On the nature of the influence of an electric current on the magnetically stimulated microplasticity of Al single crystals

A large increase in dislocation mobility in Al single crystals in a static magnetic field in the absence of mechanical loading of the samples is observed when a dc electric current of low density (10⁵–10⁶ A/m²)is additionally passed through the samples. Apparently, the role of the current reduces to depinning of dislocations from strong pinning centers on the surface of the crystal as a result of surface electromigration of defects. This interpretation is supported by the fact that in samples whose surface is insulated by a layer of lacquer the passage of a current through the volume of the crystal does not change the ordinary dislocation mobility level in a magnetic field. It is hypothesized that surface electromigration of defects, which frees dislocations and unblocks dislocation sources, also plays a key role in the physical mechanism of the long-ago discovered macroplastification of metals upon the passage of an electric current through them. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 10, 788–793 (25 May 1998)     

Anisotropy of Giant Nonlinear Magnetoelectric Effects in Hexaferrites with the Magnetoplumbite Structure

We report on the results of investigation of anisotropy of the nonlinear magnetoelectric current effect in M-type hexaferrites with a collinear magnetic ordering at room temperature. It is found that as a result of the passage of a direct electric current in a plane perpendicular to the hexagonal axis of the strontium hexaferrite sample, the saturation magnetization and the anisotropy constant of the material decrease. The change in the magnetic parameters measured using radio spectroscopic methods is found to be proportional to the supplied electric power density; the determined proportionality factors turn out to be several times larger than in the case when the current passes along the axis. We propose a phenomenological theory that explains the observed effects qualitatively.     

Passage of the discharge current through the plasma–electrode interface in the electromagnetic rail accelerator channel

We investigate the phenomena that accompany the acceleration of a free plasma piston (without a striker) in the electromagnetic rail accelerator channel filled with different gases (argon, helium). An intense glow appears in the shock-compressed layer (SCL) in the case of strong shock waves that produce a high electron concentration (~10¹⁷–10¹⁸ cm^–3) behind the front. We have proposed that explosive electron emission (EEE) ensures the high-intensity emission of electrons, the passage of a part of the discharge current through the SCL, and the glow of the SCL. The velocity of a shock wave for which the strong electric field in the Debye layer at the cathode causes EEE from its surface and the passage of the current in the SCL has been determined. It has been concluded that, for high velocities of the plasma, the EEE is a universal mechanism that ensure the passage of a strong current through the interface between the cold electrode and the plasma.     

On the current-voltage characteristic of the oxide process

The transport equations that simulate the passage of the ionic current through an oxide layer under Steady-state conditions have been investigated. These equations are integrated by the method of matched asymptotic expansions. An analysis of the current-voltage characteristic of the system has revealed a region with negative differential conductivity. On this basis, it has been argued that the system is characterized by an instability of the initially uniform distribution of the electric current, which, in turn, leads to the appearance of “current filaments.” The threshold value of this instability is determined.     

Effect of Total Reflection from a Symmetric Two-Channel Device with Fermion Path Nonanalyticity Points Induced by Rashba Spin-Orbit Coupling

The effect Rashba spin-orbit coupling has on transmission coefficient through a symmetric system with fermion path nonanalyticity points is illustrated using the example of a regular polygon-shaped chain. It is shown that the current passage through a device is blocked at the critical spin-orbit coupling values determined by the system’s geometry. At the near-critical spin-orbit coupling values, electron transport is possible only in a narrow range of energies.     

Passage of a high-current relativistic electron beam through matter

A solution is presented for the problem of passage of a high-current relativistic electron beam through matter in the stationary case with one-dimensional geometry. The system of equations describing the passage of the beam consists of the kinetic equation for fast electrons, which considers the effect of the electric field on the magnitude and direction of particle momentum, the equations for the field produced by the space charge generated by thermalized electrons, and relations connecting the conductivity of the medium to the radiation field. Higher-order perturbation theory is used for the solution. The solutions reveal that the distribution of expended energy, thermalized electrons, and other properties of the flow are highly dependent on the density of the incident flux and the conductivity of the medium. It will be shown that linear transfer theory may be applied to calculation of the passage of high-current beams through matter over a wide range of currents and conductivities, if the barrier thickness does not exceed one-half the path length, but cannot be used for calculation of passage through large-thickness barriers, i.e., with thickness comparable to the electron free path length.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 67–74, September, 1979.The author thanks A. N. Didenko and A. M. Kol'chuzhkin for their evaluation of the study.     

