Magnetic exchange coupling and Curie temperature of Ni(1+x)MnSb (x=0,   0.25, 0.5, 0.75, 1) from first principles
  We study the dependence of magnetic interactions and Curie temperature in Ni(1+x)MnSb system on the Ni concentration within the framework of the density-functional theory. The calculation of the exchange parameters is based on the super-cell and frozen-magnon approaches. The Curie temperatures, Tc, are calculated within the random-phase approximation. In agreement with experiment we obtain decrease of the Curie temperature with increasing Ni content. 
E. Sasioglu, L. M. Sandratskii, P. Bruno