First-principles study of exchange interactions and Curie temperatures of half-metallic ferrimagnetic full Heusler alloys Mn2VZ (Z=Al, Ge)

TL;DR

This study uses density functional theory to analyze exchange interactions and predict Curie temperatures in half-metallic ferrimagnetic Mn2VZ (Z=Al, Ge) Heusler alloys, providing insights into their magnetic properties.

Contribution

First-principles calculations of exchange interactions and Curie temperatures in Mn2VZ alloys, including predictions for Mn2VGe where experimental data is lacking.

Findings

Mn2VAl's Curie temperature matches experimental data.

Mn2VGe's Curie temperature is predicted without experimental confirmation.

Competing magnetic interactions influence the overall magnetic behavior.

Abstract

We report the parameter-free, density functional theory calculations of interatomic exchange interactions and Curie temperatures of half-metallic ferrimagnetic full Heusler alloys Mn2VZ (Z=Al, Ge). To calculate the interatomic exchange interactions we employ the frozen-magnon approach. The Curie temperatures are calculated within the mean-field approximation to the classical Heisenberg Hamiltonian by solving a matrix equation for a multi-sublattice system. Our calculations show that, although a large magnetic moment is carried by Mn atoms, competing ferromagnetic (inter sublattice) and antiferromagnetic (intra sublattice) Mn-Mn interactions in Mn2VAl almost cancel each other in the mean-field experienced by the Mn atoms. In Mn2VGe the leading Mn-Mn exchange interaction is antiferromagnetic. In both compounds the ferromagnetism of the Mn subsystem is favored by strong antiferromagnetic Mn-V interactions. The obtained value of the Curie temperature of Mn2VAl is in good agrement with experiment. For Mn2VGe there is no experimental information available and our calculation is a prediction.