Brillouin scattering study of the ferroelectric phase transition in tris-sarcosine calcium chloride
Schmidt, V. Hugo
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Brillouin spectra from longitudinal phonons in ferroelectric tris-sarcosine calcium chloride propagating along , , and  have been measured as functions of temperature. Large anomalies were found in the Brillouin shift and linewidth in the  and  phonons. These anomalies are interpreted as arising from the linear coupling of the polarization and the phonons. From the temperature where the linewidth is maximum, the relaxation time of the polarization fluctuations is estimated to be τ=3.1×10−12/(Tc-T) sec, where Tc is the ferroelectric transition temperature. We also observed anomalies in Brillouin shift and linewidth of the  phonons which propagate along the ferroelectric b axis. These anomalies are interpreted as coming from electro- strictive coupling. The energy-relaxation time was estimated to be τE=2.5×10−10/(T-Tc) sec in the paraelectric phase and τE=1.0×10−9/(Tc-T) sec in the ferroelectric phase, by comparing our Brillouin results with those of the ultrasonic measurements.
T. Hikita, P. Schnackenberg, and V.H. Schmidt, â€œBrillouin scattering study of the ferroelectric phase transition in tris-sarcosine calcium chloride,â€� Phys. Rev. B 31, 299-303 (1985)