y ANG_Z double precision magnetization direction cosine z READ UNIT IO MOVIE VER IO MOVIE VER IO MOVIE VER IO MOVIE VER READ UNIT NX NY NZ HCOUNT DO 200 FRAME 1 HCOUNT READ UNIT FRAME READ UNIT HX FRAME HY FRAME HZ FRAME READ UNIT MX FRAME MY FRAME MZ FRAME READ UNIT HHYST FRAME MHYST FRAME MR RES FRAME MR VOLT FRAME DO 100 I 1 NX DO 100 J 1 NY DO 100 K 1 N
23. Chapter 26 Sample Problem 1 Basic Data Input for an Fe Cube INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Click the Vortex Z Plane button 3 Click Accept Changes which exits you to the Main Page You can save your input configuration to a file by clicking the Save v2 Input button 4 Click the Begin Simulation button SAVING FILES If you have not saved the new input parameters LLG will prompt you to do so If you respond yes you will be prompted a second time for the name of the input file llg param By default the program will create two more files a domain file with the direction cosines on output llg dom and a convergence file with iteration histories and energy values llg_conv Each file will have the prefix of your llg param filename If you select NOT to save the input parameter file LLG will prompt you to enter llg dom and llg conv filenames If you select NOT to enter filenames LLG auto matically creates the two files in your running default directory and names them untitled llg dom and untitled llg conv Once files have been specified a progress meter at the bottom left tracks the computation of the demagnetization field coupling tensor SIMULATION SHEET SIMULATION PAGE Once the coupling tensor has been computed the LLG Simulation Sheet appears 1 Click Surface 3D Graph Type to see a three dimensional view of the Fe cube 2 Click the Arrow button under 3D Objects to see the surface
24. INPUT SHEET FiELDS PAGE 1 Click the Fields tab 2 To make a poor approximation to the tip pin with Hz Oe 10000 for layers 4 10 Click the Load H Pin button after you enter each layer s field 3 Click Accept Changes to log your changes INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Initialize using a Vortex in the Z Plane 3 Click Accept Changes to log your changes MASK EDITOR Check the Commit Size box on the Main Page Either load the mask provided or make a solid cylindrical tip 6 cells across and from layers 4 10 Layers 2 and 3 should be vacuum or masked out COMMENTS The strong stray field from the magnetization of the tip is enough to grossly perturb the equilibrium magnetization of the sample FEATURES Structure 500 nm x 500 nm x 100 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 50 x 50x 10 Material Permalloy Initialization Vortex in Z 43 260 LLG Micromagnetics Simulator User Manual Chapter 43 Sample Problem 18 Sample MFM Tip Interaction FIGURE 148 Magnetization Perturbed by the MFM Tip 43 261 LLG Micromagnetics Simulator User Manual CHAPTER 44 Sample Problem 19 3D Currents In this sample problem 3D current input is demonstrated Although in this sample the 3D currents are generated and examined in and of themselves it is clear how such currents can be incorporated into a larger and more complex prob lem INPUT SHEET MAIN PAGE 1 2 3
25. OG GG 00000000 060 FIGURE 11 2D Graphics Menu color coded to match graph colors 5 56 LLG Micromagnetics Simulator User Manual Chapter 5 LLG Environment 5 The Print OGL Window button allows you to print the active OGL window to any Windows supported printer 6 The About LLG button activates the About LLG Dialog Box n LLG Micromagnetics Simulator E Your Computer System Number of CPUs 1 Memory MB 536 Processor Architecture INTEL Free Memory MB 305 Processor Type 686 Free Memory 568 Processor Revision 11 Processor Stepping il lig Version 2 50 lig Input File Version 2 13 Copyright 1997 2003 MR Scheinfein Dated Version Release 23 June 2003 FIGURE 12 About LLG Dialog Box 7 The Help button activates help 8 The Editor button activates the LLG File Editor It has the same functionality as Notepad and WordPad which you can activate directly from the LLG Editor with the appropriate buttons The Editor has its own Toolbar Rate jen La Tops Dux gt CG CH Bos em ve omg peni P ira LL Mamans Lond Pet 21 enden mens a 135 FIGURE 13 LLG File Editor LLG Micromagnetics Simulator User Manual 5 57 Chapter 5 LLG Environment Dur ele gt o mE E FIGURE 14 LLG File Editor Toolbar The functions of the LLG Editor Toolbar icons are moving from left to right 1 Open File 2 Save File 3 Close Editor 4
26. PPT EZE SJETTE AAAS EIERE E EA NEE EE E E EE EE EE AXATI ES EE RAKE OY THRE RRR WANN toe ELLE KELLER TATA amp wA ARR AA ttt E AER eA e REx ERO RET LEE TEES ARRAN SERA Kj RARATTRAR Ac check hh AAA ELE ET ER LEE R t A 8 D H AMAAP EZE SEA 1 ttt ttt ttt ttt tt t V gt gt gt gt gt gt gt gt t Y YA Y Y Y y gt gt gt gt EE pp pp pp pp pp pp gt gt gt gt gt gt EE EE EE EE E op op op op op op op op op e op op op op Here tt theeeet 41 y te LE H dp Lecce 5 A gt gt EE EE EE EE E RR A A i D y y y y y y y y y y y y gt er dp 7 47 eee eee eee eee eee tt er em en te te tm tm tm tm ere LLG Micromagnetics Simulator User Manual For simulations at finite temperatures a configuration with a Random Fraction of the magnetization can be selected a number between 0 and 1 0 LLG uses a gaussian random number generator to superimpose a random component on You can select a completely random initial state by checking the Totally Random option top of the zero temperature configuration selected RANDOM INITIAL CONDITION BRRAERKR TR ERA OA ARK KKK NARR AA EK EAR EZE ELLE TELE LCE ER E DEER DCH SE E EE E ERR ARE RR THEE PERB TAR AKER KAN PR SHREK rs RRR EELER FIGURE 45 1000 nm x 500 nm x 10
27. Sample Problem 13 Bulk Terminated Bloch Wall in Fe INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Click 2D Narrow Wall as the initial condition and 2D X Directed fields 3 Exit the page by clicking Accept Changes 4 Complete the initialization by clicking the Begin Simulation button Run the problem COMMENTS Notice that the sub element size was specified to be about 7 nm This is near the upper limit that yields converged solu tions for Fe Also note that the Simulation Volume was set large in case the resulting micromagnetic structure was con strained due to the boundaries FEATURES Structure 500 nm x 500 nm Sub Element 7 14 nm x 7 14 nm Discretization 70 x 70 Material Fe Relaxation 1 Pt Energy Minimization Initialization Narrow Wall Dimensions 2 Boundary Cond Left M 1 0 and Right M 1 0 Linne A LARA x de R ooo E EE RT B R RA Tt tt tt tt tt tt tt tt tt tt tt tt tt tt tt tt tt tt tt tt tt tf tt tt ff tt tt ft f ff tt FIGURE 140 Magnetization Pattern in Cross Section Near the Top of the Bulk Terminated Bloch Wall 38 244 LLG Micromagnetics Simulator User Manual Chapter 38 Sample Problem 13 Bulk Terminated Bloch Wall in Fe FIGURE 141 Magnetization Pattern in Bitmap and Contour Near the Top of the Bulk Terminated Bloch Wall LLG Micromagnetics Simulator User Manual 38 245 CHAPTER 39 Sample Problem 14 Easy
28. Time Step Select the 3D Complex FFT method Click Accept Changes to log your changes INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 2 3 4 5 Click the Globals tab Click the Material Selector button Select Co from the Materials Page Click Accept The Co properties should be entered in the edit fields of the Glo bals Page Choose Z as the easy axis Click Accept Changes to log your changes INPUT SHEET INITIALIZE PAGE 1 2 3 Click the Initialize tab Initialize the magnetization along Negative Z Click Accept Changes to log your changes INPUT SHEET BOUNDARY CONDITIONS PAGE 1 2 3 Click the Boundary tab Set the magnetization along M to 1 for the Top Z z N Click Accept Changes to log your changes LLG Micromagnetics Simulator User Manual 40 253 Chapter 41 Sample Problem 16 Solid Pyramidal MFM Tip MASK EDITOR Check the Commit Size box on the Main Page 2 Click the Mask button 1 3 Either load the mask provided or make a pyramidal shaped mask COMMENTS Even the strong anisotropy of Co is not enough to saturate the magnetization of the tip FEATURES Structure 200 nm x 200 nm x 200 nm 10 nm x 10 nm x 10 nm 20x20x20 Co Sub Element Discretization Material Negative Z Initialization 3335 gt gt gt gt gt gt gt 3 gt gt 33 gt 333 33233 gt gt gt gt gt 3 3333333333 E bk dn de dr de A A Z Ae AE EE EI gt gt gt g
29. click the OK button to generate the journal You will hear the disk being searched the length of the search depends on how many disks you specify and on the speed of your disk drive LLG Micromagnetics Simulator User Manual 4 37 Chapter 4 Loading Saving Files SUMMARY OF INPUT AND OUTPUT FiLE FORMATS OF V1 Position Dependent Magnetic Fields llg inputhfield Type Format Where Prompt Suffix Variables External Position Dependent Field File Formatted ASCIT Boundary Condition Dialog Read H File Write H File lg inputhfield NX number along x direction NY number along y direction NZ number along z direction HX field in Oe along x direction HY field in Oe along y direction HZ field in Oe along z direction READ UNIT 1 NX NY NZ 1 FORMAT 3I5 DO 10012 1 NX DO 100 J 1 NY DO 100 K 1 NZ 100 READ UNIT 2 HX LJ K HY J K HZ LJ K FORMAT 3F15 3 Material Properties lg material Type Format Where Prompt Suffix Variables External Materials Data Base File Formatted ASCII Materials Dialog Open Data Base Write Data Base lg material NUM number of database entries DB LABEL identifying label for material DB CA exchange constant in u erg cm DB MS saturation magnetization in emu cm 3 DB CK uniaxial anisotropy in erg cm 3 DB CKC cubic anisotropy in erg cm 3 DC CS surface anisotropy in erg cm 2 DB RHO resistivity in u ohm cm DB AMR anisotropy magnetoresistance D
30. or column 2 D of boundary cells bounding the discretized region These boundary cells con ditions can reflect the continuous uniform magnetization distribution present within the domains themselves on either side of the structure If no boundary conditions are specified the cells at the edges are free In the absence of surface anisotropy the normal derivative of the magnetization distribution at the surface is zero 2 13 In the presence of sur face anisotropy the Rado Weertman boundary conditions is used 13 14 Fundamental to the solution of the micromagnetic equations is the assumption that the bulk saturation magnetization M emu cm is constant microscopically throughout the ferromagnet The parameter Mg represents saturation magne tization at room temperature For most practical systems being considered Fe Co or Permalloy there is little devia tion in Ms at room temperature from the 0 K value The value of the magnetization vector Mir at each point within the ferromagnet is the saturation magnetization multiplied by the direction cosines that is M r M r My r Mz r Mgodr Ms or B r y r The constraint equation implied by the constant magnetization assumption is orl 1 The individual contributions to the energies in this continuum model are calculated by integrating the energy expres sions over the structure in question The energy integrals below are integrated over the appropriate dimension dV The exchan
31. r Mask File 1 0 Yellow Mask On Blue Mask Off Read Mask Save Mask The Demag Edge Is Unspecified Accept Changes Main Control 3 Reject Changes Close Picker Tool Move Selected Region Delete Selected Region Edit Selected Region Coordinates Save Selected Region Fill Selected Region Sample Selected Region Histogram Specify Selected Region For Edge Property Effects Review Edge Region Coordinates When you use any of the Mask Editor Pages right click on the active graphic for the options above These features can be performed on exist ing graphics Rectangle Polygon Circle Ellipse Curve Clear All Regions Load Region From File Black Red Green Blue When you use any of the Mask Editor Pages right click on the background of the window for the options above which are for creating or loading new graphics FIGURE 64 Mask Editor Sheet Main Page There are two options and Mask Editor Pages for specifying masks The first option is to specify a mask through the Main Page using the instructions that follow the second option is to import a bitmap jpeg or targa file through the Bit map Page see page 142 21 140 LLG Micromagnetics Simulator User Manual Chapter 21 Inputting Data Into LLG Mask Editor SPECIFYING MASK PROPERTIES OPTION ONE One you have defined the appropriate shape you can define how to act on the points either i
32. tena tpeak ttan When tpeak lt t lt tena and O again when t gt tena You can view the pulses with the simple viewer Remember to accept your changes to activate the field pulses and to check the check box at the top of the dialog to indicate this LLG Micromagnetics Simulator User Manual 13 109 Chapter 13 Inputting Data Into LLG Current This tool should provide facility to explore pulse timing issues important in defining optimal MRAM device characteris tics MRAM Field Pulses r Bias Line Field Properties r Bias Line Field Properties pE Ton ps D Ton ps 0 Hele 70 Tp s 10000 ELE 7 Tp s 10000 Hy Oe y Tend ps 20000 Hb O fendips 20000 oz el 0 Trise ps 1000 Hefe D Trise ps 1000 Tfall ps 1000 Tfall ps 1000 Write Line Field Properties gt Write Line Field Properties LLL mo Ton ps 5000 x Ton ps 5000 Fabel 3 Tp ps 15000 Pis Oe i gt Tp ps 15000 Hy 0e Tend ps 25000 FP Bs Tend ps 25000 Hz Qe 0 Hz De 0 Trise ps 1000 Trise ps 1000 Tfall ps 1000 Tfall ps 1000 v Activate MRAM Field Pulses v Activate MRAM Field Pulses Field Pulse Bias Line Field Pulse Write Line 0 0 View Write Tend 0 0 View Bias Lveewiee Tend Val OK Cancel Sel OK Cancel FIGURE 50 MRAM pulse Timing bias left and write right 13 110 LLG Micromagnetics Simulator User Manual CHAPTER 14 Inputtin
33. v Enable Disable Update Indicators Enable Disable Lek File Check Check Lek ms 5000 L ol Iterations Residuals 0 ann e Files Processed 3 5 361e 003 llg v2 0 work test Sample3 llq_param ODays DHours O Mins 4 Secs I Mlg v2 0 work test S ample2 llg param a ac Lg Pause Cac D OrwakuesnSamplet lg parom D Batch Processed 100 Fies ToProcess 4 T Mlg v2 0 work Veiane l param ODays O Hours D Mins 30 Secs Mlg v2 0 work test S ampleS llg param Stoo B en EMlefv2 0 workwestNS ample amp lla param 2 Mlg v2 0 work test S ample7 llg param Output Messages From LLG Kemel Displayed Below Processing Time O Days 0 Hours 0 Mins 11 Secs S Processing File I Mg v2 0 work test S ample3 llg param Processing Complete Processing Time O Days 0 Hours 0 Mins 6 Secs H Processing File I Mg v2 0 work ech Gampled llg param E For Help press F1 Calculating Memory Load Pct 22 Available Memory MB 419 6 FIGURE 113 Batch Mode Interface LOADING A BATCH FILE To load a batch file click the Load Batch File button The suffix for batch mode files is llg batch You will see a list of files loaded into the Files to Process list control CLEARING A BATCH MODE FILE STREAM To stop or clear a batch mode processing completely click the Stop Batch button The files that remain to be pro cessed and those that have been processed will be cleared STARTING A BATCH PROCESS To start a batch process cl
34. you must specify position dependent files and mask files independently from the batch process it is not practical to have 100 000 parameters to vary LLG will also write a new title containing the original file name and the problem variance number as well as specify which parameters are being varied in comments 5 10 see Notes IO above BATCH MODE POSITION DEPENDENT PARAMETERS There is a protocol for using batch mode computations using shaped boundaries and position dependent parameters and this procedure is summarized here in the order in which is must be implemented 1 Make the appropriate lg param file and store it 2 Go back to the mask editor and make the appropriate llg mask file and store it 3 Goto the position dependent parameters sheet and make and edge for shaped boundaries and activate it You will see now that additional cells have been turned on 4 Store the llg position file 5 Store the llg shape file 6 Go back to the mask editor and store the new lg mask file with the corrected number of cells activated usually overwrite the old mask 7 Goto the batch page and check the mask position dependent parameters and shape file check boxes Load the appropriate file names into the fields provided 8 Resave your log param file 9 You can now make variations on this lig param file if you choose 10 Use the scripter to make a batch file with all of your llg param files included 11 Run your batch mode
35. 0 0001 and observe the differences in the solutions Since the Save button was checked on the Main Page the convergence output file for this example includes a complete iteration history FEATURES Structure 150 nm x 150 nm x 10 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 15x 15 x 1 Material Permalloy Relaxation 1 Pt Energy Minimization Initialization Uniform in X Hysteresis Uniform H 1000 Oe Ny 11 FIGURE 126 Surface Magnetization Pattern and Hysteresis Loop during Switching in 3D Arrows LLG Micromagnetics Simulator User Manual 28 209 CHAPTER 29 Sample Problem 4 Rotational Hysteresis Loop for a Magnetic Platelet This sample problem is of modest complexity In this simulation a volume is descretized a single material property is set and a uniform rotational hysteresis loop is specified INPUT SHEET MAIN PAGE 1 Initiate an LLG calculation by clicking on the New icon in the tool bar 2 Enter the Simulation Volume with the slide bars or edit boxes 150 nm for X nm 100 nm for Y nm and 10 nm for Z nm 3 In the adjacent discretization boxes enter 15 sub elements for N 1 for N and 10 for N INPUT SHEET GLOBALS PAGE MATERIALS PAGE 1 Click the Globals tab 2 Select U Uniaxial in the Anisotropy Type group box The uniaxial anisotropy edit field K should be enabled and the C Cubic anisotropy K edit field should be disabled 3 Click the Material Selector button which
36. 10 on the LLG Input Sheet Main Page However if there are loose spins at an edge or corner the simulation will not reach the exit criterion For such cases choose the Average exit cri terion and set the Convergence limit to about 1 10 of the value used for the maximum method or 13 x 10 for the above example EXCHANGE AND CORRELATION Decreasing computation time without sacrificing the integrity of the rendered solution is a challenge There can be a problem by which the physical size forbids using an appropriate mesh In other words sometimes there are not enough pixels to go around This leads to the problem of coarse grids When the discretization scheme is necessarily coarse the exchange terms break down All other micromagnetic effective fields are continuous variables The demagnetiza tion and anisotropy fields are length scale invariant The demagnetization fields have geometrical factors that change the value but a uniformly magnetized cube has the same field in its center no matter what size it is However in a micromagnetics context the exchange field is defined as a second derivative which means that the effective field scales with the mesh as 1 D This causes a problem and means that there is in fact a preferred discretization scheme which when implemented is correct and gives proper dynamics Furthermore on coarse grids the approxi mation of continuous changes in M breaks down that is as an 180 wall distributed across
37. 35 SC BCC and FCC Lattices on 3x3x3 Sites Viewed 10 off the x y Plane and 30 off the y z Face 77 FIGURE 36 Input Data Sheet Globals Page 1 et tte 80 FIGURE 37 Input Data Sheet Materials Page 0 cette 84 FIGURE 38 Input Data Sheet Boundary Page 0coococccocco rh 86 FIGURE 39 Input Data Sheet Computation Page ssssssesseeell rn 90 FIGURE 40 Input Data Sheet Initialize Page llli eh 98 FIGURE 41 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Uniform Magnetization 99 FIGURE 42 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Transition Magnetization 99 FIGURE 43 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Vortex Magnetization in Y 100 FIGURE 44 Two dimensional 10 nm x 40 nm Permalloy Domain Wall Narrow Initialization 100 FIGURE 45 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Totally Random Magnetization 101 LLG Micromagnetics Simulator User Manual xiii List of Figures FIGURE 46 FIGURE 47 FIGURE 48 FIGURE 49 FIGURE 50 FIGURE 51 FIGURE 52 FIGURE 53 FIGURE 54 FIGURE 55 FIGURE 56 FIGURE 57 FIGURE 58 FIGURE 59 FIGURE 60 FIGURE 61 FIGURE 62 FIGURE 63 FIGURE 64 FIGURE 65 FIGURE 66 FIGURE 67 FIGURE 68 FIGURE 69 FIGURE 70 FIGURE 71 FIGURE 72 FIGURE 73 FIGURE 74 FIGURE 75 FIGURE 76 FIGURE 77 FIGURE 78 FIGURE 79 FIGURE 80 FIGURE 81 FIGU
38. 5 LLG Environment Click the Close Movie button to end a movie session cleanly You need not exit the Movie Viewer to view additional movies To view a new movie just load a new one EDITING OR CREATING MASKS Click the Masks button to edit or create masks page 139 This is useful for preparing masks for the move hysteresis utilities SPLITTING A MOVIE Somtimes movies grow beyond your physical memory limit LLG has two mechanisms to split movies By pressing the Split Movie button LLG will automatically try to split a movie There have been some problems in splitting movies that were too large for the memory of your machine especially when the exit from the simulation was not done correctly You must click the Close All button when a simulation is complete in order to write the correct frame number in the movie file By checking the Manual box you activate the manual movie splitter where you can enter the frame count of the movie file and LLG will split that file into two nearly equally sized files without bombing The equation used to estimate the number of frames is given on the dialog page Manual Movie Splitter Read Movie File To Manually Split Frames Size 24NxNyNz 128 24NxNyNz 92 Nx 64 Size 3148012 Ny 32 Frame Estimate 61 Nz 3 Frame Count sg FIGURE 120 Manual movie splitter LLG Micromagnetics Simulator User Manual 25 197 Chapter 25 Viewing Movies MOVIE PLAYER EXTRACT HYSTERES
39. CHAPTER 13 Inputting Data into LLG Gurrent ssmeemessssssasepsssandanessenstansnnsennnnannssannseddensas san EEN 105 Reading and Saving Time Dependent Current Input and Output Files esses 107 Specifying a Time Independent Cumrent eene nennen tenenti sen rene nennen nnne 107 Specifying a Time Dependent Current sse eene nennen unnn Ennn nnn sen rennen innen 107 Superimposing Sinusiodal ll a oce cec it ee asbie ede b de vue De dett SE eve ai 107 LLG Micromagnetics Simulator User Manual v Table of Contents Specifying Spin TOrQues REM Selecting 2D Quasi Uniform or 3D Currents oocccccnncccnncccccnonnnonancncnnnnnnnnoncnnnn cc canon nn resnrrnnennnnenrnrrnesennenrenrnesnnnnnnennn Specifying Regions of Entry and Exit for 3D Current sse eene eene nnne nnne nen Reading and Saving 3D Current Files ssssssssssssssssseeeeeeee eene nennen entrent ne tn tent nenne nnn nnne Simulating MRAM Bias and Write Fields ssssssssssssseseeeneneneen enne en nennen nnns innen nnne nns CHAPTER 15 nputting Data into LLG Layer Boundary Conditions eere Specifying Boundary Conditions A Generating Position dependent Files A SPeCHYVING REROGICIY e Semino a Continuous BC for RETTEN Specifying Shaped Bouridaries 24 ioi pea tete
40. Data Into LLG Layer Properties DEFINING LAYER PROPERTIES 1 Select the Layers option under Structure Properties on the Main Page to enable the Layer Props Page Then click the Layer Props tab Input the number of layers of your entire structure in the N Layers box For the fixed layer thickness method this is the total number of different material layers sub pixels are defined within each layer as needed If you check the Non Uniform box at the bottom left under Layer Type each single pixel width layer will have the thickness that you specify and the number of discretized sub elements in Z will be the total number of layers In this case inside of LLG demag fields in each 2D sheet are computed using Real 2D FFTs and are directly summed in real space in Z For each layer for which you want to define the properties 4 In the Layer edit box indicate the layer for which you want to set the properties IMPORTANT NOTE FOR 1 LAYER POSITION DEPENDENT STRUCTURES If you plan on creating a 1 layer structure with position dependent properties you still MUST define the structure as 1 layer on the Layer Props Page according to the instructions here In this case the layer thickness defined on the Layer Props Page and the total thickness of the structure defined on the Main Page are equal Input the thickness of the indicated layer in the Layer T nm box IMPORTANT NOTE The total thickness of your structure must equal the th
41. FIELDS LLG INPUTHFIELD These files can be loaded and saved through the Boundary Page These are ASCII input files for specifying non uni form external fields HYSTERESIS FIELD PROFILE LLG HYSFIELD These files can be saved through the Hysteresis Page These are ASCII input files that contain a field profile for any hysteresis loop HYSTERESIS FIELD AND MAGNETIZATION LLG HYS These files can be loaded and saved through the Hysteresis Pages These are ASCII output files that record the fields and magnetization at each point in the hysteresis loop MAGNETIZATION MASKS LLG MASK These files can be saved through the LLG Mask Editor and View Page and in the Viewer Control These are binary input files that load or save moments that have been masked turned off MAGNETIC FIELD LLG HFIELD These ASCII files can be saved in the Views Page They are for saving the magnetic field and magnetic induction val ues GRAPHICAL ANIMATION MOVIES LLG MOVIE These binary files can be loaded through the LLG Movie Page accessed on the Tool Bar or the Drop down menu and saved through the Movies Page You can replay saved movies by clicking the Play button on the Tool Bar or by select ing the Replay Movies option under the Drop down Menu These are binary files that save the data for an entire simu lation POSITION DEPENDENT PARAMETERS LLG POSITION These binary files can be saved through the Position Dependent Page These files r
42. Hard Axis Hysteresis Loops in a Platelet This sample problem illustrates the use of the Any direction anisotropy on the switching properties of a thin platelet of hard Ky 10 erg cm3 Permalloy INPUT SHEET MAIN PAGE 1 Initiate an LLG computation 2 Enter the dimensions of the problem X nm is 150 nm Y nm is 150 nm and Z nm is 10 nm 3 Enter the discretization for the problem N is 15 Ny is 15 and N is 1 INPUT SHEET COMPUTATION PAGE 1 Click the Computation tab 2 Set the Convergence limit to 0 001 and the Iterations to 250 INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 Click the Global tab Then click the Material Selector button Select Permalloy from the Materials Page Click Accept the Permalloy properties should be entered in the edit fields of the Globals Page Click the Any button under Easy Axis Enter 1 0 in the Ax and Ay edit fields of the UNIAXIAL section You can enter numbers between 1 0 and 1 0 LLG will normalize them to a unit vector Sa PS N 6 Click Accept Changes to log your changes INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Initialize the magnetization 10 Phi from X in the X Y plane 3 Click Accept Changes to log your changes LLG Micromagnetics Simulator User Manual 39 247 Chapter 39 Sample Problem 14 Easy Hard Axis Hysteresis Loops in a Platelet INPUT SHEET HYSTERESIS PAGE 1 Click the Hysteresis tab 2 Select the Uniform
43. INTEREST Follow the Input Strategy outlined in the chart below Refer to the rest of this chapter for specific instructions for each of the Position Dependent Parameter Pages APPLYING THE PARAMETERS AND THE SELECTED COLOR TO THE AREA OF INTEREST Once you have defined a shape and entered the position dependent parameters for the area of interest right click inside the shape you have drawn and select Fill Region with Parameters Your selected color should appear INPUT STRATEGY FOR POSITION DEPENDENT PARAMETERS mb Define a mask shape with the Drawing Tool see page 148 Select a color for the shape Optional but highly recommended Select Internal or External Fill Mask Region Select Mask Properties Select Uniform or Random Fill eo m RoN If desired Seed Random Number Generator by entering an integer seed and click ing Do It Specify the Layer Fill 8 Specify parameters through the Params Page N 9 Specify the edge Exchange through the Exch Page 10 Specify media properties through the Media Page 11 Specify boundary conditions through the BC Page 12 Right click on the region in the OGL window and select Fill Region with Parameters NOTE Parameters will be cleared To view the color changes check the CO box below in the OGL Props Sheet Modes Page in the Graphic Control Use the Selector Page in the Graphics Control to test individual cells see page 71 On the Graph Page you can also select a reg
44. If any of the boundary condition magnetization components are normal to the boundary surface the magnetostatic stray field from the elements are computed and added to the energy This stray field can be visualized in the Simulation Sheet discussed later in the Manual The boundary condition inputs include DESCRIPTION VARIABLE LIMITS Left X 0 mi 1 0 m 1 0 Right X N m 10 lt m lt 1 0 Front Y 0 mi 1 0 m 1 0 Back Y Ny mi 1 0 mj lt 1 0 Bottom Z 2 0 mi 1 0 m 1 0 Top Z N m 1 0 mj 1 0 The boundary condition direction cosine values can be unnormalized as LLG performs this task internally The values are constrained to 1 0 lt m lt 1 0 LLG Micromagnetics Simulator User Manual 9 85 Chapter 9 Inputting Data Into LLG Boundary Conditions om 0 000 0 000 0 000 0 000 FIGURE 38 Input Data Sheet Boundary Page CREATING POSITION DEPENDENT FILES You can use LLG to generate position dependent magnetostatic fields such as those provided to an AMR sensor head by an external biasing permanent magnet LLG computes the field for any set of boundary conditions where the moments are perpendicular to the boundary therefore you can use the boundary conditions to generate position dependent fields for other calculations Alternatively you can generate formatted position dependent field files and read them in with the Boundary or Layer
45. Image dH dz fir above surface 10 d2H dz2 z nm above surface Z nm Divergence of M C Layer Demag C Integrated B ae Integrated Phase 0 0 Electron Trajectory gt Theta deg Phi deg FIGURE 85 Simulation Sheet Views Page While LLG is running the computation you can visualize different aspects of the problem The View Options encapsu late typical micromagnetic parameters You will probably be most interested in visualizing the direction cosines as they evolve during a simulation However there are instances when visualizing the effective demagnetization or current induced H field can give you important insight into a problem The OGL window can be recursively divided into sub windows for viewing different aspects of the same problem If you RIGHT CLICK on the main window you have the options to split the window horizontally resulting in two windows one above the other split the window vertically resulting in two windows side by side or delete the active window You cannot delete the last window as LLG requires that there be at least one active OGL window You can continue to split the windows and make the nesting as deep as you choose VIEWING POSITION DEPENDENT PARAMETERS Refer to page 150 for information on this feature LLG Micromagnetics Simulator User Manual 23 167 Chapter 23 Simulation You can put any view option into any view window For demonstration the
46. Install Cool Tools menu selection LLG uses a numerical filter to guarantee that edit fields are input as numbers If you rapidly enter a multidigit number LLG will only take the first digit You can now toggle the numerical filtering tool on off Some users consider this feature to be a bug However it prevents LLG from having to error trap every data entry to check type If you opt to turn the numerical filter off you will be responsible for insuring that the data as entered are numbers rather than arbitrary character strings 5 72 LLG Micromagnetics Simulator User Manual CHAPTER 6 Inputting Data into LLG Main INPUT SEQUENCE Once you have initiated a simulation by clicking the New Domain button the Input Data Sheet appears This sheet and its pages are where you specify the data during the Input Phase This section of the Manual outlines each page and its options which are best completed in the order in which they are presented The general strategy is to enter parameters in the following order 1 global 2 boundary conditions 3 computational 4 initialization 5 static and pinning fields 6 notes 7 hysteresis loops time dependent fields or shielded media fields 8 layer 9 layer bound ary conditions 10 position dependent 11 and currents If you use 2D currents only you might specify them after entering the static and pinning fields The strategy below indicates how LLG actually manipulates data internal
47. Journal t ee eek hadi nan UOS EC e to DL v RE Pet PEEL ED ell Meee 36 Specifying File Thy or Em 37 Searching Disks or Directories iwi ua Oe Alle Ba ii at a A ees 37 Summary of Input and Output File Formats Of vi 38 Summary of Input and Output File Formats of vi 42 LLG Micromagnetics Simulator User Manual iii Table of Contents CHAPTER S LEG ERVIFODIDODE arar minen as ediod A PM RERO 53 Startup Screen sedes uten be LL I nC De REO LCS o ddr Lec E Le dus 53 Main Window Tool Bar iter etteccosteme ee iret tre t eco viget pes tdi 54 Graphics Storico 58 OGL Prop Sheet SER Ioa E 59 OGL Prop Sheet Modes Page nennen nenne nitens en nnns enn tenis nnns sitet seen nn sentent nns nnns rennes 59 OGL Prop Sheet Orient Page EE 62 OGL Prop Sheet OGL Page ET 63 OGLE Prop Sheet Color Page ion ede dieere E 64 OGL Color SMCS SSN 65 OGL Golor Sheet Golor P ge tie tette p tee Pn te een 65 OGL Color Sheet Wheel Paoe conocen 66 OGL Nat Tal EE EE 68 OGL Information Sheet Info Page ener een resins inn rene nnn nennen inns nnns rennes 68 OGL Information Sheet Disks Page ceret ra iet rr cete e per Eie E Y ed ads 68 OGL Information Sheet Output Page 69 OGL Information Sheet Clock Page E 69 OGL Information Sheet Calculator Page eene nnne teneris sn tnr en nnns nnn nens 70 OGL Information Sheet Demag Field Calculator ssssssssssesssseseeee entente nnne nnns 70 ELE ere TEE 70 OGLE Selector She
48. Load your movie and position the view how you want to display the scene The avi movie contains no data The avi file is composed of compressed bitmap images in a video stream riff file Once you are ready to create the avi file click the Save AVI button You will be prompted to save a compressed movie Microsoft Video compression at a quality fac tor of 5096 is recommended One bitmap image at normal display size occupies 1 7MB of memory and a movie with 41 frames requires over 68MB of disk space Click the OK button to proceed You will be prompted to select the compres sion method and compression quality LLG Micromagnetics Simulator User Manual 25 195 Chapter 25 Viewing Movies Movie Hysteresis Edit Movie n LLG Movie Player SA Playback Of Recorded Calculations vx File Options Load Movie Save AV Save Dom Version 2 Nx B4 Check M AAA Frames 61 Ny 32 Status Good Nz H SpitMovie Manually Split Player Controls A Play Pause Rewind d h Speed 0 5 Sec Frame Progress 1 Frame Time ps lt Dutput File Name Examplel_TMA NEI roOhE vample TMP Io movie Set View Hys Loop Set View MR Loop fe Ang Polar e dR dR R Close Movie Masks FIGURE 119 Movie Player Sheet Movie Player Page 25 196 LLG Micromagnetics Simulator User Manual Chapter 25 Viewing Movies MoviE VIEWING OPTIONS e You can choose several view
49. Magnetization Direction Cosines Standard View Option is shown in several graphical representations Other View Options are shown in one graphical represen tation All View Options and graphics are drawn from the initial stage of the iteration process of the same sample prob lem the parameters are Simulation Volume 500 nm for X nm 500 nm for Y nm and 30 nm for Z nm 50 sub elements for N 50 for N and 3 for N Material Properties Permalloy Boundary Conditions Left M 1 0 Right M 1 0 and X directed current of 1000 uA Computational Details Relax All Points at Once FFTs Initialization Vortex in Z Click the Magnitude button to plot the magnitude of any vector quantity The data are stored in a temporary array and there is only one temporary array for each LLG object This means that when you save data to a file from a Computed View a Computed Imaging Mode View or a Magnitude View the data in the last LLG subwindow will be active To ensure that you save the correct data to file it is recommended that you use only one of these three views at a time STANDARD VIEW OPTIONS MAGNETIZATION DIRECTION COSINES With the Magnetization Direction Cosines Standard View Option you can visualize the vector field whose projections are the normalized magnetization vectors along the three Cartesian axes r Standard View Options Residuals Change lteration Effective Field Magnitude Demag Field Energy Density aveToFile
50. OF FIGURES PU XIII CHAPTER1 License Agreement and Release Notes muasnssnnsunnnnnnnennnnnnnnnnnnnnnnnnnnnnnnnnennnnennnnnnnen 17 License Agreement si feces eue tea aet duis atta aided eet eso a aee ea i aeree ets 17 Release Notes sett ele e eet Urt eee tt eee cele tee tec d te pir vtro er pec te e t a ET M 19 CHAPTER 2 GefingSaned o E t 21 System Requirements TEE 21 Memory Requirements of LLG Calculations eese eene nnne nnnnennrenennnnnnennernnnnesnnnnnennnn 22 Installing LLG Micromagnetics Simulator sse ener rennes rra 22 Installing the Protection Key i reete t tet baee e egt rubet b nae cere pu bra eai inca re A Rage n 22 Installing the Protection Key RE 22 Installing LLG with Windows 2000 or Win vi 23 Installing LLG in Kanji and Hangul Environments ssessssssseseseeeeseneenee enne nnne nri nemen nnn nnns nens 23 CHAPTER3 Introduction 10 USING LEG eiii iii iria 25 Thr e Modul siof Funetienality ua ane doe E tk Dee iate tn 25 Input Phase Data Specification sssssssssssssssssessse eene rant nennt nnn sintene rh nns en annann Eense nnne sens 25 Simulation Phase Solution of the Differential Equations oooooccccnnnnccnncccnnnocccnnnrnnnnnann conan eene 25 Review Phase Playback of Results through a Graphically Animated Movie 26 Theory of Operation eene iet e etit taba diente tepidis dts 26 CHAPTER4 Loading and Saving FICS sessisisissssdeecsesssscaseseseensssvszsde
51. OGL window frame at bottom right For the rectangle circle and ellipse left click with the mouse to choose the starting position and continue to hold down the mouse Dragging the mouse outlines the shape under construction Release the mouse button at the final point to mark out the shape NOTE For the polygon you must left click for each point that you wish to define and double click to close the polygon The arbitrary line allows you to draw a wavy line and enclose any shape that you choose to define e Click the CLR button to clear all defined shapes SELECTING A COLOR FOR THE AREA OF INTEREST You can use color coding to distinguish the region of position dependent parameters and as an indication that your input takes effect 1 Click the Params tab Select a color from the drop down color box which is at the bottom just to the left of the Clear button Check the box beside the drop down color box to indicate that you want the selected color to take effect Click the OGL Props tab in the Graphic Control at the bottom then click the Modes tab Then you MUST check the CO color box for your color selection to appear in the OGL screen The CO box is enabled during the Input Phase of LLG only when position dependent files are being defined 22 148 LLG Micromagnetics Simulator User Manual Chapter 22 Inputting Data Into LLG Position Dependent Parameters INPUTTING POSITION DEPENDENT PARAMETERS FOR THE AREA OF
52. Page Position Dependent Parameters Sheet Simple Tiling Example Position Dependent Parameters Sheet Bitmap Page Position Dependent Parameters Sheet Edge Page Edge Fields and Torques Computed Hysteresis Loops with and without Edge Correction Position Dependent Parameters Sheet Boundary Conditions Page Simulation Sheet Simulation Page Simulation Sheet Views Page Standard View Options Magnetization Direction Cosine Magnetization Direction Cosine 3D Cone Magnetization Direction Cosine Arrow Slice Magnetization Direction Cosine Domain Magnetization Direction Cosine 3D Arrows 101 xiv LLG Micromagnetics Simulator User Manual List of Flgures FIGURE 92 Magnetization Direction Cosine Contour and Bitmap 170 FIGURE 93 Optional View Options 172 FIGURE 94 Current Induced Field Arrows 172 FIGURE 95 Polar Loops X esd ccs nieee eee e cde ove atas em h let A aede anette SO tata coa 173 FIGURE 96 Polar Loops Represented in Polar and Angular Formats lille 173 FIGURE 97 Computed View Options 174 FIGURE 98 Energy Density and Effective Field Bitmaps 174 FIGURE 99 Boundary Conditions Arrow Slice lille 175 FIGURE 100 Change lteration and Demagnetization Field Contours o o ccccocccccc 175 FIGURE 101 Computed Imaging Mode View Options 176 FIGURE 102 Computed Imaging Mode Fields Arrow Slice 6 tenes 177 FIGURE 103 Computed Imaging Mode Fields and Divergence of M Bi
53. Sheet Hys U Page allows you to specify the field path along which to compute the hysteresis loop The strength and orientation are specified by the three Cartesian field components There are four principal methods for specifying the hysteresis field All field profiles can be viewed in the OpenGL window either in 2D Field View or 3D Field View with or without interpolating lines toggle With Lines The LLG Input Sheet Hys U Page allows you to specify loops with a uniform sampling of the magnetic field This makes data entry easier Internal to LLG there is no difference between uniform or non uniform or rotational hysteresis loops because LLG computes the field sequence and saves it in an internal array To enter the field you must specify the maximum field LLG will start the loop at the positive maximum field move to a negative maximum field and then return to the positive maximum field and the number of field points along a single branch The negative maximum field point is sampled only once which means that specifying 11 points to scan the field results in 21 total field points Data are summarized in the table below and the Input Sheet Hys U Page is shown on the following page You can select either a uniform hysteresis loop Hys U Page a non uniform hysteresis loop Hys NU Page a time dependent h field Time Dep H Page or a moving media problem Shields Page These are mutually exclusive only one mode can be used for a given problem
54. animated sequence that is termed a movie You can adjust how the movie is rendered at any time with the Graphics Sheet at the bottom left of the screen Refer to the Chapter 5 LLG Environment for details on graphics LLG Movie PLAYER SHEET MOVIE PAGE Click the Movie Viewer icon in the tool bar at the top of the screen to activate the Movie Player LOADING AND SAVING OPTIONS Click the Load Movie button to load a movie from a file You will be prompted for the llg param file that was used to create the movie The LLG v2 Movie Viewer will read and display LLG v1 and v2 movies Click the SaveDom button to save an ASCII llg dom file You can access your binary data that is stored in a movie file and save any frame to an ASCII file This file can be used to seed an initial condition for another LLG simulation or as input to a program that you might write to process interpret or present data based on magnetization cosines The file format is given in Chapter 4 Loading Saving Files AVI Files With LLG you can create and save a Windows video stream movie avi file from your LLG movie These standard Windows avi files can be viewed by any standard windows video viewing utility LLG is distributed with a simple utility named LLGAviMoviePlayer exe You can distribute this movie viewing utility free to your colleagues with the movies This allows you to circulate your results through avi files with those who do not have LLG Micromagnetics Simulator
55. clicking the LOAD SECTION button Enter 4 into the Field Section Specified edit box Enter 300 0 in the Limit 2 edit field for Hx Enter 10 in the Num ber Of Field Points edit box Load the field section by clicking the LOAD SECTION button Enter 5 into the Field Section Specified edit box Enter 450 0 in the Limit 2 edit field for Hx Enter 15 in the Num ber Of Field Points edit box Load the field section by clicking the LOAD SECTION button Enter 6 into the Field Section Specified edit box Enter 750 0 in the Limit 2 edit field for Hx Enter 6 in the Number Of Field Points edit box Load the field section by clicking the LOAD SECTION button The field view on the screen will appear in 2 D as shown below FIGURE 128 Non uniform Hysteresis Loop 2D View for a System with a Coercive Field near 375 Oe To save the specified field to an ASCII file click the Save Input File button You will prompted for a file name To use this field profile for another problem use the Read Input File button to read the file It will automatically be loaded into the Non Uniform Sampling Hysteresis Loop section for use in the LLG simple field editor and for visualization Choose Accept Changes to complete the hysteresis specification No other modifications to the default settings are required to run this problem Click the Begin Simulation button If you have not saved the new input parameters LLG will prompt you to do so Respond as in
56. color box at the bottom of the page FIGURE 20 OGL Color Sheet Color Page LLG Micromagnetics Simulator User Manual 5 65 Chapter 5 LLG Environment OGL CoLoR SHEET WHEEL PAGE The OGL Color Sheet Wheel Page is where you can alter and set the OpenGL color wheel properties directly Color wheels are used to display Domain Graph Type The principle is to select colors over in plane angular ranges that are indicative of domain orientations To provide the flexibility to capture this functionality the Color Wheel can be decom posed into as many as six regions that is six fold symmetry or anisotropy where each range of angles can be speci fied independently The Color Wheel allows you to select separately the number of active regions Angle 1 through Angle 5 check boxes the angle to start end that region center and the color to interpolate to at that angle The colors are selected by click ing the appropriate color box Color 1 through Color 5 1 Check an Angle box 1 Click a Color box which redirects you to the OGL Color Sheet Color Page just described 2 Select a color from the Color Page 3 Click the Wheel tab to return to the Color Wheel Page The selected color is automatically loaded into the Color box for the selected angle The Color Wheel itself at bottom left can be rotated with the slider the thumb wheel or the edit box Once you find y
57. conv file for output e Specify Output File Names Movie Specify llg movie file for output e Specify Output File Names Save Conv Details Save detail to the convergence file selector Specify Output File Names Every N Iterations Save conv detail every n iterations specifier e Specify Output File Names Save Movie Save movie file selector SAVING CONVERGENCE DATA To save the transient energies and magnetizations to file check the Save Conv Details box which enables the Every N Iterations edit field Then enter into the edit field how often you want the data saved to file For example if you enter 1 LLG writes the energies at every iteration if you enter 10 LLG writes to the file every 10 iterations You can use the 2D Graphics tool see page 55 to view these files interactively as they are written GREEN S FUNCTION LLG is a full two and three dimensional micromagnetics calculator The difference between these two computation engines is in the structure of the Free Space Green s Function for the computation of the magnetostatic self fields Most simulations will employ the 3D Green s Function However you should select the 2D Green s Function for simu lating domain walls that have 2D symmetry Several options are specific to the 2D calculation engine including the interface discretization schemes The Green s Function for the problem CANNOT be changed once a simulation has begun IMPORTANT NOTE All 2D Green s Function pro
58. dp dg kleed deed de deeg SSE ttt A FEE OE EE 7 ot tp te tt d hb 7b 7b 7b A 4 4 4 4 4 pp Dp A 4 4 4 4 4 4 ko e ok ol ge T D ge P a t 4 4 4 4 4 che Dp ll 4 4 4 aie he ie Db A aie aie b D TR Er SE IE EEE EES de de de de dg AAA tp cb D Db cb ADA E EE bat alt lt lt lt ale 4 4 4 4 dd 4 Tp Tp Tp Tp lt 4 4 4 4 gege gt gt on 4 d d d 4 d RE de de de de de bg b 7b 7b 7b b gt A 4 EEE EE PPP PP PPE EEE EEE PPP PPD DEE EEE EEDA Th TR RR Rb pp gt 4 4 4 4 4 gt d deng EEE EEE de de le le gt gt gt b 7b 7b gt gt gt 4 EEE EE PAPA PP PE EEE EEE PPP cb PD PE EEE AA DP rh hb ef jr bb Y de de de e e de Pob SS dodo j de da sje sjef SSS SE dede do ob op op of mf fr e PP PPP PPE A 4 4 4 4 4 PP PPP PPE EEE EEE 7b 7b PPD PE 4 DDP PP Jtt 4 4 47 EE 4 4 4 4 4 5 hh tettetett PP b dg dg dg 4 4 4 4 4 4 PPP AID REE EE EEE PPP cb cb b dg PPP dt b tp pp gt gt gt gt 4 4 4 pp 4 EEE 4 4 4 pp pp dt dt dg PPPPP PREECE EEE FPF D Dp D FEE EEE 47 47 7b 7b cb b cb EE EE EEE P EE ob P EE Robb Db Db Cb Db 4 EEE EEE FFF Dp Dp Dp FEE EE EEE FAFA APRA PEE 4 4 4 4 4 ob EE EE EE gt gt gt PPE EE EEE Db pp Db FEE EEE EE FARA E E 4 4 EEE EE AIP P EE PPP bob cb DP EE EE EEE FFF Dp Dp Dp FEE EEE EE FPA EE E 4 4 4 EEE PHP P P EE gt gt gt gt DD gt 4 47 4 4 4 4 pp pp b cb Dp G dr dd EE EE E E
59. eere 85 ACA uutuus Ennan EnASE ESANEAN ASEAS SEESE EEEE Ennn Ennan rannen anna 86 Biasing a Structure with an External Field 87 iv LLG Micromagnetics Simulator User Manual Table of Contents Speetfying Perlodicity cito ee ea eee ram ide en Pen ea eco ect dere deett 87 Specifying Continuous BC for 21 87 Specifying Shaped Boundaries rrrrnrrnnonrvnnnnnrnnnrnrnnnnnrnnnrnnennnnnrnnnnnnennnnnnennnnensnnn rane eterne nni sen terr inns i nent rents nnne nn 87 EDCH KSO Per 3D Complex o eie A A heste eder iate e e dedo ee e eo eode eve eee dd 87 CHAPTER 10 nputting Data into LLG Computation eersuunnevnnnnnnvnnnnnnnnnnnnnnnnnernnnennnnnnnnnnnnannvnennnnn 89 Relaxation E ne Le DE 90 Energy SOR s dan ak EE dt tte iaa 91 Energy Search Sequential or Random renannvvnnnnrnnnnnnvnnrnrrrvnnnrnnnerrrennnnrnnnenrennnnrnenenrenennrnnssnnenennrnessrnenennressnnnnnsennee 91 O E 91 Time Integration ete tet toe e fece eins edes fe dede ene ended ee Ue de ex e eda ewe a il 92 FET Method PEE 92 PS Time Step MAX iii dece e ee acne Mine e Let Hp La e eee eee nee 92 Use Dual Processors idee naken 92 Computation Parameters careret a e yet a a pet i Ee ag ae 93 CONVE EE 93 iterations tru 93 keratone d dadaismen 93 Recommendations for Selecting Convergence nennen nennen nnne nnns inns 93 Energy Up Energy Criteria arenrnnrnnnnnvnenonrvnnnnrnnnnnnennnnrnnnnnnnennnrnnnnn
60. element layer Z 1 Permalloy 10 HHmax 1 0 1 0 rs FIGURE 137 Hysteresis Loop from Unpinned Problem and 250 Oe Field Pinning 36 238 LLG Micromagnetics Simulator User Manual CHAPTER 37 Sample Problem 12 Shaping Magnetic Elements This problem illustrates the use of the Mask Editor for shaping the magnetic simulation volume Holes can be cut into a structure arbitrarily in three dimensions Corners can be cut off and roughness can be added along edges or at inter faces The Mask Editor was designed for flexibility in creating realistic and non Cartesian structures With the Mask Editor you can remove cells sets the magnetization on or off IMPORTANT NOTE Any curved surface constructed with LLG is digital i e jagged To date the presence of jagged edges has not had any deleterious effects on the outcome of the problem as long as the sub element size is appropri ately small so that the magnetic stray field can easily couple across the vacuum interface In a real structure with curved boundaries there would be some magnetic material INPUT SHEET MAIN PAGE 1 Enter the dimensions of the problem X nm is 750 nm Y nm is 500 nm and Z nm is 10 nm 2 Enter the discretization for the problem N is 75 Ny is 50 and N is 1 INPUT SHEET COMPUTATION PAGE 1 Set the Convergence limit to 0 0001 and the Iterations to 2500 2 Set the Time Step to 2 0 ps 3 Click Accept Changes INPUT SHEET MA
61. for variation You can select at most five parameters to vary Once you have selected the parameters click the Generate Files button For each parameter that you select you will be prompted by LLG to enter parameters as shown below Scripter Range Yector Variables Scripter Range Scalar Variables 0 0000 0 Boundary Condition Left rns mu mz D Layer Magnetization emu cm 3 r Range Option T List Option Range Option Range fe List Minimum 880 Variable 1 Maximum us Minimum 0 Variable 1 i Increments 3 Fi Range Maximum 1 0 Random Selector Option Minimum 880 i 720 Variable 2 Maam ee 1 SSS Increments 3 Minimum 0 Variable 2 x Standard Dev 80 Maximum 1 0 AM Random DIS dry 4 D r List Option gt List Options Y Variable 3 e 567 Minimum 0 Variable a 589 Maximum 1 0 0 List Variable 4 Minimum 0 Variable 4 Gi pe List Option MEI X File List Options 173 C File list Add Multiple Files Increments 3 n S n dei p FIGURE 116 Scripting Range Vector and Scalar Menus LLG Micromagnetics Simulator User Manual 23 191 Chapter 23 Simulation For single data values each data entry prompt allows you to specify 1 Range 2 A Random Selector 3 Alist of values or 4 A file should you wish to loop on this as a variable LLG asks for the minimum maximum and increment number f
62. from an lig hyspart file is shown below for a single Fe moment relaxing in a 5kOe field FIGURE 117 Dynamical Data View LLG Micromagnetics Simulator User Manual 24 193 Chapter 24 Viewing Files The viewing option is useful for analyzing files that you might use as initial conditions or use to interpolate onto a new grid de LLG File Viewer XK t Simple File Viewer To Check Files AN Load File File Name File Type Magnetization Components Basic Imaging e Direction Cosines Angles mi H iren above surface 10 Compute dH dz z nm above surface Z nm Ms 800 d2H dz2 z nm above surface assumed Divergence of M Difference of Dom Files 1 2 m 2 m 1 r File Type Binary Mask Files C Magnetization or Hysteresis Mask r File Type 3 D Vector Fields C 3 D Vector Fields Demag Current BC I Flow m File Type 3D View Of Position Integrated Magnetization Hysteresis Part Dynamic Mag Hysteresis Part 1 Hysteresis Part 2 Hysteresis Part 3 FIGURE 118 LLG File Viewer 24 194 LLG Micromagnetics Simulator User Manual CHAPTER 25 Viewing Movies vis tiie III p s VILLET dr Once a simulation is complete you can review the results through the Movie Sheet Just load a movie file and play it LLG s movies are not just graphics files they contain all of the data stored in binary format LLG renders the data in the form of an
