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Spin Rectification dc Voltage Spectra via Sweeping Frequency
摘要： A new measurement method of a spin rectification dc voltage spectrum through fixing the magnetic field and sweeping the frequency has been proposed, which is compared to the common method to acquire a typical spectrum via sweeping an external magnetic field. Based on the shortened microstrip fixture, the measurements of rectified dc voltage as a function of frequency have been performed. From the analysis of results of the permalloy (Py) film with various thicknesses, the magnetic parameters are presented. This method can be used in samples with magnetic domains varied with respect to the external magnetic field, such as, stripe domain structures.
关键词： stripe domain structure,monolayer Py films,frequency-swept,spin rectification effect (SRE)
更新于2025-09-23 15:23:52
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Epitaxial Growth of Orthorhombic GaFeO3 Thin Films on SrTiO3 (111) Substrates by Simple Sol-Gel Method
摘要： A Sol-gel method assisted with spin-coating has been successfully used to grow orthorhombic GaFeO3 epitaxial films on SrTiO3 (111) substrates for the first time. The film with Pna21 crystal structure has been grown along the c-axis. The rocking curve of (004) reflection shows that the Full-Width at Half-Maximum (FWHM) value could be determined to be 0.230°, indicating good single crystallinity and high quality. X-ray Φ scan reveals a three-fold symmetry of the substrate and a six-fold symmetry of the film, respectively. The in-plane domains rotate 60° from each other in the film. Uniform film with dense structure, columnar grains with similar grain size was obtained. The thickness of the film was evaluated to be ~170 nm. The roughness value (RMS) measured by AFM was 4.5 nm, revealing a flat film. The in-plane Magnetization versus Magnetic field (M-H) curve at 5 K performs a typical ferri- or ferromagnetic hysteresis loop with a saturated magnetization (Ms) value of 136 emu/cm3. The Curie temperature could be determined to be 174 K. Compared to Pulsed Laser Deposition (PLD), the sol-gel method can prepare large area films with low cost. These new films show promising applications in multiferroic devices.
关键词： GaFeO3 film,magnetic property,sol-gel method,multi-domain structure,epitaxial growth
更新于2025-09-23 15:22:29
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Self-assembled shape evolution of the domain wall and formation of nanodomain wall traces induced by multiple IR laser pulse irradiation in lithium niobate
摘要： The formation of the domain structure in congruent lithium niobate crystals by multiple pulse irradiation using an infrared laser was studied experimentally. The qualitative change of the domain wall shape with an increase of the pulse number was revealed. The chains of isolated nanodomains representing the domain wall traces appeared after each laser pulse irradiation in the samples with an irradiated polar surface covered by an indium–tin oxide layer. This effect allowed extraction of the detailed information about the evolution of the domain wall shape. The domain kinetics under the action of the pyroelectric field has been considered. The mechanism of the self-assembled shape evolution of the moving domain wall as a result of the local wall accelerations and retardations caused by the shape fluctuations (bumps and valleys) was proposed. The experimentally observed formation of the quasi-regular comb-like domain structures with randomly distributed bumps and valleys was confirmed by computer simulation. The discovered effects allowed us to create the stable random and quasi-regular domain structures and open the way for further development of the domain engineering methods.
关键词： pyroelectric field,infrared laser,nanodomains,domain wall shape evolution,lithium niobate,domain structure
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Periodically Poled MgO:LiNbO <sub/>3</sub> , MgO:LiTaO <sub/>3</sub> and KTiOPO <sub/>4</sub> Crystals for Laser Light Frequency Conversion
摘要： We present the recent achievements in periodical poling in MgO doped single crystals of lithium niobate (LN), lithium tantalate (LT) and potassium titanyl phosphate (KTP) based on the experimental study of the domain structure evolution by the complementary high-resolution domain visualization methods [1]. The crystals with tailored periodically poled domain structures (PPLN and PPLT) produced with nano-scale period reproducibility have been used for Second Harmonic Generation (SHG) and Optical Parametric Oscillation (OPO) based on quasi-phase-matched nonlinear optical wavelength conversion. The periodical poling techniques were based on the deep experimental and theoretical study of the mechanisms of domain growth and domain wall motion in these crystals. The wide range of wall velocities with two orders of magnitude difference was observed for switching in a uniform electric field [2,3]. The kinetic maps allowed analyzing the spatial distribution of the wall motion velocities and classifying the walls by velocity ranges. The distinguished slow, fast, and superfast types of domain walls in KTP differed by their orientation. The revealed increase in the wall velocity with deviation from low-index crystallographic planes for slow and fast walls was considered in terms of determined step generation and anisotropic kink motion. It was shown that the polarization reversal in KTP with artificial surface dielectric layer leads to formation and growth of the large number of narrow domain streamers oriented strictly along [010] direction with about ten times higher velocity (6-60 mm/s) than the domain walls (2-5.5 mm/s). Study