Standard Problem 5 (sim_with)

Micromagnetic Standard Problem 5 involves simulating the dynamics of a magnetic vortex in a thin rectangular film under the influence of a spin-polarized current. The problem is designed to test the accuracy of micromagnetic simulations in capturing the complex behavior of vortex structures, including their motion and deformation. The rectangular film in this example has dimensions of 100 nm × 100 nm × 10 nm, and the simulation tracks the position of the vortex core as it evolves over time due to the combined effects of exchange interactions, demagnetization, and spin-transfer torques.

using MicroMagnetic
using Printf
using CairoMakie

@using_gpu()

Define a function to initialize a vortex roughly.

function init_fun(i, j, k, dx, dy, dz)
    x = i - 10
    y = j - 10
    r = sqrt(x^2 + y^2)
    if r < 2
        return (0, 0, 1)
    end
    return (y / r, -x / r, 0)
end

init_fun (generic function with 1 method)

Define simulation parameters.

args = (name="std5", task_s=["relax", "dynamics"],          # List of tasks to perform
        driver_s=["SD", "LLG_STT"],            # List of drivers to use
        mesh=FDMesh(; nx=20, ny=20, nz=2, dx=5e-9, dy=5e-9, dz=5e-9), # Mesh configuration
        Ms=8e5,                               # Saturation magnetization
        A=1.3e-11,                            # Exchange constant
        demag=true,                           # Enable demagnetization
        m0=init_fun,                          # Initial magnetization function
        alpha=0.1,                            # Gilbert damping parameter
        ux=-72.438,                           # Effective current density
        beta=0.05,                            # Nonadiabatic STT parameter
        steps=160,                            # Number of steps for dynamics
        dt=0.05ns,                            # Time step size
        stopping_dmdt=0.01,                   # Stopping criterion for relaxation
        saver_item=SaverItem(("Rx", "Ry"), ("<m>", "<m>"), compute_guiding_center),    #vortex center tracking
        dynamic_m_interval=1);

Run the simulation using sim_with function.

sim_with(args);

[ Info: MicroSim has been created.
[ Info: Exchange has been added.
[ Info: Running Driver : MicroMagnetic.EnergyMinimization{Float64}.
[ Info: max_dmdt is less than stopping_dmdt=0.01 @steps=174, Done!
[ Info: The driver LLG_STT is used!
................................................................................................................................................................
[ Info: step =  160  t = 8.000000e-09

Generate a movie for the vortex dynamics.

jld2movie("std5.jld2"; output="assets/std5.mp4", component='z', figsize=(400, 400))

"assets/std5.mp4"

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