63. gt gt gt gt gt NMN nom 0 lt a lt a E Kk amp amp amp eee Kk amp X7 X S KLE e e ene M E e NS ou A ee E ES M E e e SE LEK d e kl e a mn SS EK Aer ux KEE KKH KKK E NNM a 7 A NwWo amp 9 m7 NN DB cA c7 NN DADC 77 NM gt gt gt 77 A Nm gt gt gt gt PITT BAD BPH gt 3 27 Magnetization Pattern in Layer 1 Near Zero Field in Arrows top and Magnetization Pattern in Layer 2 Near Field in Arrows bottom 33 228 LLG Micromagnetics Simulator User Manual CHAPTER 34 Sample Problem 9 GMR for bilinear Interlayer Exchange between Platelets This is the third sample problem with multiple material layers It has two layers of Permalloy that are separated by a non magnetic Cu layer The two layers are antiferromagnetically coupled through a GMR type exchange at the inter faces of the two magnetically active layers across the Cu interlayer In addition current is flowing along the X axis and a GMR ratio of 0 25 has been attributed to the magnetoconductance of the active layers Fields from the driving cur rents are included in the simulation Both the hysteresis and MR loops can be visualized during the computation INPUT SHEET MAIN PAGE d 2 3 4 Initiate an LLG computation Enter the dimensions of the problem X nm is 250 nm Y nm is 100 nm and Z nm is 30 nm Enter the discretization for the problem
64. if you want your inputs to update the LLG parameters used in the calculation ANALYZING THE K 0 FOURIER COMPONENT IN PERIODIC 3D COMPLEX BC COMPUTIONS The k 0 components of the field are evaluated on the Fields Page during the simulation process if this option has been selected on the Boundary Condition Page LLG Micromagnetics Simulator User Manual 12 103 Chapter 12 Inputting Data Into LLG Fields Af Huel S HysNU Ht gt FMR v Shields Main Globals Materials Boundary Computation Initialize Fields Current Layer Props Layer BCs Notes Batch v5 P r External Uniform Applied Field Hx Oe Hia UOCE Ga 0 0000 10000 10000 Hy De SR EE 0 0000 10000 10000 Hz De SE 0 0000 10000 10000 r Pinning i e Exchange Bias Field Hx De INIA OL NET 0 0000 10000 10000 Hy Oe UOR S E 06090 1708476 878087070 80011 0 0000 10000 ML ES aa Hz Oe EE KO TUN 0 0000 10000 10000 LoadH Pin gt Layer to Pin 1 Optionally Remove Effective Field Components Check ONLY To Remove Demag Exch Anis H k 0 Periodic Field Correction Status 3D Complex FFT Hx Oe Hy Oe Ae Change Hz De Accept Changes JC Reject Changes FIGURE 47 Input Data Sheet Fields Page The pinning fields are entered in Oe as specified below DESCRIPTION VARIABLE LIMITS External Applied Field Hex 106 H 106 Pinning Field Hin 108
65. in Fe 243 Input Sheet Main P g aa o tette ttt Lei etii da 243 Input Sheet Computation Page nennen tentent iren tenet ndn ns steterit nensis snnt einn san nr neret 243 Input Sheet Globals Page and Materials Page oooccoccccnnocccccncccconnnnnanoconononcnano cnn nn cana nn nc nn nr n anar nn nannn cnc 243 Input Sheet Boundary Conditions Page 243 Input Sheets Initialize Page iot ctt eren Die eh iate tte it eat a ber erect eta 244 efonsuci cM Er EE 244 SE 244 CHAPTER 39 Sample Problem 14 Easy Hard Axis Hysteresis Loops in a Platelet 247 put Sheet MaN Page eed eee fet ates Pelei edi ra T e teet Pa 247 Input Sheet Computation Page 247 Input Sheet Globals Page and Materials Page eene nnne nnne 247 Input Sheet Le EEN 247 Input Sheet Hysteresis Page eec inte in eei cial dae te xd dla 248 Rerunstlie Problem neo a RERO tutte e ee ees 248 el EE 248 SIE 248 CHAPTER 40 Sample Problem 15 Magnetization Dynamics in Permalloy Platelets 249 Input Sheet Man Page EE 249 Input Sheet Computation Page eire tete i eee ed te t de A rep I Kee dad 249 Input Sheet Globals Page and Materials Page ener nnne nene nnn nnne nen 249 Input Sheet Initialize Page oin oper ED he EE epi ee Ee atate E ed beta hd teresa 250 Input Sheet Time Dep H Page nennen enn ten sinn nns etn tes nn eran nnne nen 250 lu 250 mca uL 250 CHAPTER 41 Sample Problem 16 So
66. lies in the Z constant X Y plane Enter the plane distance from the TOP of the structure in the edit box adjacent to the MFM mode selection H z nm above surface dH dz z nm above surface d2H dz2 z nm above surface and Divergence of M The MFM contrast for each mode will be computed for the plane of interest and dis plays Electron microscopists might want to compute the Integrated B field TEM Lorentz or Integrated Phase DPC or electron holography The angle of the incident beam must be specified in the Theta deg and Phi deg edit fields where the angles are defined using the spherical coordinate convention defined in Chapter 5 LLG Environment You can also visualize demagnetization fields from independent layers To do so you must first create masks for the appropriate layers that you want to mask or any portion thereof Only the unmasked portion of the mask will be used in the demagnetization field computation When you press Do Image LLG will prompt you for the input mask to read LLG will then compute the demag field from only those cells that are unmasked This will allow you to identify the posi tion dependent dipolar coupling between layers for MRAM and similar applications IMPORTANT NOTE H z dH z dz and d H z dz Integrated B and Integrated Phase images take time to compute The Do Image button has been strategically placed for you to indicate to LLG that you want an image to be computed The computed images store da
67. m pAY m nSize sizeof t Double m fileMovie Write m pLLG gt m pAZ m nSize sizeof t Double return TRUE t BOOL CDatalO CloseMovieFile m fileMovie Seek 64 3 sizeof t Int CFile begin m_fileMovie Write amp m_pLLG gt m_nHysHcount sizeof t_Int m_fileMovie Close return TRUE LLG Micromagnetics Simulator User Manual 4 51 CHAPTER 5 LLG ENVIRONMENT START UP SCREEN When the program is first loading the copyright notice is displayed against an image of the magnetization in a thin film media with random anisotropy The domain image is color coded to indicate the directions of the magnetization in the domains This Windows environment contains features that remain constant throughout the operation of the program The dark area is an OpenGL window which is the viewing screen for all simulation graphical output It displays all graphical data as you select them through the LLG Input Sheet and LLG Simulation Sheet Pages for example you can display the direction cosines and fields while a simulation is running This is also the window where movies from previous simula tions are displayed The gray areas to the left are the I O pages In this chapter the functionality of the main window including graphics is demonstrated Dividing the Graphics Window The OGL window can be recursively divided into sub windows for viewing different aspects of the same problem RIGHT CLICK on the main window for the followi
68. magnetization on the whole cube 3 Click the Start To Compute button which initiates LLG to relax the magnetization The meter tracks the simulation s progress as a percentage of the maximum number of iterations and updates the iteration count The in plane flux vortex will degenerate so that the magnetization points perpendicular to the plane of the vortex in the core in about 200 iterations LLG will stop the calculation once the convergence limit 0 0001 in this case has been reached SIMULATION SHEET VIEWS PAGE Experiment with visualizing different parts of your structure 1 Click the Orient tab then click the Z Slice button 2 Click the Modes tab then select Bitmap Graph Type In the middle bitmap pane the vortex is visualized as the central core in the Z component of the magnetization 3 To examine the bitmap use the Orient Slice slide bar at the bottom left of the screen to scroll through the slices The helicity in the flux closure pattern can be seen as an asymmetry in the magnetization pattern 4 Select the Modes Contour Graph Type then scroll through the slices again Then examine the components of the effective field Select 3 D Arrows to see the surface fields on the whole cube and select the Effective Field from the Simulation Sheet Views Page Notice that the magnetization is indeed along the effective field direction 5 Click the Selector tab Then click on any arrow in the OpenGL window The values of the magn
69. mask characteristics to the area through the Position Dependent Parameters Sheet Main Page SPECIFYING FiLL MASK REGION You can Fill Mask Region Internally or Externally which changes the cell types either inside or outside of the shape SPECIFYING MASK PROPERTIES AND RANDOM FILL You can set the Mask Properties with the following options e You can select Set Params which is the default and applies the specified parameters to the defined region e You can Turn Cells On or Turn Cells Off completely within the defined region e Additionally you can apply the specified properties either uniformly or randomly to the defined region by selecting Uniform Fill or Random Fill A univariate random number generator is used to Turn Cells Off or Turn Cells On as a function of location with a probability that a Fraction of those cells will be on or off You must enter a number between 0 and 1 into the Frac tion edit field For example 0 5 the default means that it is equally probable that the cells will be turned on or off If you enter 0 75 into the Fraction edit field then on average 3 4 of the cells will be turned off or on If you want to be able to repeat a Random Fill in the future use the Seed the Random Number Generator fea ture For example enter an integer permutation of the date and time into the edit field and use that same integer the next time in a different region or in a different simulation the properties will be applied in the SAM
70. minimum and maximum values and coded as above The number of contours can be set in the OGL Props Sheet OGL Page e 3D This feature allows you to warp the Bitmap and Contour configurations in 3D You can adjust the vertical scale gain on the 3D warping with the slide bar adjacent to the 3D check box The normal 3D angular and position adjustments can be used to center and rotate the view LLG Micromagnetics Simulator User Manual 5 59 Chapter 5 LLG Environment 3D Slice You can display the data in either two or three dimensions The two dimensional view shows a slice in the selected orientation X Y or Z An X slice is a cut along an X constant plane with the Slice slide bar or edit box OGL Props Sheet Orient Page you can define the integer constant of the plane s sub element discretization index for the selected orientation Therefore a structure that is defined to be X 21000 nm N 100 Y 30nm Ny 3 Z 500nm N 50 has 100 X slices that display 30 nm x 500 nm Y Z planes three Y slices that display 1000 nm x 500 nm X Z planes and 50 Z slices that display 1000 nm x 30 nm X Y planes 3D Surface This feature is for three dimensional vector data only when the surface of the volume is displayed This view is useful for analyzing three dimensional structures such as cubes with vortices Domain With this feature the in plane components of a vector are projected with a fixed color wheel Regions of constant magneti
71. nm Permalloy Platelet Initialized with Totally Random Magnetization dp dd dt dm 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 ee gt gt gt gt gt gt gt gt gt gt gt gt pp op op op op op gt op op op op op op op op o o o gt gt gt gt gt gt gt gt gt gt gt gt gt gt EE op op op op op op op op op op op op op op o op op o gt gt gt gt gt gt gt gt gt RT gt gt gt pp op op op op op gt op op pp op p pp 4 47 4 4 4 47 47 4 47 47 4 47 47 47 47 47 47 47 47 47 47 47 47 47 47 47 4747 44 fm fm tm jm jm fm tt dn gt gt gt gt gt gt HHH gt od gt pp gt op op op op op op op op op op EE E EE EE E MC 4 4 4 4 4 4 4 4 4 4 6 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 tt ti e py e 47 47 47 4 e e e 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 Ee y y y y y y y y y y y y y gt gt IG gt EE gt pp op gt pp e e e e e e e e e e e b RR RR FIGURE 46 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Vortex Random Magnetization Please remember to click the Accept Changes button if you want your inputs to update the LLG parameters used in the calculation CHAPTER 12 Inputting Data
72. number of cells in a periodic direction MUST be a power of two Periodic along X Since the structure has wrap around symmetry along X the magnetostatic fields are periodic along X Periodic along Y and Z The structure has wrap around symmetry along both Y and Z SETTING A CONTINUOUS BC FOR 2D A continuous boundary condition can be set in Y for a 2D simulation which removes the boundary along the bottom side Y min allowing a semi finite terminated solid to be simulated At present the 2D Continuous feature is not active in v2 of LLG SPECIFYING SHAPED BOUNDARIES Refer to page 119 for instructions on this feature Remember to click the Accept Parameters button if you want to keep your inputs LLG Micromagnetics Simulator User Manual 15 119 CHAPTER 16 Inputting Data into LLG Notes LLG provides you with a very simple way to enter comments about your problem In addition to the problem title on the Input Sheet Main Page you have 10 additional ASCII fields for entering data in the Input Sheet Notes Page shown on the following page By default the date and time that the problem was loaded appear in the first field LLG Micromagnetics Simulator User Manual 16 121 Chapter 16 Inputting Data Into LLG Notes FIGURE 53 Input Data Sheet Notes Page 16 122 LLG Micromagnetics Simulator User Manual CHAPTER 17 Inputting Data into LLG Uniform Hysteresis Loop The LLG Input
73. of 95 color applying to position dependent parameters 148 setting for display 22 using with position dependent or layered structures 60 color map file type 33 color properties setting 64 67 color table using to display bitmap and contour modes 67 commit size 74 accessing mask editor with 139 computation page 181 computation parameters 93 95 alpha 94 convergence 93 energy up 94 gamma 94 iterations max 93 iterations min 93 limits of 89 number RHS 94 random number RN seed 94 starting and stopping times 94 temperature 94 updating during a calculation 181 computation time decreasing 95 185 decreasing with pinning layer antiferromagnet 237 cones examples of 169 contours example of 170 graph type 59 using color table to display 67 warping 59 converge problem fails to 184 convergence 93 recommendation for setting 93 convergence criteria exiting a calculation by satisfying 95 symptoms of setting too coarse 184 convergence data file type 32 saving 76 convergence file examining contents of 55 coupling tensors v1 input and output file format of 39 coupling interlayer 115 CPU time 165 current parameter limits of 105 sample problem with 3D 263 saving and loading sequences 107 specifying input and output regions of 109 types of 107 109 v2 input and output file format of 45 current induced field visualizing 172 current mask v2 input and output file format of 49 D d2H dz2 z nm example of 178 view option
74. parameters to a file you can reload them and edit them using the tools pro vided in LLG or using a standard file editor Remember your comma separated values are NOT SAVED to this file Additionally no LLG file tag is associated with this file type In the data provided these files have MO Parameters as a suffix ViEWING MO DATA USING MO GRAPHICS You may visualize your MO data using the MO T Graphs Page In the edit fields at left enter the nominal values for M4 Mo M A K If you are computing a 2 spin system LLG will form M from M4 and M Since LLG uses the functions and input data only for scaling i e position dependent M4 Ms M A and K are each scaled by these functions with their own position dependent T Just click on the appropriate parameter and it will be displayed in the graphics window at the top of the page as shown in the figure below Once you have either entered a file name for the temperature data or you have defined an appropriate function you can click the Preview Temperature File button to see a movie of your temperature data as specified and projected onto the LLG grid COMMENTS Nucleation local to the rim of the Curie disk depends quite sensitively on the parameters specified there The code will nucleate a site if the effective field is greater than the coercive field at the temperature specified This means that the shape of the Hc T curve near Tc can greatly change the characteristics of the problem In add
75. problems Note that having the check boxes checked in the batch page does not effect prob lems run interactively CLOSING THE SCRIPTING INTERFACE Click the Close Scripter button to close the scripting interface 23 192 LLG Micromagnetics Simulator User Manual CHAPTER 24 Viewing F iles The File Viewer is a simple file viewing utility You activate the View Sheet by clicking the Domain Viewer icon at the top of the screen With the file viewing utility you can load one of four standard LLG files e An lg dom file that contains direction cosines To display a file containing direction cosines click the Direction Cosines Angles button and then click the Load File button You make make an MFM image of this file by checking the appropriate MFM mode and clicking on Compute You may also form the difference between two Direction Cosines Angles files e An lg mask file that contains the position dependent mask file Select a mask file Mask or Hysteresis Mask by selecting the appropriate button e Any LLG file that contains a vector field Select a 3D Vector Field file by selecting the appropriate button e An llg hyspart file where 3D dynamical data can be viewed see the Movie Page on methods for creating Ilg_hyspart files Since the llg hyspart file contains up to three masked projections of magnetization the loading sequence requires you to define the region of interest 1st 2nd or 3rd A three dimensional projection
76. register true 3D coordinates for image charges when you run a problem with 2D Real FFTs LLG can provide the appropriate handling of the images for the magnetic material in the Simulation Volume itself In other computation modes the images of the magnetic dipoles of the sensor in the shields are not included in the calculation This differs from LLG v1 where the computation was done approximately in inverse space LLG allows you to run the calculation in any mode but the only one that supports the images of the charges in the shields is the 2D Real FFT Method However current images and boundary condition charges are included for all cases e Check the Shield Loops box to shield micromagnetic elements from external fields during hysteresis loop calcula tions This is useful when computing the performance of MR head sensors LLG Micromagnetics Simulator User Manual 20 135 Chapter 20 Inputting Data Into LLG Shields Consult the Sample Problems to study how a particular implementation will affect the outcome of your problem RESPONSE TO MODEL ATAN MEDIA CHARGE To compute cross track response you can specify the properties of a magnetic medium to be moved in proximity to a sensor The media has by default an atan transition Specifying the Media Check the Use Move Media box Then specify the following e The position of the Center X Y Z nm of the transition e The axis that the media transition is parallel to X Y or Z
77. saved through the Convergence button in the LLG Main Input Page Each file contains an iteration history and optionally the energy components at each end of each iteration cycle the maximum residual energy and the final equilibrium magnetization energy If you start LLG by opening a llg param file using the Input Params button the prefix of the file you load will be appended by the llg conv suffix and the output file will be written If you wish to specify another name use this Convergence button Default Setting By default the Save Conv Details check box is NOT selected In this mode the energies are not written to the file at each iteration step Only the final energy is saved If you check the Save Conv Details box the system energy and its components are written to the file at each functional iteration or time step Normal operation does not require this although it is useful when you want to view the iteration history of the distribution of energies exchange anisotropy dipolar and external field components The cost is that a huge file is being constantly accessed MATERIAL PROPERTIES LLG MATERIAL These files can be loaded and saved through the Materials Page These are ASCII files that are in a database from which you can load the properties of materials or save the properties of materials that you have input 4 32 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files PosiTION DEPENDENT MAGNETIC
78. searches the grid point by point and a parallel Fourier space implementation of general LLG equation solvers When you use parallel relaxation or time integration output is defined in time This page is for specifying Con vergence and Exit Criteria average or minimum and the Time Step within the convergence radius limit You can use an exchange correlation Exchange Corr scheme for a problem that must be on a grid that is outside of the conven tional micromagnetic limit IMPORTANT NOTE For most problems you can and should use the FFT Method for increased speed that is parallel solutions in time DESCRIPTION VARIABLE LIMITS Energy SOR SOR 1 lt SOR lt 2 Convergence Am 0 x Am x 107 Iterations Ncount PESAS 1009 Energy Up Nup 1 lt Nup lt 100 Number RHS Noe 1 lt Nns lt 10 Gamma MHz Y 0x y 1079 Alpha a O lt as2 Start t ns Ty 0x x 108 Stop t ns T2 0x lt 108 Temp T K T 0 lt T lt 108 RN Seed lseed integral 0 lt Leg lt 108 Time Step ps At 109 lt At lt 108 Exchange Corr Dexchange 10 lt Dexchange lt 10 LLG Micromagnetics Simulator User Manual 10 89 Chapter 10 Inputting Data Into LLG Computation RELAXATION METHOD The energy minimization solver relaxes the magnetization one point at a time which is done by rotating the magnetiza tion towards or past the effective field vector within a sub element with the rotation constrained to be in the pl
79. select 3D currents you MUST specify the input and output regions for the current flow for current conservation to work To do this click the Specify 3D Current button which activates the cur rent Mask Editor SPECIFYING REGIONS OF ENTRY AND EXIT FOR 3D CURRENT Using the Current Editor you can specify regions of entry and exit for the current You can use the mask tools see Chapter 21 1 Using the mouse draw the region that bounds the entry or exit point for the current 2 Fill the Internal or External portions of the region with current by selecting the appropriate Fill Mask Region 3 Define whether the current is entering I Entering or exiting I Exiting the structure under Mask Properties NOTE You MUST specify current entering and leaving the structure for current conservation to work 4 Randomly or uniformly fill the region by selecting Random Fill or Uniform Fill Specify the Fraction of the uniform variate that fills the region that is uniform random numbers are generated between 0 0 and 1 0 and the Fraction above the fraction entered is accepted for current paths 5 For any given view projection you can specify that the current enters or exits via the Top the Bottom or over a range as indicated in the Lower and Upper edit boxes 6 Once you have created a current mask you can Save Masks or Read Masks to binary files 7 Please remember to click the Accept Changes button if you wish your inputs to update the LL
80. teak ER naiv CHAPTER 16 nputting Data into LLG NoteS ae CHAPTER 17 Inputting Data into LLG Uniform Hysteresis Loop m uuunrennnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn Specifying a Union EOOD cia Specilying a RotationallEO0D 2 inet das d iE AA coo deem Y quet A y adn ease Specifying Loop E Ce e EEN Specifying The Number Of Loop Torque MagnetoiTietry EE CHAPTER 18 nputting Data into LLG Non uniform Hysteresis Loop nene Specifying Non uniform Sampling Hysteresis Loop Specifying Hysteresis Field Sections eene eene nennen nnne nnn rennen nennen nnns Example of a Non uniform Hysteresis Loop ssssssssesseseeeeeeene eene enne nennen entren nnns CHAPTER 19 nputting Data into LLG H t and FMR Pages ernnnnunnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnennn Specifying Time Dependent H Fields Specifying Projection Direction cccccccsscccesseeceeeeeceeeeeeceeceneeeeeeeceeeeeesesceeeeeseseeeeeeeesseeeeeeeesseesseeeeseeesaeeesseeeaeeess Sp cifying Time Dependent Field cocoa ad aee eee e ede Pe dx Specifying Sin soidal Fields 5 12 3 cerita E oa d tenen Ya keen ad an ONERE RE za EVA de USER AMENS DX TN La EO A d auo Reading and Saving Time Dependent Field Input and Output Files ono Specifying Time Varying Position Dependent Fields FMR and Dynamic S septibiliby 22 t eei petet ec rite t er pr ree ted ioa bog ved o ate e e EE tas CHAPTER 20 nputting Data into LLG Sh
81. the coarse graining problem to the finite temperature problem in micromagnetics using renormalization group methods Please see Physi cal Review Letters 90 20 207201 2003 to see how to rescale A M K and H at fixed temperatures if you know Tc RN SEED When finite temperature calculations are required a random number generator is used to generate gaussian random variables The random number sequence is initialized with a random number seed an integer Internally if you do not choose a random number seed LLG will select one for you based upon the date and time that the simulation was 10 94 LLG Micromagnetics Simulator User Manual Chapter 10 Inputting Data Into LLG Computation started If you want to seed the same random number sequence for temperature dependent computations fix the ran dom number seed EXIT CRITERIA There are four ways of exiting a calculation by satisfying the convergence criteria You can specify that the residuals display one of the following during the simulation phase e The absolute value of the largest change in a single direction cosine Max M e The absolute value of the average of all direction cosines Ave M e The absolute value of the largest normalized torque Max T e The absolute value of the average normalized torque Ave T For Permalloy structures composed of 5 000 10 000 10 nm sub elements a maximum convergence criterion is rigor ous if you set the exit criterion to between 1 x
82. the functionality specifications documented in this manual Trademark and Copyright LLG Micromagnetics Simulator is a registered trademark of Licensor No right license or interest to this trade mark is granted hereunder LLG Micromagnetics Simulator is copyrighted by Licensor General Information You may not sublicense assign or transfer the license or LLG in whole or in part except as expressly provided in this License Agreement Any attempt otherwise to sublicense assign or transfer any of the rights duties or obligations hereunder is void This Agreement will be governed by the laws of the State of Arizona and Oregon applicable to agreements made and to be performed in the State of Arizona and Oregon Should any part of this agreement be declared void or unenforceable by a court or competent jurisdiction the remaining terms shall remain in full effect Fail ure of Licensor to enforce any of his rights in this agreement shall not be considered a waiver of his rights including his right to respond to subsequent breaches Should you have any questions concerning this agreement you may contact Licensor in writing at Michael R Scheinfein IIgmicro mindspring com or IIgmicroeapOmindspring com or call 503 522 9317 Cellular 503 292 4686 Phone FAX BY USING THIS SOFTWARE YOU ACKNOWLEDGE THAT YOU HAVE READ THIS LICENSE AGREEMENT UNDERSTAND IT AND AGREE TO BE BOUND BY ITS TERMS AND CONDITIONS YOU FURTHER AGREE THAT THIS A
83. ume A uniform cubic discretization scheme has no intrinsic demagnetization effects within each sub element Non uni form grids have non uniform demagnetization fields within the cell The variable cell size has been implemented for computing thin film properties where out of plane magnetization components are rare In this case thin platelet dis cretized elements can be selected but they should be square in plane to prevent a magnetic field self bias Uniform grids will always produce unbiased solutions To specify a problem enter the dimensions nm using the sidebars or edit boxes Since the discretization is uniform rectangular the dimensions must be integral multiples of some minimum cell dimension along that direction The memory required to compute a given structure is shown LLG will not let you exceed the physical memory capacity of the computer SIMULATE A MOVIE Once you have completed a simulation and stored a movie you can reinitiate the calculation whereby instead of recomputing the magnetization you can sequentially load the direction cosines that are stored in the movie file into the simulation In this mode you can replay a movie and simultaneously visualize the effective fields and energies associated with the direction cosines stored in the movie The limiting factor is the availability of enough memory since all computational arrays are allocated and the entire movie file is loaded This mode allows you to examine all of th
84. with the Drawing Tool see page 141 Right click the graphic and select Specify Selected Region for Edge Property Effects from the pop up menu Check the Roughen Edge box and specify the Amplitude and Wavelength of the roughness in the edit boxes a RON Right click the graphic and select Fill Selected Region from the pop up menu SPECIFYING THE DEMAGNETIZATION EDGE When the square cells of your region are not aligned with the Cartesian axes the edge of your structure will look like a staircase in other words the approximation to the edge is step wise pulses LLG can compute the demagnetization effects of edges that are not aligned with the grid You can define a demag edge for three dimensional problems only Only one demag edge shape is allowed per problem That shape can be a circle an ellipse or an irregular polygon The shape must lie in the x y plane it will be extruded so as to apply to all layers in z The exchange interaction has been defined to be rigorous on 45 degree cuts For all other cuts the exchange is approximated using volume ratios of the cells Therefore a circular disk on a Cartesian grid problem will still have symmetry breaking even when the edges are computed with this method LLG will compute the eight in plane nearest neighbors the cell above the cell below and the self field using real space sums Each cell will be defined by a polygon possibly irregular of no more than six sides The remaining terms are computed
85. you can make variations on an existing problem by loading an existing lo param file and looping through the parameters You activate the scripting engine by clicking the Activate Scripter button in the Batch Page or by clicking the script SCR icon in the Tool Bar LLG Micromagnetics Simulator User Manual 23 189 Chapter 23 Simulation GENERATING A BATCH FILE USING A LIST OF EXISTING FILES ME oe PZI Generate Variations On Fixed Parameter File Bold Selectable Items May Be Varied CheckBox Choose Files lt Add Uniform Boundary Conditions al Mla v2 O Nwork test S ample3 llg param Multi Fi 0 Period Type 0 None 1 X 2 Y DIS 4 XY 5 XZ 8 YZ Mlg v2 0 work test S ample DG Io param Insertio 0 0000 0 0000 0 0000 Boundary Condition Left mx my mz AI Mo ee ample r ga e R Mla v2 0 wwork testsS ample amp ll param 0 0000 0 0000 0 0000 Boundary Condition Right mx my mz Mla v2 O workMes S amples lig_param 0 0000 0 0000 0 0000 Boundary Condition Front mx my mz Mig v2 0 workStest S ample4 lla param O 0 0000 0 0000 0 0000 Boundary Condition Back mx my mz Mla v2 O workNMestNtestllg param 0 0000 0 0000 0 0000 Boundary Condition Bottom mx my mz Allg v2 O worktest S ample lig param 0 0000 0 0000 0 0000 Boundary Condition Top mxmy mz Mlatv2 O workMtest S ample2 lig param ry p Yy Mat
86. 0 K erg cm K erg cm 1010 lt K 10 A uerg cm A uerg cm 10 lt A 10 K erg cm K erg cm 1010 K 10 Rho uohm cm p uohm cm 0 01 p X106 AMR Ratio AMR 96 0 0 lt AMR lt 1 0 N Layers N O lt N lt 1024 Layer Niayer 0 S Njayer S 1024 Layer T nm Thickness Thayer 0 01 S Tiayer 10 0 Load Layer Aj uerg cm Aj uerg cm 102 Aj lt 10 2 Load Layer Ajj uerg cm Au werg cm 102 Ai lt 102 Bilinear Coupling uerg cm Abilinear ue rg cm 10 lt A seg 10 Biquadratic Coupling uerg cm Bbiquadratic ue rg cm 2 2 10 Bbiquadratic S10 GMR fraction GMR 0 0 GMR S 10 0 Polarization P 0 0 EP 1 0 Easy Axis Direction Cosines UNIAXIAL one vector Ax x projection Ax 1 0 Ax 1 0 Ay y projection Ay 1 0 Ay 1 0 Az z projection Az 1 0 Az 1 0 Easy Axis Direction Cosines CUBIC two vectors Ax 100 x1 projection Ax 100 1 0 Ax 100 1 0 Ay 100 y1 projection Ay 100 1 0 Ay 100 1 0 Az 100 z1 projection Az 100 1 0 Az 100 1 0 Ax 010 x2 projection Ax 010 1 0 lt Ax 010 1 0 Ay 010 y2 projection Ay 010 1 0 Ay 010 1 0 Az 010 z2 projection Az 010 1 0 Az 010 1 0 LLG Micromagnetics Simulator User Manual 14 113 Chapter 14 Inputting
87. 1 22 The self magnetostatic field energy Eg can be represented in a number of equivalent forms but for these purposes the most convenient represen tation is 1 3 E av3n aM where the self field H is determined from the negative gradient of the scalar magnetic potential gt H Vo The magnetic scaler potential satisfies Vo 4nM Vea inside the ferromagnet and LaPlace s equation outside of the ferromagnet via 0 and at the surface um and 2 4nM y E in the two dimensional case for example The regularity of d at infinity is also required This can be guaranteed by solv ing for the potential using Green s function methods The calculation of this self field energy is the most computation ally intensive aspect of solving the micromagnetic equations The external field energy E for an applied field of Ho is simply given as gt A E dVH aM LLG Micromagnetics Simulator User Manual 3 27 Chapter 3 Introduction to Using LLG To calculate the magnetic microstructure in ferromagnets the time evolution of a magnetization configuration inside a ferromagnet which is described by the Landau Lifshitz Gilbert equation must be solved The Landau Lifshitz Gilbert equation has been examined experimentally and theoretically 28 29 32 81 82 and found to yield an accurate descrip tion of the time evolution of a magnetic moment of fixed magnitude in a magnetic field This equation has the following fo
88. 1 July 2001 l llg param Variation 12 Variation On Magnetization emu cm 3 Systems Wide Variables O Run Type 0 Windows l Batch 1 Dual Processors 0 Single 1 Dual 0 Save To Conv 0 Single 1 Dual 1 Save To Conv Every N Interation Steps Movie Variables Catch The Edge 0 No 1 Yes Write To Movie 0 No l Yes Movie Increment Steps Between T Movie Frames 0 200000 Edge Increment General Uniform Variables Dimension Nx Number Of Subdivisions in X Ny Number Of Subdivisions in Y 7 Nz Number Of Subdivisions in Z Lx cm Discretization Size in X FIGURE 5 Journal Viewer Journal Contents Page MODIFYING COMMENTS IN PARAMETER FILES When a llg param file is loaded into the Journal Viewer you can edit the title and the comment lines This file can be saved to disk using the File pull down menu at the top left of the main window The option of editing the file data or the journal itself is disabled CREATING A NEW JOURNAL You can create a new journal at any time Since llgJournal exe can search any file system and compile any sequenced list that you like you never have to worry about deleting or loosing your journal files However you can maintain a time snapshot of your LLG file system by keeping your generated lg journal files as a record To create a new journal 4 36 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files click the New File icon in the task bar or select File
89. 176 damping torque visualizing 174 database See materials database demagnetization field visualizing 171 deviation in domain dimension 156 dH dz z nm example of 178 view option 176 direction cosines display a file containing 193 file type 32 probing data 71 v1 input and output file format of 41 discretization volume fixing with commit size 74 disk drives searching for LLG files in 37 disk space information 68 display settings 22 divergence of m 176 Index 279 example of 177 dom files v2 input and output file format of 43 domain example of 169 domain modes using color wheel to display views 66 domain states saving during a hysteresis loop 180 domain wall sample problem with Fe 243 dual processors 92 dynamics 91 E easy axis 116 edge roughness specifying 143 161 effective field visualizing 171 elapsed time 165 energy up 94 energy slower 91 energy density visualizing 171 energy minimization 90 energy of configuration evaluation of 165 energy search 91 energy SOR 91 exchange and correlation 95 exchange bias 116 exchange coupling specifying 227 exchange stiffness modifying 115 exit criteria 95 maximum 93 recommendations for selecting 93 external applied field 103 F Fe sample problem for domain wallin 243 FFT method 92 2D real 92 3D complex 92 limitation using with shields 135 field parameters updating during a calculation 182 field shields See shields field
90. 2 LLG Micromagnetics Simulator User Manual Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETERS SHEET BOUNDARY REGION EXCHANGE PAGE BC Bitmap Edge Custom Input Custom Graph Main Params Exch Materials Graph Media r Regional Boundary Exchange Coupling Ax uerg cm D DA 0 Axe uerg cm 0 0 Aus uerg cm 0 0 Ay uerg cm Dad 0 Az uerg cm 0 0 Az uerg cm D 0 r Reg Boundary Bilinear Biquadratic Exchange Coupling Bilinear By uerg cm 0 0 By uerg em 0 0 Bz uerg cm Dad 0 Bz uerg cm D a4 0 Biquadratic Cy uerg cm 0 4 0 Cy uerg cm 0 H 0 C uerg em mE 0 s 0 Cz uerg cm ES 0 GMR BMR 07 0 Clear All FIGURE 74 Position Dependent Parameters Sheet Exchange Page This page is for inputting position dependent boundary exchange parameters such as for exchange isolating a small region in the center of a structure that is defined by grain boundaries where Tantalum might have segregated leading to exchange isolation There are six sides to each cell and in general there are X x y y Z and z projecting faces for any Cartesian structure Here the pluses and minuses refer to sides whose outward facing normals are directed along the pos itive or negative axes Actions supplied throu
91. 20 Erud EX CL Es 220 CHAPTER 32 Sample Problem 7 Layers with Demag Coupling in MRAM 223 Input Sheet MalniPage ice crap Amen ee ede rere cte ae tb ve gue ee vea an gee ia das 223 Input Sheet Eayers Page uueiin retinere Eee tae P egg e Se eee eg rx ena d d NER Le 223 Input Sheet Computation Page 224 Input Sheet Initialize e ET 224 Input Sheet Uniform Hysteresis Page 224 Simulation SMSC m M 224 aru mp EE 225 CHAPTER 33 Sample Problem 8 Antiferromagnetic Exchange Coupled Permalloy Platelets 227 Input Sheet Main Page id eal eae A A de a 227 Input Sheet Layer Properties Page 227 Input Sheet Computation Pagerie uiii iii A ua dede ed Rv gue da 227 Input Sheet Initialize Page enne nnnn ener nnn nrn ren nnn sinn nr entes tren ns sin net senis nennen 227 Input Sheet Hysteresis Uniform Page enne eene nnne ens en rent nnne internen nennen 227 Eu 227 EIERE ede EA ga e ede eee AE Ed dd ENN 228 CHAPTER34 Sample Problem 9 GMR for Bilinear Interlayer Exchange between Platelets 229 Input Sheet Malaga A DL H E eee 229 Input Sheet Computation Page 229 Input Sheet Layer Properties Page 229 Nput Sheet Current Page eo edd ed Rod e uud Bee Aas Pen RET Re dean 230 Input Sheet Initialize Page ee erect venu erue gei te e Y E epe ege fay Na le 230 Input Sheet Hysteresis
92. 2D 3D Common Parameters Random Number Seed 0 Unify Grain Properties m 3D Grouping Computational Number of 3D Cell Groupings 1 FIGURE 77 Position Dependent Parameters Sheet Media Page The Media Page is a simple tool to assist you in generating parameter properties for regions that are common in mag netic media where there are many grains with separate yet consistent magnetic properties Groupings can be done in two or three dimensions For two dimensional groupings set the Mean Domain Dimension and the Deviation in Domain Dimension For three dimensional groupings specify the Number of 3D Cell Groupings In the 3D case LLG will randomly choose n points within the cell volume Then cells of a given group are so assigned to ensure that each cell is closest to a given point This is a simplistic implementation of three dimension Voronoi cells 1 Enter the parameters in the Main Params and Exch Pages Define suitable grain structures through the Media Page Enter the Mean Domain Dimension nm in the edit field This sets the length scale for defining the domains i e grains Specify the Deviation in Domain Dimension nm in the edit field i e the degree to which the size of the grains is random Since the randomness is set using a random number generator you can select a Random Number Seed to recre ate a given tile distribution Check the Unify Grain Properties box if you want each tiled reg
93. 3D visualization Arrow When 3D objects are selected and vector data are present the arrow is the most graphically economical representation It is a line with a carat hat for orientation Cone When 3D objects are selected and vector data are present the cone is the most graphically expensive rep resentation It is a 3D hollow cone whose properties can be set in the OGL Props Sheet OGL Page Vertex Cone When 3D objects are selected and vector data are present the vertex cone can be used to provide an alternative representation The vertex cone is a collection of triangles with aligned tips The properties of the vertex cone can be set in the OGL Props Sheet OGL Page Ortho This toggles between orthographic and perspective views of 3D data The best 3D Cone and Vertex Cone viewing is with the OGL Lights on It is recommended that you turn the lights off for all other views 5 60 LLG Micromagnetics Simulator User Manual Chapter 5 LLG Environment Graph Scaling e Box Visible This toggles the bounding box e Shield Visible This toggles the shields when they are present e Size This zooms into and out of the view You can change the magnification 0 1 lt magnification lt 10 of the view e Gain This scales data linearly to amplify sensitivity when you are viewing bitmaps or contours This is useful for visualizing small changes in data such as ripple e Lev The level indicator can be turned on and off wi
94. 4 4 4 4 4 4 4 ch EE RR Pob PPP PPE EEE EEE D Dp cb Dp Dp FFE EEE EEE PAAR EE E 4 EE EEE EE EE de EE i le le ll ee le aan ds en gt EE cdo RR FIGURE 42 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Transition Magnetization LLG Micromagnetics Simulator User Manual 11 99 Chapter 11 Inputting Data Into LLG Initialization 3D VoRTEX MAGNETIZATION You can use a planer vortex to start the simulation The flux closure pattern provided by a planer vortex is often one of the low energy states and can serve as the appropriate starting state Care must be taken to ensure that the mesh dis cretization is fine enough not to pin the flux vortex core at the center Select the plane of the vortex by checking the appropriate option If the Simulation Volume has multiple planes then all planes will be initialized in the same vortex state except for pinned layers A A shot of of oe dn kr Am dn tm dn dm dr dr 4 4 9 4 4 4 4 4 4 4 4 PEE EE EE 47 4 47 EEE EEE EEE 47 47 4 4 HER EEE EERE EEE EEE M7 4747 A 47 Mk RRA CEE CREME MEME REE EERE EERE ERE EH EE EE OEE BEBE 47 47 47 47 EEE 47 EEE 4 47 4 4 ECE eee eee net eRe eee 4 4 ee 4 4 4 4 4 4 4 4 4 4 4 4 4 47 47 4 CE EEE EE ERE EE EEE EEE EEE EEE Hebe 47 4 4 4 47 4 4 4 4 4 4 4 4 4 47 skabb osb 1 4 erccerncet tLiteseet ft AR t r l t tt NN A ih i1 l X 1 H 1 1 t 1 ie 1 I t
95. 400Oe gt A nterlayer 1 gt 2 0 16erg cm Scroll back to layer 1 Enter A10 0 0 and A12 0 16 Click LOAD LAYER PROP to register your changes 6 Exit the page by clicking Accept Changes INPUT SHEET COMPUTATION PAGE These are identical to Problem 7 INPUT SHEET INITIALIZE PAGE These are identical to Problem 7 INPUT SHEET HYSTERESIS UNIFORM PAGE These are identical to Problem 7 COMMENTS Notice that the magnetization layers are the same and that the total magnetization is nearly zero at zero field in the antiferromagnetic state LLG Micromagnetics Simulator User Manual 33 227 Chapter 33 Sample Problem 8 Antiferromagnetic Exchange Coupled Permalloy Platelets FEATURES Structure 250 nm x 100 nm x 20 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 25x10x2 Material Permalloy layer 1 and Permalloy layer 2 Relaxation 3D Complex FFTs Initialization Uniform magnetization directed 30 off the long axis Hysteresis Uniform H 1250 Oe NA 21 Coupling Antiferromagnetic exchange coupling strength 400 0 Oe A AFR Gr Gr a ux y y d d KE e ZS E e E Y Reece e de e A Se ee E uy Se g e ee E KR E e e ee e e d E KR E e g e x E VP e e e Y Wwe ee eo ee E A 7 H 1 t d N APF gt gt gt gt gt AFF rp VW APF Pera sawn a ms h a a WM cocaoa w Ww gt gt DAA NY A A A A A 4 1 1 AT
96. 5 hysteresis loop saving domain states during 180 using exchange and correlation feature 95 hysteresis non uniform 127 dividing the field into sections 127 example of specifying field points for 130 215 parameter limits of 127 sample problem for a magnetic platelet with 215 specifying loop direction for 129 hysteresis uniform 123 parameter limits of 123 sample of rotational loop for a magnetic platelet 211 sample problem for 207 specifying field points for 123 124 specifying loop direction for 126 specifying maximum external field for 125 specifying rotational loops for 125 Hz nm view option 176 important note regarding 1 layer structures 114 regarding 2D real FFT method 92 regarding 3D currents 109 regarding color of mask 142 regarding FFT method 89 regarding H z dH z dz and d2H z dz2 176 regarding jagged edges on curved surfaces 239 regarding layers input 74 regarding periodic arrays and 2D real FFTs 87 regarding setting boundary condition field 76 234 regarding total thickness of layers 114 regarding using exchange and correlation with hysteresis loops 95 incident beam specifying angle of 176 initialization loading angles from a file 97 parameter limits of 97 in plane exchange parameter 152 input sequence 73 of material properties 81 input specifications file type 31 installing LLG 22 LLG in kanji and hangul environments 23 LLG with Windows2000 23 the prote
97. 5 x 10 x 1 Material Permalloy Relaxation 1 Pt Energy Minimization Initialization Uniform 10 from X in X Y Plane Hysteresis Non Uniform Hysteresis Loop 0 0 FIGURE 129 Surface Magnetization and Non uniform Hysteresis Loop during Switching in 3D Arrows LLG Micromagnetics Simulator User Manual 30 217 CHAPTER 31 Sample Problem 6 Simulation for Asymmetric Bloch Wall in Permalloy t c 4 4 4 amp Ef ERII ZAL hem RKERECCCCECREAREA RI 401012012 1401010000 CV EE HEREERRR RRR NPs eee eEEKEERRA KS ve ee yv EE RAR HD De Aa kA A haa hn YIIYNYISJAJ AAN ICC EE E E EN A A A A O A AAN A A 9 5 39 G4AARXNNNNTENN SN A DEP PPPS FIA AAV TEEN NALLY STE This is the simplest type of 2D problem It simulates the structure of the so called asymmetric Bloch wall often termed the LaBonte wall LLG has facilities to simulate the detailed structure of domain walls using the 2D Green s Function A problem for a thin film of Permalloy is set up The thickness of the film is selected to be thicker than that supporting a N el wall yet thinner than a film that supports bulk Bloch walls and N el surface caps INPUT SHEET MAIN PAGE Initiate an LLG computation From the Input Sheet Main Page select the 2D Green s Function as is appropriate for the study of domain walls Enter the dimensions of the problem X nm is 400 nm and Y nm is 100 nm Enter the dis cretization for the proble
98. 75x50x1 Material Permalloy Relaxation FFTs Initialization Vortex in Y Mask Editor Shaped structure 37 240 LLG Micromagnetics Simulator User Manual Chapter 37 Sample Problem 12 Shaping Magnetic Elements AAPP e o to ot e A E rH nl Baum vt ep in ph t ER ep na np npe pot hot p oa op OS E E B od oh eh nh dt dd ml mm b b O b 7h a E SEU S Sa SA S nb nb nh cech eb cb mm a A JR Ba rope e EE cp ce tt bot ch p ca op ce b ca b ct A E p RR NN TR RS IHR PE np pt ch eS a E E EE LARA EE EA RT F R Or ce e t pt pt pt p ce op ce pt pt t ch oe b ca A Ace a TP T TLD T E tp PR e P E a E E PAA B ch cech tm ch eh ih ib EE 8 558 CT Rc Re S9 RT A G JE root np pnt pt ot bn et bot tt hh A eb TT CR n nennt ot o ESA A bb ach eth cho ENEE h c a a a ea nece ce oe e pt EE a CP TR Ta enl t nh chr eet teh nci hc cA a a Se Hh co oe nece pt EE E e MRD n heh t hes once hc e T VN tt eee be E A A PSS to a hne tm ch choke t Je ch en nh on on en e e Seve SE GE PGE ab ot ad ad de TTT EEN a EE ei MAAT E dr AKT al a EE EN base aC MRNA Ss 4 4o do ed 4 47 07 7 47 dr dm 2o di s OASU R CR Re de qe de nde dn dn dn dn demam TE EE a ee A ede de de ie dnte dinde inde dde de de dr dc dr asa m a o oa RAR BR A A din de de dede dn de de dn demde imam m TT EE EEN a eeeeceecmeimeemeeeeeen M dc de eodd dde dm dm dr dro rera EEN Pr Karene renere DM seerne need PA AR O RRA a AAA RRA AAA A A OA d X d a La m ARO Se ALLA rtr rernm ar
99. AFP P gt rss ARCAM LE ECKE 2 ANN NX Y A 1 t N S A 2 2 2 5 A m we 44 dau de de du Ae N S KS Sg SEL E e e es E ER li ae oe oe e WE e de ZS n e e E E d Y E y Z e e E E E Y FIGURE 145 End and Mid shank Magnetization of the Tip LLG Micromagnetics Simulator User Manual 41 254 CHAPTER 42 Sample Problem 17 Hollow Pyramidal MFM Tip Y o j Fr dr y AA mma WO nm x gt gt gt DA N Si N N This sample problem illustrates the simulation of a hollow MFM tip s magnetization INPUT SHEET MAIN PAGE 1 Initiate an LLG computation 2 Enter the dimensions of the problem X nm is 200 nm Y nm is 200 nm and Z nm is 200 nm 3 Enter the discretization for the problem N is 20 Ny is 20 and N is 20 INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 aS SN Click the Globals tab then click the Material Selector button Select Co from the Materials Page but SHEET BOUNDARY CONDITIONS PAGE 1 Click the Boundary tab 2 Set the magnetization along M to 1 for the Top Z N 3 Click Accept Changes to log your changes INPUT SHEET COMPUTATION PAGE Click the Computation tab 1 a OND Check Time Faster Enter 2 0 ns for the ps Time Step Select the 3D Complex FFT method Click Accept Changes to log your changes Click Accept The Co
100. ATION SHEET INFO PAGE Through the OGL Information Sheet Info Page you can examine system information m Information Computer System Number of CPUs 2 Processor Architecture INTEL Processor Type 686 Processor Revision 8 Processor Stepping 1 Memory MB Free Memory MB 417 Free Memory 7 Output Ez clock ill Calc FIGURE 23 OGL Information Sheet Info Page OGL INFORMATION SHEET Disks PAGE Information System Disk Usage Dr totale Jean FLOPPY FLOPPY 1007 4188 2703 FLOPPY CD ROM CD ROM 4477 5646 FIGURE 24 OGL Information Sheet Disks Page Through the OGL Information Sheet Disks Page you can examine disk space 5 68 LLG Micromagnetics Simulator User Manual Chapter 5 LLG Environment OGL INFORMATION SHEET OUTPUT PAGE Output Log NT Output 2 info S Disks FIGURE 25 OGL Information Sheet Output Page The OGL Information Sheet Output Page is where messages are written for the user when LLG performs some special task OGL INFORMATION SHEET CLOCK PAGE KE August 2002 gt Sun Mon Tue Wed Thu Fri Sat 28 29 30 31 1 3 4 5 B 7 8 39 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 j 4 5 7 Today 8 2 02 info Ef Disks 17 Output EZ clock FIGURE 26 OGL Information Sheet Clock Page The OGL Informat
101. Accept Changes when you have entered data for all of the sections While editing the time dependent field sections click DELETE SECTION to remove field points from the hysteresis loop Remove all the specified Time Intervals by clicking the Clear All button SPECIFYING SINUSOIDAL FIELDS You may optionally enter a Sinusoidal field that will be superimposed upon the fixed interval fields that are specified with the Time Dep H Page The sinusoidal fields allow you optionally to investigate FMR type excitations BON You must enter the value of the ac field components into the hy hy and hz edit boxes You may only specify a sin gle ac field You can enter the starting and stopping times ty and te in ps This allows you to time shift the ac component of the field e You can enter the frequency b 1 ps and the shift c ps to fix the ac field frequency and the phase shift of the excitation wave READING AND SAVING TIME DEPENDENT FIELD INPUT AND OUTPUT FILES You can create a field file for generating hysteresis loops as an ASCII file using a text editor e These formatted files lo hysfield can be read into the program with the Read Input File option THE PRO GRAM ALLOWS FOR NO MORE THAN 16384 FIELD POINTS When reading a file the program assumes that the field points are distributed non uniformly The field values are entered into the non uniform edit field and dis played in the OpenGL window Such fields can be edited When
102. Appl Phys 40 6 2450 1969 A Aharoni J Appl Phys 37 8 3271 1966 A Aharoni J Appl Phys 38 8 3196 1967 A Aharoni Phil Mag 26 1473 1972 A Aharoni phys stat sol a 18 661 1973 A Aharoni J Appl Phys 46 2 908 1975 A Aharoni J Appl Phys 46 2 914 1975 M E Schabes A Aharoni IEEE Trans Mag MAG 23 6 3882 1987 A Hubert phys stat sol 32 519 1969 mp Ae mn bk OD e 3 28 LLG Micromagnetics Simulator User Manual Chapter 3 Introduction to Using LLG 22 23 A Hubert phys stat sol 38 699 1970 12 13 14 15 16 17 18 19 20 21 M E Schabes H N Bertram J Appl Phys 64 3 1347 1988 G T Rado J R Weertman J Phys Chem Solids 11 315 1959 G T Rado Phys Rev B40 1 407 1989 R Victora J Appl Phys 62 10 4220 1987 C Herring C Kittel Phys Rev 81 5 869 1951 G Shirane V J Minkiewicz R Nathans J Appl Phys 39 2 383 1968 C C Shir J Appl Phys 49 6 3413 1978 R Victora Phys Rev Lett 58 17 1788 1987 B D Cullity Introduction To Magnetic Materials Addison Wesley Publishing Co Reading 1972 G T Rado Phys Rev B26 295 1982 G A Prinz GT Rado J J Krebs J Appl Phys 53 3 2087 1982 M R Scheinfein and J L Blue J Appl Phys 69 11 7740 1991 LLG Micromagnetics Simulator User Manual 3 29 CHAPTER 4 LOADING AND SAVING FILES
103. B ATYPE anisotropy direction for uniaxial case DO 100 I 1 NUM READ UNIT 1 DB LABEL I DB CA DB MS D DB CK I DB_CKC D amp 4 38 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files DB CS I DB RHO D DB AMR I DB ATYPE 100 CONTINUE 1 FORMAT A20 7 1X D15 5 1X A1 Hysteresis Field Profile llg hysfield Type External Hysteresis Field File Format Formatted ASCII Where Hysteresis Dialog Prompt Read Input File Write Input File Suffix llg_hysfield Variables NHPTS number of hysteresis field points NHPTS lt 1025 HX field in Oe along x direction HY field in Oe along y direction HZ field in Oe along z direction READ UNIT I NHPTS 1 FORMAT I4 IF NHPTS GT 1024 THEN NHPTS 1024 CALL READ_ERROR_HANDLER 11 ENDIF DO 100 I 1 NHPTS 100 READ 29 2 HX D HY D HZ D FORMAT 3F10 2 Coupling Tensors llg coup Type Demagnetization Coupling Tensor File Format Unformatted BINARY Where Input Dialog Prompt Read Self Energy Tensor Write Self Energy Tensor Suffix lg coup Variables NX integer number along x direction NY integer number along y direction NZ integer number along z direction ACOEF double precision coupling arrays constants READ UNIT NX NY NZ DO 100 M 1 6 DO 100 I NX NX 1 DO 100 J NY NY 1 LLG Micromagnetics Simulator User Manual 4 39 Chapter 4 Loading Saving Files DO 100 K NZ NZ 1 100 READ UNIT
