Specific Features of Brillouin Spectra at a High-Temperature Phase Transition in Cs5H3(SO4)4xnH2O Crystals
This paper presents detailed Brillouin light scattering studies of the acoustic response of a Cs5H3(SO4)4xnH2O (PCHS) crystal in the vicinity of a superionic (superprotonic) structural phase transition of the first order. Just above the phase transition, splitting of the Brillouin doublet is observed. The ‘two-mode’ behavior of the longitudinal acoustic phonon can be explained by coexistence of phases at a structural phase transition of the first order. Above the phase transition, in the superionic phase, an additional doublet forbidden by the selection rules appears in a narrow temperature interval. It is concluded that an anomalous behavior of Brillouin light scattering can be attributed to the influence of dynamically disordered protons on the phonon subsystem.
B.M. Darinskii and L.B. Magalas
A.I. Fedoseev et al., "Specific Features of Brillouin Spectra at a High-Temperature Phase Transition in Cs5H3(SO4)4xnH2O Crystals", Solid State Phenomena, Vol. 115, pp. 279-284, 2006