Optical read-out of the N\'eel vector in metallic antiferromagnet Mn$_{2}$Au

TL;DR

This study demonstrates that near-infrared optical reflectivity anisotropy and magnetic linear dichroism in Mn₂Au can be used for ultrafast optical read-out of its Néel vector, advancing antiferromagnetic spintronics.

Contribution

It reports the observation of significant magnetic linear dichroism in Mn₂Au, enabling optical detection of the Néel vector orientation, which was previously limited to electrical and X-ray methods.

Findings

Reflectivity anisotropy of ~0.6% in near-infrared for Mn₂Au.

Magnetic linear dichroism is about four times larger than anisotropic magnetoresistance.

Dichroism arises from spin-orbit interactions affecting interband optical transitions.

Abstract

Metallic antiferromagnets with broken inversion symmetry on the two sublattices, strong spin-orbit coupling and high N\'{e}el temperatures offer new opportunities for applications in spintronics. Especially Mn$_{2}$Au, with high N\'{e}el temperature and conductivity, is particularly interesting for real-world applications. Here, manipulation of the orientation of the staggered magnetization,\textit{\ i.e.} the N\'{e}el vector, by current pulses has been recently demonstrated, with the read-out limited to studies of anisotropic magnetoresistance or X-ray magnetic linear dichroism. Here, we report on the in-plane reflectivity anisotropy of Mn$_{2}$Au (001) films, which were N\'{e}el vector aligned in pulsed magnetic fields. In the near-infrared, the anisotropy is $\approx$ 0.6\%, with higher reflectivity for the light polarized along the N\'{e}el vector. The observed magnetic linear dichroism is about four times larger than the anisotropic magnetoresistance. This suggests the dichroism in Mn$_{2}$Au is a result of the strong spin-orbit interactions giving rise to anisotropy of interband optical transitions, in-line with recent studies of electronic band-structure. The considerable magnetic linear dichroism in the near-infrared could be used for ultrafast optical read-out of the N\'{e}el vector in Mn$_{2}$Au.