First-Principles Study on the Electronic, Magnetic, and Optical Properties of Ni_1-xMn_xFe₂O₄

This study employs first-principles calculations to investigate the atomic structure, electronic structure, magnetic properties, and optical properties of the spinel system Ni1-xMnxFe2O4 (x=0, 0.5, 1). Calculations are based on density functional theory. The optimized lattice parameters show good agreement with experimental values, which are further used for self-consistent calculations to obtain the above properties. Results show that NiFe2O4 (x=0) has the smallest lattice constant and magnetic moment. With the introduction of Mn2+, the unit cell volume expands systematically, and the total magnetic moment of the system increases significantly. Band structure analysis reveals that by applying Hubbard U corrections of 5.3 eV, 5 eV, and 4.3 eV to Mn, Ni, and Fe, respectively, the band gaps for x=0, 0.5, and 1 are 1.21 eV, 1.25 eV, and 1.66 eV, classifying these materials as ferrimagnetic semiconductors. Density of states analysis further elucidates the orbital hybridization mechanisms between Mn-O, Ni-O, and Fe-O bonds: as Mn content increases, the orbital hybridization between Mn-3d and O-2p strengthens, enhancing charge transfer, inducing asymmetric dipole polarization and consequently improving magnetism. Furthermore, the exploration of the optical properties provides a theoretical basis for the system's applications in optoelectronic devices and energy storage.