Anisotropic magnetism at the surface of a non-magnetic bulk insulator

TL;DR

This study investigates the magnetic properties of FeSb2's surface, revealing anisotropic magnetism and an anomalous Hall effect, which could influence surface transport in topological Kondo insulators.

Contribution

It provides the first detailed analysis of surface magnetic anisotropy and transport properties of FeSb2, linking surface magnetism to transport phenomena.

Findings

Surface magnetic susceptibility shows Curie-Weiss behavior.

Surface magnetization anisotropy matches magnetotransport anisotropy.

Evidence of an anomalous Hall effect at low temperatures.

Abstract

The potential for topological Kondo insulating behavior in d-electron systems has attracted interest in studying the surface states of the correlated insulators FeSb2 and FeSi. While detailed studies and theoretical description of a spin-orbit coupled ferromagnetic surface state have been applied to FeSi, the magnetic properties of the surface states of FeSb2 have not been addressed. Here, we report on the surface magnetic properties of FeSb2, utilizing the surface area dependence of magnetic susceptibility to separate the surface Curie-Weiss temperature dependence from the bulk spin-gap susceptibility. We use these results to further extract the surface magnetic anisotropy of a thin, rough-surfaced single-crystal FeSb2 to compare with the observed magnetotransport anisotropy, and find good agreement between the anisotropy in the surface magnetization and surface magnetotransport. We conclude with evidence of an anomalous Hall contribution to the low-temperature surface transport.