The dependence of the superconducting critical temperature of dilute magnetic alloys on impurity concentration

Abstract

The decrease in superconducting critical temperature Tc with impurity concentration nI is examined for dilute magnetic alloys in the framework of the Kondo-Nagaoka theory. When the critical temperature Tco of the host metal is much larger than the Kondo temperature TK the curves of Tc versus nI behave in the manner predicted by the Born approximation theory of Abrikosov and Gorkov, except for an exponential tail for Tc << TK. When Tco << TK these curves show a non-magnetic behaviour which is related to the theory of the Suhl-Nagaoka spin compensated state. The theory is compared to (i) experimental data for LaCe and ThU and (ii) the theory of localized spin fluctuations which provides an alternative explanation for the data.