Disorder dependence of the magnetic moment of the half-metallic ferromagnet NiMnSb from first principles

Using half-metallic ferromagnets in spin-dependent devices, like spin valve s and ferromagnetic tunnel junctions, is expected to increase the device pe rformance. However, using the half-metallic ferromagnet NiMnSb in such devi ces led to much less than ideal results. One of the possible sources for th is behavior is atomic disorder. First-principles calculations of the influe nce of atomic disorder on the electronic structure of NiMnSb underline the sensitivity of half-metallic properties in NiMnSb to atomic disorder. In th is article, we report on the disorder dependence of the total magnetic mome nt calculated by applying the layer Korringa-Kohn-Rostoker method in conjun ction with the coherent potential approximation. We consider the following types of disorder: (1) intermixing of Ni and Mn, (2) partial occupancy of a normally vacant lattice site by Ni and Mn, and (3) partial occupancy of th is site by Mn and Sb. In all cases the composition is kept stoichiometric. All three types of disorder decrease the moment monotonically with increasi ng disorder levels. For the experimentally seen disorder of 5% Mn and 5% Sb on the normally vacant lattice site, the total moment is decreased by 4.1% . The results suggest that precise measurement of the saturation magnetizat ion of NiMnSb thin films can give information on the disorder. (C) 2000 Ame rican Institute of Physics. [S0021-8979(00)50008-5].