104. BCs Pages 9 86 LLG Micromagnetics Simulator User Manual Chapter 9 Inputting Data Into LLG Boundary Conditions BIASING A STRUCTURE WITH AN EXTERNAL FIELD If you want to bias a structure with an external field that is generated by magnets 1 Set up the parameters for the internal grid of interest 2 Make the material properties of the grid those of the permanent magnet especially the magnetization For example if the magnets lie at X 0 and at X Xmax and are magnetized along X set m left 1 0 and my right 1 0 and be sure that M on the Globals Page is that of the permanent magnet 3 Check the Write File box click Output File Name and name the file NOTE In general you can read in or save a formatted position dependent magnetic field by clicking the Input File Name or Output File Name button To enable the read file or write file options you MUST signal your intent to LLG by checking either the Read File and or Write File boxes 4 Be sure to click Accept Changes if you want to log the changes into the data structure Once LLG has computed the field tensor the field from the boundary conditions are computed and saved to file 5 Exit LLG and restart your real problem that is the real sensor configuration 6 Use the Boundary Conditions Page to read in the fields generated by the magnets Do not enter anything into the boundary conditions fields Close the page and proceed You will be able to visualize the
105. Buffer1 Format 4i m pLLG m nCurHpts m fileStdio WriteString m strBuffer1 n 0 for t Inti 0 i m pLLG m nCurHpts i m strBuffer1 Format 9610 2f m pLLG m dCurLoop i m strBuffer1 m strBuffer1 m fileStdio WriteString m strBuffer1 m m fileStdio Close return TRUE Materials Database Files t BOOL CDatalO WriteMatBaseFile2 01 t pChar pFileName t BOOL bAllocate LLG Micromagnetics Simulator User Manual 4 45 Chapter 4 Loading Saving Files Open File if Im fileStdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate Am fileException FileExceptionHandler amp m_fileException return FALSE Write Header String m fileStdio WriteString m strVersion n 0 m strBuffer1 Format 964i t Int bAllocate m fileStdio WriteString m strBuffer1 n 0 for t Inti 0 i lt t Int bAllocate i m strBuffer1 pr for t Int j 0 j lt 20 j m strBuffer1 SetAt jom pLLG m MatBaseLabel i j m fileStdio WriteString m strBuffert n 0 m strBuffer1 Format 9610 3f m pLLG m MatBaseA i m fileStdio WriteString m strBuffert nm m strBuffer1 Format 9610 3f m pLLG m MatBaseMs i m fileStdio WriteString m strBuffert WN0 m strBuffer1 Format 9610 3f m pLLG m MatBaseKu 2 i m fileStdio WriteString m strBuffert n m strBuffer1 Format 9610 3f m pLLG m MatBaseKud i m fileStdio WriteString m strBuffert n 0 m str
106. Buffer1 Format 9610 3f m pLLG m MatBaseKc i m fileStdio WriteString m strBuffert n m strBuffer1 Format 9610 3f m pLLG m MatBaseKs i m fileStdio WriteString m strBuffert WN0 m strBuffer1 Format 9610 3f m pLLG m MatBasehRho i m fileStdio WriteString m strBuffert n m strBuffer1 Format 10 3f m pLLG m MatBaseAMR i m fileStdio WriteString m strBuffer1 no m strBuffer1 Format 2i t Int m pLLG m MatBaseKTypel i m fileStdio WriteString m strBuffert n 0 m fileStdio Close return TRUE Position Dependent Parameter Files t BOOL CDatalO WritePosDepFile2_01 t_pChar pFileName t BOOL bAllocate t Int nMaskSize nArraySize nExchangeSize nIntSize n 3 nMaskSize m nSize sizeof t BOOL nArraySize m nSize sizeof t Double nExchangeSize m nX 2 m nY 2 m nZ 2 sizeof t Double nintSize 3 sizeof t Int 4 46 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files Open File if Im fileStdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate Am fileException FileExceptionHandler amp m_fileException return FALSE Write Header String m fileStdio Write amp m cVersion 64 sizeof t Char Write Integers n 0 m nXin 1 m nY n 2 m nZ m fileStdio Write amp n nIntSize Write PosDep ifrm bDoProgress m dTotal 100 m nOffset 0 m pProgress gt StartProgress 0 100 Writing File m pProgress SetPr
107. Chapter 4 Loading Saving Files Hysteresis Field and Magnetization llg hys Type LLG Hysteresis Output File Format Formatted ASCII Where Hysteresis Dialog or Automatic Prompt Prompt Name Output File Suffix lg hys Variables HCOUNT number of field points H field magnitude in Oe M remanence along field HX field in Oe along x direction HY field in Oe along y direction HZ field in Oe along z direction MX remanence along x direction MY remanence along y direction MZ remanence along z direction MR RES resistance in ohms MR VOLT voltage in volts READ UNIT 1 1 FORMAT Hmag Oe Mmag Ms Hx Oe Hy Oe Hz Oe Mx Ms My Ms Mz Ms R ohm V mV DO 100 I 1 HCOUNT READ UNIT 2 HD M D HX D HY D HZ D MX D MY D MZ D MR RES D amp MR VOLT I 2 FORMAT P9 1 F9 3 3F9 1 3F9 3 2F9 3 SUMMARY OF INPUT AND OUTPUT FILE FORMATS OF V2 Mask Files t BOOL CDatalO WriteMaskFile2 01 t pChar pFileName t BOOL bAllocate t Int nMaskSize nlIntSize n 3 nMaskSize m nSize sizeof t BOOL nintSize 3 sizeof t Int Open File if Im fileStdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate Am fileException FileExceptionHandler amp m fileException return FALSE Write Header String m fileStdio Write amp m cVersion 64 sizeof t Char Write Integers n 0 m pLLG gt m nX n 1 m pLLG gt m nY n 2 m pLLG gt m nZ m fileStdio Write amp n nIntSize Write Mask 4 42 LLG Micromagn
108. Copy Selection 5 Cut Selection 6 Paste Selection 7 Find 8 Replace 9 Change Font of Selec tion 10 Change Color of Selection 11 Print and 12 Print Preview 9 With the Save OGL Bitmap button you can save your active OGL window to a Windows bmp bitmap file 10 With the Save OGL Bitmap to Clipboard button you can save your active OGL window to a Windows bmp bit map file that is embedded in the Windows clipboard for pasting into another application GRAPHICS CONTROLS LLG implements all of the graphics and utility controls in a single nested property sheet array that is always located in the lower left quadrant of the active desktop The LLG graphics control is connected to the last activated OGL window Since the main OGL window can be recursively subdivided you can click on any subwindow with the mouse to connect that window to the OGL graphics controls The active window number is indicated in the Active View Pane at the lower right in the main window r Graph Type m Graph Scaling i 1 sc P s 3D DIGG Contour e 3D Slice Size 8D Surface Domain OO Input Cells Gain Overlays Color Contour AN Arrow UnMask Witz D a Legend Cone Ortho _ Box Visible Vertex Shield Visible DIE Modes Aoc X Color A OGLProps 2 Information ES selector FIGURE 15 LLG Graphics and Utility Control Sheets Each OGL window is numbered as
109. D t 1 H X 1 X A tt Uh RED EE ECKE A KE a a ala EE le ala E EE EE TA hb Urb AA ERR KEE bie EE EE PAP DOD RP PRA UR TR UR RR EE E RU EE EE EE EE A H y l i X 4 DH 4 I 4 D f gt t H 1 1 1 1 1 H H gt MAT at E e x t D settt DH Ria tert 1 y RARA LIA D A prt ater D y PERERA I H ri tf 1t15 14 I A etirtta I A 11212451 y AReeeeraet t tte ee ety D I RAA EA d D ed Y i titii d gt Ptttttt D tt t gt at I H t A t H t M A 1 1 t x t 1 t l gt UA ale E EE EE EE E EE E EE EE EE el PP KEE EE A EE EE EE ee EE E EE Dp DP DR EE DP E EE kk Ek Ek ke de A dk Kb de dd db da p pp dan da da de d de de de db de dp da EE EE E E din c on E EE c p n E EE EE EE n en EE E EE EE E EE ET t t t 1 4 t 4 t A f H i x H 1 t t 1 gt e e a EE am EE EE EE e eee fi tit ett ftt FEY tta tht tert 112 tit ttt Att tit rt th Fret tit rat RIA ttt tit ttt ott gt ye me eee bee eee WEST E ve vi tv Ak LI vi vi ve F F 14 r it l ves PY Y Y vi kd Ly tt A gt e i t Y 5 i t l t Y 1 D 4 DH l 3 t i t Y H i A H A f t 1 i T 4 t y f H H A b gt H gt gt gt bed FIGURE 43 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Vortex Magnetization in Y 2D NARROW OR WIDE For 2D simulations of domain walls you can select the initi
110. Data Data Is In Half Space X gt 0 0 Fix Coordinates Interpolate Coordinates Fix Lower Z Boundary To Z 0 Bottom Z nm 0 Fix Lower Y Boundary To Y Lower Y Lower Y nm 0 Fix Lower X Boundary To X Lower Lower X nm 0 Nx 10 Ny 10 Nz 10 de X Cancel FIGURE 154 Position Dependent Sheet Ancillary Input Data Page This version of LLG has been programmed specifically to read input files formatted to your specifications You must correctly enter the number of finite element output nodes in X Nx the number of finite element output nodes in Y Ny 46 274 LLG Micromagnetics Simulator User Manual Magneto Optical Simulations Supplement and the number of effective finite element nodes in Z Nz The effective number of finite element nodes in Z is that number written in the file regardless of the actual numbering scheme used In the sample file sent the effective number in Z is 4 see LLG full txt on the accompanying CD The rest of the inputs are optional Check the Data Is In Half Space Y gt 0 0 box if the finite element data is from the half space in Y LLG will take the half of the data rendered to the file and reflect it about the Y 0 0 plane Check the Fix Coordinates Interpolate Coordinates box if you would like LLG to use the coordinates in your data and the coordinates in LLG as real coordinates If you do not check this box LLG will match up the edges of the two syst
111. Direction Cosines and Media Demagnetization Field 40 268 LLG Micromagnetics Simulator User Manual CHAPTER 46 Magneto Optical Simulations Supplement INSTALLATION INSTRUCTIONS The customized version of LLG Micromagnetics Simulator is named lig v2 50 Custom MO exe and enclosed on the CD The files on the CD will not install automatically and must be copied to your disk using Explorer Please put the executable in the same directory as your other LLG files The enclosed sample files can also be copied to your hard drive but can be stored in any location THEORY OF OPERATION Magneto optical calculations have been implemented within LLG Micromagnetics Simulator These simulations use the standard LLG computation engine while allowing the user to specify temperature dependent parameters which deter mine local temperature from reading a file or through computing a function LLG has two models for computing the properties of magneto optical materials These models are termed 1 spin and 2 spin models The distinction between the models is that the effective gyromagnetic frequency and effective damping constant are both functions of tem perature in the 2 spin model but not in the 1 spin model 1 sPIN MODEL In the 1 spin model the LLG equation dM T t y gt x ya 3 as M T t xH T t M T OxM T OxH Tt dt 1 0 eee 1 amp M T t SO oa UIS is solved for a position dependent system where the saturation magnetizatio
112. E EE EE EE EE E EE EE EE EE EE EE E EE EE EE temm AAA AA AA AN EE EE EE EE EE EE EE EE EE EE EE EE EE E EE EE EE EE AAAAAAA EE EE EE EE EE EE EE EE EIE EIE EE EE EE EE E E EE EE EE ANAND ARAAAAAAAAAA E EE EE E EE EE EE EE EE E EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE E EE EE EE EE EE EE LP PP P P P D PP DP DP DD EE EE EE EE EE EE EE E EE EE EE EE EE EE EE utut t ntn rng mr EE EE EE EE EE EE E EE EE EE EE EE EE EE EE EE E EL EE EE EE EE EE E EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE E EE EE EE EE EE ARA DADA MARA ARP EE EE EE EE EE EE EE EE EE E EE EE EE EE EE LEE RR III EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE RA EE EE EE EE EE E EE EE EE E EE EE EE EE EE EE EE EE E EE EE PIPPI IA IAL EE EE EE E EE EE EE E EE EE EE EE EE EE EE EE EE E EE PARADA AR ARA RARA AAA RARA AAA AAA AAA AA AAA III AAA FIGURE 41 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Uniform Magnetization 3D TRANSITION MAGNETIZATION You can initialize the magnetization in the form of written disk media tracks You can select the direction parallel to the magnetization and perpendicular to the transitions by checking the appropriate option Enter the number of transitions along that direction in the Transition Number edit box A Me A af af na dd fa A A A A A A A A A A A A A A A De A De ce 4 4 1 pp pp gt 1 1 ao ao ao deed e De t bad de de det de de gll gll IF ol oa de de de de de
113. E random order To activate that seed click the Do It button SPECIFYING LAYER FILL You can select how the fill parameters are applied throughout the layers using the Layer Fill options Since the view is constrained to be one projected into two dimensions you must specify the actions that are to take place in the third pro jected dimension e You can apply parameters to This Layer only You specify the layer with the Graphics Control at the bottom Click the OGL Props tab then click the Orient tab Set the layer with the Slice bar which will reflect the number of lay ers in your structure If you established layer colors in the Layer Props Page they will be evident as you scroll through the layers You can apply parameters to All Layers which automatically loads the layer range of your structure into the edit fields This means the defined area will drill through all layers of the structure e You can apply parameters to a Range of layers which means the defined area will drill through a specified Range of layers Enter the range in the Lower and Upper Layer Range edit fields In this sense layers are actually the discretized sub element count not the actual layer number You must specify the properties themselves that apply the defined area in the Params Exchange Materials Media and BC Pages which follow READING AND SAVING POSITION DEPENDENT FILES Position dependent files are binary files that contain a huge amount of s
114. G parameters used in the calculation READING AND SAVING 3D CURRENT FILES When 3D currents have been specified you can save or read the computed current flow Since large sparse matrices take some time to solve once you solve for a 3D current flow you should reuse it The current flow is stored for a 1 microamp test current Internal to LLG the fields are computed for that test current and scaled by the appropriate con stant or time dependent current linearity SIMULATING MRAM BIAS AND WRITE FIELDS LLG includes a facility to add add time dependent MRAM fields In order to activate the MRAM tool you must use a time dependent current in this case the sense current When you specify a time dependent sense current the MRAM but ton will be enabled On the MRAM dialog shown below two field pulses can be selected a bias line pulse and a write line pulse These labels serve only to identify the field pulses and you can naturally use them as you please You can specify the direction and the magnitude Hx Hy Hz of each of the pulses and independently specify the rise use fall tran peak toeax end tena and turn on time to of each pulse relative to LLG s computation time and those natu rally specified for the sense current timing The temporal pulse shape is defined as H f t Hx Hy Hz where f t is 0 when t lt ton 1 exP tton trige 1 XP toeak ton trise when ton lt t lt tpe and 1 1 exp t toear traj 1 exp C
115. GE 1 Initiate an LLG calculation by clicking the New button on the Tool Bar to activate the Main Page 2 Enter the Simulation Volume with the slide bars or edit boxes 56 nm each for X nm Y nm and Z nm 3 In the adjacent discretization boxes enter 7 sub elements each for N Ny and N INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 Click the Globals tab 2 Select U Uniaxial in the Anisotropy Type group box The uniaxial anisotropy edit field K should be enabled and the cubic anisotropy K edit field should be disabled 3 Click the Material Selector button which activates the Materials Page 4 Select Permalloy from the Precoded Materials and Properties section which loads Permalloy s parameters into the database fields 5 Click Accept This closes the Materials Page returns you to the Globals Page loads the parameters for Permalloy into the edit fields in the Globals Page and records Permalloy after Properties Of 6 Click the Accept Changes button which exits you to the Main Page and loads Permalloy into the edit field at the top INPUT SHEET COMPUTATION PAGE 1 Click the Computation tab 2 Click the Energy Slower button Make sure that the Iterations and Convergence boxes are selected Be sure that the Convergence criteria is set to 0 0001 and that the number of Iterations is 25000 3 Click Accept Changes which exits you to the Main Page LLG Micromagnetics Simulator User Manual 26 201
116. GREEMENT IS THE COMPLETE AND EXCLUSIVE STATEMENT OF THE AGREEMENT BETWEEN YOU AND LICENSOR AND SUPERSEDES ANY PROPOSAL OR PRIOR AGREEMENT ORAL OR WRITTEN ANY OTHER COMMUNICATIONS BETWEEN YOU AND LICENSOR RELATING TO THE SUBJECT MATTER OF THIS AGREEMENT 1 18 LLG Micromagnetics Simulator User Manual Chapter1 License Agreement and Release Notes RELEASE NOTES Below is a history of LLG version 2 releases and the new features of each release Version 2 0 Released November 1 2000 with an Updated Manual V2 0 was a major upgrade that included an entirely rede signed graphical user interface faster calculating time and the following dozens of new features 1 Document interface Run multiple problems simultaneously e Runasimulation and a movie simultaneously 2 Graphics e Multiple OGL windows and views Multiple simultaneous perspective views e Input cells e Variable contours e Contour indicator e Material color codes e Variable color maps e Variable color wheels Variable 3D glyphs 3 Graphics representation e Current flow Position dependent external fields 4 Integrated electron phase 5 Utilities e Disk information e Clock Calculator Graphical picker Enhanced persistent graphical picker 6 Input configuration e Arbitrary number of material layers 7 Input parameters Fourth order uniaxial anisotropy 8 Boundary conditions e Continuous 2D is no longer a feature 9 Current
117. Get Imaging Mode View Options _ H 2 nm above surface Do Image dH dz z nm above surface 10 d2H dz2 z nm above surface Z nm Divergence of M Layer Demag Integrated B M Integrated Phase 0 0 Electron Trajectory gt Theta deg Phi deg FIGURE 101 Computed Imaging Mode View Options When you compute H dH dz d2H dz2 or Divergence M you must specify how far from the surface actually how far from the center of the top layer of cells to locate the scan For example 10nm converts to a scan height of 5nm above the surface since the cells are each 10 thick Once the image is computed the results are put in the TOP layer of cells in Z This means that if you have a 10 layer system in z you must select the topmost layer Nz 10 to see the view This is to simulate that it is a surface view To save the file once it is viewed actively click the Save To File button The file will have the suffix lg inputhfield The data for that scan will be in the layer of cells that corresponds to the top layer of cells In other words if you have a 10 layer system and the top layer is z 25 0 nm that layer will contain the data All other cells will have zero values There are four MFM contrast modes for visualizing what your MFM would measure if it scanned above a given micro magnetic structure LLG uses a rigid paradigm for rendering MFM images LLG assumes that the surface of the struc ture of interest
118. HYSTERESIS LOOP Often the magnetization does not undergo many changes while a hysteresis loop is being computed at field points away from the coercive field It can be more economical computationally to sample field points coarsely in regions where the magnetization does not change quickly and on a fine grid near any switching fields The non uniform hyster esis field provides this flexibility however you must input more complicated data The non uniform hysteresis field component divides the field into sections Each section is a linear interpolation of the field between its starting Limit 1 and ending Limit 2 field points You can specify the number of points independently within each section The first sec tion contains both the starting and ending field points for that section while subsequent sections join to the previous field section DESCRIPTION VARIABLE LIMITS Loop Direction x y z gt mi 10 lt m lt 1 0 Limit 1 Hx hys1 Hx hys1 1010 lt H wei 09 Hy hyst Hy hyst 1010 lt Hy hyst S 199 Hz hyst Hz hyst 1010 lt Hz hys1 lt 1010 Limit 2 Hy hys2 Hy hys2 1010 lt Hy hys2 lt 1010 Hy hys2 Hy hys2 1010 lt Hy hys2 lt 10 Hz hys2 Hz hys2 1010 lt Hz hys2 lt 1010 Hysteresis Points Nhys 3 S Nhys 16384 Field Section Specified Nsect 1 Nyegt lt 16384 LLG Micromagnetics Simulator User Manual 18 127 Chapter 18 Inputting Data Into LLG Hysteresis Non Uniform
119. IS LOOPS PAGE Movie Hysteresis Edit Movie n l Extract Hysteresis Loops D m Create Custom Hysteresis Loops Read Mask 1 ReadMask 2 Read Mask 3 Ei Save P save Z Save Save ToFile Projection Direction 1 000 0 000 0 000 Save Hys Field Dotted Into Projection Direction Extract average and projected magnetization from 3 different areas defined by the loaded masks Store result in llg hyspart file View file in 2D plot viewing tool FIGURE 121 Movie Player Sheet Extract Hysteresis Loops Page The Extract Hysteresis Loops Page is for extracting data from a movie file Unlike normal LLG simulation data hys teresis data that are extracted from a movie use direction cosines only that is the magnitude of the magnetization associated with each spin is NOT retained It IS retained for computing the hysteresis loops stored in the llg hys files and in the movie file in the hysteresis loop itself When you click the Hysteresis tab a mask view OGL window appears e You can load up to three masks with the Read Mask buttons from which the region of interest to extract three hys teresis loop can be specified Select the projection direction to specify that component of the field and magnetiza tion to write to the file Check the Save Hys Field Dotted Into Projection Direction box to save a particular field value to file If you do not then the original hysteresis fields will be writte
120. Input Sheet Main Page iia in oa 211 Input Sheet Globals Page Materials Page ooococonnccconncccnnccnnonacccononcnnnn cnn non cnn anna nn nn nn ran ranas 211 Input Sheet Initialize Page 211 Input Sheet Uniform Hysteresis Page nennen enters nennen anna inns sinn neret 212 Simulation Sheet Simulation Page nennen enne nennen nnns nnn EESE Ennn nennen 212 COMMENTS x stereo erii ie ida 212 mca cT 213 CHAPTER 30 Sample Problem 5 Non uniform Hysteresis Loop for a Platelet 215 Input Sheet Main Page innen ppt eanet uen pee Dti estin ten 215 Input Sheets Initialize Page irt de thee o ibo ertet earth ent 215 Input Sheet Non uniform Hysteresis Page eene ener enne en nennen intente nnne ren 215 Simulation Sheet Simulation Page AA 217 GOMIMEMIS str ee axe cte acabe heredi du et Mc LU E Ur weet LK iE bes EE 217 KO EEE lada ies 217 CHAPTER 31 Sample Problem 6 Simulation for Asymmetric Bloch Wall in Permalloy cuccnu 219 Input Sheet lt M in Page ete ect itt ose eth pha da Beate 219 Input Sheet Materials Page cacon cananea cerraran 219 Input Sheet Boundary Condttons eene sn trente aanne enn sistere 219 LLG Micromagnetics Simulator User Manual ix Table of Contents Input Sheet Computation Page 220 Input Sheet Initialize Page ii Uere ea e eere ed regenda PUn eats ene eer pee dieta D det TR lee 220 Gomirients cas Fre ed etre raden vest oe or ees dE dre senke bed deg daten EA E Sutera 2
121. LLG Drop down Menu and are standard Windows bitmap formatted files The contents of the OpenGL window can be captured and stored in a file for presentation or later use INPUT SPECIFICATIONS LLG_PARAM These ASCII files can be loaded and saved through the read and save Read Input Save v1 Input and Save v2 Input buttons in the LLG Main Input Sheet These are formatted files that can be edited with LLG s File Editor or a word pro cessor such as Microsoft s NotePad LLG Micromagnetics Simulator User Manual 4 31 Chapter 4 Loading Saving Files e Loading Data that has been loaded or saved in an lo param file in ASCII format can be reloaded at a later time These files contain the input specifications for all parameters including layers As such loading parameters from a file saves time in the input phase storing parameters to a file can save time by reusing them in the future e Saving If you have entered data through the LLG Input Sheet and its pages as opposed to loading a file it is highly recom mended that you specify a lg param file in which to store the ASCII start up file Save vi and Save v2 options dif ferentiate between v1 and v2 compatible input files V2 will read v1 files but version 1 will not read v2 files DIRECTION COSINES LLG DOM These files can be loaded and saved through the Angle Config button in the Main Input Page or through the Input File Name button in the Initialization Page These are ASCII f
122. LLG User Manual v2 50 Michael R Scheinfein and Elizabeth A Price LLG Micromagnetics Simulator 503 522 9317 Cellular 503 292 4686 Phone FAX lligmicroQmindsping com or Ilgmicroeap mindspring com Published by Michael R Scheinfein and Elizabeth A Price LLG Micromagnetics Simulator 503 522 9317 cellular 503 292 4686 Phone FAX IIgmicro mindspring com or llgmcroeapO mindspring com Copyright O 1997 2003 by Michael Scheinfein and Elizabeth Price All rights reserved No part of the contents of this manual may be reproduced or transmitted in any form or by any means without the express written permission of LLG Micromagnetics Simulator M You must accept the enclosed License Agreement before you can use this product This product is licensed for use onone computer LLG Micromagnetics Simulator is a registered trademark of Michael R Scheinfein Windows NT 4 0 Win2000 Win xP Visual C MFC Developer Studio and Fortran Powerstation are registered trade marks of Microsoft Corporation OpenGL is a registered trademark of Silicon Graphics OpenGL32 is Microsoft s 32 bit rendition of the Silicon Graphics code and is a registered trademark of Microsoft Corporation Portions Copy right C 1999 Bogdan Ledwig Cool Look Controls Hook and C 1999 Paul Barvinko starting code for 2D Graphics Thanks to JK Weiss of EmiSpec M Systems for a recursive splitter window routine Table of Contents DIST
123. Main Page Click the PosDep button on the Main Page Enter data with the Position Dependent Data Editor Click the Masks button on the Main Page Enter or load the mask through the Mask Editor H fr OTR 6 74 LLG Micromagnetics Simulator User Manual Chapter 6 Inputting Data Into LLG Main SF HysU ST HysNU TimeDepH v Shields Fields Current Layer Props Layer BCs Notes Batch Main Globals Materials Boundary Computation Initialize Ej CU R r Read x Files Save Input Files Read Input Save v1 Input Save v2 Input r Specify Output File Names Angle Config Convergence Movie i Movie Save Conv Details Every N Iterations 1 Simulation Volume X nm Tono B 56 0000 M 1 5000 Y nm 56 0000 7 Ny 1 5000 E ora aee ae 56 0000 7 Nz 1 5000 Commit Size Estimated Memory MB 4 r Greens Fnc p 2D Disc Structure Properties e 3D 2D E cube dnd Layers Pos Dep Atomic e r PET Fnc SH Lattice Val Overlay Editors Bosweg 2 Begin Simulation x Cancel Simulate Using A Movie FIGURE 34 Input Data Sheet Main Page VARIABLE LIMITS X nm 0 01 X 108 Y nm 0 01 Y 108 Z nm 0 01 Z 106 N number in X 1 N 108 Ny number in Y 1 Ny 108 N number in Z 1 N 106
124. Menu color coded to match graph colors 56 FIGURE 12 About LLG Dialog Box 1 2 ehh 57 FIGURE 13 EEGiFile Editof surr otra eee ee hate hie m ere iure me arises Ede ERE ah aie 57 FIGURE 44 LLG File Editor Toolbar a tows ER RE E rra EST 58 FIGURE 15 LLG Graphics and Utility Control Sheets 1 eee 58 FIGURE 16 OGL Property Sheet Modes Page o o ocococccon e 59 FIGURE 17 OGL Property Sheet Orient Page teen teens 62 FIGURE 18 OGL Property Sheet OGL Page teen een eens 63 FIGURE 19 OGL Property Sheet Color Page 1 nents 64 FIGURE 20 OGL Color Sheet Color Page 1k anaana aaa 65 FIGURE 21 OGL Color Sheet Wheel Page 66 FIGURE 22 OGL Color Sheet Table Page 6 eet eee 67 FIGURE 23 OGL Information Sheet Info Page 1 ett 68 FIGURE 24 OGL Information Sheet Disks Page ooccoccoccccoc ren 68 FIGURE 25 OGL Information Sheet Output Page 0 ren 69 FIGURE 26 OGL Information Sheet Clock Page oe tees 69 FIGURE 27 OGL Information Sheet Calc Page tte 70 FIGURE 28 OGL Information Sheet Demag Page 2 1 eee eee 70 FIGURE 29 OGL Selector Sheet Main Page 1 ett teens 71 FIGURE 30 OGL Selector Sheet Arrays Page ttt eee 71 FIGURE 31 OGL Selector Sheet Properties Page 6 tte 72 FIGURE 32 Utility tools sme asa diate chee rtt ditate mte od utei Lakes puts e dd pedi er mima 72 FIGURE 33 Input Data Strategy 73 FIGURE 34 Input Data Sheet Main Page 1 2 tee n 75 FIGURE
125. N 106 Media M Mom 0 Mgm 108 Media Thickness T nm Tm VET lt 10 Transition Width W nm Wm 0 X Wa lt 108 Transition Length L nm Lm 0 Lp 108 LLG Micromagnetics Simulator User Manual 20 137 Chapter 20 Inputting Data Into LLG Shields FIGURE 62 Input Data Sheet Shields Page 20 138 LLG Micromagnetics Simulator User Manual CHAPTER 21 Inputting Data into LLG Mask Editor The Input Sheet Mask Editor Page is where you shape the magnetic system by turning individual cells on and off Mask files are binary files that contain sequential integer fields with ones and zeros There are two masks The first mask contains information about which sub elements have non zero magnetization The second mask determines which sub elements will be used when the hysteresis or MR loop is visualized ACCESSING MASKS To access masks in LLG memory must be committed This means that the size of the problem can no longer be changed To commit memory check the Commit Size box on the Main Page Once memory has been committed you can access the Mask Editor Page by clicking the Masks button on the Main Page Once you have initiated the Mask Editor shown on the following page a new Mask View is loaded into the OGL window DEFINING A MASK SHAPE You define the mask using the mouse 1 Inthe Graphics Control set X Y or Z to establish the orientation projection of the layer or layers that you want to work with
126. N is 25 Ny is 1 and N is 3 Select Layers in the Structure Properties group box INPUT SHEET COMPUTATION PAGE These are identical to Problems 7 and 8 INPUT SHEET LAYER PROPERTIES PAGE 1 DUO 9v e Be Je 8 9 Click the Layer Props tab Enter 3 in the N Layers edit field Enter 1 in the Layer edit field Set the thickness of layer 1 to 10 0 in the Thickness T nm edit field Click the Material button Select Permalloy and click Accept Set the interlayer exchange coefficients A49 and A45 equal to 0 Click the LOAD LAYER PROP button to record your changes Enter 2 in the Layer edit field 10 Set the thickness of layer 2 to 10 0 in the Thickness T nm edit field 11 Click the Material button 12 Select Vacuum and click Accept LLG Micromagnetics Simulator User Manual 34 229 Chapter 34 Sample Problem 9 GMR for Bilinear Interlayer Exchange between Platelets 13 Set the resistivity Rho to 5 0 LOhm cm to approximate Cu mb 4 Set the interlayer exchange coefficients Ag and Ag3 equal to 0 Set the Bilinear exchange coupling coefficient to 0 16 uerg cm 4000e see Problem 7 15 Set the GMR value to 0 25 16 Press the LOAD LAYER PROP button to record your changes 17 Enter 3 in the Layer edit field 18 Set the thickness of layer 3 to 10 0 in the Thickness T nm edit field 19 Click the Material button 20 Select Permalloy and click Accept 21 Set the interlayer exchange coefficie
127. NS Once LLG has verified that you have input the data correctly you have your first chance to set the graphical represen tation of the data Many features can be viewed interactively LLG Micromagnetics Simulator User Manual 3 25 Chapter 3 Introduction to Using LLG REVIEW PHASE PLAYBACK OF RESULTS THROUGH A GRAPHICALLY ANIMATED MOVIE Once a simulation is complete you can review the results by replaying them through a graphically animated movie or you can view a domain or field file in the viewer control Graphical representation of the data is essential to compre hending the results of a simulation The program provides complete two and three dimensional views in the form of bit map images contour maps and vector fields THEORY OF OPERATION Micromagnetic structure such as that present in surface domain walls can be extracted with standard methods for the solution to the Landau Lifshitz Gilbert equation Such methods have been given in the literature by Brown 1 LaBonte 1 2 Aharoni 3 9 Hubert 10 11 and Schabes 9 12 The equilibrium magnetization configuration results from the minimization of the system s free energy The energy of a ferromagnetic system is composed of 1 the mean field exchange energy E between nearest neighbors characterized by the exchange coupling constant A erg cm 2 the magnetocrystalline anisotropy energy Ex which describes the interaction of the magnetic moments with the crystal fiel
128. New from the file drop down menu which activates the journal generator shown below Journal Directory Drive Selector de Directory Search Disk Search File Type Specification y Choose 153 OC wv lg param Lex win batch lg conv I8ilg movie Mg hys O 1lg_hysfield Choose Directories lg inputhfield Cancel FIGURE 6 Journal Viewer Journal Directory and Drive Selector SPECIFYING FILE TYPE You can select which file types to add to your journal by checking the appropriate box adjacent to the file type Above the selected file types include input llg param batch llg batch and domain llg dom files All LLG specific file types can be archived in a journal SEARCHING DISKS OR DIRECTORIES You can choose ONE of two possible search mechanisms 1 If you have specific directories that you want to generate journal files for check the Choose Directories box and use the Directory Search tool to add the directories to the list Above two directories have been added to the list There is no limit on the number of directories that you can add to the list 2 Alternatively you can select entire disk systems to scan for LLG files Above disks DA and JA have been selected The Journal Viewer scans your system for HARD DRIVES ONLY It will not scan CDs IOMEGA type drives or the network In other words LLG only scans your local hard drives for LLG files Once you have specified the file types and search paths
129. R ANY BUG ERROR OMISSION DEFECT DEFICIENCY OR NONCONFORMITY IN LLG AS A RESULT LLG IS SOLD AS IS AND THE PUR CHASER ASSUMES THE ENTIRE RISK AS TO ITS QUALITY AND PERFORMANCE WITH THE EXCEPTION THAT LICENSOR WARRANTS THAT LLG WILL PREFORM TO THE FUNCTIONALITY SPECIFICATIONS DOCUMENTED IN THIS MANUAL LICENSOR SHALL IN NO EVENT BE LIABLE FOR DIRECT INDIRECT SPECIAL INCIDENTAL CONTINGENT OR CONSEQUENTIAL DAMAGES RESULTING FROM ANY DEFECT IN LLG INCLUDING BUT WITHOUT LIMITATION TO DAMAGES FROM LOSS OF DATA DOWNTIME LOSS OF GOODWILL DAMAGE TO OR REPLACEMENT OF EQUIPMENT OR PROPERTY EVEN IF LICENSOR HAS BEEN ADVISED OF THE POSSI BILITY OF SUCH DAMAGES YOU AGREE THAT LICENSOR S LIABILITY ARISING OUT OF CONTRACT NEGLI GENCE STRICT LIABILITY IN TORT OR WARRANTY SHALL NOT EXCEED ANY AMOUNTS PAID BY YOU FOR THIS PRODUCT Any written or oral information or advice given by Licensor will in no way increase the scope of this warranty nor may you rely on such oral or written communication Some states do not allow the exclusion or limitation of implied warranties or liability for incidental or consequential damages so the above limitation or exclusion may not apply to you Changes Licensor reserves the right to modify or change LLG in whole or in part at any time prior to the delivery thereof in order to include therein any refinements deemed appropriate by Licensor and such refinements will not negatively affect LLG s ability to meet or exceed
130. R POSITION DEPENDENT PARAMETERS Enter Global data Check the Layers box under Structure Properties on the Main Page Enter layer data on the Layer Props Page see page 90 IMPORTANT NOTE FOR 1 LAYER POSITION DEPENDENT STRUCTURES Even if your structure has 1 layer to apply position dependent parameters you MUST first define the structure as 1 layer on the Layer Props Page In this case the layer thick ness defined on the Layer Props Page and the total thickness of the structure defined on the Main Page are equal Check the PosDep box not the button under Structure Properties on the Main Page Check the Commit Size box on the Main Page which allows you access to the Posi tion Dependent Parameter Sheet Once you commit memory the size of the prob lem can not be changed Click the PosDep button on the Main Page which activates the Position Dependent Parameter Editor shown on page 150 and loads a new Mask View into the OGL window LLG Micromagnetics Simulator User Manual 22 147 Chapter 22 Inputting Data Into LLG Position Dependent Parameters BASIS STEPS FOR ESTABLISHING POSITION DEPENDENT PARAMETERS For EACH area to which you want to apply position dependent parameters you must complete following steps Techni cally steps 1 through 3 can be completed in any order 1 2 3 4 Define the area of interest with the drawing tool Select a color for the area of interest from the Params Page to di
131. RE 82 FIGURE 83 FIGURE 84 FIGURE 85 FIGURE 86 FIGURE 87 FIGURE 88 FIGURE 89 FIGURE 90 FIGURE 91 1000 nm x 500 nm x 10 nm Permalloy Platelet Initialized with Vortex Random Magnetization Input Data Sheet Fields Page Input Data Sheet Current Page Input Data Sheet Current Mask Editor MRAM pulse Timing bias left and write right Input Data Sheet Layer Properties Page Input Data Sheet Layer Boundary Conditions Page Input Data Sheet Notes Page Input Data Sheet Hysteresis Uniform Page Hysteresis Loop Views for a Uniform linear Hysteresis Loop Hysteresis Loop Views for a Uniform rotational Hysteresis Loop Input Data Sheet Hysteresis Non uniform Page Non uniform Hysteresis Loop Example Hysteresis Loop View for a Non uniform Hysteresis Loop Input Data Sheet Time Dependent H Page FMR Page Input Data Sheet Shields Page Mask Editor Tool Bar Mask Editor Sheet Main Page Mask Editor Sheet Bitmap Page Mask Editor Sheet Edge Page Mask Editor Sheet Super Egg Super Egg Mask Editor Sheet Graphical Element Point Editor Position Dependent Parameter Editor Tool Bar Position Dependent Parameters Sheet Main Page Position Dependent Parameters Sheet Pop up Menus Position Dependent Parameters Sheet Parameters Page Position Dependent Parameters Sheet Exchange Page Position Dependent Parameters Sheet Materials Page Position Dependent Parameters Sheet Graph Page Position Dependent Parameters Sheet Media
132. S AS A FUNCTION OF TEMPERATURE USING FUNCTIONS LLG supports two different function inputs to generate temperature dependent data These functions scale as the nor malized temperature T T T F a 1 T Tc T T F a b T Tc c T Tc d T Tc T lt T When T gt T F 0 0 It is extremely important to note that this scaling will apply to all parameters in the array If you wish some parameters to remain temperature independent then simply set the Curie temperature of that site to a very high value 10x higher than the maximum temperature reached in the problem These function inputs allow you to set the magnetization as a function of temperature variably throughout the grid IMPORTANT NOTE 1 For example the magnetization in a 1 spin problem will be constructed from M T t x y z M4 x y 2 Fiy1 1 and in a 2 spin problem M T t x y Z My X y 2 Fy1 T Mo X y 2 Fy2 T IMPORTANT NOTE 2 The radius of convergence for a problem is fixed primarily by the exchange field which scales as A M If you want your problem to remain stable at all temperatures you must be sure that A gt 0 faster than M gt 0 at T gt 1 0 IMPORTANT NOTE 3 When specifying properties using functions all properties must be specified using functions i e you cannot mix functions and data options SPECIFYING PARAMETERS AS A FUNCTION OF TEMPERATURE USING DATA READ FROM FILES The second input option for parameters that LLG supports reads parameter data from a file Th
133. S ample _GS llg_param I Mllg v2 O work test S ample llg param I Mllg v2 O work test S ampleB llg param EH I Mllg v2 O work test S ample5 llg param I Mllg v2 O work test S ample4 llg param I Mllg v2 O work test test llq_param IE 4 FIGURE 115 Batch Mode Scripting Interface To generate an LLG batch file from existing llg param files use the list control at right to load named files into the list Once the list is complete click the Generate Batch button you will be prompted for a batch file name and location Files may be deleted reordered and cleared from the list The Clear All button clears the entire list 23 190 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation VARYING BATCH PROBLEMS AND SCRIPTING You can load a single problem and examine its contents for varying selected parameters Click the Read Seed File but ton in the Scripting Interface to load a selected parameter file The controls not shown above at left allow you to examine the contents of this file using the standard LLG input tools When you load a file the input controls are updated with the required parameters You can vary up to five parameters at a time using the scripting engine a nested loop five deep The parameters that can be modified are in black as opposed to dark grey check each one that you want to change In the Scripting Interface shown the magnetization and uniaxial anisotropy parameters have been selected
134. Samples 1 and 3 Set up your graphics windows as described in the prior two examples 30 216 LLG Micromagnetics Simulator User Manual Chapter 30 Sample Problem 5 Non uniform Hysteresis Loop for a Platelet SIMULATION SHEET SIMULATION PAGE The Simulation Sheet Simulation Page is activated and a top down view of your Permalloy platelet appears on the Screen 1 Select the Arrow Graph Type to see the surface magnetization on the platelet surface 2 Click the Views tab Right click on the OGL window and select Split Window Horizontally Left click on the upper pane of the OGL window view number 1 should appear at the top of the Views Page after Active View Then click Hysteresis Loop Your loop axes should be visible on top 3 Click the Start To Compute button which initiates LLG to relax the magnetization The meter tracks the simulation s progress as a percentage of the number of hysteresis loop points and updates the iteration count The domain pat tern will change as the field is swept and the hysteresis loop is updated 4 Click the Selector tab at the bottom of the screen and then click the Arrays tab Click the Activate Picker box then click on a point in the polar hysteresis loop The point s values appear in the fields COMMENTS Notice the higher field density local to the coercive field in the hysteresis loop FEATURES Structure 250 nm x 100 nm x 10 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 2
135. Secs 5mSecs m Progress Status Indicators Iterations 5 2060 0 Es Simulation Time ps Residual Update E ergs Total Energy 2 162445e 010 Internal Energy 1 879613e 010 Exchange Energy 5 648434e 011 Anisotropy Energy 6 513917e 014 Stray Field Energy 1 314118e 010 External Field Energy 2 828328e 011 r Progress Hysteresis Indicators Hysteresis Loop Gof 21 29 96 M Hys H x y z M 0 773 0 000 0 000 Rem 0 773 H 260 00 0 00 0 00 lt Hys 260 00 H 0 00 0 00 0 00 Static Hext Status Pausinq Close All Graphics Active Onl FIGURE 84 Simulation Sheet Simulation Page 23 166 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation VIEWS PAGE Main Views Movies Notes Comp Fields B Probe de Simulation View Options Active View ma Standard View Options Mx My andMg lt log FFT C Residuals Ich ite s Effective Field Magnitude Demag Field Energy Density Save To File m Optional View Options Boundary Cond Field Temp K Gurrent Induced Field Current Pas Dep Ext Field 7 PosDep Shielded Ext Field Se View Polar Hysteresis Loop MR Loop View dh m Computed View Options B Field Induction Gyromagnetic Torque C Damping Torque _ Total Torque Heff dm dt Dissipation r Computed Imaging Mode View Options H z nm above surface _Do
136. Simulation Volume to 250 nm for X nm 100 nm for Y nm and 10 nm for Z nm In the adjacent discretization boxes enter 25 sub elements for N 10 for N 1 and for N INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Click the Uniform X Direction button in the 3D Uniform Magnetization field 3 The Sign On Uniform options default to Positive with Theta 90 0 magnetization in the X Z plane and Phi 0 0 magnetization along the X axis Enter 10 0 into the Phi edit field to cant the initial magnetization off the X axis by 10 Close this page by clicking Accept Changes INPUT SHEET NON UNIFORM HYSTERESIS PAGE 1 Click the Hys NU tab 2 Click the Non Uniform box to enable the section and to accept a non uniform hysteresis loop Then you must specify an arbitrary yet non uniform hysteresis loop Then design a field loop for a system where the coercive field is around 375 Oe 3 The Field Section Specified edit box should read 1 the first field section Enter 750 0 in the Limit 1 edit field for Hx Leave Hy and Hz set to zero This is the initial field point for the first hysteresis field section 4 Enter 300 0 in the Limit 2 edit field for Hx Leave Hy and Hz set to zero This is the final field point for the first hys teresis field section and subsequently the initial field point for section 2 should you select another field section 5 Enter 10 in the Number Of Field Points edit box This will interpolate 10 intervals
137. TERIALS PAGE 1 Select Permalloy in the Materials Page 2 Click Accept the Permalloy properties should be entered in the edit fields of the Globals Page 3 Click Accept Changes to log your changes INPUT SHEET MASK AND VIEW PAGE 1 Check the Commit Size box on the Main Page This commits the memory fixes the sample size and allows you to use the Mask Editor 2 Click the Masks button on the Main Page The Mask Editor and View Page appear Your initial view of the struc ture will be from the top All of the sub elements will be painted yellow indicating that the magnetization is active within each cell 3 Use the drawing tool to form the element into the same shape as the one above and on the following page Active cells appear yellow and removed cells appear blue Save your mask once you have completed forming the struc ture You can import a given mask into a new problem which LLG will interpolate if the meshes are different LLG Micromagnetics Simulator User Manual 37 239 Chapter 37 Sample Problem 12 Shaping Magnetic Elements 4 Click Accept Changes and return to the Main Page 5 Click Begin Simulation and run the problem FIGURE 138 View of Mask COMMENTS Observe how the magnetization runs parallel nearly parallel to the edges defined by the mask which is consistent with minimizing the stray field energy FEATURES Structure 750 nm x 500 nm x 10 nm Sub Element 10 nm x 10 nm x 10 nm Discretization
138. This activates the drawing tool and the Drawing Tool Bar will be visible The default color of the drawing pen is Red You can change the color to Black Green or Blue You can adjust the size of the pen as well cooo m MEE v une FIGURE 63 Mask Editor Tool Bar 2 Choosethe type of shape that you wish to draw The default is a rectangle 3 Use the mouse to draw the shape Its position in nm will be output to the OGL window frame at bottom right Forthe rectangle circle and ellipse left click with the mouse to choose the starting position and continue to hold down the mouse Dragging the mouse outlines the shape under construction Release the mouse button at the final point to mark out the shape Forthe polygon you must left click for each point that you wish to define and double click to close the polygon The arbitrary line allows you to draw a wavy line and enclose any shape that you choose to define Click the CLR button to clear all defined shapes LLG Micromagnetics Simulator User Manual 21 139 Chapter 21 Inputting Data Into LLG Mask Editor MASK EDITOR SHEET MAIN PAGE Main Bitmap Edge Super Egg pa Mask Editor r Fill Mask Region r Mask Properties e Toggle Cells C Tum Cells On Turn Cells Off r Random Fill 3 e Uniform Fill t Random Fill Fraction 0 5 Layer Fill e This Layer AMI Layers Range Layer Range Lower Upper
139. U Page enne enn nnn nnns sen renh nsn teen tres et nns snnt rens nennen 230 Simulation Sheet Simulation Page senes nenne nr ran ra Ennen nnne 230 Comments 3 20 29 gh tefle etii t utr Yao i ha dodo sia ate COBRE Rd URN eed coder FAG AERE Trag ccv Son vh Ee 230 FOatures x 230 CHAPTER 35 Sample Problem 10 Boundary Conditions Applied to a Thin Platelet 233 Input Sheet Main Pages avai Keane daa 233 Input Sheet Computation Page 233 Input Sheet Globals Page and Materials Page sss ener nennen nennen nnne 233 Input Sheet Boundary Conditions Page 233 Input Sheet lnitialize Page auraen id gel ye etx ede e ae av dE e da 234 El 235 Features na nd til dU dte Det e RD de Bill alee Fe SEED de d epo eid edie 235 CHAPTER 36 Sample Problem 11 Non uniform Hysteresis Loop for a Pinned Platelet 237 Input Sheet External Pinning Fields 237 COMMONS 5 eet inire teca idad entret taes en daba ag ccn sut aut Ee 237 A A 238 X LLG Micromagnetics Simulator User Manual Table of Contents CHAPTER 37 Sample Problem 12 Shaping Magnetic Elements rrrrrnnnuunnnnnnnnnnnnnnnnnnnnnnnnnnnnnnen 239 Input Sheet Main Page E 239 ll eene Ee Be EE 239 Input Sheet Materials Page nennen nnne en tens nn trns entres sinn nnna nana 239 Input Sheet Mask and View Page cesses eenaa aiaa aana aaea aan anaia aa EAEan nE raina aa aa aa 239 EIERE T A deeg A AT 240 SEI 240 CHAPTER 38 Sample Problem 13 Bulk Terminated Bloch Wall
140. Z Mask Save An Ascii File Click the Pos Dep Views button to activate the pop up menu above Each parameter can be visualized including those specified in the Parameter and Exchange Pages The Input Cell Position is required for editing so always return to this view to edit the cells or to specify a shape FIGURE 71 Position Dependent Parameters Sheet Main Page Move Selected Region Delete Selected Region Edit Selected Region Coordinates Save Selected Region Fill Selected Region Sample Selected Region Histogram Review Edge Region Coordinates Specify Selected Region For Edge Property Effects Specify Selected Region For Demag Edge Calculation Delete The Region Specified For Demag Edge Calculation Review Demag Edge Calculation Region Coordinates In Mask Editor right click on the active graphic for these options which can be performed on existing graphics Rectangle Polygon Circle Ellipse Curve Clear All Regions Load Region From File Black Red Green Blue Pen Width In Mask Editor right click on the background of the window for these options which are for creating or loading new graphics FIGURE 72 Position Dependent Parameters Sheet Pop up Menus 22 150 LLG Micromagnetics Simulator User Manual Chapter 22 Inputting Data Into LLG Position Dependent Parameters Once you have defined an area of interest you can apply additional fill and
141. Z 100 READ UNIT ANG_X LJ K ANG_Y LJ K ANG_Z LJ K 200 CONTINUE 4 40 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files Direction Cosines llg dom Type LLG Domain File Format Formatted ASCII Where Input Dialog and Saving Dialogs Throughout Prompt Read Input Angle Configuration Write Input Angle Configuration Suffix lg dom Variables NX number along x direction NY number along y direction NZ number along z direction ANG X magnetization direction cosine along x direction ANG Y magnetization direction cosine along y direction ANG_Z magnetization direction cosine along z direction II dummy index in x for file visualization assistance JJ dummy index in y for file visualization assistance KK dummy index in z for file visualization assistance READ UNIT DNX NY NZ 1 FORMAT Q3D DO 100 I 1 NX DO 100 J 1 NY DO 100 K 1 NZ 100 READ UNIT 2 IL JJ KK ANG_X LJ K ANG_Y LJ K ANG_Z LJ K 2 FORMAT 3i3 3E15 7 Magnetization Masks llg mask Type LLG Mask File Format Unformatted BINARY Where View Mask Input Graphics Dialog Prompt Save Mask Read Mask Hysteresis or Regular Mask Suffix lg mask Variables NX integer number along x direction NY integer number along y direction NZ integer number along z direction READ UNIT NX NY NZ DO 100 I 1 NX DO 100 J 1 NY DO 100 K 1 NZ 100 READ UNIT PICKER 1 J K or HYSTPICKER LJ K LLG Micromagnetics Simulator User Manual 4 41
142. _strBuffer1 Format 15e 15e 15e 15e 15e 15e m_pLLG gt m_pX m_nOffset m pLLG m pY m nOffset m pLLG m pZ m nOffset pX m nOffset pY m nOffset pZ m nOffset m fileStdio WriteString m strBuffer1 n 0 m fileStdio Close 4 44 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files return TRUE Hysteresis Field Files t_BOOL CDatalO WriteHysFieldFile2_01 t_pChar pFileName t_BOOL bAllocate Open File if m_fileStdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate amp m fileException FileExceptionHandler amp m fileException return FALSE Write Header String m fileStdio WriteString m strVersion n0 m strBuffer1 Format 4i m pLLG m nHysHpts m fileStdio WriteString m strBuffert WN0 for t Inti 0 i lt m pLLG m nHysHpts i m strBuffer1 Format 9610 219610 219610 2f m pLLG m dHysHLoop O i m pLLG m dHysHLoop 1 i m pLLG m dHysHLoop 2 i m strBuffer1 m strBuffer1 m fileStdio WriteString m strBuffer1 n 0 m fileStdio Close return TRUE Current Files t BOOL CDatalO WriteCurFile2 01 t pChar pFileName t BOOL bAllocate Open File if m_fileStdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate amp m_fileException FileExceptionHandler amp m_fileException return FALSE Write Header String m fileStdio WriteString m strVersion n0 m str
143. a Fie Names Save Ange Coig Commomee Move Y Save Corre Delos Every N lierabore Coment Size Keimaed Memory MB Greene Fre 20 Disc wD 2 Greens Fre Type Lattice 7 Alc E Dve 30 Diech Age Coe Otho T wee Coment doa BH L TENE Postion Postion Postion Auve View 1 Ej mus Memory Load Pct 28 Avalatle Memory MB 387 9 intro LLG a Hilask Capture ZAH PRO UG Miciemagnetics L R nw For Help press F1 Start n cod 0 2 02 Ay Exploring New Figs FIGURE 8 LLG Environment MAIN WINDOW TOOL BAR BBR 9 V aE FIGURE 9 LLG Main Window Tool Bar The functions of the tool bar icons moving from left to right are 1 New Simulation 2 View Screen 3 Movie Screen 4 2D Graphics 5 Print OGL Window 6 About LLG 7 Help 8 Editor 9 Save OGL Bitmap and 10 Save OGL Bitmap to the Clipboard 1 The New button clears the screen and enables you to start a new simulation The name of the file in use appears in the window workbook tab If you are working with an unnamed file the program names the files Init LLG and defaults to these names in the Save function 2 The View Screen button activates the file viewer where you can visualize domain field and mask files individually 3 The Movie Screen button see page 195 activates the movie viewer where you can visualize movie files and ani mation sequences 5 54 LLG Micromagnetics Simulator User Manual Chapt
144. ab under OGL Properties Sheet Select the Arrow Graph Type to see the surface magnetization on the platelet VIEWING THE HYSTERESIS LOOP 1 Right click on the OGL window and select Split Window Horizontally 2 Decrease the size of the top half of the window by sliding the splitter window bar upward 3 Click the Views tab to reveal the view menu options 4 Left click on the upper pane of the OGL window view number 1 should appear at the top of the Views Page after Active View Then click Hysteresis Loop on the Views Page Your loop axes should be visible on top 5 Right click on the lower window pane and select Split Window Vertically Left click on the lower right window view number 3 should appear at the top of the Views Page after Active View 6 Click the Bitmap button in the OGL Props Sheet Modes Page You should have a bitmap view at bottom right an arrow view at bottom left and a hysteresis view at the top You can change the view options and the graphical representation of your data in each window To remove a view right click on the pane and select Delete Active View Start the LLG computation by clicking the Start To Compute button The meter tracks the simulation s progress as a percentage of the number of hysteresis loop points and updates the iteration count The domain pattern changes as the field is swept and the hysteresis loop is updated If you pause the computation you can determine the numerical valu
