Correlation between magnetic domain structures and quantum anomalous Hall effect in epitaxial MnBi2Te4 thin films

TL;DR

This study uses magnetic force microscopy to link magnetic domain uniformity with the quantum anomalous Hall effect in MnBi2Te4 thin films, revealing that uniform magnetization is crucial for quantization.

Contribution

It demonstrates a direct correlation between magnetic domain size and the quantum anomalous Hall effect in epitaxial MnBi2Te4 films, highlighting the importance of magnetic uniformity.

Findings

More uniform magnetization correlates with the presence of QAH.

Magnetic domain size influences Hall resistivity quantization.

Sample inhomogeneity causes magnetic domain pinning and nonuniformity.

Abstract

We use magnetic force microscopy (MFM) to study spatial uniformity of magnetization of epitaxially grown MnBi2Te4 thin films. Compared to films which exhibit no quantum anomalous Hall effect (QAH), films with QAH are observed to have more spatial uniformity of magnetization with larger domain size. The domain evolution upon magnetic field sweeping indicates that the magnetic domains or the spatial nonuniformity of magnetization originates from the strong pinning of the inherent sample inhomogeneity. A direct correlation between the Hall resistivity and the domain size has been established by analyzing a series of thin films with and without QAH. Our observation shows that one has to suppress the spatial nonuniformity of magnetization to allow the Hall resistivity to be quantized. The fact that a sizable longitudinal resistivity remains even for the QAH sample suggests a quantized Hall insulator scenario. Our work provides important insights to the understanding of the quantization mechanism and the dissipation of the QAH state in MnBi2Te4 system.