Synthesis, crystal structures, and magnetic properties of new 12L-Perovskites Ba4LnRu3O12 (Ln = lanthanides)

Synthesis, crystal structures, and magnetic properties of new quaternary oxides Ba(4)LnRu(3)O(12) (Ln = lanthanides) were investigated. From the powder X-ray and neutron diffraction measurements, it is found that they adopt the 12L-perovskite-type structures consisting of Ru3O12 trimers and LnO(6) octahedra. The Ba(4)LnRu(3)O(12) for Ln = Tb-Lu have a hexagonal unit cell with the space group R3m, while those for Ln = La-Nd, Sm-Gd have a monoclinically distorted cell with C21m. Only for Ln = Ce, Pr, and Tb compounds, the Ln ions are in the tetravalent state. The magnetic properties of these three compounds were investigated. For Ba4CeRu3O12, no magnetic transition was observed down to 0.5 K. The Ba4PrRu3O12 and Ba4TbRu3O12 show an antiferromagnetic transition at 2.4 and 24 K, respectively. The magnetic structure for Ba4TbRu3O12 was determined by powder neutron diffraction measurements at low temperatures, which indicates the long-range antiferromagnetic ordering.