145. able above you are less likely to make the error of exiting the parameter setup without accepting your Global Parameter input because you are automatically returned to that Page step 4 left instead of the Main Page step 3 right after using the Materials Database Once you have entered data into the Globals Page you MUST click the Accept Changes button for your changes to update the LLG data structures If you do not you will lose your changes when you leave this property page At any time you can click the Main Control button to return to the Main Page but remember to Accept Changes before exit ing if you want your changes to take effect CONVENTION FOR ANISOTROPY When the anisotropy coefficients are positive the internal energy due to anisotropy will always be positive The Uniax ial energy density is written as Ey Kyo 1 m a Kua 1 m a where a is a unit vector along the easy direction The surface anisotropy is taken as E 1 2K m n where n is the outward facing unit normal vector Thus positive K has the effect of forcing moments back into the surface in this convention The interface anisotropy in the Layer Page has the similar form E 21 2K m m The interface effective field is simply K m which favors out of plane magnetization when K 0 This is the convention in LLG GLOBAL SPIN TORQUES Facilities to compute spin torque in non layered systems has been added in v2 50 see Currents Chapter Whenever there is a d
146. activates the Materials Page 4 Select Permalloy from the Precoded Materials and Properties section which loads Permalloy s parameters into the database fields 5 Click Accept This returns you to the Globals Page loads the parameters for Permalloy into the edit fields in the Globals Page and records Permalloy after Properties of 6 Click the Accept Changes button which exits you to the Main Page and loads Permalloy into the edit field at the top INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Click the Uniform X Direction 3 Enter 10 0 into the Phi edit field to cant the initial magnetization off the X axis by 10 4 Click Accept Changes LLG Micromagnetics Simulator User Manual 29 211 Chapter 29 Sample Problem 4 Rotational Hysteresis Loop for a Magnetic Platelet INPUT SHEET UNIFORM HYSTERESIS PAGE 1 2 Click the Hys U tab Click the Uniform and Rotational boxes to accept a rotational hysteresis loop and click the X Y Rotation Plane button to select the plane of field rotation to be in the plane of the platelet Then using the slide bar or the edit box set the field in the X direction H Oe in the Maximum External Field sec tion to 300 Oe Use the slide bar or edit box to set the Points to 37 This ensures that the rotation field magnetization will be com puted in ten degree increments including 0 and 360 The field values will be displayed in the OpenGL window Refer to
147. adapter 18 GB hard drive for data and a 4 mm DAT tape backup are recommended Fast SCSI controllers are good for accessing disk files quickly A high end fast OpenGL video card such as 3D LABS Oxygen video card 32 MB RAM and a Glint chip A 21 monitor such as the View Sonic 810 which supports resolutions up to 1600x1200 at 70Hz LLG Micromagnetics Simulator User Manual 2 21 Chapter 2 Getting Started MEMORY REQUIREMENTS OF LLG CALCULATIONS LLG will have the following approximate memory requirements The numbers in the table below are based on a Per malloy structure with 10 nm cubic cells Approximate Structure Size Pixilation Pixels Layers Position Dependent 500 nm x 500 nm x 50 nm 50x50 x5 12500 23 MB 27 MB 1000 nm x 1000 nmx 50nm 1100 x 100 x5 150000 82 MB 95 MB 2000 nm x 2000 nm x 50nm 200 x 200 x5 20000 315 MB 369 MB 4000 nm x 40000 nm x 50 nm 1400 x 400 x 5 80000 1245 MB 1461 MB INSTALLING LLG MICROMAGNETICS SIMULATOR e Log onto your system as the Administrator e Use the control panel to open the display control Set your display settings to 1280 x 1024 16 7 million colors Set the fonts to small fonts e nsert the CD ROM e From Explorer open the CD ROM and double click on Setup exe This activates InstallShield which automatically sets up LLG e You will be prompted to enter a Serial Number Since the installation is not protected you may enter anything you
148. advanced button Now choose the Trouble shooting page Turn off hardware acceleration Try LLG which should now display the graphics Now iterate on the above process gradually increasing the acceleration to an optimized setting where LLG graphics are still displayed INSTALLING LLG iN KANJI AND HANGUL ENVIRONMENTS To install LLG in kanji and hangul environments you might need to move a copy of msvcrt dll from the LLG directory into your system32 folder Please send any questions to IlIgmicro mindspring com LLG Micromagnetics Simulator User Manual 2 23 CHAPTER 3 INTRODUCTION TO UsiNG LLG This section provides you with an overview of LLG s design of how to use LLG and of LLG s functionality For complete details and instructions refer to the appropriate sections found later in the Manual THREE MODULES OF FUNCTIONALITY LLG Micromagnetics Simulator has three functional modules These modules are specified in terms of the serial pro cess of defining the solutions to most problems while maintaining consistency with the Windows event driven pro gramming interface These modules are listed below with their corresponding menus e Input phase data specification LLG Input Sheet e Simulation phase solution of the differential equations LLG Simulation Sheet e Review phase playback of results through graphical animation movies LLG Movie Viewer INPUT PHASE DATA SPECIFICATION The LLG Input Sheet is the central interfa
149. al transition region to occupy 20 Narrow or 100 Wide of the entire width of the discretized region FIGURE 44 Two dimensional 10 nm x 40 nm Permalloy Domain Wall Narrow Initialization 11 100 LLG Micromagnetics Simulator User Manual Chapter 11 Inputting Data Into LLG Initialization EELER LKE SRA RA RARA A ARA RAR ARA Ax am CR re AA A AMO DEEL KEE tres ERR RK THAR KAR Ax zz bs ES RRRA LAKE EE HEA At XN ES SRCETANKARRR KRACK RARE SA pb PRR RO RRR AER RR REREAD REM ERK POW RRR EELER RRA AR RKRA TERR KR BRERA AAA t EAE di de dk EE CECE 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 VG omm m t pomo m dm 7 4 47 t Leescht NEE 4 4 fee OOO dr om 4 4 47 t Mc ll 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 1 nl n 4 4 4 4 4 4 4 4 4 4 4 T il le le ol 4 4 4 4 4 4 4 4 4 t le le eee e ee T ll eee e 4 4 4 T ll i i o eee ce ee A ot st m m n lt e e e tt 4 tt tt w e TI 4 4 4 4 4 f 11 101 LEE CECR EZE BK RRR HR RR RA te AAT II E a RARER R PASSE BS KERK TERA ROS LEE ELE EN RARA ORAR RRA RAR RRR RH KARR SEERA R mk n RRR AR EE ERR PARA RAE RARER ERRARA ARK tx b RN mann E Een tat ER nn ER nb zb Esstsnz ts ft RN ERR R SRRRR AMARA RA EE HE EET JE DE ERR E ENER EE ER Trane PAP Awami SAA ARA PEARS AAA MEAP AL AAA PP AAAS LL aaa
150. allel algorithms If that does not work stop and refine your grid Since the Save button was checked on the Main Page the convergence output file for this example includes a com plete iteration history FEATURES Structure 56 nm x 56 nm x 56nm Sub Element 8 nmx8 nm x 8 nm Discretization 7x7x7 Material Permalloy Relaxation 1 Pt Energy Minimization Initialization Vortex in Z Plane FIGURE 123 Surface Magnetization Effective Field in 3D Arrows and Change Pattern in 3D Arrows LLG Micromagnetics Simulator User Manual 26 203 Chapter 26 Sample Problem 1 Basic Data Input for an Fe Cube FIGURE 124 Demagnetization Field Pattern in 3D Arrows 26 204 LLG Micromagnetics Simulator User Manual CHAPTER 27 Sample Problem 2 Basic Data Input for a Soft Magnetic Cube This problem is a continuation of Sample Problem 1 It presents results for a single material with no boundary condi tions external fields or sources of any kind This sample problem can be initiated by entering the size and discretization of the structure in the Input Sheet Main Page For all other features run this example exactly as Sample 1 except set the magnetization in the Globals Page to 400 emu cm COMMENTS Since the Save button was checked on the Main Page the convergence output file for this example includes a com plete iteration history FEATURES Structure 56 nm x 56 nm x 56 nm Sub Element 8 nm x 8 nm x 8 nm Discr
151. ameters specified check the Mag Edge box To scale the exchange parameters with the functional parameters specified check the Exch Edge box Internal to LLG the function that you specify is used to scale the existing magnetization and or exchange parameter values Check the Fix Torque box if you want to keep the ratio of A M constant Set the distance from the edge of the structure in the Edge Distance edit field Draw an edge in the graphic using the Drawing Tool This feature cannot be used with an imported graphic Right click the graphic and select Specify Selection Region for Edge Property Effects from the pop up menu Ne oe Use the Picker Tool see page 71 to identify the change in properties along the edge Example 1 Draw a square to define an edge 2 On the Main Page check Set Params and either Internal or External Fill Region depending on whether you want to scale the edge internally or externally to the graphic On the Edge Page check the Mag Edge box Set A 1 B 2 0 4 C 0 and D 0 Click the Plot button Set the Edge Distance to 50nm Right click the window and select Specify This Shape for Edge Property Effects Right click the graphic and select Fill Selected Region eo Dm P Oo SPECIFYING EDGE ROUGHNESS To specify periodic Edge Roughness 1 Specify which layers you want to mask on the Mask Editor Main Page and whether you want to turn on or turn off the region internal or external Define a region
152. ample selecting X displays the slice where X constant Position nm eon AAA Nea Cun eee nn dets X 0 Y 0 Z 0 Phi Slice Rendering Properties 068 oO le Filed Lines ME Modes zE Orient oa FIGURE 17 OGL Property Sheet Orient Page e Rendering Properties You can visualize solid figures including Bitmap and Domain Graph Types with the Filled surfaces and outLines 5 62 LLG Micromagnetics Simulator User Manual Chapter 5 LLG Environment OGL PROP SHEET OGL PAGE The OGL Modes Prop Sheet OGL Page is where the OpenGL properties can be altered and set directly Length With this you can set the length of the arrow or cone 0 75 is the default Radius With this you can set the radius of the arrow or cone 0 25 is the default Sides With this you can set the number of cone sides 12 is the default More sides take longer to draw Arrow Steps It is difficult if not impossible to see detail when you display all moments for systems that have thousands of sub elements in each plane To simplify the view you can display every other arrow by entering 2 into the Arrow Steps edit box to display every third arrow use 3 etc All of the data remain unchanged However an uncluttered view of the vector field simplifies interpretation of order in entire structures of Contours With this you can set the number of contours 20 is the default Size With
153. an examine exactly how energies are traded as they are minimized Remember that the ultimate integrity of an LLG solution is defined by its total energy the best solutions have the lowest energies for identical starting condition etc The number of Iterations Simulation Time and CPU Time are indicated after each computational cycle The dis tinction between Elapsed Time and CPU Time is seen when the system has more than one processor In such a situation the CPU time will be greater than the elapsed time e When hysteresis loops are generated the Progress Hysteresis Indicators chart progress The number of field points completed as well as the remanence at each cycle is displayed to mark the calculation s progress e At lower left in the Simulation Page shown on the following page the status of the computation and the graphics are always indicated The Red and Green lights on the buttons can be used to indicate the calculation s state e To evaluate the energy of a given configuration click the Update E button This computes the energy without tak ing a time step LLG Micromagnetics Simulator User Manual 23 165 Chapter 23 Simulation SIMULATION PAGE Main Views Movies Notes Comp Fields B Probe 5 Elapsed Time CPUTime Iteration Time r Time Status Indicators LLG Simulation Control E Tum Graphics Off ZN O Days O Hours O Mins 12 Secs 0 Days O Hours O Mins 6 Secs O Mins O
154. and switching behavior of your system or of the magnetic microstructure within it use the Boundary Condition H field visualization tool to correlate the effect of the field with the resulting equilibrium magnetization CURRENT INDUCED FIELD You can visualize the vector field whose projections are the normalized Current Induced H field vectors along the three Cartesian axes Use this View Option to visualize the field due to currents alone Since currents are often used to bias the magnetization in MR heads this allows you the flexibility of imaging that component of the magnetic field sep arately FIGURE 94 Current Induced Field Arrows POSITION DEPENDENT EXTERNAL FIELD You can visualize the Position Dependent External Field when it is defined SHIELDED EXTERNAL FIELD You can visualize the Shielded External Field when shields are specified and the loop is shielded HYSTERESIS LOOP AND MR Loop There are two additional View Options for visualizing MR and hysteresis loops An MR Loop is displayed for LLG problems that have finite currents and non zero AMR or GMR ratios The MR Loop option allows you to toggle 23 172 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation between viewing the resistance R the default and the normalized differential resistance dR R MR loop The text on the button reflects the current state of the viewing tool A polar hysteresis loop is displayed for LLG problems with rotational hyste
155. and 0 00 for the Loop Direction lt x y z gt for the projection axis for the hysteresis loop display Since there is only an X component the magnetization is dotted into a unit vector along X for the hysteresis display 5 Click Accept Changes to complete the hysteresis specification 6 Click Begin Simulation SAVING FILES If you have not saved the new input parameters LLG will prompt you to do so If you respond yes you will be prompted a second time to name the input file llg param By default the program will create three more files a domain file with the direction cosines on output llg dom a con vergence file with iteration histories and energy values llg conv and a hysteresis output file llg hys with the magnetization directions and field directions recorded at every field point Each file will use the prefix of your lg param filename If you select NOT to save the input parameter file LLG will prompt you to enter lg dom lg conv and lo hys filenames If you select NOT to enter filenames LLG automatically creates and names the three files in your running default directory untiitled llg dom untitled llg conv and untitled llg hys Once files have been specified a progress meter at the bottom left tracks the computation of the demagnetization field coupling tensor SIMULATION SHEET AND OGL PROPERTIES SHEET Then the Simulation Sheet appears along with a top down view of your Permalloy platelet Select the Modes t
156. ane of those two vectors This method is similar to solving the LLG equation in the limit of infinity damping parameter CL since solutions take the form of torque 0 at equilibrium Aligning M to H forces the plane of rotation to include M and H since there is no gyromagnetic precession term Once you have rotated the vectors the angles are normalized Advantages Ws m Relaxation Method JI HysU A HysNU AL TimeDepH w Shields Fields Current Layer Props Layer BCs Notes Main Globals Materials Boundary Computation Initialize Energy Slower Time Faster ba Energy SOR AX Time Integration NEEN s Predictor Corrector O 4 e Rotation Matrices O 2 1 0 111 20 Euler 0 1 Energy Search Gauss Seidel Stable DI Ce Sequential EET Method Randam e 2DReal 3D Complex M Computation Parameters mM Time Step ps Iw Use Dual Processors 100 ol iv Convergence 1 000e 004 Max N A IV terations max 25000 PESTEN Iterations min 1 Q Max M s Max T E AT 2 H AveM Ave T ET r Exchange Cor be NumberRHS VHT interpolate Y Gamma MHz 17 600 7 00000 nm v Alpha 1 000 LA Start t ns 0000 Accept Changes Stop t ns 1 000 Temp TK 2000 X Reject Changes AN Seed 0 A i FIGURE 39 Input Data Sheet Computation Page There are two advantages to this method First the
157. ange field rather than the exchange coupling parameter calculate the exchange bias see below Use the bilinear and biquadratic coupling coefficients only to couple films across a non magnetic layer which has Mg 0 For example the edit boxes are disabled if you specify a three layer system with a central magnetic layer There are many paradigms for specifying the coupling across non magnetic layers In LLG the topmost sheet of sub elements in the layer below the non magnetic layer couples to the bottommost sheet of sub elements in the layer above the non magnetic layer Since the exchange field sub element discretization and exchange coupling parame ters are related in LLG an independent assignment of the exchange field and the exchange parameter is impossible In LLG the fundamental exchange parameter is A rather than the exchange field The exchange parameter couples adja cent sub elements using a finite difference second derivative to determine the exchange field Sub elements within lay ers are strongly exchange coupled while sub elements across non magnetic spacer layers are typically weakly coupled Bilinear or biquadratic exchange between sub elements forces the coupling between the layers With this LLG convention the bilinear and biquadratic coupling energy density is A in s ug E JAbitinear a mj Byiquaraticr 1 mj m dv where Abilinear is the bilinear coupling coefficient Byiquadratic iS the biquadratic coupling
158. ape using the position dependent editing tools 5 specifying either a single layer all layers or a range of layers from the LLG Main Position Dependent Param eters Page and 6 by right clicking on the defined shape and selecting fill region You may repeat this process as many times as you choose to Remember to save your position parameters IMPORTANT NOTE Your custom version of LLG Micromagnetics Simulator saves position dependent files in a different format than the regular version of LLG The custom version saves in addition to the normal position dependent parameters the position dependent magneti zation of both spin systems the gyromagnetic frequencies and damping parameters as well as the local Curie temper ature LLG uses the same file suffix to specify these files If you attempt to read a position dependent file saved with the normal version of LLG with the customized version the file read will fail since the added arrays are not written to the file Please keep your files written with the customized LLG in a separate directory from those written with the normal version of LLG Remember load your files before you begin to specify your problem and be sure to save your position dependent data prior to beginning a simulation SPECIFYING PARAMETERS AS A FUNCTION OF TEMPERATURE You have two options for specifying MO properties as a function of temperature either using defined functions or read ing data from a file SPECIFYING PARAMETER
159. appropriate edit fields Once you have selected a material its name appears in the Global Page following Properties Of CREATING A MATERIALS DATABASE You can use the Materials Page for saving material properties that you have input yourself To create a database 1 Enter the material s property values and the name of the material in the edit boxes 2 Click the Load into Data List button to register the material in the drop down menu 3 To store the database to a file for permanent archival click the Save Database button and name the file LLG Micromagnetics Simulator User Manual 8 83 Chapter 8 Inputting Data Into LLG Materials EF HyeU SF HysNU TimeDepH w Shields Fields Current Layer Props Layer BCs Notes Main Globals Materials Boundary mener Initialize n PreCoded a and Properties Zb Fei e Permalloy Vacuum m Enter Material into Database 800 Ms emu cm 3 1000 Ku2 erg cm 3 105 A uerg cm 0 Kud erg cm 3 15 Rho u ohm cm 0 Ke erg cm 3 0 02 AMR Ratio Ks erg cm 2 ares e Uniaxial Cubic Uniaxial and Cubic Permalloy Material or Identifying Title Load into Data List Open Database Save Database Delete Item Delete All Accept z X Reject FIGURE 37 Input Data Sheet Materials Page LOADING A PREVIOUSLY SAVED MATERIALS DATABASE FILE e To load a previously saved database file click the Open Database bu
160. ating magnetization typically choose 3 or 4 periods as the minimum Also please note that there are only 1000 points in the susceptibility arrays so 1 f x time step 1000 LLG will warn you if you exceed the memory limit Internally LLG computes the entire matrix of the sus ceptibility However for now have constrained the field to vary in x and have output only the real and imaginary parts of Xxx in other works m h Main Globals Materials Boundary Computation Initialize Fields Current Layer Props Layer BCs Notes Batch Af HysU f HysNU A pm 2 FMR s Shields n FMR and Frequency Dependent Suseptibility gt Le DoFMR Susepibiy FMR Fen ee Component Min Oe Max De x y 500 z 0 T Suseptibility Min 21 Number DC Field Points FMR Suseptibility AC der and Polarization 1000 Component Field De Phase x 1 Y Z E pmi Number AC Field Points for Chi 21 Freq GHz FMR gt Min 20 B Min GHz Max GHz Convergence gt max y 0 005 dx x cycle h Minimum Cycles 4 Accept CI anges 3 Reject Changes FIGURE 61 FMR Page 19 134 LLG Micromagnetics Simulator User Manual CHAPTER 20 Inputting Data into LLG Shields You can specify the presence and position of finite permeability field shields as well as specify the media used to excite a sensor You can use shields for any problem under study You
161. ations Convergence criterion as a hard exit however it is useful for catching cases that will never meet the convergence exit criterion such as when there is a loose spin in a corner A loose spin will appear to oscillate in the effective field of its neighbor due to the low coordination of its own spin envi ronment In such an instance LLG will never meet the convergence exit criteria for maximum residuals however the spin configuration of the entire system might be well converged It is for just this type of situation that the Maximum lterations Exit Criteria was designed Note that loose spins can be tightened by choosing a finer grid and by decreasing the time step LLG Micromagnetics Simulator User Manual 10 93 Chapter 10 Inputting Data Into LLG Computation Single Iterations You should be aware that in LLG a single Iteration is one relaxation pass through the entire collection of sub elements For systems composed of between 5 000 and 10 000 sub elements setting the Iterations from between 2 500 and 10 000 yields effective results ENERGY UP ENERGY CRITERIA LLG has a damping term that guarantees that the energy of the system decreases with time Instead of exiting at the convergence limit you can enable LLG to exit when the energy begins to increase that is when the numerical preci sion of the problem has been reached This is not independent of the Time Step and should be handled carefully In the edit box enter t
162. ber 2002 1 FMR Dynamic suseptibility 2 Specify adaptive integration 2 Demag field calculator utility 3 Implement Gause Seidel integration Version 2 50 Released June 2003 with an Updated 4 Import bitmap files for position dependent parame Manual ters 1 Updated domain viewer utility 5 Define edge magnetization and edge roughness 2 Time and position dependent external fields effects 3 Heff field flagging 6 Specify 3D Voronoi cell discretization 7 nterpolate movies 8 Edit the numerical values of graphics 9 Save and load graphics to LLG 1 20 LLG Micromagnetics Simulator User Manual CHAPTER 2 GETTING STARTED SYSTEM REQUIREMENTS To install and run LLG Micromagnetics Simulator you must have at least the following A 600 MHz Pentium Pro III 256 MB of RAM A video card that supports a minimum of 16 million colors at 1280 x 1024 resolution such as the ELSA Winner 2000 ProX 4 MB RAM or the Matrox Millennium II 4 MB RAM A 17 monitor that supports at least 1280 x 1024 at 70 Hz although the letters appear rather small At least Service pack 3 for NT4 0 workstation Win2000 Win xP are acceptable To take advantage of LLG on an NT 4 0 Workstation you should have the following A Pentium III 733 MHz CPU Dual CPUs are supported by LLG 512MB of RAM are required for larger problems A computer with a 512MB capacity allows you to add memory as needed An Adaptec 2940 UltraWide SCSI adapter 68 pin
163. between Limit 1 and Limit 2 The first field section is the ONLY section that has n 1 points Every other field section will have the specified number of points n You must either add the extra point to the first section or the last in LLG it is in the first LLG Micromagnetics Simulator User Manual 30 215 Chapter 30 Sample Problem 5 Non uniform Hysteresis Loop for a Platelet 14 15 16 Then click the LOAD SECTION button to enter the field section 1 into the hysteresis loop If you do not the field section will not be added to the hysteresis loop This completes the specification for the first field section Sections Loaded should indicate 1 and Points Loaded should indicate 11 Either use the arrows next to Field Section Specified to advance to section 2 or enter 2 into the edit box Notice that LLG automatically records Limit 2 from field section 1 in the Limit 1 position for field section 2 Enter 450 0 in the Limit 2 edit field for Hx Leave Hy and Hz set to zero This is the final field point for the second hysteresis field section and the initial field point for section 3 Enter 15 in the Number Of Field Points edit box Load the field section by clicking the LOAD SECTION button Use this same process in entering the remaining fields Enter 3 into the Field Section Specified edit box Enter 750 0 in the Limit 2 edit field for Hx Enter 6 in the Num ber Of Field Points edit box Load the field section by
164. blems require cubic rods cells The discretization CANNOT be modified once the input is complete GREEN S FUNCTION TYPE For 3D simulations you can use either a continuous magnetostatic hamiltonian Cont which is recommended or a point dipole approximation Pt Dipole This affords you extra flexibility in seeing the real deviations from the simple point dipole approximation in determining the minimum energy configuration Although you will most likely never choose to use point dipoles such a model is useful when comparing analytic results and computations in critical phe nomenon theory Currently point dipole fields are used only in 3D computations This selection CANNOT be changed once a simulation has begun 6 76 LLG Micromagnetics Simulator User Manual Chapter 6 Inputting Data Into LLG Main 2D DISCRETIZATION For 2D problems continuous boundary conditions can be selected in the Boundary Page To this end a separate dis cretization scheme has been implemented whereby the self fields are computed interface by interface rather than cell by cell This option will be of little or no interest unless you wish to simulate the central portion of a continuous film or the top of a semi infinite substrate NOTE This feature is presently not fully implemented in v2 which is the same as in v1 SIMULATION VOLUME The Simulation Volume is the discretized system under study Please take care when entering the discretization vol
165. c Uaxst Main Arrays Properties FIGURE 31 OGL Selector Sheet Properties Page MEMORY LOAD AND MEmory STATUS PANE Refer to the window toward the bottom center of the screen for the memory load and the available physical memory LLG does not modify Windows NT memory in the sense that if an unusually large disk cache is allocated in physical memory then the program assumes that this memory is in use and does not try to reallocate it If you have less mem ory than anticipated close all other programs Since the program uses a lot of CPU cycles it is generally best not to run other programs while you run LLG PROGRAM STATUS PANE Consult the window toward the bottom right of the screen for the status of program operations For instance while the program is starting up and while the LLG Input Sheet is in view the window says Initiating LLG Micromagnetics Like wise if you select the Pause button during a computation it reads Pausing Computation LLG UTILITIES ALTERING LLG S APPEARANCE AND BEHAVIOR LLG uses two utilities to alter the look feel and functionality of the program Close all LLG windows using the menu selection located under File at top left The main menu will be replaced with the utility menu Under Tools you will find the following Customize Install Cool Tools Install Number Editor Filter FIGURE 32 Utility tools LLG s flat look and feel can be toggled on off by checking the
166. can be selectively loaded with the appropriate Read File button The X Axis variable is selected from the list at the upper left for a given file type you can select as many Y Axis variables as you want from the list at the upper right Each x y pair is a separate plot and can be examined in the window to the right At the top right you can scroll through the x y point pairs in your graph You may also replot the energy as a function of the externally applied magnetic field in order to more precisely determine the switching field flat energy curve By RIGHT CLICKING on the graphics window you have the options to e Toggle the Points Window on and off e Toggle Autoscale on and off Points window D e Toggle the Plot Symbols on and off FORMES e Toggle the Mouse Coordinates tracking on and off v Plot Symbols Mouse coordinates e Toggle the Grid Overlay on and off v Grid Overlay e Zoom in and out pun tool PP eoa e Copy points to the text buffer for pasting into docu Fit gt ments Undo Copy D e Reset the graph Properties pete This is not meant to be the kind of tool that you would find in a commercial graphics software package but rather is included to allow you to probe your LLG data quickly and efficiently LLG Micromagnetics Simulator User Manual 5 55 Chapter 5 LLG Environment d d e e d 6 e d 6 e 6 6 6 e s MO of o of of 0 DEG 00000600 OE 0 00000000 GE GGG 090000 000
167. can select either a uniform hysteresis loop Hys U Page a non uniform hysteresis loop Hys NU Page a time dependent h field Time Dep H Page or a moving media problem Shields Page These are mutually exclusive only one mode can be used for a given problem SPECIFYING SHIELD ATTRIBUTES For any LLG simulation you can select shields that are parallel to X Y planes only and that are separated from the object under study in Z e Activate either one or two shields by checking the Min and or Max boxes e Inthe Distance to Shield nm edit boxes below Min Below On Off and Max Above On Off enter the distance in nanometers from the bottom or top of the shield to the magnetic material of the shield s inner towards simulation volume surface e These vacuum gap distances are measured from the top and or bottom of the magnetic material to the surface of the Mu metal shield Internal to LLG the shields are replaced with 3D image charges to screen current and sensor magnetization For shielding the fields due to external fields and media fields the finite extent of the shields in the transverse direction must be specified In the Shield Edge edit boxes you must enter the distance in nanometers from the edge of the magnetic material to the edge of the shield in the transverse direction e Enter the relative permeability of the shields in the Mu MuO edit box which accounts for the image charges due to the current IMPORTANT NOTE Since shields
168. ce for coordinating input parameters error checking and setting critical glo bal parameters In general inputting data specifications is the most tedious aspect of numerical simulations The pro gram has been designed to allow you flexibility in customizing simulations however this makes the data specification phase time consuming and increases the risk of input error Although as a counter measure LLG performs exhaus tive error checking to prevent floating point exceptions defining a structure and how well it models an actual material or device is ultimately the user s responsibility Since the program solves the Landau Lifshitz Gilbert equations using finite differences for exchange energies and fields as well as boundary elements for magnetostatic self energies and fields the structure of interest must be defined as a grid The program uses rectangular pixels on a Cartesian grid Although you can change the material parameters including eliminating magnetic material altogether this must be done on a Cartesian grid Once you have specified the structure and clicked the Begin Simulation button LLG initializes all of the arrays com putes the demagnetization field coupling tensors and calculates the fields for any boundary conditions Once these large arrays have been specified the simulation phase can begin Also you are prompted to store the simulation parameters in several files SIMULATION PHASE SOLUTION OF THE DIFFERENTIAL EQUATIO
169. change X Uni Dir Y Cub Dir 3 Y Exchange Y Uni DirZ Cub Dir 3Z Exchange Z Cub Dir 1X Rho Anis Uniaxial 2 Cub Dir 1 Y AMR Anis Uniaxial 4 Cub Dir 1 Z GMR Anis Cubic Cub Dir 2 Bilinear Anis Sur Art Cub Dir 2 Y Biquadratic Hpin X Cub Dir 22 j Hpin Y Polarization Hpin Z T FIGURE 76 Position Dependent Parameters Sheet Graph Page Once you have specified parameters for a problem you can analyze those properties through the Graph Page 1 Define a region of interest see page 148 2 Right click on the region and select Distribution Resample generate a histogram of the data for viewing 3 Then click the Draw Graph button to illustrate a histogram of your Parameter Selection Be sure that you have specified the desired properties In the sample in the menu above a saturation magnetization of 800 100 was selected The graph illustrates the gaussian distributed random variables centered about 800 with a o of 100 LLG Micromagnetics Simulator User Manual 22 155 Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETERS SHEET MEDIA PAGE BC Bitmap Edge Custom Input Custom Graph Main Params Exch Materials Graph Media n l Randomly Group Cells in 2D or 3D p 2D Grouping Graphical Mean Domain Dimension nm 35 Deviation in Domain Dimension nm 10 Tile The Surface Clear The Tiles Fill 2D Tiling Parameters m
170. check box enables or disables the inclusion of the gyromagnetic term in the torque equation The default is selected ALPHA This is the LLG phenomenological damping parameter unitless Since Alpha controls the time scale for the magneti zation approach to the effective field direction it governs how quickly a solution converges The check box enables or disables the inclusion of the damping term in the torque equation The default is selected Real materials can have val ues of a in the 0 01 range however not much is known about the origin of this component of the relaxation it is still a live issue Setting Alpha to one provides the same final solution to identical problems as 0 01 solutions in a frac tion of the computation time for domain wall systems that have been extensively tested Also the energy minimization method functions essentially as an o large computation Setting o to a value larger than one is not recommended Experiment with a small a for starters try a 1 START T NS This is the starting time for a calculation in ns STOP T NS This is the ending time for a calculation in ns T4 T2 lt 109 Use these only for the Time Integration solution method ology and not for Relaxation TEMP T K This is for activating the finite temperature solver LLG features one finite temperature method Langevin dynamics for the quasi time based algorithms R Koch and G Grinstein IBM Yorktown Heights have SOLVED
171. checking the Read File box and selecting a file name using the Input File Name button Once you have specified all of your parameters you MUST click the Load Layer BC button for your entries to be recorded Once you have loaded a layer s Boundary Conditions the background color of the edit box changes from white to yellow You must repeat this sequence for each layer as you enter the properties Since LLG uses property pages and property sheets to record data sequences you must signal LLG that your entries are to take effect Thus once you finish entering each layer s properties you must click Load Layer BC Once you complete all of your data entry you MUST click Accept Changes for all of your layer changes to be permanently recorded Note since the lay ers are in z the top and bottom layers do not change when you scroll through the layers DESCRIPTION VARIABLE LIMITS Load Layer BC Niayer 1 Njayer Njayers Left X 0 mi 10 lt m lt 1 0 Right X N m 1 0 lt m 10 Front Y 0 mi 1 0 m 1 0 Back Y Ny mi 1 0 mj lt 1 0 Bottom Z 0 mi 1 0 m 1 0 TopZ N mi 1 0 mj 1 0 LLG Micromagnetics Simulator User Manual 15 117 Chapter 15 Inputting Data Into LLG Layer Boundary Conditions SF HysU ST HysNU TimeDepH w Shields Main Globals Materials Boundary Computation Initialize Fields Curent LayerProps Layer BCs Notes Ke Load Layer BC 1 i La
172. coefficient and m and m are the direction cosines adjacent to the non magnetic spacer layer The bilinear and biquadratic exchange fields are defined in terms of the appropriate derivatives with respect to magnetization thereby introducing a sub element size depen dence into the exchange field LLG Micromagnetics Simulator User Manual 14 115 Chapter 14 Inputting Data Into LLG Layer Properties CALCULATING THE EXCHANGE BIAS In LLG Micromagnetics Simulator exchange energy density is defined as Esx Vm dv where A is the exchange stiffness in erg cm V is the gradient operator m is the direction cosines and dv is the vol ume element LLG implements this exchange integral on a finite difference grid with piece wise uniform variables Hence the effective field due to exchange on a given cell is uniform cubic grid 4 9E AD AM Hex ex _ 24 xm ym zm gt 2 oM MA Thus the exchange effective field scales as 2A M A and the direction cosine of the nearest neighbor The exchange field strength for adjacent pixels across a layer is Hex 24 MAT where M is the magnetization in the layer of interest and is the direction cosine across the interface layer Therefore the exchange coupling parameter can be calculated as Ag M A 2 H as a function of the exchange field and dis cretization This is the protocol used in LLG SPECIFYING THE ANISOTROPY TYPE The anisotropy types are Cubic C
173. created with a sep arate graphics application IMPORTANT NOTE LLG recognizes and applies ONLY BLACK as the color of the mask so the mask region of your graphic MUST BE BLACK in the RGB sense 0 0 0 e Specify which layers you want to mask on the Position Dependent Parameter Main Page page 151 and whether you want to turn on or turn off the region internally or externally e Load an image file by clicking the Open button and selecting the file type from the options An image of the file will be painted in the window on the Bitmap Page The spatial extent of the image is scaled to match the size of the projection of your structure e To flip and rotate the image click the Flip button and select the desired option e Click the Apply Mask button to visualize your changes in the graphics window DEFINING POSITION DEPENDENT PARAMETERS WITH AN IMPORTED COLOR MAP Instead of using LLG s drawing tool you can import an image that you have created with a separate graphics applica tion with up to 20 regions of color LLG uses the image as a map for identifying mask or position dependent parameter regions with each region identified by a color LLG reads the image pixel by pixel starting with the first pixel in the upper left and generates a record of up to 20 colors from the image This allows you to specify up to 20 parameter sets for an imported image Only the properties from the Main Params and Exchange Pages of the Position Dependent Pa
174. cs LLG Micromagnetics LLG Micromagnetics LLG Micromagnetics LLG Micromagnetics LLG Micromagnetics LLG Micromagnetics NLLG Journal Entries LLG Journal Contents 7 a Ready SORTING JOURNAL ENTRIES FIGURE 4 Journal Viewer Journal Entries Page You can sort LLG journal entries by double clicking the column header e To sort by date double click the Date header e To sort by file name double click the Base File Name header To sort the list by title double click the File Title header A second double click sorts any list in inverse order EXAMINING JOURNAL ENTRIES Once you have compiled a journal you can use the list to examine the file s contents Using the mouse right double click the left most column of the row that contains the file that you wish to view The contents of that file if it is an ascii LLG Micromagnetics Simulator User Manual 4 35 Chapter 4 Loading Saving Files file will be loaded into the LLG Journal Contents window tabbed at bottom as shown below Print the formatted journal contents by clicking the Print icon te LLG Micromagnetics Simulator Journal Viewer LLG Journall File Edit View Format Window Help nje m e S elele LLG Micromagnetics Simulator Journal Viewer File INlg v2 0 work 1 7 11 2001 15h30m55s M 12 llg param File Contents File Version 2 05 LLG Version 2 3 01 02 Jul 2001 Time 15 30 55 Date lt 1
175. csosrdaaavsseuassssseleawsuedendduassonuads 31 File TYPOS mase EE 31 Bitmap e ul EE 31 Input Specifications IG paraM sesi tie i ei oh tee t eed diia 31 Direction Gosines llg e inn EE 32 Convergence Data iq CONV iioi e dere n td dan ed eite date tete e pre e be n Reo 32 Material Properties llg material E A essen eene nennen nnne EA rinse nisse nn 32 Position Dependent Magnetic Fields llg inputhfield AAA 33 Hysteresis Field Profile llg hysfield rrrnnnnornnnnnnnnnrnnnnnnnnnnnnnaannnnnnnnnnnnnnnnnnannnnnnnnsnnnnnnnnannnnnnnnsannnnnnnnsannnnnnnee 33 Hysteresis Field and Magnetization llg bye oooocoonnnninicinononociconnnnnccnccnnnarrr cnn naar rc cnn rc 33 Magnetization Masks llg mask O 33 Magnetic Field lg BR UE 33 Graphical Animation Movies llg movie nennen nennen nni intret sinn 33 Position Dependent Parameters llg position ooooonoocccnnnnnocccccccnnoncnccnnnnoncnnnnnnnonnnncnn nan n cnc cnn nennen nennen nnne enn 33 Color Map Files llg colomap nennen nnn aad atado aaa Aaea i ep r dAn adn Eanan en 33 Shape Files NAPO ci oe iether 33 Using the LLG Journal Viewer 34 Opening an Old Joutnal File 1 certes tiit REP dein cp adde Pot eee det ein aie Udo tur dee AEN 34 eltern BEEN 35 Examining Journal Erres eeh Nee Ae dee e in te eo A dtes 35 Modifying Comments in Parameter Files sse eene nennen teen r erri nnne inns rennes 36 Greating a New
176. ction key 22 the protection key driver 22 integrated b view option 176 intercell exchange 153 interlayer bilinear and biquadratic exchange 153 interlayer coupling antiferromagnetic sample problem with 223 227 229 demag sample problem with 223 GMR type sample problem with 229 turning off between layers 224 iterations 93 definition of 94 recommendations for setting 93 status indicators of 165 J journal entries sorting 35 journal files opening old 34 journal viewer 34 K kanji and hangul environments installing LLG in 23 L LaBonte wall See Bloch wall layers boundary condition parameter limits for 117 boundary conditions for 117 color coding 114 coupling across non magnetic layers 115 coupling between 115 definition of 111 FFT method with variable thickness of 111 important note regarding 1 layer position dependent structures 147 important note regarding 1 layer structures 114 important note regarding input sequence 74 parameter limits of 113 pinning 103 process for defining 114 sample problem with coupling between 227 sample problem with GMR 229 sample problem with steps for input 223 specifying the coupling across 115 total thickness of 114 224 turning off coupling between 224 license agreement 17 18 LLG files searching for 37 lock files 189 loose spin 93 M magnetic field file type 33 magnetic media generating properties for 156 magnetic platelet sample problem for non uniform hyst
177. d characterized by the constant K erg cm 3 the surface magnetocrystalline anisotropy energy Eks which cor rects for broken symmetry near surfaces in the interaction of the magnetic moments with the crystal field and is char acterized by the constant Ks erg cm 4 the magnetostatic self energy Es which arises from the interaction of the magnetic moments with the magnetic fields created by discontinuous magnetization distributions both in the bulk and at the surface 5 the external magnetostatic field energy Ey which arises from the interaction of the magnetic moments with any externally applied magnetic fields and 6 the magnetostrictive energy E which arises when mechanical stress strains are applied to a ferromagnetic material thereby introducing effective anisotropy into the system charac terized by K erg cm The solution for the equilibrium magnetization distribution is a constrained boundary value problem in two or three spa tial dimensions with the constraint of constant magnetization M The continuous magnetization distribution of a ferro magnet is approximated by a discrete magnetization distribution consisting of equal volume cubes 3 D or rods 2 D Each individual discretized magnetization cell interior to the array will be addressed by the X Y Z coordinates of its centroid There are N cells along X Ny cells along Y and N cells along Z interior to the structure to be modeled There is one plane 3 D
178. d then cools The sample is 512 x 512 x 50 nm 128x128 pixels The nominal properties for the materials are Property Value Units A F1 B F1 Ms 180 emu cm3 1 0 Ku 2000000 erg cm 1 0 A 0 4 uerg cm 1 0 Te 441 K N A N A Ti 0 1 ns N A N A To 0 1 ns N A N A Tpeak 0 1 ns N A N A Tend 0 1 ns N A N A Tamb 300 K N A N A Triax 500 K N A N A Hc A HAK Magnetic Parameter M T 0 1 80 2 K T 0 2 0046 A T 0 0 4e 6 He T 0 2 2e 4 A A K 0 5 17 6nm 0 2 H 01 00 1 I L 1 1 1 00 01 02 03 04 05 06 07 08 09 10 T Tc Magnetic Parameter FIGURE 156 Magnetic Parameters for the Sample Problem LLG Micromagnetics Simulator User Manual 46 277 Magneto Optical Simulations Supplement Temperature Pulse 0 0 Tend FIGURE 157 Temperature Profile for the Sample Problem This sample was run through heating cooling cycles in a variety of external fields 46 278 LLG Micromagnetics Simulator User Manual INDEX Numerics 2D discretization 77 2D narrow or wide 100 2D plotting 55 2D problem formation of Bloch and Neel walls 243 simple example of 219 2D real FFT method using periodic boundary conditions with 92 with shields 135 with variable thickness layers 111 3D complex FFT method 92 3D transition magnetization 99 3D uniform magnetization 98 3D vortex magnetization 100 3D warping 59 A activate picker 71 AIJ 115 alpha 94 anisotropy types 116 antiferromag
179. dependent time vary ing uniform fields Current Page at any time during a simulation FMR AND DYNAMIC SUSEPTIBILITY You may choose between computing the FMR loop scanning H for a fixed frequency or a dynamic susceptibility loop scanning frequency for a fixed external field To activate FMR you must check the Do FMR Suseptibility check box You can select between FMR and Dynamic suseptibility by clicking on the appropriate FMR or Chi button You specify the number and range of the DC field points an ac field magnitude in H for now and a frequency in the FMR case or a DC field and ac field and the number and range of frequency in the susceptibility case Since LLG computes FMR loops in time you should be sure to uncheck the convergence and iteration boxes in the computation page so not to exit prematurely Also leave the t 2 ns check box in the Compution page unchecked LLG will store the frequency dependent field in an array and accumulate the magnetization vector at each time step Once one period of oscillation is complete LLG will compute the real and imaginary part of the susceptibility at the frequency of excitation LLG mea sures the peak in the ac excitation and finds the time shift relative to the peak in the ac field You set an exit criteria at the bottom the of FMR page as the largest fractional change in the susceptibility and the minimum number of cycles Since the field ramp may only produce a small perturbation to the oscill
180. dified This is particularly impor tant when there is an interface between dissimilar materials For 3D systems where layers occur with Z directed nor mals you must independently specify how a material layer will couple across the interface LLG provides you with the flexibility to make the assignment with the Au interlayer For example suppose your layered structure has a dirty evap orator that creates carbon at the interface which greatly reduces or eliminates the coupling This would allow you to put real coupling across the interface Aly Bilinear is the coupling across a non magnetic layer This is the GMR type of coupling that can be ferro or antiferro depending on the thickness of the interlayer You can modify the coupling between adjacent layers Assuming that the layer specified is layer 2 in a 3 layer system you can specify the exchange coupling between layer 2 and layers 1 and 3 that is A12 in the edit box next to the num ber of the layer to couple to in this case layer 1 or 3 To modify the exchange between layer 2 and layer 1 alter the number in the edit box next to the 1 Interlayer exchange operates only between adjacent layers To modify interlayer exchange across non magnetic interlayers use the Bilinear or Biquadratic exchange fields MODIFYING BILINEAR AND BIQUADRATIC INTERCOUPLING AND GMR You can modify the Bilinear and Biquadratic exchange across non magnetic spacers as in Co Cu GMR superlattices When you know the exch
181. e 0 work MestNS ample15 llg param 0 Edge Demag Shape Specifier 1 0 Yes No Mlo v2 0 work test S ample14 deg lla param Mlg v2 0 work test S ample1 PD Io param O Layered Magnetic Parameters Mlo v2 0 work test S ample21 lla param O 1 Use Layers 0 No 1 Yes O 2 Number Of Layers 8 000000e 007 0 Layer Thickness cm v 800 000000 0 Layer Magnetization emu cm 3 1 050000e 006 0 Layer Exchange X erg cm 1 050000e 006 0 Layer Exchange Y erg cm 1 050000e 006 0 Layer Exchange Z erg cm 1 0 Layer Anisotropy Type 0JKU 1 KC 2 KU and KC 0 000000 0 Layer Uniaxial Anisotropy 2nd Order erg cm 3 0 000000 0 Layer Uniaxial Anisotropy 4th Order erg cm 3 0 000000 0 Layer Cubic Anisotropy erg cm 3 1 000000 0 Layer Uniaxial Anisotropy Axis X Projection C 0 000000 0 Layer Uniaxial Anisotropy Axis Y Projection 0 000000 0 Layer Uniaxial Anisotropy Axis Z Projection 0 577350 0 Layer Cubic Anisotropy Axis 1 X Projection 0 577350 0 Layer Cubic Anisotropy Axis 1 Y Projection E 0 577350 0 Layer Cubic Anisotropy Axis 1 Z Projection 0 816497 0 Layer Cubic Anisotropy Axis 2 X Projection 0 408248 0 Layer Cubic Anisotropy Axis 2 Y Projection zi Read Seed File Generate Files Clear All Clear All Parameter File Generate Parameter Generate Batch File Used to Seed Script and Batch Files from Parameter Files Files Processed To Batch File Mllglv2 O work test test3 llg_batch Noe Dark test S ample3 llg param I Mllg v2 0 work test
182. e of the parameters Click the Selector tab then click the Arrays tab Click the Activate Picker box Also you can click on points in the hysteresis loop to ascertain their values 28 208 LLG Micromagnetics Simulator User Manual Chapter 28 Sample Problem 3 Uniform Hysteresis Loop for a Magnetic Platelet COMMENTS Notice that the sub element size was specified to be 10 nm This is near the upper limit that yields converged solutions for Permalloy Try rerunning this sample with 12 sub elements per side which makes the problem unstable with the 1 Pt minimization method The instability is a result of setting the sub element size too large When the simulation begins the moments will oscillate back and forth and in the worst case the residuals displayed in the Simulation Page will near 2 0 This is a pathological situation If a simulation enters this regime STOP THE PROBLEM IMMEDI ATELY AND RE INITIATE IT ON A FINER GRID Test your residuals when running any calculation for the first time If you notice the characteristic red and blue stripes in the Bitmap Graph Type of the Residual Changes Iteration View Option decrease the time step for parallel algo rithms If that doesn t work stop and refine your grid Also note how high the convergence parameter is set This high a value will only work on extremely small problems such as this one and then not always accurately Try this problem again set the convergence exit criteria to
183. e entered in picoseconds ps 4 Specify the number of time steps in the Time Interval Steps edit box 5 Specify the time step itself in the Time ps Step edit box Only one time step is allowed for all time intervals that is itis a fixed time step calculation of the current NOTE IF YOU USE BOTH TIME DEPENDENT CURRENT AND TIME DEPENDENT FIELDS BE SURE THAT THE TIME STEPS ARE IDENTICAL 6 You MUST load the field section by clicking the LOAD SECTION button Each section must be loaded since the same controls are used both to examine and to modify the field values 7 Increment the Time Interval Specified counter and enter the data for the next field sector While editing the time dependent field sections click DELETE SECTION to remove field points from the hysteresis loop Remove all the specified Time Intervals by clicking the Clear All button SUPERIMPOSING SINUSIODAL I You can superimpose a sinusoidal current on the time dependent current by specifying the following e The ac current lo in microamps e The frequency in b in 1 ps e The time shift c in ps e The starting t1 and stopping t2 times in ps SPECIFYING SPIN TORQUES In 1996 John Slonczewski wrote a paper JMMM 159 1996 L1 L7 where spin torques resulted from a direct interac tion between spin dependent current generated in a ferromagnetic layer polarizer incident upon a second ferromag netic layer analyzer through a paramagnet The spin torque check box allow
