The Crystal Structure of Ba3CuRu2O9 and Comparison to Ba3MRu2O9 (M=In, Co, Ni, and Fe)

The crystal structure of Ba3CuRu2O9, determined by powder neutron diffraction, is reported for temperatures of 18–295 K. Structural refinements by powder neutron diffraction for the previously reported compounds Ba3MRu2O9 for M=Fe, Co, Ni, and In are also reported. All structures consist of pairs of face-shared RuO6 octahedra interconnected by corner-sharing MO6 octahedra. For Ba3CuRu2O9, Jahn–Teller distortion of the CuO6 octahedra leads to an orthorhombic symmetry structure of space group Cmcm with a=5.6723(1), b=10.1722(3), and c=14.1575(3) ? at 295 K. For Ba3FeRu2O9, site occupancy disorder is found. Magnetic ordering is observed below 100, 105, and 110 K for M=Cu, Ni, and Co, respectively. The magnetic structures at low temperatures for M=Co and Ni are described and compared to previous reports.