Ferroelectric Domain Wall Motion Research Articles

A continuum analysis of charge induced ferroelectric domain wall motions

A continuum model is presented for the motion of a domain wall in a plane 90°-domain configuration subjected to an isolated extrinsic charge near the surface of a ferroelectric single crystal. Local pinning is postulated for the kinetic law. Before the appearance of the extrinsic charge, all polarization surface charges are taken to be neutralized by environmental charges. The domain wall motion after the appearance of the extrinsic charge is assumed to proceed sufficiently fast without any significant conductive currents on the surface or in the interior of the crystal such that new surface and interface polarization charges remain unscreened and contribute to the ferroelectric anisotropy energy. A non-admissible divergence of the electric field and consequently of the local thermodynamic driving force and of the domain wall velocity appears in the model if the domain wall charged by interface polarization charges intersects the crystal surface charged by surface polarization charges under an arbitrary angle. The physically possible domain wall angle is identified using the condition of a non-divergent driving force. The ferroelectric anisotropy energy and an intrinsic surface energy of the domain wall, however, do not provide stability of the domain wall trajectory against an unlimited increase of its curvature at the surface. The problem has been solved conceptually by proper account of the domain wall bending energy. Numerical and dimensional analysis explain also why domain walls driven by extrinsic charges remain almost straight in soft ferroelectrics.

Domain wall creep in mixed c-a axis Pb(Zr0.2Ti0.8)O3 thin films

Creep motion of ferroelectric domain walls in epitaxial Pb(Zr0.2Ti0.8)O3 thin films was studied by atomic force microscopy. The dynamical exponent μ was found to be smaller than in previous reports, with values significantly lower than 1 observed in samples with a-axis inclusions.

Domain wall creep in mixed c‐a axis Pb(Zr0.2Ti0.8)O3 thin films

AbstractCreep motion of ferroelectric domain walls in epitaxial Pb(Zr0.2Ti0.8)O3 thin films was studied by atomic force microscopy. The dynamical exponent μ was found to be smaller than in previous reports, with values significantly lower than 1 observed in samples with a‐axis inclusions.

Novel effects observed in heavy ion irradiated Bi2Sr2-xLaxCuOy thin films

Creep motion of ferroelectric domain walls in epitaxial Pb(Zr0.2Ti0.8)O3 thin films was studied by atomic force microscopy. The dynamical exponent μ was found to be smaller than in previous reports, with values significantly lower than 1 observed in samples with a-axis inclusions.

Forward motion of ferroelectric domain walls

A theory is presented for the forward growth of ferroelectric domains taking place during polarization reversal. A faster forward motion in comparison with a sidewise motion is explained in terms of forces arising from the depolarization field of the growing domain. Dynamic equations for the time dependence of the domain length and radius are derived and solved. The calculation shows that in a strong electric field the forward velocity of the domain in barium titanate exceeds the lateral velocity by a large factor. This explains the observed rapid growth of new domains throughout the sample thickness without significant changes in their lateral sizes.

Dielectric Relaxation Processes in Relaxor Ferroelectric Cd 2 Nb 2 O 7 Modified with Ni 2+ or Cu 2+

The weak-field dielectric dispersion studies (100 Hz-13 MHz, 100 K < T < 300 K) of pyrochlore relaxor ferroelectric Cd 2 Nb 2 O 7 modified with Ni 2+ or Cu 2+ on the Cd 2+ site (at x = 0.02, 0.1, and 0.2) are presented and discussed. With increasing x, a relaxor behaviour of the system is manifested at higher temperature (around T C = 196 K and above). Around T C, the dielectric absorption spectra and relaxation-time distribution exhibit developing of two LF dielectric relaxation processes, in addition to ferroelectric domain wall motions: non-Debye relaxation typical of relaxors and Debye-like relaxation of quasi-isolated dipoles. The order parameter characterizing a deviation from Curie-Weiss dielectric behaviour in relaxors is nonzero up to ∼280 K, much higher than T C . The role of disorder on the Cd 2+ -site caused by randomly distributed off-center Ni or Cu ions (at x S 0.1) is discussed.

