FM/AFM coupling

[RIYA MEHTA]

Hello,

I am trying to create a FM/AFM layer in the Mumax+.

I understand that the FM layer can be designed using the class magnet as magnet = Ferromagnet(world, Grid((-,-,-))).

In the same way, the antiferromagnetic layer can be designed using the class magnet as antiferromagnet.

I am wondering how to couple the ferromagnetic and the antiferromagnetic layers. 

magnet.inter_exchange.set_between(region1, region2, value), magnet.inter_exchange = value and set_between(i,j,value) works between regions of same class. For FM/AFM, the two classes are different; is there any other way to do so? Could anyone please assist with this, it would be very helpful.

Regards,

[RIYA MEHTA]

May anyone please assist with this

[Lars Moreels]

Hello

The easiest way to achieve this, is to create one single AFM instance and set the saturation magnetization of one sublattice to zero in some layers (either by using a numpy array, or by defining regions). This way, the different existing exchange interactions can be used to exchange-couple the layers. For example (by using regions):

    grid = Grid((128, 128, 2))
    # Split the grid into 2 regions, with the lower region (index 0) being the AFM and the top region (index 1) being the FM
    regions = np.zeros(grid.shape)
    regions[1, :, :] = 1

    magnet = Antiferromagnet(World(cellsize=(1e-9, 1e-9, 1e-9)), grid, regions=regions)
    magnet.msat = 800e3 # both layers
    magnet.sub1.msat.set_in_region(1, 400e3) # msat of FM
    magnet.sub2.msat.set_in_region(1, 0) # unset msat of second sublattice in FM layer

    # Intercell FM coupling (inhomogeneous)
    # This couples both layers
    magnet.sub1.inter_exchange = 5e-12

Hope this helps!

For your interest, we recently opened Githbub Discussions for questions related specifically to mumax+. This way we can provide you with an answer more quickly since the whole mumax+ team gets notified when something is posted there.

Warm regards

Lars