Electronic structure and magnetic ordering of NiN and Ni2N from first principles

Abstract

The results of first-principles electronic structure calculations for the nitrogen-rich nickel nitrides and are presented. The calculations are based on density functional theory and used the generalized gradient approximation (GGA) as well as the GGA+U approach. The latter turned out to be crucial for a correct description of the crystal phase stability and magnetic instabilities of both compounds. While for GGA calculations predict a non-magnetic ground state with the zincblende structure, GGA+U calculations result in a half-metallic ferromagnet with the rocksalt structure in line with indications from the neighboring transition-metal nitrides making a possible candidate for spin-filter devices. For GGA calculations likewise lead to a non-magnetic behavior, which is contrasted with a ferrimagnetic ordering obtained from the GGA+U approach. This ground state results from complex three-dimensional exchange interaction via -type and -type overlap of the Ni 3d orbitals with the N 2p orbitals and may explain the reported sensitivity of the magnetic ordering to details of the crystal structure. For both nitrides, experimental data are called for to confirm our predictions.