Anomalous Kerr Effect in SrRuO$_3$ Thin Films

TL;DR

This study reveals complex Kerr effect behavior in SrRuO$_3$ thin films, showing anomalous components linked to domain inhomogeneities, challenging previous skyrmion-based interpretations of Hall and Kerr anomalies.

Contribution

It introduces a theory connecting Kerr effect anomalies to magnetic domain inhomogeneities, not skyrmions, in SrRuO$_3$ thin films.

Findings

Kerr rotation exhibits two-component behavior under certain conditions.

Anomalous Kerr component correlates with Hall resistivity anomalies.

Inhomogeneous domain formation explains the observed effects.

Abstract

We study the magneto-optical Kerr effect (MOKE) in SrRuO$_3$ thin films, uncovering wide regimes of wavelength, temperature, and magnetic field where the Kerr rotation is not simply proportional to the magnetization but instead displays two-component behavior. One component of the MOKE signal tracks the average magnetization, while the second "anomalous" component bears a resemblance to anomalies in the Hall resistivity which have been previously reported in skyrmion materials. We present a theory showing that the MOKE anomalies arise from the non-monotonic relation between the Kerr angle and the magnetization, when we average over magnetic domains which proliferate near the coercive field. Our results suggest that inhomogeneous domain formation, rather than skyrmions, may provide a common origin for the observed MOKE and Hall resistivity anomalies.