Control of Hall angle of Skyrmion driven by electric current

Skyrmions are very promising for applications in spintronics and magnetic memory.It is desired to manipulate and operate a single skyrmion.Here we report on the thermal effect on the motion of current-driven magnetic Skyrmions in magnetic metal.The results show that the magnon current induced by the thermal gradient acts on Skyrmions via magnonic spin-transfer torque,an effect of the transverse and longitudinal Skyrmions drift velocities,thus leading to the effective manipulation of the Hall angle through the ratio of thermal gradient to electric current density,which can be used as a Skyrmion valve.     

On the behavior and stability of a liquid metal in quasi-planar electric contacts

The contacts between conductors formed under relatively low pressures can be treated as quasi-planar. Melting of the material of such contacts upon the passage of electric current is used in some technological processes, but the behavior of liquid in these conditions has not been analyzed. In this study, such an estimate was obtained for specific conditions appearing under electric-pulse compacting (briquetting) of metal shavings. Analysis of derived relations shows that this estimate is valid for any quasi-2D contacts upon passage of a pulsed current of duration from microseconds to milliseconds. It is shown that the spacing between contact surfaces decreases, the liquid metal is extruded in the lateral directions, and the area of the contact and its conductivity increase. Sausage-type magnetohydrodynamic (MHD) instability and overheating instability do not evolve in these conditions because the instability wavelength is larger than the rated thickness of the molten layer; screw MHD instability can appear in slower processes.     

导电突扩管中磁流体管流的数值模拟

采用基于OpenFOAM环境自主开发的低磁雷诺数磁流体求解器,对45°和90°突扩矩形管中液态金属流体在受到垂直流向的外加磁场作用时的速度、感应电流、压力的分布及突扩位置处的MHD三维现象进行数值模拟.结果表明：磁场沿突扩方向时,由于无回流涡,45°比90°突扩管在肩部位置速度分布更优.哈特曼数增大,强射流和突扩结构,在突扩肩部位置引发流动的不稳定性.伴随感应电流的不稳定,流动不稳定发展到突扩位置上游.磁场沿垂直突扩方向时感应电流的三维效应显著.哈特曼数增大,MHD压降显著增大.同方向磁场和相同哈特曼数,不同突扩角度的三维无量纲压力梯度无明显差异.     

Effect of the charge dragging in a graphene-based superlattice under a constant electric field

The effect of a constant electric field on the charge dragging by an electromagnetic wave is studied for graphene-based superlattice. An expression is derived for the electric current density in a graphene-based superlattice under a constant electric field in an approximation of a constant time of relaxation. It is demonstrated that the current as a function of wave intensity is of a nonmonotonous character.     

Change in the electrical resistance of the metallic composite material-steel contact under friction and electric current

The I–V characteristics of the sliding contact of metallic composites of grade 45 steel without a lubricant are presented. Steel-based composites are shown to increase the actual electric-contact area due to the appearance of electric discharges, which provide the main passage of an electric current with a density up to 300 A/cm². Copper-based composites cannot initiate electric-discharge conduction because of the fracture of the contact zone material at a current density higher than 50 A/cm². The electrical resistivity of the contact layer of metallic composites is calculated. It is found that, during friction with a high current density, the electrical resistivity of the contact layer approaches the electrical resistivity of graphite. It is experimentally shown that the actual electric-contact area can be increased by the introduction of a Pb-Sn melt into the friction zone and reaching a current density higher than 300 A/cm² in the contact.     

Radioelectric effect in a superlattice under the action of an elliptically polarized electromagnetic wave

The density of the current associated with the drag of charge carriers in a superlattice by an elliptically polarized electromagnetic wave is calculated. Two cases of the mutual orientation of the Umov-Poynting vector and the superlattice axis, i.e., their parallel and perpendicular orientations, are analyzed. It is shown that, for the parallel orientation, the radioelectric effect can change sign. The influence of the longitudinal dc electric field on the radioelectric effect is investigated under the conditions where a circularly polarized electromagnetic wave propagates along the superlattice axis. The current density is studied as a function of the electric field strength and the electromagnetic wave intensity. It is demonstrated that the direction of the electric current is changed at specific values of the dc field strength and the wave intensity.     

