Intrinsic Even-Odd Thickness-Driven Anomalous Hall in Epitaxial MnBi2Te4 Thin Films

TL;DR

This study demonstrates how precise control of layer thickness and synthesis conditions in MnBi2Te4 thin films reveals an even-odd layer dependence of the anomalous Hall effect, advancing understanding of intrinsic magnetism in topological materials.

Contribution

It introduces a refined synthesis method for MnBi2Te4 films and uncovers the layer-dependent intrinsic anomalous Hall effect related to non-compensated ferromagnetism.

Findings

Odd-layer films show large hysteresis up to 25K.

Even-layer films exhibit minimal anomalous Hall response.

Sign reversal of the Hall effect indicates intrinsic versus defect-related magnetism.

Abstract

We demonstrate precise control of magnetism in MnBi2Te4 thin films through careful synthesis by molecular beam epitaxy, achieving minimal defects and accurate layer thickness control. By optimizing Mn-Bi-Te ratios and growth temperatures, we minimize detrimental self-doping effects and accurately target integer-layer films. X-ray diffraction and reflectivity provide quantitative measures of film quality and thickness. When these macroscale probes of structure and thickness are integrated with magnetotransport measurements, a striking even-odd layer dependence of the anomalous Hall effect is revealed. Odd-layer films exhibit a large hysteresis up to the N\'eel temperature (~25K), consistent with non-compensated antiferromagnetism, while even-layer films show minimal response, as expected for an antiferromagnet. The sign of the anomalous Hall effect exhibits a sign reversal for intrinsic magnetism versus magnetism associated with defects. This work identifies critical factors for inducing pure, non-compensated ferromagnetism and reveals the character of the intrinsic anomalous Hall effect in MnBi2Te4, which together is a step towards realizing the zero-field quantum anomalous Hall effect in topological materials.