A FAMILY OF ONE-DIMENSIONAL OXIDES - SR(3)MIRO(6) (M=NI, CU, ZU) - STRUCTURE AND MAGNETIC-PROPERTIES

The structures and magnetic properties of Sr3ZnIrO6, Sr3CuIrO6, and Sr3NiIrO6 are presented. The structure of Sr3NiIrO6 was solved by Rietveld analysis of powder neutron data. The structure refined in space group R $($) over bar$$ 3c, with a = 9.5806(1) and c = 11.1315(2) Angstrom. The structure consists of infinite chains of alternating IrO6 octahedra and NiO6 trigonal prisms. The structures of Sr3ZnIrO6 and Sr3CuIrO6 are closely related to that of Sr3NiIrO6. Magnetic susceptibility studies show that Sr3NiIrO6 undergoes complex magnetic transitions as a function of temperature and achieves a singlet ground state below 15 K. Low-temperature neutron diffraction does not show any evidence for structural changes. Magnetic susceptibility measurements of Sr3CuIrO6 display ferromagnetic ordering below 40 K. Measurements of the saturation magnetization at applied fields of up to 20 T display virtually no hysteresis loop, indicating that Sr3CuIrO6 is a very soft ferromagnet. The saturation magnetization of 0.61 mu(B) is lower than that expected for two unpaired electrons. Sr3ZnIrO6 orders antiferromagnetically. The data were fit to an alternating-chain Heisenberg model. The structures and magnetic properties of these one-dimensional oxides are discussed. (C) 1995 Academic Press, Inc.