Pair anisotropy in disordered magnetic systems

TL;DR

This paper introduces pair-induced uniaxial anisotropy in disordered magnetic systems, showing how neighboring atoms influence magnetic anisotropy and improving model accuracy for dilute magnetic semiconductors.

Contribution

It presents the concept of pair anisotropy and demonstrates its importance in accurately modeling magnetism in disordered materials.

Findings

Including pair anisotropy improves agreement between simulations and experiments.

Pair anisotropy significantly affects magnetic behavior in dilute magnetic semiconductors.

Density functional theory calculations reveal the influence of neighboring atoms on anisotropy.

Abstract

Accurate modelling of magnetism is pivotal for elucidating the microscopic origins of magnetic phenomena in functional materials. However, for a specified class of materials, such as random dilute ferromagnets or alloys, the reliance on simplifying assumptions, such as single-ion anisotropy, limits the accuracy of existing spin models. In such systems, there is a significant probability of the formation of nearest-neighbor magnetic ion pairs or higher order clusters, whose presence breaks the local symmetry of otherwise isolated magnetic species. Here, we introduce the concept of pair-induced uniaxial anisotropy and demonstrate how nearby atoms influence each other's anisotropic behavior. This effect is investigated in the dilute magnetic semiconductor Ga$_{1-x}$Mn$_x$N, by means of density functional theory calculations. The inclusion of pair anisotropy in the atomistic spin simulations significantly improves the agreement between simulated and experimental magnetization curves, in contrast to models that consider only single-ion anisotropy.