Acoustic anomalies at phase transformation to quasi-2D proton glass state in Cs5H3(SO4)(4) x xH(2)O crystal

Citation
Sn. Gvasaliya et al., Acoustic anomalies at phase transformation to quasi-2D proton glass state in Cs5H3(SO4)(4) x xH(2)O crystal, J PHYS-COND, 13(15), 2001, pp. 3677-3688
Citations number
34
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF PHYSICS-CONDENSED MATTER
ISSN journal
09538984 → ACNP
Volume
13
Issue
15
Year of publication
2001
Pages
3677 - 3688
Database
ISI
SICI code
0953-8984(20010416)13:15<3677:AAAPTT>2.0.ZU;2-Q
Abstract
The paper describes Brillouin light scattering studies of longitudinal acou stic (LA) phonons in Cs5H3(SO4)(4) X xH(2)O (PCHS) crystals at temperatures from 100 K to 360 K. The acoustic response of the cn stal at different fre quencies is analysed in detail. It is shown that both the velocity and damp ing of sound exhibit a strong dispersion caused by relaxation processes in the region of transformation into the glass-like phase (T-g approximate to 260 K). A strong anisotropy in the acoustic response, attributable to the q uasi-two dimensional (quasi-2D) structure of PCHS, is revealed. The LA phon on damping is calculated in the framework of a number of relaxation models. It is shown that, in the vicinity of T-g, anomalies in ultrasonic damping of the LA phonons propagating in the basal plane reflect the cooperative ef fect of freezing of acid protons. At the same time, the anomaly in damping of the LA phonon propagating perpendicular to the basal plane Is described in terms of the Debye model and is due to the interaction between protons o n hydrogen bonds and LA phonons. This suggests that the proton glass state realized at T < T-g is of quasi-2D nature.