Site occupancy, composition and magnetic structure dependencies of martensitic transformation in Mn$_{2}$Ni$_{1+x}$Sn$_{1-x}$

TL;DR

This study uses first-principles calculations to analyze how site occupancy, composition, and magnetic order influence the martensitic phase stability in Mn$_{2}$Ni$_{1+x}$Sn$_{1-x}$, revealing the critical role of Mn occupancy at specific lattice sites.

Contribution

It identifies the dominant influence of Mn occupancy at 4d sites on martensitic stability, clarifying discrepancies between experiments and previous theoretical models.

Findings

Mn occupancy at 4d sites is crucial for phase stability.

Mn interactions at specific sites determine martensitic phases.

Results align qualitatively with experimental trends in magnetization.

Abstract

A delicate balance between various factors such as site occupancy, composition and magnetic ordering seems to affect the stability of the martensitic phase in Mn$_{2}$Ni$_{1+x}$Sn$_{1-x}$. Using first-principles DFT calculations, we explore the impacts of each one of these factors on the martensitic stability of this system. Our results on total energies, magnetic moments and electronic structures upon changes in the composition, the magnetic configurations and the site occupancies show that the occupancies at the 4d sites in the Inverse Heusler crystal structure play the most crucial role. The presence of Mn at the 4d sites originally occupied by Sn and it's interaction with the Mn atoms at other sites decide the stability of the martensitic phases. This explains the discrepancy between the experiments and earlier DFT calculations regarding phase stability in Mn$_{2}$NiSn. Our results qualitatively explain the trends observed experimentally with regard to martensitic phase stability and the magnetisations in Ni-excess, Sn-deficient Mn$_{2}$NiSn system.