Effect of Co Substitution on Ferrimagnetic Heusler compound Mn3Ga

TL;DR

This study uses first-principles calculations to explore how cobalt substitution affects the structural and magnetic properties of Mn3Ga, revealing phase preferences and magnetic behavior changes with Co concentration.

Contribution

It provides new insights into the phase stability and magnetic interactions in Co-doped Mn3Ga, highlighting the different magnetic moments and exchange interactions at varying Co levels.

Findings

Ferrimagnetism remains robust across Co concentrations.

Phase preference shifts from tetragonal to cubic at x=0.5.

Co magnetic moment behavior explains changes in total magnetization.

Abstract

Effect of Co substitution on Mn$_3$Ga is investigated using first-principles study for structural and magnetic properties. Without Co, ferrimagnetic Heusler compound Mn3Ga is in tetragonal phase. With Co substitution, depending on Co concentration (x) Mn$_3$Ga prefers tetragonal (cubic) phase when x \leq 0.5 (x \geq 0.5). Ferrimagnetism is robust regardless of x in both phases. While magnetic moments of two Mn do not vary significantly with x, Co magnetic moment in two phases exhibit different behaviors, leading to distinct features in total magnetic moment (M_{tot}). When x \leq 0.5, in tetragonal phase, Co magnetic moment is vanishingly small, resulting in a decrease of M_{tot} with x. In contrast, when x \geq 0.5, in cubic phase, Co magnetic moment is roughly 1$\mu_B$, which is responsible for an increase of Mtot. Electronic structure is analyzed with partial density of states for various x. To elucidate the counterintuitively small Co moment, the magnetic exchange interaction is investigated where exchange coefficient between Co and Mn is much smaller in x \leq 0.5 case than x \geq 0.5 one.