OOMMF Standard Problem 4 Details

The simulation run that produced the µMAG Standard Problem 4, Field 1 (170° from positive x-axis) movies used the OOMMF 1.2a1 version of mmSolve2D with the following MIF input file:
   # MIF 1.1
   damp coef:0.02
   anisotropy type:uniaxial
   anisotropy init:constant
   anisotropy dir1:1 0 0
   anisotropy dir2:0 1 0
   demag type:constmag
   part height:500E-9
   part width:125E-9
   part thickness:3e-9
   part shape:rectangle
   cell size:3.125e-9
   init mag:avffile prob4-start-3.125nm.omf
   base output filename:prob4a
   magnetization output format:binary 4
   total field output format:binary 4
   data table output format:%.15g
   randomizer seed:0
   max time step: 0.2e-12
   field range: 0 0 0 0 0 0 0 -torque 1e-9
   field range: -0.0043 -0.0246 0 -0.0043 -0.0246 0 5000 -time 1e-12
Notice that the control point specification '-time 1e12' was used to generate output every picosecond. The initial state, taken from the input file prob4-start-3.125nm.omf, is an s-state obtained by relaxing to equilibrium using a large damping factor. This equilibrium is checked by the first control point (control point spec '-torque 1e-9')

The MIF file for Problem 4, Field 2 (190° from positive x-axis) was the same except for the magnitude and direction of the applied field.

To produce the divergence image movies, every fifth magnetization state output file (i.e., one every 5 ps of simulation time) was converted from OVF to bitmap format using the OOMMF command line tool avf2ppm with the following plot configuration file:

   # avf2ppm Plot Configuration File     -*-Mode: tcl-*-
   # This file should only be sourced from within another
   # Tcl application. Check to make sure we aren't at the
   # top application level
   if {[string match [info script] $argv0]} {
       error "'[info script]' must be evaluated by an\
              mmdisp-style application"

   # Plot configuration array
   array set plot_config {
       colormaps  { Red-Black-Blue Blue-White-Red   \
                    Teal-White-Red Black-Gray-White \
                    White-Green-Black Red-Green-Blue-Red }
       arrow,status       1
       arrow,colormap     Black-Gray-White
       arrow,colorcount   0
       arrow,quantity     z
       arrow,autosample   0
       arrow,subsample    5
       arrow,mag          1.25
       arrow,antialias    1
       pixel,status       1
       pixel,colormap     Blue-White-Red
       pixel,colorcount   225
       pixel,quantity     div
       pixel,autosample   0
       pixel,subsample    0
       pixel,mag          1
       misc,background    white
       misc,drawboundary  1
       misc,margin        10
       misc,width         640
       misc,height        192
       misc,crop          0
       misc,zoom          0
       misc,rotation      270
       misc,datascale     100000
Bitmap images for the XY and YZ movies were made similarly, but with the appropriate change to the 'pixel,quantity' field in the avf2ppm configuration file.

One fine point: The MIF file above places the long axis of the sample parallel to the simulation y-axis, because mmSolve2D runs more efficiently with that orientation. In the µMAG Problem 4 specification, however, the long axis is horizontal. The necessary coordinate rotation is performed by avf2ppm, via the 'misc,rotation 270' option.

The QuickTime movies were produced using the SGI makemovie command with 'qt_video' compression and spatial quality set to 0.1. The MPEG movies were made using the free mpeg_encode program, with the following parameters file:

   PATTERN              IPPPPPPP
   OUTPUT               output.mpg
   INPUT_CONVERT        *
   GOP_SIZE             16
   INPUT_DIR            tmp
      *.ppm [0000-2005+5]
   PIXEL                HALF
   RANGE                40
   BSEARCH_ALG          CROSS2
   IQSCALE              1
   PQSCALE              6
   BQSCALE              16
   FRAME_RATE           30
   GAMMA                0.75

The MPEG movies are similar in size to the QuickTime versions, but the sharp edge details in the magnetization arrows are better preserved by the QuickTime compression algorithm.

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Date created: March 1, 2001 | Last updated: April 27, 2011    Contact: Webmaster