Exchange bias in the van der Waals heterostructure MnBi2Te4/Cr2Ge2Te6

Abstract

The exchange bias effect, namely the horizontal shift in the magnetic hysteretic loop, is known as a fundamentally and technologically important property of magnetic systems. Though the exchange bias effect has been widely observed in normal magnetic heterostructure, it is desirable to raise such pinning coupling in topology-based multilayer structure. Furthermore, the exchange bias effect was theoretically proposed to be able to further open the surface magnetization gap in the recently discovered intrinsic magnetic topological insulator $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$. Such an exchange interaction can be ensured and programmed in the heterojunction, or applied to spintronics. Here we report the electrically tunable exchange bias in the van der Waals $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}/{\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$ heterostructure. The exchange bias emerges over a critical magnetic field and reaches the maximum value near the band gap. Moreover, the exchange bias is experienced by net ferromagnetic (FM) odd-layers $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ rather than the pure FM insulator ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$. Accompanied by nonlocal signal, an unfamiliar antisymmetric peak endows a domain-related structure within interface of the heterostructure. Such van der Waals heterostructure provides a promising platform to study the novel exchange bias effect and explore the possible application of spintronics or $\mathrm{high}\ensuremath{-}{\mathrm{T}}_{\mathrm{c}}$ quantum anomalous Hall effect.