Magnetic properties and electronic structure of Mn-Ni-Ga magnetic shape memory alloys

Abstract

Influence of disorder, antisite defects, martensite transition and compositional variation on the magnetic properties and electronic structure of Mn${}_2$NiGa and Mn${}_{1+x}$Ni${}_{2-x}$Ga magnetic shape memory alloys have been studied by using full potential spin-polarized scalar relativistic Korringa-Kohn-Rostocker (FP-SPRKKR) method. Mn${}_2$NiGa is ferrimagnetic and its total spin moment increases when disorder in the occupancy of Mn${}_{\mathrm{Ni}}$ (Mn atom in Ni position) is considered. The moment further increases when Mn-Ga antisite defect[1] is included in the calculation. A reasonable estimate of $T_C$ for Mn${}_2$NiGa is obtained from the exchange parameters for the disordered structure. Disorder influences the electronic structure of Mn${}_2$NiGa through overall broadening of the density of states and a decrease in the exchange splitting. Inclusion of antisite defects marginally broaden the minority spin partial DOS (PDOS), while the majority spin PDOS is hardly affected. For Mn${}_{1+x}$Ni${}_{2-x}$Ga where 1$\ge$$x$$\ge$0, as $x$ decreases, Mn${}_{\mathrm{Mn}}$ moment increases while Mn${}_{\mathrm{Ni}}$ moment decreases in both austenite and martensite phases. For $x$$\ge$ 0.25, the total moment of the martensite phase is smaller compared to the austenite phase, which indicates possible occurrence of inverse magnetocaloric effect. We find that the redistribution of Ni 3$d$- Mn${}_{\mathrm{Ni}}$ 3$d$ minority spin electron states close to the Fermi level is primarily responsible for the stability of the martensite phase in Mn-Ni-Ga.

10 pages, 5 figures

References in corpus (5)

• Advanced materials for solid-state refrigeration
• Cooling and heating by adiabatic magnetization in the Ni${}_{50}$Mn${}_{34}$In${}_{16}$ magnetic shape memory alloy
• Martensitic transition, ferrimagnetism and Fermi surface nesting in Mn_2NiGa
• First-principles calculation of the instability leading to giant inverse magnetocaloric efects
• Magnetoresistance behavior of a ferromagnetic shape memory alloy: Ni_1.75Mn_1.25Ga

Cited by in corpus (3)

• Ab initio Studies on Electronic and Magnetic Properties of X${}_2$PtGa (X = Cr, Mn, Fe, Co) Heusler Alloys
• Interplay of phase sequence and electronic structure in the modulated martensites of Mn${}_2$NiGa from first-principles
• Bulk Electronic Structure of Ni2MnGa studied by Density Functional Theory and Hard X-ray Photoelectron Spectroscopy