Improving the magnetic moment of Ca2Ge and promoting the conversion of semiconductors to diluted magnetic semiconductors using Mn-doping

Abstract

The dilute magnetic properties of materials have important potential applications in the field of electronic science and technology. Intrinsic Ca₂Ge is a new environmentally friendly semiconductor material, and exhibits cubic and orthorhombic phases. The crystal structure characteristics of Ca₂Ge indicate that the modulation of its dilute magnetic properties can theoretically be achieved by doping with magnetic elements. The study of band structures shows that Ca₂Ge is a semiconductor, while Mn doped Ca₂Ge is a semi-metal. The results of density of states and atomic population analysis show that Mn doped Ca₂Ge exhibits ferrimagnetism with a magnetic moment of 5 μ_B, and the orbital splitting energy of the Mn atom is 1.0 eV. Mn-doping changes the cubic crystal field of Ca₂Ge, and the charge transfer and electron polarization of Ca d and Ge p orbitals are affected by Mn atoms. The Ca d orbital is split into d_zz, d_zy, d_zx, d_xx–yy and d_xy orbitals, and the contribution of spin of each d split orbital to the magnetic moment of the Ca d orbital is in the order d_xy > d_yz > d_xz > d_xx–yy > d_zz. The Ge p orbital is split into p_x, p_y and p_z orbitals, and the spin contribution of each p orbital to the magnetic moment of the Ge p orbital is in the order p_y > p_z > p_x. The analysis of atom populations shows that the charge transfer and spin of Ca and Ge change with Mn doping, and the difference between spin up and spin down increases, improving the magnetism of Ca₂Ge and forming a dilute magnetic semiconductor.