Half-metallic ferromagnetism in binary compounds of alkali metals with nitrogen: Ab initio calculations

TL;DR

This study uses ab initio calculations to predict that certain hypothetical alkali metal nitrides are half-metallic ferromagnets with robust magnetic properties across various crystal structures.

Contribution

It is the first to theoretically demonstrate half-metallic ferromagnetism in alkali metal nitrides across multiple crystal structures using first-principles calculations.

Findings

All compounds are half-metallic ferromagnets with up to 2.0 eV bandgap.

Magnetic moment is exactly 2.00 μ_B per formula unit.

Half-metallicity remains stable under lattice contraction.

Abstract

The first-principles full-potential linearized augmented plane-wave method based on density functional theory is used to investigate electronic structure and magnetic properties of hypothetical binary compounds of I$^{A}$ subgroup elements with nitrogen (LiN, NaN, KN and RbN) in assumed three types of cristalline structure (rock salt, wurtzite and zinc-blende). We find that, due to the spin polarized \textit{p} orbitas of N, all four compounds are half-metallic ferromagnets with wide energy bandgaps (up to 2.0 eV). The calculated total magnetic moment in all investigated compounds for all three types of crystal structure is exactly 2.00 $\mu_{\text{B}}$ per formula unit. The predicted half-metallicity is robust with respect to lattice-constant contraction. In all the cases ferromagnetic phase is energetically favored with respect to the paramagnetic one. The mechanism leading to half-metallic ferromagnetism and synthesis possibilities are discussed.