"Switching" of Magnetic Anisotropy in a fcc Antiferromagnet with Direction-Dependent Interactions

TL;DR

This paper investigates how direction-dependent exchange interactions in a face-centered-cubic antiferromagnet induce magnetic anisotropy that switches between phases, driven by fluctuations, revealing a novel anisotropy switching phenomenon.

Contribution

It demonstrates that magnetic anisotropy in such systems is fluctuation-induced and differs between paramagnetic and ordered phases, highlighting a new anisotropy switching mechanism.

Findings

Anisotropy is induced by fluctuations in both phases.

Susceptibility peaks along 11 directions in the paramagnetic phase.

Magnetic moments align along 10 or 00 in the ordered phase.

Abstract

Direction-dependent anisotropic exchange is a common feature of magnetic systems with strong spin-orbit coupling. Here we study the effect of such exchange upon macroscopic magnetic anisotropy for a face-centered-cubic model. By several theoretical techniques, we show that, both in the paramagnetic and ordered phases, the magnetic anisotropy is induced by fluctuations. Moreover, the magnetic anisotropy differs in the paramagnetic and ordered phases: in the paramagnetic phase the susceptibility is maximum along the $\langle111\rangle$ directions, while the magnetic moments orient along $\langle110\rangle$ or $\langle100\rangle$ in the ordered phase. We suggest that such "anisotropy switching" can be a common feature of strongly spin-orbit coupled magnets.