Brillouin light scattering anomalies and new phase transition in Cs5H3(SO4)4 crystals
Lushnikov, Sergey G.
Shuvalov, L. A.
Dolbinina, V. V.
Schmidt, V. Hugo
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The behavior of hypersonic longitudinal acoustic phonons at temperatures ranging from 290 to 370 K in a crystal of Cs5H3(SO4)4·nH2O was studied by Brillouin light scattering. Anomalies in the temperature dependences of the frequency shift and spectral width of the Brillouin components in the vicinity of T=360K were observed. We found a “point of isotropization” near 360 K where C11=C33=2.6X10 10 N/m2 We attribute it to an isostructural phase transition from P63/mmc⇔P63/mmc where the apparent acoustic symmetry changes from hexagonal to cubic. Possible models for the phase transition have been discussed.
S.G. Lushnikov, V.H. Schmidt, L.A. Shuvalov, and V.V. Dolbinina, “Brillouin light scattering anomalies and new phase transition in Cs5H3(SO4)4 crystals,” Solid State Commun. 113, 639-642 (2000).