Observation of a spin-singlet proximity effect in a superconductor/ferromagnet interface

Abstract

Since a spin-singlet superconductor (SC) and a ferromagnet (FM) have ground states with conflicting spin configurations, the superconducting order in a FM in proximity contact with a SC is bound to be suppressed. However, a rather long-range proximity effect has been observed in a metallic FM of a SC/FM junction. Recently, the possible formation of long-range spin-triplet pairing at the SC/FM interface has also been claimed. In this study, we examined the superconducting proximity effect in a simple spin-singlet SC/FM interfacial structure, where the formation of long-range spin-triplet pairing was highly unlikely. We suggest that the finite resistance reduction of the FM segment observed in this study due to the proximity contact to a SC is explicable by the ordinary short-range spin-singlet proximity effect combined with a current redistribution through the SC overlay due to the Andreev reflection at the interface of the unpolarized electrons in the FM.