Electric and magnetic excitations in anisotropic broadside-coupled triangular-split-ring resonators

The electric and magnetic resonances of anisotropic broadside-coupled triangular-split-ring resonators are studied for different incident wave excitations. It is shown that the higher order modes exist in both electric and magnetic resonances. It is observed that the incident electric field couples to the magnetic resonance of the designed structure under different excitations. Multiple resonance features due to the anisotropy of the structure are found in the case of different excitations and the nature of these resonances can be regulated as either an electric or a magnetic mode for different frequencies. In this way, a resonant effective permittivity or permeability can be obtained. Hence, controllable properties of the constitutive material parameters (i.e. electric or magnetic resonances, negative values, etc.) can be determined by changing the incident wave excitation.     

A moiré method of visualizing electromagnetic force lines

We propose a simple moiré method of visualizing electromagnetic force lines. The indicial equation is first derived for the tangent (or normal) curve to the electric field (or magnetic induction) around two parallel-line charges (or currents). The derived equation is then shown to have a one-to-one correspondence with that of the moiré fringe formed by two overlapped radial gratings. Since the tangent (or normal) curve to the electric field (or the magnetic induction) corresponds to the direction of the electric (or magnetic) force on a test charge (or current), the radial grating moirés can be used for the visualization of electric (or magnetic) force lines.     

Generation of Electric Field and Net Charge in Hall Reconnection

Generation of Hall electric field and net charge associated initial conditions of plasma density and magnetic field. with magnetic reconnection is studied under different With inclusion of the Hall effects, decoupling of the electron and ion motions leads to the formation of a narrow layer with strong electric field and large net charge density along the separatrix. The asymmetry of the plasma density or magnetic field or both across the current sheet will largely increase the magnitude of the electric field and net charge. The results indicate that the asymmetry of the magnetic field is more effective in producing larger electric field and charge density. The electric field and net charge are always much larger in the low density or/and high magnetic field side than those in the high density or/and low magnetic field side. Both the electric field and net charge density are linearly dependent on the ratios of the plasma density or the square of the magnetic field across the current sheet. For the case with both initial asymmetries of the magnetic field and density, rather large Hall electric field and charge density are generated.     

平面横电磁波模的初值问题

经典理论所描述的电场和磁场处处同相的平面电磁波模并不存在.Maxwell方程组的解依赖于 电磁场的初始值或边界条件,根据不同的初始条件解得的平面电磁波模是不同的.结果表明 ,平面电磁波是横波,在不同的位置,由变化的电场激发的磁场或由变化的磁场激发的电场 振幅不同,电场与磁场的相位差也不同. 关键词： Maxwell方程组 最优微分方程 初始条件 平面电磁波     

Performance parameters for highly-focused electromagnetic waves

New performance parameters are presented for electromagnetic focusing systems of high numerical aperture. The field in the focal region is expanded into either electric/magnetic dipole components, or transverse electric/magnetic components. The treatments can be applied to the important case of electric dipole waves, where the focused polarization distribution is the same as that of an electric dipole. For the limiting case of a system of unity numerical aperture, the transverse focus for a focused electric dipole field is sharpened up by 19% compared with an aplanatic system with plane-polarized input, while at the same time the focal intensity for a given input power is increased by 17%. This should be contrasted with using a pupil filter, in which case, as the focal spot is made smaller the focal intensity also decreases. Pure TE polarization results in an even smaller central lobe. Other inhomogeneous polarizations can also be investigated as linear combinations of electric/magnetic or TE/TM components.     

Magnetic charge and hyperfine splitting in hydrogen

The large spatial size of magnetic charges (or dyons) and parity considerations are used to show that in models of the proton based on dyons the hyperfine splitting must be due to the magnetic moment produced by the electric charge. The contributions of the magnetic monopoles cancel, otherwise the proton would have a large electric dipole moment.     

外场调控下硼磷烯量子点的电子结构和光学性质研究

采用紧束缚近似方法对锯齿状六边形硼磷烯量子点在平面电场和垂直磁场调控下的电子结构和光学性质进行了研究. 研究表明,硼磷烯量子点作为直接带隙半导体,在无外加电场和磁场作用时,能隙不随尺寸的改变而变化. 在平面电场调控下,能隙随电场强度的增加逐渐减小直至消失,平面电场方向几乎不会对硼磷烯量子点体系产生影响, 且随量子点尺寸的增大,能隙消失所需电场强度逐渐减小. 在垂直磁场调控下,表现为体态的能级在磁场作用下形成朗道能级,而能隙边缘处的朗道能级近似为一个平带,不随磁通量的改变而变化,态密度主要分布于朗道能级处. 另外,垂直磁场作用下的光吸收主要是由朗道能级之间的跃迁引起的.     

