Transition metal impurities in CoGa

Isolated transition metal impurities on Ga sites in β-phase CoGa have been studied by treating 9, 15, and 27-atom clusters representative of the compounds Co₂Ga_2-xM_x(M = Ti, V, Cr, Co), for small values of x. Self-consistent calculations performed on MCo₈ and MCo₈Ga₆ clusters give an incomplete description of the local magnetic environment of off-center Co atoms. The addition of a new shell of atoms, so that 7 of the 8 nearest neighbors of these Co atoms were explicitly included in the cluster, led to marked reduction of spurious peripheral atom magnetization. Results for the MCo₈Ga₆Ga₁₂ clusters, indicate that isolated impurity atoms on Ga sites are non-magnetic, in agreement with experimental interpretations.