The correlation of surface impurity states with the antiferromagnetic ground states is crucial for understanding the formation of the topological surface state in the antiferromagnetic topological insulators MnBi₂Te₄. By using low-temperature scanning tunneling microscopy and spectroscopy, we observed a localized bound state around the Mn-Bi antisite defect at the Te-terminated surface of the antiferromagnetic topological insulator MnBi₂Te₄. When applying a magnetic field perpendicular to the surface (B_z) from −1.5 to 3.0 T, the bound state shifts linearly to a lower energy with increasing B_z, which is attributed to the Zeeman effect. Remarkably, when applying a large range of B_z from −8.0 to 8.0 T, the magnetic field induced reorientation of surface magnetic moments results in an abrupt jump in the local density of states (LDOS), which is characterized by LDOS-change-ratio \({\rm{d}}\tilde \sigma /{\rm{d}}B\) quantitatively. Interestingly, two asymmetric critical field, −2.0 and 4.0 T determined by the two peaks in \({\rm{d}}\tilde \sigma /{\rm{d}}B\) are observed, which is consistent with simulated results according to a Mills-model, describing a surface spin flop transition (SSF). Our results provide a new flatform for studying the interplay between magnetic order and topological phases in magnetic topological materials.

表面杂质态与反铁磁基态的相关性对于理解反铁磁拓扑绝缘体MnBi ₂ Te ₄中拓扑表面态的形成至关重要。通过使用低温扫描隧道显微镜和光谱学，我们在反铁磁拓扑绝缘体 MnBi ₂ Te ₄的 Te 端面处观察到 Mn-Bi 反位缺陷周围的局部束缚态。当施加从 -1.5 到 3.0 T 的垂直于表面 ( B _z )的磁场时，随着B _z的增加，束缚态线性转变为较低的能量，这归因于塞曼效应。值得注意的是，当施加从 -8.0 到 8.0 T 的大范围B _z时，磁场引起的表面磁矩重新定向导致局部状态密度 (LDOS) 的突然跳跃，其特征在于 LDOS 变化比\({\rm{d}}\tilde \sigma /{\rm{d}}B\)定量。有趣的是，观察到两个不对称临界场，-2.0 和 4.0 T，由\({\rm{d}}\tilde \sigma /{\rm{d}}B\)中的两个峰确定，这与模拟的一致根据 Mills 模型得出的结果，描述了表面自旋翻转跃迁 (SSF)。我们的结果为研究磁性拓扑材料中磁序和拓扑相之间的相互作用提供了一个新的平台。