Ab initio comparative study of the magnetic, electronic and optical properties of AB2O4 (A, B= Mn, Fe) spinels

The comparison of the magnetic, electronic, and optical properties of the spinel transition-metal oxides AB 2 O 4 (A, B = Fe, Mn) and their relationship with the structure and composition were studied within DFT-GGA + U approximation. The spinels were considered both in the normal and inverse structure. We have found that regardless of composition and structure, the studied spinels are ferrimagnetic with antiparallel magnetic moments on A- and B-site cations. Electronic and structural properties of spinels depend on the composition: FeMn 2 O 4 has a tetragonal structure and half-metallic properties; however, in the inverse FeMn 2 O 4 , the bandgap opens for the spin-up channel. MnFe 2 O 4 is a cubic insulator with a bandgap of about 1.5 eV, which decreases in the inverse structure. The superexchange constants estimate within the simple indirect coupling model and have values close to the experimental ones. The total magnetization of FeMn 2 O 4 is drop-down to zero under hydrostatic pressure above 60 GPa due to the strong dependence of the magnetic moment of octahedral manganese ion on the pressure. The microscopic mechanisms of the relationship between the structure, composition and properties are studied. • The effect of the cation's site on the properties of the spinels is studied. • The electronic and structural properties of spinels depend on the composition. • The exchange constants of the spinels are estimated. • The abrupt decrease of the FeMn2O4 spinel total magnetization under pressure is predicted.