45° Brillouin Scattering Studies of the Anisotropic Polarization Relaxation Time in Triglycine Sulfate

The temperature dependence of the anisotropic polarization relaxation time τ(θ) has been studied in the b c -plane of the uniaxial ferroelectric TGS by the observation of the 45° Brillouin scattering spectra. The frequency shift and the linewidth of the Brillouin satellite show temperature dependent anisotropic anomalies in the ferroelectric phase. These anomalies are found to arise out of the depolarization effect on the polarization fluctuation. From the viewpoint of the polarization relaxation phenomena, the effect can be analyzed satisfactorily by τ(θ) with reasonable values of three parameters; dielectric susceptibilities along the b - and the c -axes, χ 22 x ( q // c )≃115( T c - T ) -1 and χ 33 x ≃0.8, and a relaxation time for a transverse polarization fluctuation τ(0)=4.2 ×10 -11 ( T c - T ) -1 sec.