Spin-fluctuation mechanism of anomalous temperature dependence of magnetocrystalline anisotropy in itinerant magnets

TL;DR

This paper explains the unusual temperature dependence of magnetocrystalline anisotropy in (Fe$_{1-x}$Co$_{x}$)$_{2}$B alloys through first-principles calculations, revealing electronic mechanisms involving band shifts and spin fluctuations.

Contribution

It introduces a first-principles approach within the disordered local moment model to elucidate the anomalous temperature behavior of anisotropy in itinerant magnets, contrasting with existing models.

Findings

Excellent agreement with experimental data.

Anisotropy can increase as magnetization decreases.

Electronic mechanisms involve band shifts and suppression of spin-orbit hot spots.

Abstract

The origins of the anomalous temperature dependence of magnetocrystalline anisotropy in (Fe$_{1-x}$Co$_{x}$)$_{2}$B alloys are elucidated using first-principles calculations within the disordered local moment model. Excellent agreement with experimental data is obtained. The anomalies are associated with the changes in band occupations due to Stoner-like band shifts and with the selective suppression of spin-orbit "hot spots" by thermal spin fluctuations. Under certain conditions, the anisotropy can increase, rather than decrease, with decreasing magnetization due to these peculiar electronic mechanisms, which contrast starkly with those assumed in existing models.