Thermal collapse of spin-polarization in half-metallic ferromagnets

TL;DR

This paper investigates how thermal spin fluctuations cause a rapid loss of spin-polarization in half-metallic ferromagnets at temperatures below the Curie point, revealing a new mechanism affecting their magnetic properties.

Contribution

It introduces a novel mechanism where thermal fluctuations lead to abrupt polarization collapse, supported by ab-initio calculations and a mapped Heisenberg model.

Findings

Spin-polarization drops abruptly due to thermal fluctuations

The mechanism is verified for NiMnSb

Thermal properties modeled with Monte Carlo simulations

Abstract

The temperature dependence of the magnetization and spin-polarization at the Fermi level is investigated for half-metallic ferromagnets. We reveal a new mechanism, where the hybridization of states forming the half-metallic gap depends on thermal spin fluctuations and the polarization can drop abruptly at temperatures much lower than the Curie point. We verify this for NiMnSb by ab-initio calculations. The thermal properties are studied by mapping ab-initio results to an extended Heisenberg model which includes longitudinal fluctuations and is solved by a Monte Carlo method.