Polarized single crystal absorption spectroscopy of thePnam-P21/atransition of Ilvaite Ca(Fe2+, Fe3+)Fe2+Si2O8(OH) as measured between 300 K and 450 K
✍ Scribed by B. Güttler; E. Salje; S. Ghose
- Publisher
- Springer-Verlag
- Year
- 1989
- Tongue
- English
- Weight
- 972 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0342-1791
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✦ Synopsis
The temperature dependence of the absorption spectra of ilvaite, Ca(FeZ+,Fe3+)FeZ+Si2Os(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 Fe 2 +-Fe 3 + ordering. This ordering scheme is discussed on an atomistic level and compared with the behaviour of magnetite and trans-(CH)~.