Growth and structural characterization of single crystals of the magnetic superconductor Ru1−xSr2−yGd1+yCu2+xO8−δ (RuGd-1212) obtained by the partial melting technique

In this study, cubic single crystals of the magnetic superconductor Ru1−xSr2−yGd1+yCu2+xO8−δ (RuGd-1212) with typical dimensions of 100-150 µm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.