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POLARIZATION TRANSFORMATION BY A HYPERBOLIC METAMATERIAL ON A METAL SUBSTRATE
摘要： In the present paper we focus on the study of polarization properties of biaxial metamaterial, which consist of alternate ferrite and semiconductor layers, located on an ideally conducted metal substrate. The system is placed into an external magnetic field along the boundaries of the layers. The effective medium theory is applied. Effective linear-to-elliptic polarization conversion has been shown, by means of physical and geometrical parameters of the system under consideration.
关键词： biaxial metamaterial,ferrite,linear-to-elliptic polarization conversion,metal substrate,polarization properties,semiconductor layers,external magnetic field,effective medium theory
更新于2025-09-04 15:30:14
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Influence of Sputtered ZnO and Al:ZnO Top Layers on Magneto-Optic Responses of Yttrium Iron Garnet Films
摘要： Zinc oxide (ZnO) is a promising material for combining with magneto-optic (MO) materials because it can propagate stable exciton-polaritons, with velocities considerably lower than that of photons in a vacuum. This study investigated the in?uence of sputtered ZnO and Al:ZnO top layers on MO responses of a bismuth-substituted yttrium iron garnet (Bi:YIG) ?lm. The ZnO top layer modulated the Faraday rotation and magnetic circular dichroism (MCD) of the Bi:YIG around the exciton resonance wavelength of ZnO at 369 nm. Furthermore, Al-substituted ZnO, which is a conductive ZnO, also changed the MO effects around the exciton resonance wavelength. These results imply that the exciton-polaritons in ZnO affect the MO interaction, because of their considerably low group velocity. The results suggest potential for controlling the MO response via excitons.
关键词： exciton,magneto-optical effect,magnetic garnet,zinc oxide,polariton
更新于2025-09-04 15:30:14
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Nanoparticle-Based Imaging of Clinical Transplant Populations Encapsulated in Protective Polymer Matrices
摘要： A recent clinical trial proves that autologous olfactory mucosal cell (OMC) transplantation improves locomotion in dogs with naturally occurring spinal injuries comparable to human lesions. However, not all dogs respond to the treatment, likely due to the transplantation procedures involving injections of cell suspensions that are associated with cell death, uneven cell distribution, and cell washout. Encapsulating cells in protective hydrogel matrices offers a tissue engineering solution to safely achieve 3D growth of viable transplant cells for implantation into injury sites, to improve regenerative outcomes. It is shown for the first time that canine OMCs (cOMCs) can be propagated with high viability in 3D collagen matrices. Further, a method to incorporate cOMCs pre-labeled with clinical-grade iron oxide nanoparticles into the constructs is described. Intraconstruct labeled cells are visualized using magnetic resonance imaging, offering substantial promise for in vivo tracking of cOMCs delivered in protective matrices.
关键词： magnetic nanoparticle,canine olfactory mucosal cell,cell transplantation,hydrogel,spinal injury
更新于2025-09-04 15:30:14
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<i>In situ </i>soft x-ray absorption spectroscopic study of polycrystalline Fe/MgO interfaces
摘要： In situ soft x-ray absorption spectroscopic study of polycrystalline Fe/MgO interfaces. It is found that at the interface of iron and MgO film, about two monolayers of Fe3O4 is formed. Fe3O4 being the oxide of iron with the highest heat of formation, the reaction appears to be controlled thermodynamically. On the other hand, on the interface with MgO (001) surface, FeO is formed, suggesting that the reaction is limited by the availability of oxygen atoms. Magnetic behavior of the FeO layer gets modified significantly due to proximity effect of the bulk ferromagnetic iron layer.
关键词： FeO,soft x-ray absorption spectroscopy,Fe/MgO interfaces,Fe3O4,magnetic behavior
更新于2025-09-04 15:30:14
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Simulation of the wave-absorbing model of a carbonyl iron?/?silver-coated core–shell structure
摘要： The microwave-absorbing performances of carbonyl iron powder/silver core–shell composite particles are studied on the basis of the electromagnetic scattering theory and the energy conservation law. In addition, a calculation method for re?ection loss of the carbonyl iron powder/silver core–shell composite particles with microwave is proposed. The calculated re?ection loss of the carbonyl iron powder/silver core–shell composite particles is compared with the experimental results. The ?ndings show that the trend of re?ection loss of the carbonyl iron powder/silver composite particles can be predicted which can subsequently provide a relevant reference for future experiment and calculation of the absorbing mechanism of electromagnetic wave-microscopic carbonyl iron powder/silver core–shell composite particles.
关键词： magnetic permeability,Carbonyl iron powder/silver nucleus,wave loss
更新于2025-09-04 15:30:14
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Magnetism of Eu-doped GaN modulations by spinodal nanodecomposition
摘要： By the Monte Carlo method, magnetic properties have been investigated for Eu-doped GaN involving internal nanostructures induced by nanoscale spinodal decomposition, where these nanostructures are spontaneously or artificially formed. In the present simulations, hysteretic and nonhysteretic magnetization curves are observed in the systems with the large-sized and small-sized nanostructures, respectively. These nanostructures affect the blocking temperatures as well. Furthermore, they influence temperature-dependent energy barriers of spin flipping; therefore, the simulations suggest that the magnetization is thermally stable. However, we observe that the blocking temperatures are smaller than the experimental values, which may be due to atomic vacancies.
