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Syntheses, Structures, and Magnetic Properties of Nickel-Doped Lepidocrocite Titanates

2009; American Chemical Society; Volume: 48; Issue: 19 Linguagem: Inglês

10.1021/ic901251w

1520-510X

Tao Gao, Poul Norby, Hiroshi Okamoto, Helmer Fjellvåg,

Advanced Condensed Matter Physics

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.