Half-metallicity in NiMnSb: a Variational Cluster Approach with ab-initio parameters

TL;DR

This study investigates electron correlation effects in NiMnSb using a combined density functional and many-body approach, revealing a significant reduction in spin polarization due to correlations.

Contribution

It introduces a variational cluster approach with ab-initio parameters to analyze correlation effects in half-metallic ferromagnets.

Findings

Spectral weight transfer towards the Fermi level in the majority spin channel.

States with vanishing quasiparticle weight in the minority spin gap.

Strong reduction of spin polarization due to correlations.

Abstract

Electron correlation effects in the half-metallic ferromagnet NiMnSb are investigated within a combined density functional and many-body approach. Starting from a realistic multi-orbital Hubbard-model including Mn and Ni-d orbitals, the many-body problem is addressed via the Variational Cluster Approach. The density of states obtained in the calculation shows a strong spectral weight transfer towards the Fermi level in the occupied conducting majority spin channel with respect to the uncorrelated case, as well as states with vanishing quasiparticle weight in the minority spin gap. Although the two features produce competing effects, the overall outcome is a strong reduction of the spin polarisation at the Fermi level with respect to the uncorrelated case. This result emphasizes the importance of correlation in this material.