Pressure-induced structural, electronic, and magnetic evolution in cubic inverse spinel NiFe2O4, an ab-initio study

NiFe2O4 (NFO) is a soft magnetic material that is vital for various spintronic, biomedical, and energy-related applications. In this report, cubic inverse spinel NFO was investigated for its electronic structure, magnetic, and optical properties, and variations of these properties as a function of external hydrostatic pressure were determined in the framework of the Density Functional Theory using the CASTEP code. The NFO is a semiconducting ferrimagnetic material in the absence of externally applied hydrostatic pressure, however, this electronic and magnetic character changes steadily as the applied pressure is increased from 0 to 100 GPa. The bandgap value, lattice constant, and the net magnetic moment all decrease with increasing pressure. The electronic bandgap of NFO becomes zero and it becomes paramagnetic at the highest studied pressure of 100 GPa. The electronic structure was studied in detail with varying pressure, and it was indicated that the density of states Fe3+ at the octahedral sublattice showed a large splitting of 3d states with increasing pressure. This large decrease in the net magnetic moment can be attributed to the above-mentioned energy splitting. All optical constants were also observed to be affected by the external pressure. The conversion of O2− states from discrete/split to continuous may be the possible reason for the variation of optical properties.