derivative of magnetization vector

[Chris289-star]

How do users define the field related to the derivative of magnetization vector m? For example, exchange interaction field and DMI field?

[jplauzie]

Hi,

In general, this sort of question would be better suited to the mailing list, here. However, you can also find an example of this in the custom quantities section of the API. There is also an example with exchange listed here.

Best,
Josh L.

[Chris289-star]

Hi,
Thank you very much for Josh L.'s answer. However, I have looked at the relevant APIs and did not find any examples of m differentiating space or time. I have seen an example with exchange, where the second derivative of m with respect to space can be achieved through Shifted m. However, how to implement the derivative of m with respect to time? Is there a general form of differentiation for m?