Magnetic Phase Transitions and the Origin of Anomalous Hall Effect on MnBi₂Te₄ Grown by MBE

Intrinsic magnetic topological insulators have been extensively studied due to the theoretical prediction that it will provide a platform for novel topological phases, such as the quantum anomalous Hall effect (QAHE), the axion insulators (AIs), and the type-II magnetic Weyl semimetals depending on thickness. Recently, the QAHE and AI have been observed on MnBi₂Te₄ flakes with odd and even number of layers, respectively. However, further progress on this novel material is hindered by the difficulty in preparing its high-quality thin films with well-controlled compositions and thickness. Here we report on the magnetic properties of MnBi₂Te₄ grown by MBE with various thicknesses. We observed two main results: magnetic phase transitions and the linear dependence between the Hall conductance and the magnetization. Both transport and SQUID measurements clearly show the magnetic phase transitions between a FM to an AFM state and vice versa, which brings the possibility of hosting new topological phases on MBE grown samples. In addition, we verify the origin of the AHE of MnBi₂Te₄ is intrinsic, from its linear dependence of magnetization. Our results enable the realization of QAHE in the large area MnBi₂Te₄ films with thickness precisely controlled by MBE.