Martensitic transition, ferrimagnetism and Fermi surface nesting in Mn_2NiGa

TL;DR

This study combines theoretical and experimental methods to analyze the electronic structure and phase transitions in Mn_2NiGa, revealing ferrimagnetism, Fermi surface changes, and phonon softening associated with martensitic transformation.

Contribution

It provides new insights into the electronic and magnetic properties of Mn_2NiGa across phases, highlighting Fermi surface nesting and its role in martensitic transition.

Findings

Martensitic phase is more stable with c/a=1.25.

Mn_2NiGa exhibits ferrimagnetism in both phases.

Fermi surface nesting suggests phonon softening and modulation.

Abstract

The electronic structure of Mn_2NiGa has been studied using density functional theory and photoemission spectroscopy. The lower temperature tetragonal martensitic phase with c/a= 1.25 is more stable compared to the higher temperature austenitic phase. Mn_2NiGa is ferrimagnetic in both phases. The calculated valence band spectrum, the optimized lattice constants and the magnetic moments are in good agreement with experiment. The majority-spin Fermi surface (FS) expands in the martensitic phase, while the minority-spin FS shrinks. FS nesting indicates occurrence of phonon softening and modulation in the martensitic phase.