π phase in magnetic-layered superconductors

We show that in a system composed of alternating superconducting and magnetic layers the ground state may be the so-called ‘‘π phase,’’ wherein the superconducting order parameter changes its sign as we go from one superconducting layer to another. This phase is similar to the Larkin-Ovchinnikov-Fulde-Ferrell phase. We find that the π phase exists, under certain conditions, in the presence of both ferro- and antiferromagnetism.