Towards the Quantized Anomalous Hall effect in AlOₓ-capped MnBi₂Te₄

The quantum anomalous Hall effect in layered antiferromagnet MnBi₂Te₄ harbors a rich interplay between magnetism and topology, holding a significant promise for low-power electronic devices and topological antiferromagnetic spintronics. In recent years, MnBi₂Te₄ has garnered considerable attention as the only known material to exhibit the antiferromagnetic quantum anomalous Hall effect. However, this field faces significant challenges as realizing quantized transport at zero magnetic fields depends critically on fabricating high-quality device. In this article, we address the detrimental influences of fabrication on MnBi₂Te₄ by simply depositing an AlOₓ thin layer on the surface prior to fabrications. Optical contrast and magnetotransport measurements on over 50 samples demonstrate that AlOₓ can effectively preserve the pristine state of the samples and significantly enhance the anomalous Hall effect towards quantization. Scaling analysis reveals the Berry curvature dominated mechanism of the anomalous Hall effect at various magnetic configurations. By adjusting the gate voltage, we uncover a gate independent antiferromagnetism in MnBi₂Te₄. Our experiment not only pave the way for fabricating high-quality transport devices but also advance the exploration of exotic quantum physics in 2D materials.