184. e format is in comma separated values so that you can prepare your data using Microsoft Excel and save the file using the Comma Sepa rated Value csv option The data are saved in columns in the following format headings are not part of the file itself T T M M T 0 A A T 0 K K T 0 M M T 0 M M T 0 0 0 1 0 1 0 1 0 1 0 1 0 0 1 0 9 0 9 0 9 0 95 0 85 0 2 0 8 0 8 0 8 0 90 0 70 46 272 LLG Micromagnetics Simulator User Manual Magneto Optical Simulations Supplement Once data are read from a file they are linearly interpolated onto a grid of equally spaced base points separated by T Te 0 002 i e 501 total points You should remain mindful of this scheme when entering data as interpolation of K and M near T can radically alter nucleation properties SPECIFYING TEMPERATURE DATA READ FROM FILE OR MOVE A GAUSSIAN PROBE You may read temperature data from a file or use LLG s internal temperature profiler If you want to use LLG s internal temperature profiler then check the Temp Funct box on the main MO Page If you want to read data from a file then DO NOT check the Temp Funct box on the main MO Page When you have checked the Temp Funct box on the main MO Page and you click the Read Temp button you will be prompted by the Functional Temperature Probe dialog box as shown below The generated function has the following form Custom MO Functional Temperature Probe m Laser Heating Ambient Temperature K
185. e has been expanded to 1000 z FIGURE 68 Super Egg LLG Micromagnetics Simulator User Manual 21 145 Chapter 21 Inputting Data Into LLG Mask Editor EDITING THE GRAPHIC COORDINATES Graphical Element Point E ditor na Graphical Element Point Editor p Object Type Rectangle Accept Update View Reject E xit FIGURE 69 Mask Editor Sheet Graphical Element Point Editor Sometimes the specification of your graphic requires a precision that cannot be achieved with the mouse In this case 1 Approximate the graphic with the drawing tool 2 Right click on the graphic and select Edit Selected Region Coordinates from the pop up menu The menu above will appear with the coordinates of the graphic in the edit fields 3 Editthe coordinates to create the desired graphic dimensions You can update the view before accepting the changes by clicking the Accept Update View button 21 146 LLG Micromagnetics Simulator User Manual CHAPTER 22 Inputting Data into LLG Position Dependent Parameters Pr TI 8 ES MMs pmet los LI 1 0 The Input Sheet Position Dependent Parameters Page is for locally altering the parameters in the magnetic system However BEFORE you can even access and enter data into the Position Dependent Parameter Pages you MUST have first defined the global parameters and committed the memory according to the sequence outlined below INPUT PREREQUISITES FO
186. e of the rotational hysteresis loop when you increase the value of the Anisotropy or make the struc ture longer increase the shape anisotropy 29 212 LLG Micromagnetics Simulator User Manual Chapter 29 Sample Problem 4 Rotational Hysteresis Loop for a Magnetic Platelet FEATURES Structure Sub Element Discretization Material Relaxation Initialization Hysteresis 150 nm x 100 nm x 10 nm 10 nm x 10 nm x 10 nm 15x 10 x 1 Permalloy 1 Pt Energy Minimization Uniform 10 from X in X Z Plane Uniform Rotational H 300 Oe Ny 37 Rotational Loop FIGURE 127 Surface Magnetization Pattern and Polar Hysteresis Loop during Switching in 3D Arrows LLG Micromagnetics Simulator User Manual 29 213 CHAPTER 30 Sample Problem 5 Non uniform Hysteresis Loop for a Platelet This sample problem is of modest complexity In this simulation a volume is descretized a single material property is set and a non uniform hysteresis loop is specified The flexibility provided by the non uniform hysteresis mode allows you to take advantage of the fact that the magnetization changes quickly as a function of the applied field near the coercive field while it changes slowly elsewhere therefore tuning the number of hysteresis points appropriately saves computation time INPUT SHEET MAIN PAGE Initiate an LLG calculation Use the same setup procedure and materials properties for Sample Problem 4 Except set the
187. e pede a 272 Specifying Position Dependent Parameters sssssssssssssssssseeese senem snnt enne nen 272 Specifying Parameters as a Function of Temperature 272 Specifying Parameters as a Function of Temperature using Funchons enn 272 Specifying Parameters as a Function of Temperature Using Data Read from Eiles 272 Specifying Temperature data Read from File or Move a Gaussian Probe nnen e ne 273 Read File Containing Temperature Data eene enneen nennen enn nnn nennen terrre seinen 274 Loading and Saving MO Parameter Files ssssssssssssssssseeeee nennen nennt nen trenes nnn enn 275 Viewing MO data using MO Graphic 275 eil 275 Sample Problem ieie niea tins Deed de a v las 277 INDEX hin 279 xii LLG Micromagnetics Simulator User Manual List of Flgures LisT OF FIGURES FIGURE 1 Keyscan Menu for Probing Protection Key Attributes nnna eee 23 FIGURE 2 LEG File Types seti S be She S Rete ee bebe ta P eme reri ros eec rem pies 31 FIGURE 3 Journal Viewer Main Page ssssese m rr 34 FIGURE 4 Journal Viewer Journal Entries Page 35 FIGURE 5 Journal Viewer Journal Contents Page 1 1 ren 36 FIGURE 6 Journal Viewer Journal Directory and Drive Selector 37 FIGURE 7 LLG Recursive Window Splitting Menu 1 s rh 53 FIGURE 8 LLG Environment 54 FIGURE 9 LLG Main Window Tool Bar 2 ett 54 FIGURE 10 2D Graphics Environment 55 FIGURE 11 2D Graphics
188. e simulation details after you have completed a simulation The Simulate a Movie options are described in Chapter 23 Simulation To use this option you must check the Simulate a Movie box before beginning a simulation ATOMIC COMPUTATIONS LLG can be utilized to run computations on atomic lattices In general LLG operates on a simple cubic lattice In this mode the magnetizations can be treated as continuous variables or discrete dipoles To use an atomic lattice compu tation you must first check the point dipole approximation Now check the Vol checkbox to activate the atomic volume selection and check the radio button with the lattice as sc simple cubic bcc body centered cubic or fcc face cen tered cubic Once you commit the memory LLG will display the cells as shown below on a 3x3x3 lattice Please note that LLG will remove atoms from the designated simple lattice to form bcc or fcc lattices so appropriate cell sizes must be selected Also the exchange calculator will now include all nearest neighbors in the exchange energy computation FIGURE 35 SC BCC and FCC Lattices on 3x3x3 Sites Viewed 1 off the x y Plane and 3 off the y z Face LLG Micromagnetics Simulator User Manual 6 77 CHAPTER 7 Inputting Data into LLG Globals Global LLG parameters are those that are specified for every cell in the Simulation Volume The Input Data Sheet Globals Page is shown on the following page The parameters are summarized b
189. ecord all the micromagnetic parameters at each discrete point COLOR MAP FILES LLG_COLORMAP These are ASCII files that store color wheels and color indices suitable for displaying data The data are stored in ASCII format SHAPE FILES LLG_SHAPE These are ASCII files that store Ilg outline shapes used in the position dependent graphics tool and in the mask graph ics tool The data are stored in ASCII format LLG Micromagnetics Simulator User Manual 4 33 Chapter 4 Loading Saving Files USING THE LLG JOURNAL VIEWER LLG Micromagnetics Simulator has a supplemental utility tool for generating catalogues of available LLG files This tool llgJournal exe is distributed with the LLG release You can place the executable file in your LLG directory and cre ate a desktop link to that file using the task bar manager You can use LLG Journal Viewer to view old journals create new journals or to examine the content of files on your disk Although the journal files are stored in binary format you can cut and paste either the journal log or the journal selections into any Windows based editor such as Wordpad and Microsoft Word that supports the OLE embedding protocol You can format your journal including font size and type color and column width and spacing Formatting information will be saved with your file To activate llgJournal exe double click the icon or the task bar link and the Jour nal Viewer Page appears as shown below
190. ed Note you are also afforded the opportunity to save field files in the Simulation Sheet View Page once a simulation has been initiated 5 Exit the page by clicking Accept Changes to log your changes IMPORTANT NOTE Saving the boundary condition field is important This is related to LLG s method for solving boundary value problems In LLG the direction cosines are fixed on the boundaries in sheets of sub elements If the moments have a component of their magnetization perpendicular to the boundary the charge at the boundary produces a field within the structure As such LLG modifies a problem in two ways when you use boundary conditions First the sheet of sub elements adjacent to the boundary will exchange couple to the boundary sub element direction cosines e Second the effect of any stray field from the boundaries is included at every point in the structure of consideration Internal to LLG these effects are independent This means that you can provide a means of having NON EXCHANGE COUPLED boundary condi tions in the following way For example you might want to simulate a structure that has permanent magnets made of CoPt at either end of the structure yet you do not want the magnets exchange cou pled to the simulation volume Begin a new simulation with a structure the same size and shape as your system under study Select the properties of your permanent magnet material for the global parameters for example the prope
191. ed in the simulation volume Alternatively the pinning field can be used to make films locally harder for whatever physical mechanism you are trying to model As far as LLG is concerned the pinning fields are just another external position dependent field that is added to the list of fields to which the magnetic moments are subjected INPUT SHEET EXTERNAL PINNING FIELDS 1 PSN 5 6 Initiate an LLG computation Initialize the problem as in Sample Problem 7 Click the Fields tab Use the slide bar or edit box to enter a 250 0 Oe pinning field in the Hx Oe Pinning Field input area Click the Load H Pin button to load the field Make sure that 1 appears in the Layer to Pin field so that this field is applied only to the bottom Fe layer Click Accept Changes and exit the page Click Begin Simulation and run the problem COMMENTS Compare these results with those from Problem 7 Observe the shift in the hysteresis loop LLG Micromagnetics Simulator User Manual 36 237 Chapter 36 Sample Problem 11 Non uniform Hysteresis Loop for a Pinned Platelet FEATURES Structure 250 nm x 100 nm x 20 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 25x10x2 Material Permalloy layer 1 and Fe layer 2 Relaxation 3D Complex FFTs Initialization Uniform magnetization directed 30 off the long axis Hysteresis Uniform H 1250 Oe Ns 21 Coupling Interface exchange coupling 0 Pinning Fields H 250 Oe on sub
192. edia INPUT SHEET LAYERS PAGE 1 Check the Layers box on the Main Page 2 Click the Layer Props tab 3 Set the parameters to the same values in the Layers Page POSITION DEPENDENT PROPERTIES 1 Check the PosDep box under Structure Properties on the Main Page Check the Commit Size box to fix the discretization volume This enables the Mask and PosDep buttons Click the PosDep button which activates the position dependent set of menus Click the Params tab Check the anisotropy direction box and then click the Any button Check the X Y and Z boxes and the Uniform box for uniform deviates in all directions 5 Click the Exchange tab and check the Ax Ay Ax and Ay boxes These are the boundary edge exchange val ues Leave them checked but set to 0 0 that is with no exchange across the grain boundaries 6 Click the Media tab and enter 100 nm for the Mean Domain Dimension and 40 nm for the Deviation PSN 7 Click Tile the Surface Then click the Unify Grains box to set the parameters uniformly within the grains 8 Click the Fill Parameters button to fill the parameters into the tiled areas Save your parameter file and start the cal culation LLG Micromagnetics Simulator User Manual 45 267 Chapter45 Sample Problem 20 Media FEATURES Structure 640 nm x 640 nm x 10 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 64 x 64 x 1 Doma great item De ortum Connes nea FIGURE 151 Media Magnetization
193. egration There are three exit criteria for the relaxation method and time limits for the time integration method Convergence Iterations and number of energy Energy Up increases are the relaxation method exit criteria Checking the box next to each criterion enables the edit box You must select at least one exit criterion However if you select all three the program will terminate the computation when the first exit criterion is reached Each criterion that you check will be examined for exit CONVERGENCE Enter the Convergence limit for exiting the calculation This criterion is the absolute value of the change during the iter ation process of any direction cosine component For Permalloy structures with 10 nm cubic sub elements a conver gence criterion between 1 x 104 and 3 x 104 should be suitable for most if not all problems If you select Average for Convergence Criteria the average of the absolute value of all deviations is checked against the exit criteria that you select In this case Convergence should be reduced by about 10 and would be between 1 x 10 and 3 x 10 for the above example ITERATIONS MAX Enter the maximum number of Iterations that the program should perform before it exits the calculation LLG will end the simulation or the simulation for the relaxation of a single field point in a hysteresis loop if the number of function iterations is exceeded ITERATIONS MIN Enter the minimum number of Iterations t
194. el to the surface of the film FEATURES Structure 400 nm x 100 nm Sub Element 10 nm x 10 nm Discretization 40 x 10 Material Permalloy Relaxation 1 Pt Energy Minimization Initialization Narrow Wall X Directed Dimensions 2 BC Left M 1 0 and Right M 1 0 31 220 LLG Micromagnetics Simulator User Manual Chapter 31 Sample Problem 6 Simulation for Asymmetric Bloch Wall in Permalloy ccceccem mt 4e c RK eee KEEFER LK eee KeeEERRASN eevee e K RA ryvvy gt rrifter 9vu22 72725 y 39 990022 KKK EE E E 23225523 ww kk E e S t amp H h D gt XE Pd 6 4 m o e ex k t E e e e II BORA KAR ox wk Eege eeu X f RR oT A Y Y a A A Lax 3 gt A do rom we e ZS 2 AAA NS co dm a e FIGURE 130 Magnetization Pattern in Cross Section in Arrows FIGURE 131 Magnetization Pattern in Cross Section in Bitmap LLG Micromagnetics Simulator User Manual 31 221 Chapter 31 Sample Problem 6 Simulation for Asymmetric Bloch Wall in Permalloy FIGURE 132 Magnetization Pattern in Cross Section in Contours X dMx Ms S XX FIGURE 133 Residuals Pattern in Cross Section in Contours LLG Micromagnetics Simulator User Manual 31 222 CHAPTER 32 Sample Problem 7 Layers with Demag Coupling in MRAM Hysteresis Loop This is the first problem with multiple material layers In the crudest sense it is a two
195. eld Pattern in 3D Arrows 204 FIGURE 125 Surface Magnetization and Effective Field Pattern in 3D Arrows Mode 206 FIGURE 126 Surface Magnetization Pattern and Hysteresis Loop during Switching in 3D Arrows 209 FIGURE 127 Surface Magnetization Pattern and Polar Hysteresis Loop during Switching in 3D Arrows 213 FIGURE 128 Non uniform Hysteresis Loop 2D View for a System with a Coercive Field near 375 Oe 216 FIGURE 129 Surface Magnetization and Non uniform Hysteresis Loop during Switching in 3D Arrows 217 FIGURE 130 Magnetization Pattern in Cross Section in Arrows 221 FIGURE 131 Magnetization Pattern in Cross Section in Bitmap 221 FIGURE 132 Magnetization Pattern in Cross Section in Contours llli 222 FIGURE 133 Residuals Pattern in Cross Section in Contours liiliil llis 222 FIGURE 134 Hysteresis Loop Showing Antiferromagnetic Coupling between the Layers 225 FIGURE 135 Magnetization Near Zero Field in 3D Arrows lee 231 FIGURE 136 Magnetization Pattern and Boundary Conditions Fields in 3D Arrows lsulssun 235 FIGURE 137 Hysteresis Loop from Unpinned Problem and 250 Oe Field Pinning LL 238 LLG Micromagnetics Simulator User Manual Xv List of Figures FIGURE 138 View of Mask FIGURE 139 Magnetization Pattern in Arrows Graph Type ooccccccccccc eh FIGURE 140 Magnetization Pattern in Cros
196. elow DESCRIPTION Saturation Magnetization VARIABLE Mg emu cm LIMITS 0 0 lt Ms lt 108 O 2 Uniaxial Anisotropy Kyo erg cm 1010 lt Kuo lt 10 O 4 Uniaxial Anisotropy Kua erg cm 1010 lt K 10 Cubic Anisotropy K erg cm 1010 K 10 Exchange Stiffness A uerg cm 10 A 10 Surface Anisotropy Ks erg cm 1010 K 10 Resistivity p uohm cm 0 01 p lt 106 Anis Magnetoresistance AMR 96 0 0 lt AMR S 1 0 Anisotropy Type KType U C or Both Easy Axis Direction KDir X Y Z or Any Easy Axis Direction Cosines Ax yz 00SA 251 0 LLG Micromagnetics Simulator User Manual 7 79 Chapter 7 Inputting Data Into LLG Globals Jf HysU HysNU Hit ZA FMR v Shields Fields Current Layer Props Layer BCs Notes Batch Main Globals Materials Boundary Computation Initialize n ey Properties Of Title gt r Ms emu cm 3 800 0 ZN Ku2 erg cm 3 1000 0 Kud erg cm 3 0 0 Ke era cm 3 0 0 A uerg cm 1 050 Ks erg cm 2 0 0 Rho u ohm cm 8 600 AMR Ratio 0 012 Polarization 0400 Easy Axis IN EM EN Any Anisotropy Type fut C to Heft P Axis Direction Cosines UNIAXIAL one vector Ax 1 000 Ay 0 000 Az 0 000 Easy Axis Direction Cosines CUBIC two vectors Ax 1 000 Ay 0 000 Az 0 000 100 Ax 0 000 Ay 1 000 Az 0 000 010
197. ems and interpolate the temperature data on the LLG grid assuming that your data are fixed to the LLG grid If your data are keyed to real coordinates then do NOT select this option You may shift your data by fixing the lower boundary This will shift your data as follows Check the Fix Lower Z Boundary to Z 0 and enter the shift value in the Bottom Z nm edit box If you enter the coordinate of the lower Z surface of the active data area 135nm in LLG_full txt on the accompanying CD your data s lower surface 135nm will be shifted to 0 0 nm internal to LLG i e Zi G Zrem Z Bottom Z nm Check the Fix Lower Y Boundary to Y Ylower and enter the shift value in the Lower Y nm edit box If you enter the coordinate of the lower Y surface of the active data area internal to LLG i e Y a Yrem Y Lower Y nm Check the Fix Lower X Boundary to X Xlower and enter the shift value in the Lower X nm edit box If you enter the coordinate of the lower X surface of the active data area 135nm in LLG_full txt on the accompanying CD your data s lower surface 135nm will be shifted to 0 0 nm internal to LLG i e XL 6 Xfem X Lower X nm LOADING AND SAVING MO PARAMETER FILES You may load and save MO parameter files by clicking the buttons at the top of the main LLG MO parameter page These files contain all the functional parameter data temperature probe data and file reading shifting data specific to your problem Once you have saved your
198. en but not for file saving LLG Micromagnetics Simulator User Manual 1 19 Chapter1 License Agreement and Release Notes e To save the MFM data to a file ACCURATELY be sure that NO other computed views torques are selected the one and only com puted view is the MFM view selected Version 2 1 Released April 2001 with an Updated Manual With v2 1 you can 1 Warp bitmap and contour graph types in 3D 2 Overlay color arrows and contours onto the selected graph type 3 Specify minimum and maximum Iterations 4 Specify either the absolute value of the e largest normalized torque average normalized torque e largest change in single direction cosine average of all direction cosines Version 2 2 Released June 2001 with an Updated Manual With v2 2 you can 1 Specify demagnetization edge correction Version 2 3 Released July 2001 with an Updated Manual 1 Run problems in batch mode 2 View and organize LLG files with a journal viewing tool Version 2 45 Released August 2002 with an Updated Manual 1 Atomic lattice computations 2 Asymptotic energy fitting in 2D Graphics environ ment 3 Remove k 0 component of residual flux in periodic problems using the 3D complex FFT solver Version 2 46 Released August 2002 with an Updated Manual 1 Spin torque computations 2 Interface anisotropy for layers 3 Dynamic magnetization visualization Version 2 47 Released Decem
199. en modifying foreground and background colors e The program defaults to the foreground view For saving LLG bitmaps for eventual printing on a standard rather than a color printer click the B W button Red Green Blue r RGB Colors 1 000 1 000 0 000 ETT Revert BZW Front Qut Back In HSB Colors Hue Sat Bright 0 167 1 000 1 000 DE Modes L Orient Moc Fy FIGURE 19 OGL Property Sheet Color Page 5 64 LLG Micromagnetics Simulator User Manual Chapter 5 LLG Environment OGL COLOR SHEET The OGL Color Sheet controls all essential OGL color functions There are three sub pages 1 Color 2 Wheel and 3 Table You can toggle between the pages by clicking the appropriate tab OGL COLOR SHEET COLOR PAGE The OGL Modes Prop Sheet Color Page is where you can alter and set the OpenGL color properties directly LLG s view is true 24 bit color You can modify the colors of the foreground and background with the Red Green and Blue controls as well as with the Hue Saturation and Brightness controls the values of which must be between 0 0 and 1 0 This page has identical functionality to that of the OGL Props Sheet Color Page except for the additional control of the drop down color button where colors can be selected directly from the Windows color palette The active selected color is displayed in the
200. en nsn sen rennen nint 148 Inputting Position dependent Parameters for the Area of Interest ooonnnccnnoniccnicccnnnornnanann conan conan o nana r nara nrnnnnno 149 Applying the Parameters and the Selected Color to the Area of Interest 149 Position Dependent Parameter Sheet Main Page 150 Specifying Fill Mask Regi n viii iuter e ete ad eee ep ORE Lade e Sd RED e n er Reg i ded 151 Specifying Mask Properties and Random Fill sess nne nn renes 151 specifying Layer Filltww nesete EE 151 Reading and Saving Position dependent Files nennen nennt nens 151 Determining if the Demagnetization Edge is Unspected enne 151 Position Dependent Parameters Sheet Params Page sse nennen nennen 152 Position Dependent Parameters Sheet Boundary Region Exchange Page ooooocccncccccnnociccncccnononnnccnnccnanancnnnnnns 153 Position Dependent Parameters Sheet Materials Page 154 Position Dependent Parameters Sheet Graph Page 155 Position Dependent Parameters Sheet Media Page nennen nennen 156 Position Dependent Parameters Sheet Bitmap Page sse eene 158 Specifying a Mask or Properties with an Imported Image eene enne nnns 159 Defining Position Dependent Parameters with an Imported Color Map 159 Specifying Edge Magnetization and Exchange Damping eene 161 Specifyinig Edge Roughress eet A ee iestad apie 161 Specifying the Demagnetization Edoe sse enne nennen nnns sen stnn nennen 161 A Demagnetization Edge Problem oooccccccn
201. enentis en tets tn sn isst n tenen enses n trte enn nennt nen 201 Input Sheet lnitialize Page eerie e teet ep te este he e e cx ne oat 202 SaviNgPIlES Take 202 Simulation Sheet Simulation Page miresine aai aeaaea iae i a a a aa aa aa aa asa arbi 202 Simulation Sheet Views Page nentes nenne sentes in nnns sentes sedis ennt sinn aset retener ases nennt 202 Comments ie eerta eaten dete E d ead n date sia ln eed ee t breeders 203 Featules coca dt e sace ums Lum s Ds AR 203 CHAPTER 27 Sample Problem 2 Basic Data Input for a Soft Magnetic Cube 205 EIERE ies fender rd e eec ce cte t edes ee ees 205 MD E 205 CHAPTER 28 Sample Problem 3 Uniform Hysteresis Loop for a Magnetic Platelet 207 Input Sheet RS EE 207 Input Sheet Globals Page and Materials Page sse ener nnne nnne 207 Input Sheet Computation Page ics cdi eee re EEN Pe ERR Rn er ee tene 207 Input Sheet Initialize Page 207 Input Sheet Hysteresis U Page rf oct ed ee Ree pr eene t eeu ber ege tat b tdg 208 resur e EIE EE 208 Simulation Sheet and OGL Properties Sheet ccccceceeeececeeeeeeeeceaeeeseeeecceaeeeseaeeseeaeeeeeaaeseeaeeeesaaeeseeeeesseeseeaeees 208 Viewing thie Fysteresis EoOp uskrevne skibakkene 208 COMMONS iia e bii eth e een tb apice T ANAE pte vest ve b dte 209 SIE 209 CHAPTER 29 Sample Problem 4 Rotational Hysteresis Loop for a Magnetic Platelet 211
202. equential double precision fields You can load an llg position file using the Read File button If the requested file does not have the same dimensions as your prob lem it will be rejected You can save a position file at any time with the Save File button Click the Read Mask button to import a mask file DETERMINING IF THE DEMAGNETIZATION EDGE IS UNSPECIFIED To compute the properties of shaped boundaries see page 87 you must specify one boundary to define the shaped edges LLG states on the bottom of the menu whether or not this shaped edge has been defined LLG Micromagnetics Simulator User Manual 22 151 Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETERS SHEET PARAMS PAGE BC Bitmap Edge Customimput Custom Graph Main Params Exch Materials Graph Media 2 Properties Of Ms emu cm 3 D 0 Ku2 erg cm 3 D 0 Kud erg cm 3 0s 0 Ke ferg em 3 0 0 A uerg em IP D 2 0 Ks erg cm 2 D 0 Rho u ohm cm D 0 AMR Ratio D 0 Polarization D D r Anisotropy Type Easy Axis E NE NNNM n 5 5 5 0 Any m Easy Axis Direction Cosines UNIAXIAL one vector Ax 1 Ay D Az 0 Easy Axis Direction Cosines CUBIC two vectors Ax 1 Pay Az 0 100 An 0 Ay 1 Az 0 010 xI YI Z Uniform or Angle gt 0 m Pinning F
203. er 5 LLG Environment 4 The 2D Graphics button enables 2D plotting Ze LLG Micromagnetics Simulator V2 0 Sergey ME Ele View Heb HBB emt 3 0 1 0 7 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 9 EF ma View Hysteresis and Convergence Files 20 Graphics Shifting and Scaling Controle H H Sht Sege d en TTT beer eo E40 64 Ed TIED CONT EN ERT H H i Micremagnetc stats Ploting Graphics pu d Convergence Fie bet Ni Resifi er i fa Wesahon Number H H Time Tme d Residual Beudus I Log 1 1 Eoi G R Riegel Eischen E arscobcpyl Pin or E demageetz hen Eldemognelizabor H h i Ejevtemall Eegen i Magnetization X g Ir Magnetization Y Hagen i gi in Hs HIN D i ubi ii A Hag Hag GC H is ES S AR t H H 1 uii Neier s nn SR 1 iid ti Determine Switching Fiss Zi ni You may find Hent to detemine Hc fit Et curve 41 3 G 5 nawy ergo curves wil be plotted noemalosd to 1 H Hu x y z JM D 9 ont EE r Hysteresis File Hysteresis Part Fie RosdFie Read Fie m YAm Xam m H H Hx Hs P M ER Mei M Hr He Mei My1 M M Met Mat Me Mx M2 M2 My My Mei Me2 Ma Mz Mp2 Mp2 v Nei R M3 M Mei Med Ma CM Cox Graghacs M23 Mad 0 1 9 2 0 9 0 8 0 6 0 6 0 7 9 9 0 9 1 0 1 1 1 2 1 2 1 4 2 5 FIGURE 10 2D Graphics Environment The 2D Graphics environment is where you can examine the contents of Convergence Files Hysteresis Files or Hysteresis Part Files The files
204. eresis loop 215 sample problem for rotational hysteresis loop 211 sample problem for uniform hysteresis loop 207 magnetic systems sample problem for shaping 239 shaping 139 magnetization 3D transition 99 3D uniform 99 3D vortex 100 aligning arbitrarily 99 magnetization direction cosines view options 168 170 magnetization dynamics sample problem in Permalloy platelets 249 magnetization masks file type 33 v1 input and output file format of 41 magnitude view 168 mask specifying properties 141 mask editor 139 committing size to access 139 point editor feature of 146 sample problem with 239 tool bar 139 mask files v2 input and output file format of 42 masks defining 139 demagnetization edge 141 important note regarding color of mask 142 input sequence 74 specifying properties 140 material entering a title for 81 material properties file type 32 input sequence 81 v1 input and output file format of 38 materials position dependent 154 materials database creating 83 loading 84 management of 84 parameter limits of 83 v2 input and output file format of 45 mean domain dimension 156 media cross track response 136 parameter limits of 137 sample problem with 267 specifying properties in magnetic 136 memory allocating for arrays 74 determining availability and load 72 requirements of LLG calculations 22 mesh density symptoms of setting too coarse 184 MFM images 176 MFM tip sample problem of pyramidal 253 sample problem wit
205. erge if you are arbitrarily close to a dipole CLosiNG DOWN A CALCULATION To end a calculation pause the calculation and then shut down LLG by clicking the Close All button on the Simulation Page LLG Micromagnetics Simulator User Manual 23 183 Chapter 23 Simulation GUIDELINES FOR RUNNING LLG SIMULATIONS Modeling problems with LLG involves some subjective interpretive judgement on your part The Input Phase demands precision in data entry However the data used to specify a problem in LLG is only a MODEL How well this model replicates a physical system depends upon many features including whether you have e Matched the size and shape of the structure e Included observable physical imperfections such as vacancies or roughness e Assigned the correct macroscopic magnetic parameters to the regions of interest e Specified field values for the hysteresis loops that saturate the system e Assigned the mesh density appropriately e Set the convergence and exit criteria appropriately Oversights in the Input Phase manifest themselves during the Simulation Phase in two typical ways solutions oscillate and fail to converge and the iteration process terminates prematurely Your Problem Fails to Converge LLG may not produce meaningful solutions when the mesh density is too coarse or when the quasi time step has been set too large Examine the iteration history when running a problem that you suspect or it may be extremely obvi
206. et Main Page oed ote t aei eerte i rete arre eo Me ent Re tU che SEAN 71 OGL Selector Sheet Arrays and Properties Pages eese 71 Memory Load and Memory Status Pane tenens eterne nennen nente tenes essere trn sees nennen 72 Program Status Pales EE 72 LLG Utilities Altering LLG s Appearance and Behavior nennen nens 72 CHAPTER 6 J putling Data into LLG Main iii Aa 73 INPUt SEQUENCE 5c emeret te ein ente oti hie Eee Gn A e te ete ad a bees eee Lote eod 73 Saving Convergence Data 76 Greens aei aa 76 Green s ee KE EE EN LE Rio s RN MEER ERR aa een uu ees 76 2D DiScretiZatior suse eebe d arsen ken iaa ds datae cet pe cade ee etg 77 Simulation Weu EE 77 Simulate a le D 77 Atomic GompUtatiols 53 51 19 kroer ee AN ae 77 CHAPTER nputting Data into EEG SGIODAS ia 79 Using the Materials Database to Select Parameters eene 81 Convention Tor Anson etd ee ire Dn erdt eec f dee e Pg oett dee rcs 81 Global Spin Toques e a a a E a a a aa aa aaa aa ap a iala 81 CHAPTERS Inputting Data into LLG MaterialS iii die 83 Creating a Materials Database sssssssssssssssssseeee eene nnne nennt nrnnret renis nnrnne 83 Loading a Previously Saved Materials Database Elei 84 Managing the Materials Database enne nennnnnrrn nennen nete rennen nnn nennen 84 CHAPTER 9 nputting Data into LLG Boundary Conditions caes serere
207. etics Simulator User Manual Chapter 4 Loading Saving Files m_fileStdio Write m_pLLG gt m_pMask nMaskSize Success m_fileStdio Close return TRUE Dom Files t_BOOL CDatalO WriteAngleFile2_01 t_pChar pFileName t_BOOL bAllocate t_Int nArraySize nIntSize nArraySize m nSize sizeof t Double nintSize 3 sizeof t Int Open File if Im fileStdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate Am fileException FileExceptionHandler amp m_fileException return FALSE m_fileStdio WriteString m_strVersion n 0 m strBuffer1 Format 966i966i966i m pLLG gt m nX m pLLG m nm pLLG m nZ m fileStdio WriteString m strBuffert WN0 Write Data for t Int k 0 k lt m pLLG m nZ k for t_Int j 0 j lt m pLLG m nY j for t Inti 0 i lt m pLLG m nX i m nOffset OffSetComputer i j k m_strBuffer1 Format 15e 15e 15e 15e 15e 15e m_pLLG gt m_pX m_nOffset m pLLG m pY m nOffset m pLLG m pZ m nOffset m pLLG m pAX m nOffset m pLLG m pAY m nOffset m pLLG gt m pAZ m nOffset m fileStdio WriteString m strBuffer1 n 0 Success m_fileStdio Close return TRUE H Field Files t_BOOL CDatalO WriteHFieldFile2 01 t pChar pFileName t BOOL bAllocate Open File if Im fileStdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate amp m fileException FileExceptionHandler amp m fileException return FALSE
208. etization 7x7x7 Material Permalloy exchange and anisotropy M 400 emu cm Relaxation 1 Pt Energy Minimization Initialization Vortex in Z Plane LLG Micromagnetics Simulator User Manual 27 205 Chapter 27 Sample Problem 2 Basic Input Data for a Soft Magnetic Cube FIGURE 125 Surface Magnetization and Effective Field Pattern in 3D Arrows Mode 27 206 LLG Micromagnetics Simulator User Manual CHAPTER 28 Sample Problem 3 Uniform Hysteresis Loop for a Magnetic Platelet This sample problem is of modest complexity The simulation requires a volume to be descretized a single material property to be set and a uniform hysteresis loop to be specified This is the simplest of all hysteresis loop problems INPUT SHEET MAIN PAGE 1 Initiate an LLG calculation by clicking the New button on the Tool Bar to activate the Main Page 2 Enter the Simulation Volume 150 nm for X nm 150 nm for Y nm and 10 nm for Z nm 3 In the adjacent discretization boxes enter 15 sub elements for N 15 for N and 1 for N INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 Click the Globals tab 2 Select U Uniaxial in the Anisotropy Type group box The uniaxial anisotropy edit field K should be enabled and the C Cubic anisotropy K edit field should be disabled 3 Click the Material Selector button which activates the Materials Page 4 Select Permalloy from the Precoded Materials and Properties section which loads Per
209. etization effective field residual and energy density appear in the edit boxes at the bottom the Selector tool must be directly over a point When you Pause LLG you can examine the numbers this way at any time during the simulation 6 Select the Residuals Change Iteration from the Views Page You will see the latest update on the residual pat tern Select the Demagnetization Field to see the demagnetization field If you like use the Selector to examine the numbers 26 202 LLG Micromagnetics Simulator User Manual Chapter 26 Sample Problem 1 Basic Data Input for an Fe Cube COMMENTS Notice that the sub element size was specified to be 8 nm This is near the upper limit that yields converged solutions Unstable Problems Try rerunning this sample with 6 sub elements per side which will make the problem unstable with the 1 Pt minimiza tion method The instability is a result of setting the sub element size too large When the simulation begins the moments will oscillate back and forth and in the worst case the residuals displayed in the LLG Simulation Control will near 2 0 This is a pathological situation If a simulation enters this regime STOP THE PROBLEM IMMEDIATELY AND RE INITIATE IT ON A FINER GRID Test the residuals when you are running any calculation for the first time If you notice the characteristic red and blue stripes in the Bitmap Mode of the Residual Change lteration View Option decrease the time step for par
210. every Check Lck ms as entered in the edit box at the top right of the Batch Mode Interface You can modify any file still in the queue that has not been processed or you can add or delete any param file from the Files To Process list box This gives you the flexibility of modifying the batch file s actions as the file progresses The file based Ick mechanism allows you to make changes over a network or remotely Once the Ick file is gone LLG begins process ing the next file in the queue Please note that the Ick file interrupt occurs only between the calculations of individual param files no checking occurs during the calculation itself Kf HyeU 47 HysNU TimeDepH w Shields Main l Globals Materials Boundary Computation Initialize Fields Current Layer Props LayerBCs Notes Batch v5 p AN Enable LLG Batch File Descriptors Select Mask File Specifier Mask Es a Lm Position Dependent Parameters File Specifier PosDep NE i Initial Direction Cosines File Specifier Init Ang Ei Boundary Condition Field File Specifier BC Field Ki EI Current Field F File Specifier Field Er El Shape File Specifier Shape Er paj Activate Scripter Accept Changes X Reject Changes FIGURE 114 Batch Page of Input Sheet for File Name Specification Using the Scripting Interface You can use the batch mode scripting interface to write batch files directly using a search or
211. ews Page after Active View Then click Hysteresis Loop Your loop axes should be visible on top Click the Start To Compute button which initiates LLG to relax the magnetization Set up your OGL window as described in the previous example LLG will start the computation The meter tracks the simulation s progress as a percentage of the hysteresis loop points and updates the iteration count The domain pattern changes as the field is swept and the hysteresis loop is updated Click the Views tab The View Polar button allows you to toggle between the polar and angular views When selected the button reads Angular and the data is plotted as a function of angle as a strip chart Click the button again to return to the Polar view Click the Pause Computation button which allows you to use the Arrays feature of the Selector for exploring the numerical values of the parameters Also you can click on points in the polar hysteresis loop to identify their values Notice that when you pause the computation the hysteresis and magnetization status bar at the bottom of the OpenGL window is updated with the values of the magnetization and field at the current hysteresis field point Note that these values are updated only during idle time and not while the computational engine is running the simulation COMMENTS Notice the pinched shape of the rotational hysteresis loop as well as the slight asymmetry near 90 and 270 Observe the change in shap
212. extract proper ties from and click When you click an object its properties are loaded into all three Selector Pages 5 70 LLG Micromagnetics Simulator User Manual Chapter 5 LLG Environment You MUST check the Activate Picker box before EACH selection This allows you to toggle between selector and nor mal interaction with your views OGL SELECTOR SHEET MAIN PAGE Through the OGL Selector Sheet Main Page you can examine position and direction cosine information m Picker Information Basic Arrays Position nm Direction Cosines 0 00 Ma 0 00000 E Activate Picker 0 00 0 00000 0 00 Mz 0 00000 Heff De Energy Density 0 00e 000 erg cc 0 00e 000 E 0 00e 000 0 00e 000 SE FIGURE 29 OGL Selector Sheet Main Page OGL SELECTOR SHEET ARRAYS AND PROPERTIES PAGES Through the OGL Selector Sheet Arrays Properties Page you can examine all array property information Picker Information All Arrays Ei Der Picker Array x component v Componeri Z Component Heff Oe StaticH Oe HetfRot Oe Mask Eden erg cc Hbc Oe grs FIGURE 30 OGL Selector Sheet Arrays Page LLG Micromagnetics Simulator User Manual 5 71 Chapter 5 LLG Environment Picker Information Properties Activate Picker X Component Y Component Z Component _4 Anis Type U2 ergicc KU4 era cc U axis C ergic
213. f t Double Write Positions m fileMovie Write m pLLG gt m pX m nSize sizeof t Double m fileMovie Write m pLLG gt m pY m_nSize sizeof t_Double m fileMovie Write m pLLG gt m pZ m nSize sizeof t Double return TRUE H t BOOL CDatalO WriteMovieFile t Int ii t Double dTime Hcount m fileMovie Write amp m pLLG gt m nHysHcount sizeof t Int CMax m fileMovie Write amp dTime sizeof t Double HLoop m fileMovie Write amp m pLLG m pStatistics m pHx ii sizeof t Double m fileMovie Write amp m pLLG m pStatistics gt m pHy ii sizeof t Double m fileMovie Write amp m pLLG m pStatistics m pHz ii sizeof t Double MLoop m fileMovie Write amp m pLLG m pStatistics m pMx ii sizeof t Double m fileMovie Write amp m pLLG m psStatistics gt m pMy ii sizeof t Double 4 50 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files m_fileMovie Write amp m_pLLG gt m_pStatistics gt m_pMZ ii sizeof t Double HMag and Remanence Resistance and Voltage m fileMovie Write amp m pLLG gt m dHysHField ii sizeof t Double m fileMovie Write amp m pLLG m dHysMRenmlii sizeof t Double m fileMovie Write amp m pLLG m dMhRResistance ii sizeof t Double m fileMovie Write amp m pLLG m dMRvVoltage ii sizeof t Double Angles m_fileMovie Write m_pLLG gt m_pAX m nSize sizeof t Double m fileMovie Write m pLLG gt
214. fields using the Boundary Conditions Field Viewer during the Simulation Phase SPECIFYING PERIODICITY LLG allows you to compute the properties of periodic structures You can specify a three dimensional structure to be periodic along any or all of the three Cartesian directions This is implemented with FFTs Two dimensional simulations can be periodic only in Y The continuous boundary condition affords you the option of modeling a bulk terminated sur face such as a domain wall at the surface In the LLG convention continuous boundary conditions remove the mag netostatic charges from the bottom surfaces of the bottom row of sub elements Therefore the magnetization appears continuous for all Y values below the bottom set of sub elements To implement this scheme LLG uses the 2D inter face discretization scheme as described earlier see page 52 IMPORTANT NOTE For 2D Real FFTs the number of cells in a periodic direction MUST be a power of two Periodic Along X Since the structure has wrap around symmetry along X the magnetostatic fields are periodic along X For three dimensional simulations any or all of the directions can be selected but periodicities are limited to two of the three dimensions at one time Periodic Along Y and Z The structure has wrap around symmetry along Y and Z SPECIFYING CONTINUOUS BC FOR 2D A continuous boundary condition can be set in Y for a 2D simulation which removes the boundary along the bo
215. fter you have completed the Input Phase and started a computation Scalar e g energy density or vector fields and magnetization data are represented There are two dimensional projections bitmap contour and domain and three dimensional views slice surface and input e Bitmap The Bitmap Graph Type displays interpolated color pictures of the data on a two dimensional slice of the structure For scalar data such as energy density the maximum value is by default scaled to red and the minimum value is scaled to blue all intermediate values are interpolated between these colors The color index can be altered using the Color Sheet Table Page For vector data such as the magnetization three panes of bitmap appear my my and m direction cosine components Each bitmap has color coded and labeled axes r g b to orient you The magnetization direction cosines show m m my or mz 0 as black y or m 1 as red m m or m 1 as blue and m e Contour Data are represented in the same fashion as in the Bitmap Graph Type color but instead of a smooth interpolated image contours of constraint m my or mz are plotted By default red indicates positive increments in by default 0 10 values blue indicates negative increments in 10 values in all by default there are 20 contours 95 85 05 4 05 15 85 and 4 95 When you image unnormalized variables such as vector fields the view is scaled to the
216. g Data into LLG Layer Properties NOTE Refer to the material on the Global Page see page 54 for inputting elements that are common to the Global and Layer Props Pages including Material Properties The program treats materials as piece wise uniform You must define the layer specific and the position dependent properties that describe the material or materials A layer is distinct from a discretized sub element or pixel in that for the purposes of this program it is any collection of pixels composed of an independent material A layer is defined as a group of pixels or sub elements that is composed of a single magnetic or non magnetic material that is confined to that layer In three dimensional problems layers are confined to the X Y plane Z normal in two dimensional prob lems layers are confined to X Z planes Y normal because structures in 2D are infinite in Z A layer can be composed of one or several sub elements in the normal direction At present the program can accommodate up to 1024 layers However when the Z discretization is fixed for 3D prob lems the thickness of each layer must be an integral number of the pixel width in Z If you check the Non Uniform box at bottom left of the page this constraint is relaxed and the Z thickness of each layer s pixel need not be the same However for variable thickness layers only the 2D Real FFT method of computation is supported Refer to Chapter 7 Globals for the variables
217. g hys file so that you can display the data at a later time in any manner you wish Limit 1 Limit 2 FIGURE 58 Non uniform Hysteresis Loop Example EI SL Wyster osis Field Configuration fl 00 Wed 00 Wel 00 kro 00008 Me ne 00000 Miis 80000 EM 00 Me 00000 FIGURE 59 Hysteresis Loop View for a Non uniform Hysteresis Loop Please remember to click the Accept Changes button to record your changes to LLG s internal data structures 18 130 LLG Micromagnetics Simulator User Manual CHAPTER 19 Inputting Data into LLG H t and FMR Pages Hysteresis Loop SPECIFYING TIME DEPENDENT H FIELDS The time dependent field component is divided into intervals Each interval is a linear field interpolation between a starting T 1 and an ending T 2 time interval and an optional ac field component between a starting t1 and an end ing t2 time interval The first interval has the starting and ending field points while subsequent sections join with the previous section You can select either a uniform or a non uniform hysteresis loop Hys U and Hys NU Pages a time dependent h field Time Dep H Page or a moving media problem Shields Page These are mutually exclusive DESCRIPTION VARIABLE LIMITS Projection Direction x y z gt mj 10 lt m lt 1 0 T 1 ps Hx hyst H wei 1010 lt Hy nys S0 Hy hyst Hy hyst 1010 SA 41210 Hz hyst Hz hyst 1010
218. g whether or not a particular process is to be activated In this way LLG can run any type of simulation as long as the appropriate files are available at run time As of this release all log param files contain the necessary file elements added to the parameter output file for batch mode processing The file names can be specified on the Input Sheet Batch Page click the Batch tab There are six check boxes You must check the box to signal LLG batch mode only to use the attached file for processing You can enter the names of the files in the edit boxes or search for them by clicking the buttons to the right of the edit fields This provides you with the option of loading an existing file named or specifying a file yet to be created by a future LLG batch run However note that the specified file must have been written by the time the problem being specified is to be run Note LLG writes comments on batch problem variations to the Input Sheet Notes Page page 121 23 188 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation EXTERNALLY CoNTROLLING BATCH MODE PROCESSING When you check the Enable Disable Lck File Check box at the top of the Batch Mode Interface LLG searches for a file with the ck extension that is your batch file is CAMyLLGNSampleBatch llg batch and the Ick file must have the name CAMyLLGYSampleBatch llg Batch Ick When LLG finds a lock file it pauses the calculations LLG checks that this file exists
219. ge energy E in the continuum approximation is given by E dV Vol VB al The exchange parameter A can be extracted from spin wave theory 15 17 which shows that A AM DS 2V where D is the spin wave dispersion parameter S is the spin per atom and V is the volume per atom The spin wave dispersion parameter D is related to the exchange constant J in the Heisenberg hamiltonian by D 2JSa2 where a 3 26 LLG Micromagnetics Simulator User Manual Chapter 3 Introduction to Using LLG is the lattice spacing This relationship is true for spin wave modes along bcc 100 bcc 110 fcc 110 and fcc 100 directions The volume magnetocrystalline anisotropy for uniaxial e g easy axis in y Exy and cubic crystals Ege is given by the following expressions respectively E fdvIk a Ka y E av k PP P rech Kerg where the bulk anisotropy constants for cubic Kc and uniaxial Ku symmetry can be determined from torque magne tometry measurements The energy due to magnetostriction can be included in the expression for the uniaxial anisot ropy by appropriately adjusting the value of the anisotropy constant 20 The surface magnetocrystalline anisotropy energy Exg is given by 1 Ex d t e n where the integration is along the line increment dS in 2 D or a surface increment in 3 D boundary at the film sur faces The symmetry of the surface anisotropy energy was determined by Rado 2
220. gh this page apply ONLY to the cells that BOUND the region Only those properties that you check are applied All others remain unchanged A is intercell exchange B is interlayer Bilinear Exchange across non magnetic spacers C is interlayer Biquadratic Exchange across non magnetic spacers GMR specifies the layer dependent GMR ratio for the layer region inside the defined structure The edit fields at right are for inputting a gaussian random portion to the specified parameter For example if you choose A of 1 05 and use 0 20 the generated exchange stiffness along x will vary cell by cell within the region of interest with the exchange stiffness given by 1 05 0 20 gaussian random variable LLG Micromagnetics Simulator User Manual 22 153 Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETERS SHEET MATERIALS PAGE FIGURE 75 Position Dependent Parameters Sheet Materials Page The properties of this page are identical to those outlined in Chapter 8 Materials 22 154 LLG Micromagnetics Simulator User Manual Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETERS SHEET GRAPH PAGE BC Bitmap Edge Custom Input Custom Graph Main Params Exch Materials Graph Media Pal de Parameter Distribution d Y t r Parameter Selection e Magnetization Un DirX Cub Dir 3X Ex
221. h hollow pyramidal 255 sample problem with solid tip interacting with a sample 259 movies avifiles 195 editing 199 extracting a piece of an existing movie for anew movie 199 interpolating onto a new grid 199 loading and saving 195 page 180 v2 input and output file format of 50 viewing options 197 viewing those with embedded hysteresis or MR loops 197 viewing through standard utilities 195 MRAM system sample of two layer 223 N Neel walls sample problem with 243 non magnetic layers coupling across 115 non uniform hysteresis See hysteresis non uniform notes making 121 number RHS 94 O OGL window splitting 53 orienting graphics 62 output messages 69 overlays arrow 60 color 60 contour 60 P parameters global 79 updating during a calculation 181 182 periodicity 87 Permalloy sample problem for cube 201 permanent magnet fields 86 phi for specifying angle of incident beam 176 limits of 97 picker activating 70 pinning field 103 sample problem with 237 point editor 146 Position 33 position dependent external fields 86 Index 281 visualizing 172 position dependent magnetic fields file type 33 v1 input and output file format of 38 position dependent parameters 147 analyzing properties of graphically 155 applying color for 148 boundary conditions for 164 boundary region exchange for 153 color of mask in imported graphic for 159 defining 152 defining edge for 160 defining in plane exchange for 152 defin
222. hat the program should perform When you compute Hysteresis Loops and the field is changed by a small increment the forcing function to move the magnetization from its equilibrium is very weak Often a minimum of 100 Iterations is sufficient to allow LLG to begin to reorient the spins which prevents a pre mature exit The iteration number is not as easy to select as you might think The approach to equilibrium is governed by several factors including the mesh size and density but the slowest eigenvalue of the system ultimately determines how quickly the solution converges Since LLG is non linear it supports soliton solutions Near the coercive field there is continuous slowing that can make the solution s convergence quite lengthy RECOMMENDATIONS FOR SELECTING CONVERGENCE Check the Convergence and Iterations boxes Set the Convergence to between 0 0001 and 0 0003 and set the Iter ations to between 2500 and 10 000 Solve your problem a couple of times with different mesh sizes Consult your Jg conv file to examine the iteration history or to see how the solutions evolve at low residuals Reset these values so that they work better with the parameter values that you have selected At the maximum Time Step stable results have been found using Convergence 10 and Iter 5000 for systems composed of 5000 10000 10 nm Permalloy sub elements When to Use the Maximum Iterations Convergence Criteria You would typically NOT use the Maximum Iter
223. he LLG equations due to the 1 1 a2 scaling The main problem is in determining what state the spin system should take once that part of the spin system is above the Curie temperature and what happens when those spins above the Curie temperature are cooled below the To This implementation makes the following assumptions e When a spin at T lt T transitions to T gt T save the spin state in memory and set the direction cosine to zero i e no energy is contributed to the magnetic system and spins outside of the Curie rim cannot couple via exchange to those within the Curie rim e When a spin at T gt T transitions to T lt Tc compute the effective field at that point and set the spin state to the effective field direction if Hag H or set the direction to the stored spin direction if Hag H This makes the assump tion that the dynamics for the spin response are fast as the spin makes the transition from being above the Curie 46 270 LLG Micromagnetics Simulator User Manual Magneto Optical Simulations Supplement temperature to being below it This is consistent with Mansuripur s assumption that at the compensation tempera ture and since the damping constant is diverging the spin should be instantly aligned with the effective field Fur ther since the in field critical behavior has ordering about T so long as H gt H it seems sensible to order along the field direction When T Tcompensation Set the direction cos
224. he number of sequential energy increases allowed before the simulation exits You should choose a number greater than one typically two although LLG will accept one When the mesh density is too coarse you can exit LLG prematurely since on a coarse grid the exchange energy density can deviate from its true value Use this option with care to experiment with the precision with which you can determine the energy Since the residuals are known with better accuracy than the energy density they are a better measure as an exit criterion NUMBER RHS LLG computes the effective field rigorously during each iteration cycle Even when you use FFTs the most time con suming part of the computation is finding the demagnetization field This parameter gives you a method for changing how often LLG computes the demagnetization fields during the solution process In most systems solutions are domi nated by the long range low spatial frequency demagnetization field where setting Number RHS to anything but one can be disastrous However if your solution is really proceeding by domain wall motion far from the structure s edge setting Number RHS to three or five will save you a factor of three or five in computing time Experiment with this option carefully keeping in mind that the solution is rigorous only when Numhs 1 which is the recommended value GAMMA MHz This is the free electron gyromagnetic frequency The most typical value is y 17 6 MHz Oe The
