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Start Over Author "Onoda, M." Journal journal of solid state chemistry
9 results on '"Onoda, M."'

4. Modulated Structure of the Composite Crystal Ca0.83CuO2

Author

Miyazaki, Y., Onoda, M., Edwards, P. P., Shamoto, S., and Kajitani, T.

Subjects
*CALCIUM compounds, *COMPOSITE materials, *CRYSTALS, *CHEMICAL structure
Abstract

We have determined the crystal structure of the quasi one-dimensional cuprate Ca0.83CuO2, known as Ca4Cu5O10, etc., by a superspace group approach. The compound consists of two interpenetrating subsystems of CuO2 chains and Ca atoms. Structural parameters were refined with a superspace group of F2/m(1+α 0 γ)0s using powder X-ray and neutron diffraction data. Lattice parameters were refined to be a1=2.8043(2) A˚, b=6.3179(2) A˚, c1=10.5744(5) A˚, and β1=90.10(1)° for the [CuO2] subsystem and a2=3.3652(2) A˚, b=6.3179(2) A˚, c2=10.5893(5) A˚, and β2=93.04(1)° for the [Ca] subsystem. Remarkable displacive modulation of the O and Ca atom sites is observed parallel to the b-axis and the c-axis, respectively. On the other hand, the Cu atom sites deviate mainly in the a direction to yield a periodic fluctuation between the nearest Cu–Cu distances. The Ca atoms suitably sit in the center of the modulated O6 octahedra. [Copyright &y& Elsevier]

Published
2002
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5. Valence Fluctuation in α-CuVO3Studied by Photoemission Spectroscopy

Author

Nakamura, M., Namatame, H., Fujimori, A., Misu, A., Okatake, S., Onoda, M., and Nagasawa, H.

Abstract

We have performed a photoemission study of the mixed-valence semiconductor α-CuVO3(Cu7-xV6O19-x, x∼ 0.38). From the measured spectra we have found that both Cu and V are mixed-valent between Cu+and Cu2+and between V4+and V5+. The mean valences of Cu and V deduced from the spectra suggest a considerably larger number of local magnetic moments than that deduced from the Curie-Weiss magnetic susceptibility, indicating that the magnetic moments of the V4+and Cu2+ions are partially suppressed. Combining the present results with the NMR and ESR data, we proposed that the V4+local moments are totally suppressed by the formation of singlet pairs and the Cu2+local moments are reduced by the Cu+-Cu2+valence fluctuation. The O 2pto Cu 3dcharge-transfer energy deduced from the analysis of the Cu 2pcore-level spectrum is found to be small, which may favor the occurrence of the valence fluctuation at the Cu sites.

Published
1994
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