Interface transparency of superconductor/ferromagnetic multilayers

Abstract

We have investigated the behavior of the superconducting transition temperature (Formula presented) in superconducting/ferromagnetic (S/F) multilayers, as a function of the different layer thicknesses and for varying magnetic moment (Formula presented) of the F-layer atoms. The system studied consists of superconducting V and ferromagnetic V(Formula presented)Fe(Formula presented) alloys with (Formula presented) such that (Formula presented) on the Fe atom is varied between 2 and 0.25(Formula presented) We determined the superconducting coherence length in the F layer (Formula presented) which is found to be inversely proportional to (Formula presented) We also determined the critical thickness of the S layer, above which superconductivity appears. This thickness is found to be strongly nonmonotonic as function of the Fe concentration in the alloys. By analyzing the data in terms of the proximity-effect theory, we show that with increasing (Formula presented) the increasing pair breaking in the F layer by the exchange field is counteracted by a decreasing transparency of the S/F interface for Cooper pairs. © 1997 The American Physical Society.