Magnetic-superconducting phase diagram of (formula presented)

(formula presented) (Ru-2122) is the first Cu-O-based system in which superconductivity (SC) in the (formula presented) planes and weak ferromagnetism (WFM) in the Ru sublattice coexist. The hole doping in the (formula presented) planes is controlled by appropriate variation of the Ce concentration. SC occurs for Ce contents of 0.4-0.8, with the highest (formula presented) for (formula presented) The as-prepared non-SC (formula presented) (formula presented) sample exhibits magnetic irreversibility below (formula presented) and orders antiferromagnetically (AFM) at (formula presented) The saturation moment at 5 K is (formula presented) close to the expected (formula presented) for the low-spin state of (formula presented) Annealing under oxygen pressures does not affect these parameters, whereas depletion of oxygen shifts both (formula presented) and (formula presented) up to 169 and 215 K, respectively. Systematic magnetic studies of (formula presented) show that (formula presented) (formula presented) and (formula presented) decrease with x, and the full Ce-dependent magnetic-SC phase diagram is presented. A simple model for the SC state is proposed. We interpret the magnetic behavior in the framework of our ac and dc magnetic studies, and argue that (i) the system becomes AFM ordered at (formula presented) (b) at (formula presented) WFM is induced by the canting of the Ru moments: and (c) at lower temperatures, the appropriate samples become SC at (formula presented) The magnetic features are not affected by the SC state, and the two states coexist.