Electronic Structure, Optical, and Magnetic Properties of Mn_100−xGe_x (x = 20, 25, and 30) Alloys Near Tetragonal–Orthorhombic Structural Phase Transition

Abstract

Electronic, structural, optical, and magnetic properties of the Mn100−xGex alloys for x = 20, 25, and 30 are investigated near a tetragonal–orthorhombic structural phase transition. In the electronic structure calculations, the ferrimagnetic ground state is found which is in excellent agreement with the experimental observation of magnetic properties. The calculations reveal that the main contribution to the optical absorption is associated with the electronic transitions in the system of 3d manganese bands, these states significantly change near the Fermi energy. The optical conductivity of the alloys is also transformed with an increase of the low‐energy absorption values near structural phase transition due to the enhanced electronic transitions. Among different compositions of the studied Mn–Ge, the highest magnetization is observed for Mn70Ge30 whereas highest coercivity is observed for the Mn75Ge25 alloy. High coercivity can be ascribed to the highest magneto‐crystalline anisotropy of the sample whereas high magnetization of Mn70Ge30 can be due to the presence of a hexagonal ferromagnetic phase with higher magnetization. The effect of Mn–Ge composition on the structural phase transition and its relationship with the electronic structure, optical, and magnetic properties may allow for better designing of new Heusler alloys for various customized applications.