SYNTHESIS, CRYSTAL-STRUCTURE, AND MAGNETIC-PROPERTIES OF COMPLEX OXIDES CU2BSBO6 (B=MN, FE, A) WITH A BIXBYITE STRUCTURE

New complex oxides Cu2BSbO6 (B = Mn3+, Fe3+, Ga3+) with a body-centere d cubic elementary cell (the bixbyite type structure) and parameters 9 .5667(3), 9.5622(3), and 9.5237(3) angstrom, respectively, have been s ynthesized in air at 950-degrees-C from simple Cu, Sb, Mn, Fe, and Ga oxides. Rietveld's method of full-profile analysis was employed to ref ine the structure parameters of one of the obtained compounds, Cu2FeSb O6. Sb occupies 8b sites and Cu and Fe are in 24d sites. From cation-o xygen and oxygen-oxygen interatomic distances, it was shown that Sb oc curs within an almost regular SbO6 octahedron (R(Sb-O) = 2.00 angstrom ), while Fe and Cu are located inside strongly distorted octahedra (R( M-O) (angstrom) = 1.938, 2.020, and 2.311). Magnetic susceptibility ch i of the compounds was measured. For Cu2GaSbO6, chi(T) obeys the Curie -Weiss law in the temperature range 77-300 K. For Cu2+, the values of Weiss's constant and the magnetic moment (c = 0.42, mu = 1.81mu(B)) ar e close to the theoretical ones. A transition to the antiferromagnetic state was observed at 15.6 K for Cu2FeSbO6 and at 5.9 K for Cu2MnSbO6 . (C) 1994 Academic Press, Inc.