Half-metallicity and anomalous Slater-Pauling behaviour in half-Heusler CrMnSb

TL;DR

This paper reveals that CrMnSb, an 18-electron half-Heusler compound, exhibits a half-metallic, compensated ferrimagnetic ground state instead of the expected nonmagnetic semiconducting behavior, due to localized sublattice moments.

Contribution

It provides first-principles evidence explaining the anomalous magnetic behavior of CrMnSb, challenging conventional Slater-Pauling expectations for 18-electron systems.

Findings

CrMnSb is half-metallic with a compensated ferrimagnetic ground state.

Localized sublattice moments cause the deviation from expected behavior.

CrMnSb's magnetic properties are due to antiparallel alignment of Cr and Mn moments.

Abstract

This study provides a first-principles insight into half-Heusler CrMnSb to understand its deviation from the conventional Slater-Pauling semiconducting behavior. CrMnSb, having a valence electron count of 18, has been proposed to exhibit compensated ferrimagnetic character instead of the expected nonmagnetic semiconducting ground state. As half-Heusler systems with a valence electron count of 18 are not known to exhibit magnetic ordering, we have investigated the electronic and magnetic properties of CrMnSb using a combination of density functional theory and Green's function-based multiple-scattering theory. We show that, despite satisfying the 18 valence electron Slater-Pauling rule, CrMnSb does not exhibit ground-state nonmagnetic semiconducting behavior. Instead, it reveals a half-metallic, fully compensated ferrimagnetic ground state. This anomaly originates from the presence of localized sublattice moments, resulting from antiparallel alignment between Cr and Mn sublattices, which enforces half-metallic ferrimagnetism despite its ideal 18 valence electron count.