Anti-site disorder and improved functionality of Mn$_{2}$Ni{\it X} ({\it X}= Al, Ga, In, Sn) inverse Heusler alloys

TL;DR

This study explores how chemical disorder in Mn2NiX alloys influences their phase stability and magnetic properties, revealing potential for enhanced functional effects like magneto-caloric responses due to anti-site disorder.

Contribution

It demonstrates that anti-site disorder in Mn2NiX alloys can induce martensitic transformations and improve magnetic functionalities, expanding understanding of disorder effects in inverse Heusler alloys.

Findings

Anti-site disorder induces martensitic transformations in most Mn2NiX alloys.

Disorder enhances inverse magneto-caloric effects.

Electronic structure analysis explains the origin of property improvements.

Abstract

Recent first-principles calculations have predicted Mn$_{2}$Ni{\it X} ({\it X}=Al, Ga, In, Sn) alloys to be magnetic shape memory alloys. Moreover, experiments on Mn$_{2}$NiGa and Mn$_{2}$NiSn suggest that the alloys deviate from the perfect inverse Heusler arrangement and that there is chemical disorder at the sublattices with tetrahedral symmetry. In this work, we investigate the effects of such chemical disorder on phase stabilities and magnetic properties using first-principles electronic structure methods. We find that except Mn$_{2}$NiAl, all other alloys show signatures of martensitic transformations in presence of anti-site disorder at the sublattices with tetrahedral symmetry. This improves the possibilities of realizing martensitic transformations at relatively low fields and the possibilities of obtaining significantly large inverse magneto-caloric effects, in comparison to perfect inverse Heusler arrangement of atoms. We analyze the origin of such improvements in functional properties by investigating electronic structures and magnetic exchange interactions.