Are the boundary conditions modified for custom effective fields?

[J A. Fernandez-Roldan]

Dear colleagues,

I am implementing some custom DMI interaction (custom energy and custom field).

I wonder if the micromagnetic boundary conditions at surfaces are modified by the program when custom fields and energy terms are included?

Thanks for any help you can provide.

[Felipe Garcia]

Dear Jose Angel,

As far as I know, the boundary conditions are considered inside the DMI/exchange calculations, but I don't see any modification for custom fields. If you add a custom DMI, or any field that contains derivatives, you will have to modify the boundary. Regarding this, they will for PBC conditions but I am almost sure that for normal boundaries it will not work

Best regards,

Felipe

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[José A. Fdez.]

Dear Felipe, 

thank you very much for your explanation. I expected so. I will try to find a way to modify them or look for some alternative.

Best regards,

José Ángel 

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[Josh Lauzier]

As Felipe mentioned, I don't see anything within the custom fields code that modifies boundary conditions.

Probably what you can do is copy the existing DMI .go and .cu files (i think mostly it is the cuda you need to tweak), and then tweak the pieces you need. For the most part it should be nearly identical, and there is some explanation of things in the file comments (DMI.cu in particular has comments on the boundary conditions used/implemented). The boundary terms are only ~6 lines or so (repeated for each dimension), so like 36 lines of code total. Of course, you'll have to recompile after making those edits.

There are also some existing test mx3 files to test things like the DMI energy, so if your custom version can be simplified to normal DMI (say, in a special case), those might be useful as sanity checks once you get the modifications working.

Cheers,

Josh L.

[Felipe Garcia]

Dear Jose Angel and Josh,

One subtle fact to be considered is that one has to derive the proper boundary conditions for the Included DMI field. Actually, one has to derive the conditions from the DMI energy.

Best regards,

Felipe

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