OOMMF Tutorial Series: Homework

Session 3 Homework

Write a MIF file:

Using the equilibrium state from the Session 2 homework as the initial state, set up an STT simulation using the Anv_SpinTEvolve extension with these parameters:

1. u=100 m/s
2. alpha=0.1
3. beta=0.04

See the Anv_SpinTEvolve web page and sample problem to get started. (Note: This extension is installed by default in all standard OOMMF releases.)

Run simulations:

The skyrmion should move to the right, and slightly upward. Determine the speed of the skyrmion and the drift angle. Try varying alpha. For alpha = beta there should be no up or down drift. For alpha < beta the drift should be downward. For that condition flip the initial state using Oxs_AffineOrientVectorField and Oxs_AffineTransformVectorField so the skyrmion can drift without running into the edge of the simulation. If the simulation goes unstable for small alpha try adding “method rkf54s” to the Anv_SpinTEvolve Specify block.

Extra Credit:

Reduce the saturation magnetization Ms in the simulation to 200 kA/m, and enable dipole-dipole interactions by including an Oxs_Demag object. Solve for remanent equilibrium as in Session 2 homework, with increased pinning if necessary. Then run STT current simulations as above.

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