- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2019
- 2018
- electromagnetic pulse
- cell proliferation
- cell membrane permeability
- cell response to electromagnetic stress
- apoptosis
- cancer therapy
- necrosis
- periodic structures
- electromagnetic screening
- filtering
- Optoelectronic Information Science and Engineering
- Intelligent Medical Engineering
- Southern University of Science and Technology
- Politehnica University of Timi?oara
- Wroclaw University of Technology
- Centro de laseres pulsados
- Szchenyi Istvn University
- ELI-ALPS, ELI-HU Non-Profit Ltd.
- V.N. Karazin Kharkiv National University
- Politecnico di Torino
- Centro de laseres pulsados and University of Salamanca
-
nanoparticles
摘要： We report changes on the magnetic behavior of the Heavy-Fermion ferromagnetic YbNi2 alloy when reducing the size of the particles to the nanometer scale by high-energy ball milling. The milling process induces a reduction on the particle size of the bulk alloy down to 10 (2) nm and a lattice strain of 1.8 (2)%, for 30 h of milling time, as calculated from the x-ray diffraction data. The ferromagnetic transition at TC =10.5 K in the bulk alloy tends to disappear whereas other magnetic transitions arise at lower temperatures with the milling process. The AC magnetic susceptibility of the 30 h milled sample shows a frequency independent peak at 3 K, in a wide range of frequencies, consistent neither with superparamagnetic nor simple freezing of the magnetic moments, and as expected for a ferromagnetic behavior. However, from the specific heat measurements in the 30 h milled sample, a peak at 3.6 K is shifted respect to that observed in the AC magnetic susceptibility, as found in spin glasses. Additionally, the specific heat on nanometric samples show reduced magnetic contributions respect to the bulk alloy with ?cmax around 0.45 J/molK. The results are explained by the influence of magnetic inhomogeneities and disorder of the alloys enhanced by the milling process in the ensemble of nanoparticles.
关键词： Specific heat,Ferromagnetic,Spin glass,Magnetic properties,Yb alloys
更新于2025-09-23 15:21:21
-
Observation of Optical Band-Gap Narrowing and Enhanced Magnetic Moment in Co-Doped Sol–Gel-Derived Anatase TiO <sub/>2</sub> Nanocrystals
摘要： The magnetic behavior of TiO2 and doped TiO2 nanocrystals has been a challenge due to the unambiguous nature of defects present in oxide semiconductors. Here, a simple, low-temperature sol?gel method is developed for the synthesis of low-dimensional and highly efficient stable anatase TiO2 nanocrystals. The X-ray powder diffraction pattern and Raman spectra confirm the formation of a single-phase anatase structure of TiO2. High-resolution transmission electron microscopy studies reveal the crystalline nature of the sol?gel-derived nanocrystals. The increase in lattice parameters together with the shifting and broadening of the most intense Eg(1) mode in micro-Raman spectra of Co-doped TiO2 nanocrystals indicate the incorporation of Co in TiO2. Shifting of the absorption edge to the visible region in UV?visible spectra indicates narrowing of the band gap due to Co incorporation in TiO2. X-ray photoelectron spectra confirm the presence of Co2+ and Co3+ in Co-doped TiO2 samples. Oxygen vacancy defects lead to the formation of bound magnetic polarons which induces a weak ferromagnetic behavior in air-annealed 3% Co-doped TiO2 at room temperature. It is observed that irrespective of the dopant ion, whether magnetic or nonmagnetic, the overlapping of bound magnetic polarons alone can induce ferromagnetism, while the magnetic impurities give rise to an enhanced paramagnetic moment for higher Co concentrations. A detailed understanding on the variation of these magnetic properties by estimating the concentration of bound magnetic polarons is presented, which is in corroboration with the photoluminescence studies. The observed band-gap narrowing in Co-doped TiO2 nanostructures and the mechanism underlying the magnetic interactions associated with the magnetic impurity concentration are advantageous from an applied perspective, especially in the field of spintronic and magneto-optic devices.
关键词： spintronic,magnetic moment,nanocrystals,optical band-gap narrowing,TiO2,magneto-optic devices,Co-doped,sol?gel
更新于2025-09-23 15:21:21
-
Nonequilibrium Magnetic Oscillation with Cylindrical Vector Beams
摘要： Magnetic oscillation is a generic property of electronic conductors under magnetic fields and widely appreciated as a useful probe of their electronic band structure, i.e. the Fermi surface geometry. However, the usage of the strong static magnetic field makes the measurement insensitive to the magnetic order of the target material. That is, the magnetic order is anyhow turned into a forced ferromagnetic one. Here we theoretically propose an experimental method of measuring the magnetic oscillation in a magnetic-order-resolved way by using the azimuthal cylindrical vector (CV) beam, an example of topological lightwaves. The azimuthal CV beam is unique in that, when focused tightly, it develops a pure longitudinal magnetic field. We argue that this characteristic focusing property and the discrepancy in the relaxation timescale between conduction electrons and localized magnetic moments allow us to develop the nonequilibrium analogue of the magnetic oscillation measurement. Our optical method would be also applicable to metals under the ultra-high pressure of diamond anvil cells.
