Wang Fei, Zhao Yi-Fan, Yan Zi-Jie, Zhuo Deyi, Yi Hemian, Yuan Wei, Zhou Lingjie, Zhao Weiwei, Chan Moses H W, Chang Cui-Zu
Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
School of Material Science and Engineering, Harbin Institute of Technology, Shenzhen 518055, China.
Nano Lett. 2023 Apr 12;23(7):2483-2489. doi: 10.1021/acs.nanolett.2c03827. Epub 2023 Mar 17.
To date, the quantum anomalous Hall effect has been realized in chromium (Cr)- and/or vanadium(V)-doped topological insulator (Bi,Sb)Te thin films. In this work, we use molecular beam epitaxy to synthesize both V- and Cr-doped BiTe thin films with controlled dopant concentration. By performing magneto-transport measurements, we find that both systems show an unusual yet similar ferromagnetic response with respect to magnetic dopant concentration; specifically the Curie temperature does not increase monotonically but shows a local maximum at a critical dopant concentration. We attribute this unusual ferromagnetic response observed in Cr/V-doped BiTe thin films to the dopant-concentration-induced magnetic exchange interaction, which displays evolution from van Vleck-type ferromagnetism in a nontrivial magnetic topological insulator to Ruderman-Kittel-Kasuya-Yosida (RKKY)-type ferromagnetism in a trivial diluted magnetic semiconductor. Our work provides insights into the ferromagnetic properties of magnetically doped topological insulator thin films and facilitates the pursuit of high-temperature quantum anomalous Hall effect.
迄今为止，量子反常霍尔效应已在铬（Cr）和/或钒（V）掺杂的拓扑绝缘体（Bi，Sb）Te薄膜中实现。在这项工作中，我们使用分子束外延法来合成具有可控掺杂剂浓度的V掺杂和Cr掺杂的BiTe薄膜。通过进行磁输运测量，我们发现这两个体系对于磁性掺杂剂浓度均表现出异常但相似的铁磁响应；具体而言，居里温度并非单调增加，而是在临界掺杂剂浓度处出现局部最大值。我们将在Cr/V掺杂的BiTe薄膜中观察到的这种异常铁磁响应归因于掺杂剂浓度诱导的磁交换相互作用，这种相互作用呈现出从非平凡磁拓扑绝缘体中的范弗莱克型铁磁性到平凡稀磁半导体中的鲁德曼 - 基特尔 - 卡苏亚 - 约西达（RKKY）型铁磁性的演变。我们的工作为磁性掺杂拓扑绝缘体薄膜的铁磁特性提供了见解，并有助于追求高温量子反常霍尔效应。
