Critical Behavior in Thermal Expansion Coefficient and Dielectric Constant of Triglycine Sulfate

Measurements of the thermal expansion coefficient and the dielectric constant have been made for the uniaxial ferroelectric triglycine sulfate (TGS) along the ferroelectric b -axis. Deviations from Landau-like behavior are observed in the vicinity of the critical temperature. Some attempts of logarithmic corrections to these results are made on the basis of the Larkin-Khmel'nitskii prediction. The parameters in the theory are determined by examining the dielectric constant for clamped crystal and the thermal expansion coefficient. Agreement between the theory and the present experiments are good over the temperature range \(T-Tc 3\) K in the paraelectric phase.