of the static domain structures demonstrated that the streamers are formed by [100] and [010]-oriented domain walls. The streamer width was about 500 nm and the distance between the neighboring streamers – about 100 nm. The global domain kinetics during the poling process at elevated temperatures has been studied by in situ optical observation which allowed us to reveal the main characteristics of the poling process at elevated temperatures. It has been shown that the periodically poled area propagates from the edges to the middle of the electrode pattern. The interfering effect of essential increasing of the bulk conductivity during poling has been studied and several ways to overcome this problem have been proposed. The static domain images revealed by chemical etching were visualized by optical and scanning probe microscopy. The influence of the spatially nonuniform electric field on the domain kinetics has been studied for finite-size electrodes of various shapes. The key role of the field anomalies at the electrode corners, ends, and edges in the nucleation process has been revealed by computer simulations and confirmed experimentally. Essential acceleration of the switching at the boundaries of the electrode patterns (so called “pattern effect”) has been explained. The optimized design of the electrode pattern was based on experimental results and computer simulation. The fan-out periodical domain structures created in 3-mm-thick MgO:LN wafers allowed us to realize the widely tunable OPO generation with the signal wave from 2.5 to 4.5 μm using the 1.053 μm pump. The possibility of producing the elements with thickness up to 10 mm for high-power application has been discussed. The peridical domain struture with period of 40 μm was created in KTP single crystals for OPO generation at 2.4 μm using the 1.053 μm pump. The abilities and perspectives of producing the elements with submicron periods has been discussed. The optimized periodical poling techniques have been used for creation of ridge waveguides in periodically poled MgOLN single crystals. The high-index contrast of obtained multi-mode waveguides allowed tuning of the SHG wavelength from 510 to 570 nm using the 1.064 μm pump. The deep knowledge of the domain structure evolution at elevated temperatures and relaxation of the high bulk conductivity along the charged domain walls MgO:LN and MgO:LT allowed us to optimize the periodical poling technique and to produce high-fidelity domain patterns.
关键词： domain structure evolution,MgO:LiTaO3,KTiOPO4,Second Harmonic Generation,Optical Parametric Oscillation,MgO:LiNbO3,Periodically Poled
更新于2025-09-23 15:19:57
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Mechanical writing of in-plane ferroelectric vortices by tip-force and their coupled chirality
摘要： Recent experiments have demonstrated the existence of vortex or flux-closure domains in ferroelectric nanostructures, which are attractive to develop high-density data storage and novel configurable electronic devices. However, it remains challenging to stabilize in-plane vortex or flux-closure domains in ferroelectric film for the absence of a lateral geometry confinement. Based on a 3D phase field model, here we show that stabilization of isolated or interacting in-plane vortices in ferroelectric film can be achieved via applying a mechanical tip-force. The formation of such dipole vortices is caused by a conjoint effect of the tip-force-induced depolarization effect and in-plane strain. The effects of factors like film thickness, misfit strain, tip force and temperature on the vortex formation are systematically revealed and summarized as phase diagrams. The interaction between tip-induced vortices is also investigated. It is found that as the two tips get closer than the critical distance, the two initially isolated vortices become coupled, with identical or opposite chirality, depending on the distance between the two tips. A maximum data storage density of isolated in-plane vortices in ferroelectric thin film is estimated to be ~1 Tb in?2. Our work thus demonstrates a mechanical strategy to stabilize dipole vortices, and provides a comprehensive insight into the characteristics of ferroelectric film under a mechanical tip force.
关键词： flexoelectricity,ferroelectric,mechanical force,domain structure,vortex
更新于2025-09-23 15:19:57
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Mn-doping composition dependence of the structures, electrical and magnetic properties, and domain structure/switching of Aurivillius Bi5Ti3FeO15 films
摘要： Mn-doped Bi5Ti3FeO15 (BTFO) ?lms were prepared by a chemical solution deposition route. The e?ect of a series of di?erent Mn-doping concentrations from 0.05 to 0.4 on structures, electrical and magnetic properties, and domain structure/switching was systematically studied. Mn-doping into BTFO can avail the grain growth. Ferroelectric and dielectric properties are improved through Mn-doping, and the optimized Mn-doping content is 0.25 with remnant polarization of 17.2 μC/cm2 and permittivity of 371.2 at 10 kHz. Moreover, similar evolution of the permittivity and loss tangent with frequency to that of parent BTFO ?lms appears in the BTFMO ?lms when Mn-doping content is below 0.25, while obvious dispersion phenomena is demonstrated with further increasing Mn-doping content. A 180° domain structure and local ferroelectric switching are observed in all these Mn-doped BTFO thin ?lms, and the piezo-displacement can reach 416 p.m. in 0.15 Mn-doped BTFO ?lm. Finally, ferromagnetic properties appear in all these Mn-doped BTFO thin ?lms. The coercive ?eld shows weak temperature independence on Mn-doping contents, while the remnant magnetization is raised by Mn-doping.
