The MnBi2Te4 material family has emerged as a key platform for exploring magnetic topological phases, most notably exemplified by the experimental realization of the axion insulator state. While spin dynamics are known to significantly influence the axion state, a profound understanding of their interplay remains elusive. In this work, we employ an antiferromagnetic spin-chain model to demonstrate that an external magnetic field induces extrinsic perpendicular magnetic anisotropy. We find that an in-plane field stabilizes the antiferromagnetic order, whereas an out-of-plane field destabilizes it and triggers spin-flop transitions. Remarkably, near the surface spin-flop transition in even-layer MnBi2Te4 films, the axion insulator state undergoes a sharp switching behavior accompanied by distinct magnetoelectric responses. Furthermore, we propose that this switchable axionic magnetoelectric effect can be utilized to convert alternating magnetic field signals into measurable square-wave magneto-optical outputs, thereby realizing an axionic analog of a zero-crossing detector. Our findings could open a pathway toward potential applications of axion insulators in next-generation spintronic devices.
@article{arxiv.2510.16760,
title = {Switchable axionic magnetoelectric effect via spin-flop transition in topological antiferromagnets},
author = {Yiliang Fan and Rongxiang Zhu and Tongshuai Zhu and Jianzhou Zhao and Huaiqiang Wang and Haijun Zhang},
journal= {arXiv preprint arXiv:2510.16760},
year = {2025}
}