Rearrangement Of Domain Structure Research Articles

Stress dependence of the magnetic properties of glass-coated amorphous microwires

We studied the effect of applied tensile stresses on magnetic properties of Fe- and Co-rich amorphous glass-coated microwires. Rising of magnetic anisotropy field upon tensile stress in Co-rich glass-coated microwires is described by a linear dependence. Furthermore, decrease of magnetic susceptibility upon tensile stress is observed in Co-rich microwires. A monotonous increase in the coercivity and the switching field upon tensile applied stress is observed for as-prepared Fe-rich microwire. Stress induced magnetic bistability consisting of transformation of hysteresis and onset of rectangular hysteresis loop upon tensile stress, σ, of about 22.5 MPa is observed in stress-annealed Fe-rich microwires. Such stress-induced magnetic bistability results in considerable growing of coercivity and remanent magnetization in stress-annealed Fe-rich microwires. The rising in the coercivity and the switching field upon applied tensile stresses in stress-annealed Fe-rich microwires with stress induced magnetic bistability (at σ > 22.5 MPa) is roughly described by the σ½ dependence, as previously reported for the wires with spontaneous magnetic bistability. Consequently, stress-annealing of Fe-rich microwire allows beneficial enhancement of the stress dependence of coercivity. Observed dependencies are discussed considering stress dependence of the magnetostriction coefficient in Co-rich glass-coated microwires, internal stresses redistribution and domain structure rearrangement in stress-annealed Fe-rich microwires upon applied tensile stresses.

Direct Microscopic Observation of Domain Rearrangement Mechanism of Photo-Orientation Process in Azobenzene-Containing Materials.

The evolution of the domain structure of two azobenzene-containing materials during irradiation with polarized light was monitored using polarized optical microscopy with additional λ-waveplate for discerning the domains oriented parallel and perpendicular to irradiating light polarization. It is shown that the process of photo-orientation consists in growth of perpendicularly oriented domains and diminishing of parallel domains via the movement of domain boundaries. These data confirm the mechanism of photo-orientation via domain structure rearrangement.

Arguments Reinforcing the Three-Domain View of Diversified Cellular Life

The archaeal ancestor scenario (AAS) for the origin of eukaryotes implies the emergence of a new kind of organism from the fusion of ancestral archaeal and bacterial cells. Equipped with this “chimeric” molecular arsenal, the resulting cell would gradually accumulate unique genes and develop the complex molecular machineries and cellular compartments that are hallmarks of modern eukaryotes. In this regard, proteins related to phagocytosis and cell movement should be present in the archaeal ancestor, thus identifying the recently described candidate archaeal phylum “Lokiarchaeota” as resembling a possible candidate ancestor of eukaryotes. Despite its appeal, AAS seems incompatible with the genomic, molecular, and biochemical differences that exist between Archaea and Eukarya. In particular, the distribution of conserved protein domain structures in the proteomes of cellular organisms and viruses appears hard to reconcile with the AAS. In addition, concerns related to taxon and character sampling, presupposing bacterial outgroups in phylogenies, and nonuniform effects of protein domain structure rearrangement and gain/loss in concatenated alignments of protein sequences cast further doubt on AAS-supporting phylogenies. Here, we evaluate AAS against the traditional “three-domain” world of cellular organisms and propose that the discovery of Lokiarchaeota could be better reconciled under the latter view, especially in light of several additional biological and technical considerations.

On mechanisms of domain switching in amorphous glass‐coated wires

The study of the magnetic properties of amorphous wires is a topic of great interest because of their outstanding properties, such as the giant magnetoimpedance effect. The domain structure of the amorphous wire consists of an axially magnetized inner core and the outer shell. Taking into account that the giant magnetoimpedance effect is mainly a surface effect, the investigation of surface magnetic structure in the outer shell becomes a special topic. Discovering earlier the basic domain structures, here we demonstrate the original domain structures and mechanisms of magnetization reversal in Co‐ and Fe‐rich glass‐covered microwires. In particular, we focused on the temperature dependence of the magnetization reversal process. The original effect – the rearrangement of domain structure without the domain walls movement – was found.

