Interaction Of Magnetic Field Research Articles

Spin-orbit interaction and snake states in a graphene p-n junction

We study a model of a $p$-$n$ junction in single-layer graphene in the presence of a perpendicular magnetic field and spin-orbit interactions. By solving the relevant quantum-mechanical problem for a potential step, we determine the exact spectrum of spin-resolved dispersive Landau levels. Close to zero energy, we find a pair of linearly dispersing zero modes, which possess a wave-vector-dependent spin polarization and can be regarded as quantum analogous of spinful snake states. We show that the Rashba spin-orbit interaction, in particular, produces a wave vector shift between the dispersions of these modes with observable interference effects. These effects can in principle provide a way to detect the presence of Rashba spin-orbit interaction and measure its strength. Our results suggest that a graphene $p$-$n$ junction in the presence of strong spin-orbit interaction could be used as a building block in a spin field-effect transistor.

The Eddy Current Method of Alloy Drill Pipes Wall Thickness Evaluation: Impact Analysis

The dependences of the surface eddy current probe added voltage at the interaction of the probe magnetic field with an aluminum pipe from the following main interference factors are determined: the pipe wall thickness, the gap between the probe and the surface of the pipe, the electrical conductivity of the material, the curvature of the pipe wall, the presence of areas with a smooth thickness change of the wedge character and a local spherical thinning, axis misalignment with respect to the pipe surface, the lateral misalignment of the probe axis. The problem is solved with the help of the finite element method (FEM). These data are consistent with the experimental results.

Assessment of magnetic field interactions, radiofrequency, and radiation‐induced heating of Zr implants in 7 T MR scanner

Assessment of magnetic field interactions, radiofrequency, and radiation‐induced heating of Zr implants in 7 T MR scanner

Dynamics of a pair of ellipsoidal microparticles under a uniform magnetic field

Under a uniform magnetic field, magnetic particles tend to form chains, clusters or columns due to particle–particle interactions. Non-spherical magnetic particles dispersed in a liquid medium show different rheological properties. However, there is a lack of knowledge about the fundamental mechanism of particle–particle interactions of non-spherical particles under a uniform magnetic field. In this work, we numerically investigate the particle–particle interactions and relative motions of a pair of paramagnetic elliptical particles by using direct numerical simulations to create two-dimensional models that resolve the magnetic and flow fields around the finite-sized particles. The modeling is based on the finite element method and arbitrary Lagrangian–Eulerian approach with full consideration of particle–fluid–magnetic field interaction. The effects of initial position and aspect ratio of the particles are investigated. The results show that the particles spend much more time under global reorientation than local magneto-orientation. Larger initial relative angles and distances, and larger aspect ratios, tend to require more time to form a stable chain. The particle–particle interactions and relative motion of a pair of elliptical particles in this study provide insights into the particle alignment and chaining processes under uniform magnetic fields, which are closely related to the response of magneto-rheological fluids to magnetic fields.

A Novel Electromagnetic Testing Method Based on the Magnetic Field Interaction

The traditional magnetic flux leakage (MFL) method with a single magnetic excitation source has been widely used in engineering practice but fails in long-range (long liftoff distance of the sensor from the surface of the tested object) defect detection, especially when the liftoff distances increase. Thus, we propose a novel electromagnetic testing method based on the magnetic field interaction between the primary magnetic induction field and the secondary field of MFL. The principles of the new method are first introduced, and the method is compared with the common MFL methods; this comparison indicates that the new method has the capabilities of long-range defect detection and signal strength enhancement. Furthermore, a series of simulations and analyses demonstrates that the proposed method is more efficient in defect detection, particularly when the induction magnet is a diamagnetic material, which is independent of the coercive force. Finally, experiments and comparisons were conducted to verify the feasibility and reliability of our proposed method in the long-range defect detection. All results show that the novel method has great promise in widely practical applications in the future.

HTS Bulk Experiments Performed for and Under Space Conditions

In the shadow of dominant long-length high-temperature superconductors bulk HTS show a considerable effort of magnetic engineering application. Bulk HTS are capable of providing easily magnetic fields of several tesla, levitates self- stabilized mirrors or measuring instruments, and can be used as a passive magnetic shield. By simulating space conditions we have been investigated the possible degradation of YBCO material under 160 MeV proton irradiation at a radiative dose of 10-20 krad. We report the successful preparation of an HTS bearing cosmic background radiation, the fabrication and testing of a bulk superconducting device operating in the Columbus laboratory of the International Space Station (ISS). The Magvector/MFX experiment operates the last four years at the ISS. It measures the interaction of a YBCO HTS with the Earth magnetic field using sensitive flux gate sensors in μT level. Laboratory shielding results are given. Dependent on the bulk conductivity at T>T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and T<;T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> the Earth magnetic field interaction causes distortions of the surrounding electromagnetic (EM) field. Possible benefits of HTS bulk devices on applications in space will be discussed.

