Temperature dependence of spin-model parameters in antiferromagnets

TL;DR

This paper derives how key spin-model parameters in antiferromagnets change with temperature using Green's function theory, showing agreement with simulations and potential for multiscale modeling.

Contribution

It provides a theoretical framework for temperature-dependent spin-model parameters in antiferromagnets, extending previous ferromagnet results.

Findings

Transversal spin correlations reduce anisotropy terms.

Exchange interactions increase with temperature due to spin correlations.

Results align with atomistic simulations and ferromagnet data.

Abstract

The temperature dependence of mesoscopic spin-model parameters is derived in two-sublattice antiferromagnetically aligned systems based on Green's function theory. It is found that transversal spin correlations decrease the anisotropy terms while increasing the Heisenberg and Dzyaloshinsky--Moriya exchange interactions and the latter's contribution to the anisotropy. The obtained temperature dependences show quantitative agreement with the results for ferromagnets, and they also agree well with numerical atomistic simulations which treat the spin correlations without approximations. Possible applications of the results in multiscale modelling are discussed.