Barkhausen Jumps During Domain Wall Motion in Ferroelectrics

Noise component of switching current has been recorded during polarization reversal by domain wall motion in single-crystalline gadolinium molybdate (GMO) and lithium tantalate (LT) with various types of controlled domain structure. Simultaneously the domain kinetics has been optically visualized. The probability distribution of duration, area and energy of individual Barkhausen pulses demonstrates the critical behavior typical for the fractal records in time. Obtained power spectrum is typical for Flicker-noise and demonstrates the self-organized behavior. We classify the noise types at switching stages and show its relation to the wall interactions with pinning centers.

2–5 pyrochlore relaxor ferroelectric Cd2Nb2O7 and its Fe2+/Fe3+ modifications

The weak-field dielectric dispersion (100 Hz–1.8 GHz) studies both of pure and Fe2+/Fe3 modified Cd2Nb2O7 ceramics over the temperature range of 90–380 K are presented and discussed from the viewpoint of relaxor and glassy properties of the system. It is revealed that Cd2Nb2O7 pyrochlore is intolerant of the addition of 25 mol % Fe2+ or Fe3+ for Cd2+. From the x-ray diffraction analysis, pure Cd2Nb2O7 forms a single-phase pyrochlore, while the compositions Cd1.5Fe0.52+Nb2O7 and Cd1.5Fe0.53+Nb2O7 give CdNb2O6 columbite doped with Fe2+ or Fe3+ on the Cd sites (&amp;lt;8 and &amp;lt;2 mol %, respectively), except for minor amount of parasitic hematite. The novel CdNb2O6 type compounds are not ferroelectrics, unlike Cd2Nb2O7. In the latter, at TC=196 K the dielectric relaxation due to the motion of ferroelectric domain walls driven by an external ac electric field is observed. A polydispersive dielectric response of Cd2Nb2O7 around 188 K has characteristics of the relaxor ferroelectrics with glassy behavior (like PMN). Near the characteristic freezing temperature of the zero-field-cooled state (Tf=183 K) the dielectric absorption spectra and the relaxation-time distribution strongly broaden and tend to flatten out, while below Tf the imaginary part of the dielectric permittivity becomes nearly frequency independent. The dielectric response of Cd2Nb2O7 dominating far below TC (around 150 K) and that of Fe2+/Fe3+ doped CdNb2O6 between 90 and 380 K are typical of glass-forming systems at temperature far above Tglass. The relaxational process is characterized by (i) a significant frequency dependence of the peak permittivity position, (ii) non-Arrhenius behavior, and (iii) increasing asymmetry of the dielectric absorption spectrum at the low-frequency side with decreasing temperature, without broadening the relaxation-time distribution and freezing the peak-absorption frequency. It is proposed that although the nature of structural disorder in Cd2Nb2O7 pyrochlore and Fe2+/Fe3+ doped CdNb2O6 columbite is different, in both systems the off-center displacements of the A-site ions act as a random field and are responsible for the relaxor and dipolar glass-like behavior upon cooling. The Debye-like HF dielectric relaxation (1 MHz–1.8 GHz) observed both in Cd2Nb2O7 and its isostructural analog Cd2Ta2O7 at RT and higher (a centrosymmetric phase) is attributed to fluctuations in polarization of the dynamically reoriented O(7th)–Cd–O(7th) dipoles due to dynamical off-center location of Cd ions.

Aging and other related phenomena in potassium niobo-tantalate crystalsstudied through the frequency dependence of their dielectricconstant

We report on dielectric measurements in the frequency range from 1 to 1000 kHzin two disordered ferroelectric KTa1-yNbyO3 (KTN) crystals(y≅0.02). We have studied the frequency dependence of the dielectricconstant (real and imaginary parts) during several thermal evolutions:isothermal aging, rejuvenation by cooling or heating after a temperatureplateau, memory. In every case the frequency dependence is well described by apower law. The temperature and plateau duration dependences of the exponentshave been studied. We give a description of our results within a model wherethe variations of the dielectric constant are attributed to the motion (growthand reconformation) of ferroelectric domain walls. In particular we are ableto explain the identity of the exponents of the frequency power law dependenceof memory and isothermal aging.

