I have a very important question about the spin package. To clarify my problem, I am attaching a pdf file. I hope you will help me to progress in my research work as well. Thankful
SPIN PACKAGE.pdf (496 KB)
Hello Majid,
My apologies for the late answer, I discovered your question yesterday.
I do not have a lot of information about your simulation settings, so that I will have to make a couple of guesses. I assume your only magnetic pair interactions is an exchange (pair spin/exchange), and your initial spin configuration has all spins aligned.
If so, I believe you’re facing a very common issue of spin-lattice calculations. If your spins start all aligned in the same direction, the exchange interaction is not sufficient to transfer angular momentum from the lattice to the spins, and your spins will not start moving.
This manuscript by Perera et al. discussed thoroughly this issue and proposed some corrections:
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.060402
In practice, to solve your issue, you may either start your calculation with some spin disorder (for example randomizing some spins in your system), or you can add an interaction accounting that will account for the spin-orbit coupling. This interaction will account for angular momentum transfer between your lattice and spin systems, and will prevent this problem.
The Neel pair interaction can be used to perform such coupling. To understand how to parametrize a Neel interaction, you may want to have a look at some of the following papers:
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.094437
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.024429
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.86.174409
Your parametrization of the Neel model can be used to recover appropriate spin-lattice relaxation rates, or simulate other materials properties such as the magnetocrystalline anisotropy or the magneto-elastic coefficients in your material. In both cases, it should solve your problem.
Hope this helps!
Best,
Julien.