Proximity effect: Amorphous Sn-Fe, amorphous Bi-Fe films

We report the results of an experimental investigation of the proximity effect in sandwiches of amorphous Bi-Fe and amorphous Sn-Fe. The measurements on a-Bi films resolve a controversy concerning its coherence length while that derived for a-Sn is consistent with values reported from critical-field measurements. The pair penetration depths determined from a new analysis technique are consistent with values derived from other proximity experiments which employ Fe normal layers. A linear decrease of the transition temperature with resistance per square and inverse film thickness, an apparently universal characteristic of amorphous superconducting films, was also observed in these experiments