Tuning the magnetic properties of half-metallic semi-Heusler alloys by sp-electron substitution: The case of AuMnSn$_{1-x}$Sb$_x$ quaternary alloys

TL;DR

This study investigates how substituting sp-electrons in AuMnSn$_{1-x}$Sb$_x$ Heusler alloys influences their magnetic phases, revealing a transition from ferromagnetic to antiferromagnetic states with increased Sb content, consistent with experimental data.

Contribution

First principles calculations of magnetic phase transitions in AuMnSn$_{1-x}$Sb$_x$ alloys, demonstrating the effect of sp-electron substitution on magnetic properties and phase diagram.

Findings

Phase transition from ferromagnetic to antiferromagnetic with increasing Sb.

Antiferromagnetic superexchange dominates at high Sb concentrations.

Correlation effects do not change the phase diagram.

Abstract

We study the electronic and magnetic properties of the quaternary AuMnSn$_{1-x}$Sb$_{x}$ Heusler alloys using first principles calculations. We determine their magnetic phase diagram and we show that they present a phase transition from a ferromagnetic to an antiferromagnetic state with increasing Sb concentration. For large Sb concentrations the antiferromagnetic superexchange coupling dominates over the ferromagnetic RKKY-like exchange mechanism. This behavior is similar to the one demonstrated by the isovalent Ni$_{1-x}$Cu$_x$MnSb alloy studied recently by the authors [I. Galanakis et al, Phys. Rev. B. \textbf{77}, 214417 (2008)]. Thus the variation of the concentration of the \textit{sp}-electrons (Sn and Sb atoms) and the variation of the concentration of the non-magnetic \textit{3d} atoms (Cu) lead to a similar tuning of the the magnetic properties of the Heusler alloys. We show that the inclusion of correlation effects does not alter the phase diagram. Calculated results are in good agreement with the available experimental data.