Brillouin scattering in incommensurate Rb/sub 2/ZnBr/sub 4/ and Rb/sub 2/ZnCl/sub 4/

Journal Article · Wed Mar 15 04:00:00 EST 1989 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.39.5726· OSTI ID:6482000

Horikx, J J.L.; Arts, A F.M.; Dijkhuis, J I; de Wijn, H W

In Rb/sub 2/ZnBr/sub 4/ and Rb/sub 2/ZnCl/sub 4/, Brillouin scattering of longitudinal-acoustic phonons is performed as a function of the temperature. Small anomalies, arising through a coupling with the soft-going modes, are observed in both the phonon velocity and damping near the transition from the orthorhombic to the modulated phase. The anomalies are quantitatively accounted for with a comprehensive analysis based on an adaptation of Levanyuk's Landau theory for sound absorption near second-order phase transitions. In the incommensurate regime, two mechanisms appear to contribute by about equal weights: an effective coupling bilinear in the strain and amplitude fluctuations, and a coupling linear in the strain, but quadratic in the amplitude fluctuations. Above the transition, the soft-mode counterpart of the latter coupling remains. Estimates of these contributions derived from the theory with parameter values from other sources are found to be in conformity with the experiment. The analysis further yields the amplitude-mode and soft-mode relaxation times as well as the transition temperatures. Additionally, the anomalous phonon velocity and damping observed in Rb/sub 2/ZnBr/sub 4/ near a transition at 115 K are analyzed. Finally, the elastic constants of Rb/sub 2/ZnBr/sub 4/ and Rb/sub 2/ZnCl/sub 4/ are determined at 300 K.

• Research Organization: Fysisch Laboratorium, Rijksuniversiteit Utrecht, P.O. Box 80 000, 3508 TA Utrecht, The Netherlands
• OSTI ID: 6482000
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 39:9; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360604* -- Materials-- Corrosion
Erosion
& Degradation
ALKALI METAL COMPOUNDS
BRILLOUIN EFFECT
BROMIDES
BROMINE COMPOUNDS
CHLORIDES
CHLORINE COMPOUNDS
COHERENT SCATTERING
HALIDES
HALOGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RELAXATION TIME
RUBIDIUM BROMIDES
RUBIDIUM CHLORIDES
RUBIDIUM COMPOUNDS
SCATTERING
SPECTROSCOPY
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
ZINC BROMIDES
ZINC CHLORIDES
ZINC COMPOUNDS
ZINC HALIDES