Effect of Biaxial Strain on Cation Octahedral Rotations and Magnetic Structure of the Antiperovskite Mn$_{3}$GaN

TL;DR

This study uses density functional theory to investigate how biaxial strain affects the magnetic structure and electron distribution in Mn₃GaN, revealing strain-induced magnetic transitions and charge redistribution mechanisms.

Contribution

It provides new insights into strain effects on Mn₃GaN's magnetic and electronic properties, highlighting differences from oxide perovskites in strain response mechanisms.

Findings

Tensile strain induces spin canting and net magnetization.

Compressive strain collapses non-collinear order, leading to ferrimagnetism.

Strain affects bond lengths and charge distribution, not octahedral tilts.

Abstract

Density functional theory is used to study the effect of compressive and tensile biaxial strain on Mn$_{3}$GaN. Mn$_{3}$GaN is a non-collinear antiferromagnetic antiperovskite with a similar structure to that of an ideal cubic oxide perovskite, but with cations at the octahedral sites while the anion, nitrogen, is found at the B site. The present study explores the response of Mn$_{3}$GaN to (001) strain, considering biaxial strain levels ranging from -5% to 5%. It is found that the electron structure is insensitive to tensile strain. The study supports previous results in that a spin-canted antiferromagnetic order emerges due to tensile strain, inducing net magnetization. Compressive strain collapses the non-collinear antiferromagnetic spin structure and induces a ferrimagnetic order at -2% strain. Notably, in contrast with oxide perovskites, Mn$_{3}$GaN does not respond to strain by octahedral tilt, but rather by intraband redistributions of charge between Mn $d$ states. Despite the similar structure to oxide perovskites, the bonds between the B site anion and octahedral site cations in Mn$_{3}$GaN bonds are less rigid, such that strain is instead accommodated by a change in bond length rather than a change in bond angles.