Magnetic topological insulators provide an important platform for realizing several exotic quantum phenomena, such as the axion insulating state and the quantum anomalous Hall effect, owing to the interplay between topology and magnetism. MnBi₄Te₇ is a two-dimensional Z₂ antiferromagnetic (AFM) topological insulator with a Néel temperature of ∼13 K. In AFM materials, the topological Hall effect (THE) is observed owing to the existence of nontrivial spin structures. A material with noncollinearity that develops in the AFM phase rather than at the onset of the AFM order is particularly important. In this study, we observed that such an unanticipated THE starts to develop in a MnBi₄Te₇ single crystal when the magnetic field is rotated away from the easy axis (c-axis) of the system. Furthermore, the THE resistivity reaches a giant value of ∼7 μΩ-cm at 2 K when the angle between the magnetic field and the c-axis is 75°. This value is significantly higher than the values for previously reported systems with noncoplanar structures. The THE can be ascribed to the noncoplanar spin structure resulting from the canted state during the spin-flip transition in the ground AFM state of MnBi₄Te₇. The large THE at a relatively low applied field makes the MnBi₄Te₇ system a potential candidate for spintronic applications.

中文翻译：

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二维反铁磁拓扑绝缘体MnBi4Te7非共线相中的巨型拓扑霍尔效应

由于拓扑和磁性之间的相互作用，磁性拓扑绝缘体为实现几种奇异的量子现象提供了重要的平台，例如轴子绝缘态和量子反常霍尔效应。MnBi ₄ Te ₇是二维Z ₂反铁磁(AFM) 拓扑绝缘体，奈尔温度约为13 K。在AFM 材料中，拓扑霍尔效应(THE) 由于存在非平凡的自旋结构而被观察到。在 AFM 阶段而不是在 AFM 阶次开始时形成的具有非共线性的材料尤其重要。在这项研究中，我们观察到这种意想不到的 THE 开始在 MnBi ₄ Te ₇当磁场旋转远离系统的易轴（c轴）时，单晶。此外，当磁场与c轴之间的角度为 75°时，THE 电阻率在 2 K 时达到了 ∼7 μΩ-cm 的巨值。该值明显高于先前报告的具有非共面结构的系统的值。THE 可以归因于在 MnBi ₄ Te _{7 的}AFM 基态中的自旋-翻转跃迁期间由倾斜状态产生的非共面自旋结构。在相对低的外加场下的大 THE 使 MnBi ₄ Te ₇系统成为自旋电子应用的潜在候选者。