225. he sim plest of all hysteresis options 2 Use the slide bars or edit boxes to enter a Maximum External Field which is the maximum field value for the hys teresis loop 3 Enter the Points with the slide bar or in the edit box The distribution of field values will be visible in the OpenGL window The number of field points in the whole loop will be 2n 1 where n is the number defined in the edit box The field values are distributed uniformly between the maximum and minimum negative of maximum vector val ues of the field If you want to determine zero field remanence select an odd number of points along the branch for fields specified as TH max 17 124 LLG Micromagnetics Simulator User Manual Chapter 17 Inputting Data Into LLG Hysteresis Uniform In the following example uniform hysteresis fields are shown in 2D and 3D with no interpolating lines The field specifi cations are Hy 2000 Oe Hy 1000 Oe and H 2500 Oe with the Points 21 The entire hysteresis loop will con sist of 41 field points that are uniformly sampled et CS TT Wysteresis Tei Configuration hyetnr esin ht Configuration He Biel 00 He Del 00 He Del 00 Meis 0 0000 MyMs 00000 MaMe Hej 00 MMe 00000 Me Del 80 We Del DD Me fal OO Met BD Meis BD MiMs amp 0000 Hd 00 MMs 60000 FIGURE 55 Hysteresis Loop Views for a Uniform linear Hysteresis Loop SPECIFYING A ROTATIONAL LOOP You can perform
226. how the magnetization follows the flux lines from the stray field of the external magnets as expected This is due in part to the stray field and in part to exchange This feature adds flexibility to the structures that you can simulate with LLG The use of boundary conditions also allows you to simulate smaller volumes regions of interest within larger structures FEATURES Structure 250 nm x 100 nm x 30 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 25x 10x3 Material Permalloy Relaxation 2D Real FFTs and Rotation Matrices Initialization Uniform magnetization directed 10 off the long axis Boundary Cond Permanent exchange coupled magnets on two faces NOTE In the graphic below the structure has been rotated for a view from the back The magnetization pattern is the top picture FIGURE 136 Magnetization Pattern and Boundary Conditions Fields in 3D Arrows LLG Micromagnetics Simulator User Manual 35 235 CHAPTER 36 Sample Problem 11 Non uniform Hysteresis Loop for a Pinned Platelet This sample illustrates the use of pinning fields in solving micromagnetics problems Pinning fields can be the result of many different physical phenomena For example LLG uses them to capture the effects of antiferromagnetic pinning at an interface spin valves by applying a fixed bias field to a given sub element layer This saves computation time because the pinning layer antiferromagnet need not be includ
227. ick the Start Batch button This activates the process and enables the Pause Calc button As the files are processed the Iterations progress bar and Residuals progress bar track the calculation s progress You can disable these monitors by checking the Enable Disable Update Indicators box While this control is checked the interface is updated As the process runs LLG will also report on elapsed times for the problem and the batch As each problem is run the problem name appears in the topmost black and green file banner Once the computation is LLG Micromagnetics Simulator User Manual 23 187 Chapter 23 Simulation complete the name of the file moves to the Files Processed list control LLG reports batch mode status to the output window at the bottom of the dialog box and concurrently writes this data to a log file llg batch log PAUSING A BATCH MODE CALCULATION To pause a batch mode calculation click the Pause Calc button To resume a paused calculation click the Start Batch button To terminate a problem click the Stop Calc button If there are other files to process in the list the batch mode will begin processing the next problem MONITORING A BATCH MODE CALCULATION While running computations LLG continues to write standard output files If you opted to store a movie or write to a convergence file at a defined number of iteration steps you can examine these files during the batch mode computa tion to see the progres
228. ickness of your structure for the uniform option Further for the uniform option since the structure is discretized into a uniform mesh in Z each layer must contain an integral number of sub elements LLG will not let you proceed unless these criteria are met Enter all of the parameters for the indicated layer To apply a color to the indicated layer to distinguish it from other layers graphically select a color from the drop down color box at the bottom center If you want to make a custom label for the layer click the small yellow arrow at the upper right to access the Material Label menu THE NEXT THREE STEPS MUST BE FOLLOWED PRECISELY OR YOUR INPUT WILL NOT TAKE EFFECT Once you have specified all of your parameters for the indicated layer you MUST click the LOAD LAYER PROP button for your entries to be recorded Once you have loaded a layer s properties the background color of that layer s edit field changes from white to yellow REPEAT steps 2 through 5 for each layer making sure that you click the LOAD LAYER PROP button each time before proceeding to the next layer Once you complete the data entry for all of the layers you MUST click Accept Changes for the input of all of the layers to take effect 14 114 LLG Micromagnetics Simulator User Manual Chapter 14 Inputting Data Into LLG Layer Properties SPECIFYING THE Au INTERLAYER LLG uses the convention that the exchange stiffness between adjacent cells can be mo
229. ie Samplei PD Sample2 1 I lg v2 O workttestiSample2 llg movie Sample3 Lllg v2 O workttestisample3 Io movie Sample4 I Ma v2 0 wwork testisample4 Io movie Sample4 Int i T la v2 workttestiSample4 Int lig movie Sample5 lg v2 0 worktestiSampleS lig movie Sample6 Y Wg v2 0 worktestiSample6lg movie Sample7 lg v2 0 worktestiSample lig movie Sample EU 1 Sample GS Sample GS 4 untitled E Lllo v2 O workuntitled lg movie BatchTest E Mg v2 0 wwvorkBatchTest lo param BatchTest1 E Mig 2 0 work BatchTest lig param Douwe Field 1 1 Samplet I Ilg v2 0 workttestiSamplei lig param Sample14 Odeg Samplet 5 E Tuer O workitest Samplet 5 llg_param Sample1 PD EMlg v2 Oy workiDouwe Field jo param I Ma v2 0 wworkttestisample1 4 Odeg lg param Eg v2 O wworkttest sample1 PD Io param Sample2 1 T ll v2 O workttestisample2 lig param Sample21 lg v2 0 worktestiSample21 lig param Sample3 Tuer OJworktestiSample3 llg_param Sample4 l EMlg v2 OJworktestiSample4 lig param Samples 1 Tuer OJworktestiSamples llg_param Samples 1 Lllg v2 O wwork itestiSample6 llg param Sample i Ellg y2 OJworktestiSample lig param IHlg v2 0 workttestiSample7 GG Io param lg v2 0 worktestiSample1 4 Odeg lg movie klg v2 0 workttestiSamplet PD lig movie RENG OJworktestiSample _EU Wo movie Ellg y2 D workttestiSample GS lig movie I Ma v2 0 tweorktestisample GS 4 lg movie LLG Micromagnetics LLG Micromagneti
230. ield Hx og Hy 0 Hz 0 wl ob 0 0 Main Control Material C 14 Clear FIGURE 73 Position Dependent Parameters Sheet Parameters Page This page is for specifying position dependent material properties as outlined in Chapter 7 Globals or Chapter 14 Layer Properties The one difference here is that you must check the properties that you want to change If a box is CHECKED then that property WILL BE CHANGED if a box is UNCHECKED then that property WILL REMAIN AS SPECIFIED e Check the IP box adjacent to the exchange parameter which indicates that you want to modify only the in plane component of the exchange parameter e The edit fields are for inputting a gaussian random variable to the properties that you specify For example if you choose a saturation magnetization of 800 and use 100 the generated magnetization will vary cell by cell within the region of interest with the magnetization given by 800 100 gaussian random variable e Click the Clear button to reinitialize your input configuration e Click the Material button to access the database for selecting parameters for the materials edit fields e Use the drop down color box to select a color to apply to the region You MUST also check the CO box in the Graphics Control for the color to appear in the OGL window once you have applied the properties to the region Click the OGL Props tab then click the Modes tab to access this feature 22 15
231. ields m rrrruuunnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnevevevevennnnnnnnnnnnnnnnnner Specifying Shield te vi LLG Micromagnetics Simulator User Manual Table of Contents Response to Model atan Media Charge 136 CHAPTER21 nputting Data into LLG Mask Editor sensannnnevnnnnnnnannnnnnnnonnnnnnnvvnnnannannnnnnenevennannner 139 ACCES MMS EE 139 Defining a Mask Shape cio ia veden bien cd 139 Mask Editor Sheet Main Page ooooococonncccnnncccnnoccccnncccnnnncc conca cr 140 Specifying Mask Properties Option one 141 Color GOdinNgus EE 141 Determining if the Demagnetization Edge is Ulnspected AAA 141 Reading and Saving Mask Files eee ennr nennen nennen entes intr nns ettet siste sais trtn ennt 141 Mask Editor Sheet Bitmap Page AA 142 Specifying Mask Properties Option Two 142 Mask Editor Sheet Edge Page sinsin teada ada aial adai aaia ladaa i baia aaa 143 Mask Editor Sh et Super Egg rererere eau ii eie eode eer adaa aada Skad Re a ansatte 144 Editing the Graphic Coordinates necat n diete ette eae due e uL qe cms gre ep de nnne dat 146 CHAPTER 22 nputting Data into LLG Position Dependent Parameters 147 Basis Steps for Establishing Position dependent Parameters cccccccceeeceeeeeeeeeeceaeeeeeaeeeseaeesseneeeseeeesenneees 148 Defining an Area of Interest with the Drawing Tool 148 Selecting a Color for the Area of Interest sssssssssssssssssssssse eene nennen senten e
232. ile In this way you can cap ture transition states if your baseline field points are too coarsely separated COMPUTATION PAGE Ve f 3 Rotation Matices 111 E Euler ati auss Seide Stable tli Sequential Pe rane M Use Dual Processors 1 000e 004 Iv D E E e iv zl EMBA AY FIGURE 109 Simulation Sheet Computation Page You can update computational parameters such as the Time Step and the Convergence criteria during a calculation As in v1 you cannot change a major computation mode such as going from an energy method to an FFT method Please see Chapter 10 Input Sheet Computation for a complete discussion of the parameters on this page LLG Micromagnetics Simulator User Manual 23 181 Chapter 23 Simulation FiELDS PAGE Main Views Movies Notes Comp Fields B Probe Ws e External Uniform Applied Field Hx De SS Ale pay EN 0 0000 10000 10000 Hy De e et 0 0000 10000 10000 Hz De AUI det I ALI 0 0000 10000 10000 m Pinning Le Exchange Bias Field ESTE e a VE 0 0000 10000 10000 H IIe QS 0 0000 10000 1 Ha eee ace 0 0000 10000 10000 LoadHPin gt Laver to Pin 1 m Optionally Remove Effective Field Components Check ONLY To Remove Demag Exch Anis H k20 Periodic Field Correction Status 3D Complex FFT Hx De Hy De Hz Ge Accept Changes zie JC Reject Changes FIGURE 110 Sim
233. iles that contain the direction cosines for every element in the array If you start LLG by opening a lg param file using the Input Params button the prefix of the file you load will be appended by the llg dom suffix and the output file will be written Use this page if you wish to specify another name or to load an existing configuration to seed a new computation e Loading Loading these angles from a file allows you to start with any predefined magnetization distribution or to continue a computation that may have been terminated prematurely If the loaded file does not have the same discretization as the problem you wish to run you will be prompted to indicate whether or not you want to interpolate the old data onto the new grid In addition you can explore the effect of changing input parameters or other input specifications on a particular equilibrium magnetization structure e Saving Saving these angles to a file which LLG requires allows you to record the final equilibrium magnetization distribu tion By default these angles are saved for each computation The default name is either the input prefix of the loaded LLG file or the loaded lo param ASCII file with an lig dom suffix If an alternative name is desired this page confirms the new name If no name is selected the program prompts you for an acceptable name before you enter the simulation phase of the computation CONVERGENCE DATA LLG CONV These ASCII files can be
234. in the Position Dependent Parameter Sheet the Image Color Table and Apply Params features apply only to that Sheet The only feature relevant to making a mask is specifying the black portion of the image 21 142 LLG Micromagnetics Simulator User Manual Chapter 21 Inputting Data Into LLG Mask Editor MASK EDITOR SHEET EDGE PAGE Main Bitmap Edge Super Egg Em Model 1 Af d B Model 2 A B x d C d 2 D x d 3 0 0 Distance nm 20 0 Edge Magnetization E change Damping Mag Edge A B P D Pe Le Model E 2 r d 0 Model chEdge A B E D Pit Model Pat 11 nml Edge Roughness Floughen Edge Amplitude nm 20 Wavelength nm 50 Edge Rectangle Specified FIGURE 66 Mask Editor Sheet Edge Page You can specify periodic Edge Roughness on the Edge Page 1 Specify which layers you want to mask on the Main Mask Editor Page and whether you want to toggle turn on or turn off the region internal or external 2 Draw a region with the Drawing Tool see page 139 3 Right click on the graphic and select Specify Selected Region for Edge Property Effects from the pop up menu 4 Checkthe Roughen Edge box and specify the Amplitude and Wavelength of the roughness in nm in the edit boxes 5 Right click on the graphic and select Fill Selected Region from the pop up menu This Page also appears in the Position Dependent Parameter Sheet the Edge Magnetization Exchange Dampi
235. ine along the effective field direction instantly For all other situations the equation is solved directly Also note that when the gyromagnetic frequencies are identical for the two spin systems that the system gyromagnetic frequency is fixed and constant INITIATING A MAGNETO OPTICAL CALCULATION IN LLG All magneto optical calculations in LLG must be done using position dependent parameters Please see the LLG Micromagnetics Simulator User Manual for a complete description of initializing computations for position dependent parameters Once a problem has been initialized you may click on the MO page to activate the main input page for specifying magneto optical parameters shown below Params Exch Materials Graph Media Bitmap Edge CustomMO MOT Graphs n Function 1 Y a 1 T Tc b T Tc SE Se Function 2 Y a bT c1 2 d1 3 T lt Te pa P Option 3 Read MIT KIT and A T From File LX Functions Save MO Params Read MO Params 0 0 0 0 Main BC Function 1 co LIE Function 2 Function Fonction Z y oe LLL 0 Function 1 Function 2 Function 1 Cc o C o e ol o o eb igh ER 7 0 0 Function 2 0 MO fromFile gt Fenr raame EB He Au Exchange Aij 4 amp up amp down 2 m Controls A B C 1 Interface Exchange 1 Bilinear Interlayer 1 BiQuad Interlayer DoMO Calc 2 Spin Syst jet Temp Font Read Temp Time Step
236. ing options through the Movie Player e The right facing triangle Plays a movie from the beginning to the end e The square is the Stop button e The double lines are the Pause button e To control the speed enter the length of time you want each frame to run in the Speed edit box The default is 10 second frame e Use the Frame slide bar or edit box to set the movie s frame manually e The Progress edit box tracks the percentage of the movie that has been played This provides you with informa tion on the number and progress of frames in a movie MR AND HYSTERESIS LOOPS You can recursively divide the OGL screen for multiple views of your data e For data sequences that include hysteresis loops or MR loops that are embedded in the movie use the Set View Hys Loop and Set View MR Loop buttons to activate the appropriate loop in the active clicked OGL View e Click the Set View Angle button to return the view back to the direction cosines of the magnetization which is the default e lf the hysteresis loop is rotational you can click the Ang or Polar button to define the display the polar loop e f you have computed an MR Loop you can display the data as the change in resistance dR or the normalized change in resistance dR R by clicking the appropriate button INTERACTING WITH THE DATA Once a movie has finished playing or while a movie is paused you can interact with data through the Selection Page as described in Chapter
237. ing with an imported color map 159 demagnetization edge for 151 file type 33 GMR 153 input prerequisites for 147 input sequence for 74 specifying bitmap for mask 158 specifying materials with 154 specifying random fill for 151 tiling example of 157 turning cells on or off 151 using the random number generator for 151 v2 input and output file format of 46 viewing 150 visualizing 150 with 1 layer structures 147 properties of objects in graphics determining 70 protection key installing 22 protection key driver installing 22 R random fill applying to position dependent parameters 151 random fraction limits of 97 random initial condition 101 random number RN seed 94 151 using with media 156 random variable gaussian 101 152 153 155 relaxation method 90 energy slower 91 time faster 91 release notes 17 rendering properties 62 residuals 165 display during simulation 95 visualizing 171 S save conv details 76 scripting interface for batch mode processing 189 sensor fields 86 serial number 22 shielded external field Index 282 visualizing 172 shielding micromagnetic elements from external fields 135 shields attributes 135 computing cross track response 136 mode that supports images of the charges 135 parameter limits of 137 specifying properties of magnetic medium 136 simulate a movie 186 simulation page 165 residual 165 status indicators 165 update e 165 simulation volume parameter limits of 75 requi
238. into LLG Fields The Fields Page allows you to specify any orientation of external fixed fields in which to minimize the magnetization of the sample which is above and beyond those provided by the boundary conditions currents and hysteresis fields The external and pinning fields persist even if a hysteresis field is applied This allows you additional flexibility in defin ing running and interpreting problems and their solutions External fields can be oriented uniformly along any direction Pinning fields can be applied to any plane in Y of sub elements where the magnitude of the orientation can be inde pendently selected for each pinned plane In this way a computationally efficient method allows coupling to antiferro magnetic substrates or to any other desired configuration EXTERNAL APPLIED FIELD H is the X component of the external field Hy is the Y component of the external field H is the Z component of the external field PINNING FIELD H is the X component of the pinning field H is the Y component of the pinning field H is the Z component of the pin ning field PINNING A LAYER You can pin a layer by entering a number into the Layer to Pin edit box single discretized pixel layer to pin in Z or by clicking the arrow keys on the scroll bar You can scroll through the pinned layers to make changes You MUST click the Load H Pin button for your changes to take effect Please remember to click the Accept Changes button
239. ion grain to have identical properties When this is selected the parameters random number generator randomizes only by tile not by cell 22 156 LLG Micromagnetics Simulator User Manual Chapter 22 Inputting Data Into LLG Position Dependent Parameters 6 Once the data is specified click Tile The Surface to see how your space can be filled 7 If you are satisfied with the distribution click Fill Parameters to set the parameters otherwise click Clear The Tiles and try again A simple tiling example follows Refer to Sample Problem 20 Media for an example Input Configuration Active Moments FIGURE 78 Position Dependent Parameters Sheet Simple Tiling Example LLG Micromagnetics Simulator User Manual 22 157 Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETERS SHEET BITMAP PAGE Click the Open button to load files listed in the menu above Click the Flip button for the options listed in the menu above Click one of the color boxes in the Image Color Table for the options listed in the menu above FIGURE 79 Position Dependent Parameters Sheet Bitmap Page 22 158 LLG Micromagnetics Simulator User Manual Chapter 22 Inputting Data Into LLG Position Dependent Parameters SPECIFYING A MASK OR PROPERTIES WITH AN IMPORTED IMAGE A second option for specifying mask properties is to import a bitmap jpeg or targa file that you have
240. ion Sheet Clock Page provides you with a clock and a calendar LLG Micromagnetics Simulator User Manual 5 69 Chapter 5 LLG Environment OGL INFORMATION SHEET CALCULATOR PAGE fo E Disks 17 Output E Clock M Calc FIGURE 27 OGL Information Sheet Calc Page The OGL Information Sheet Calc Page provides you with a calculator OGL INFORMATION SHEET DEMAG FIELD CALCULATOR The OGL Information Sheet Demag Page provides you with a demagnetization field calculator for uniformly magne Demag Coupling Tensor 0 53879 0 00000 0 00000 Api 0 00000 0 27839 0 00000 0 00000 0 00000 0 18282 mo Epi 150 out Ez oi il cate FIGURE 28 OGL Information Sheet Demag Page tized structures bounded by cartesian planes OGL SELECTOR SHEET The OGL Selector Sheet allows you to probe the properties of the OGL window You can access all array values such as magnetization and field and parameters such as magnetization and position There are three sub pages Main Arrays and Properties You can toggle between the pages by clicking the appropriate tab To activate the selector picker check the Activate Picker box at the upper right When you position the cursor over an OGL window the arrow cursor changes to a target cursor You can select objects only in 3D Slice Graph Type using Arrow Cones or Vertex Cones To select an object position the cursor over the object you wish to
241. ion and reapply the distribution to view 13 Repeat steps 1 12 for each area to which you want to apply position dependent parameters LLG Micromagnetics Simulator User Manual 22 149 Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETER SHEET MAIN PAGE BC Bitmap Edge Custom Input Custom Graph Materials Graph Media Main Params Exch de Position Dependent Parameter E ditor Fill Mask Region Layer Fill te nal e This Layer External All Layers m Mask Properties Su Set Params Layer Range Tum Cells On Lower 1 Tum Cells Off Upper 1 r Random Fill e Uniform Fill C Random Fill Fraction 0 5 Pos Dep File L Read File Save File Read Mask m Seed Random Number Generator Dot a The Demag Edge Is Unspecified Accept Changes X Reject Changes Close PosDep Tool Pos Dep Views gt amp Main Control Input Array Cell Positions Magnetization Uniaxial 2 Anisotropy Uniaxial 4 Anisotropy Cubic Anisotropy Surface Interface Anisotropy Exchange Coefficient X Exchange Coefficient Y Exchange Coefficient 2 AMR Resistivity Polarization Uniaxial Axis Along X Uniaxial Axis Along Y Uniaxial Axis Along Z Cubic Axis 1 Along X Cubic Axis 1 Along Y Cubic Axis 1 Along Z Cubic Axis 2 Along X Cubic Axis 2 Along Y Cubic Axis 2 Along Z Hpin X Hpin Y Hpin
242. iration date of the program As shown below you should see Success written in all four edit fields at the lower left A Version 2 key will display a 2 in the Key Version edit field If your key dis plays a 2 you can run both v1 and v2 of LLG If your Protection Key fails contact LLG Micromagnetics immedi ately e LLG Read Protection Key Attributes EN Today s System Date r Last Execution Date ES 2001 Year 2001 Month a Month Day 5 Day 8 Hour Hour Minute 8 Minute 8 Coded Query Resonse Pairs r Expiration Date Initialization Success Year 2101 Query Pairs Success Month Expiration Date Success Day Last Run Time Success BITS TIT Key Version v2 0 Exit FIGURE 1 Keyscan Menu for Probing Protection Key Attributes INSTALLING LLG WITH WINDOWS 2000 oR WIN xP For installing LLG on a computer with Windows 2000 or Win xP 1 Make a new directory in your LLG directory called WIn2000Files and move the following dll files into the Win2000Files directory e Gdi32 ddll e Glu32 dll e OpenG132 dll e Kernel32 dll User32 dll e Ole32 dll e Msvcp60O dll On Win2000 WinxP systems you may experience graphics irregularities This stems from Microsoft s graphical optimi zation algorithms which may circumvent the OpenGL drivers If you experience problems right click on the display desktop window and select properties Choose settings and click on the
243. is loop is a plot of two scalar variables H and M The magnitude of H is given by the scanned field point dotted into some direction and the value of the magnitude of M is that magnetization dotted into that same direction The Projection Dir edit fields are for specifying the x y and z components of the direction cosine of which you want to obtain the hysteresis loop By default the x direction is specified Therefore you can scan the field along one direction and acquire a hysteresis loop projected along another if you choose SPECIFYING A TiME DEPENDENT FIELD To specify a time dependent field 1 You MUST first check the Time Dep Field box to enable time dependent fields Specify the time interval in the Time Interval Specified edit box starting with the first Set the specified interval s starting and stopping fields in the T 1 ps and or T 2 ps edit boxes Specify the Time Interval Steps Each Time Interval Specified must have a corresponding Time Interval Steps 5 Specify the Time ps Step which MUST be the same for each interval THE NEXT THREE STEPS MUST BE FOLLOWED PRECISELY OR YOUR INPUT WILL NOT TAKE EFFECT 6 You MUST load the field section by clicking the LOAD SECTION button Each section must be loaded since the same controls are used both to examine and to modify the field values 7 Increment the Time Interval Specified counter and enter the data for the next field sector following steps 2 through 6 8 Click
244. ition the value of Ms at T near Tc can greatly change the properties of the nucleation in that a steeper rise in Ms near the Curie temperature can lead to inversely magnetized sub domain formation in the demagnetization field of cells local to the Curie rim Be sure to experiment with your parameter selection prior to initiating a problem in LLG by examining the size and shape of Ms and Hc near Tc LLG Micromagnetics Simulator User Manual 46 275 Magneto Optical Simulations Supplement Main Params Exch BC Bitmap Edge de View Temperature Dependent Parameters x Mi T 0 1000 M2 T 0 800 Ms T 0 800 KiT 0 1000 A T 0 1 05e 006 Scales Materials Graph Media Custom MO MD T Graphs 0 0 Normalized Temperature T T c 1 0 Magnetization 2 Anisotropy Minimum Maximum 8 0000e 002 Preview Temperature File Magnetization 1 Exchange Alpha eff Gamma eff Coercive Field 0 0000e 000 Frame FIGURE 155 Position Dependent Sheet MO T Graphs Page 46 276 LLG Micromagnetics Simulator User Manual Magneto Optical Simulations Supplement SAMPLE PROBLEM Some sample problems are provided to illustrate LLG s basic functionality for performing MO calculations These prob lems are based on content from Mansuripur s book on MagnetoOptical Recording The essential problem is to examine nucleation in the region around a gaussian beam that heats the specimen above T an
245. ition can be selected to provide a head start for the iteration procedure When the largest residual of a single value of MxHa M Har decreases below a convergence minimum the iteration process is stopped The convergence min imum for terminating the calculation is the value of the largest relative change in the largest component of the direction cosines This value will depend upon the size of the mesh and on the closeness to a magnetization change such as the reorientation close to the coercive field in a hysteresis loop calculation Equilibrium domain wall configurations determined from this energy minimization scheme agree extremely well with configurations determined by solving the Landau Lifshitz Gilbert equation directly 23 For equilibrium configurations for uniform systems the more economical energy minimization scheme can be used to determine equilibrium configurations For more complex systems or in the presence on grain boundaries which may serve as nucleation sites the solution of the Landau Lifshitz Gilbert equation is necessary for accurate results 18 19 The content of this section has been extracted and slightly altered from the original version published in a section of Micromagnetics of 180 Degree Domain Walls at Surfaces M R Scheinfein J Unguris J L Blue K J Coakley D T Pierce R J Celotta P J Ryan Phys Rev B43 4 3395 1991 1 W F Brown A E LaBonte J Appl Phys 36 4 1380 1965 A E LaBonte J
246. ivergence of M in the presence of current there is the possibility to exchange angular momentum i e like in the layered case between non aligned spin moments Layered system spin torques Current Page and Global spin torques cannot be used at the same time Since this feature is experimental this parameter in not saved in the param eter file hence you will need to check it each time you want to use it LLG Micromagnetics Simulator User Manual 7 81 CHAPTER 8 Materials Inputting Data into LLG LLG material parameters can be saved and loaded into a database The Input Data Sheet Materials Page is shown on the following page The parameters are summarized below DESCRIPTION Saturation Magnetization M emu cm VARIABLE LIMITS 0 0 lt M 108 O 2 Uniaxial Anisotropy Kyo erg cm 1010 lt Kuo 1010 O 4 Uniaxial Anisotropy Kya erg cm 1010 lt Ka 1010 Cubic Anisotropy K erg cm 1010 lt K 10 Exchange Stiffness A uerg cm 10 A 10 Surface Anisotropy Ks erg cm 1010 lt K 10 Resistivity p uohm cm 0 01 p X106 Anis Magnetoresistance AMR 96 0 0 lt AMR S 1 0 Anisotropy Type KType U C or Both Easy Axis Direction KDir X Y Z or Any Easy Axis Direction Cosines Axy z 0 0 S A y X 1 0 From the Materials Page you can load the pre coded properties of Fe Co Permalloy and vacuum into the
247. ize to define the largest time step possible FFT METHOD There are two FFT Methods You can unfold the symmetries in 3D to implement a true 3D real algorithm but it is difficult The advantage is that multi thickness layers can optimize for the number of cells which always translates into faster calculations The danger is that the non uniform treatment of the out of plane part which is the driving force to torque the in plane part The BEST computations will use cubic pixels since there is no self field biasing of any kind However for most systems except those of theoretical interest it is not pixel efficient enough e Check the 2D Real FFT Method button if your structure has fewer than five active layers in Z This method is fast est if the number of pixels or elements in X and Y is a power of two The 2D Real FFT Method uses slices of real two dimensional FFTs to perform the convolution in three dimensions If your array is not a power of two it will be padded In the case that the layers are not the same thickness use 2D Real FFT Method in each plane and sum It is all orders correct with no approximations This uses the Intel MKL FFT which is power of two based and therefore is best for 2 pixelated grids otherwise they are zero buffered IMPORTANT NOTE When you use periodic boundary conditions with the 2D Real FFT Method you must use a discretiza tion that is a power of two in the direction of the periodicity e Check
248. l E RRR Re er Re Re Re eidem da da n mami tiic mnl ga RRR e dete ke EERE EEL ELE EE EE EEE EEE drm mra man RA O O LAE KE dni dod oie dre hr todo od hod A AAA aa RRR RR RRR dein de inde in de tnim trim iin inen innen dim de im de Imam RR jn Pando qo idend rtm ara a ER DREES MB RAHA DA ch rh hh c nn fe EE en ee en hh EET JOE DIR at cb ea eet a et ot ot p en pe b t pt op ot op ot Y DD eff fe ee e dd Gat eh eh ot ot to ot bet et bet bee bbb AP R A A nn fn ee NY AAA AAA e e e e a e a a S O E MH PR nt Pen en en e e 9 e OR e e hh bh aE ot ch Dp c AE e e tet Rt tp pf e e e a do oa ot at ot ot to ao at ad od at ot dt dt EE MASS AS ete eee V7 dr a7 dr ee e MACC EE de Ve de entren mdr n Ian aman n ee d ECKER SE EE EE E e ee e AR RE Re Reece enero ere eee REMAN RAR Rate d rd tdm enna da ee RARARA RAR Ramee eee d dm l a Rete eee eee Li 747 6747 47 d 47 47 d 67 aman eds CA et ee ei eee non A A L H H 1 H 1 H 1 H t H T 1 H t H t t H t 1 t 1 H t t t H H t t H H t t t x A D FIGURE 139 Magnetization Pattern in Arrows Graph Type LLG Micromagnetics Simulator User Manual 37 241 CHAPTER 38 Sample Problem 13 Bulk Terminated Bloch Wall in Fe This sample problem illustrates the formation of Bloch and N el walls at or near a surface region local to a domain wall in 2D structures The sample solves the micromagnetic st
249. layer MRAM system of a rela tively hard layer Fe and a relatively soft layer Permalloy The two layers are antiferromagnetically coupled through their mutual demagnetization fields There is no interlayer coupling that is they are exchange isolated by an ultra thin layer of a non magnetic and non coupling material INPUT SHEET MAIN PAGE 1 Initiate an LLG computation 2 Enter the dimensions of the problem X nm is 250 nm Y nm is 100nm and Z nm is 20 nm 3 Enter the discretization for the problem N is 25 Ny is 10 and N is 2 4 Check the Layers box to establish a multilayered problem INPUT SHEET LAYERS PAGE 1 Click the Layer Props tab 2 Atthe top right of the Layers Page use the arrow keys or the edit box to indicate N Layers of 2 that is a two layer problem Then you must specify the properties of each layer 3 Set the Layer to 1 the first or lower layer 4 Setthe Layer T nm Thickness to 10 for layer 1 5 Click the Material button at bottom center Select Permalloy for the material and click Accept to return to the Lay ers Page The properties for Permalloy should be loaded into the edit fields for the material properties of layer 1 6 Use the color button at the bottom center to select green The color should appear in the box on the button 7 Click the LOAD LAYER PROP req button to register your entries for layer 1 You must click the LOAD LAYER PROP button after you enter each layer s propertie
250. lid Pyramidal MFM Tip uunnnvnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnennnnnnen 253 Input Sheet Main Page enim eee bte e e 253 Input Sheet Gomputation Page EE 253 Input Sheet Globals Page and Materials Page eene nennen nenen nnn nnne nen 253 Input Sheet Initialize Le ii e rete reke ei d eet 253 Input Sheet Boundary Conditions Page 253 MER ssepe m 254 COMMONS EET TDI EET Em E 254 Features EE EE 254 CHAPTER 42 Sample Problem 17 Hollow Pyramidal MFM Tip rrrrrnnnnnnnnnnnnnennnnnnnnnnnnnnnnnnnnenner 255 Input Sheet M in Page irit etie ce ente TE 255 LLG Micromagnetics Simulator User Manual xi Table of Contents Input Sheet Globals Page and Materials Page 255 Input Sheet Boundary Conditions Page 255 Input Sheet Computation Page 255 Input She t Initialize Page eet poe A A AE eio edu enr EA lanes ae Bae s 256 COMME atra Podere tele Idle ua reed brodo Eee eb viv eet IE tae bete aeu ue bu edite ater ad depend 256 aig LC 256 CHAPTER A3 Sample Problem 18 Sample MFM Tip Interaction osuere 259 Input Sheet Main Page uie Aere AA icd et p eps edu gd d deoa 259 Input Sheet Computation Page 259 Input Sheet Globals Page and Materials Page sse ener 259 Input Sheet Fields Page AANEREN 260 Input Sheet Initialize Page cassie tercia t idee eden mec kadett hea oa Ds 260 i MEisise ic IR 260 GOMMERS iria
251. like into this field but you must enter something e You will be prompted for an install directory Use the NT interface to select a new directory or use the default The files will automatically be installed into this directory INSTALLING THE PROTECTION KEY The Protection Key must be installed directly onto the parallel printer port on your computer s backplane If you have a parallel printer that is connected to this port simply install the Protection Key between the parallel port and the printer cable Printer functionality will not be impaired INSTALLING THE PROTECTION KEY DRIVER 1 The program for installing the Protection Key Driver can be found in the LLG Micromagnetics program installation directory Double click on the folder named Rainbow Then double click on Setupx386 exe You must be logged on as the System Administrator to install the driver 2 A set up window with a function menu at the upper left will appear Click on the functions menu and select Install Sentinel Driver 3 You will be prompted for the path to the drivers which should be correctly determined The drivers are located in the i386 subdirectory in the Rainbow folder Choose OK 4 Then reboot your system 2 22 LLG Micromagnetics Simulator User Manual Chapter 2 Getting Started 5 Test the Protection Key by double clicking on keyscan exe in the llg directory Click on the test button and observe the current date last run date and exp
252. linear integro differential equations LLG provides several con trol parameters to help you specify how accurate a solution your problem requires The outcome from setting the con vergence criteria too coarsely can be severe that is you might get the wrong coercive field or even the wrong final magnetization state When you are performing an important problem bracket the solution by repeating the calculation with a range of exit criteria to test the robustness of your solution 23 184 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation GUIDELINES FOR SETTING UP PROBLEMS AND DECREASING COMPUTATION TIME The following are essential features for solving a real micromagnetics simulation problem Know your problem Simulate only the part of your system that is relevant You need not simulate each and every part at once Start small Model a subset of your problem If you have a large problem establish the key features by constructing a miniature version of your problem Small problems run quickly and can be visualized and tested interactively Find the appropriate settings convergence time step and mesh density for your miniature model problem Do not simulate a hysteresis loop Run the zero field problem first Find the coercive field manually increase the statically applied external magnetic field Knowledge of the coercive field allows you to optimize the hysteresis loop sampling later Watch the problem evolve inte
253. ly Check PosDep Box and Commit Size Global Data Size Layers c Begin Simulation Check Layer Box Begin Simulation Commit Size V Pos Dep V Masks Begin Simulation Begin Simulation y Masks Begin Simulation FIGURE 33 Input Data Strategy When LLG initializes its parameter arrays and allocates memory first it fills in the layer parameters with globally speci fied parameters and then it fills in the layer specific properties Once layers have been created if position dependent parameters are required LLG uses the layers properties to initialize the position dependent parameters This allow you to create a problem with layered properties and to make only one parameter position dependent LLG Micromagnetics Simulator User Manual 6 73 Chapter 6 Inputting Data Into LLG Main IMPORTANT NOTE In v2 of LLG you MUST check the Layers box under Structure Properties BEFORE you input lay ered or position dependent parameters Checking the Layers box gives you access to the Layer Props Page When you apply position dependent parameters to a 1 layer structure you MUST specify it as 1 layer on the Layer Props Page In this case the layer thickness defined on Layer Props Page and the thickness of the structure defined on Main Page are equal After you have input layered properties the PosDep box under Structure Properties is enabled allowing you to configure a position depe
254. ly is 2 Rd gt gt 2kgTa l q ap yM x Heff aya X M x Heff YM xo YM AVA Uspin Torque S a a and y can be adjusted independently to provide flexibility Hence both the gyromagnetic and damping terms are rig orously retained You can solve the equation by using FFTs O N fast with all magnetization vectors rotating in uni son The rotations are performed using a simple Euler O 2 integration method a rotation matrix unitary transformations in a reversible second order in time scheme O 2 or a Hamming Predictor Corrector method O 4 The additional terms on the RHS of the LLG equation are the Langevin term at finite temperature T for gaussian ran dom uncorrelated variates o Orms 1 at time step At in volume Av in the Stratonovich sense and the spin torque term see Current Chapter ENERGY SOR The over relaxation parameter is used only in the LLG Energy Relaxation method LLG uses a standard successive over relaxation scheme to speed up convergence in one point searches An Energy SOR parameter of about 1 11 which is the default value is nearly optimal for many systems Experiment with the SOR slide bar and edit box to mod ify the parameter and to increase computation speed A SOR parameter of 1 0 provides a straight relaxation You can adjust the overrelaxation parameter using the slidebar or the edit box directly when Energy Slower has been checked ENERGY SEARCH SEQUENTIAL OR RANDOM For the one point at a
255. m N is 40 and N is 10 INPUT SHEET MATERIALS PAGE 1 gt DN Click the Materials tab Select Permalloy Click Accept This loads the parameters for Permalloy into the edit fields in the Globals Page Click the Globals tab then click Accept Changes on the Globals Page before you exit This records Permalloy in the file name field in the Main Page INPUT SHEET BOUNDARY CONDITIONS 1 3 Click the Boundary tab The structure runs infinitely in the Z direction In a domain wall the magnetization of the boundary conditions is fixed by the domains on either side of the wall Enter the domain orientations on either side of the wall into the Boundary Conditions fields Enter 1 0 in the M edit field for the Left X 0 boundary condition and enter 1 0 in the M edit field for the Right X N boundary con dition These are the values of the direction cosines on the left and right sides of the structure LLG will not change these values during the energy minimization process The structure is now assumed to be infinite in the X direction too bounded on the left by Z directed magnetization 1 0 and on the right by magnetization 1 0 The interior sub elements adjacent to the boundaries will be exchange coupled to each boundary condition direction cosine If the boundary conditions provide a component of the magnetization perpendicular to that boundary at each interior point the magnetostatic field will be computed and stored due to
256. malloy s parameters into the database fields 5 Click Accept This returns you to the Globals Page loads the parameters Permalloy into the edit fields in the Glo bals Page and records Permalloy after Properties Of 6 Click the Accept Changes button which exits you to the Main Page and loads Permalloy into the edit field at the top INPUT SHEET COMPUTATION PAGE 1 Click the Computation tab 2 Select Energy Slower 3 Click Accept Changes to exit this page INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Select Uniform X Direction 3 Click Accept Changes to exit this page No other modifications to the default settings are required to run this prob lem LLG Micromagnetics Simulator User Manual 28 207 Chapter 28 Sample Problem 3 Uniform Hysteresis Loop for a Magnetic Platelet INPUT SHEET HYSTERESIS U PAGE 1 Click the Hys U tab 2 Click the Uniform box to activate the uniform hysteresis option Using the slide bar or the edit box set the field in the X direction Hx Oe to 1000 Oe 3 Enter 11 into the Points field Since an odd number of field points was selected for a single hysteresis loop field sweep Max Min the zero field magnetization will be computed The field values will be displayed in the OpenGL window Refer to the legend toward the right of the OpenGL window for the color coding The triangular waveform is indicative of a linear field sweep 4 Enter 1 00 0 00
257. ment the Field Section Specified counter and enter the data for the next Field Section following steps 2 through 5 above REPEAT this process for each Field Section Once you have entered the data for ALL of the Field Sections specify the Loop Direction The hysteresis loop is a plot of two scalar variables H and M The magnitude of H is given by the scanned field point dotted into some direc tion and the value of the magnitude of M is that magnetization dotted into that same direction The Loop Direction edit fields are for specifying the x y and z components of the direction cosine of which you want to obtain the hyster esis loop By default the x direction is specified Therefore you can scan the field along one direction and acquire a hysteresis loop projected along another if you choose Click Accept Changes when you have entered data for all of the sections or your data will not take effect Reading and Saving Hysteresis Input and Output Files You can create a field file for generating hysteresis loops as an ASCII file using a text editor These formatted files llg hysfield can be read into the program with the Read Input File option THE PRO GRAM ALLOWS FOR NO MORE THAN 16384 FIELD POINTS When reading a file the program assumes that the field points are distributed non uniformly The field values are entered into the non uniform edit field and are displayed in the OpenGL window Such fields can be edited When you create any ty
258. mode Set Hx Oe to 1000 0 3 Set the Points on one branch to 11 4 Click Accept Changes to log your changes Run the problem RERUN THE PROBLEM Re initiate an LLG computation Load the previously saved file This time force the easy axis to be along X Exit the page Begin the calculation and save a movie COMMENTS The difference in the remanence and coercivities is evidence for the different orientation of the easy axis The sample with the easy axis oriented at 45 from X in the X Y plane has a coercivity of about 200 Oe and a zero field magnetiza tion of about 0 61M saturated The sample with the easy axis aligned along the X plane has a coercivity of about 450 Oe and a zero field magnetization of about 0 86M saturated Use the Any direction option to orient the direction of the easy axis in your films FEATURES Structure 150 nm x 150 nm x 10 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 15x 15x 1 Material Permalloy Relaxation 1 Pt Energy Minimization Initialization 10 from X in the X Y plane Hysteresis Uniform H 1000 Oe Ny 11 Anisotropy Any at 45 from X in the X Y plane FIGURE 142 Hysteresis Loops Taken along the Easy Axis and at 45 from the Easy Axis 39 248 LLG Micromagnetics Simulator User Manual CHAPTER 40 Sample Problem 15 Magnetization Dynamics in Permalloy Platelets This sample problem illustrates the use of time integration to keep track of temp
259. n dent problem Checking the Commit Size box on the Main Page allocates memory for the arrays that represent your structure and fixes the discretization volume You MUST check the Commit Size box BEFORE you input or edit Masks Chapter 21 or alter parameters with the Position Dependent Parameter Editor Chapter 22 Once memory has been allocated you cannot change the number of cells in the prob lem If you need to alter the problem s size you must reinitialize LLG INPUT SEQUENCES FOR MASK LAYER AND POSITION DEPENDENT DATA For Global and Mask Data 1 Enter Global data 2 If using Masks check the Commit Size box on the Main Page 3 Click the Masks button on the Main Page 4 Enter or load the mask through the Mask Editor Note If your structure is a single material layer DO NOT check anything under Structure Properties on the Main Page For Global Layer and Mask Data Enter Global data Check the Layers box under Structure Properties on the Main Page Enter data for each layer through the Layer Props Page Click the Masks button on the Main Page Enter or load the mask through the Mask Editor B UP ae For Global Layer Position Dependent and Mask Data 1 Enter Global data Check the Layers box under Structure Properties on the Main Page 2 Enter layer data on the Layer Props Page e Check the PosDep box not the button under Structure Properties on the Main Page Check the Commit Size box on the
260. n directed 30 off the long axis Hysteresis Uniform H 1250 Oe Ny 21 Coupling Interface exchange coupling 0 Hysteresis Loop FIGURE 134 Hysteresis Loop Showing Antiferromagnetic Coupling between the Layers LLG Micromagnetics Simulator User Manual 32 225 CHAPTER 33 Sample Problem Antiferromagnetic Exchange Coupled Permalloy Platelets This is the second sample problem with multiple material layers It has two layers of Permalloy which are antiferromag netically coupled through exchange at the interface In all other ways this problem is identical to Sample 7 INPUT SHEET MAIN PAGE 1 Initiate an LLG computation 2 Enter the dimensions of the problem X nm is 250 nm Y nm is 100 nm and Z nm is 20 nm 3 Enter the discretization for the problem N is 25 Ny is 10 and N is 2 4 Select Layers in the Structure Properties group box INPUT SHEET LAYER PROPERTIES PAGE 1 Click the Layer Props tab 2 Enter 2 in the N Layers edit field 3 Enter 1 in the Layer edit field Set the Layer Thickness to 10 0 Click the Material button Select Permalloy and click Accept Click LOAD LAYER PROP to define the material for layer 1 4 Enter 2 in the Layer edit field Set the Layer Thickness to 10 0 Click the Material button Select Permalloy and click Accept Click LOAD LAYER PROP to define the material for layer 2 5 Compute the interlayer coupling for 10 nm thick films of permalloy as Hexchange
261. n M T t the anisotropy K T t and the exchange stiffness A T t are all functions of Temperature T and time t The parametric dependence of the LLG input parameters on time is specified by either reading a file that contains T x y z t data or through a function temperature input that computes T x y z t The complication in solving the LLG equation for magneto optical materials stems largely from the fact that mean field theory is not a good approximation for systems near the transition temperature i e near the Curie temperature T Here the gyromagnetic frequency y 90 2 is usually determined from the free elec tron value of og and the spectroscopic splitting factor g 2 The gyromagnetic frequency y the damping parameter a and the magnitude of the effective fields determine the time scales of interest For time domain simulations the nomi nal free electron gyromagnetic frequency is y 1 78 x 107 Oe sec 1 The damping parameter a is typically selected to LLG Micromagnetics Simulator User Manual 46 269 Magneto Optical Simulations Supplement be between 0 005 and 2 0 The effective magnetic field on each magnetic moment is determined from the total system energy Etot as 0E T t H T t pr 9 M T The effective magnetic field incorporates all the effects of exchange anisotropy external fields and demagnetizing fields For the analysis of the equilibrium micromagnetic structure the differential equati
262. n Z 0 plane Front Boundary Condition on Z Zmax N2 15 118 LLG Micromagnetics Simulator User Manual Chapter 15 Inputting Data Into LLG Layer Boundary Conditions The boundary condition direction cosine values can be unnormalized as LLG performs normalization internally How ever the values are constrained to 1 m lt 1 GENERATING POSITION DEPENDENT FILES You can use LLG to generate position dependent magnetostatic fields such as those provided to an AMR sensor head by an external biasing permanent magnet LLG computes the field for any set of boundary conditions where the moments are perpendicular to the boundary therefore you can use the boundary conditions to generate position dependent fields for other calculations Alternatively you can generate formatted position dependent field files see Chapter 4 Loading Saving Files and read them in with the Global BCs or Layer BCs Pages If you want to bias a structure with an external field that is generated by magnets set up the parameters for the internal grid of interest Make the material properties of the grid those of the permanent magnet especially the magnetization For example if the magnets lie at X 0 and at X X nax and are magnetized along X set m left 1 0 and m right 1 0 Click Output File Name check the Write File box and name the file Close the page and complete the initializa tion by starting the computation Once LLG has computed the field te
263. n the Z direction In this problem layers 1 and 2 are each 10 nm for a total thickness of 20 nm There are two layers specified in Z in 20 nm which makes the integral layer thickness compliant at 10 nm When you try to exit the page by clicking Accept Changes LLG checks for compliance and warns you if the param eters are set incorrectly LLG places layer 1 on the bottom Z 0 of the structure and places layer 2 above layer 1 at an increased value of the coordinate Z The interlayer coupling between layers 1 and 2 should be set to zero This completes the layer parameter initialization 16 Click Accept Changes to exit and record your entries INPUT SHEET COMPUTATION PAGE 1 2 3 4 5 Click the Computation tab Set the Convergence limit to 0 0001 and the Iterations to 25000 There are no boundary conditions or externally applied currents in this problem Use the 3D Complex FFT method to compute the solution to the LLG equations Set the Time Step to 4 0 ps This entry will be revisited once the simulation has been initialized Click Accept Changes to exit and record your entries INPUT SHEET INITIALIZE PAGE 1 2 3 4 Click the Initialize tab Click the Uniform X Direction button in the 3D Uniform Magnetization field Notice that the Sign On Uniform options default to Positive with Theta 90 0 magnetization in the X Z plane and Phi 0 0 magnetization along the X axis Enter 30 0 into the Phi edit field to can
264. n the figure the 45 degree grid with the staircase edge shows marked errors in the computed demagnetization field which are corrected using the edge algorithm implemented within LLG The torque shown at the bottom graph are again more accurately represented in the edge correction scheme although the overall error is not so large as the effective field Hy 4nMg Hy 4nMg m x Hgtray 47Ms 0 35 Ir rer parrer em qoe i 0 30 I Grid 5nm Cells e a 0 Grid 10nm Cells i 025 45 Grid 14nm Cells Staircase j E 45 Grid 14nm Cells Edge Corrected 1 0 20 4 F o 0 15 af F i 0 10 F e 3 E e 1 0 05 E PET er 3 o ete e e 9 9 ooo 1 0 00 POP OPERE PEPE SPS eee er 900 920 940 960 980 1000 Position nm 0 30 DEET EE EE P 0 Grid 5nm Cells 3 0 25 0 Grid 10nm Cells 2j F 45 Grid 14nm Cells Staircase 0 20 45 Grid 14nm Cells Edge Corrected 0 15 LIE e 0 10 P 4 E 0 06 E o E papera 20 lo 09070 0709070 0 00 900 920 940 960 980 1000 Position nm FIGURE 81 Edge Fields and Torques 22 162 LLG Micromagnetics Simulator User Manual Chapter 22 Inputting Data Into LLG Position Dependent Parameters te o TT 10 Hidden by Corrected 45 Staircase 45 Edge Corrected 0 5 E a o L oo s L 0 5 1 0 Du Krag LEN gn KEE qp ES 600 400 200 0 200 400 600 Field Oe FIGURE 82 Computed Hysteresis Loop
