Interface-driven topological Hall effect in SrRuO$_3$-SrIrO$_3$ bilayer

TL;DR

This study demonstrates the emergence of a topological Hall effect in SrRuO$_3$-SrIrO$_3$ bilayers, driven by interface Dzyaloshinskii-Moriya interaction, which can be tuned by layer thickness and has implications for topological electronics.

Contribution

It reveals the interface-driven topological Hall effect in oxide bilayers and links it to Dzyaloshinskii-Moriya interaction and skyrmion formation, advancing understanding of topological phenomena in oxide interfaces.

Findings

Topological Hall effect observed in SrRuO$_3$-SrIrO$_3$ bilayers.

Effect diminishes with SrRuO$_3$ thickness, disappearing at 7 unit cells.

Interface Dzyaloshinskii-Moriya interaction induces Nel-type skyrmions.

Abstract

Electron transport coupled with magnetism has attracted attention over the years as exemplified in anomalous Hall effect due to a Berry phase in momentum space. Another type of unconventional Hall effect -- topological Hall effect, originating from the real-space Berry phase, has recently become of great importance in the context of magnetic skyrmions. We have observed topological Hall effect in bilayers consisting of ferromagnetic SrRuO$_3$ and paramagnetic SrIrO$_3$ over a wide region of both temperature and magnetic field. The topological term rapidly decreases with the thickness of SrRuO$_3$, ending up with the complete disappearance at 7 unit cells of SrRuO$_3$. Combined with model calculation, we concluded that the topological Hall effect is driven by interface Dzyaloshinskii-Moriya interaction, which is caused by both the broken inversion symmetry and the strong spin-orbit coupling of SrIrO$_3$. Such interaction is expected to realize the N\'{e}el-type magnetic skyrmion, of which size is estimated to be $\sim$10 nm from the magnitude of topological Hall resistivity. The results established that the high-quality oxide interface enables us to tune the chirality of the system; this can be a step towards the future topological electronics.