First principles study of Mo, W doped CrBr3 alloy compounds

Two-dimensional ferromagnetic semiconductors are considered to be the cornerstone of the next generation of electronic devices, but their application in practical devices is limited by their low Curie temperature (TC). A monolayer of chromium tribromide (CrBr3) as a member of two-dimensional ferromagnetic material chromium trihalide CrX3 (X = I, Br, Cl) has found widespread applications in the latest years. Equivalent alloying of ferromagnetic materials is an effective way to increase TC. In this paper, the transition metals Mo and W were chosen to replace Cr atoms in monolayer CrBr3 to construct alloy compounds Cr8_xTMxBr24 (TM = Mo/W, x = 1-4) and the electronic structures as well as magnetic properties were investigated via first principles calcula-tions. Alloy compounds all maintain their original semiconductor properties, with Cr8_xMoxBr24 (x = 2-4) and Cr5W3Br24 transformed into direct bandgap semiconductors compared to intrinsic CrBr3. Additionally, the ferromagnetic (FM) coupling of alloy compounds is further enhanced. The strongest FM coupling is found in Cr6W2Br24, which is enhanced by 3 times. The magnetic anisotropic energy (MAE) values of alloy compounds are significantly higher. MAE value of Cr4W4Br24 is up to 2357 mu eV/Cr which is 11 times larger than a value without doping (202 mu eV/Cr). TC of alloy compounds all increase, with Cr4W4Br24 having a maximum TC of 100.3 K, which is 3 times larger than a value without doping (31 K). The findings increase the range of two-dimensional ferromagnetic semiconductors and offer a theoretical basis for the investigation of the spintronic devices based on CrBr3.