Bloch oscillations of an acoustic field in a layered structure

This study is devoted to experimentally achieving the phenomenon of periodic modulation of the acoustic-wave intensity, which is observed upon passage of an acoustic signal through a quasi-periodic structure and is the acoustic analog of the effect of Bloch oscillations (BO). Ultrasound at a frequency of 1 MHz is used, and a layered structure that consists of alternate plane-parallel glass and water layers serves as a super-lattice. In order to create an analog of the external electric field, the thickness of the water layers was changed inversely with respect to their ordinals. It is shown that the transmission spectrum of such a structure has the form of narrow equidistant peaks (an analog of the Wannier-Stark ladder), and the envelope of a transmitted signal undergoes periodic oscillations (analogous to BO). The experimental results are in good agreement with theoretical calculations performed by the transfer-matrix method.     

Surface waves at the interface between a dielectric and a topological insulator

Surface waves that propagate along the interface between an isotropic linear or nonlinear (of the Kerr type) dielectric and a topological insulator have been studied theoretically. A dispersion relation for surface waves, which are represented by superpositions of TE and TM waves, has been obtained. This hybridization occurs because, upon passage through the interface, the polarization of a surface wave changes, which is caused by an induced surface current (which is transverse to the electric field vector of the wave). The surface current of this kind is characteristic of topological insulators. Expressions for the energy flux transferred by a surface wave have been given.     

Column buckling of doubly parallel slender nanowires carrying electric current acted upon by a magnetic field

Axial buckling of current-carrying double-nanowire-systems immersed in a longitudinal magnetic field is aimed to be explored. Each nanowire is affected by the magnetic forces resulted from the externally exerted magnetic field plus the magnetic field resulted from the passage of electric current through the adjacent nanowire. To study the problem, these forces are appropriately evaluated in terms of transverse displacements. Subsequently, the governing equations of the nanosystem are constructed using Euler–Bernoulli beam theory in conjunction with the surface elasticity theory of Gurtin and Murdoch. Using a meshless technique and assumed mode method, the critical compressive buckling load of the nanosystem is determined. In a special case, the obtained results by these two numerical methods are successfully checked. The roles of the slenderness ratio, electric current, magnetic field strength, and interwire distance on the axial buckling load and stability behavior of the nanosystem are displayed and discussed in some detail.     

On the streamer discharges emitted from the head of a person located in the vicinity of lightning strikes and their possible consequences

In this paper the currents associated with the streamer discharges generated from the head of a person located in the vicinity of a lightning strike are investigated. In the analysis the location of the person with respect to the lightning strike is selected in such a way that only a streamer burst, without the formation of a connecting leader, is emitted from the head. The current associated with these streamer bursts could exceed several hundreds of mA and may last for several hundreds of microseconds. The results of the calculation show that the passage of the streamer currents through the body of the person could create electric fields in the brain large enough to excite neurons. Depending on the strength of lightning flash and the distance to the strike point these streamer bursts can give rise to phosphenes which are a form of visual experience that occurs when the visual cortex is stimulated by electric currents.     

Structural transformation of graphite by arc-discharge

The formation of novel structures by the passage of an electric current through graphite is described. These structures apparently consist of hollow three-dimensional graphitic shells bounded by curved and faceted planes, typically made up of two graphene layers. The curved structures were frequently decorated with nano-scale carbon particles, or short nanotubes. In some cases, nanotubes were found to be seamlessly connected to the thin shells, indicating that the formation of the shells and the nanotubes is intimately connected. Small nanotubes or nanoparticles were also sometimes found encapsulated inside the hollow structures, while fullerene-like particles were often seen attached to the outside surfaces. With their high surface areas and structural perfection, the new carbon structures may have applications as anodes of lithium ion batteries or as components of composite materials.     

A technique for rapid diagnostics of dielectric liquids basing on their high-voltage conductivity

The electrical conductivity of a liquid dielectric is one of its most important properties; however, it is typically measured in the low-voltage range whereas the features of the current passage processes under the effect of strong electric field remain poorly investigated. The paper presents an experimental technique for rapid measurement of the high-voltage conductivity. The current–voltage characteristics obtained with the voltage modulation by a saw-tooth signal underlie the proposed technique. Some examples are given to demonstrate the importance of its application. The experimental data were complemented with the computer simulation of the corresponding processes.     

Effect of an electric field on surface combustion

The effect of an electric field on the surface combustion of both lean and rich stirred gas mixtures was studied. The voltage–current characteristics of a current flow through gas were constructed. It was found that the confinement of surface combustion and a decrease in the temperature of a wire screen over the matrix are possible in the presence of an electric field. A change in the matrix polarity from negative to positive leads to an increase in electrical current in the circuit by an order of magnitude. Upon the arrangement of an impenetrable screen over the matrix, the matrix temperature can increase or decrease with the negative or positive polarity of the matrix, respectively.