Proximity effects in multiband superconductor–ferromagnetic metal structures

Abstract

Proximity effects in multiband superconductor/ferromagnetic metal (S/F) structures are considered. In the limit when the transport properties of both metals correspond to the diffusion conductivity type, the general form of the Usadel equations and their quasiclassical boundary conditions are formulated. For several limiting cases, analytical solutions of the Usadel equations are obtained. It is shown that induced (proximity) characteristics reflect the multiband structure of the superconductor and significantly depend on the SF boundary parameters and the exchange interaction magnitude in the F layer. Main manifestations of the magnetic proximity effect in the S layer near the SF boundary are considered: additional suppression of the superconducting order parameter by the exchange field, spin splitting of the quasiparticle density of states, the emergence of localized states inside the energy gap, and induced equilibrium magnetization of unpaired electrons in the S layer.