First-principles study of the structural stability of Mn3Z (Z=Ga, Sn and Ge) Heusler compounds

TL;DR

This study uses first-principles calculations to analyze the structural stability and magnetic properties of Mn3Z (Z=Ga, Sn, Ge) Heusler compounds across different phases, aligning well with experimental data.

Contribution

It reveals the role of the cubic phase as an intermediate in phase transitions and explains differing behaviors among Mn3Z compounds based on phase energy comparisons.

Findings

Cubic phase acts as an intermediate in phase transitions.

Mn3Ga and Mn3Ge differ from Mn3Sn in phase energy hierarchy.

Calculated magnetic properties match experimental observations.

Abstract

We investigate the structural stability and magnetic properties of cubic, tetragonal and hexagonal phases of Mn3Z (Z=Ga, Sn and Ge) Heusler compounds using first-principles density-functional theory. We propose that the cubic phase plays an important role as an intermediate state in the phase transition from the hexagonal to the tetragonal phases. Consequently, Mn3Ga and Mn3Ge behave differently from Mn3Sn, because the relative energies of the cubic and hexagonal phases are different. This result agrees with experimental observations from these three compounds. The weak ferromagnetism of the hexagonal phase and the perpendicular magnetocrystalline anisotropy of the tetragonal phase obtained in our calculations are also consistent with experiment.