Dielectric relaxation in deuterated triglycine sulfate crystals

A study has been made of the slow relaxation of the dielectric permittivity of deuterated triglycine sulfate (DTGS) initiated by application of a dc electric field. The field and temperature dependences of the relaxation time associated with domain-wall motion were obtained. The effect of the internal electric field on relaxation processes is seen in different behavior of the field and temperature dependences under different orientations of the external field. The existence in DTGS crystals of two temperature regions of domain-structure rearrangement lying 7–8 and 15–18 °C below the Curie point has been established. Fiz. Tverd. Tela (St. Petersburg) 40, 1542–1545 (August 1998)     

Polarization switching of triglycine sulfate and deuterated triglycine sulfate single crystals irradiated with a high-current pulsed electron beam

The influence of high-current pulsed electron beams on the processes of polarization switching in triglycine sulfate and deuterated triglycine sulfate single crystals is investigated using the Barkhausen effect.     

Relaxation of the domain structure in triglycine sulfate and deuterated triglycine sulfate crystals in the course of polarization switching

Relaxation of the domain structure in triglycine sulfate and deuterated triglycine sulfate crystals is investigated using polarization switching (during which the domain structure is disturbed from an equilibrium state by a dc electric field) over a wide range of temperatures.     

Relaxation of piezobirefringence in triglycine sulfate crystals

The effect of photoelastic relaxation is investigated using triglycine sulfate ferroelectric crystals as an example. The optical and deformation contributions to the photoelastic relaxation are described, and their percentage in the combined effect is determined. Consideration is given to the temperature dependences of the relaxation amplitudes of the path difference and birefringence, which are induced by mechanical stress.     

Specific heat and electrical conductivity of deuterated triglycine selenate single crystals

Measurements of the specific heat were carried out on deuterated trigylcine selenate (DTGSe) single crystals to clarify its critical nature near the ferroelectric transition point (T_c ). The results obtained have indicated that DTGSe crystals deuterated by 90% exhibit a first-order phase transition.

This paper presents also the electrical conductivity (δ) of DTGSe crystals. The deuterium substitution induces an increase in the Curie point T_c , and a decrease in the conductivity in the para- and ferroelectric phases accompanied by an increase in the activation energy (W) in both phases.     

Magnetic memory effects in triglycine sulfate ferroelectric crystals

The effect of a magnetic field on the processes of relaxation of the defect structure relaxation in a triglycine sulfate (TGS) ferroelectric (nonmagnetic) crystal has been observed for the first time. The atomic-force microscopy study has shown that the application of a static weak magnetic field (2 T, 20 min) significantly changes the size distribution of defect nanoclusters characteristic of TGS. Previously known macroscopic aftereffects of the magnetic field in TGS (slow relaxation of the dielectric susceptibility, symmetrization of P–E dielectric hysteresis loops, etc.) can be explained by the redistribution of pinning centers of domain walls caused by the magnetically induced reconfiguration of the defect structure.     

Chaotic behavior of triglycine sulfate crystals containing radiation defects

The temperature-amplitude region of existence of chaotic oscillations in a resonant circuit containing a triglycine sulfate crystal shifts toward higher amplitudes of the repolarization field when the crystal is irradiated with small x-ray doses. This trend is attributed to a change in the kinetics of the domain structure of the crystal in a strong electric field in the presence of radiation defects. Fiz. Tverd. Tela (St. Petersburg) 40, 716–718 (April 1998)     

Barkhausen jumps and switching current in triglycine sulfate crystals

The slow processes involved in establishment of the overall and discontinuous parts of the polarization of a triglycine sulfate crystal are compared on the basis of a joint study of the switching current and the Barkhausen jumps. Over a wide field range (10–10³ V/cm) the time required to establish the entire polarization is equal to the time required to establish its irreversible part due to jumps. The time dependences of the overall and discontinuous parts of the polarization are shown to be analogous. There is a threshold field above which the discontinuous repolarization processes play a decreasing role with increasing field.     

