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Coupled phase‐field modeling of domain and fracture evolution in anisotropic ferroelectric ceramics
摘要： The contribution presents a material model for the simulation of domain and fracture evolution in ferroelectric ceramics. Ferroelectric domains and cracks are modeled by using a phase field. While for the modeling of the ferroelectric domains we consider the vectorial electric polarization as order parameter, the modeling of cracks is based on a scalar damage variable. In the present contribution, we discuss the evolution of domains and cracks in an anisotropic ferroelectric solid.
关键词： domain evolution,ferroelectric ceramics,fracture evolution,phase-field modeling,anisotropy
更新于2025-09-16 10:30:52
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An approach for the calculation of local dielectric properties in nanosized systems on the basis of coupled dipoles method
摘要： Despite interest in a description of nanoscale systems properties, there is still a lack of methods that can grasp size dependence and variation across the interface of the static dielectric properties. We propose an approach for the calculation of local nanoscopic electric susceptibility and dielectric permittivity tensors in nanosized systems on the basis of the coupled dipoles method. Requiring only the polarizability of individual molecules, this approach allows one to determine the local dielectric properties of arbitrarily shaped nanoparticles as well as (semi)infinite bodies such as bulk material and infinite films, expanding our ability to predict and govern the behavior of nanoscale systems.
关键词： Boundary layers,Coupled dipoles method,Dielectric response,Permittivity anisotropy,Nanoparticles
更新于2025-09-16 10:30:52
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Annealing effect on laser-induced magnetization dynamics in Co/Ni-based synthetic antiferromagnets with perpendicular magnetic anisotropy
摘要： We report a comprehensive study of annealing treatment modulation on the laser-induced ultrafast magnetic behaviors in antiferromagnetically exchange-coupled [Ni/Co]4/Ru/[Co/Ni]3 multilayers with perpendicular magnetic anisotropy (PMA). Magnetic hysteresis loops indicate that the uniaxial PMA ?eld Hkeff decreases monotonously with the increase in annealing temperature Ta, but the variation of interlayer coupling ?eld Hex is rather complicated. Time-resolved magnetic-optical Kerr effect (MOKE) measurements demonstrate that the laser-excited demagnetization and precession process relies signi?cantly on Ta. Upon laser impulsion, the MOKE signal immediately shows a nonchanging transient increase and decrease with H increasing for low Ta, but only the ultrafast decreasing behavior for high Ta. From the subsequent dynamic precession spectra, the optical and acoustic precession modes are identi?ed. By ?tting the ?eld-dependent frequency curves via the deduced dispersion relations, both Hkeff and Hex are determined and their variation trends agree well with the results from the static magnetic measurement. Moreover, it is found that the critical ?eld where the ultrafast signal decrease occurs is dependent on the co-effect of Hkeff and Hex, whereas the maximum ?eld at which the optical mode precession disappears shares the same trend as Hex. The magnetic damping of acoustic mode is seen to increase with Ta due to the increased inhomogeneities. Our ?ndings provide a deep understanding of the magnetic properties in synthetic antiferromagnetic multilayers with high annealing temperatures, which will be helpful for designing advanced spintronic devices.
关键词： time-resolved magnetic-optical Kerr effect,laser-induced ultrafast magnetic behaviors,annealing treatment,synthetic antiferromagnets,perpendicular magnetic anisotropy
更新于2025-09-16 10:30:52
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Dielectric Anisotropy Sensor Using Coupled Resonators
摘要： In this article, a new approach is proposed for the measurement of the uniaxial anisotropic dielectric constant of different planar samples by means of a single sensor. The sensor is based on a couple of straight-line coupled resonators in microstrip technology that can be excited in odd and even propagation modes. This sensor is designed on an isotropic substrate at the design frequency. Due to the electric field configuration specific for each mode, it is possible to relate these modes to the dielectric constant in two different directions (parallel and perpendicular) of a dielectric material placed on top of the sensor. This technique is used for the successful characterization of the dielectric constant anisotropic of anisotropic dielectrics (FR4, Rogers 4350B, and Arlon Diclad 880), and the isotropic material PTFE.
