Mössbauer spectroscopy, magnetic, and ab initio study of the Heusler compound Fe2NiGa

The structural, electronic, magnetic, elastic, and hyperfine-interaction properties of Fe2NiGa have been determined by means of X-ray diffraction, 57Fe Mössbauer spectroscopy, and magnetic measurements and ab initio calculations. The compound studied crystallizes in the cubic space group F4¯3m with lattice constant a=5.7961(4)A˚. Evidence is provided for the presence of significant structural disorder in the compound. Fe2NiGa is predicted to be half-metallic with covalent chemical bonding. It orders ferromagnetically with the Curie temperature TC=586.0(7)K. The saturation magnetization per formula unit and the estimated Fe magnetic moments at the A and B sites are 3.00, 1.87(2), and 2.25(2) μB, respectively. The ab initio calculations overestimate the values of the A- and B-site Fe magnetic moments. It is observed that the magnetic properties of Fe2NiGa are very strongly dependent on its heat treatment. The calculated hyperfine-interaction parameters show general agreement with the experimental ones. It is demonstrated that the compound studied decomposes when heated and kept at temperatures above around 500 K. The Debye temperature of Fe2NiGa is found to be 378(5) K.