Large topological Hall effect in an easy-cone ferromagnet (Cr0.9B0.1)Te

TL;DR

This study reports a large topological Hall effect and a sign change in the anomalous Hall effect in (Cr0.9B0.1)Te single crystals, driven by a spin reorientation from easy-axis to easy-cone structure affecting Berry curvature.

Contribution

It demonstrates the influence of spin reorientation on Berry curvature and Hall effects in an easy-cone ferromagnet, providing insights into the relation between spin structure and topological phenomena.

Findings

Sign conversion of anomalous Hall effect observed.

Large topological Hall effect detected in the material.

Spin reorientation affects Berry curvature and Hall responses.

Abstract

The Berry phase understanding of electronic properties has attracted special interest in condensed matter physics, leading to phenomena such as the anomalous Hall effect and the topological Hall effect. A non-vanishing Berry phase, induced in momentum space by the band structure or in real space by a non-coplanar spin structure, is the origin of both effects. Here, we report a sign conversion of the anomalous Hall effect and a large topological Hall effect in (Cr0.9B0.1)Te single crystals. The spin reorientation from an easy-axis structure at high temperature to an easy-cone structure below 140 K leads to conversion of the Berry curvature, which influences both, anomalous and topological, Hall effects in the presence of an applied magnetic field and current. We compare and summarize the topological Hall effect in four categories with different mechanisms and have a discussion into the possible artificial fake effect of topological Hall effect in polycrystalline samples, which provides a deep understanding of the relation between spin structure and Hall properties.