I am trying to simulate domain wall motion in nanowires. In [1] with the below mentioned parameters, the authors have simulated domain wall oscillation in a constricted nanowire. The constricted nano wire is designed by offsetting a portion of the nano-wire in transverse direction by 15 nm. I am trying to reproduce their result in mumax3. I have attached the image of the regions.

The material parameters are- saturation magnetization = 600e03 A/m^3 magnetic anisotropy energy = 1e05 J/m^3 exchange stiffness = 1.3e-11 J/m current density = 8.65e11 A/m^2 spin polarization of the applied current = 0.6 damping constant = 0.014 Polarized electric current is flowing along positive x-direction

MUMAX 3.9.1 Code

// The exchange length lex = {Aex/ (0.5*mu0*Msat^2)}^0.5

// In this model lex = 7.58 nm approx

// We are considering cell dimension 2nm X 2nm X 3nm

// Define gridsize & cellsize

Nx := 128

Ny := 64

Nz := 1

sizeX := 256e-9

sizeY := 128e-9

sizeZ := 3e-9

SetGridSize(Nx, Ny, Nz)

SetCellSize(sizeX/Nx, sizeY/Ny, sizeZ/Nz)

//Define geometry

struc1 := cuboid(100e-09,40e-09,3e-09).transl(-40e-09,0,0)

struc2 := cuboid(100e-09,40e-09,3e-09).transl(40e-09,-15e-09,0)

struc := struc1.add(struc2)

setgeom(struc)

//Define regions

defregion(1,struc)

save(regions)

//Define Material parameter

Msat.setregion(1,600e3) // Saturation Magnetization in A/m

Ku1.setregion(1,1e05) // 1st order uniaxial anisotropy constant in J/m^3

Aex.setregion(1,1.3e-11) // Exchange stiffness in J/m^3

alpha.setregion(1,0.014) // Landau-Lifshitz damping constant

//Define Initial Reduced Magnetization

m.setregion(1,twodomain(1,0,0, 1,1,0, -1,0,0))

//Save data and vector field

runtime := 1e-09

autosave(m.region(1),runtime/10)

tableautosave(runtime/10)

//Initialize excitation

J.setregion(1,vector(8.65e11,0,0)) // Current density vector in A/m^2

Pol.setregion(1,0.6) // Electrical current polarization

run(runtime)

I will be really thankful if you could help in this matter.

[1] Sbiaa, R., and M. Al Bahri. "Constricted nanowire with stabilized magnetic domain wall." Journal of Magnetism and Magnetic Materials 411 (2016): 113-115