Exchange bias in van der Waals MnBi$_2$Te$_4$/Cr$_2$Ge$_2$Te$_6$ heterostructure

TL;DR

This study demonstrates electrically tunable exchange bias in a van der Waals heterostructure of MnBi$_2$Te$_4$ and Cr$_2$Ge$_2$Te$_6$, potentially facilitating high-temperature quantum anomalous Hall effects.

Contribution

It reports the first observation of electrically tunable exchange bias in MnBi$_2$Te$_4$/Cr$_2$Ge$_2$Te$_6$ heterostructures, highlighting a new platform for topological quantum phenomena.

Findings

Exchange bias appears over a critical magnetic field.

Maximum exchange bias occurs near the magnetic band gap.

Exchange bias affects the antiferromagnetic MnBi$_2$Te$_4$ layer.

Abstract

The layered van der Waals (vdW) material MnBi$_2$Te$_4$ is an intrinsic magnetic topological insulator with various topological phases such as quantum anomalous Hall effect (QAHE) and axion states. However, both the zero-field and high-temperature QAHE are not easy to realize. It is theoretically proposed that the exchange bias can be introduced in the MnBi2Te4/ferromagnetic (FM) insulator heterostructures and thus opens the surface states gap, making it easier to realize the zero-field or high-temperature QAHE. Here we report the electrically tunable exchange bias in the van der Waals MnBi$_2$Te$_4$/Cr$_2$Ge$_2$Te$_6$ heterostructure. The exchange bias emerges over a critical magnetic field and reaches the maximum value near the magnetic band gap. Moreover, the exchange bias was experienced by the antiferromagnetic (AFM) MnBi$_2$Te$_4$ layer rather than the FM layer. Such van der Waals heterostructure provides a promising platform to study the novel exchange bias effect and explore the possible high-temperature QAHE.