关键词： magnetic properties,blocking temperatures,Eu-doped GaN,Monte Carlo method,spinodal decomposition
更新于2025-09-04 15:30:14
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Magnetooptical Visualization and Mapping of Magnetic Stray Fields over the Surface of Composite Permanent Magnets Using Gadolinium–Cobalt Amorphous Films
摘要： Stray fields of magnetic systems with a known degree of structural and magnetic nonuniformities have been mapped using indicator amorphous films with a perpendicular anisotropy. The characteristic magnetooptical patterns have been determined, which correspond to the distribution of the magnetic-field component normal to the plane of the indicator films. The theoretical patterns of model magnetic systems that are similar to the studied systems in the degree of the structural and magnetic nonuniformity have been calculated. The validity of the magnetooptical visualization has been confirmed by comparison of the experimental and theoretical patterns. The possibility of the express monitoring of the parameters of the magnetic system has been shown using a laboratory model of a magnetooptical visualizer by the observation of the magnetooptical contrast of gadolinium–cobalt indicator films under the action of an ac magnetic field.
关键词： visualization,mapping,nonuniform magnetic fields,simulation
更新于2025-09-04 15:30:14
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Tunneling ionization of atoms and ions in a linear electromagnetic wave and a constant magnetic field and the “imaginary time” method
摘要： The tunneling ionization of atoms and negative ions in an intense linearly polarized laser ?eld and a constant uniform magnetic ?eld is discussed in the quasiclassical theory framework. We use the “imaginary time” method, where tunneling is described by the classical equations of motion but with purely imaginary “time” to derive the extremal subbarrier trajectory of the photoelectron. This allows to obtain simple analytical expressions for ionization rates in the tunneling regime for an arbitrary angle between a laser beam and a constant magnetic ?eld accounting for the Coulomb interaction of the photoelectron with the atomic core. The resonance case, when the frequency of a monochromatic electromagnetic wave and the cyclotron frequency are equal, is also considered. The limits of weak and strong magnetic ?elds and the expressions for the barrier width and the emission angle of photoelectrons are discussed. It is shown that a magnetic ?eld in the presence of a linear electromagnetic wave increases the barrier width and thus decreases the ionization probability, i.e., stabilizes the bound level.
关键词： linear electromagnetic wave,imaginary time method,atoms,ions,quasiclassical theory,tunneling ionization,constant magnetic field
更新于2025-09-04 15:30:14
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Ab-initio study on electronic and magnetic properties of (Ga,Co) co-doped ZnO
摘要： Using first-principles calculations based on density functional theory within GGA formalism, we have studied the electronic structure and magnetic properties of (Ga,Co) co-doped ZnO system. The effect of impurity distances on ferromagnetic and antiferromagnetic ground state in Co0.056Zn0.944O has been studied. For the closest Co-Co distance, a ferromagnetic ground state with total magnetic moment of ~3.00μμ’ per Co atom has been found. The electronic structure also displays a nearly halfmetallic order. Conversely, for the farthest Co-Co distance an antiferromagnetic ground state was found for Co0.056Zn0.944O. When Zn2+ ions are replaced by Ga ions in Co0.056Zn0.944O, the new (Ga,Co) co-doped ZnO system is more energetically stable. It has also been found that Ga-doping reduces the Co0.056Zn0.944O band gap due to the sp-d exchange interactions, which is in good agreement with the experimental data. Moreover, the Ga-doping changes the nearly halmetallic order of Co0.056Zn0.944O to metallic. Results also show that Ga0.029Co0.056Zn0.915O is still ferromagnetic with a total magnetic moment of ~3.00μμ’ per Co atom. It was also found that the ferromagnetic ground state in (Ga,Co) co-doped ZnO vanishes as Ga concentration increases.
关键词： GGA formalism,(Ga,ab-initio,density functional theory,electronic structure,Co) co-doped ZnO,magnetic properties
更新于2025-09-04 15:30:14
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trilayers
摘要： Chiral domain walls in ultrathin perpendicularly magnetized layers have a Néel structure stabilized by a Dzyaloshinskii-Moriya interaction (DMI) that is generated at the interface between the ferromagnet and a heavy metal. Different interface materials or properties are required above and below a ferromagnetic film in order to generate the structural inversion asymmetry needed to ensure that the DMI arising at the two interfaces does not cancel. Here we report on the magnetic properties of epitaxial Pt/Co/AuxPt1?x trilayers grown by sputtering onto sapphire substrates with 0.6 nm thick Co. As x rises from 0 to 1, a structural inversion asymmetry is progressively generated. We characterize the epilayer structure with x-ray diffraction and cross-sectional transmission electron microscopy, revealing (111) stacking. The saturation magnetization falls as the proximity magnetization in Pt is reduced, whilst the perpendicular magnetic anisotropy Ku rises. The micromagnetic DMI strength D was determined using the bubble expansion technique and also rises from a negligible value when x = 0 to ～1 mJ/m2 for x = 1. The depinning field at which field-driven domain wall motion crosses from the creep to the depinning regime rises from ～40 to ～70 mT, attributed to greater spatial fluctuations of the domain wall energy with increasing Au concentration. Meanwhile, the increase in DMI causes the Walker field to rise from ～10 to ～280 mT, meaning that only in the x = 1 sample is the steady flow regime accessible. The full dependence of domain wall velocity on driving field bears little resemblance to the prediction of a simple one-dimensional model, but can be described very well using micromagnetic simulations with a realistic model of disorder. These reveal a rise in Gilbert damping as x increases.
关键词： perpendicular magnetic anisotropy,Gilbert damping,Chiral domain walls,domain wall dynamics,Dzyaloshinskii-Moriya interaction
更新于2025-09-04 15:30:14