Topological response of the anomalous Hall effect through the spin-flop transition of MnBi2Te4

Abstract

MnBi2Te4 is an intrinsic magnetic topological insulator where a naturally occurring band inversion and spontaneous magnetization cooperate to yield strong, often quantized, anomalous Hall effects. Quasi-three-dimensional compensated MnBi2Te4 is antiferromagnetic, but undergoes a spin-flop transition at intermediate fields, resulting in an unusual metastable canted phase before saturation. In this work, synthesis by molecular beam epitaxy allows us to obtain a large-area 24-layer antiferromagnetic MnBi2Te4 with near-perfect compensation that hosts the phase diagram of bulk MnBi2Te4 and a strong anomalous Hall effect (AHE). This AHE exhibits an antiferromagnetic response at low magnetic fields, and a clear evolution at intermediate fields through surface and bulk spin-flop transitions and into saturation. We also show that the anomalous Hall conductivity is super-linear versus magnetization, evidencing a non-collinear magnetic texture as magnetization evolves towards saturation. The strong impact of this non-collinear magnetic structure on the AHE measured here can be promising for the realization of electronic states predicted to occur in this magnetic regime of MnBi2Te4.