New compounds with incommensurate phases: Cs2CdI4 and Cs2ZnI4 |
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Authors: | S V Melnikova S V Primak |
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Institution: | Kirensky Institute of Physics , 660036, Krasnoyarsk, USSR |
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Abstract: | Abstract In this paper the results of birefringence studies and of optical observations in polarized light in a wide temperature region are presented for crystals Cs2CdI4 and Cs2ZnI4. There is the following sequence of phases: commensurate orthorhombic Pnma ? incommensurate ? monoclinic ferroelastic P21/n ? triclinic ferroelastic PT. A correlation was observed between the peculiarities of birefringence and NQR spectra temperature dependence. An assumption is made, that in Cs2ZnI4 crystal in a broad pre-transition region (T - T i = 100 K) precursor clusters exist, which manifest themselves as coexistence of NQR spectra of two phases and as deviation of birefringence from the linear temperature dependence (“tail”). |
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Keywords: | Cs2CdI4 Cs2ZnI4 phase transitions incommensurate phase birefringence NQR spectra |
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