Implementation of Anisotropic DMI in Mumax3.

[Sudharsun Govindarajan]

Hello. I am a 2nd year MSc student currently working on the implementation of anistropic DMI in Mumax3. Mumax3 supports isotropic DMI, however to stabilize certain magnetic textures like antiskyrmions require anisotropic DMI. I found through this forum and mumax3 API that we could either use custom fields to provide anistropic DMI or modify the source code. I tried both but i was not successful. Now i seek help from the forum if they can point me in the right direction. Also i believed that anisotropic DMI via custom fields simply acts like an energy term in the total energy which would not make the spins to be twisted in neel like along one direction and bloch like on one direction (to stabilize an antiskyrmion) but i wish someone could clarify whether my understanding is right or not. Furthermore, kindly convey whether is it possible to provide anistropic DMI via custom fields.

[Josh Lauzier]

Hi,

It is indeed possible. If you can give some more details on how you tried to implement them, we can give some more specific suggestions? It is hard to give general suggestions without some further context on what you got stuck on.

When you implement custom fields, there should be both a torque/field term (via AddFieldTerm), and the energy density (via AddEdensTerm). Mumax mostly (with a few exceptions) works with the torques. When you implement a customfield you should be using both, not just the energy.

Separately, you may also be interested in mumaxplus. The implementation there is the full DMI tensor. I haven't tested it for this use case specifically, but I believe it allows setting all the tensor elements separately. It should allow for anisotropic DMI more easily, without having to fiddle with things like custom fields or the source code.

Best,
Josh L.