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Raman study of phonons in CaMn7O12 : effects of structural modulation and structural transition

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Raman study of phonons in CaMn7O12 : effects of structural modulation and structural transition

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Título Raman study of phonons in CaMn7O12 : effects of structural modulation and structural transition
Autor Iliev, Milko N.
Hadjiev, Viktor G.
Gospodinov, Marin
Nikolova, Rositsa Petrova
Abrashev, Miroslav Vergilov
Abstract Polarized Raman spectra of oriented CaMn7O12 single crystals have been studied in a broad temperature range (5–500 K) covering the crystallographic, ferroelectric, and magnetic transitions. From the spectra obtained at room temperature (RT) 10 out of the total 12 Raman active 6Ag + 6Eg modes of the trigonal R¯3 phase have been identified and assigned to definite atomic motions in close comparison to results of lattice-dynamics modeling. With the decrease in temperature below 250 K some Raman bands split, and additional spectral features, not expected for the R¯3 structure, arise well above the magnetic transitions near 90 and 50 K. Their appearance, however, correlateswith the transformation due to incommensurate structural modulation revealed by recent x-ray and neutron-diffraction studies. As temperature increases above RT the intensity of the Raman lines strongly decreases, and entering the high-temperature Im¯3 phase the spectrum transforms its shape to that expected for a structure with disordered Jahn-Teller distortions.
Contido em Physical review. B, Condensed matter and materials physics. Woodbury. Vol. 89, no. 21 (June 2014), 214302, 6 p.
Assunto Espectros raman
Origem Estrangeiro
Tipo Artigo de periódico
URI http://hdl.handle.net/10183/107173
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