Magneto-optic Kerr effect in a spin-polarized zero-moment ferrimagnet

TL;DR

This paper demonstrates that the magneto-optical Kerr effect can occur in a fully compensated ferrimagnet with zero net magnetization, due to spin-polarized conduction bands, challenging traditional assumptions.

Contribution

It reveals that MOKE can be observed in chemically similar, spin-polarized ferrimagnets with zero net moment, expanding understanding of magneto-optical phenomena.

Findings

MOKE observed in Mn2Ru_xGa despite zero net magnetization

Spectral analysis shows helicity-dependent reflectivity from a spin-polarized conduction band

The behavior is dominated by a manganese sublattice creating a broad Drude tail

Abstract

The magneto-optical Kerr effect (MOKE) is often assumed to be proportional to the magnetisation of a magnetically ordered metallic sample; in metallic ferrimagnets with chemically distinct sublattices, such as rare-earth transition-metal alloys, it depends on the difference between the sublattice contributions. Here we show that in a highly spin polarized, fully compensated ferrimagnet, where the sublattices are chemically similar, MOKE is observed even when the net moment is strictly zero. We analyse the spectral ellipsometry and MOKE of Mn 2 Ru x Ga, and show that this behaviour is due to a highly spin-polarized conduction band dominated by one of the two manganese sublattices which creates helicity-dependent reflectivity determined by a broad Drude tail. Our findings open new prospects for studying spin dynamics in the infra-red.