265. n to the file Remember to check the appropriate boxes to indi cate which loops you want to save to the llg hyspart file e Click the Save To File button to store your hysteresis loops You can examine your llg_hyspart file with the 2D Graphics utilities see page 31 25 198 LLG Micromagnetics Simulator User Manual Chapter 25 Viewing Movies MOVIE PLAYER EDIT MOVIE FILE PAGE na r Re Order Movie Frames Movie Hysteresis Edit Movie Edit Movie File Movie Frames Frame 2 Frame 3 Frame 4 Frame 5 Frame 6 Frame 7 Frame 8 Frame 39 Frame 11 T ps 1569 0 Tips 1820 0 Tips 2098 0 Tips 2397 0 Tips 2722 0 Tps 3074 0 Tips 3463 0 Tips 3892 0 Frame 10 T ps 4370 0 T ps 4912 0 Frame 12 T ps 5534 0 Save ToFile H De 280 0 H De 260 0 H De 240 0 H De 220 0 H Oe 200 0 H De 180 0 H De 160 0 H De 140 0 H De 120 0 Hiel 100 0 H De 900 Move or eliminate frames Store the new sequence and reload to view 64 640 320 18 Existing Movie nterpolate 4 Movie Onto A New Grid Interpolated Movie Nx B4 My 32 Interpolate Nz 3 f nm 640 onm 0 lem 320 Yo nm 0 Ztinm 18 Zolnm oO FIGURE 122 Movie Viewer Sheet Edit Movie File Page The Edit Movie File Page is for editing and storing LLG movie files You can reorder or move movie frames Once you have revised or edited a movie click the Save To File bu
266. netic exchange See interlayer exchange arbitrary h field v2 input and output file format of 44 arrays allocating memory for 74 arrays properties probing data 71 arrows examples of 169 170 177 graph type 60 asymmetric Bloch wall Permalloy example of 219 avi files 195 B basic data input sample problem for 201 205 batch files generating from existing files 190 using scripting interface to write 189 varying existing files to use as 191 batch mode processing 187 controlling externally 189 editing files for 188 files that runin 188 LLG writing comments on problem variation for 188 monitoring 188 pausing 188 scripting interface for 189 setting up problems to run in 188 setting up the executable for 187 starting 187 b field visualizing 174 bilinear and biquadratic GMR 115 bitmap examples of 170 178 file type 31 graph type 59 graph type synchronized with 171 using color table to display 67 visualizing residuals in 171 warping 59 Bloch wall asymmetric sample problem in Permalloy 219 sample problem of bulk terminated in Fe 243 boundary condition field visualizing 172 boundary conditions important note regarding setting fields 76 234 layer parameter limits of 117 parameter limits of 85 position dependent 164 sample problem with steps for input 233 specifying 85 with layers 117 boundary region exchange 153 b probe 183 C calculator function 70 catch the transition 180 clock function 69 coarse grids problem
267. netization fields and any other fields resulting from terms that contribute to the free energy The exchange field is defined as on a Cartesian grid DEMAGNETIZATION FIELD You can visualize the vector field whose projections are the normalized demagnetization H field vectors along the three Cartesian axes with the Demagnetization Field View Option Use this to locate large demagnetization effects and to determine when they dominate nucleation and switching ENERGY DENSITY You can visualize the scalar Energy Density This is the only true scalar visualization mode Since a scalar field cannot be visualized in a vector mode with arrow fields for example this option is synchronized with the Bitmap Graph Type LLG Micromagnetics Simulator User Manual 23 171 Chapter 23 Simulation OPTIONAL VIEW OPTIONS r Optional View Options Boundary X 1 Hel p Temp K Shielded Ext Hysteresis Loop MR Loop FIGURE 93 Optional View Options BOUNDARY CONDITION FIELD You can visualize the vector field whose projections are the normalized boundary condition H field vectors along the three Cartesian axes When your boundary conditions have components of the magnetization normal to the bound aries there is a stray field within the sample volume due to the boundary conditions LLG treats this field as an inde pendent externally applied position dependent field In cases where such fields determine the nucleation
268. ng srrrrnannrvnnnrrrnnnnnnnrnr renn nn coco rca ann cnn rana 189 Generating a Batch File Using a List of Existing Files sssssssssseseeeeneneeneneenne enne 190 Varying Batch Problems and Scripting ssssssssssssssssesess seen enne nennen enn nr sn nnr inns nen 191 Batch Mode Position Dependent Parameters AAA 192 Glosirig the Scripting Interface ioc A ene Dl A a edu dde 192 CHAPTER 24 Viewing FIGS A eu nana utu eR EE x Fea e ka b Fe au eeben 193 CHAPTER 25 Viewing MOVIES ii 195 LLG Movie Player Sheet Movie Page 195 Eoadingand Saving Options cum 195 Movie Viewing pions it e teen oleas ttbi unii ct eset En E 197 MR and Hysteresis LOOPS rrt eter tinet eere ttg tene tin pete adt ou e Madero tdv Ela 197 Interacting withthe Data EE 197 Editing or Creating Masks cere are cate eei to idee eee e desti e cta 197 SPITTING E RE 197 Movie Player Extract Hysteresis Loops Pag8 oommcoccccnonoccccconooncccncnnnnnoncnnnnnnnonnnnnnnnne nn NERENN ANANA nennen nenne 198 Movie Player Edit Movie File Paggene ninaa RA ETEA E RINEN A EEEE EAEN ORA EARRA 199 luese EIER LC 199 viii LLG Micromagnetics Simulator User Manual Table of Contents CHAPTER 26 Sample Problem 1 Basic Data Input for a Permalloy Cube 201 Input Sheet Main Page EE 201 Input Sheet Globals Page and Materials Page eene nennen nennen nnne nnn 201 Input Sheet Computation Page nennen t
269. ng features apply only to that Sheet LLG Micromagnetics Simulator User Manual 21 143 Chapter 21 Inputting Data Into LLG Mask Editor MASK EDITOR SHEET SUPER EGG Main Bitmap Edge Super Egg Le Super Octagon For General Ovals 56 Xextent nm offset nm 56 Yextent nm Yoffset nm Xshift nm 0 Y shift nm 0 Corner Segments 3 p DE nm nm 18 18 yinm y nm 18 2 Power Power 2 Pivot 1 Coordinates Pivot 2 Coordinates Offset From Corners Pivot 4 Coordinates Pivot 3 Coordinates 3 x nm x nm 5 5 y nm y nm 5 2 Power Power 3 Create Super d Main Control Octagon FIGURE 67 Mask Editor Sheet Super Egg The super egg or superoctagon has eight parameters length width thickness four corner parameters and an expo nent for the curvature of the four corners The corners are quadrants of a superoval given by x x W Yo 1 This addition to LLG was prompted by Prof Tony Arrott and Dr Terry Templeton who routinely use the super egg to define stable modes for MRAM switching The super egg encompasses all shapes from pointed corners to flat edges depend 21 144 LLG Micromagnetics Simulator User Manual Chapter 21 Inputting Data Into LLG Mask Editor ing upon the size and sign of the exponent A series of super egg examples shown below The maximum number of vertices that you can enter in the polygon mode and super egg mod
270. ng menu You can either split the window horizontally resulting in two windows one above the other split the window vertically resulting in two windows side by side or delete the active window You cannot delete the last window as LLG requires that there be at least one active OGL window You can continue to split the windows and make the nesting and the view sequencing into a configuration of your selection Split Window Horizontally Split Window Vertically Delete Active View Save Bitmap To File Synchronize Parameters In All Views Read OGL Parameters From File Write OGL Parameters To A File FIGURE 7 LLG Recursive Window Splitting Menu Since LLG supports multiple view windows you can replicate the properties of a single window to all window by select ing the synchonize parameters selection in the menu In addition you can read and save OGL parameters to a file for use in later LLG simulations You can archive the OGL view settings that you prefer so that you can load and run sub sequent problems from the same view perspective LLG Micromagnetics Simulator User Manual 5 53 Chapter 5 LLG Environment e LLG Micromagnetics Simulator V20 Deg LLG CEE Ele View Heb HESS TV SEE 3 Jj MUS kyrne A TmeDepH vi Shields Pai Cimera Layer Prope Lan Bt Mate Baich Man Global Materiais Boundary Computation be CG ES Le las Raad ingat Fis Save legua Fins Read input Save vi Ingut Save va leget Speciy Oup
271. nned field point dotted into some direction and the value of the magnitude of M is that magnetization dotted into that same direction The Loop Direction edit boxes are for specifying the x y and z components of the direction cosine of which you want to obtain the hysteresis loop By default the x direction is specified Therefore if you want you can scan the field along one direction and acquire a hysteresis loop projected along another CW and CCW indicate the rotation sense of each loop SPECIFYING THE NUMBER OF Loops The number of rotational loops may be entered If the sample has not been trained then at least 2 loops are required to determine the equilibrium rotational hysteresis loop If the sample has already been trained then a single loop will suf fice TORQUE MAGNETOMETRY You must check uniform rotational and torque check boxes ALL THREE You can specify the plane and the rotation sense as described above When you check torque LLG will make a single pass from the starting angle of field defined by Hx Hy and Hz pass through the defined angle in Nx increments and then return to the intial state You can plot the loops as rotational or as a function of angle Please remember to click the Accept Changes button to record your changes to LLG s internal data structures 17 126 LLG Micromagnetics Simulator User Manual CHAPTER 18 Inputting Data into LLG Non uniform Hysteresis Loop SPECIFYING NON UNIFORM SAMPLING
272. nnnnnenrartannnnnnnn renn nnnnsnnnressn nisi inerte enn n sinn s nnns 94 Number RHS ici 94 EAEE m E EE 94 hs a EU 94 Start TI Ma T 94 Stop ENEE 94 Temp T I e Benes eot va ee fte deett co reete E ca cotes ite ph EE eco ee UTI EI RR Eee eth ET ei trs 94 RN S86d aite Vete dude We dieu lr ede Pau ee ee eed ae dede da e T Ut va Doe A sc ve eec ov de Eu re e 94 NNI REIHE 95 Exchange and Correlation gett PU Lata adden digre 95 CHAPTER 11 nputting Data into LLG Initialization reuannsevvennnnnnnnnnvnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnennnnnen 97 Read from File and Input File Name 97 3D Uniform MagnetizatiOn ieu ite cedent eere eod O Ra iE ESEA N EAA etaient 99 3D Transition Magnetizaltiori eerie ene ne edet Pee eee e pee ue x e Lee a dee eide de 99 3D Vortex Magnetization im pre tenerte EN reiten Ii uteri exe EE RE eet 100 2D Narrow or Wide PI 100 Random u eeler EE 101 CHAPTER 12 Inputting Data Into LLG FieldS sssciccsssstsstsosnsstccssssedseoderecssasssiadassortaawadsstevessdobaeas 103 External Applied Field WEE 103 Pinning A ET AE A ONT OE IEAA ENEA ATENE AEE OAE AEE 103 Pinning alayo err ridi e ERE Dad e T pk e a e E T ETTR 103 Analyzing the k 0 Fourier Component in Periodic 3D Complex BC Computons oooooonoccccnoccconanacnnanaccnanancnnancnos 103 Optionally Remove Effective Field Components esent n nnne nennen sentent 104
273. nocccccccnanoccncconanoncnncnnnnnnnnnnnnno nennen nene nn rr rn rre 162 Position Dependent Parameters Sheet BC Page 164 CHAPTER Wu t 165 Progress Status Indicators 7 edic etie eie a ated da oed tdt ded Eege be dace y nado read 165 Simulation Page uere tur e ag Eee ee 166 VIOWS P ge Rd 167 Viewing Position Dependent Parameters A 167 Standard View e le EE 168 Magnetization Direction Cosines nennen enne nnn einai iiaii sss nnns sentent nenas einen 168 Residuals Change Weraton eene ennt nnns entenrt enr ssn therein nnns innen nens nnne nen 171 Effective Field iege dede aedes heated evel ipee vo iain eR Per decr vec iet is 171 LLG Micromagnetics Simulator User Manual vii Table of Contents Demagnetizatiori Fleld nro diei t nee qi eren rade ep pee E idee e ete d aie 171 Energy Density icc eee de a 171 Optional View OPNS caricia e irae des dle ehe ia uen e o de Ru c RU T aU Ea eR rne dante 172 Boundary Condition Fieldsa anai AA aoe a eh tee Vedi ae De 172 Gurr nt Ind ced Fleld ravnene ibat eto ee prb ade bebo eho 172 Position Dependent External Field 172 Shielded External Field at dedii e eite e red ladies 172 Hysteresis Loop and MR Loop ree eret tendere esee nenne eee ut ee eet reg dox e ee ade e eae dae n 172 Gomput d VieWw OptlOns ru vindrue bete En donde Dee b e eir dure ecoute Ag e ERE vite 174 Computed Imaging Mode View Options
274. nsfer LLG you must at the same time either transfer all copies of LLG to the same party or destroy any copies not transferred You must also notify Licensor in writing within 30 days of the transfer of LLG and this license agreement e You may not use or install LLG on more than one workstation concurrently e You may not copy rent distribute sell license or sublicense LLG or its license in whole or in part to another party e You may not transfer LLG or its license in whole or in part except as specifically set forth above Time Limit of License If you license the code year to year your license will be automatically renewed each year under the original terms price and conditions of this Agreement unless you notify Licensor in writing about your intention of letting the license expire 30 days before the license expiration date If you let the license expire you must delete and destroy all copies of LLG associated documentation and installation media LLG Micromagnetics Simulator User Manual 1 17 Chapter1 License Agreement and Release Notes Limited Warranty If you discover physical defects in the media on which LLG is distributed Licensor will replace the media You must return the defective media to Licensor with proof of purchase LICENSOR DISCLAIMS ALL IMPLIED WARRANTIES ON LLG INCLUDING WITHOUT LIMITATION WARRANTIES OF MERCHANTABILITY PERFORMANCE AND FIT NESS FOR A PARTICULAR PURPOSE LICENSOR WILL NOT BE LIABLE FO
275. nsor the field from the boundary conditions will be computed and saved to the file Exit LLG and restart your real problem that is the real sensor configuration Use the Boundary Conditions Page to read in the fields generated by the magnets Do not enter anything into the boundary conditions fields Close the page and proceed You will be able to visualize the fields using the Boundary Conditions Field viewer during the simulation phase In general you can read in or save a formatted position dependent magnetic field by clicking the Input File Name or Output File Name button SPECIFYING PERIODICITY LLG allows you to compute the properties of periodic structures For three dimensional structures you can specify a structure to be periodic along any one or two of the three Cartesian directions This is implemented with FFTs Two dimensional simulations can be periodic only in Y The continuous boundary condition option allows you to model a bulk terminated surface such as a domain wall at the surface In the LLG convention continuous boundary conditions remove the magnetostatic charges from the bottom surfaces of the bottom row of sub elements Therefore the mag netization appears continuous for all Y values below the bottom set of sub elements To implement this scheme LLG uses the 2D interface discretization scheme as described earlier At present the 2D Continuous feature is not active in v2 of LLG IMPORTANT NOTE For 2D Real FFTs the
276. nterior or exterior to that shape e You can Fill the Mask Region either Internally or Externally In each case the action of changing the cell types will occur either within or outside of the defined shape You can either Toggle Cells i e the logical NOT operation Turn Cells On On or Turn Cells Off Off under Mask Properties e Instead of turning cells on or off completely Uniform Fill within the defined region you might want to change the properties of the cells randomly Random Fill e Aunivariate random number generator is used to turn off cells as a function of location with a probability of a Frac tion of those cells being specified For example since random numbers are generated between 0 and 1 a Fraction of 0 5 makes it equally probable to turn cells on or off If you choose a fraction of 0 75 on average 3 4 of the cells will be turned off or on depending upon the Mask Properties option selected and so on e You can select how the fill factors are generated throughout the layers using the Layer Fill options Since the view is constrained to be one projected into two dimensions you must specify the actions that are to take place in the third projected dimension Your choices are to act only on This Layer the one visualized and adjusted through the Graphics Control All Layers or on a Range of layers as specified by the Lower and Upper edit fields Here lay ers are actually the discretized sub element count not the ac
277. nts A45 and A44 equal to 0 22 Click the LOAD LAYER PROP button to record your changes 23 Click Accept Changes to record the variables INPUT SHEET CURRENT PAGE 1 Click the Current tab 2 Select 2D for the current 3 Set the direction to be X 4 Enter 1000 0 in the Current UA edit field 5 Click Accept Changes to record the variables INPUT SHEET INITIALIZE PAGE These are identical to Problems 7 and 8 INPUT SHEET HYSTERESIS U PAGE These are identical to Problems 7 and 8 Problem specification is complete Click the Begin Simulation button SIMULATION SHEET SIMULATION PAGE Once the Simulation Sheet Simulation Page is visible divide the screen into four quadrants Put the hysteresis loop in the upper left the MR loop in the upper right the lower layer magnetization is the lower left and the upper layer mag netization in the lower right Run the problem and save a movie file Notice the complex hysteresis and MR loops that result from the coupling between the layers COMMENTS Notice that the magnetization layers are the same and that the total magnetization is zero in the antiferromagnetic state FEATURES Structure Sub Element Discretization 250 nm x 100 nm x 30 nm 10 nm x 10 nm x 10 nm 25 x 10x3 Material Permalloy layer 1 Non magnetic Cu layer 2 and Permalloy layer 3 Relaxation 3D Complex FFTs Initialization Uniform magnetization directed 30 off the long axis Hysteresi
278. o starting to simulate integrate for the first time You must define movie options before you start a computation since you will not have another chance to change or update them once a simulation is initiated The file names for standard LLG output files are summarized for your convenience Additionally while the calculation is paused you can Save This Dom File at any time during a cal culation As you can modify the computational parameters after a calculation has started there is an extra option to save a v1 Save Old Input File or a v2 Save New Input File to disk for later use SAVING A MoviE TO Disk To save a movie to disk you must check the Write To Movie File box The Write Movie File Increment option is for saving time slices during a time dependent calculation to a file Long calculations produce even longer movies so choose the Write Movie Time Increment carefully SAVING DOMAIN STATES DURING A HYSTERESIS LOOP Sometimes you might want to save the domain states during a hysteresis loop even though you are not at the equilib rium state for that field LLG terms this catching the transition Check the Catch The Transition box if you want to do this Set the Edge Transition Increment to a value between 0 and 1 If you set the value at 0 2 then when each value 23 180 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation that is passed for remanence 1 0 0 8 0 6 and so on a movie sheet will be written to the f
279. ogressPos 0 m fileStdio Write m pLLG gt m pPosDepMagnetization nArraySize Magnetization m_nOffset 3 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepExchange_X nExchangeSize X Directed Exchange m_nOffset 4 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepExchange_Y nExchangeSize Y Directed Exchange m_nOffset 3 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepExchange_Z nExchangeSize Z Directed Exchange m_nOffset 4 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepUniaxial_2 nArraySize Uniaxial Anisotropy 2 order m_nOffset 3 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepUniaxial_4 nArraySize Uniaxial Anisotropy 4 order m_nOffset 4 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepCubic nArraySize Cubic Anisotropy m_nOffset 3 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepHpin_X nArraySize X Pinned H Field m_nOffset 4 if m_bDoProgress UpdateProgressBar LLG Micromagnetics Simulator User Manual 4 47 Chapter 4 Loading Saving Files m_fileStdio Write m_pLLG gt m_pPosDepHpin_Y nArraySize Y Pinned H Field m_nOffset 3 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepHpin_Z nArraySize Z Pinned H Field m_nOffset 4 if m_bDoProgress Upda
280. on need not be integrated directly Instead notice that for an equilibrium magnetization distribution dM dt 0 which implies that the effective field Hau must be parallel to the magnetization M The magnetization configuration can be relaxed iteratively by posi tioning each magnetization vector almost along the effective field vector direction throughout the mesh 2 SPIN MODEL In the 2 spin model it is assumed that a strongly antiferromagnetically coupled 2 spin sub lattice exists such as in the TbFe or TbFeCo system Here following Mansuripur and Giles the LLG equation can be adapted where now an effec tive gyromagnetic frequency damping constant and effective field can be attributed to the lattice as a whole The sys tem of equations is now given by V e m To dM T t mye Vett M T t x Ha T t _ Vett eff M T t x M T t xH T t dt VEG AFA IM T t M T t M T t M T t y M T t y Y err 1 0 oa M T t y a M T t y MOT 0 Yy M T 0 Y Qo T t M T OH an M T tH ar gt M T t M T t H T t where Her 4 and Her 2 are the effective fields on sublattices 1 and 2 respectively and the new He is effectively the effective field computed through normal means with M set to Mj M As Mansuripur points out there is a singularity in the gyromagnetic frequency and damping constant at the angular momentum compensation point but that singularity does not appear in t
281. op Time to 106 t lt 106 I T 1 uA Current Start I T 1 106 lt 1 T 1 X108 I T 2 uA Current Stop I T 2 106 I T 2 lt 106 Time Interval Steps T steps 0 S Tyteps S 16383 Time Interval Specified N 0 N 1000 Time ps Step T 0 0 lt Tsteps OF step LLG Micromagnetics Simulator User Manual 13 105 Chapter 13 Inputting Data Into LLG Current Af Hell 4 HysNU A HE 2 FMR wi Shields Main Globals Materials Boundary Computation Initialize Fields Current Layer Props Layer BCs Notes Batch Va Read Save Time Dep Current 1 0 Files to Read Input File Save Input File ZN 2D I Direction Time Independent Current Current uA 0 0 fe X C Se s Zz Sinusoidal lo sin 2 pi b t c t ps From t1 to t2 ac Current lo 0 0 b 00 e 00 4 0 0 p2 0 0 2D Quasi Uniform 3D Y Enable Ift MAAK fe 2D Specify 3D S 0 0 C 3p Current Tibet 0 uA T2 ps 0 0 0 us Spin Torque i 0 Timefpsl Step Time Interval Steps 10 Time Interval Specified E 1 0 Intervals Loaded LOAD SECTION H Time Loaded ps Ma Clear Al amp Main Control 3D Flow 2D amp 3D Current Files M Bead Flow Read Field Save Flow Save Field FIGURE 48 Input Data Sheet Current Page 13 106 LLG Micromagnetics Simulator User Manual Chapter 13 Inputting Data Into LLG Current READING AND SAVING TIME DEPENDENT CURRENT INPUT AND OUTPUT FILES LLG allows
282. or the variation of that parameter for the range option In the example above the Saturation magnetization will step from 700 725 750 775 and 800 that is from 700 to 800 in 5 values For the random option you must enter the minimum maximum standard deviation number of increments and the type of random variable to use either gaussian or uniform If you use uniform variates the range is from min gt max If you choose gaussian deviates the mean is max min 2 and the standard deviation is as specified The list option allows you to enter any appropriate list of values The file option when enabled allows you to scan for files Use the Multiple add button at the bottom to add more than one file at a time from a directory of your selection When you check vector multiple values you are prompted to enter them in either range or list format only Once the sequence is complete LLG creates a new directory The name of the directory is the seed file s name augmented by the date and time The files will be created in the new directory and will have the same file name as the original file augmented by a number 0 1 and so on Since the directory names are keyed to seconds you will never be in danger of overwriting your files LLG will also write the appropriate batch file in the newly created directory If your param file uses any auxiliary files as discussed above then the same files will be used in each parameter variation file Pres ently
283. oral changes in the magnetization over time INPUT SHEET MAIN PAGE 1 gt Y Initiate an LLG computation Enter the dimensions of the problem X nm is 150 nm Y nm is 150 nm and Z nm is 10 nm Enter the discretization for the problem N is 15 Ny is 15 and N is 1 Check the Save Conv Details box and enter 10 in the Every N Iterations edit box This will save the energies and remanence every 20 ps INPUT SHEET COMPUTATION PAGE 1 noo 1 P Se M 8 Click the Computation tab Deselect the Convergence and Iterations boxes Check the Stop t ns box and enter 2 0 ns for the Stop t ns Enter 0 02 for Alpha Check Time Faster Select the 2D Real FFT method and set the ps Time Step to 1 0 Click the Predictor Corrector Time Integration method This method should be used for all problems where alpha is 0 5 Click Accept Changes to log your changes INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 BON Click the Globals tab and click the Material Selector button Select Permalloy from the Materials Page Click Accept The Permalloy properties should be entered in the edit fields of the Globals Page Click Accept Changes to log your changes LLG Micromagnetics Simulator User Manual 40 249 Chapter 40 Sample Problem 15 Magnetization Dynamics In Permalloy Platelets INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Initialize the magnetization along Negative X in the X Y plane
284. ors 2 Open e Length 776 Bits Pix 1 I Mllg v2 0 work Kamel EyeShapel bmp Flip v Flip Vertical Image Color T able Flip Horizontal 80 O o Bo 0 Rotate 90 Degrees CW m Oo EH o Bo Rotate 30 Degrees CCW 0 0 D D 0 0 0 Click the Flip button for the E o ro Bo 0 options in the menu above Number Of Colors 2 D Param Unset Apply Mask Apply Parar Reset P Param Set Param Saved Main Control FIGURE 65 Mask Editor Sheet Bitmap Page SPECIFYING MASK PROPERTIES OPTION TWO The second option for specifying mask properties is to import a bitmap jpeg or targa file that you have created with a separate graphics application IMPORTANT NOTE LLG recognizes and applies ONLY BLACK as the color of the mask so the mask region of your graphic MUST BE BLACK in the RGB sense 0 0 0 1 Specify which layers you want to mask on the Main Mask Editor Page and whether you want to toggle turn on or turn off the region internal or external 2 Loadan image file by clicking the Open button and selecting the file type from the options An image of the file will be painted in the window on the Bitmap Page The spatial extent of the image is scaled to match the size of the projection of your structure 3 To flip and rotate the image click the Flip button and select the desired option 4 Click the Apply Mask button to visualize your changes in the graphics window This Bitmap Page also appears
285. ose PosDep Tool INPUT SHEET CURRENT PROPERTIES PAGE 1 Click the Current tab 2 Set the Time Independent Current to 1000 uA 3 4 Check 3D current and click the Specify 3D Current button This brings up the Current Mask Editor Onthe third layer use the rectangle tool to specify rectangular regions as above at either end of the Permalloy bar Set the Current to Enter on one end and Leave on the other Click Accept and close the tool You are ready to compute the current flow and field so start the simulation The out put is shown below FEATURES Structure 640 nm x 320 nm x 30 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 64 x 32x 3 Material Permalloy FIGURE 149 3D Current Flow in a Bar with a Hole 44 264 LLG Micromagnetics Simulator User Manual Chapter44 Sample Problem 19 3D Currents FIGURE 150 3D Current Field in a Bar with a Hole LLG Micromagnetics Simulator User Manual 44 265 CHAPTER 45 Sample Problem 20 Media This simple sample illustrates the use of the media option in the position dependent parameters page INPUT SHEET MAIN PAGE 1 Enter the Simulation Volume X nm is 640 nm Y nm is 640 nm and Z nm is 10 nm 2 Enter the discretization Ny is 64 nm Ny is 64 nm and Nz is 1 nm INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 Click the Globals tab 2 Set the magnetization to 350 and the anisotropy to 1000000 These are reasonable parameters for m
286. our favorite Color Wheel selections save them for future use Color wheel files can be Saved or Loaded by clicking the appropriate button You must click the Apply or Reset button to activate a new Color Wheel for the actively selected OGL view Please note that the angular range must be monotonically increasing i e Angle 5 gt Angle 4 gt Angle 3 gt Angle 2 gt Angle 1 Select Color Segments Start Color Bc Color 1 Angle 2 Color 2 Y Angle 3 Color 3 Angle 4 Endes Rotate Reset Apply gt Color Wheel Files Save Load EX Color V Wheel FIGURE 21 OGL Color Sheet Wheel Page 5 66 LLG Micromagnetics Simulator User Manual Chapter 5 LLG Environment OGL CoLoR SHEET TABLE PAGE The OGL Modes Prop Sheet Table Page is where you can alter and set the OpenGL color table properties directly Color tables are used to display Bitmap and Contour Graph Types The principle behind using a color table is to select colors over in plane angular ranges that are indicative of domain orientations The color table can be decom posed into as many as five regions where each range can be specified independently Select Color Segments Color 1 Hen Level2 0 Color 2 Fen Y Level3 0 gt Color 3 REN Level4 0 Color 4 iae D oS ANIM Reset Apply r Color Table Files Load EX Color V Wheel FIGURE 22 OGL Color Sheet Table Page
287. ous may be unstable Pause the simulation and visualize the Change lteration in the Bitmap Graphics Type Time Step Too Large Subtle and sometimes not so subtle instabilities caused by exchange appear when neighboring moments oscillate In the Changellteration Bitmap Graphics Type you will see oscillating parallel lines of red and blue This happens in any of the parallel FFT or time integration computing modes when the time step is too large Pause the simulation and decrease the time step Grid Too Coarse If the grid is too coarse your problem may never converge In both the 1 pt and FFT based methods problems defined on course grids oscillate wildly Since the grid stability is related to the specified parameters a general rigid rule can not be given for all situations However as a rule of thumb Permalloy sub element sizes should be no larger than about 10 nm and Fe sub element sizes should be no larger than about 7 nm If your problem becomes unstable and resetting the time step or accelerator does not remedy the instability Pause then terminate the simulation Restart the problem and increase the grid density The goal is to define as coarse a grid as possible while maintaining stability as this saves CPU time Exiting the Iteration Process Prematurely The validity of the solution depends upon whether the local energy minimum has actually been reached This criterion is difficult to specify analytically since LLG solves non
288. pe of uniform uniform rotational or non uniform hysteresis field the values of the fields can be output to a formatted ASCII file lo hysfield by using the Save Input File button You can generate a cata logue of field profiles that you commonly use Use the Name Output File button if you want to rename the hysteresis data output default file llg hys When you read in a file the new data once saved become part of the llg param file Therefore when you use the file in the future you are not required to re input the hysteresis field unless of course you change it LLG Micromagnetics Simulator User Manual 18 129 Chapter 18 Inputting Data Into LLG Hysteresis Non Uniform EXAMPLE OF A NON UNIFORM HYSTERESIS LOOP The following example has seven field segments the vectors are outlined in the table The first fourth and seventh sections are coarsely sampled while the second third and sixth sections are sampled on a fine grid You can use the arrow keys to display the contents of each section To delete a section use the DELETE SECTION button the effects of which will be reflected in the OpenGL window The philosophy behind the non uniform hysteresis field is that the field is specified on an arbitrary but connected path through field space The hysteresis loop will be displayed with the component of the magnetization projected along the initial field direction However all the magnetizations and fields are written to the ll
289. properties should be entered in the edit fields of the Globals Page Choose Z as the Easy Axis Click Accept Changes to log your changes LLG Micromagnetics Simulator User Manual 42 255 Chapter 42 Sample Problem 17 Hollow Pyramidal MFM Tip INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Initialize the magnetization along negative Z 3 Click Accept Changes to log your changes Mask Editor 1 Check the Commit Size box on the Main Page 2 Click the Mask button 3 Either load the mask provided or make a hollow pyramidal shaped mask COMMENTS Even the strong anisotropy of Co is not enough to saturate the magnetization of the tip FEATURES Structure 200 nm x 200 nm x 200 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 20 x 20 x 20 Material Co Initialization Negative Z Vv y y d d VY d d VY d d VY Vy Y y y y y y y y y y A vy VY yy y y Y y VY y y VY yy V ve y y vy y y y y y y y y A A M a A WM A zx sx uy A a 9 MN y zs eve ovx aa NNN FX ww ver as y NN 3 93 19 Y y FIGURE 146 Midplane Magnetization of the Tip 42 256 LLG Micromagnetics Simulator User Manual Chapter 42 Sample Problem 17 Hollow Pyramidal MFM Tip d X kk eg X S E Je e e E E E E e se E KK vc e kKE veer wR GN 1117274 V X725 uw AA a r FA ADIZAZ AA AS i po op od Hollow 1250 2500 Filled H 0e 3750 Fields From MFM Ti
290. ps Simulated With LLG 5000 6250 Hollow Tip Thickness 10 nm WO OA A E 7500 L L 500 400 300 200 100 0 Distance nm e ZE D Y y i i 1 f H Tip Diameter 100 nm 1 A a E PM Vo Eeer E E E FIGURE 147 End shank Magnetization and Field Dependence as a Function of Position Away from the Tip LLG Micromagnetics Simulator User Manual 42 257 CHAPTER 43 Sample Problem 18 Sample MFM Tip Interaction This sample problem illustrates the interaction of a solid MFM tip with a sample INPUT SHEET MAIN PAGE 1 2 3 Initiate an LLG computation Enter the dimensions of the problem X nm is 500 nm Y nm is 500 nm and Z nm is 100 nm Enter the discretization for the problem N is 50 Ny is 50 and N is 10 INPUT SHEET COMPUTATION PAGE 1 aS ON Click the Computation tab Check Time Faster Enter 2 0 for the ps Time Step Select the 3D Complex FFT method Click Accept Changes to log your changes but SHEET GLOBALS PAGE AND MATERIALS PAGE 1 ao PF YS DN Click the Globals tab then click the Material Selector button Select Permalloy from the Materials Page Click Accept the Permalloy properties should be entered in the edit fields of the Globals Page Choose X as the Easy Axis Click Accept Changes LLG Micromagnetics Simulator User Manual 43 259 Chapter 43 Sample Problem 18 Sample MFM Tip Interaction
291. ps 100 Time Steps 10 Mi Alphal 800 o 1 0 17 6 2 0 M2 Alpha2 Gamma 0 0 1 0 176 Al 0 Gammal Tel a 0 FIGURE 152 Position Dependent Sheet MO Main Page When you run a magneto optical problem using LLG extra memory is allocated for M4 x y z Mo x y Z o4 X y z ao X y Z amp X y Z Y1 X y Z Yo Y Z y Xx y Z T x y z and T x y z In addition memory is allocated for the input tem perature array read from file should you select that option 46 271 LLG Micromagnetics Simulator User Manual Magneto Optical Simulations Supplement SPECIFY AN MO CALCULATION To signal LLG that you will be performing an MO computation check the Do MO Calc box If you wish to perform a 2 spin computation check the 2 Spin Syst box You must enter the Time Step ps for each segment of the file that is to be read and the total number of Time Steps Your input file must have at MOST N time steps Your time evolution as specified when read from a file will be Nsteps I per step SPECIFYING POSITION DEPENDENT PARAMETERS You may specify the position dependent parameters for each input variable by 1 checking the box to signal LLG that your parameter is to be changed 2 entering the nominal value in the edit box 3 entering the gaussian random com ponent of the value adjacent to the edit box 4 drawing the appropriate sh
292. r ties of CoPt if you know them Click the Boundary tab and input the permanent magnet orientations Click the Save H Field File button to save the file Complete the LLG initialization The status bar indi cates that first the tensors and then the boundary condition fields are being computed Then LLG writes the fields to a file Exit when the Simulation Sheet appears Start a new problem this time load ing your real structure s parameters into the Input Sheet fields Open the Boundary Conditions Page and click the Read H Field File button Enter the filename with the permanent magnet field files Load the file them complete problem specification You will find that the stray field from the permanent mag nets is included in the external fields to which your structure is subjected INPUT SHEET INITIALIZE PAGE Back to the problem of interest 1 2 3 Click the Initialize tab Click the Uniform X Direction button in the 3D Uniform Magnetization field Notice that the Sign On Uniform options default to Positive with Theta 90 0 magnetization in the X Z plane and Phi 0 0 magnetization along X axis Enter 10 0 into the Phi edit field to cant the initial magnetization off the X axis by 100 Close this page by clicking Accept Changes Click the Begin Simulation button Run the problem 35 234 LLG Micromagnetics Simulator User Manual Chapter 35 Sample Problem 10 Boundary Conditions Applied to a Thin Platelet COMMENTS Notice
293. ract with it and experiment with modifying the parameters to identify those that must be specified accurately LLG Micromagnetics Simulator User Manual 23 185 Chapter 23 Simulation MoviE PAGE SIMULATE A MoviE OPTION Movie Views B Probe Sy LLG Movie Player jos Playback Of Recorded Calculations X4 File Options J GN Version Nx Frames Ny Status Nz Split Movie lt Manually Split Player Controls A Play I Pawe ri Rewind Speed 05 Sec Frame Progress as Frame Time ps ETE lt Output File Name Close Movie FIGURE 112 Simulation Sheet Movie Page Simulate a Movie Option You can load and play a movie through your simulation For explicit instructions on loading and playing movies refer to Chapter 25 Movie Viewer The movie that you load through this page with the Simulate a Movie option MUST have the same number of pixels in each dimension in the Simulation Volume as those specified in the Main Page This option allows you to play the movie visualize the magnetization effective fields energy densities and residuals simul taneously You can restore all essential simulation details in the short time it takes to play the movie 23 186 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation BATCH MODE PROCESSING LLG features batch mode processing In batch mode there is no graphical data representation A very simple user inte
294. rameter Sheet apply to the regions of color When you read in a new image LLG clears the internal data arrays that record the parameters associated with a given color 1 Import the graphic by clicking the Open button LLG records the colors of the graphic in the Image Color Table 2 Specify which layers you want to work with on the Position Dependent Parameter Main Page page 151 and whether you want to toggle turn on or turn off the region internal or external 3 Enter the data into the Main Params and Exchange Pages of the Position Dependent Sheet 4 Leftclick the color box whose parameters you wish to set and select Save Parameters From Pages to LLG Arrays from the pop up menu LLG places the Parameter Set Indicator P next to the color in the Image Color Table 5 Save the color parameters to a file click the color box and select Save A Single Color Parameter Set To A File from the pop up menu 6 Repeat this for each color that you wish to change 7 Once you have specified the entire array of parameter values save the entire parameter history to a file by clicking the color box and selecting Save All Color Params to a File from the pop up menu You can reuse this file at a later time you can apply the parameters from the file to a new image with the same number of color regions by selecting Load All Colors Parameters From a File from the pop up menu 8 Click a color box and select either Fill This Color s or Fill All Color
295. red in the edit fields of the Globals Page Click Accept Changes to log your changes INPUT SHEET BOUNDARY CONDITIONS PAGE 1 2 Click the Boundary tab Enter the permanent magnet orientations on two of the six sides into the Boundary Conditions edit fields Enter 1 0 in the Mx edit field for the Left X 0 boundary condition and 1 0 in the My edit field for the Back Y Ny boundary condition These are the values of the direction cosines on the left and back sides of the structure They represent permanent Permalloy magnets the first magnetized positively along X and positioned just to the left of the struc ture and the second magnetized negatively along Z and positioned at the back of the structure LLG will not change these values in the energy minimization process Due to the boundary magnetization adjacent to the boundaries LLG Micromagnetics Simulator User Manual 35 233 Chapter 35 Sample Problem 10 Boundary Conditions Applied to a Thin Platelet the interior sub elements will be exchange coupled to each boundary condition direction cosine and due to the nor mal component of boundary magnetization the magnetostatic field at each interior point will be computed and stored Check the Write File box Click the Output File Name button and enter a name for the boundary condition H field file This instructs LLG to store the values of the field at each point in the structure to a file after the values have been comput
296. rements for 2D Green s function problems 76 setting parameters for 77 sinusoidal fields 133 soft magnetic cube sample problem for 205 staircase effect 163 start up screen image when LLG loads 53 status indicators simulation page 165 structure properties 74 sub element size keeping small for curved jagged surfaces 239 system information 68 system requirements 17 21 T temperature 94 theory of operation 26 29 theta for specifying angle of incident beam 176 limits of 97 theta and phi aligning magnetization with 99 viewing the orientation of 62 time CPU 165 starting and stopping 94 time dependent h fields 131 parameter limits of 131 reading and saving files 133 sinusoidal fields 133 time integration 92 sample problem with 249 time slices saving during a time dependent calculation 180 time step 92 93 symptoms of setting too large 184 title entering for material 81 tool bar functions 54 58 total torque visualizing 174 transient energies saving to file 76 transition magnetization 3D 99 transition number limits of 97 transition region initial for 2D domain walls 100 U uniform magnetization 3D 99 update e 165 V video See movie view options 168 178 b field 174 boundary condition field 172 current induced field 172 d2H dz2 z nm 176 damping torque 174 demagnetization field 171 dH dz z nm 176 divergence of m 176 effective field 171 energy density 171 gyromagnetic torque 174 heff dm dt 174 hysteresi
297. resis loops The View Polar button lets you toggle between viewing the loop as a polar plot and as an angular plot The text on the button reflects the current state of the viewing tool FIGURE 95 Polar Loops Rotational Loop 1 0 ax 1 0 1 0 0 5 H Hmax 0 5 1 0 FIGURE 96 Polar Loops Represented in Polar and Angular Formats LLG Micromagnetics Simulator User Manual 23 173 Chapter 23 Simulation COMPUTED ViEW OPTIONS You can visualize several computed view options including B Field magnetic induction Gyromagnetic Torque y term in the LLG equation Damping Torque oa term in the LLG equation Total Torque and Heff dm dt this is sort of a dissipation term and is not completely rigorous due to the form of exchange field Computed View Options B Field Induction Gyromagnetic Torque Damping Torque Total Torque C Heft dm dt Dissipation FIGURE 97 Computed View Options FIGURE 98 Energy Density and Effective Field Bitmaps 23 174 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation FIGURE 99 Boundary Conditions Arrow Slice JomtuesuLG Micromagnetcs Smulatorun RE aye NN d L X dMz Ms K Al X dMx Ms 1eSLLG Micromagnetics sm FIGURE 100 Change Iteration and Demagnetization Field Contours LLG Micromagnetics Simulator User Manual 23 175 Chapter 23 Simulation COMPUTED IMAGING MODE VIEW OPTIONS
298. rface allows you to keep track of LLG s activities and progress The batch mode processor is based upon a list file This list file is a compilation of LLG parameter files each with an embedded list of auxiliary input files masks posdep files and initialization files etc The batch mode file can be loaded as a list of individual parameter files or generated automatically by the batch mode scripting engine This allows you to instruct LLG to run sequential problems per haps varying parameters or initial conditions between sequential runs SETTING UP THE BATCH MODE EXECUTABLE LLG s batch mode processor is embedded in the LLG executable kernel It uses the same engine as the GUI enabled LLG i e the same classes and files etc To set up LLG to run in batch mode e Create a new link to lig v2 exe using the task bar e When you are prompted for the command line add b to the end On a typical system the command line looks like D MIg v2 0 MMIg v2 exe b e When prompted to name the link choose something like Ig v2 batch Note For DOS friendly users you can open a DOS window change directories to the LLG executable directory and type the command Ilg_v2 exe b to obtain the same results The batch mode interface shown below appears with a bath file already loaded fe LLG Micromagnetics Simulator V2 0 I llgv2 0 work test Sample4 n MERA Loops LLG Micromagnetics Simulator v2 Batch Mode Processor 2 of 37 Land Satch Fie
299. rm gt gt gt gt gt YE Mx MxH i Y dM dt Tr ff M H gt gt o2 eff 1 02 M Here the gyromagnetic frequency y gw 2 is determined from the free electron value of w and the spectroscopic splitting factor g 2 The gyromagnetic frequency y the damping parameter a and the magnitude of the effective fields determine the time scales of interest For time domain simulations the free electron gyromagnetic frequency of y 2 1 78 x 107 Oe sec 1 is used The damping parameter a is not well known Values of o between 0 005 and 2 0 have been used to solve LLG The damping parameter was not found to change the equilibrium magnetization configurations in domain walls in uniform ferromagnetic systems 23 The effective magnetic field on each magnetic moment is deter mined from the total system energy Ej as gt m H o Eg M a The effective magnetic field incorporates all the effects of exchange anisotropy external fields and demagnetizing fields For the analysis of the equilibrium micromagnetic structure the differential equation need not be integrated directly Instead notice that for an equilibrium magnetization distribution dM dt 0 which implies that the effective field Hs must be parallel to the magnetization M The magnetization configuration can be relaxed iteratively by posi tioning each magnetization vector almost along the effective field vector direction throughout the mesh The initial cond
300. rogress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepCubicAxis_3_Y nArraySize Cubic Y axis3 m_nOffset 4 if m_bDoProgress UpdateProgressBar m fileStdio Write m pLLG gt m pPosDepCubicAxis 3 Z nArraySize Cubic Z axis3 4 48 LLG Micromagnetics Simulator User Manual Chapter 4 Loading Saving Files m_nOffset 3 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepRho nArraySize Resistivity m_nOffset 4 if m_bDoProgress UpdateProgressBar m fileStdio Write m pLLG m pPosDepAMR nArraySize AMR Coefficient m_nOffset 3 if m_bDoProgress UpdateProgressBar m fileStdio Write m pLLG m pPosDepGMR nArraySize Bi mear GMR Coefficient m nOffset 4 ifrm bDoProgress UpdateProgressBar m fileStdio Write m pLLG m pPosDep BiLinear nArraySize BiLinear GMR Coefficient m_nOffset 3 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDep_BiQuadratic nArraySize BiQuadratic GMR Coefficient m_nOffset 3 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepColor m_nSize sizeof COLORREF Color Table Key if m_bDoProgress m_pProgress gt StopProgress Success m_fileStdio Close return TRUE Current Mask t BOOL CDatalO WriteCurrentMaskFile2 01 t pChar pFileName t BOOL bAllocate t Int nMaskSize nIntSize n 3 nMaskSize m nSize sizeof t BOOL nintSize 3 sizeof t Int Open File if Im fileS
301. rotational hysteresis loops by checking the Uniform and Rotational Hysteresis Loop boxes Specify a value of the field using the Maximum External Field bars or edit boxes The vector direction of this field defines the angular coordinate of the first field point You can specify the Cartesian plane in which you want the field rotation to be constrained by using the buttons provided X Y Y Z or Z X The number of sample points is uniformly distributed around a circle The magnitude of the field is l wees The hysteresis loop will be plotted on a polar diagram with the magnetization displayed radially for each field direction An output file llg hys is created automatically An example of a rotational hysteresis loop field follows The field has been constrained to lie in the X Z plane The field values are H 2000 Oe Hy 0 Oe and H 1000 Oe with the st Points 21 The first field point lies at an angle of tan 1 2 LLG Micromagnetics Simulator User Manual 17 125 Chapter 17 Inputting Data Into LLG Hysteresis Uniform me fl 00 pf 00 Mrjjeje OO MO ome Wans DER M M HDs 38 MM 00060 Miele 00 ride 88 HeWel 0 ds 00000 Moie 00000 MM 0 0000 MiDel 88 MAMs 0000 FIGURE 56 Hysteresis Loop Views for a Uniform rotational Hysteresis Loop SPECIFYING LooP DIRECTION The hysteresis loop is a plot of two scalar variables H and M The magnitude of H is given by the sca
302. rrent Induced Field Current Pos Dep Ext Feld PosVep Optional View Options Boundary Cond Field Temp K Current Induced Field Current C Pos Dep Ext Field PosDep C E Shielded Ext Field View Polar C Shielded Ext Field View Polar t Mi Ehi H C Ri View dR R MR Loop ViewidH H FIGURE 105 Simulation view for H t and I t left and FMR right 23 178 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation Below examples of the time dependent magnetization magnetoresistance and suseptibility are illustrated for the cases defined above The magnetizations in color have r g b connected to x y z components of M FIGURE 106 M t and R t x r x g FIGURE 107 x H and x H LLG Micromagnetics Simulator User Manual 23 179 Chapter 23 Simulation MoviES PAGE Simulation Views Movies Computation Fields B Probe n z LLG Simulation File Options t AL Param File Illa v2 Ol work V rrott Dom File ECRIRE Conv File I llgfv2 ON work rrott llg Hys File I llgfv2 ON workv rrott 1l Movie File I llgfv2 ON work v rrott 50 Write Movie File Increment Catch The Transition 0 2 Edge Transition Increment Save Old Input File Save New Input File Save This Dom File FIGURE 108 Simulation Sheet Movies Page The Simulation Sheet Movies Page is where you specify movie options prior t
303. ructure for a Fe domain wall including the bulk Bloch wall and the N el cap INPUT SHEET MAIN PAGE 1 2 3 4 Initiate an LLG computation From the Main Page click the 2D button to use the 2D Green s Function as is appropriate for the study of domain walls Enter the dimensions of the problem X nm is 500 nm and Y nm is 500 nm Enter the discretization for the problem N is 70 and N is 70 INPUT SHEET COMPUTATION PAGE 1 2 3 4 Click the Computation tab Set the Convergence limit to 0 0001 and the Iterations to 25000 Choose Energy Slower and a Sequential search Exit by clicking Accept Changes INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 2 3 4 Click the Globals tab and click the Material Selector button Select Fe from the Materials Page Click Accept the Fe properties should be entered in the edit fields of the Globals Page Exit the page by clicking Accept Changes INPUT SHEET BOUNDARY CONDITIONS PAGE 1 2 3 Click the Boundary tab The structure runs infinitely in the Z direction In a domain wall the domains on either side of the wall fix the magne tization Enter the domain orientations on either side of the wall into the Boundary Conditions edit fields Enter 1 0 in the Mz edit field for Left X 0 and 1 0 in the M edit field for the Right XN boundary conditions Exit by clicking Accept Changes LLG Micromagnetics Simulator User Manual 38 243 Chapter 38
304. s 8 Now enter 2 in the edit field for Layer to specify the properties of layer 2 9 Set the Layer T nm Thickness to 10 for layer 2 10 Click the Material button at bottom center and select Fe from the Materials Page 11 Click Accept to return to the Layers Page Fe properties have been entered into the edit fields 12 Under Material Properties set A Exchange for Fe to 2 1 13 Use the color button to select pink LLG Micromagnetics Simulator User Manual 32 223 Chapter 32 Sample Problem 7 Multiple Layers with Demag Coupling in MRAM 14 At the upper right there is an edit field beneath Aj This is where you enter the exchange coupling parameter between the present layer layer 2 and the adjacent layers layer 1 or 3 Since there is no boundary layer layer 3 coupling is irrelevant However the interlayer coupling between layers 1 and 2 should be zero Therefore enter 0 0 into the edit field adjacent to Aij 1 This turns off the coupling between layers 1 and 2 Note that you can enter any coupling parameter including antiferromagnetic coupling Aij 0 0 15 Click the LOAD LAYER PROP red button to register your entries for layer 2 You must click the LOAD LAYER PROP button after you have entered each layer s properties IMPORTANT NOTE You must insure that The total thickness of the layers equals the total thickness of the structure The thickness of each layer is an integral multiple of the sub element width i