Electro-optic control of optical beams by rearrangement of the ferroelectric domain structure

The light passing through a ferroelectric crystal tends to split into several separate beams due to refraction and reflection at the domain walls. The corresponding intensities are known to depend on the electric field applied to the crystal. We propose a simple model taking into account multiple refractions and rearrangement of the domain structure with no assumptions on the specific material properties. The obtained coupling between intensity of the deflected light and the relative macroscopic ferroelectric polarization is in good agreement with known experimental data.

Electron Emission from TGS Crystals Grown on Seeds Exposed to Alpha Particles

The electron emission from triglycine sulfate crystal grown on a seed exposed to alpha-particles has been studied. It is shown that the emission manifests a behavior characteristic of unipolar material: in the region of rearrangement of domain structure and in the region of phase transition maxima there exist in the temperature dependence of emission current and their heights depend on the degree of unipolarity of a sample and the distance from it to the seed.

Rearrangement of ferroelectric domain structure induced by chemical etching

The rearrangement of the domain structure induced by chemical etching has been observed in periodically poled MgO-doped stoichiometric lithium tantalate single crystals. Topographic and piezoresponse scanning probe microscopy have been used for measuring the etching relief height and domain wall position after etching. The considerable shift of the domain wall during etching by pure hydrofluoric acid has been revealed by analysis of the experimental data. We have found that the wall motion proceeded after the termination of the etching procedure. We have shown that the whole consequence of the domain wall positions during etching is recorded in the etching relief height and can be extracted with high spatial and temporal resolution.

Circular magnetic bistability induced by tensile stress in glass-covered amorphous microwires

Investigations of magnetic reversal in Co-rich glass covered amorphous microwires were performed using the magneto-optical Kerr-effect technique. The appearance of circular magnetic bistability was found in the presence of external tensile stress. A tensile-induced large Barkhausen jump of circular magnetization is associated with a change of the value of the magnetostriction constant induced by stress and by rearrangement of domain structure in the outer shell of the microwire.

The governing of anisotropy of real piezoelectric ceramic materials

The accumulation of defects of the crystal structure and the rearrangement of domain structure of crystallites in ferro-piezoelectric ceramics during multiple cyclic polarization reversal in a strong ac electric field leads to increased anisotropy of the piezoelectric effect in ferrosoft PCR-1-and PCR-7M-type ceramics.

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.

Stabilization and destabilization of domain wall positions in Fe [sbnd]Si polycrystals using magnetic annealing effects

The effect of variation of magnetic annealing conditions on the properties of grain-oriented Fe-3%Si steels was investigated. It was shown that during magnetic annealing with special magnetizing conditions (in the B-range, corresponding to the stability of a large number of 90°-supplementary domains), the special magnetic structure is stabilized. This state is characterized by the increase of the sample magnetostriction in low and high fields as well as under compression, demonstrating the increased contribution of 90°-domain wall displacements and the magnetic domain structure rearrangement. The initial material state may be recovered using magnetic reannealing in the AC field by means of destabilization of induced changes in structure. Magnetic annealing in high DC fields yields an increase of preferred alignment of magnetic domains along the rolling direction and a pronounced magnetostriction decrease.

Isothermal relaxation due to random local phase transformation in pbzr0.993ti0.007o3 single crystal

Abstract In a PbZr0.993Ti0.007O3 single crystals of the perovskite structure an isothermal structural transformation has been found. One of phase transitions appearing in this compound between the paraelectric, ferroelectric and antiferroelectric states disclosed a time dependent character. Only on cooling there is a temperature range in the intermediate ferroelectric phase inside which spontaneous transformation from the ferroelectric (R3m) to antiferroelectric (Pbam) state takes place in time at constant temperature. By means of three different experimental methods (dielectric, X-ray and optical) it was established that the transformation was completed after about 30 minutes. X-ray diffraction proved that this transition was of structural type and optical observation excluded this phenomenon to be related with a domain structure rearrangement. Nature of phase transitions in the investigated crystal is discussed from the point of view of martensitic transformation.

Surface potential of TGS and LATGS crystals

Abstract . The induction probe method is used to study the surface potential of TGS and LATGS crystals. The influence of L-alanine doping on the magnitude and decay of surface potential for LATGS crystal is found. The samples without internal bias field show nearly the same initial value and decay rate of surface potential for opposite electrode potentials. The opposite electrode potentials applied to the sample with internal bias field give different rate of surface potential decay. These changes of decay rate are related to domain structure rearrangement.

