3d-electron induced magnetic phase transition in half-metallic semi-Heusler alloys

TL;DR

This study investigates how non-magnetic 3d atoms influence magnetic phase transitions in half-metallic semi-Heusler alloys, revealing a transition from ferromagnetic to antiferromagnetic states driven by Cu concentration.

Contribution

It provides a detailed first-principles analysis of magnetic phase diagrams in semi-Heusler alloys, highlighting the role of 3d atoms and Fermi level positioning in magnetic behavior.

Findings

Phase transition from ferromagnetic to antiferromagnetic with increasing Cu content

Dominance of RKKY-like exchange at low Cu concentrations

Superexchange coupling becomes significant at higher Cu levels

Abstract

We study the effect of the non-magnetic 3\textit{d} atoms on the magnetic properties of the half-metallic (HM) semi-Heusler alloys Co$_{1-x}$Cu$_{x}$MnSb and Ni$_{1-x}$Cu$_{x}$MnSb ($0 \leq x \leq 1$) using first-principles calculations. We determine the magnetic phase diagram of both systems at zero temperature and obtain a phase transition from a ferromagnetic to an antiferromagnetic state. For low Cu concentrations the ferromagnetic RKKY-like exchange mechanism is dominating, while the antiferromagnetic superexchange coupling becomes important for larger Cu content leading to the observed magnetic phase transition. A strong dependence of the magnetism in both systems on the position of the Fermi level within the HM gap is obtained. Obtained results are in good agreement with the available experimental data.