Electron Correlations and the Minority-Spin Band Gap in Half-Metallic Heusler Alloys

TL;DR

This paper investigates how electron-electron correlations influence the minority-spin band gap and spin depolarization in half-metallic Heusler alloys, using advanced first-principles methods to explore potential spintronic applications.

Contribution

It applies dynamical mean field theory to analyze correlation effects and proposes new alloy materials for spintronic devices.

Findings

Correlation effects introduce non-quasiparticle states above the Fermi level.

Depolarization depends on Coulomb interaction strength and temperature.

Ni$_{1-x}$Fe$_{x}$MnSb alloys are promising for spin-valve applications.

Abstract

Electron-electron correlations affect the band gap of half-metallic ferromagnets by introducing non-quasiparticle states just above the Fermi level. In contrast to the spin-orbit coupling, a large asymmetric non-quasiparticle spectral weight is present in the minority-spin channel, leading to a peculiar finite-temperature spin depolarization effects. Using recently developed first-principle dynamical mean field theory, we investigate these effects for the half-metallic ferrimagnetic Heusler compound FeMnSb. We discuss depolarization effects in terms of strength of local Coulomb interaction $U$ and temperature in FeMnSb. We propose Ni$_{1-x}$Fe$_{x}$MnSb alloys as a perspective materials to be used in spin-valve structures and for experimental search of non-quasiparticle states in half-metallic materials.