Magnetism and superconductivity in Sr2YRu1-uCuuO6 and magnetism in Ba2GdRu1-uCuuO6

We report magnetization, surface resistance (), and electron spin resonance (ESR) for non-superconducting Ba 2 GdRu 2 Cu u O 6 , 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 ( K) Sr 2 YRu 1- u Cu u O 6 , resistivity, muon spin rotation (µ + SR), and 99 Ru Mossbauer absorption are reported. None of the O 6 materials ( e.g. , Sr 2 YRu 1- u Cu u O 6 ) have cuprate planes, although Cu is employed as a dopant. In Sr 2 YRu 1- u Cu u O 6 , 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 O 6 structure, the SrO layers, carry holes and exhibit diamagnetic screening characteristic of type-II superconductivity.