title: Syntheses, structures, and magnetic properties of nickel-doped lepidocrocite titanates.
abstract: Ni-doped titanate Cs(x)Ti(2-x/2)Ni(x/2)O(4) and its protonic derivative H(x)Ti(2-x/2)Ni(x/2)O(4) x xH(2)O (x = 0.7) were synthesized and characterized by means of synchrotron X-ray diffraction, Raman scattering, X-ray photoelectron spectroscopy (XPS), and magnetic measurements. Cs(x)Ti(2-x/2)Ni(x/2)O(4) crystallizes in an orthorhombic structure (space group Immm), consisting of infinite two-dimensional (2D) host layers of the lepidocrocite (gamma-FeOOH) type. The substitution of Ni atoms for Ti in the 2D octahedral layers results in negative charges that are compensated by interlayer Cs(+) ions. Raman scattering and XPS indicate that local structural perturbations are induced upon exchange of interlayer Cs ions with protons H(3)O(+). Magnetic measurements reveal typical paramagnetism induced by Ni substitution; the effective paramagnetic moment mu(eff) = 1.57(1) mu(B) and Curie-Weiss temperature -2.51(1) K are obtained for H(x)Ti(2-x/2)Ni(x/2)O(4) x xH(2)O. Ni- and Mg-codoped titanates Cs(x)Ti(2-x/2)(Ni(y)Mg(1-y))(x/2)O(4) (x = 0.7, 0 < or = y < or = 1) were also reported. The crystal structure, interlayer chemistry, and magnetic properties of the titanates depend on the Ni substitution levels, indicating opportunities for tuning of the properties by controlling the nature and level of lattice substitutions.
authors.affiliation: Centre for Materials Science and Nanotechnology and Department of Chemistry, University of Oslo, P.O. Box 1033, N-0315 Oslo, Norway. tao.gao@kjemi.uio.no
authors.forename: Tao
authors.initials: T
authors.lastname: Gao
authors.forename: Poul
authors.initials: P
authors.lastname: Norby
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Okamoto
authors.forename: Helmer
authors.initials: H
authors.lastname: Fjellvåg