Effect of Biaxial Strain on Cation Octahedral Rotations and Magnetic Structure of the Antiperovskite Mn₃GaN

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.