二维层状磁性半导体材料FePSe₃的物理性质研究

Study on Physical Properties of Two-Dimensional Layered Magnetic Semiconductor Material FePSe₃

摘要: 本文采用化学气相输运(CVT)法生长了大尺寸高质量的过渡金属–磷–三硒化物FePSe₃的单晶样品，通过扫描电镜–能谱系统(SEM-EDX)、X射线衍射仪(XRD)、综合物性测量系统(PPMS)和磁性测量系统(MPMS)研究了该单晶样品的化学成分、晶体结构、电输运性质和磁各向异性。单晶和粉末X射线衍射表明FePSe₃是具有三角晶体结构的典型层状材料。面内电阻率随温度变化曲线表明FePSe₃是半导体材料，激活能约为268 meV。磁化率随温度变化曲线表明FePSe₃在109 K发生具有明显一级相变特征的反铁磁相变；反铁磁相变温度之上面内磁化率和面间磁化率都表现居里–外斯顺磁行为，但外斯温度符号相反，表现出明显的各向异性。

Abstract: The transition metal phosphorus trisulfides FePSe₃ was successfully grown by chemical vapor transport (CVT) method. The chemical composition, crystal structure, electrical transport properties, and magnetic anisotropy have been studied by scanning electron microscope-energy dispersion spectrum (SEM-EDX), X-ray diffractometer (XRD), physical property measurement system (PPMS), and magnetic property measurement system (MPMS). Single crystal and powder X-ray diffraction pattern confirms that FePSe₃ belongs to the trigonal crystal structure, and has the features of van der Waals layer structure. The in-plane resistivity increases with decreasing temperature and exhibits semiconductor behavior with an activation energy of 268 meV. In high temperature, the in-plane and out-of-plane magnetic susceptibility increase with decreasing temperature and exhibit Curie-Weiss paramagnetic behavior, but the Weiss temperatures of both directions have a different sign which indicates that the magnetic properties of FePSe₃ are anisotropic. With decreasing temperature, the magnetic susceptibility of both directions shows a sharp decrease at the temperature of 109 K and then almost keeps a constant, which is a typical antiferromagnetic transition, but further analysis suggests that the antiferromagnetic transition is a first-order phase transition.