M–H and M–V characteristics of STT MTJ

[Anuj Kumar]

Hi All, I am currently learning MuMax and would like to start with a simple STT-MTJ switching example. My goal is to obtain the M–H and M–V characteristics of the MTJ. Could you please let me know if this code is correct?

// Geometry
SetGridsize(64,64,1)
SetCellsize(2e-9,2e-9,1.5e-9)

// Material parameters
Msat  = 1.1e6
Aex   = 15e-12
alpha = 0.02
Ku1   = 5e5 // PMA

// STT parameters
Pol = 0.6
SlonczewskiPolarizer = vector(0,0,1)

// M–H loop
tableadd(B_ext)   // store applied field
tableadd(mz)      // store mz

Hmin := -0.5 // Tesla
Hmax :=  0.5 // Tesla
nsteps := 50

for i:=0; i<nsteps; i++ {
    H := Hmin + (Hmax-Hmin)*float64(i)/float64(nsteps-1)
    B_ext = vector(0,0,H)
    m = uniform(0,0,1)   // reset to +z before each field step
    relax()
    tablesave()
}

// 2) Magnetization vs STT Current 
jmin := 1e10   // A/m^2
jmax := 1e12   // A/m^2
nstepsJ := 20
pulseDuration := 100e-9

for i:=0; i<nstepsJ; i++ {
    m = uniform(0,0,1)   // reset to +z before each run
    B_ext = vector(0,0,0) // no external field
   
    j = jmin + (jmax-jmin)*float64(i)/float64(nstepsJ-1)
    run(pulseDuration)   // apply pulse
    tablesave()
}

save(m)