Decoupling of superconducting layers in the magnetic superconductor RuSr2GdCu2O8 -: art. no. 184501

We propose the model for magnetic properties of the magnetic superconductor RuSr2GdCu2O8, that incorporates the theory of the superconducting/ferromagnetic multilayers. The transition line T-d(h), on which the Josephson coupled superconducting planes are decoupled, i.e., j(c)(T-d) = 0. is calculated as a function of the exchange energy h. As the result of this decoupling a nonmonotonic behavior of magnetic properties. such as the lower critical field H-c1, Josephson plasma frequency, etc., is realized near (or by crossing) the Td(h) line. The obtained results are used in analyzing the newly discovered anti ferromagnetic ruthenocuprate RuSr2GdCu2O8 with possible weak ferromagnetic order in the RuO2 planes.