Raman spectroscopy of low-temperature ( P n m a ) and high-temperature ( R 3 ¯ c</mml:mi…
2006; American Physical Society; Volume: 74; Issue: 21 Linguagem: Inglês
10.1103/physrevb.74.214301
ISSN1550-235X
AutoresM. N. Iliev, A. P. Litvinchuk, V. G. Hadjiev, Y.-Q. Wang, J. Cmaidalka, R.L. Meng, Yanyi Sun, Nikolay Ivanov Kolev, M. V. Abrashev,
Tópico(s)Advanced Condensed Matter Physics
ResumoWe present the polarized Raman spectra of $\mathrm{La}\mathrm{Cr}{\mathrm{O}}_{3}$ measured between 5 and $863\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ in several exact scattering configurations. All Raman lines below $600\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ are assigned to definite phonon modes of $Pnma$ $(\mathrm{T} 528\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ structures on the basis of their polarization properties, comparison to spectra of isostructural compounds, and comparison to mode frequencies predicted by calculations of lattice dynamics. The broad overlapping high-frequency bands between 600 and $750\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ of ${A}_{g}$ character, which are sample dependent and vary significantly upon annealing in vacuum or change of excitation photon energy, are assigned to local vibrations of ${\mathrm{Cr}}^{4+}$-related defect species. These results can serve as a ground for further study of microstructure-property relationships in practically important doped rare earth chromates.
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