Finite range scattering of Ni and Zn impurities in Y-123 thin films

Abstract We investigated YBa 2 (Cu 1− z M z ) 3 O 7-δ (M Ni,Zn) thin films and determined the decrease of T c and the increase of residual resistivity due to Cu-site substitution, taking into account the CuO-chain contributions to the total conductivity. Although Zn suppresses T c stronger than Ni by a factor of 2.3 the increase of resistivity differs only slightly. Furthermore the observed resistivities are too high to be explained within scattering from point-like defects. To reconcile these contradictions, we assumed finite size scattering potentials, which lead to scattering phase shifts δ l of higher angular momebtum l > 0. T c -suppression is discussed qalitatively within this picture.