Surface-Driven Evolution of the Anomalous Hall Effect in Magnetic Topological Insulator MnBi2Te4 Thin Films

TL;DR

This study demonstrates that surface oxidation significantly influences the magnetic and electronic properties of MnBi2Te4 thin films, including reversing the anomalous Hall effect, which is crucial for future spintronic and quantum applications.

Contribution

It reveals how surface oxidation modifies magnetic and electronic responses in MnBi2Te4, highlighting the importance of surface engineering for topological and magnetic properties.

Findings

Surface oxidation affects the top 1-2 unit cells of MnBi2Te4.

Reversal of the anomalous Hall effect sign observed.

Surface stoichiometry critically influences magnetic and electronic behavior.

Abstract

Understanding the effects of interfacial modification to the functional properties of magnetic topological insulator thin films is crucial for developing novel technological applications from spintronics to quantum computing. Here, we report that a large electronic and magnetic response is induced in the intrinsic magnetic topological insulator MnBi2Te4 by controlling the propagation of surface oxidation. We show that the formation of the surface oxide layer is confined to the top 1-2 unit cells but drives large changes in the overall magnetic response. Specifically, we observe a dramatic reversal of the sign of the anomalous Hall effect driven by finite thickness magnetism, which indicates that the film splits into distinct magnetic layers each with a unique electronic signature. These data reveal a delicate dependence of the overall magnetic and electronic response of MnBi2Te4 on the stoichiometry of the top layers. Our study suggests that perturbations resulting from surface oxidation may play a non-trivial role in the stabilization of the quantum anomalous Hall effect in this system and that understanding targeted modifications to the surface may open new routes for engineering novel topological and magnetic responses in this fascinating material.