Spontaneous magnetic moment of flowing superfluid 3He-B in electric fields

An electric field creates a spontaneous magnetic moment in flowing superfluid ³He-B, if the direction of flow is perpendicular to the electric field. This magnetic moment can be detected experimentally with ease, by reversing the direction of the field or the flow.     

点电荷在拓扑绝缘体和导体中感应磁单极

利用电势和磁标势的第一类零阶贝塞尔函数的公式及拓扑绝缘体材料的本构关系, 推导了点电荷在电介质、 拓扑绝缘体和接地导体三个区域的感应电势及感应磁标势. 研究表明: 点电荷 在电介质、 拓扑绝缘体和接地导体中感应了像电荷和像磁单极; 感应像电荷和感应像磁单极的大小和正负除了与场源电荷、 拓扑绝缘体材料参数等因素有关外, 还与像电荷和像磁单极所处的空间位置有关.     

New theorems for bianisotropic media

The general volume equivalence theorem for bianisotropic scatterers is presented, where the equivalent electric and magnetic currents are determined by a pair of coupled vector integral equations. Moreover, using the general volume equivalence theorem and conventional image principle, image theory is developed for a bianisotropic body over an infinite perfect electric or magnetic conducting ground plane.     

Electrostimulation of the magnetoplastic effect in LiF crystals by an “internal” electric field induced during indentation

Indented LiF crystals demonstrate a change in the length of the dislocation rosette rays during their exposure to jointly acting dc magnetic and electric fields. It is shown that magnetic field with induction B = 1 T causes the electrostimulation or electrosuppression depending on the magnitude and direction of the external electric field with respect to the “internal” electric field induced by the charge transfer due to dislocations moving during the indentation.     

Artificial multiferroic heterostructures for an electric control of magnetic properties

The control of magnetism by electric fields is an important goal for future low-power spintronics devices. This partly explains the intensified recent interest for magnetoelectric multiferroic materials and heterostructures. The lack of ferro- or ferrimagnetic–ferroelectric materials with large magnetoelectric coupling between the two orders has spurred intensive research on artificial multiferroics combining ferroelectric or piezoelectric materials and ferromagnets. In this paper we review synthetically the potential of thin-film-based heterostructures in which a magnetic film is in contact with a ferroelectric or piezoelectric one to obtain an electric control of magnetic properties. This electric control either results from a strain-induced magnetoelectric coupling, a charge-driven one, or from the modulation of an interfacial exchange-bias interaction.     

Electromagnetic sources distributed on shells in a Schwarzschild background

In the Introduction we briefly recall our previous results on stationary electromagnetic fields on black hole backgrounds and the use of spin-weighted spherical harmonics. We then discuss static electric and magnetic test fields in a Schwarzschild background using some of these results. As sources we do not consider point charges or current loops like in previous works, rather, we analyze spherical shells with smooth electric or magnetic charge distributions as well as electric or magnetic dipole distributions depending on both angular coordinates. Particular attention is paid to the discontinuities of the field, of the 4-potential, and their relation to the source.     

Scattering polarization in the presence of magnetic and electric fields

The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Limiting cases of scattering under Zeeman effect, and Hanle effect in weak magnetic fields are discussed. The theory is general enough to handle scattering in intermediate magnetic fields (Hanle-Zeeman effect) and for arbitrary orientation of magnetic field. The quadrupolar electric field produces asymmetric line shifts, and causes interesting level-crossing phenomena either in the absence of an ambient magnetic field, or in its presence. It is shown that the quadrupolar electric field produces an additional depolarization in the Q/I profiles and rotation of the plane of polarization in the U/I profile over and above that arising from magnetic field itself. This characteristic may have a diagnostic potential to detect steady-state and time-varying electric fields that surround radiating atoms in solar atmospheric layers.     

