Effect of Ni doping on the magnetic and electronic properties of half heusler Cu_1-xNi_xMnSb alloys

The effect of Ni-doping on the magnetic and electronic properties of cubic half heusler Cu_1-xNi_xMnSb (x = 0.04, 0.07, 0.1, 0.125) compounds have been investigated both experimentally and theoretically in light of the development of half-metallic ferromagnetism (HMFM) in x = 1, NiMnSb. Our findings reveal that Ni-substitution introduces ferromagnetic (FM) correlations within the parent AFM matrix of CuMnSb. This is followed by the reduction in spin-down density of states (DOS) at the Fermi energy (E_F), verified from the gradual suppression of T²-dependency in the low T resistivity variation upon increasing doping content. The ab-initio electronic structure calculations further suggest that the Sb p-holes, produced upon Ni doping, mediate the RKKY-type indirect FM exchange between the distant Mn atoms, and consequently, the spin-down DOS starts to get depleted at the Fermi energy. Further the importance of the Sb p-holes in mediating ferromagnetic (FM) exchange interaction, is illustrated theoretically on Fe-doped Cu_1-x Fe_xMnSb systems having identical crystal structure, where appreciable Sb holes stabilizes FM correlations at much lower concentration of Fe.