スピネル固浴体Fe3O4-Mn3O4系およびFe3O4-Fe2TiO4系の席対称の変化

概要

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Site symmetry of tetrahedral (A) and octahedral (B) sites of the spinel structures in the solid solulion of Fe3O4-Mn3O4 and Fe3O4-Fe2TiO4 varies microscopically with their cation distribution. Variations of the local distortion due to the Jahn-Teller distortion of Mn3+ in B site affect the electric field gradient of cations. This gradient is related to the nuclear quadrupole splitting in the Mossbauer spectra. The above variations also affect lattice vibration, which is recognized by the far-infrared absorption spectra. Factors obtained from these spectra shift continuously over the whole range of Fe3O4-Mn3O4 solid solution. Atomic positional disorder and electron localization by the Jahn-Teller effect give rise to the local distorion, which affects anisotropic temperature factors. From this point of view, X-ray crystal structure analysis can be used for the observation of local displacement of atomic position resulting from the variation of local site symmetry. The structure analysis of Fe3O4-Fe2TiO4 solid solution shows that temperature factors of oxygen considerably varies with the degree of substitution and displacement of oxygen atom results in the local distortion of polyhedra. The observations of these different types of methods give a consistent result for the local site symmetry of the solid solutions.
日本結晶学会の論文