Supercurrents through SNS Junctions with Thick Cu Layer Doped with Mn

The maximum supercurrent I c passing through the S(Nb)-N(Cu doped with Mn)-S(Nb) junction made of Cu-clad Nb wire has been measured down to 30 mK, in order to investigate the relation between the superconducting proximity effect and the Kondo effect. The maximum supercurrent becomes small with an increase in Mn concentration and remarkably with a decrease in electronic mean free path in Cu. The electronic mean free path dependence of I c may be explained qualitatively in consideration of the spin flip scattering and the RKKY interaction of Mn impurities. The Meissner effect induced by the proximity effect in Cu-clad Nb wire can be understood through the behavior of the coherence length ξ N in Cu which is derived from I c .