Crystal Structures and Magnetic Properties of Nickel Chain Compounds PbM2Ni6Te3O18 (M = Mn, Cd).

The synthesis, crystal structures, and magnetic properties of the pentanary oxides PbM2Ni6Te3O18 (M = Mn and Cd) were investigated. These compounds crystallize in a hexagonal structure with space group P63/m, in which the Ni(2+) ions form a zigzag chain along the c axis. From the magnetic susceptibility and specific heat measurements, we found that the PbCd2Ni6Te3O18 behaves as a low-dimensional magnet due to the intrachain antiferromagnetic interaction between Ni(2+) ions. Both compounds show a long-range antiferromagnetic ordering at 25.7 K (M = Cd) and 86.0 K (Mn). The magnetic structure of PbMn2Ni6Te3O18 determined by neutron diffraction measurements is a collinear antiferromagnetic arrangement of Mn(2+) ions in the Mn2O9 dimeric unit and Ni(2+) ions in the zigzag chain.