Even-Odd Layer-Dependent Anomalous Hall Effect in Topological Magnet MnBi2Te4 Thin Films

TL;DR

This study investigates the layer-dependent anomalous Hall effect in MnBi2Te4 thin films, revealing even-odd layer behavior linked to antiferromagnetism and phase contributions, advancing understanding of magnetic topological insulators.

Contribution

It demonstrates the layer-dependent anomalous Hall effect in MnBi2Te4 films grown by MBE, distinguishing contributions from different phases and revealing even-odd layer signatures.

Findings

Observation of non-square hysteresis loops in films >2 SL

Identification of two anomalous Hall components from different phases

Demonstration of even-odd layer-dependent behavior in MnBi2Te4

Abstract

A central theme in condensed matter physics is to create and understand the exotic states of matter by incorporating magnetism into topological materials. One prime example is the quantum anomalous Hall (QAH) state. Recently, MnBi2Te4 has been demonstrated to be an intrinsic magnetic topological insulator and the QAH effect was observed in exfoliated MnBi2Te4 flakes. Here, we used molecular beam epitaxy (MBE) to grow MnBi2Te4 films with thickness down to 1 septuple layer (SL) and performed thickness-dependent transport measurements. We observed a non-square hysteresis loop in the antiferromagnetic state for films with thickness greater than 2 SL. The hysteresis loop can be separated into two AH components. Through careful analysis, we demonstrated that one AH component with the larger coercive field is from the dominant MnBi2Te4 phase, while the other AH component with the smaller coercive field is from the minor Mn-doped Bi2Te3 phase in the samples. The extracted AH component of the MnBi2Te4 phase shows a clear even-odd layer-dependent behavior, a signature of antiferromagnetic thin films. Our studies reveal insights on how to optimize the MBE growth conditions to improve the quality of MnBi2Te4 films, in which the QAH and other exotic states are predicted.