Transverse field effect close to the critical point in the TGS ferroelectric

Abstract

International audienceA hysteresis loop was measured in a round plate sample of the triglycine sulphate (TGS) ferroelectric with two measurement and one side electrode. Due to a non-zero electric potential Vs applied to the side electrode the hysteresis loop gradually decayed on time. It has been shown that the higher the Vs value, the shorter time td is required for the hysteresis loop to disappear. The value of 1/td has turned out to be proportional to the electric potential Vs generating a transverse field at a constant temperature. Within the limits of experimental errors, the inverse of the slope of the dependence 1/td versus Vs is proportional to the difference Tc−T. A relation between the temperature T, the spontaneous polarization P+- (positive or negative) and the freezing parameter f has been proposed. The parameter f describes the influence of the transverse electric field. Arguments in favour of considering the transverse field effect as occurring due to free electric charges flowing into the crystal have been given. A method by means of which the parameters of the hysteresis loop can be easily adjusted by an electric potential of an additional side electrode has been proposed

Pyroelectric properties of the triglycine sulphate crystal formerly influenced by a transverse electric field

“…During hysteresis loop measurements, a ground referenced electric side potential V s = 500.0 ± 0.5 V was connected to the side electrode, while at the same time, a sin waved driving electric field was continuously applied by means of the circular electrodes (c.f. Figure 3 of [3]). A gradual decrease of the hysteresis loop could be observed in the course of time of nearly three hours, as a result of the side potential application.…”

“…The Sawyer-Tower method was used [13] for the hysteresis loop detection. The measurement circuit and the apparatus were the same as those used in [3]. The amplitude and frequency of the driving electric field were 39.5 kVm −1 (estimated as 150 V/3.8 mm) and 100 Hz, respectively.…”

“…In fact, the hysteresis loop reduction or even its disappearance could be observed when, apart from the driving field applied by the electrodes covering the TGS cleavage surfaces, an electrical potential was additionally connected to a side electrode (side electrodes) attached perpendicularly to the measurement ones (e.g. [2,3]). A similar gradual flattening of the hysteresis loop and finally its disappearance in a transverse electric field was also observed in triglycine selenate (TGSe) [4] and in the Rochelle salt (RS) [5], that is in other uniaxial ferroelectrics.…”

“…It was assumed in [3] that 0 ≤ f ≤ f 0 , f increases as more and more electric charges flow through the sample during the transverse field application and f 0 decreases as temperature tends to the critical point:…”

“…According to the empirical formula given in [3], the spontaneous polarization of the crystal depends then on f:…”