Electronic structure and magnetic ordering of NiN and Ni$_2$N from first principles

TL;DR

This study uses first-principles calculations to explore the electronic structure and magnetic properties of NiN and Ni₂N, revealing the importance of the GGA+U approach for accurate predictions and suggesting potential applications in spintronics.

Contribution

It demonstrates that GGA+U calculations are essential for correctly predicting the magnetic states and stability of NiN and Ni₂N, providing new insights into their electronic and magnetic behaviors.

Findings

NiN is predicted to be a half-metallic ferromagnet with rocksalt structure using GGA+U.

Ni₂N exhibits ferrimagnetic ordering under GGA+U, contrasting with non-magnetic GGA results.

Experimental data are needed to validate the theoretical predictions.

Abstract

The results of first-principles electronic structure calculations for the nitrogen-rich nickel nitrides $ {\rm NiN} $ and $ {\rm Ni_2N} $ 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 $ {\rm NiN} $ 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 $ {\rm NiN} $ a possible candidate for spin-filter devices. For $ {\rm Ni_2N} $ 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 $ \sigma $-type and $ \pi $-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.