Suppression of superconductivity in ruthenium alloys

Existing data on the depression of the superconducting transition temperature of Ru by Co, Ni, Ft, Pd, Rh and Ir impurities are analysed using Kaiser's model, which considers resonant scattering from non-magnetic impurity states. Numerical values for various parameters characterising this resonant d-state are thus derived; in particular estimates of the intra-impurity Coulomb repulsion are obtained from which the presence (or absence) of localised spin fluctuations in these alloy systems is inferred.