Martensitic transition, ferrimagnetism and Fermi surface nesting in Mn2NiGa

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.