Relaxation of the domain structure in doped triglycine sulfate crystals in an internal field

This paper reports on the results of an investigation into the relaxation of the domain structure of triglycine sulfate ferroelectric crystals from a nonequilibrium state induced by rapid cooling of the sample through the phase transition point, in response to an external electric field, and under thermal annealing. The role played by the internal field in the processes of relaxation of the domain structure to the equilibrium state in defect-containing triglycine sulfate crystals is elucidated.     

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 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.     

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.     

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.     

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.     

Relaxation stimulated in the domain structure of a triglycine sulfate crystal by an alternating-current electric field

The relaxation of the domain structure in a triglycine sulfate crystal from a nonequilibrium state induced by an alternating-current electric field has been investigated. The distributions of the activation energy of the processes under consideration and the energy of interaction of domain walls with defects over the exciting fields have been obtained.     

Temperature and time behavior of the parameters of the domain structure of triglycine sulfate crystals near the phase transition

This paper reports on the results of the investigation into the temperature and time behavior of the parameters of the domain structure in nominally pure and doped (??-alanine, chromium, phosphorus) triglycine sulfate crystals, which has been revealed by piezoresponse force microscopy during observation of the domain structure. The relaxation time dependences on the total perimeter of the domain walls, the velocity of lateral domain-wall motion, and the coefficient of static unipolarity have been obtained using computer image processing of the domain structure of the crystals under investigation. The temperature dependences of these parameters near the Curie temperature have been found. A comparison with the data available in the literature has been made, as well as with the results of our measurements of the permittivity for the same samples and under the same temperature-time conditions.     

Relaxation of radiative defects in irradiated triglycine sulfate

Nonmonotonic temporal behavior of the temperature dependence of the conductivity of ferroelectric triglycine sulfate is observed after its irradiation by small doses of x radiation. Such behavior is associated primarily with the formation of two types of radiation defects having different lifetimes. Fiz. Tverd. Tela (St. Petersburg) 40, 116–117 (January 1998)     

Relaxation of static photoelasticity in triglycine fluoroberyllate crystals

The relaxation of the static photoelasticity in triglycine fluoroberyllate crystals has been studied. The anisotropy of the relaxation amplitudes and their anomalies near the phase transition have been revealed. The photoelastic relaxations and peculiarities of their temperature behavior have been explained in terms of the piezocaloric mechanism.     

Relaxation of the nonequilibrium domain structure in TGS and TGSP crystals

The relaxation behavior of the nonequilibrium domain structure in nominally pure triglycine sulphate and triglycine sulphate doped with phosphorus has been investigated. A significant difference in the state of the domain structure formed as a result of slow and rapid cooling of crystals into the ferroelectric phase has been found.     

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.     

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.     

Simulation of the dynamics of the spatial domain structure of a ferroelectric triglycine sulfate crystal

The dynamics of a domain structure of order-disorder ferroelectrics similar to triglycine sulfate is considered. Starting from the Hamiltonian of the problem, a kinetic equation describing the polarization dynamics of ferroelectrics is derived. The results are analyzed and compared with the experimental data.     

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)     

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.