Optical, elastic, and dielectric studies of the phase transitions in lawsonite

Results of optical birefringence, ultralow-frequency elastic, dilatometric, and dielectric measurements of lawsonite crystals are presented in a wide temperature range including two successive phase transitions $\mathrm{Cmcm}\ensuremath{-}{(T}_{1}=273 \mathrm{K})\ensuremath{\rightarrow}\mathrm{Pmcn}\ensuremath{-}{(T}_{2}=120 \mathrm{K})\ensuremath{\rightarrow}{P2}_{1}\mathrm{cn}.$ Pronounced pretransitional effects are observed in macroscopic properties in a large temperature region $(\ensuremath{\approx}200 \mathrm{K})$ above ${T}_{1}.$ The low-temperature transition at ${T}_{2}=120 \mathrm{K}$ is found to be proper ferroelectric. A deviation from the Curie-Weiss law appears in the temperature dependence of the dielectric susceptibility in the region of the ferroelectric transition below ${T}_{2}.$ Frequency dependent measurements of the dielectric permittivity yield evidence that ferroelectric domain-wall motion is responsible for this deviation from the standard behavior.

Effect of PbO Content on Dielectric and Electric Field Induced Strain Properties in Y-Modified Lead Zirconate Titanate Stannate

The dielectric and field induced strain properties of the antiferroelectric–ferroelectric phase boundary (y = 0.085) and the ferroelectric (y = 0.12) compositions in the Pb 0.97Y 0.02[(Zr 0.6Sn 0.4) 1-yTi y]O 3 system have been investigated as a function of excess PbO in the range of 0–5 mol%. The y = 0.085 specimen showed that the double hysteresis loops of the antiferroelectric phase and its transition field (E A↔F) of the antiferroelectric–ferroelectric phase transition increased with the increase of excess PbO. The y = 0.12 specimen showed that the typical ferroelectric hysteresis loop, due to the stable ferroelectric phase and its coercive field, increased due to inhibition of the ferroelectric domain wall motion as the amount of excess PbO increased. The shape memory effect of strain in the y = 0.085 specimen disappeared above 3 mol% of excess PbO. The y = 0.12 specimen maintained the butterfly-type strain curve through the entire range of excess PbO additions. The maximum strain of the y = 0.085 specimen with no excess PbO was about 4 × 10 −3, and it decreased to about 2 × 10 −3 with the addition of 5 mol% excess PbO.

Anomalies of ferroelectric domain wall motion near the transition point

Optical measurements of the individual ferroelectric/ferroelastic domain wall oscillations in the ac electric field were carried out up to the transition temperature. The amplitude of the wall vibrations fell abruptly to zero so that the wall was at rest during the phase transition. The change of oscillation characteristics with temperature is shown to be dependent on the history of motion, in part on the initial amplitude and the presence of the shell of mobile defects or charge carriers. Change of material parameters, influence of screening or defects shell, and critical damping are discussed as possible mechanisms of the effect. The last assumption is shown to be in a good agreement with the experimental data. The measurements of the amplitude of domain wall vibrations may be used as a simple method for investigations on critical phenomena in ferroelectrics.

The ferroelectric and proton glass coexistence region in K0.77(NH4)0.23H2AsO4 detected by complex permittivity measurements

This paper reports results of the studies on complex permittivity epsilon *= epsilon '-i epsilon " in a mixed K0.77(NH4)0.23H2ASO4 crystal. Measurements along the crystallographic a axis have clearly indicated the coexistence of the ferroelectric state and proton glass state in this crystal. The temperature dependence of epsilon 'a shows a maximum at Tc=61 K, indicating a ferroelectric transition, while the dispersion of epsilon 'a and epsilon a" below T=40 K satisfies the Vogel-Fulcher equation with the parameters T0=8.3 K, Ec=183.5 K and nu c=1.65*1011 Hz, which proves the presence of the proton glass state. Analysis of the shape of the temperature dependence of dielectric losses epsilon c"( nu ,T) observed in the measurements along the ferroelectric c axis revealed the presence of Another process of relaxation apart from that related to the freezing of ferroelectric domain wall motion known for KDP type crystals. The two relaxation processes are also described by the Vogel-Fulcher equation with the parameters T01=34 K, Ecl=7.7 K and nu cl=6.8*105 Hz for one of them and for the other T02=20.5 K, Ec2=13.4 K and nu c2=5.6*106 Hz. Our results prove the coexistence of the ferroelectric and proton glass states in the K0.77(NH4)0.23H2AsO4 crystal, and the occurrence of different kinds of cluster of local ordering (proton glass and relaxer clusters) and ferroelectric domains.