305. s Position Dependent Parameters to visual ize the parameters in the graphics window Click the Reset button if you want to clear the image colors and all of the parameters from Bitmap Page LLG Micromagnetics Simulator User Manual 22 159 Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETERS SHEET EDGE PAGE Main Params Exch Materials Graph Media BC Bitmap Edge Custom Input Custom Graph n Model 1 Af d B Model 2 A B x d C d 2 D x d 3 0 0 Distance nm 20 0 m Edge Magnetization E change Damping MagEdge A B C Modell B x 1 0 2 Model 2 ExchEdge 4 B e Model 1 1 Model 2 us Fix Torque AM Edge Distance dem 20 Edge Roughness Floughen Edge Amplitude nm i 20 Wavelength nm 50 Main Control Edge Is Unspecified FIGURE 80 Position Dependent Parameters Sheet Edge Page 22 160 LLG Micromagnetics Simulator User Manual Chapter 22 Inputting Data Into LLG Position Dependent Parameters SPECIFYING EDGE MAGNETIZATION AND EXCHANGE DAMPING The two formulas for specifying Edge Magnetization and Exchange Damping appear at the top of the Edge Page 1 Specify which layers you want to work with on the Position Dependent Parameter Main Page page 151 and whether you want to toggle fill parameters and layers 2 To scale the position dependent magnetization with the functional par
306. s e AC Currents superimposed or not Time dependent currents Time dependent current editor 10 Layers e An unlimited number of material layers 11 GUI input for layer boundary conditions 12 13 14 Time dependent h field e AC fields Fixed time fields Arbitrary waveforms and waveform editor 3D finite permeability shields e Imaging BC magnets Response to media e Cross track response Moving media Position dependent parameter editor Variable 3D resistivities Extended media model input editor Variable surface tiling coupling editor Parameter histogram viewer e BC parameter viewer Version 2 05 Released April 2001 with an Updated Manual With v2 05 you can 1 2 3 4 Examine convergence hysteresis or hysteresis part files in a 2D graphics environment Simulate a movie Extract hysteresis data from a movie file Edit movie files Version 2 05b Released Electronically March 18 2001 V2 05b features are 1 2 2D graphics Print the page e Copy graph to clipboard e Save graph to a bitmap file MFM imaging was changed for speed e To compute an MFM image enter Z height and mode then check the Compute MFM box The MFM mode will not be recomputed until this box is checked again each click results in one computa tion Since the same array holds all computed views if you have other computed views checked the MFM field data will be valid on the scre
307. s parameter limits of 104 file viewer 193 files examining contents of LLG 34 fonts setting for display 22 G gamma 94 gaussian random variable 101 152 153 155 Index 280 global parameters limits of 79 GMR bilinear and biquadratic 115 position dependent parameters 153 sample problem with 229 graph scaling gain 61 legend show 61 level 61 ortho 60 size 61 graph type 3D slice 60 3D surface 60 bitmap 59 cone 60 contours 59 domain 60 input cells 60 vertex cone 60 graphic properties setting 63 graphical animation file type 33 v1 input and output file format of 40 graphics determining properties of objects in 70 editing numerical values of 146 graphics screen splitting 53 Green s function 76 simulate domain walls using 219 guidelines for running simulations 184 for setting up problems and decreasing computation time 185 gyromagnetic torque visualizing 174 H H z dH z dz and d2H z dz2 important note regarding computation time 176 hangul and kanji environments installing LLG in 23 head fields 86 heff dm dt visualizing 174 h field files v2 input and output file format of 43 hysteresis and MR loops visualizing 172 hysteresis field four methods of specifying 123 v2 input and output file format of 45 hysteresis field and magnetization file type 33 v1 input and output file format of 42 hysteresis field profile file type 33 v1 input and output file format of 39 hysteresis file examining contents of 5
308. s Uniform H 1250 Oe Ny 21 Coupling Antiferromagnetic coupling across a non magnetic layer strength 400 0 Oe 0 16 uerg cm 34 230 LLG Micromagnetics Simulator User Manual Chapter 34 Sample Problem 9 GMR for Bilinear Interlayer Exchange between Platelets Md 1 0 Dueno CIE 10 0 5 MMs FIGURE 135 Magnetization Near Zero Field in 3D Arrows 34 231 LLG Micromagnetics Simulator User Manual CHAPTER 35 Sample Problem 10 Boundary Conditions Applied to a Thin Platelet This sample illustrates using boundary conditions for a three dimensional problem including creating and storing posi tion dependent field files It is a thin Permalloy platelet with permanent magnets on two sides INPUT SHEET MAIN PAGE 1 2 3 4 Initiate an LLG computation Enter the dimensions of the problem X nm is 250 nm Y nm is 100 nm and Z nm is 30 nm Enter the discretization for the problem N is 25 Ny is 10 and N is 3 Select Layers in the Structure Properties group box INPUT SHEET COMPUTATION PAGE 1 2 3 4 Click the Computation tab Set the Convergence limit to 0 0001 and the Iterations to 2500 Choose Time Faster and 2D Real FFT Method Click Accept Changes to log your changes INPUT SHEET GLOBALS PAGE AND MATERIALS PAGE 1 2 3 4 Click the Globals tab Click the Material button Select Permalloy and click Accept The Permalloy properties should be ente
309. s Section Near the Top of the Bulk Terminated Bloch Wall FIGURE 141 Magnetization Pattern in Bitmap and Contour Near the Top of the Bulk Terminated Bloch Wall FIGURE 142 Hysteresis Loops Taken along the Easy Axis and at 450 from the Easy Axis FIGURE 143 Time Dependence of Energies in Fast Rise Time Switching Field FIGURE 144 Midplane Magnetization ofthe Tip o ooococcocccncc RII Ih FIGURE 145 End and Mid shank Magnetization of the Tip 0 0 cece eI FIGURE 146 Midplane Magnetization ofthe Tip ooooococcocccoco II In FIGURE 147 End shank Magnetization and Field Dependence as a Function of Position Away from the Tip FIGURE 148 Magnetization Perturbed by the MFM Tip 2 IIR II FIGURE 149 3D Current Flow in a Bar with a Hole sssssele en FIGURE 150 3D Current Field in a Bar with a Hole slssesesseeee eh FIGURE 151 Media Magnetization Direction Cosines and Media Demagnetization Field FIGURE 152 Position Dependent Sheet MO Main Page FIGURE 153 Position Dependent Sheet MO Functional Temperature Probe Page s FIGURE 154 Position Dependent Sheet Ancillary Input Data Page 6 ee ee FIGURE 155 Position Dependent Sheet MO T Graphs Page 2 eee FIGURE 156 Magnetic Parameters for the Sample Problem FIGURE 157 Temperature Profile for the Sample Problem xvi LLG Micromagnetics Simulator User Manual
310. s and MR loops 172 Hz nm 176 integrated b 176 magnetization direction cosines 168 magnitude 168 position dependent external field 172 residuals change iteration 171 shielded external field 172 total torque 174 views page 167 Voronoi cells implementation of 156 vortex magnetization 3D 100 W warping 3D graphics 59 Windows 2000 installing LLG with 23
311. s and those of the previous iteration The residuals decrease as the problem solution is approached Visualizing the residuals can be very helpful when an instability occurs such as in the following cases e If the time step is too large a common instability involving exchange causes adjacent cells to oscillate from itera tion to iteration When residuals are visualized in Bitmap Graph Type adjacent rows of sub elements oscillate between red and blue e You might be computing a large structure that is responding slowly during the iteration process Or there may be a domain wall across your structure that is moving rather slowly You can use the view of the residuals to monitor the progress of this domain wall if the wall is moving the changes to the magnetization local to the wall are large and easily visualized e If your problem has loose spins that oscillate during a simulation as a result of a miscalculation of the appropriate mesh and set up parameters the view of the residuals allows you to identify which spin is loose EFFECTIVE FIELD With the Effective Field you can visualize the vector field whose projections are the normalized effective field vectors along the three Cartesian axes The effective magnetic field is the negative gradient of the energy density in a sub ele ment with respect to the magnetic moment in that sub element Therefore the effective field includes external fields exchange fields anisotropy fields demag
312. s of your problem You can use the GUI enabled LLG to look at your partially written movies or to load the convergence file into the 2D Graphics environment page 55 You can keep track of the details of your calcu lation by using these existing LLG tools SETTING UP A BATCH MODE PROCESS An LLG batch file is simply a list of llg param files You can use a standard editor to create this list you must use the full path name including the disk as DAMyDirectory MySubDirectoryMyFile llg param or use LLG to create the batch mode file for you The fundamental difference between batch mode processes and interactive processes is that in batch mode processes you must define the input variables prior to loading the parameter file into the LLG execution kernel EDITING BATCH FILES At any time while LLG is running in batch mode you can edit the contents of any parameter file set to run in the batch even if the file is already in the Files To Process list In this way LLG remains fully compliant to interactive changes up to the moment that the parameter file is loaded to run LLG has the capability of loading the following files at run time e lo mask mask file e lo posdep position dependent parameter files e lo dom initial angle files e lo inputhfield boundary condition field e lo inputhfield current field Batch mode processor allows the names of these files to be added to the end of the parameter file with a flag indicat in
313. s with and without Edge Correction The staircase effect can lead to erroneous switching modes and switching fields In the simple example shown above the hysteresis loop is computed for a 100nm x 100nm x 10nm Permalloy platelet oriented along and at 45 degrees to the Cartesian axes The edge corrected loop falls on the oriented loop in other words they are the same The stair case edge shows 100 error in the coercive field The size and orientation of this example were selected to demon strate the maximum effect due to the staircase approximation LLG Micromagnetics Simulator User Manual 22 163 Chapter 22 Inputting Data Into LLG Position Dependent Parameters POSITION DEPENDENT PARAMETERS SHEET BC PAGE Main Params Exch Materials Graph Media BC Bitmap Edge CustomInput Custom Graph de Boundary Condition Specification Select Boundary e Left X 0 Right Nx Front Y 0 Back Y Ny Bottom Z 0 Top Z Nz Mz 0 Set Boundary Conditions Remember To Select All Layers In Main Pos Dep Dialog Clear All FIGURE 83 Position Dependent Parameters Sheet Boundary Conditions Page The BC Page is for setting the boundary conditions for position dependent parameter problems 1 Select a region of interest using the drawing tool see page 148 Select the Boundary Condition that you want to change Set the boundary value in the Mx My and Mz edit boxes Check the Set Boundary Conditions bo
314. s you to include spin torques in your computation These spin torques are only active for 2D currents oriented in the Z DIRECTION In addition the polariza tion P and magnetization must be finite in the layers adjacent to the paramagnet defined as having M P 0 LLG Micromagnetics Simulator implements the spin torques according to the following equation e me gt gt gt gt dm 5 0t m X m xm LLG Micromagnetics Simulator User Manual 13 107 Chapter 13 Inputting Data Into LLG Current Here the magnetizations 1 and 2 are sequential along positive z J is the current density h is Plank s constant and e is the electronic charge Since this is an interface torque the A in the denominator is the thickness of the layer adjacent to the interface When J is given in Amp cm and e in coulombs the units are cgs and the post factor has units of a field The function g is given by Sloncewski as follows 3 1 2 2 4p 4P P Kr EEE EE DE 3 gt gt 2 2 gt gt 2 1L P 3 m m 16P 1 P 1 P 3 m m 16P P and P 0 40 0 35 0 23 and 0 12 at T 4K for Fe Co Ni and Gd respectively ie egge Wells g E FIGURE 49 Input Data Sheet Current Mask Editor 13 108 LLG Micromagnetics Simulator User Manual Chapter 13 Inputting Data Into LLG Current SELECTING 2D Quasi UNIFORM OR 3D CURRENTS You can select 2D Quasi Uniform currents or true 3D currents IMPORTANT NOTE When you
315. search can be implemented in an arbitrary sequence which provides access to states not normally probed in a parallel solution algorithm Second the eigenvalue for the solution to the differential equation leads to a more rapid convergence than the par allel solution algorithm For instance the sample problem with the file name of 3D samplet llg param solves for the magnetization in a 56 nm ferromagnetic cube of fictitious Fe beginning in a fixed planer vortex state The sequential mode one point method converges after 31 iterations while the parallel LLG method with maximum step size and acceleration converges after over 130 iterations 10 90 LLG Micromagnetics Simulator User Manual Chapter 10 Inputting Data Into LLG Computation Disadvantage The one disadvantage of the one point method is that the CPU time depends on N in the magnetostatic self field com putation The FFT Method can be 100 1 000 times faster for large problems even with a 10 100 times slower conver gence in the differential equation itself With the one point method the solution process can become unstable Large oscillations and a convergence residual that never decreases are evidence of instability In the worst cases of instabil ity the residual can reach 1 9 2 0 If this occurs while you are using this method the only stabilization scheme is to stop the simulation and restart the problem with a finer smaller sub elements grid When solving LLG direct
316. stinguish it graphically and to be sure that the parameters take effect This is an optional but highly recommended step Specify the position dependent parameters that you want to apply to the defined area of interest Apply the parameters including the selected color to the defined area of interest DEFINING AN AREA OF INTEREST WITH THE DRAWING TOOL To define an area of interest 1 Click the OGL Props tab then click the Orient tab in the Graphics Control at the bottom Set the Position of X Y or Z to establish the orientation projection of the layer or layers e f your structure has more than one layer indicate the layer that you want to work with the Slice bar which will reflect the number of layers in your structure If you established layer colors in the Layer Props Page they will be evident as you scroll through the layers NOTE This control is synchronized with the Layer Fill This Layer option in the Main Page You can apply addi tional Fill and Mask properties on the Main Page This activates the Drawing Tool Bar at the top The default color of the drawing pen is Red You can change the color to Black Green or Blue You can adjust the size of the pen as well nooo mz MENHNHE v gaze FIGURE 70 Position Dependent Parameter Editor Tool Bar Select the shape that you wish to draw The default is a rectangle Use the mouse to draw the shape As you move the mouse its position in nm will be output to the
317. t gt gt gt 2 gt gt gt 23232333A gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt ee 33 gt gt gt M 9 2 gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt a gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt A gt gt gt gt gt gt gt o A A A A A gt gt gt gt gt gt EE EE EE EE NN gt gt gt 3 gt S gt gt gt gt IIII gt SIR ka de d n da Ab Aa Ae A E A EW gt gt 3 gt 3 E gt h z zk D obo A 9 gt z 33 vcevu uzuzy y GA vvv NM FIGURE 144 Midplane Magnetization of the Tip pm o em en e e m mm gt gt gt a a mn en e e en si D Y gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt m4 0 A x cc A 85 3 gt gt gt SS aa 95 27 5 3 a H t i RE ES E KARR CR Ree ee eee eve RRR BR eK LK LK eK KE LK Tt pg g gg e r e r r e E r 4 4 4 4 4 amp EE amp amp SO amp I A AAP E gt A
318. t the initial magnetization off the X axis by 30 Click Accept Changes to exit and record your entries INPUT SHEET UNIFORM HYSTERESIS PAGE This problem has no static external fields and none of the layers is exchange pinned To complete the problem set up you need to specify only the hysteresis loop options 1 2 3 4 5 Click the Hys U tab Select the Uniform mode Set H Oe to 1250 0 Oe Set the Points on one branch to 21 Click Accept Changes to exit and record your entries Problem specification is complete Save your input file Run the problem and save a movie file SIMULATION SHEET Once the Simulation Sheet appears 32 224 LLG Micromagnetics Simulator User Manual Chapter 32 Sample Problem 7 Multiple Layers with Demag Coupling in MRAM Divide the screen in half and place the hysteresis loop in the upper pane 2 3 4 Divide the lower pane in half Click on the lower right pane Click the Modes tab and then click the color button CO next to 3D Slice Click the Orient tab then move the layer selection with the View slide bar You can visualize changes in layers 1 and 2 simultaneously Notice the complex hysteresis loop that results from the coupling between the layers FEATURES Structure 250 nm x 100 nm x 20 nm Sub Element 10 nm x 10 nm x 10 nm Discretization 25x10x2 Material Permalloy layer 1 and Fe layer 2 Relaxation 3D Complex FFTs Initialization Uniform magnetizatio
319. ta in a common temporary array You can view only one computed image at a time because the data are stored in a common area 23 176 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation FIGURE 102 Computed Imaging Mode Fields Arrow Slice x Div FIGURE 103 Computed Imaging Mode Fields and Divergence of M Bitmaps LLG Micromagnetics Simulator User Manual 23 177 Chapter 23 Simulation Ia Or uui ulatorvuntr X dHzidy X d2Hzidy2 X dHy dy X d2Hyidy2 X dHxidy X d2Hx dy2 FIGURE 104 Computed Imaging Mode dH dz and d H dz Bitmaps SAVING TO FILE To save any active view data to a file left click on the view then click the Save to File button to assign a file name H z dH z dz and d H z dZ are surface properties and data are stored as the top most slice in Z in the file the rest of the cell data are set to 0 0 IMPORTANT NOTE Current Field Files are saved with the current scaled to 1 microamp As LLG internally varies current with time all spatially dependent currents are derived from test currents of 1 microamp To recover true field values from the saved files multiply the saved field values by the real current in microamps TIME DEPENDENT FIELD H T CURRENT I T AND FMR VISUALIZATION When time dependent fields currents or FMR fields are used the simulation view page will change to reflect the simu lation mode Optional View Options Boundary Cond Field Temp K Cu
320. tdio Open pFileName CStdioFile modeWrite CStdioFile modeCreate Am fileException FileExceptionHandler amp m_fileException return FALSE Write Header String m_fileStdio Write amp m_cVersion 64 sizeof t_Char Write Integers n 0 m nXin 1 m nY n 2 m nZ m fileStdio Write amp n nIntSize Write Mask m fileStdio Write m pLLG gt m pCurMask nMaskSize Success m fileStdio Close return TRUE LLG Micromagnetics Simulator User Manual 4 49 Chapter 4 Loading Saving Files Movie Files t_BOOL CDatalO OpenMovieFile Open File if Im fileMovie Open m pLLG gt m pFileMaster gt IO WriteMovie CFile modeWrite CFile modeCreate amp m fileException FileExceptionHandler amp m fileException return FALSE Write Header String m fileMovie Write amp m cVersion 64 sizeof t Char Write Size m fileMovie Write amp m pLLG m nX sizeof t Int m fileMovie Write amp m pLLG m nY sizeof t Int m fileMovie Write amp m pLLG m nZ sizeof t Int Place Holder for Size m fileMovie Write amp m pLLG m nZ sizeof t Int Write Dimensions m fileMovie Write amp m pLLG m X sizeof t Double m fileMovie Write amp m pLLG m Y sizeof t Double m fileMovie Write amp m pLLG m Z sizeof t Double m fileMovie Write amp m pLLG m dX sizeof t Double m fileMovie Write amp m pLLG gt m dY sizeof t Double m fileMovie Write amp m pLLG m dZ sizeo
321. teProgressBar m_fileStdio Write m_pLLG gt m_pPosDepAnisotropyType nMaskSize Anisotropy Type m_nOffset 3 if m_bDoProgress UpdateProgressBar m fileStdio Write m pLLG gt m pPosDepUniaxialAxis X nArraySize Uniaxial X axis m nOffset 3 ifrm bDoProgress UpdateProgressBar m fileStdio Write m pLLG m pPosDepUniaxialAxis Y nArraySize Uniaxial Y axis m_nOffset 4 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepUniaxialAxis_Z nArraySize Uniaxial Z axis m_nOffset 3 if m_bDoProgress UpdateProgressBar m fileStdio Write m pLLG gt m pPosDepCubicAxis 1 X nArraySize Cubic X axis 1 m nOffset 4 ifrm bDoProgress UpdateProgressBar m fileStdio Write m pLLG m pPosDepCubicAxis 1 Y nArraySize Cubic Y axis1 m_nOffset 4 if m_bDoProgress UpdateProgressBar m_fileStdio Write m_pLLG gt m_pPosDepCubicAxis_1_Z nArraySize Cubic Z axis1 m_nOffset 3 if m_bDoProgress UpdateProgressBar m fileStdio Write m pLLG gt m pPosDepCubicAxis 2 X nArraySize Cubic X axis2 m nOffset 4 ifrm bDoProgress UpdateProgressBar m fileStdio Write m pLLG m pPosDepCubicAxis 2 Y nArraySize Cubic Y axis2 m_nOffset 3 if m_bDoProgress UpdateProgressBar m fileStdio Write m pLLG gt m pPosDepCubicAxis 2 Z nArraySize Cubic Z axis2 m nOffset 4 ifrm bDoProgress UpdateProgressBar m fileStdio Write m pLLG gt m pPosDepCubicAxis 3 X nArraySize Cubic X axis3 m_nOffset 3 if m_bDoP
322. tep until stability is reestablished THE TIME STEP LIMIT IS PRIMARILY A FUNCTION OF THE EXCHANGE COUPLING PARAMETER THE MAG NETIZATION AND THE SIZE OF THE SUB ELEMENTS PROBLEMS ON EQUIVALENT SYSTEMS SPECIFIED ON DIFFERENT GRIDS WILL HAVE INTRINSICALLY DIFFERENT TIME LIMITS ENTER YOUR CHOICE FOR THE TIME STEP IN THE EDIT BOX PROVIDED LLG Micromagnetics Simulator User Manual 10 91 Chapter 10 Inputting Data Into LLG Computation TIME INTEGRATION LLG supports four integrators e The crudest is an Euler Cartesian method which is the fastest and least accurate e The Rotation Matrices method is the integrator of choice for solutions where alpha is greater than 0 5 In other words when temporal dynamics are not being explored e The Cartesian Predictor Corrector integrator is a modified Haming predictor corrector which is the most accurate of the three integrators this scheme is a factor of two slower when alpha 1 and can be about a factor of 50 faster when alpha 0 01 Use this integrator for all problems where a lt 0 5 e The Gauss Seidel Stable method is a semi implicit first order integration scheme developed by Weinan E and co workers at Princeton The integration time steps can be much larger on fine grids using this method and is recom mended for computations on extremely fine grids LLG will not check your time step for stability when you use this method You must experiment with a small problem at the same grid s
323. th the Lev checkbox The level indicator is active only in bit map and contour modes The level indicator overlays a white contour at the level selected This tool is useful for demarking individual equidata value lines i e equimagnetization lines The value of the contour is displayed in the edit box adjacent to the check box This adds a quantitative visualization feature to your data analysis e Legend This feature allows you to toggle the Legend on and off for Bitmap Contour and Domain Graph Types LLG Micromagnetics Simulator User Manual 5 61 Chapter 5 LLG Environment OGL PROP SHEET ORIENT PAGE The OGL Modes Prop Sheet Orient Page is where you translate and rotate the view e X YandZ With this control you can translate the position of the view You can shift the center view of the 2D or 3D coordinate system with the X Y and Z slide bars or edit boxes The default sets the structure in the center of the window The units are in nm e Slice This allows you to select the slice number to view e Theta and Phi This allows you to select the view orientation The angles are defined in the conventional spheri cal polar geometry Theta and Phi are given in degrees M Mg sin0 coso My M sind sing M Ms cos LLG uses color to establish orientation the colors of the coordinate axes are X Red r Y Green 9 rgb lt gt xyz Z Blue b e Slice X Y Z This allows you to select the 2D projection For ex
324. the 3D Complex FFT Method button to perform complex 3D factors of primes FFTs This method is intrin sically slower than 2D Real FFTs for systems with few layers however it will be faster for true 3D structures The advantage is that the factors of primes gets the size close with minimal buffering PS TimE STEP MAX The Time Step must be selected to insure stability in the solution of the LLG equations Once the simulation has been started LLG computes the Time Step for the maximum radius of convergence for the problem If your Time Step exceeds this value you will be prompted to change it Note that for many problems you will want to select a Time Step smaller than the maximum Time Step You might need to experiment with this parameter to tune it for your problem Use DUAL PROCESSORS If your computer has dual processors this feature will be enabled If you want to use both processors check the Use Dual Processors box 10 92 LLG Micromagnetics Simulator User Manual Chapter 10 Inputting Data Into LLG Computation COMPUTATION PARAMETERS LLG uses Computation Parameters to solve the differential equations With the exception of Gamma Alpha and temperature Temp T the parameters help define an equilibrium magnetization configuration Choosing an exit crite rion that is too large can lead to erroneous results so care should be exercised when you enter this parameter There are two simulation methods relaxation and time int
325. the boundary magnetization Exit by clicking Accept Changes LLG Micromagnetics Simulator User Manual 31 219 Chapter 31 Sample Problem 6 Simulation for Asymmetric Bloch Wall in Permalloy INPUT SHEET COMPUTATION PAGE 1 Click the Computation tab 2 Set the Convergence limit to 0 0001 and the Iterations to 2500 3 Choose the Energy Slower method and the Sequential search method 4 Click Accept Changes to exit INPUT SHEET INITIALIZE PAGE 1 Click the Initialize tab 2 Choose a Narrow Wall whose orientation is X Directed as the initial condition by clicking the appropriate buttons in the 2D Narrow or Wide and 2D Direction fields respectively 3 Close the page by clicking Accept Changes 4 Complete the initialization by clicking the Begin Simulation button COMMENTS Notice that the sub element size was specified to be 10 nm This is near the upper limit that yields converged solutions for Permalloy Rerun this sample with 80 and 20 sub elements per side to see if any details were missed by selecting a coarse mesh Rerun this sample again with a coarser mesh of 32 and 8 sub elements per side to see if you can make the problem unstable This sample problem is difficult to make unstable with the 1 Pt minimization method however if you coarsen the mesh the solution eventually becomes unstable The structure on the screen will be the asymmetric Bloch wall characterized by the tight vortex structure whose axis runs parall
326. the legend toward the right of the OpenGL window for the color coding The cosine sine waveform is indicative of a rotational field sweep Click the 3D Field View button This plots the field in 3D in a circle about the origin where each point signifies the tip of the field vector during the rotational sweep The direction for the magnetization component in the polar hyster esis loop display is always along the direction of the field The polar output displays the magnitude of the magnetiza tion along the field as the radius as a function of the angle of the field You can toggle the view during the simulation to see the magnetization as a function of the field angle in a strip chart as well Click Accept Changes to complete the hysteresis specification which returns you to the Main Page No other mod ifications to the default settings are required to run this problem Click the Begin Simulation button If you have not saved the new input parameters LLG will prompt you to do so Respond as in Samples 1 2 and 3 SIMULATION SHEET SIMULATION PAGE The Simulation Sheet Simulation Page is activated and a top down view of your Permalloy platelet appears on the screen 1 2 Select the Arrow Graph Type to see the surface magnetization on the platelet surface Click the Views tab Right click on the OGL window and select Split Window Horizontally Left click on the upper pane of the OGL window view number 1 should appear at the top of the Vi
327. this you can zoom into and out of the view You can change the magnification 0 1 lt magnification lt 10 of the view For convenience this control is on both the OGL and Modes Pages Gain With this you can scale data linearly to amplify sensitivity when viewing bitmaps or contours This is useful for visualizing small changes in data such as ripple For convenience this control is on both the OGL and Modes Pages OGL Lights With this you can toggle the OGL Lights on and off The best 3D Cone and Vertex cone viewing is with the lights on It is recommended that you turn the lights off for all other views m 3D Object Props View Properties Length of Cons Radius Size oF Gain OGL Lights On ie Off FIGURE 18 OGL Property Sheet OGL Page LLG Micromagnetics Simulator User Manual 5 63 Chapter 5 LLG Environment OGL PROP SHEET COLOR PAGE The OGL Modes Prop Sheet Color Page is where you set and alter the OpenGL color properties LLG s view is true 24 bit color e You can modify the colors of the foreground and background with the Red Green and Blue controls as well as with the Hue Saturation and Brightness controls the values of which must be between 0 0 and 1 0 Torestore the control to the original settings click the Revert button e The foreground and background must be changed independently the Front Out Back In button allows you to toggle betwe
328. tialization amv all AECE SIE ell leen EME E FIGURE 40 Input Data Sheet Initialize Page 11 98 LLG Micromagnetics Simulator User Manual Chapter 11 Inputting Data Into LLG Initialization 3D UNIFORM MAGNETIZATION You can initialize the magnetization to be oriented uniformly along any of the three Cartesian directions by checking the appropriate button e The sign of the magnetization can be altered with the Positive and Negative Sign On Uniform buttons e Align the magnetization arbitrarily along any direction by modifying the entries in the Theta and Phi edit boxes The magnetization direction cosines in LLG are M sin0cosQ M sinOsino M cos0 AAA AMAA AAA SS AMARA SSES AAA AAA AAA AAA AA AA SS SS SS SS SS PAA AA AAA AMA AA AMMA MAMA MAMMA AAA AAA AAA AAA AAR AA SS SS SS SS SS SS AFA AAA AAA AAA SS SSES SS SS SS SS AAA AA AA AAA SSES SS SS SS SS AAA AAA SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS AAA AAA AAA AMA MAA SS SS SS SS SS SS SS SS SS SS AAA RA SS SS SS SS SS SS A ASS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS AAA AS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS AB RES SS MAA SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS AR AR RAR RAA RBS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS ASS EE EE E EE EE EE EE EE EE EE EE E EE EE EE EE EE AA AAK III E EE EE EE EE EE EE EE EE EE EE E EE EE EE EE E EE EE EE EE GNE N
329. time energy minimization method specify either a Sequential or Random search by checking the appropriate button TIME FASTER When the Landau Liftshitz Gilbert equations are being solved time appears explicitly as a parameter You can solve the equations directly in time by selecting an exit criterion associated with reaching equilibrium or by selecting an exit criterion at a specific time Pure time methods are integrated for a fixed time interval whereas equilibrium time meth ods are generally focused on obtaining equilibrium magnetization states When you select pure time integration the program determines an approximate radius of convergence for the differential equations This is presented as one maximum time step The program warns you not to set the time step larger than this limit as doing so makes the solu tion intrinsically unstable Linear differential equations can be integrated using implicit method integrators to achieve unconditional stability Unfortunately this is not the case with LLG equations as they are coupled non linear differential equations A robust Gear s method implicit integration scheme has been implemented in the program but the maximum step size was not significantly larger than the stability limit for the explicit scheme Since inverting and solving the Jacobian matrix slows down the calculation significantly this method was abandoned If your solution becomes unstable and oscillations occur decrease the Time S
330. tive the internal energy due to anisotropy will always be positive The Uniax ial energy density is written as E Kyo 1 m a Kua 1 m a where a is a unit vector along the easy direction The interface anisotropy has the form E 1 2K m m The interface effective field is simply K m which favors out of plane magnetization when K 0 This is the convention in LLG 14 116 LLG Micromagnetics Simulator User Manual CHAPTER 15 Inputting Data into LLG Layer Boundary Conditions The Layer Boundary Conditions Page allows you to define external sources for the differential equation These boundary conditions are identical in function to the Global Boundary Conditions described in Chapter 9 However when you select a problem with layers you can specify Boundary Conditions for each layer individually For example in a magnetic sensor problem you might have a permanent magnet abutting the lower half of the stack A simple way to simulate a permanent magnet is to specify boundary conditions with the magnetization of the boundary pointing along the direction that the permanent magnet is magnetized If the magnet is not exchange coupled to the stack sim ply use the mask tool to isolate the sensor from the boundary with dead M 0 cells The table below summarizes the input variables The Input Sheet Layer BCs Page is shown on the following page As in the Global Boundary Condi tion Page you can read boundary condition files by
331. tmaps eee eee 177 FIGURE 104 Computed Imaging Mode dH dz and d2H dz2 Bitmaps 178 FIGURE 105 Simulation view for H t and I t left and FMR right 178 FIGURE 106 M D nd R D e eL etes Sak de te rt fog er ota e RR 179 FIGURE TOZ7 Hand Ele Saarem reke RR beUo EE Ede e Eus ede 179 FIGURE 108 Simulation Sheet Movies Page ococcccccccn ranerne 180 FIGURE 109 Simulation Sheet Computation Page 1 eet 181 FIGURE 110 Simulation Sheet Fields Page 6 teens 182 FIGURE 111 Simulation Sheet B Probe Page ok vanner rer ra nakne 183 FIGURE 112 Simulation Sheet Movie Page Simulate a Movie Option o ooocccoccccc o 186 FIGURE 113 Batch Mode Interface 187 FIGURE 114 Batch Page of Input Sheet for File Name Specification 189 FIGURE 115 Batch Mode Scripting Interface liliis 190 FIGURE 116 Scripting Range Vector and Scalar Menus 191 FIGURE 117 Dynamical Data View losses 193 FIGURE 118 LLG File Viewer sssesle Rr 194 FIGURE 119 Movie Player Sheet Movie Player Page tees 196 FIGURE 120 Manual movie splitter lislleslel RR eee 197 FIGURE 121 Movie Player Sheet Extract Hysteresis Loops Page 1 eee 198 FIGURE 122 Movie Viewer Sheet Edit Movie File Page ssssleee eee 199 FIGURE 123 Surface Magnetization Effective Field in 3D Arrows and Change Pattern in 3D Arrows 203 FIGURE 124 Demagnetization Fi
332. ttom side Y min allowing a semi finite terminated solid to be simulated NOTE This feature is not presently imple mented in v2 which is the same as in v1 SPECIFYING SHAPED BOUNDARIES For many problems LLG s stepwise approximation to the shaped boundaries changes the details of the switching behavior To approximate the solution for shaped boundaries better check the Enable Shaped Boundary box This allows you to specify one globally shaped edge in the Position Dependent Parameters Sheet However this requires 8N extra sums in the computation of the demagnetization field LLG computes the all orders demag field from the near est neighbors that are shaped into n gons a hexagon is the largest number of sides This type of solution allows you to get approximately the same coercive field for structures fixed to the grid or for structures rotated with respect to the grid Refer to the material on Position Dependent Parameters Chapter 22 for the operational details Fix H K 0 PER 3D COMPLEX Use this option to fix the k y 0 H field in the periodic solution usually less than 1 Oe Must use 3D complex FFTs LLG Micromagnetics Simulator User Manual 9 87 CHAPTER 10 Inputting Data into LLG Computation d y hd p TA Z WW Lan mdp GELT n VARIA Vlt Wt E Y Jd IA P biben P ut The Computation Page is for specifying the computational scheme for solutions There is an energy minimization pro cedure that
333. tton e To retrieve a material select it from the drop down menu The name and properties appear in the edit boxes e Click Accept to load the parameters into the Globals or Layers Page To clear the material click Reject MANAGING THE MATERIALS DATABASE The files are ASCII and can be edited with the LLG File Editor Notepad WordPad or a word processor Once a data base file has been loaded the material properties remain in the drop down menu until you finish the problem You can delete any item by selecting it from the list then clicking the Delete Item button Clicking the Delete All button clears the entire list You can enter up to 1 024 materials into a single database file you can have as many database files as you wish Once data has been entered you must click the Accept button for the data to change the LLG data structures If you do not you will lose your changes when you leave this property page Click the Main Control button to return to the Input Data Sheet Main Page at any time but remember to click Accept before leaving this page to change data 8 84 LLG Micromagnetics Simulator User Manual CHAPTER 9 Inputting Data into LLG Boundary Conditions You can specify Boundary Conditions uniformly on any or all of the six sides of a 3D Cartesian structure and on the left and right sides of a 2D structure When boundary conditions have been specified the boundary elements are exchange coupled to the Simulation Volume
334. tton to store it as a standard LLG movie INTERPOLATING A MOVIE With LLG you can interpolate an existing movie onto a new grid You can refine the grid or coarsen the grid Also you can extract a piece of the structure in an existing movie and make that piece into a new movie The size and grid density of the existing movie are shown in the edit boxes to the left e Specify the new grid density in the active Nx Ny and Nz edit boxes e Extract a piece of the existing movie by specifying the region in the following edit fields e Xf nm right side Yf nm back side e Xo nm left side e Yo nm front side e Zf nm top side e Zo nm bottom side IMPORTANT NOTE Clicking the Interpolate button prompts you for a file name for the new movie If you do not choose a new file name you risk overwriting your data LLG Micromagnetics Simulator User Manual 25 199 CHAPTER 26 Sample Problem 1 Basic Data Input for a Permalloy Cube This is the simplest of all problems to run The structure is a single material and contains no boundary conditions external fields or sources of any kind It can be initiated by entering the size and discretization of the structure in the LLG Input Sheet Main Page For all other features use the default NOTE Your LLG CD contains all sample problems in the Sample Files subdirectory within LLG s installation directory The prefix for each sample file is Sample INPUT SHEET MAIN PA
335. tual material layer number COLOR CODING Yellow indicates active cells and blue indicates inactive cells DETERMINING IF THE DEMAGNETIZATION EDGE IS UNSPECIFIED To compute the properties of shaped boundaries see page 87 you must specify one boundary to define the shaped edges LLG states on the bottom of the menu whether or not this shaped edge has been defined READING AND SAVING MASK FILES Mask files are binary files that contain sequential integer fields with ones and zeros You can load an lg mask file using the Read Mask button If the requested mask does not have the same dimensions as your problem it will be interpolated onto the existing grid This is a binary or digital interpolation You can save a mask file at any time with the Save Mask button Closing the Mask Sheet Once you have completed your problem specification it is highly suggested that you save your parameters file using the Save Mask button Then you must click Accept Changes if you wish your changes to be recorded Finally you must click Close Picker Tool to close the Mask Editor LLG Micromagnetics Simulator User Manual 21 141 Chapter 21 Inputting Data Into LLG Mask Editor MASK EDITOR SHEET BITMAP PAGE Main Bitmap Edge SuperEgg rm Bitmap For Mask Position Dependent Parameters Load Bitmap File Load Jpeg File Load Targa File Click the Open button to load the files in the menu above Stat Width 344 Col
336. two cells Artifacts of a mesh that is too coarse manifest themselves as switched lines of cells that is as arbitrary and unphysical 180 domain walls They appear because this configuration like total alignment is torque free Methods are being tested to remove these artifacts from the program in a systematic physical and rigorous way An interim solution has been provided introducing roughness or regularities necessarily breaks symmetry and alleviates the problem When you select Exchange Corr LLG linearly interpolates the magnetization onto a finer grid whose grid spacing is given by the correlation length This changes the scaling of Hex from 1 D to 1 D This is non physical since the exchange stiffness is unnaturally increased Although you might be able to recover an equilibrium magnetization distri bution switching field studies hysteresis loops will not yield correct values IMPORTANT NOTE Do not use Exchange Corr for hysteresis loops It is only for finding an equilibrium magnetization state or for seeding a fine grid study Please remember to click the Accept Changes button if you wish your inputs to update the LLG parameters used in the calculation LLG Micromagnetics Simulator User Manual 10 95 CHAPTER 11 Inputting Data into LLG Initialization The Initialize Page allows you to specify the initial preconditioned state of the simulation Choosing the correct initial magnetization configuration can sa
337. ulation Sheet Fields Page You can update field parameters during a calculation Refer to Chapter 12 Fields page 75 for a complete discussion of the parameters on this page 23 182 LLG Micromagnetics Simulator User Manual Chapter 23 Simulation B PROBE PAGE Main Views Movies Notes Comp Fields B Probe de LLG Simulation Field Probe Cl Point 1 Point 2 0 x nm 0 0 vinm 0 D z nm 0 2 N Points Scan Magnetic Fields E valuate Line Scan H De B Oe Record Line Scan Internal Arrays Evaluate Internal Arrays FIGURE 111 Simulation Sheet B Probe Page You can use the B Probe Page to calculate the B and H fields anywhere inside or outside of the Simulation Volume To sample the field at one point enter the coordinates in nanometers into the Point 1 edit boxes and click the Evaluate Point 1 button The B and H field components will appear beneath H Oe and B Oe To store a line scan enter the starting and ending point coordinates in the N Points edit box Click the Evaluate Line Scan button and you will be prompted for a file name in which to store the line scan data When computing fields inte rior to the Simulation Volume you MUST be sure that the sampling point coordinates are coincident with the locations of the magnetization moments in the grid Since this calculation mode uses the fields from point dipoles the field value will begin to div
338. using Fourier transforms on the Cartesian grid The additional expense to compute the demag edge is 11 x n where n is the number of cells in other words the penalty is linear in the number of cells To define the demag edge you must first mask the cells that are external to the region Once the cells are off right click on the shape and select Specify Selected Region for Demag Edge Calculation LLG will turn on any cells that are partially cut and the polygonal discretization of the boundary cells will shown LLG Micromagnetics Simulator User Manual 22 161 Chapter 22 Inputting Data Into LLG Position Dependent Parameters IMPORTANT NOTE With demag edge correction and Fourier transform methods for computing the demagnetization field the first row of cells outside of the material will not have the correct demagne tization field values To save time the linear sums over the neighboring shaped edges for those cells in vacuum are omitted Interior fields are correct For energy methods of solving LLG demagnetiza tion fields are never computed in vacuum A DEMAGNETIZATION EDGE PROBLEM An example of the edge demagnetization problem is demonstrated below The demagnetization field is computed along a row of cells adjacent to an edge of a 1 micron square by 20 nm thick Permalloy platelet This computation was done for aligned grids using 5 and 10nm cell sizes and for 45 degree oriented platelets with and without the edge cor rection I
339. ve time For 2D and 3D cases you can select a Random start This Page gives you another opportunity to load a starting file as the initial condition Note that unless you have loaded an llg dom file sub elements that are subjected to a pinning field are automatically initialized along the direction of the pinning field READ FROM FILE AND INPUT FiLE NAME The Read From File and the 3D Uniform Transition and Vortex Magnetization buttons are mutually exclusive You can select only one Once you select the Read from File option you can input a file through the Input File Name but ton This is the same as the Read Angle Config on the Main Page Loading these angles from a file allows you to start with any predefined magnetization distribution or to continue a computation that may have been terminated prema turely If the loaded file does not have the same discretization as the problem you wish to run you will be prompted to indicate whether or not you want to interpolate the old data onto the new grid In addition you can explore the effect of changing input parameters or other input specifications on a particular equilibrium magnetization structure DESCRIPTION VARIABLE LIMITS Theta 0 180 0 180 Phi Q 360 lt q 360 Transition Number Ntransition 1 lt Nyransition 10 Random Frac All Cases frandom 0 0 frandom 1 0 LLG Micromagnetics Simulator User Manual 11 97 Chapter 11 Inputting Data Into LLG Ini
340. well When you click on an OGL window the properties in the window update the graphics controls Each window has its own set of OGL properties and the graphics utilities can be used to modify them There are four main sheets 1 OGL Props Sheet 2 Color Sheet 3 Information Sheet and the 4 Selector Sheet Summaries of the functions of each sheet and its pages follow 5 58 LLG Micromagnetics Simulator User Manual Chapter 5 LLG Environment OGL PROP SHEET The OGL Prop Sheet controls all essential OGL functions There are four sub pages 1 Modes 2 Orientation 3 OGL Properties and 4 Color You can toggle between the pages by clicking the appropriate labeled tab OGL PROP SHEET MODES PAGE The OGL Modes Prop Sheet Modes Page is where the display type is set Several other important OGL features can be set using the Modes Page Graph Type r Graph Type Bitmap Contour e 3D Slice 3D Surface Domain E Input Cells Overlays Color Contour Arrow 3D Objects e Arrow i e Cone Ortho Vertex UnMask r Graph Scaling Size Gain H Lev Legend Box Visible yq ___________ ken Lei We N Eh oe 1 Shield Visible FIGURE 16 OGL Property Sheet Modes Page DUE Modes 2L Orient oGL EH Color The Graph Type allows you to control how the data are viewed which is key to their interpretation This is activated a
341. x to activate the boundary condition filler a PS YS BN Right click the region of interest and select Fill Region Closing the Position Dependent Parameters Sheet Once you have completed problem specification it is strongly recommended that you save your parameters file using the Save File button Then you must click Accept Changes if you wish your changes to be recorded Finally you must click Close PosDep Tool to close the Position Dependent Parameters Sheet 22 164 LLG Micromagnetics Simulator User Manual CHAPTER 23 Simulation The Simulation Sheet has six pages where you can fine tune your computation Once you have specified your prob lem and started a computation LLG computes the magnetostatic field coupling matrices and appropriate FFTs if needed The Simulation Sheet Simulation Page is the master computation page From the Simulation Page you can toggle between running Start To Compute and pausing Pause your problem You can visualize your problem as it evolves Turn Graphics On or just compute Turn Graphics Off Remember for faster computation speed turn the graphics off PROGRESS STATUS INDICATORS After every functional iteration LLG updates the Progress Status Indicators From one iteration to the next the Residual is the largest change in any normalized magnetization vector This is compared against the Convergence cri teria Each contribution to the total energy is displayed separately so that you c
342. yer tt p m Boundary Conditions Use Uniform Mx My Mz Left X 0 0 000 0 000 0 000 Right X Nx 0 000 0 000 0 000 Front Y 20 0 000 0 000 0 000 Back Y Ny 0 000 0 000 0 000 Bottom Z 0 0 000 0 000 0 000 Top Z Nz 0 000 0000 0 000 Read Write File Input File Name Ouput File Name File m Periodicity Periodicity Directions Continuous BC for 2D Periodic AlongX 17 Front v 0 Continuous Periodic Along Y Periodic Along Z r Shaped Boundary Enable Shaped Boundary Accept Changes i X Reject Changes FIGURE 52 Input Data Sheet Layer Boundary Conditions Page SPECIFYING BOUNDARY CONDITIONS You can specify Diriclet Boundary Conditions uniformly on any or all of the six sides of a 3D Cartesian structure and on the left and right sides of a 2D structure When boundary conditions have been specified the boundary elements are exchange coupled to the Simulation Volume If any of the boundary condition magnetization components is nor mal to the boundary surface the magnetostatic stray field from the elements is computed and added to the energy You can visualize the stray field in the Simulation Sheet covered in Chapter 23 The boundary condition inputs are Left Boundary Condition on X 0 plane Right Boundary Condition on X Xmax Nx Bottom Boundary Condition on Y 0 plane Top Boundary Condition on Y Ymax Ny Back Boundary Condition o
343. you create any type of uniform uniform rotational or non uniform hysteresis field the values of the fields can be output to a formatted ASCII file lo hysfield by using the Save Input File button You can generate a cata logue of field profiles that you commonly use Use the Name Output File button if you want to rename the hysteresis data output default file llg hys When you read in a file the new data once saved become part of the llg param file Therefore when you use the file in the future you are not required to re input the hysteresis field unless of course you change it Please remember to click the Accept Changes button to record your changes to LLG s internal data structures LLG Micromagnetics Simulator User Manual 19 133 Chapter 19 Inputting Data Into LLG H t and FMR SPECIFYING TIME VARYING POSITION DEPENDENT FIELDS By checking the Scale Pos Dep Field check box LLG will after computing the coupling matrices prompt you for a position dependent input field file The time and position dependent field that results uses the input from this Page to scale the data as follow HEG y x t H pos x y z H t in dialog Hy x y x t Hypos x y z Hy t in dialog Hz X y xyt Hzpos x y z Hz t in dialog In this way you can simulate write head field time dependences on media You cannot simultaneously scan a uniform field in time and a position dependent field in time However you may use the MRAM fields as in
344. you to save and recall current sequences that you create using the I Mask Editor A graphical representa tion of your data appears in the OGL window as you specify your current data When you are satisfied with the time sequence save your data by clicking the Save Input File button or recall your data using the Read Input File button SPECIFYING A TIME INDEPENDENT CURRENT You can specify a current in microamps for 2D current flow This current will be the 2D constant current when Time Dep Current is not selected In this case the 2D I Direction will indicate down which axis the current will flow SPECIFYING A TiME DEPENDENT CURRENT You can enter a time dependent current for both 2D and or 3D currents using the Mask Editor 1 First you MUST check the Enable I t check box to activate the time dependent current mode In the 2D case the current will flow down the axis specified by the 2D I Direction When time dependent currents are active you can specify a time dependent current signal that may persist for up to 16ns The time dependent currents are input in intervals 2 Specify the time interval in the Time Interval Specified edit box starting with the first Once you have specified all of the time intervals you can use the arrow keys to scroll through them and to examine the specifications 3 Specify the current limits at the end points time limits of the current step in microamps in the T 1 ps and or T 2 ps edit boxes Times ar
345. zation direction such as in a domain appear as one color This is specified in the Color Sheet Wheel Page Input Cells This shows the input configuration Overlays The Overlay configurations are superimposed on the selected Graph Type Color You can apply color to regions with position dependent parameters or layered parameters You specify the colors themselves on the Position Dependent Properties Sheet Params Page and the Layer Props Page How ever these colors appear in the graphics window only when you ALSO check the Color Overlay box in the Graph ics Control This can be useful when analyzing complex structures Arrow This control is active for Domain Bitmap and Contour Graph Types when 3D warping is NOT selected The Arrow Overlay superimposes an arrow slice on top of the Domain Bitmap and Contour Graph Types Contour This control is active for Domain and Bitmap Graph Types when 3D warping is NOT selected The Contour Overlay superimposes a contour map on top of the Domain or Bitmap Graph Type Unmask This control allows you to visualize computed fields in regions where the magnetization cells have been turned off with the Mask Editor see page 115 When you check the Unmask Overlay box you can visualize the magnetic fields in the holes and in regions where M 0 that are otherwise not visible 3D Objects There are three glyphs for rendering 3 dimensional objects You can toggle between orthographic and projection

LLG User Manual v2.50

Contents

Download Pdf Manuals

Related Search

Related Contents