A Computational Study of Nickel Ferrite

Magnetic properties and electronic structure of nickel ferrite are studied using hybrid density functional theory. In the calculation, the exchange correlation is a mixture of Fock exchange, local spin density approximation (LSDA) and generalized gradient approximation (GGA). The weighting factor (w) of the Fock term and a scaling factor of the 3d orbitals of Fe (a) are introduced as fitting parameters. All nearest neighbor exchange constants for inter and intra A and B sites of the spinel structure of nickel ferrite are calculated from the energies of different magnetic structures. Local magnetic moments of the ions on the A and B sites are calculated by the Mülliken population analysis. Moreover, the density of states is calculated to show the insulating nature of nickel ferrite. The band gap and intrasite Coulomb repulsion are extracted from the calculated density of states. The charge density map is calculated to visualize the electrons in nickel ferrite. r 2006 Elsevier B.V. All rights reserved. PACS: 75.30.Et; 75.50.Gg; 71.20.Ps; 71.15.Mb