关键词： Domain structure and switching,Dielectric response,Magnetic property,Ferroelectric property,Aurivillius compounds,Element doping
更新于2025-09-19 17:15:36
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Two-level hierarchical stripe domains and enhanced piezoelectricity of rapid hot-press sintered BiFeO <sub/>3</sub> ceramics
摘要： BiFeO3 represents the most extensively investigated multiferroic due to its fascinating ferroelectric domain structures, large polarization, and multiferroic coupling, among many other emergent phenomena. Nevertheless, much less concern with the piezoelectricity has been raised while all these well addressed properties are identified in thin film BiFeO3, and bulk ceramic BiFeO3 has never been given priority of attention. In this paper, we report our experiments on the ferroelectric and piezoelectric properties as well as domain structures of BiFeO3 bulk ceramics synthesized by rapid hot-press sintering. It is revealed that these properties are strongly dependent on the microstructural quality, and the largest piezoelectric coefficient d33 = 55 pC/N with electric polarization as large as 45 μC/cm2 is obtained for the sample sintered at 800 °C, while they are only 30 pC/N and 14 μC/cm2 for the samples sintered in normal conditions at 800 °C. The two-level hierarchical stripe-like and irregular dendrite-like domain structures are observed in these hot-press sintered samples. It is suggested that the enhanced piezoelectric property is ascribed to the two-level hierarchical stripe-like domain structure which may respond more easily to electrical and strain stimuli than those irregular dendrite-like domains. The enhanced remnant polarization should be owing to the improved sample quality and large grains in the properly hot-press sintered samples.
关键词： ferroelectric,hot-press sintering,BiFeO3,multiferroic,domain structure,piezoelectric
更新于2025-09-10 09:29:36
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Outstanding piezoelectric properties, phase transitions and domain configurations of 0.963(K0.48Na0.52)(Nb0.955Sb0.045)O3?0.037(Bi0.50Na0.50)HfO3 ceramics
摘要： Requirements for substituting the current lead-based piezoelectric materials with lead-free ones are becoming increasingly strong from environmental concerns. In this article, we report piezoelectric properties, phase transitions and domain configurations of a dense 0.963(K0.48Na0.52)(Nb0.955Sb0.045)O3?0.037(Bi0.50Na0.50)HfO3 lead-free ceramic prepared through solid-state reaction by two-step sintering. It has a large piezoelectric coefficient d33 = 512 pC/N and a planner eletromechanical coupling coefficient kp ≈ 0.54 at room temperature. Dielectric measurement indicates that rhombohedral-orthorhombic, orthorhombic-tetragonal, and tetragonal-cubic phase transitions upon heating process occur at ?30 °C, 57 °C and 238 °C, respectively. X-ray diffraction analysis shows that the crystalline structure is dominantly of orthorhombic phase at room temperature. Domain configurations were investigated by acid etching technique. The poled ceramic shows domain patterns of long parallel stripes with hierarchical nanodomain structure existing in some broad stripes. The observed outstanding piezoelectric properties are ascribed to the rhombohedral-orthorhombic and orthorhombic-tetragonal phase transitions, and to the characteristic domain structure.
关键词： Phase transitions,Piezoelectricity,Lead-free ceramics,Ceramics,Ferroelectrics,Domain structure
更新于2025-09-10 09:29:36
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Ferroelectric behavior in nanocrystalline KNbO <sub/>3</sub> synthesized by a modified polymerized complex method
摘要： Effect of nanocrystalline size of the particles on ferroelectric properties of KNbO3 is studied. Properties like hysteresis parameters, phase transition temperatures and domain morphology in nanocrystallites were studied by using P-E hysteresis, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) techniques, respectively. Nanocrystalline KNbO3 compound was synthesized by a modified polymerized complex method and room-temperature structural phase was characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Field emission gun-scanning electron microscopy (FEG-SEM) was used to reveal the size and morphology of the particles. It was found that the present nanoparticles of sizes ranging from 50 to 250 nm bears polarization values <1 lC/cm2, and undergo cubic-tetragonal and tetragonal-orthorhombic phase transitions at 312 and 87 (cid:1)C respectively. Although the value of polarization is small as compared to the bulk reported in the literature, the nature of P-E loops along with phase transitions and presence of 60, 90 and 180(cid:1) domain structures indicates retention of ferroelectric nature in KNbO3 even at the nanolevel.
关键词： domain structure,Nanocrystalline material,phase transition,ferroelectrics
更新于2025-09-10 09:29:36