Structural, electronic, magnetic, and transport properties of the equiatomic Ni-based quaternary Heusler alloys

This work reports on three quaternary Hensler alloys NiCuFeGa, NiCuMnGa, and NiFeMnGa. We have investigated the phase stabilities and ordering tendencies in these compositions through, first principle calculations followed by the study of structural, electronic, magnetic, and transport properties through experimental techniques. The crystal structure of all three compositions is characterized using high-resolution synchrotron X-ray diffraction (XRD). NiCuMnGa adopts a cubic LiPdMgSn-type crystal structure, while NiFeMnGa and NiCuFeGa form a mixed phase of tetragonal and cubic symmetry. Transport and magnetic properties have been measured as a function of temperature and magnetic field. The saturation magnetization at 5 K is 4.06 mu(B)/f.u., 3.30 mu(B)/f.u., and 2.42 mu(B)/f.u. for NiCuMnGa, NiFeMnGa, and NiCuFeGa, respectively. All the compositions show typical metallic resistivity with a residual resistivity ratio of 1.32, 2.33, 3.99 for NiCuFeGa, NiCuMnGa, and NiFeMnGa, respectively. First-principles calculations suggest high degree of spin polarization in NiFeMnGa, which is reflected through the power law fittings carried out for its resistivity data. Also, the transition metals present strong ferromagnetic correlations between them, resulting in the Curie temperatures (T-C) lying above room temperature in all three compositions. (C) 2019 Elsevier B.V. All rights reserved.