Site-preferences and local spin-polarization of transition metal solute atoms in B2 type Ni–Al alloys

In the framework of the Local Spin Density Approximation we study the electronic structure, site preference energies and magnetism in B2 Ni50(Al37.5Ni12.5) alloys doped with 3d-transition metals using a Coherent Potential Approximation for treating effects of substitutional disorder. We find that the lattice expands also for non-magnetic Ti and V substitutions and thus this effect cannot entirely be related to magnetism as it was conjectured earlier. Except Co all TM atoms are found to prefer the Al sublattice. For the magnetic substitutions (Cr, Fe, Mn) we also find that the lattice expands independently on the state of magnetic order – only local atomic spin-polarization is important. An effective magnetic coupling between substituted atoms has been calculated and it is shown that it does not scale with the magnitude of the local moments.