Electron microscopy study of ferroelastic and ferroelectric domain wall motions induced by thein situapplication of an electric field in BaTiO3

Abstract We have built a new TEM heating stage permitting the in situ application of an electric field on sample surfaces and have performed experiments on ferroelectric domain switching in BaTiO3. The domain growth induced by the electric field first occurs by domain tip motion and then by the lateral shift of walls. A memory effect due to the localization of defects along the domain boundaries has been observed.

Ferroelectric domain wall motion and related internal friction in TGS crystal

On etudie le mouvement des parois de domaines ferroelectriques dans un cristal TGS dans lequel la transition de phase ordre-desordre ferroelectrique du second ordre prend place a la temperature de Curie

Dielectric and piezoelectric properties of modified lead titanate zirconate ceramics from 4.2 to 300 K

The dielectric and piezoelectric properties (d-p properties) of four kinds of doped lead titanate zirconate piezoelectric ceramics (PZTs) have been measured from 4.2 to 300 K. The d-p properties of the materials converge with decreasing temperature down to liquid helium temperature, even though the properties have large differences at room temperatue. The values of mechanical and electrical quality factors,Q m,Q e, and of the frequency constant,N, of the materials increased at low temperature. It is evident from the freeze out inK′ and the associate temperature: frequency-dependent maxima in tan 5 that the relaxation processes including ferroelectric domain wall motion and thermal defect motion contribute to the d-p properties. The Navy type-III composition has a minimum temperature coefficient of d-p parameters and it is evident that PZT ceramics modified with Fe2O3 can provide good stability and also give the strongest piezoelectric response at liquid helium temperature.

A single mechanism for slow domain wall motion in both ferroelectrics and ferromagnets

A tunneling theory of slow wall motion in ferromagnets is applied to BaTiO3 using the data of Miller and Savage. It is shown that, over seven decades of velocity for which the approximations are valid and for which data are available, the theory fits the data well and even gives the appreciable change of slope in the lnu -versus-l/E plot found experimentally. A material will or will not behave as though it had a true coercive force, below which wall motion does not occur, depending on whether a quantity called Z* is large or small, respectively. Z* is the average range of pinning centers in the crystal, normalized to the (approximate) tunneling length. For BaTiO3 it was determined that Z*=6; u0, a characteristic tunneling velocity, was 2.72 cm/s; Ec, the classical coercive field, was 763 V/cm. It is concluded that domain wall motion in ferromagnets and ferroelectrics proceeds by the same mechanism.

On the preparation, properties, and possible ferroelectricity in SbI 5

Two methods have been described for the growth of single crystals of SbSI. This paper reports that one method produces not SbSI, but SbI 5. The stoichiometry was checked by chemical analysis. The interplanar spacing obtained by X-ray diffraction is in agreement with a close-packed structure similar to that reported for SbCl 5. Optical studies reveal a domain structure. Application of electric fields produces changes in extinction area. This effect may be evidence for ferroelectric domain wall motion, but electrostrictive effects could not be ruled out.

Die Auswirkung des eingepr�gten Nachwirkungsfeldes auf die Bewegung ferroelektrischer Dom�nenw�nde in Seignettesalzkristallen

Dielectric dispersions at low and audio frequencies and ferroelectric after effects in Rochelle Salt are due to ordering of point defects as recently has been shown byUnruh and the author. It is possible to describe all these effects in terms of an intrinsic electric field. This paper deals with the influence of the intrinsic field on the motion of ferroelectric domain walls. Preliminary measurements are consistent with the conception of the intrinsic field, but some details are to understand only by the assumption of permanent imperfections of the crystals.

Dielectric properties of boracites and evidence for ferroelectricity

The dielectric constants of Ni-Cl, Ni-Br, Co-Br and Co-I boracites have each a maximum at a temperature which coincides with that of a phase transformation we have observed optically. Motion of ferroelectric domain walls under an applied electric field has been sought for in Ni-Cl boracite and found to occur at temperatures as far as 80° below that of the phase transition.