On the theory of ferromagnet/superconductor heterostructures

We investigate ferromagnet/superconductor/ferromagnet (F/S/F) hybrid structures in the dirty limit, described by the Usadel equations. More precisely, the critical temperature is studied as a function of the ferromagnetic layer thickness for parallel and antiparallel orientations of the ferromagnetic moments. We show that an asymmetry in the ferromagnetic layers may lead to an enhancement of the spin-valve effect, while spin-flip scattering leads to its decrease, which could explain the small experimentally measured values. We also show that the interplay between a superconducting and a ferromagnetic layers implies an induced magnetic moment in the superconductor that is non-monotonic with the ferromagnetic layer thickness as well as a spatially modulated electronic moment in the ferromagnet.