Polar magneto-optical Kerr effect in antiferromagnetic M$_2$As (M=Cr, Mn, Fe) under an external magnetic field

TL;DR

This study combines first-principles simulations and experiments to analyze the polar magneto-optical Kerr effect in antiferromagnetic M$_2$As compounds under magnetic fields, revealing how magnetic symmetry breaking influences optical responses.

Contribution

It introduces a computational scheme to calculate magnetic susceptibility from total-energy changes and links magneto-optical effects to symmetry breaking in antiferromagnetic materials.

Findings

Magneto-optical Kerr rotation and ellipticity depend on magnetic symmetry breaking.

Tilting magnetic moments affects exchange interactions but not spin-orbit coupling.

The work highlights the role of magnetic susceptibility in magneto-optical responses.

Abstract

Antiferromagnetic metals attract tremendous interest for memory applications due to their expected fast response dynamics in the terahertz frequency regime. Reading from and writing information into these materials is not easily achievable using magnetic fields, due to weak high-order magneto-optical signals and robustness of the magnetic structure against external magnetic fields. Polarized electromagnetic radiation is a promising alternative for probing their response, however, when ideal antiferromagnetic symmetry is present, this response vanishes. Hence, in this work we combine first-principles simulations with measurements of the polar magneto-optical Kerr effect under external magnetic fields, to study magneto-optical response of antiferromagnetic M$_2$As (M=Cr, Mn, and Fe). We devise a computational scheme to compute the magnetic susceptibility from total-energy changes using constraints on magnetic-moment tilting. Our predictions of the spectral dependence of polar magneto-optical Kerr rotation and ellipticity allow us to attribute these effects to breaking of the magnetic symmetry. We show that tilting affects the exchange interaction, while the spin-orbit interaction remains unaffected as the tilting angle changes. Our work provides understanding of the polar magneto-optical Kerr effect on a band structure level and underscores the importance of the magnetic susceptibility when searching for materials with large magneto-optical response.