Critical temperature of a ferromagnet/superconductor structures in a parallel magnetic field

Two- and three-layered structures consisting of ferromagnetic metal (F) film and superconductor (S) film are considered in the magnetic field H applied parallel to the plane of the F/S interface. Magnetic-penetration depth is presumed much greater than thicknesses of layers. Assuming that both S and F layers are dirty the boundary problem for the Usadel function is solved taking account of so called "Umklappprocesses" for momenta of superconducting pairs on the F/S interface. It is shown that the field H can significantly alter a functional form of the dependence of critical temperature T(c) versus thickness of the F layer d(f). Keeping in mind the possible applications like the superonducting spin-valve the behavior of T(c)(d(f)) for the F/S/F trilayer in the magnetic field is investigated.