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 (∼65-83-at.% La). From the data on $T_c$, the temperature dependence of the upper critical field $H_{c2\mathrm{}}\mathrm{}\left(T\right)\mathrm{}$, and the residual-resistivity values, we estimate the coherence length $\xi \mathrm{}\left(o\right)\mathrm{}$, the density of states at Fermi level $N\left(E_{\mathrm{F}}\right)$, and the electron-phonon coupling parameter $\lambda$ 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.