Anisotropic Magnetoresistance Effect

As consequence of the Anisotropic Magnetoresistance Effect we compute the Resistance of a layer of Permalloy by using the effect that the resistance changes with the direction of the magnetic field.

To have success with this script you have to download the following Image by right-click and save in the same folder like your script

Shape The shape with cathodes (red, green) and Permalloy (black)

Code

from magnum import *

mesh = RectangularMesh((200, 100, 1), (4e-9, 4e-9, 10e-9))

#Building the mesh from the image
isc = ImageShapeCreator("amr_shape.png", mesh)

world  = World(
  mesh,
  Body("left"  , Material.Au(), isc.pick("red")),
  Body("square", Material.Py(), isc.pick("black")),
  Body("right" , Material.Au(), isc.pick("green"))
)

solver = create_solver(world, [StrayField, ExchangeField, CurrentPath], 
                       log=True)

solver.state.U_contact = 2 # volts
solver.state.M = vortex.magnetizationFunction(400e-9, 200e-9, 1)

writeOMF("M_initial.omf", solver.state.M)
writeVTK("M_initial.vtk", solver.state.M)

# I. Print resistance (resulting from Ohmic and AMR resistance).
print "Total resistance:", solver.state.R_contact, "Ohm"

# II. Calculate spatially resolved current density. 
# This needs either U_contact or I_contact specified.
writeOMF("vortex-j.omf", solver.state.j)
writeVTK("vortex-j.vtk", solver.state.j)

Results

As consequence of the vortex we have a inhomogeneous current density. The total resistance is 28.83 Ohm

Vortex The z-Component of magnetization in the permalloy

Stromdichte The inhomogeneous current density in the permalloy