Crystal and magnetic structures of magnetic topological insulators MnBi2Te4 and MnBi4Te7
Crystal and magnetic structures of magnetic topological insulators MnBi2Te4 and MnBi4Te7
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DOI：
10.1103/physrevb.101.020412
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发表时间：
2020-01-27
影响因子：
3.7
通讯作者：
Cao, Huibo
中科院分区：
文献类型：
--
作者：
Ding, Lei;Hu, Chaowei;Cao, Huibo
利用单晶中子衍射，我们对范德华拓扑绝缘体 MnBi2Te4 和 MnBi4Te7 的晶体结构和磁性进行了系统研究，最近预测和观察到了丰富的拓扑量子态。结构改进表明，两种材料的 Mn 位点上都占据了相当多的 Bi 原子，这与之前报道的反位无序不同。我们明确表明，MnBi(2)Te4 在 24 K 以下呈反铁磁性有序，具有磁对称性 R-I-3c，而 MnBi4Te7 在 13 K 以下呈反铁磁性，具有磁性空间群 P-c-3c1。它们都呈现出沿 c 轴自旋的反铁磁耦合铁磁层。我们提出了构建单元为[Bi2Te3]的无限自适应系列MnBi2nTe3n+1 (n >= 1)晶体结构的堆叠规则。通过比较 MnBi2Te4 和 MnBi4Te7 之间的磁性，结合最近的密度泛函理论计算，我们得出结论，在导数中可能实现二维磁极限。我们的工作可能会促进MnBi2nTe3n+1系列拓扑磁态的理论研究。
Using single-crystal neutron diffraction, we present a systematic investigation of the crystal structure and magnetism of the van der Waals topological insulators MnBi2Te4 and MnBi4Te7, where rich topological quantum states have been recently predicted and observed. Structural refinements reveal that considerable Bi atoms occupied on the Mn sites in both materials, distinct from the previously reported antisite disorder. We show unambiguously that MnBi(2)Te4 orders antiferromagnetically below 24 K, featured by a magnetic symmetry R-I-3c, while MnBi4Te7 is antiferromagnetic below 13 K with a magnetic space group P-c-3c1. They both present antiferromagnetically coupled ferromagnetic layers with spins along the c axis. We put forward a stacking rule for the crystal structure of an infinitely adaptive series MnBi2nTe3n+1 (n >= 1) with a building unit of [Bi2Te3]. By comparing the magnetic properties between MnBi2Te4 and MnBi4Te7, together with recent density-functional theory calculations, we concluded that a two-dimensional magnetism limit might be realized in the derivatives. Our work may promote theoretical studies of topological magnetic states in the series of MnBi2nTe3n+1.