关键词： Topological lightwaves,Magnetic oscillation,Cylindrical vector beams,Nonequilibrium measurement,Fermi surface geometry
更新于2025-09-23 15:21:21
-
Enhanced Fluorescence Emission and Magnetic Alignment Control of Biphasic Functionalized Composite Janus Particles
摘要： Janus particles, particles that have two distinct aspects on their surface or interiors, have attracted much attention due to their potential for application. For the application of Janus particles to high-resolution displays, and as light sources for optical circuits and fluorescent probes, the Janus particles should be nanosize to ensure high-resolution display and analysis, responsive to external stimuli, and highly fluorescent. However, it is still a challenging issue to develop such highly fluorescent nanoscale Janus particles and control their alignment. Magnetoresponsive Janus particles, of which the orientation can be controlled by an external magnetic field, are prepared by the simple introduction of polymer-coated magnetic nanoparticles (NPs) into the hemispheres of Janus particles. If these magnetoresponsive Janus particles can be combined with a strong fluorescence system, then they could be ideal candidates as components of the previously mentioned applications. In the present study, Janus particles are prepared with a fluorescent dye and gold nanoparticles (Au NPs) on one side. The optical properties of the resulting particles are assessed and discussed. Furthermore, the response of composite Janus particles containing dyes, Au NPs, and iron oxide NPs to an external magnetic field is discussed.
关键词： fluorescence enhancement,LSPR,magnetic alignment,Janus particles
更新于2025-09-23 15:21:21
-
Tuning optical and magnetic properties of nanocrystalline BaTiO3 films by Fe doping
摘要： Fe-doped BaTiO3 is a promising multiferroics material due to its appealing physical properties and potential applications in sensors, transducers and non-volatile memories and multilayer capacitors. Herein, Fe-doped BaTiO3 nanocrystalline films were deposited on silicon substrates by chemical solution route. The relation between Fe content and the optical and magnetic properties of the samples was analyzed. X-ray diffraction data show that the films are tetragonal with P4mm space group. The atomic force microscopy measurement indicates that the film surface roughness increases with Fe composition. The optical response behavior of the films was investigated by Adachi’s dielectric function model with fitting ellipsometric spectra in the photon energy 1.5–4.13?eV. With increasing Fe content, the real part of dielectric functions gradually decreases in the transparent region. Moreover, EOBG (the optical band gap) is reduced with increasing Fe composition x, and the relationship between them is EOBG = (3.817–1.440 × x) eV. All Fe-doped films show weak ferromagnetism coming from the bound magnetic polarons and exchange interaction between oxygen vacancies and Fe3+ in the films. When iron content x exceeds 0.06, the magnetization values of the samples exhibit an unsaturated characteristic at more than 3000 Oe magnetic fields, which is due to the competition between the ferromagnetism and the antiferromagnetism of two Fe3+ ions superexchange. These results suggest that optical and magnetic properties of Fe-doped BaTiO3 nanocrystalline films can be changed by Fe composition.
关键词： multiferroics,optical properties,Fe-doped BaTiO3,magnetic properties,chemical solution route
更新于2025-09-23 15:21:21
-
Optimized quasi-optical cross-polarization scattering system for the measurement of magnetic turbulence on the DIII-D tokamak
摘要： Simulations and laboratory tests are used to design and optimize a quasi-optical system for cross-polarization scattering (CPS) measurements of magnetic turbulence on the DIII-D tokamak. The CPS technique uses a process where magnetic turbulence scatters electromagnetic radiation into the perpendicular polarization enabling a local measurement of the perturbing magnetic ?uctuations. This is a challenging measurement that addresses the contribution of magnetic turbulence to anomalous thermal transport in fusion research relevant plasmas. The goal of the new quasi-optical design is to demonstrate the full spatial and wavenumber capabilities of the CPS diagnostic. The approach used consists of independently controlled and in vacuo aiming systems for the probe and scattered beams (55-75 GHz).
关键词： cross-polarization scattering,magnetic turbulence,quasi-optical system,DIII-D tokamak
更新于2025-09-23 15:21:21
-
Noise mitigation methods for ion detectors operating with a direct view of high temperature plasmas
摘要： We have developed an ion current measurement instrument with a direct view of a plasma that reduces the particle and radiation-induced noise current it detects by over three orders of magnitude, from tens of microamps to tens of nanoamps. This is accomplished using electric ?elds, magnetic ?elds, and physical shielding that limit the ?ux of particles and radiation into the instrument and suppress the secondary electrons produced within it by particle and radiation impact. Operation of this detector in various con?gurations, without an ion beam, has allowed identi?cation of the sources of noise current. In our experimental setup, the largest noise contributors were found to be plasma ions and photoelectric emission due to UV radiation.