关键词： FR4,Anisotropic,dielectric constant,printed circuit board (PCB),uniaxial,anisotropy,sample under test (SUT)
更新于2025-09-16 10:30:52
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In-Parallel Polar Monitoring of Chemiluminescence Emission Anisotropy at the Solida??Liquid Interface by an Optical Fiber Radial Array
摘要： Chemiluminescence (CL) detection is widely employed in biosensors and miniaturized analytical devices since it offers high detectability and flexible device design (there are no geometry requirements for the measurement cell, except the ability to collect the largest fraction of emitted photons). Although the emission anisotropy phenomenon for an emitting dipole bound to the interface between two media with different refractive index is well known for fluorescence, it is still poorly investigated for CL reactions, in which the excited-state reaction products can diffuse in solution before the photon emission event. In this paper, we propose a simple method for the real-time evaluation of the CL emission anisotropy based on a radial array of optical fibers, embedded in a poly(methyl methacrylate) semicylinder and coupled with a Charge-Coupled Device (CCD) camera through a suitable interface. The polar-time evolutions of the CL emission have been studied for catalyzing enzymes immobilized onto a solid surface (heterogeneous configuration) or free in solution (homogeneous configuration). Evidence of the anisotropy phenomenon is observed, indicating that the lifetime of the excited-state products of the enzyme-catalyzed reactions is shorter than the time required for their diffusion in solution at a distance at which the CL can be considered isotropic. These results open new perspectives in the development of CL-based miniaturized analytical devices.
关键词： CCD camera detector,chemiluminescence,emission anisotropy,multimode optical fiber
更新于2025-09-16 10:30:52
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Selective oxidation of the surface layer of bilayer WSe <sub/>2</sub> by laser heating
摘要： WSe2 films have several anisotropies between the in-plane and out-of-plane directions, which affects their responses to external operation. Guided by the anisotropies, we provide adequate heat propagation to oxidize selectively the surface layer of bilayer WSe2 and characterized the structure of monolayer WSe2 covered with an oxidized layer by optical and atomic force microscopy, Raman spectroscopy and photoluminescence measurements. Furthermore, we found indications that laser treatments of monolayer WSe2 covered with an oxidized layer have possibility to cause photoactivated oxidation. Our observations suggest clues to understand low-dimensional oxidation behaviours.
关键词： anisotropy,laser heating,WSe2,selective oxidation,photoluminescence
更新于2025-09-12 10:27:22
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[IEEE 2019 15th International Conference on Telecommunications (ConTEL) - Graz, Austria (2019.7.3-2019.7.5)] 2019 15th International Conference on Telecommunications (ConTEL) - Beam Quality Factor and Its Effect on Laser Beam through Anisotropic Turbulence for OWC
摘要： For optical wireless communication (OWC), beam quality factor is used as an important parameter to evaluate the propagation of laser beam through atmospheric turbulence. The beam quality factor and its effect on laser beam are investigated using the generalized anisotropic non-Kolmogorov power spectrum such that anisotropy property of turbulence, general spectral power law, and turbulence inner and outer scales can be considered together. We derive new expressions of beam quality factor for the lowest-order Gaussian beam and higher-mode Hermite-Gaussian beam. The effect of beam quality factor on the beam intensity through turbulence is also analyzed. Numerical results are presented to exhibit influences of different turbulence parameters on the beam quality factor and further on the propagation of laser beam, which provides a better understanding for OWC over free space.
