Relaxor Ferroelectrics: Back to the Single-Soft-Mode Picture. Auteur(s): Hehlen B., Al Majzoub Al Sabbagh M., Al-Zein A., Hlinka J (Article) Publié: Physical Review Letters, vol. 117 p.155501 (2016) Texte intégral en Openaccess : Ref HAL: hal-01388588_v1 PMID 27768376 DOI: 10.1103/PhysRevLett.117.155501 WoS: 000385341900016 Exporter : BibTex | endNote 15 Citations Résumé: The fluctuations of electric polarization in a disordered ferroelectric substance, relaxor crystal PbMg_{1/3}Nb_{2/3}O_{3} (PMN), were studied using a nonlinear inelastic light-scattering technique, hyper-Raman scattering, within a 5-100 cm^{-1} spectral interval and in a broad temperature range from 20 to 900 K. The split ferroelectric mode reveals a local anisotropy of up to about 400 K. Spectral anomalies observed at higher temperatures are explained as due to avoided crossing of the single primary polar soft mode with a temperature-independent, nonpolar spectral feature near 45 cm^{-1}, known from Raman scattering. The temperature changes of the vibrational modes involved in the measured fluctuation spectra of PMN were captured in a simple model that accounts for the temperature dependence of the dielectric permittivity as well. The observed slowing down of the relaxational dynamics directly correlates with the huge increase of the dielectric permittivity. |