Experimental Study of Antiferroelectric Copper Formate Tetrahydrate and Its Deuterium Substitute

TLDR: In this paper, the Curie-Weiss constant for dielectric constant above the transition is 3.1×10 4 °C in both H 2 O and HCOO 2 4D 2 O.

Abstract: Antiferroelectric properties of Cu(HCOO) 2 4H 2 O and Cu(HCOO) 2 4D 2 O were investigated experimentally. Dielectric constant as a function of temperature shows a behavior of the first order transition with a large discontinuity at the transition. The transition point is shifted from -37.7°C for hydrogenous crystal to -27.7°C by deuterium substitution. The Curie-Weiss constant for dielectric constant above the transition is 3.1×10 4 °C in both crystals. Typical double hysteresis loop was observed in the antiferroelectric phase under a pulsive sinusoidal electric field. From the double loops at various temperatures, critical field to induce a forced transition and spontaneous polarization of sublattice as function of temperature were obtained. The critical field shows a linear dependence on temperature and it stays finite at the transition point. The spontaneous polarization is almost constant of 6 µ coul/cm 2 and shows discontinuous vanishing at the transition point. This value agrees well to the calculat...