关键词： beam quality factor,inner and outter scales,non-Kolmogorov turbulence,anisotropy,general spectral power law
更新于2025-09-12 10:27:22
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Nanomachining-enabled strain manipulation of magnetic anisotropy in the free-standing GaMnAs nanostructures
摘要： Strain perturbs atomic ordering in solids, with far-reaching consequences from an increased carrier mobility to localization in Si, stabilization of electric dipoles and nanomechanical transistor action in oxides, to the manipulation of spins without applying magnetic fields in n-GaAs. In GaMnAs, a carrier-mediated ferromagnetic semiconductor, relativistic spin-orbit interactions – highly strain-dependent magnetic interactions – play a crucial role in determining the magnetic anisotropy (MA) and anisotropic magnetoresistance (AMR). Strain modifies the MA and AMR in a nanomachined GaMnAs structure as measured by the anomalous Hall effect (AHE) and the planar Hall effect (PHE). Here, we report an MA modification by strain relaxation in an isolated GaMnAs Hall bar structure and by applying a range of local strains via fabricating asymmetrically mechanically buckled GaMnAs micro-Hall bar structures. in the AHe and pHe measurements, we observe a reduction in the in-plane MA and an enhancement in the out-of-plane MA as the compressive strain due to the lattice mismatch relaxes in the suspended structure. The functionality of such mechanical manipulation, as well as the two-level mechanical state and the corresponding AHe responses, is demonstrated by a fully scalable binary mechanical memory element in a GaMnAs single Hall cross structure.
关键词： strain,GaMnAs,magnetic anisotropy,planar Hall effect,anomalous Hall effect
更新于2025-09-12 10:27:22
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Dielectric and electro-optical properties of zinc ferrite nanoparticles dispersed nematic liquid crystal 4’-Heptyl-4-biphenylcarbonnitrile
摘要： In this work, comprehensive results on dielectric and electro-optical properties of pristine and zinc ferrite (ZnFe2O4) nanoparticles (NPs) dispersed in host nematic 4?-Heptyl-4-biphenylcarbonnitrile (7CB) systems are reported. The dielectric and EO properties of pristine and NPs dispersed (concentrations 0.05, 0.1, 0.15, 0.2, 0.3 and 0.5 wt%) into the host nematic system have been studied. We have seen uniform NPs dispersion into nematic 7CB up to 0.15 wt% concentration of NPs by the POM. The NPs aggregation starts at 0.2 wt% dispersion. It is shown that the dielectric and electro-optical properties are strongly in?uenced by the concentration of NPs in host nematic and applied electric ?eld. The dielectric anisotropy is maximum for the NPs dispersed system of 0.15 wt% concentration. The Birefringence, parallel and perpendicular components of permittivity and conductivity are found to be dependent on temperature and concentration of NPs into host matrix. In pure nematic material, small memory is seen but in NPs dispersed systems noticeable memory is found. In particular, pronounced memory is found for the dispersed system of 0.3 wt% concentration of NPs.
关键词： Nematic liquid crystal,zinc ferrite nanoparticles,birefringence,splay elastic constant,dielectric anisotropy
更新于2025-09-12 10:27:22
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Giant plasmonically induced circular conversion dichroism in an anisotropic golden slit grating filled by a chiral medium
摘要： We report the giant plasmonically induced (PI) circular conversion dichroism in transmission (CCDT ) and PI-unconverted CD effect (unCCDR ) in re?ection from the golden slit grating ?lled by chiral medium (GSGCM). The CCDT and unCCDR are the differences between the off-diagonal elements in transmission matrix and diagonal elements in re?ection matrix, respectively, and originate from both the chirality and anisotropy. Our research indicates that the PI ? CCDT and PI-unCCDR in the plasmonic resonance wave band come from the coupling between the inherent chiroptical resonance of chiral medium and the plasmonic resonance of the golden slit grating, where the real part of chiral parameter ξ from chiral medium plays a main role in the coupling process. The isotropic chiral medium slab, the anisotropic chiral medium grating, the golden slit grating, and the GSGCM have been rigorously investigated in this work. Our research clearly reveals the difference of PI-chiroptical effect between the anisotropic and isotropic system, and will ?nd potential applications in biosensor and nanophotonic devices.
关键词： golden slit grating,biosensor,plasmonically induced circular conversion dichroism,nanophotonic devices,anisotropy,chiral medium
更新于2025-09-12 10:27:22