共查询到20条相似文献,搜索用时 78 毫秒
1.
《Photonics and Nanostructures》2014,12(5):447-459
Problem of homogenization of nanostructured media in magnetic field has been considered. Possibility of introduction of effective material parameters dielectric permittivity and magnetic permeability for three classes of media such as magnetic metal nanostructures, film metal–dielectric composite media and 3D-nanocomposites on the base of opal matrices has been investigated. It has been stated that the introduction of effective parameters far from magnetic resonance conditions is possible at millimeter waveband frequencies. Strict introduction of effective magnetic permeability of nanostructured media near magnetic resonance is not possible. 相似文献
2.
A composite medium consisting of two sublattices of dielectric spherical particles of high permittivity and different radii
embedded in a dielectric matrix of smaller permittivity are considered. It has been shown that such a composite medium reveals
properties of an isotropic double negative media (DNG) in a limited frequency range, when resonance oscillations of HIII mode in one kind of particles and EIII mode in another kind of particles are excited simultaneously. The EIII resonance and the HIII resonance give rise to the magnetic dipole momentum and the electric dipole momentum correspondingly. Averaging the magnetic
momentum and the electric momentum over the cells belonging to the appropriate spherical particles gives the negative permittivity
and permeability. The model of diffraction of a plane electromagnetic wave on a dielectric sphere is presented and compared
with the mixing rule based consideration. The results obtained are rather close. Distribution of the electromagnetic wave
outside the sphere is calculated. Influence of the dispersion of the sphere size and the dielectric permittivity on the effective
parameters of the DNG material is estimated. 相似文献
3.
E. A. Petrzhik E. S. Ivanova V. I. Alshits 《Bulletin of the Russian Academy of Sciences: Physics》2014,78(10):1052-1057
Changes are found in the microhardness and dielectric permittivity of triglycine sulfate (TGS) crystals after magnetic treatment in a permanent magnetic field or in the scheme of electron paramagnetic resonance (EPR) using the Earth’s magnetic field. The temporal kinetics of microhardness reduction and the rise in dielectric permittivity (as along with their recovery) are nearly identical. The effects disappear when the crystal’s axis of symmetry is parallel to the static magnetic field in both variants of exposure. 相似文献
4.
E. Muhammad Abdul Jamal P. Mohanan P. A. Joy Philip Kurian M. R. Anantharaman 《Applied Physics A: Materials Science & Processing》2009,97(1):157-165
Nickel–rubber nanocomposites were synthesized by incorporating ferromagnetic nickel nanoparticles in a natural rubber as well
as neoprene rubber matrix. Complex dielectric permittivity and magnetic permeability of these composites were evaluated in
the X-band microwave frequencies at room temperature using cavity perturbation technique. The dielectric loss in natural rubber
is smaller compared to neoprene rubber. A steady increase in the dielectric permittivity is observed with increase in the
content of nickel in both the composites. The magnetic permeability exhibits a steady decrease with increase in frequency
and magnetic loss shows a relaxation at 8 GHz. The suitability of these composites as microwave absorbers is modeled based
on the reflection loss which is dependant on the real and imaginary components of the complex dielectric permittivity and
magnetic permeability. 相似文献
5.
Propagation characteristics of a high-power electromagnetic wave through an inhomogeneous magnetized plasma is investigated. Considering the momentum transfer equations for electrons and ions and taking into account the ponderomotive force, the distribution of electron density and dielectric permittivity are obtained. Using non-linear dielectric permittivity and Maxwell's equations in the absence of external current and charge densities, non-linear wave equations are achieved. The results indicate that the external static magnetic field can modify the profiles of both the electric and magnetic fields. It is also shown that the external static magnetic field enhances the amplitude of the electron density and the non-linear dielectric permittivity. 相似文献
6.
The effect of a constant magnetic field on the dielectric properties of triglycine sulfate crystals has been investigated. It has been shown that, after the magnetic treatment of the crystal (2 T, 20 min), the hysteresis loop becomes narrower; i.e., the coercive field decreases, and the dielectric permittivity changes in the region of the phase transition. It has been found that the observed effect is anisotropic with respect to the orientation of the crystal in a magnetic field and occurs when the vector of magnetic induction is perpendicular to the polar axis of the crystal. The relative orientation of the magnetic field and the domain structure determines its sign. The doping of the crystal with chromium makes the effect more pronounced and leads to a change in the kinetics of the magnetically stimulated increase in the dielectric permittivity. 相似文献
7.
