Departure from mean field critical behavior in ferroelectric DTGS

Abstract

Dielectric constant and hysteresis loops measurements have been performed in single crystals of deuterated triglycine sulfate (DTGS) in the vicinity of the transition temperature. In the range 0.02°C < Δ T < 0.60°C deviations from mean field behavior were observed. In the range 1°C < Δ T < 10°C the dielectric constant data fitted mean-field predictions fairly well. Using the experimental (non mean-field) values for the critical exponents in the temperature range closer to T c , the “scaling” equation of state h( x) = ( x 0 + x) β( δ-1) was seen to be fulfilled in a wide range of x = ( ΔT/ T c )/( P/ P 0) 1/ gb below and above T c . The same is true for TGS data, using classical values for the exponents.