Alloying effect on superconductivity in amorphous lanthanum-based alloys

Abstract

The effect of alloying on the superconducting properties of amorphous, liquid-quenched La-based alloys containing Al, Ge, and Au is studied. The transition temperature ${T}_{c}$ of these superconductors depends largely on the La content and is not very sensitive to the second alloy constituent throughout the composition range investigated (\ensuremath{\sim}65-83-at.% La). From the data on ${T}_{c}$, the temperature dependence of the upper critical field ${H}_{c2}(T)$, and the residual-resistivity values, we estimate the coherence length $\ensuremath{\xi}(o)$, the density of states at Fermi level $N({E}_{\mathrm{F}})$, and the electron-phonon coupling parameter $\ensuremath{\lambda}$ as a function of alloy concentration. The implication of these results is that the electron-phonon interaction strength $〈{I}^{2}〉$ is essentially constant, suggesting that superconductivity in these alloys is of a localized nature.