Martensitic transition, ferrimagnetism and Fermi surface nesting in Mn ₂ NiGa

Abstract

PACS. 81.30.Kf -Martensitic transformations PACS. 71.20.Be -Electron density of states and band structure of transition metals and alloys PACS. 71.18.+y -Fermi surface: calculations PACS. 71.15.Nc -Total energy calculationsThe electronic structure of Mn 2 NiGa 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 2 NiGa 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.PACS numbers:

Theoretical prediction and experimental study of a ferromagnetic shape memory alloy:Ga2MnNi

“…34 Since the tetragonal structure is not computationally demanding, precise calculations can be performed for lattice constant optimization in the lowest energy magnetic state. 20,21,22 Thus, the total energy difference can be determined with sufficient accuracy and thus T M estimated. However, difference in T M between experiment and theory could occur, as in this case, possibly because the latter does not consider the actual structure.…”

“…The reasons for this disagreement could be that the actual sample has Mn excess, which might cause Mn clustering leading to antiferromagnetic coupling between Mn atom pairs, as has been observed for other Mn excess systems. 22,32,33 Moreover, note that the theory does not consider the actual monoclinic structure (discussed below) which might favor a different magnetic ground state with anti-parallel coupling between Mn atoms.…”

Magnetic properties of new compounds RuMn2Sn and RuMn2Si

“…Both experimental and theoretical studies made clear that NiMn 2 Ga crystallizes in the Hg 2 CuTi-type structure (space group F43m), which is different from the L2 1 structure with Fm3m space group [8]. Simultaneously, Barman et al discussed the martensitic transition, ferrimagnetism and Fermi surface nesting using a firstprinciples calculation [9,10]. Liu et al investigated theoretically and experimentally the electronic structures and magnetic properties of CoMn 2 Z (Z = Al, Ga, In, Si, Ge, Sn and Sb) compounds [11].…”

Electronic, magnetic, and structural properties of the ferrimagnet Mn2CoSn

“…The desired properties of the materials Mn 3?x Ga can easily be tuned by substitution of elements, i.e., variation of the Mn:Ga ratio. The recently discovered ferrimagnetic shape memory compound Mn 2 NiGa exhibits a record-breaking magnetic-field-induced strain of approximately 21% in its single crystalline form [21,22]. Co 2 -based Heusler compounds often follow the Slater-Pauling rule, which is a signature for their half metallicity.…”