Soft-mode spectroscopy in cubic (Ba0.8Sr0.2)Ti-0.95(Zn1/3Nb2/3)(0.05)O-3 by hyper-Raman scattering and the mechanism of the phase transition - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Solid State Communications Année : 2016

Soft-mode spectroscopy in cubic (Ba0.8Sr0.2)Ti-0.95(Zn1/3Nb2/3)(0.05)O-3 by hyper-Raman scattering and the mechanism of the phase transition

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Résumé

This paper presents a survey of soft modes and their relationship to structural phase transitions. After introducing the concept of a soft mode, the origin of softening is considered from a lattice-dynamical point. The Landau theory approach to structural transitions is then discussed, followed by a generalization of the soft-mode concept through the use of the dynamic order-parameter susceptibility. The hyper-Raman spectra in the cubic phase of (Ba0.8Sr0.2)Ti-0.95(Zn1/3Nb2/3)(0.05)O-3 are studied with special emphasis on the lowest-frequency phonon mode. The spectral structure is found to change above the Curie temperature (303-873 K). Soft modes were put forward by Cochran and Anderson about 50 years ago as an explanation of structural phase transitions. Extending Landau's theory of phase transitions, their prediction was that the square of the frequency of the soft mode was proportional omega(0)(T)= C root T-T-C where T-c is the transition temperature.
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hal-03627585 , version 1 (01-04-2022)

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Dhifallah Nabil, Bernard Hehlen, Mimoun El Marssi, Dammak Mohamed, Hamadi Khemakhem. Soft-mode spectroscopy in cubic (Ba0.8Sr0.2)Ti-0.95(Zn1/3Nb2/3)(0.05)O-3 by hyper-Raman scattering and the mechanism of the phase transition. Solid State Communications, 2016, 248, pp.97-100. ⟨10.1016/j.ssc.2016.09.016⟩. ⟨hal-03627585⟩
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