Crystal and magnetic structures of A2YRu1-xCuxO6 with A = Sr, Ba and x=0.05 to 0.15

A series of mixed ruthenium-copper oxides of general formulae A(2)YRu(1-x)Cu(x)O(6) with A = Sr, Ba and x = 0.05 to 0.15 were prepared by high temperature synthesis. Electrical and magnetic measurements confirmed the samples were superconducting. Variable temperature neutron powder diffraction studies were undertaken to determine the crystal and magnetic structures of the materials in the temperature range 2-100 K. Both series are double perovskites with the Sr compounds adopting a distorted structure with space group P2(1)/n and the Ba materials in the cubic space group Fm3m. The neutron diffraction patterns clearly show the development of extra peaks at temperatures similar to30-40 K indicative of long-range magnetic order. Refinements of the data indicate that the Ru5+ ions adopt a Type I magnetic structure for both series with a magnetic moment at 2 K of similar to2.4(1) mu(B) in the ab plane. The magnetic moment is found to increase slightly with increased copper doping in the Sr series, whereas the Ba series has a higher magnetic ordering temperature due to higher symmetry of the crystal structure.