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 Co2Ga2−xMx(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.