THERMAL HISTORY AND DIELECTRIC BEHAVIOR OF [N(CH3)4]2ZNCL4 AT THE INCOMMENSURATE-COMMENSURATE PHASE-TRANSITION

Thermal hysteresis and memory effects near the lock-in transition of [N(CH3)4]2ZnCl4 are investigated by means of dielectric susceptibility measurements. The general kinetic behaviour of this material differs considerably from the one observed in the isomorphous compound [N(CH3)4]2CoCl4. Relaxation of the dielectric susceptibility is detected on the cooling runs when a sample is annealed in the incommensurate phase. As a consequence, thermal hysteresis loops cannot be constructed. Memory effects show similar features when annealings are performed at the incommensurate phase on the cooling curve or at the commensurate ferroelectric phase. In contrast, no memory effect could be created by annealing on the heating curve at the incommensurate phase. © 1990.