Controllable thickness inhomogeneity and Berry-curvature-engineering of anomalous Hall effect in SrRuO3 ultrathin films

TL;DR

This study demonstrates how controlled thickness inhomogeneity in SrRuO3 ultrathin films can engineer Berry curvature and induce a two-channel anomalous Hall effect, providing insights into topological properties and distinguishing it from skyrmion-induced effects.

Contribution

It introduces a method to control film thickness in SrRuO3 to engineer Berry curvature and AHE, clarifying the origin of Hall anomalies in these films.

Findings

Engineered inhomogeneous SrRuO3 films exhibit a two-channel AHE.

Identified microscopic features distinguishing AHE from topological Hall effect.

Achieved continuous control of AHE via sub-unit-cell thickness adjustments.

Abstract

In quantum matters hosting electron-electron correlation and spin-orbit coupling, spatial inhomogeneities, arising from competing ground states, can be essential for determining and understanding topological properties. A prominent example is Hall anomalies observed in SrRuO3 films, which were interpreted in terms of either magnetic skyrmion-induced topological Hall effect (THE) or inhomogeneous anomalous Hall effect (AHE). To clarify this ambiguity, we systematically investigated the AHE of SrRuO3 ultrathin films with controllable inhomogeneities in film thickness (tSRO). By harnessing the step-flow growth of SrRuO3 films, we induced microscopically-ordered stripes with one-unit-cell differences in tSRO. The resultant spatial distribution of momentum-space Berry curvatures enables a two-channel AHE, which shows hump-like anomalies similar to the THE and can be continuously engineered via sub-unit-cell control of tSRO. In these inhomogeneous SRO films, we microscopically identified a two-step magnetic switching and stripe-like ferromagnetic domains. These features are fingerprints for distinguishing the two-channel AHE from the skyrmion-induced THE.