Domain structure of (Ba, Sr)TiO3heteroepitaxial films

Abstract The dependence of domain structure on film structural perfection was studied. Domain structure rearrangement due to both mechanical stresses and temperature variation was observed.

Rearrangement of domain structure in ferroelectrics near isostructural phase transitions

Abstract It is shown that anomalies of physical properties in a ferroelectric phase of some ferroelectrics which are not accompanied by the crystal group symmetry change may be explained as a result of thermo-dynamic path passing through supercritical region of isostructural phase transitions in the phase diagram on the basis of phenomenological model of crystal.

Power losses versus stress and temperature in soft amorphous alloys

The role of stress-induced anisotropy on magnetic power losses has been investigated in FeBSiC amorphous ribbons, in the ‘‘as-quenched’’ state and after annealing. Loss separation has been accomplished up to 400 Hz, under a wide range of applied tensile stresses (3.5 MPa≤σ≤300 MPa). It is found that, by increasing σ, the hysteresis loss component Wh is initially decreased and passes through a minimum around a critical stress σ0. Correspondingly, rearrangement of the maze domain structure associated with the unstressed state occurs and a longitudinally oriented pattern sets in. The dynamic loss exhibits a somewhat opposite trend, as it tends to monotonically increase with σ, thus attenuating the overall benefits of tensile stressing. Insight on the physical mechanisms responsible for these phenomena is obtained by measuring, at different stress levels, Wh versus temperature (20 °C≤T≤280 °C). Topological rearrangements of the domain structure and interaction of the Bloch walls with localized stress fluctuations are envisaged, in association with roughness of the ribbon surface, as the main sources of coercivity and losses. As to the relaxation aftereffect, this is shown to produce additional loss under fairly restricted conditions of temperature and magnetization rate.

Domain structure of PSD- and MD-grains and its temperature dependence

Abstract A theoretical model which predicts a strongly temperature-dependent domain structure in MD magnetite grains is presented. The temperature dependence of domain structure is of a great interest in rock magnetism because: (1) a number of direct observations of domain structure demonstrate a strongly temperature-dependent pattern; (2) domain structure rearrangement is believed to be an important physical mechanism in thermoremanence aquisition.

Temperature dependence of domain structure in natural magnetite and its significance for multi-domain TRM models

Abstract Magnetic domain structures of natural magnetite grains were observed as a function of temperature with the Bitter method. The domain walls were completely rearranged during heating from 20 to 90°C. Parallel 180° domain walls at 20°C changed to complicated curved domain walls of the stress-controlled type when heated in zero field to 90°C. These changes in domain structure could be explained by the faster decrease of the magnetocrystalline anisotropy energy with increasing temperature compared with the slower decrease in the magnetoelastic energy term. Temperature-dependent domain wall changes in magnetite were postulated previously by measurements of partial thermoremanent magnetization. A synthesis of microscopic domain observations, macroscopic magnetization measurements and multidomain theories is attempted. Published data on the acquisition and decay of partial thermal remanent magnetization are interpreted in terms of the continuous rearrangement of domain structure with changing temperature.

Peculiarities of dynamical properties of domain walls and phase boundaries in some ferroelectric single crystals and ceramics near phase transition

Abstract Low- and infralow frequencies dielectric spectra of some ferroelectric single crystals (RS, KTL, PMN, CDP) and ceramics (PZT, PSN, PLZT) are studied in the vicinity of phase transition temperatures. Oscillation parameters of 180° domain walls in weak fields are determined on the basis of phenomenological consideration of polydomain ferroelectrics dielectric properties. Quantitative estimates are presented for elasticity and viscosity coefficients, electric compliance and domain-walls displacement amplitude in field intensity of E ≈ 1V·m−1. The connection of the above parameters with “weak” and “strong” defects in crystals is discussed. Examples are adduced of revealing the processes of domain structure rearrangement, domain-wall pinning, polarized defects interrelations, formation of clusters and other phenomena associated with phase transition o in real ferroelectric single crystals and ceramics.

Technique for investigation of ferroelastics strain-stress curves peculiarities related to domain structure rearrangement

The apparatus for investigation of ferroelastics in torsion and homogeneous bending with the simultaneous domain structure observation is described. Strain-stress curves for KFe(Mo04)2 are given. These curves peculiarities disclose a distinct correlation with ferroelastics domain structure rearrangement processes.