A. C. Calorimetric Investigations of Specific Heat Anomaly in Ferroelectric TGSe

The specific heat of triglycine selenate was investigated with an a.c. calorimetry technique in the temperature range -170°C to +90°C including the Curie point at 22°C. A λ-type anomaly with a sharp peak at T c was seen in the range about -60°C to T c . The plateau region reported by Strukov et al. was not observed. The specific heat curve below T c was fitted very well with a mean-field theory of an Ising-dipole system which took into account the effect of lattice distortion. A parameter Δ which describes the strain dependence of the interaction energy was determined to be 0.303<Δ<0.324, indicating that the transition is of the second order and very close to the Curie critical one which occurs when Δ=1/3. A slight excess specific heat with logarithmic temperature dependence was observed in the paraelectric phase within \(T-Tc{}10\) K. This anomaly is considered to be due to the critical fluctuation.