《Waves in Random and Complex Media》2013,23(4):459-474
The dielectric permittivity tensor elements of a rotating cold collisionless plasma spheroid in an external magnetic field with toroidal and axial components are obtained. The effects of inhomogeneity in the densities of charged particles and the initial toroidal velocity on the dielectric permittivity tensor and field equations are investigated. The field components in terms of their toroidal components are calculated and it is shown that the toroidal components of the electric and magnetic fields are coupled by two differential equations. The influence of thermal and collisional effects on the dielectric tensor and field equations in the rotating plasma spheroid are also investigated. In the limiting spherical case, the dielectric tensor of a stationary magnetized collisionless cold plasma sphere is presented. 相似文献
8.
Zhao Q Kang L Du B Zhao H Xie Q Huang X Li B Zhou J Li L 《Physical review letters》2008,101(2):027402
Isotropic negative permeability resulting from Mie resonance is demonstrated in a three-dimensional (3D) dielectric composite consisting of an array of dielectric cubes. A strong subwavelength magnetic resonance, corresponding to the first Mie resonance, was excited in dielectric cubes by electromagnetic wave. Negative permeability is verified in the magnetic resonance area via microwave measurement and the dispersion properties. The resonance relies on the size and permittivity of the cubes. It is promising for construction of novel isotropic 3D left-handed materials with a simple structure. 相似文献
9.
Transverse and parallel dielectric permittivity elements have been derived for radio frequency waves in a laboratory dipole magnetic field plasma. Vlasov equation is resolved for both the trapped and untrapped particles as a boundary value problem to define their separate contributions to the dielectric tensor components. To estimate the wave power absorbed in the plasma volume the perturbed electric field and current density components are decomposed in a Fourier series over the poloidal angle. In this case, the dielectric characteristics can be analyzed independently of the solution of the Maxwell's equations. As usual, imaginary part of the parallel permittivity elements is necessary to estimate the electron Landau damping of radio frequency waves, whereas imaginary part of the transverse permittivity elements is important to estimate the wave dissipation by the cyclotron resonances. Computations of the imaginary part of the parallel permittivity elements are carried out in a wide range of the wave frequencies. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
本文通过对高介电常数介质基于介质谐振器理论进行分析,明确了利用高介电常数介质产生负介电常数或负磁导率的途径在于介质中产生具有Lorentz谐振形式的电磁响应的电偶极子或磁偶极子,指出了这种偶极子的产生来源于电磁波在介质中形成的驻波,而左手通带的形成正是由于电偶极子和磁偶极子之间的相互影响,破坏了驻波形成的条件所实现的. 模拟结果表明,通过将尺寸相同,介电常数不同的介质进行组合,使二者电谐振和磁谐振的频率点重合从而实现左手通带,最后利用高介电常数,低损耗的陶瓷进行样品制作并测试,测试结果证实了基于这一原理实
关键词:
全介质左手材料
介质谐振器
磁偶极子
电偶极子 相似文献
11.
A microwave detector based on a self-sustained oscillator circuit is proposed as a means to investigate the real and imaginary
components of the dielectric permittivity of liquid crystals in external electric and magnetic fields. Results are given for
measurements of a 500 MHz oscillator frequency for two types of nematic crystals, 5CBP and MBBA. Fundamental regularities
are identified in the behavior of the microwave dielectric permittivity of samples in electric and magnetic fields. It is
shown that the minimum of the high-frequency dielectric loss in liquid crystals correspond to a situation in which the long
axes of the molecules are oriented parallel to the direction of the microwave electric field.
Zh. Tekh. Fiz. 68, 117–121 (January 1998) 相似文献
12.
L. V. Panina M. Ipatov V. Zhukova A. Zhukov J. Gonzalez 《Applied Physics A: Materials Science & Processing》2011,103(3):653-657
This paper discusses a new type of wire media based on amorphous ferromagnetic microwires. The combination of two effects,
namely, a strong dispersion of the effective permittivity in metallic wire composites (resonance or plasmonic type) and giant
magnetoimpedance effect in wires, will result in unusual property that an effective dielectric response may strongly depend
on the wire magnetization which can be changed with external stimuli: magnetic field, mechanical stress and temperature. 相似文献
13.
