Domain-wall superconductivity in hybrid superconductor-ferromagnet structures

On the basis of a phenomenological Ginzburg-Landau approach we investigate the problem of order parameter nucleation in hybrid superconductor-ferromagnet systems with a domain structure in an applied external magnetic field. Both isolated domain boundaries and periodic domain structures in ferromagnetic layers are considered. We study the interplay between superconductivity localized at the domain walls and far from the walls and show that such an interplay determines a peculiar field dependence of the critical temperature T-c. For a periodic domain structure the behavior of the upper critical field of superconductivity nucleation near T-c is strongly influenced by the overlapping of the superconducting nuclei localized over different domains.