关键词： high temperature plasmas,magnetic fields,electric fields,ion detectors,physical shielding,noise mitigation
更新于2025-09-23 15:21:21
-
Effect of Static Magnetic Field on the Evolution of Residual Stress and Microstructure of Laser Remelted Inconel 718 Superalloy
摘要： As a typical additive manufacturing technique, direct energy deposition is restricted from further application due to the presence of residual stress and the structural deformation. Thus, minimizing the residual stress plays a crucial role in additive manufacturing. In this work, a transverse static magnetic field is introduced in the laser remelting of Inconel 718 superalloy to investigate the effects on residual stress and microstructural change. The x-ray diffraction technique was used to examine the residual stress variation. Optical microscope and scanning electron microscope were applied to observe the microstructure evolution. It was found that the compressive residual stress of the remelted region was notably reduced from 392.50 to 315.45 MPa under the effect of the magnetic field of 0.55 T. Furthermore, it was observed that the average dendrite spacing was reduced by about 32% under the magnetic field. During the laser remelting process, the imposed electromagnetic force minimized the flow field within the molten pool, inhibiting the heat transfer and minimizing the cooling rate. These directly reduced the residual stresses. Based on research findings, the magnetic field can be a potential method to eliminate the residual stress in laser additive manufacturing components.
关键词： laser direct deposition,static magnetic field,Inconel 718 superalloy,laser remelting,residual stress,thermoelectric magnetic force
更新于2025-09-23 15:21:01
-
Morphology and magnetic properties of grain-oriented steel scribed using different picosecond lasers
摘要： Micro-scribing experiments were conducted to investigate the characteristics of the associated ablative behavior and the improvements to the magnetic properties of grain-oriented steel using both a 532 nm and a 1064 nm wavelength ultra-fast picosecond laser. Ablative morphological characteristic analysis and elemental analysis were carried out using a 3D confocal microscope, a scanning electron microscope, and energy-dispersive spectroscopy. The damage mechanisms were analyzed by comparing the ablation morphologies. Furthermore, an iron loss tester and magnetic domain observation instrument were used to analyze the dynamic hysteresis loop, macroscopic magnetic property parameters, and to observe the microscopic structure of the magnetic domains. The magnetization behavior, loop characteristics, and magnetic domain refinement mechanisms were discussed. The results indicated that the magnetic domains were clearly refined and that the magnetic properties were significantly improved after picosecond laser scribing of the grain-oriented steel. The sample scribed using an ultra-fast wavelength 532 nm laser was more effectively scribed: the magnetic domain was slightly more refined, the iron loss was reduced by 15.73%, the coercivity was reduced by 24.42%, the residual magnetism was reduced by 20.8%, and the relative permeability was increased by 10.3%. The surface was of a high quality, but there were traces of stress damage caused by high-pressure steam in the scribed area. The 1064 nm wavelength ultra-fast laser clearly showed the effects of heat accumulation in the scribed area. Defects due to thermal damage were more common. The improvement to the macroscopic magnetic properties depended largely on the surface quality of the scribing and the penetration depth of the residual stress in the sample.
关键词： Magnetic domains,Laser surface treatment,Scanning electron microscopy,Iron core loss,Magnetic properties,Grain-oriented silicon steel
更新于2025-09-23 15:21:01
-
A 0.5-T pure-in-plane-field magnetizing holder for in-situ Lorentz microscopy
摘要： A side-entry specimen holder capable of applying a 0.5-tesla in-plane magnetic-induction field for in-situ transmission electron microscopy was developed. Three miniaturized electromagnets with 300 × 300-μm pole area and 180-μm pole gap are stacked along the electron-beam path in the holder. The middle magnet is used for magnetizing the specimen, which is inserted into the pole gap by using a 40-μm-width cantilever for atomic-force microscopy. The upper and lower magnets are used to keep the electron beam parallel to the optical axis. Magnetic-field magnitude was determined on the basis of experimentally measured electron-deflection angles and induction-field profiles along the electron-beam path calculated by finite element electromagnetic simulation. Magnetization reversal in 300-nm-thick Nd-Fe-B magnets from the saturated state was in-situ observed by using the holder and a 1-MeV cold-field-emission transmission electron microscope. The observation revealed that domain-wall pinning occurred in different manners at the c-plane and non-c-plane grain boundaries. The holder was thereby shown to be useful for analysis of magnetization-reversal behaviors of hard magnetic materials.
关键词： In situ transmission electron microscopy,Specimen holder,Magnetic domains,Finite element method,Lorentz microscopy,Hard magnetic material
更新于2025-09-23 15:21:01