Strong-coupling theories for superconductors containing local spin fluctuations

Abstract

Theories for isotropic and anisotropic superconductors containing transition-metal impurities which give rise to local spin fluctuations are developed by use of the Migdal-Eliashberg formalism. The multiplicative renormalization method is used to obtain the normal and anomalous d-electron propagators. The decreases in the transition temperatures of the isotropic and anisotropic superconductors due to the local spin fluctuations are obtained within the framework of the square-well-model version of the Midgal-Eliashberg formalism. Different approaches are used to obtain the decreases for the two cases. The effects of the local spin fluctuations on the jump in the specific heat at Tc of the strong-coupling anisotropic superconductors are also calculated. © 1987 The American Physical Society.