Magnetic topological insulators exhibit unique electronic states due to the interplay between the electronic topology and the spin structure. The antiferromagnetic metal EuIn₂As₂ is a prominent candidate material in which exotic topological phases, including an axion insulating state, are theoretically predicted depending on the magnetic structure of the Eu²⁺ moments. Here, we report experimental results of the nuclear magnetic resonance (NMR) measurements of all the nuclei in EuIn₂As₂ to investigate the coupling between the magnetic moments in the Eu ions and the conduction electrons in In₂As₂ layers and the magnetic structure. The ⁷⁵As and ¹¹⁵In NMR spectra observed at zero external magnetic fields reveal the appearance of internal fields of 4.9 and 3.6 T, respectively, at the lowest temperature, suggesting a strong coupling between the conduction electrons in the In₂As₂ layer and the ordered magnetic moments in the Eu ions. The ⁷⁵As NMR spectra under in-plane external magnetic fields show broad distributions of the internal fields produced by an incommensurate fan-like spin structure which turns into a forced ferromagnetic state above 0.7 T. We propose a spin reorientation process that an incommensurate helical state at zero external magnetic field quickly changes into a fan state by applying a slight magnetic field.

由于电子拓扑和自旋结构之间的相互作用，磁拓扑绝缘体表现出独特的电子态。反铁磁金属EuIn ₂ As ₂是一种重要的候选材料，其中根据Eu ²⁺矩的磁结构从理论上预测了其中包括轴子绝缘态的奇异拓扑相。在这里，我们报告了 EuIn ₂ As ₂中所有原子核的核磁共振（NMR）测量的实验结果，以研究 Eu 离子中的磁矩与 In ₂ As ₂层中的传导电子之间的耦合以及磁性结构。在零外部磁场下观察到的⁷⁵ As 和¹¹⁵ In NMR 谱显示，在最低温度下分别出现了 4.9 T 和 3.6 T 的内部磁场，表明 In ₂ As ₂层中的传导电子与 In 2 As 2 层中的传导电子之间存在强耦合。 Eu 离子中的有序磁矩。面内外部磁场下的⁷⁵ As NMR 谱显示，由不相称的扇形自旋结构产生的内部场分布广泛，该结构在 0.7 T 以上转变成强制铁磁态。我们提出了一种自旋重定向过程，使不相称的螺旋状态在外部磁场为零时，通过施加轻微的磁场，快速转变为风扇状态。