Papers by Keyword: Domain Structure

Abstract: A model of the rearrangement of the domain structure of the Tb_0.2Y_2.8Fe₅O₁₂ garnet ferrite in the temperature region of the spontaneous reorientation of the easy magnetization axis is proposed, which makes it possible to consistently describe (at a qualitative level) the entire set of experimental results obtained. The latter makes it possible to make a choice in favor of the fluctuation mechanism of nucleation of domains of a new magnetic phase in the process of reorientation of the direction of the easy magnetization axis.

Abstract: Atomic force microscopy techniques (conductive-AFM, I-V spectroscopy and PFM) were used for characterisation of the local electrical properties of bilayer polyaniline-polystyrene/P(VDF-TrFE) polymer nanocomposite. Observed hysteresis of current-voltage characteristics confirms its memristive properties. It was caused by the influence of the ferroelectric polarization of P(VDF-TrFE) layer, the domain structure of which was visualised by piezoelectric force microscopy on the transport of charge carriers at the interface.

Abstract: A series of Fe_75.5-xNi_xCu₁Nb₃Si_12.5B₈ (x=0.5-10 at. %) soft magnetic dual-phase alloys with low permeability were synthesized by adjusting Ni content. Effect of annealing on the soft-magnetic properties, crystallization behavior and microstructure were investigated. It is found that the temperature interval between the two crystallization temperature is significantly decreased from 169 to 127°C when the Ni content of the alloys increases from x=0.5 to x=10, which greatly reduces the optimum annealing temperature range. The alloys with higher Ni content are prone to exhibit lower permeability, and the alloys with the composition of Fe_65.5Ni10Cu₁Nb₃Si_12.5B₈ exhibit excellent soft-magnetic properties, including the low permeability of 3350, low coercivity of about 1.26 A/m and low remanence of 8 mT. The combination of low permeability and excellent soft-magnetic properties makes the FeNiCuNbSiB nanocrystalline alloys to be a kind of promising material for common mode chokes and current transformer with direct current tolerance.

Abstract: The article is devoted to the analysis of polarization reversal process arising in ferroelectrics under electron beam exposure. The advanced model was proposed to describe the polarization switching process in ferroelectrics as well as formation of polarization switching response in electron beam-induced polarization current mode of SEM taking into account the specific character of domain structure dynamics. Simulation of polarization switching current in TGS ferroelectric crystals was performed to estimate the main characteristics of electron beam-induced polarization reversal processes.

Abstract: The influence of most physical factors on the revelation ability of magneto-optic eddy current defectoscopy of linear defects in metallic objects is investigated. Uniaxial anisotropy multi-component Bi-substituted garnet film is used as the sensor element. The efficiency of visualization depends on frequency and amplitude of the inducer’s electric current and the biasing magnetic field. Optimal values of these parameters are obtained. It is shown that the alternative magnetic field exerts the most influence on the eddy current magneto-optic image.

Abstract: PbTiO₃ (PTO) films were successfully fabricated by sol-gel method. We studied the structure and the nanoscale polarization switching property using XRD and Piezoresponse Force Microscopy. The results reveal that the PTO films are single perovskite phase grain films with tetragonal structure, and are polycrystalline materials with no evidence of preferential orientation. The average grain size is about 150nm and a striped multi-domain structure is exhibited in individual grains. Under 15 kHz alternating current of PFM, a significant asymmetry of switching pattern was observed. We suggest that the cooperative action of the built-in electric field at the bottom interface and the PFM ac-voltage lead to the asymmetry switching.

Abstract: The relaxor state has been found in the mixed ferroelectric system Ba (Ti_1-xZr_x)O₃ around x = 0.35. To understand the nature of the relaxor state, the crystallographic features of the paraelectric (PC), ferroelectric, and relaxor states for 0.15 ≤ x ≤ 0.40 have been investigated mainly by transmission electron microscopy. It was found that a microstructure of the ferroelectric state for 0.15 ≤ x ≤ 0.28 consisted of banded structures with boundaries parallel to the {110}_PC and {100}_PC planes. Based on the Sapriel theory concerning ferroelastic transitions, it was understood that the banded structures were consistent with domain structures in the ferroelectric rhombohedral (FR) state having a polarization vector parallel to one of the <111>_PC directions. With the help of the failure of Friedel’s law in diffraction, furthermore, polar regions having <001>_PC and <110>_PC components of a <111>_PC polarization vector were also found to be separately observed in the PC and relaxor states as well as the FR state. Then, in-situ observation for 0.29 ≤ x ≤ 0.40 made in this study indicated that the PC and relaxor states consisted of polar nanometer-sized regions having these two components. Based on this, the relaxor state in BTZ can be identified as an assembly of polar nanometer-sized regions, which were produced by the suppression of the (PC→FR) ferroelectric transition on cooling.

Abstract: Thermal processing of materials in external magnetic field is employed in order to produce a controllable uniaxial anisotropy and to tailor a domain structure in the series of soft magnetic FeCo-and FeNi-based amorphous/nanocrystalline alloys. Examples of our recent work on the utilization of both longitudinal and transverse magnetic field annealing for tuning the shape of hysteresis loops as well as the giant magnetoimpedance (GMI) characteristics are briefly presented. The beneficial effects of a heat treatment under magnetic field are discussed in terms of the improved application-oriented properties of these soft magnetic alloys.

Abstract: The technical magnetization and the domain structure of a Tb0.26Y2.74Fe5O12 single crystal have been studied in the temperature region of a spontaneous spin-flip phase transition (SFPT) by magneto-optical method. It has been found that the character of evolution of domain configuration in a SFPT depends from mechanical stresses in crystal.

Abstract: The mechanism of spin-reorientation phase transmission (SRPT) has been examined. The structure change of domain boundaries in process of phase transmission (PT) has been researched. The models of domain structure (DS) relevant to experiment have been offered. It is shown that in connection with temperature change of the anisotropy constants the structure of domain boundaries and view of DS changes as well, SPRT and PT takes place in the domain boundaries.