Gauge-invariant charged,monopole and dyon fields in gauge theories

We propose explicit recipes to construct the Euclidean Green functions of gauge-invariant charged, monopole and dyon fields in four-dimensional gauge theories whose phase diagram contains phases with deconfined electric and/or magnetic charges. In theories with only either abelian electric or magnetic charges, our construction is an Euclidean version of Dirac's original proposal, the magnetic dual of his proposal, respectively. Rigorous mathematical control is achieved for a class of abelian lattice theories. In theories where electric and magnetic charges coexist, our construction of Green functions of electrically or magnetically charged fields involves taking an average over Mandelstam strings or the dual magnetic flux tubes, in accordance with Dirac's flux quantization condition. We apply our construction to 't Hooft-Polyakov monopoles and Julia-Zee dyons. Connections between our construction and the semiclassical approach are discussed.     

Electric-field and magnetic-field effects on electronic tunneling through magnetic-barrier nanostructures

We have theoretically investigated electric-field and magnetic-field effects on electronic transport properties in nanostructures consisting of realistic magnetic barriers created by lithographic patterning of ferromagnetic or superconducting films. The results indicate that the characteristics of transmission resonance are determined not only by the magnetic configuration and the incident wave vector but also strongly by the applied electric and magnetic fields. It is shown that transmission resonance shifts towards the low-energy region by applying the electric field, and that with increasing the electric field transmission resonance is suppressed for the entire incident wave vector in the magnetic nanostructures with antisymmetric magnetic profile, while for the magnetic nanostructures with symmetric magnetic profile transmission resonance is enhanced for certain incident wave vector. It is also shown that both transmission and conductance shift towards high-energy direction and are greatly suppressed with the increase of the external magnetic field.Received: 20 May 2003, Published online: 11 August 2003PACS: 73.40.Gk Tunneling - 73.23.-b Electronic transport in mesoscopic system - 75.70.Cn Interfacial magnetic properties (multilayers, superlattices)     

Magnetic monopole-like response in metamaterials

In this paper, we explored magnetic monopole-like responses in metamaterials. We designed a sub-wavelength metamolecule that is composed of two dielectric-spaced split-ring resonators. In response to incident waves, the induced magnetic field in the metamolecule resembles that of a two-dimensional magnetic monopole. The magnetic monopole-like response is resulted from electric resonance of the metamolecule, so an electric dipole is always attached. By combining two mirror-symmetric metamolecules with inward and outward radial magnetic fields, magnetic dipole-like responses can be produced just as an electric dipole is formed by separating two opposite-signed electric charges.     

感生电场与动生电场的等效性探究

本文认为在感生电场的情况下,磁场的强弱变化可以引起磁场自身的横向运动,使得线圈中电子相对于磁场发生运动,从而等效为一个动生电场,受到洛伦兹力的作用.借助磁感线模拟磁场的运动方式,得到圆形回路中任意一点与磁场相对运动速度的表达式,进而推得该＂等效动生电场＂中的洛伦兹力.以螺线管为例,验证该方法可以解释感生电场所满足的规律.将感生电场与动生电场的产生原因统一为导体中电子与磁场的相对运动,相应电动势的非静电力统一为洛伦兹力.     

Electro-and magnetostatic fields in media with a nonuniform velocity

A motion-induced magnetic or electric field is calculated by the integral method in the first order of smallness in the ratio of the motion velocity to the speed of light for homogenous media with an arbitrary stationary velocity distribution that are placed in static electric or magnetic fields. For the case of rotation of a sphere, the validity of the results is corroborated by comparing with a solution obtained by joining the fields in the moving and quiescent parts of the medium. Estimates suggest the feasibility of experimentally observing this effect of continuum electrodynamics.     

Electric current control of creation and annihilation of sub-100 nm magnetic bubbles examined by full-field transmission soft X-ray microscopy

The effect of electric current pulses on a sub-100 nm magnetic bubble state in a symmetric Pt/Co multilayer was directly observed using a full-field transmission soft X-ray microscope (MTXM). Field-induced evolution of the magnetic stripe domains into isolated bubbles with their sizes down to 100 nm was imaged under varying external magnetic fields. Electric current pulses were then applied to the created magnetic bubbles, and it was observed that the bubbles could be either created or annihilated by the current pulse depending on the strength of applied magnetic field. The results suggest that the Joule heating plays a critical role in the formation and/or elimination of the bubbles and skyrmions. Finally, the schematic phase diagram for the creation and annihilation of bubbles is presented, suggesting an optimized scheme with the combination of magnetic field and electric current necessary to utilize skyrmions in the practical devices.