Influence of weak pulsed magnetic fields on triglycine sulfate crystals

The influence of weak (≤0.02 T) pulsed magnetic fields on the ferroelectric and dielectric characteristics of nominally pure triglycine sulfate crystals was detected for the first time. A short-term (seconds) pulsed magnetic impact caused long-term (hundreds of hours) changes in the coercive field and the temperature dependences of the dielectric constant, the dissipation factor, and the relaxation time of the dielectric constant near the ferroelectric phase transition. It was assumed that the effects detected were caused by unpinning of domain walls and dislocations from stoppers, followed by the formation of new defect and domain structures.     

Comparative study of the effect of low-dose gamma irradiation on phase transitions in single crystals of triglycine sulfate and its deuterated analog

The effect of low γ-radiation doses (< 0.5 MR) on the specific heat C _p of crystals of triglycine sulfate and its deuterated analog was studied using precision vacuum adiabatic calorimetry in the temperature range 80–350 K. Appreciable changes in the behavior of C _p of nominally pure and γ-irradiated crystals were detected near the phase transition temperature (T _c ), which decreased as the dose was lowered.     

Acoustic emission upon spontaneous polarization in triglycine sulfate single crystals

We report on the results of analysis of acoustic emission (AE) under thermal action on a triglycine sulfate (NH₂CH₂COOH)₃ ? H₂SO₄ crystal. The triglycine sulfate single crystals grown from solution and not subjected to mechanical treatment are heated to a temperature above the Curie point (T_C = 49°C). During natural cooling of the crystal, a transition from the paraelectric to ferroelectric phase is accompanied by intense AE. In the temperature range ～28–30°C, an anomalous drop of the mean-square voltage in the AE signal is observed against the background of monotonic accumulation of AE events.     

Ferroelectric properties of doped triglycine sulfate crystals grown at negative temperatures

The effect of Cr³⁺ impurity ions on the dielectric and pyroelectric properties of triglycine sulfate crystals grown at temperatures below 0°C is studied. The Curie temperature T _C of the chromium-containing crystals is 0.2–0.4°C lower than that of the impurity-free crystals grown at conventional temperatures. A stable reproducibility of the results of the pyroelectric measurements for the crystals studied is established, which indicates that the polar state in crystals is stabilized by growth defects.     

Threshold behavior of the dielectric nonlinearity in ferroelectric crystals of triglycine sulfate

The threshold behavior of the effective permittivity and harmonic amplitudes of the polarization switching-current spectrum is studied for triglycine-sulfate crystals with various defects as a function of the ac electric field amplitude. The interaction energies are calculated for domain walls with defects. The relaxation behavior of the effective permittivity at a constant amplitude of the switching field is studied.     

Selective effect of a weak DC magnetic field on triglycine sulfate crystals

The effect of the selective influence of a dc magnetic field on the characteristics of nominally pure triglycine sulfate crystals was detected for the first time. A short (minutes) exposure to a weak magnetic field B₀=0.08±0.01 T caused long-term (hundreds of hours) changes in the spontaneous polarization, coercive field, Curie temperature, and permittivity of the crystal at the Curie point. The effect is selective in nature presumably because of the participation of hydrogen bond protons in the spin-dependent processes of the transformation of defect complexes in real crystals.     

Rearrangement of the domain structure of cobalt- and chromium-doped triglycine sulfate crystals

The paper reports the results of studies of repolarization and rearrangement of the domain structure of triglycine sulfate (TGS) crystals containing two impurities, cobalt and chromium. The introduction of these impurities hinders the repolarization of TGS crystals and causes their spontaneous polarization to decrease, the coercive field to increase, and displacement fields to form.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 63–66, April, 1991.     

Dielectric properties of single-crystal deuterated triglycine sulfate (DTGS) in ultra-weak low-and infra-low-frequency electric fields

The complex permittivity ɛ* is studied with separate readings for ɛ′ and ɛ″ at low and infralow frequencies and ultraweak fields. The effective conductivity λ is determined. An Arrhenius dependence is observed for ln ɛ′(1/T), ln ɛ″(1/T), and ln λ(1/T), both in the paraphase and in the polar phase. It is proposed that the conductivity of crystalline DTGS in the paraphase is an ion jump conductivity. Fiz. Tverd. Tela (St. Petersburg) 41, 1073–1075 (June 1999)