Unveiling the impact of anti-site defects in magnetic transitions of few-layer MnBi2Te4 by operando heating

TL;DR

This study investigates how anti-site defects influence magnetic transitions in few-layer MnBi2Te4, revealing thermal effects and defect roles crucial for optimizing topological quantum phases in this magnetic topological insulator.

Contribution

It demonstrates the essential role of anti-site defects in magnetic states and shows how operando heating affects magnetic transitions, providing insights for engineering topological quantum phenomena.

Findings

Anti-site defects significantly affect magnetic states.

Thermal heating causes convergence of magnetic properties in different layers.

Heating-induced magnetic evolution serves as a quality assessment tool.

Abstract

As the first experimentally discovered intrinsic magnetic topological insulator, MnBi2Te4 has attracted widespread attentions, providing a unique platform for the exploration of topological quantum phases, such as quantum anomalous Hall effect and axion insulator state. Despite the increasing number of potential factors affecting samples being identified, obtaining the high-quality device performance with desired topological quantum phases remains a challenge. In this work, by comparing the reflective magnetic circular dichroism (RMCD) of crystals with different defect densities that are characterized by atomically resolved scanning tunneling microscopy, we demonstrate that anti-site defects play an essential role in achieving ideal magnetic states. By measuring RMCD hysteresis loops with operando heating, we find that MnBi2Te4 few-layer samples are highly susceptible to thermal impact, even at temperature as low as 45{\deg}C. The magnetic behavior of heating-treated samples is akin to that of samples fabricated into devices, revealing the thermal impact on devices as well. Starting from few-layers with ideal layer-dependent magnetic order, thermal heating leads to the convergence of magnetization and transition fields between odd- and even-layers. The observed heating-induced magnetic evolution can serve as a valuable reference for assessing the sample quality or the density of anti-site defects. Our findings not only point out the long-standing hidden factor that arose controversies in MnBi2Te4, but also pave the way for controllably engineering the topological quantum phenomena.