Proximity effect and superconducting transition temperature in superconductor/ferromagnet sandwiches

Abstract

The theory of proximity effect for superconductor/ferromagnet (SC/FM) sandwiches is developed. The superconducting transition temperature Tc of a sandwich is calculated taking into account the finite transparency of the SC/FM interface, the exchange splitting of conduction band and breaking of superconducting pairs in the ferromagnetic layer(s). It is found that in SC/FM bilayers and FM/SC/FM trilayers Tc may exhibit nonmonotonic, oscillating or re-entrant behavior as a function of the ferromagnetic layer(s) thickness. The qualitative relevance of the theory to existing experiments is discussed. The experiment which allows one to distinguish the formation of 'π-phase' or '0-phase' in SC/FM multilayer systems is proposed. © 1998 Elsevier Science B.V. All rights reserved.