Magnetism and superconductivity in Sr₂YRu_1-uCu_uO₆ and magnetism in Ba₂GdRu_1-uCu_uO₆

We report magnetization, surface resistance (R_S(T,H)), and electron spin resonance (ESR) for non-superconducting Ba₂GdRu_1-uCu_uO₆, and find that all three magnetic ions (Gd, Ru, and Cu) are ordered at low temperatures. Both ESR (Gd sublattice) and weak ferromagnetic resonance (dopant Cu) are observed while no magnetic resonance due to either paramagnetic or ordered Ru is detected. In addition, for superconducting (T_c ∼ 45 K) Sr₂YRu_1-uCu_uO₆, resistivity, muon spin rotation (μ⁺ SR), and ⁹⁹Ru Mössbauer absorption are reported. None of the O₆ materials (e.g., Sr₂YRu_1-uCu_uO₆) have cuprate planes although Cu is employed as a dopant. In Sr₂YRu_1-uCu_uO₆, the Ru moments order at a temperature (∼23 K) below that for the resistive onset of superconductivity, while the Cu orders at a higher temperature, ∼86 K. Therefore at low temperatures, this material exhibits magnetic order, coexisting with diamagnetism. The only non-magnetic layers in the superconducting O₆ structure, the SrO layers, carry holes and exhibit diamagnetic screening characteristic of type-II superconductivity.