Nonhomogeneous magnetization and superconductivity in superconductor/ferromagnet structures

We study two different superconductor/ferromagnet (S/F) structures. We consider first a Josephson junction which consists of two S/F bilayers separated by an insulating layer. We show that for an antiparallel alignment of the magnetization in the two F layers the Josephson critical current 1, increases with increasing exchange field h. The second system we consider is a S/F structure with a local inhomogeneity of the magnetization in the ferromagnet near the S/F interface. Due to the proximity effect not only a singlet but also a triplet component of the superconducting condensate is induced in the ferromagnet. The latter penetrates over the length rootD/epsilon (D is the diffusion coefficient and E the energy), In the case of temperatures of the order of the Thouless energy this length is comparable to the length of the ferromagnet. This long-range penetration leads to a significant increase of the ferromagnet conductance below the superconducting critical temperature T-c. (C) 2002 Elsevier Science B.V. All rights reserved.