元素替代对准二维铁磁半导体Cr2Ge2Te6磁学性质的调控研究

准二维铁磁半导体在具有铁磁性质和半导体性质的同时还具有低维属性，是制备纳米自旋电子器件的理想材料。以Cr2Ge2Te6为代表的层状材料表现出本征铁磁性的特征，但其铁磁转变温度均远低于室温，这大大限制了其在自旋电子学领域的应用。本项目以准二维铁磁半导体Cr2Ge2Te6为研究对象，采用元素替代的手段，不仅引入化学压力改变原子间距调控直接磁交换作用，还可以减小发生超交换作用的轨道间的能量差，增强Cr2Ge2Te6中的铁磁超交换作用，双向增强Cr2Ge2Te6的磁性，提高其铁磁转变温度。通过系统开展不同元素掺杂对其磁学性质的调控研究，并利用变温拉曼光谱方法来研究材料的晶格畸变与其宏观磁性的关联，总结元素掺杂对其磁性的调控规律，为探索合成高相变温度的准二维磁性半导体材料提供参考，也为相关自旋电子学器件应用研究奠定材料基础。

Quasi-two-dimensional (2D) ferromagnetic (FM) semiconductors, integrating semiconductivity, ferromagnetism, and low dimensionality, serve as the cornerstone for high-speed nano-spintronic devices. The typical layered materials, such as Cr2Ge2Te6, present the intrinsic FM behavior. However, the FM phase transition temperature (TC) is much lower than room temperature, which limits the applications in spintronic field. In this project, we plan to enhance the TC of Cr2Ge2Te6 by the element substitution on the Cr and Ge sites. Firstly, the chemical pressure will be introduced by the element substitution on the Ge site to change the distance between the Cr atoms and then tune the magnetic properties. Secondly, the proper element substitution on Cr site will enhance the FM superexchange. To discover the relationship between the magnetism and the distortion of lattice which is introduced by element substation, the local lattice distortion will be studied by temperature- and pressure-dependent Raman scattering. Finally, the rule of manipulating the magnetism by element substitution will be summarized. The studies in the present project may stimulate researchers to make quasi-2D ferromagnetic semiconductors toward room temperature application.