Effect of a Two-Dimensional Pressure on the Curie Points of Triglycine Sulphate and Rochelle Salt

Abstract

The effect of a two-dimensional pressure perpendicular to the ferroelectric axis on the Curie temperatures of triglycine sulphate (TGS) and Rochelle salt (RS) was studied. The Curie temperatures T c varied linearly with the pressure p within the pressure range studied ( p <100 bar). The rate of the T c shift was ∂ T c /∂ p =13±1 for TGS, ∂ T c /∂ p =-22±1 for the upper Curie point of RS and ∂ T c /∂ p =30±2 for the lower Curie point of RS, all in °C/k bar. These results agree with the predictions of the phenomenological theory (Ginzberg-Devonshire theory) and Janovec's theory (V. Janovec: J. chem. Phys. 45 (1966) 1874).