Anisotropic superconductors containing transition-metal impurities: Local spin fluctuations

Abstract

The effects of transition-metal (TM) impurities on the transition temperature of an anisotropic superconductor when the TM impurities give rise to local spin fluctuations (LSFs) are studied. The effective electron-electron interaction between the Cooper-pair electrons is taken to be the sum of a separable anisotropic electron-phonon potential and the repulsive Coulomb potential existing between the electrons. The multiplicative renormalization technique is used to treat the Coulomb repulsion between the d electrons of opposite spins which localize about an impurity site. It is found that the LSFs influence the anisotropic superconductors in two ways. They cause a decrease in the anisotropy and an increase in the Coulomb pseudopotential. Numerical calculations of the decrease in Tc are carried out using parameters appropriate to the dilute AlMn superconductors. © 1986 The American Physical Society.