This paper aims to study the general conditions under which omnidirectional band gaps (OBGs) are achieved by using heterostructure magnetic photonic crystals (HMPCs). These structures contain periodic layers with alternative dielectric permittivity and magnetic permeability. The proposed design offers the stacking of two magnetic photonic crystals (MPCs), where one MPC has Brewster’s angle at TE polarization and another has the angle at TM polarization. The propagation of electromagnetic waves is investigated by means of the transfer matrix method. Also, the total reflection frequency range for any incident angle and polarization is discussed in this paper. As a conclusion, although each MPC has no OBG individually, the proposed HMPC may contain an OBG. The main advantage of the proposed design is that the obtained OBG is independent of the ambient media refractive index. Therefore, it can be used in engineering omnireflectors in integrated photonics. 相似文献
14.
Yu. V. Kabirov V. G. Gavrilyachenko A. S. Bogatin E. I. Sitalo V. K. Yatsenko 《Physics of the Solid State》2018,60(1):60-63
The dielectric properties of a magnetoresistive conducting two-phase 80%La0.7Sr0.3MnO3/20%GeO2 (wt %) composite have been studied near the percolation threshold in magnetic fields from 0 to 15 kOe at frequencies of the measurement field from 5 kHz to 1 MHz. The samples have inductive impedances; i.e., their permittivities can be considered negative due to a high conductivity in this frequency range. The permittivity increases in magnitude in magnetic field, and the values of the magnetodielectric coefficient reach 23% at room temperature. The reasons for the effect of magnetic field on the dielectric permittivity of samples are discussed. 相似文献
15.
16.
The problem of the transformation of a plane monochromatic wave by a finite-duration sequence of periodic rectangular pulses of the dielectric permittivity and magnetic permeability is solved exactly with integral equations. The expressions for the transformed component of the electric field at any point in space at an arbitrary time are derived and analyzed. 相似文献
17.
Ferydon Babaei 《Optics Communications》2007,278(2):221-231
The concept of local homogenization in the visible and infra-red frequencies is used by estimating the permittivity dyadics of noble metals (Cu, Ag, and Au) in the form of thin film helicoidal bianisotroptic media (TFHBM). Despite the fact that the absorption transitions of dielectric to metal (percolation threshold) in metallic TFHBMs occur at long wavelengths at lower volumetric fraction of metallic particles, at these wavelengths the transition from dielectric to metal in composite relative permittivity scalar occurs at higher volumetric fraction of metallic particles. The latter is responsible for the increase of circular Bragg phenomenon. 相似文献
18.
Engineering the electromagnetic properties of periodic nanostructures using electrostatic resonances
Electromagnetic properties of periodic two-dimensional subwavelength structures consisting of closely packed inclusions of materials with negative dielectric permittivity epsilon in a dielectric host with positive epsilon(h) can be engineered using the concept of multiple electrostatic resonances. Fully electromagnetic solutions of Maxwell's equations reveal multiple wave propagation bands, with the wavelengths much longer than the nanostructure period. Some of these bands are described using the quasistatic theory of the effective dielectric permittivity epsilon(qs). Those bands exhibit multiple cutoffs and resonances which are found to be related to each other through a duality condition. An additional propagation band characterized by a negative magnetic permeability is found. Imaging with subwavelength resolution in that band is demonstrated. 相似文献
19.
Journal of Experimental and Theoretical Physics - Experimental results on temperature dependences of the low-frequency dielectric permittivity of the group of magnetic fluoroperovskites with... 相似文献
20.
Enis Tuncer Adam J. Rondinone Jonathan Woodward Isidor Sauers D. Randy James Alvin R. Ellis 《Applied Physics A: Materials Science & Processing》2009,94(4):843-852
In this paper, we report the dielectric properties of composite systems (nanodielectrics) made of small amounts of mono dispersed
magnetic nanoparticles embedded in a polymer matrix. It is observed from the transmission electron microscope images that
the matrix polymeric material is confined in approximately 100 nm size cages between particle clusters. The particle clusters
are composed of separated spherical particles which comprise unconnected networks in the matrix. The dielectric relaxation
and breakdown characteristics of the matrix polymeric material are altered with the addition of nanometer size cobalt iron-oxide
particles. The dielectric breakdown measurements performed at 77 K showed that these nanodielectrics are potentially useful
as an electrical insulation material for cryogenic high voltage applications. Finally, structural and dielectric properties
of nanocomposite dielectrics are discussed to present plausible reasons for the observed low effective dielectric permittivity
values in the present and similar nanodielectric systems. It is concluded that polymeric nanoparticle composites would have
low dielectric permittivity regardless of the permittivity of nanoparticles are when the particles are coordinated with a
low dielectric permittivity surfactant. 相似文献