Martensitic transition, ferrimagnetism and Fermi surface nesting in Mn₂NiGa

Abstract

The electronic structure of Mn₂NiGa 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. Mn₂NiGa 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.