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

Abstract

A series of mixed ruthenium–copper oxides of general formulae A₂YRu_1−xCu_xO₆ 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 P2₁/n and the Ba materials in the cubic space group Fm3m. The neutron diffraction patterns clearly show the development of extra peaks at temperatures ∼30–40 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 ∼2.4(1) μ_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.