Non-collinear Magnetic states of Mn5Ge3 compound

TL;DR

This study uses ab-initio calculations to explore the magnetic states of Mn5Ge3, revealing how pressure and strain influence the stability of collinear and non-collinear magnetic configurations, with implications for magnetic degeneracy and state transitions.

Contribution

It provides the first detailed theoretical analysis of the magnetic state stability of Mn5Ge3 under pressure and strain, highlighting the role of uniaxial strain in favoring non-collinear configurations.

Findings

Degenerate magnetic states under pressure.

Transition from ferromagnetic to non-collinear states with volume change.

Uniaxial tensile strain favors non-collinear magnetic configurations.

Abstract

Mn5Ge3 thin films epitaxially grown on Ge(111) exhibit metallic conductivity and strong ferromagnetism up to about 300 K. Recent experiments suggest a non-collinear spin structure. In order to gain deep insights into the magnetic structure of this compound, we have performed fully unconstrained ab-initio pseudopotential calculations within density functional theory, investigating the different magnetic states corresponding to Collinear (C) and Non-Collinear (NC) spin configurations. We focus on their relative stability under pressure and strain field. Under pressure, the C and NC configurations are degenerate, suggesting the possible occurrence of accidental magnetic degeneracy also in Mn5Ge3 real samples. We found a continuous transition from a ferromagnetic C low-spin state at small volumes to a NC high-spin state at higher volumes. Remarkably, the degeneracy is definitely removed under the effect of uniaxial strain: in particular, NC spin configurations is favoured under tensile uniaxial strain.