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The concept of local ferroelectricity discussed in this paper belongs to the emerging field of ultrathin multiferroics. The idea of the ferroelectric polarization associated with the domain walls in magnets proposed by V.G. Bar'yakhtar et al. more than thirty years ago has recently got experimental evidence including electric field driven magnetic domain wall motion and electric field induced Stark shift in the single molecule microscopy. The special attention is paid here to the magnetoelectric properties of dislocation in stripe domain structure (i.e. the stripe domain heads) that differ considerably from the ones of straight domain wall segments. It is shown that the electric field induced displacement of the domain wall can be increased by an order of value with external constant magnetic field.

The coupling between the spatial modulation of the order parameter and the electric polarization, known as the flexoelectric effect in liquid crystals, appears in spin structures in the case of magnetic media. In this paper the various implications of spin flexoelectricity are reviewed including: magnetically induced electric polarization in magnets, electric field driven magnetic domain wall motion, tilting of the domain wall plane, and switching of domain wall chirality as well as the pinning of a magnetic domain wall at the ferroelectric one in multiferroics.

Shape of local hysteresis loops was studied by scanning probe microscopy using pulsed and in-field modes. Intermediate states on the loops measured in pulsed mode were revealed and explained by partial backswitching in the area under SPM tip. The obtained slope of the loops measured in the in-field mode was explained taking into account the interaction between two types of charges: induced in sample by switching voltage and in cantilever by modulation voltage. Dependence of loops slope on the position of the laser spot on the cantilever was found. Computer simulation was used for explanation of the observed data.

Self-assembled formation of dense structures of oriented domain rays under application of uniform electric field was studied in single crystalline lithium niobate wafers with surface layers modified by Ar ion implantation. Two types of domain structures were observed: strictly oriented straight domain rays and cogged ones appeared due to the fingering effect. The piezoresponse force microscopy was used for high-resolution domain imaging. Geometrical characteristics of the domain patterns obtained for different strength of applied field were extracted by statistical analysis. The correlated nucleation mechanism was claimed to be responsible for the formation of observed self-assembled domain structures.

Anomalies of domain structure evolution in congruent lithium niobate with surface layers modified by implantation of Cu ions were investigated. Formation of residual domains and growth of areas occupied by domain patterns with high density of charged domain walls were studied during cyclic polarization reversal. Growth of unusual three-rayed star domains was observed during polarization reversal in low external field much less than the threshold field for conventional congruent lithium niobate. The complicated geometry of these domains in the bulk was revealed using scanning laser confocal microscopy combined with Raman spectroscopy.

The abnormal domain kinetics in congruent lithium niobate single crystals caused by surface modification using proton exchange was studied experimentally. The dependence of domain kinetics on polarity of the growing domains at the surface with proton exchange was revealed. The abnormal smooth motion of irregularly shaped domain walls with finger-like features and correlated nucleation was observed for growth of domains with Z + at surface with proton exchange. Such behavior drastically differs from jump-like motion of plane domain walls oriented along Y directions observed both in conventional lithium niobate and for growth of domains with Z – at surface with proton exchange.

Visualization of as-grown domain patterns and local polarization reversal were carried out in ferroelectric single crystals Pb5Ge3O11 and LiNbO3 using scanning probe microscopy. The piezoresponse force microscopy (PFM) was used for domain imaging. The problem of PFM background signal smearing the domain contrast was solved by special mathematical treatment resulting in clear PFM images. This analysis was applied for extracting the field dependence of the size of domains produced by local polarization reversal in Pb5Ge3O11. The strong effect of abnormal polarization reversal resulting in appearance of the domains with polarization anti-parallel to locally applied field was demonstrated in LiNbO3.

We present the complex study of the polarization reversal process in single crystals of cerium doped relaxor ferroelectric strontium barium niobate Sr 0.61 Ba 0.39 Nb 2 O 6 (SBN61:Ce) using in situ visualization of the domain kinetics by optical microscopy with simultaneous recording of the switching current data. The original mathematical treatment of the experimental data has been used for quantitative characterization of the switching kinetics.

Pulsed implantation of Cu ions into single crystalline congruent lithium niobate resulted in extraordinary effects. First, surface nano-domain structures consisting of star-like domains with rays oriented along three Y directions were induced under the action of the pyroelectric field appeared during cooling after implantation pulse. These nano-domains served as nucleation sites for subsequent polarization reversal under external field. Second, jump-like domain wall motion led to formation of residual domain arrays along the staying positions of the wall. Third, the implantation led to suppression of screening of depolarizing field, due to formation of surface layer with suppressed polarization or non-ferroelectric.

We discuss the most interesting nanoscale domain effects resulting in formation andevolution of self-assembled domain structures in various representatives of LiNbO3 andLiTaO3 family. Several exoti ...

