Enhancement of ferromagnetism in Ni excess Cu_1−xNi_xMnSb half Heusler alloys

Spin momentum densities of Cu_1−xNi_xMnSb (for x = 0.17 and 0.22), derived from experimental magnetic Compton profiles (MCPs), show an increase in magnetic moment while going from x = 0.17 → 0.22, which is attributed to Mn 3d states. MCPs along with magnetization data suggest a negligible contribution of orbital moment. The MCPs and spin moments at Mn 3d states computed using the spin polarized relativistic Korringa-Kohn-Rostoker technique are in good agreement with the experimental data. An unusual increase in magnetic moment (2.77 ± 0.03 μ_B/f.u. for x = 0.17 to 3.94 ± 0.03 μ_B/f.u. for x = 0.22) is due to significant rise in local magnetic moment on Mn site. For x = 0.22 (0.17), presence of antiferromagnetic phase is observed to be 2 (31)%.