Temperature and composition dependence of vibrational modes in Sm1?xLaxAlO3 |
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Authors: | P Alain B Piriou |
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Institution: | U.E.R. Sciences Fondamentales et Appliquées, Universitéd''Orléans, and Centre de Recherche sur la Physique des Hautes Temperatures, Centre National de la Recherche Scientifique, 45045 OrléansCedex, France;Laboratoire des Eléments de Transition dans les Solides, E.R. 60210, Centre National de la Recherche Scientifique, 1 Place A. Briand, 92140 Meudon-Bellevue, France |
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Abstract: | At room temperature and for x0 ~ 0.43, the system Sm1?xLaxAlO3 undergoes a first order phase transition in which an orthorhombic structure transforms into a rhomboedral structure as x increases. This phase transition was investigated by Raman scattering experiments on polycrystalline compounds in the range 0 ? x ? 1. The dependence of low frequency modes on x is reported and compared with their well known temperature dependence. Soft modes have been observed in the orthorhombic (D2h16) and rhomboedral (D3d6) phases. It was found that the first order phase transition is probably driven by a double degenerate mode whose two components in the low symmetry phase display a linear composition dependence of their squared frequencies. The source of anomalous behaviour of Raman bands near the phase transition is discussed. |
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