Formation of the nanoscale domain structure in the surface layer as a result of pulsed UV laser irradiation has been studied experimentally in congruent single crystalline lithium niobate LiNbO3. The self-assembled structures have been classified and statistically analyzed. The structure is formed by growth, turning, and branching of domain rays strictly oriented along three Y+ directions. High-resolution microscopy shows that the rays represent the chains of individual needle-like nano-domains. The results of computer simulation of the domain structure formation using experimentally revealed rules are in good agreement with the experimental ones.

We present the experimental study of the geometry of the nanoscale domain structure in classical lead zirconate-titanate relaxor ceramics (Pb1 − x La x )(Zr0.65Ti0.35)O3 (PLZT) with La concentration from 5 to 10%. The analysis of the switching current data measured in rectangular pulses indicates the existence of random three-dimensional maze-type domain structure. High-resolution domain visualization performed using Piezoresponse Force Microscopy (PFM) reveals nanoscale domain patterns. The domain structures existing in PLZT ceramics after zero-field-cooling represent the nanoscale quasi-regular maze (“finger-print”). Statistical and fractal analysis of PFM images was performed for quantitative characterization of the nano-domain structures for different compositions.

We review the study of self-organized formation of several types of quasi-regular micro- and nano-scale domain patterns in single crystalline LiNbO3 and LiTaO3 samples with artificial surface dielectric layers. The domain images revealed by chemical etching have been visualized using optical, scanning electron and scanning probe microscopy (SPM) in contact atomic force mode. SPM piezoresponse imaging mode allows us to investigate the domain structure under the sample surface. We classify the obtained quasi-regular domain structures and discuss the mechanism of their formation and self-maintained growth.

We present the review of our systematic investigation of the propagation of domain walls/boundaries in wide velocity range in uniaxial ferroelectrics with optically distinguished domains, such as lead germanate Pb5Ge3O11, congruent and stoichiometric lithium tantalate LiTaO3 and lithium niobate LiNbO3. In situ optical observation of domain kinetics was widely used. Three different regimes of boundary propagation have been revealed and investigated in details. It was shown that except of conventional “slow” sideways domain wall motion “fast” and “superfast” domain growth regimes through formation of complicated self-maintained domain boundaries could be obtained. The crucial role of the retardation of screening/compensation of depolarization field has been pointed out. It was demonstrated that realization of proper regime is determined by the ratio of switching rate to bulk screening one. Computer simulation has been applied for verification of proposed approach.

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.

Evolution of the domain shape during switching in electric field in congruent and stoichiometric lithium tantalate single crystals has been investigated both experimentally and by computer simulation. Domain patterns were observed using optical microscope. It was shown that typical domain shape is triangular for congruent lithium tantalate and hexagonal for stoichiometric one. The domain shape changes during cyclic switching. The kinetic nature of the domain shape has been proposed. The variety of domain shapes from triangular to hexagonal through intermediate shapes has been studied by computer simulation of the isolated domain growth. We report the first evidence of formation of the ordered domain structure in stoichiometric lithium tantalate with artificial dielectric layer.

We show experimentally that spontaneous decay of highly non-equilibrium domain state in ferroelectric is achieved through the formation of self-organized nanoscale domain structures. The nanodomain structures have been observed by SEM and SFM in uniaxial ferroelectric lithium niobate during spontaneous backswitching after fast removing of switching field. The regular nanoscale domain patterns consist of strictly oriented arrays of nanodomains (diameter down to 30 nm, density up to 100 μm−2). The mechanisms of self-maintaining correlated nucleation effects are discussed.

We present a survey of our recent study of the field-induced domain kinetics in single-crystalline congruent lithium niobate (LN) and lithium tantalate (LT). The proposed backswitched poling by field application to the lithographically defined metal strip electrodes allows to produce periodical micro-scale structures for nonlinear optical application and to demonstrate the first achievements in domain nano-technology.

We present our experimental investigations of the domain evolution in lithium niobate. Particular attention is paid to the short-pitch and nanoscale domain patterning. We demonstrate the production of domain patterns with period down to 2.6 μ.m in 0.5-mm-thick LiNbO3wafers by backswitched poling using lithographic stripe electrodes and nanoscale domain patterns consisting of strictly oriented arrays of nanodomains (diameter down to 30 nm, density up to 100 μm−2).

We demonstrate how the mathematical treatment of the switching current data allows to characterize the variation of the domain structure during fatigue. Investigating PZT/YBCO heterostructures on SrTiO3 and NdGaO3 substrates we propose two different scenarios of fatigue-induced evolution of the domain structure. The essential role of as-grown domain structure is pointed out. It is shown that for high a-domain concentration the growth of the area occupied by a-domains prevails. For low “a-c ratio” we obtain the competition between rejuvenation process and growth of the “frozen” c-domain area at the grain boundaries.

The paper deals with the detail investigation of the smooth motion of the single plane domain wall (PDW) in the vicinity of the initial/steady position and analysis of the mechanisms of Barkhausen noise generation during PDW jump-like motion.