Polarized single crystal absorption spectroscopy of the Pnam-P2 1/a transition of Ilvaite Ca(Fe2+, Fe3+)Fe2+Si2O8(OH) as measured between 300 K and 450 K |
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Authors: | B. Güttler E. Salje S. Ghose |
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Affiliation: | 1. Department of Earth Sciences, University of Cambridge, Downing Street, CB2 3EQ, Cambridge, UK 2. Interdisciplinary Research Centre for Superconductivity, Cambridge 3. Department of Geology, University of Washington, Seattle, USA
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Abstract: | The temperature dependence of the absorption spectra of ilvaite, Ca(Fe2+,Fe3+)Fe2+Si2O8(OH), shows strongly one dimensional transport behaviour with no singularity at the Pnam-P21/a phase transition point near 335 K. Polarized single crystal transmission measurements were carried out between 300 K and 450 K in a frequency range between 600 and 23 000 cm−1. No Drude —absorption at low energies was found at any temperature. A macroscopic, thermodynamic model based on Landau-Ginzburg theory is given which accounts for the observed macroscopic properties of the structural phase transition and its coupling with the Fe2+-Fe3+ ordering. This ordering scheme is discussed on an atomistic level and compared with the behaviour of magnetite and trans-(CH) x . |
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