Quantum coherence of the spin-1 system under an XY spin chain with three-spin interaction

We investigate the performance of quantum coherence and nonlocal advantage of quantum coherence (NAQC) for the central spin-1 system which couple to an XY spin chain with three-spin interaction in a transverse magnetic field. For the case that the central spin system couple weakly to the spin chain, both quantum coherence and NAQC endure sudden change around the critical point of quantum phase transitions when the three-spin interaction is switched off. While there is three-spin interaction, the performances of quantum coherence and NAQC indicate that the critical point has been shifted away from its ordinary position. Therefore, quantum coherence and NAQC can be used to detect the critical point of quantum phase transitions of the XY spin chain for the weak-coupling case. However, three-spin interaction has no obvious effect on the dynamics of quantum coherence and NAQC for the strong-coupling case.

Investigation of the Arc Characteristics of Switching DC Arcs on Hydrogen Containing Gas Mixtures

The characteristics of switching DC current arcs in hydrogen containing gas mixtures under pressure were investigated using a model chamber. The switching device consists of an electro-mechanic double breaker unit with copper contacts. High-speed imaging and spectroscopy were used to observe and to characterize the switching arc. The experiments indicate how the dynamic interaction of an external magnetic field with a high-pressure discharge causes an elongation and twisting of the arc-channel and consequently a voltage increase. Comparative measurements with and without external magnetic field indicate a strong influence of this factor. Cu and N lines together with strongly broadened H lines were observed.

Analysis of Electromagnetohydrodynamic Stagnation Point Flow of Nanofluid Over a Nonlinear Stretching Sheet with Variable Thickness

ABSTRACTPresent study explores stagnation point flow of nanofluid towards a nonlinear stretching sheet of variable thickness in the presence of electromagnetic field and convective heating. The effect of viscous dissipation and Joule heating are also taken into consideration. Novel concept of non-linear radiative heat flux is also considered. The nanofluid is inspired by Lorentz force which is instigated from the interaction of magnetic and electric fields. Using similarity transformation, the governing partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations and then solved numerically by fourth order Runge-Kutta method along with shooting technique. The velocity, temperature and nanoparticle concentration profiles are plotted and analysed corresponding to various pertinent flow parameters. Also, the skin friction and rate of heat and mass transfers at the surface are computed and explained in detail. It is observed that higher wall thickness parameter results in the reduction of velocity, temperature and nanoparticle concentration when velocity power index is less than unity and opposite effect is observed when velocity power index is greater than unity. Due to intensification of electric field, nanofluid velocity is getting retarded and thereby resulting in enhancement of fluid temperature and nanoparticle concentration.

On the Laughlin function and its perturbations

The Laughlin state is an ansatz for the ground state of a system of 2D quantum particles submitted to a strong magnetic field and strong interactions. The two effects conspire to generate strong and very specific correlations between the particles. I present a mathematical approach to the rigidity these correlations display in their response to perturbations. This is an important ingredient in the theory of the fractional quantum Hall effect. The main message is that potentials generated by impurities and residual interactions can be taken into account by generating uncorrelated quasi-holes on top of Laughlin's wave-function. An appendix contains a conjecture (not due to me) that should be regarded as a major open mathematical problem of the field, relating to the spectral gap of a certain zero-range interaction.

Critical phenomena in a two-dimensional ferrimagnetic system: Monte Carlo and Mean-Field Analysis

The critical, first order, and spin compensation behaviors of a ferrimagnetic Ising system, consisting of spins S=3∕2 and Q=5∕2 alternating on a square lattice, have been studied by Monte Carlo (MC) simulations and Mean-Field Theory (MF). The system is defined by a Hamiltonian (H) that contains ferromagnetic next-nearest-neighbors interactions between S spins (J2′) and Q spins (J3′), as well as external magnetic field (h′) and anisotropy (D1′, D2′) interactions. The effects of D1′ crystal and h′ magnetic fields on the critical, double first order transition, and compensation phenomena are analyzed in detail. We found that the existence of a double first order phase transition depends on the temperature and the strength of h′.

Peculiarities of the Gravitational Interaction of Electrical and Magnetic Vortex Fields with Nonlinear Vortex-Free Fields

Within the framework of GRT, the properties of the gravitational interaction of magnetic and electric vortex fields with self-gravitating nonvortex fields are investigated. The possibilities of improving the traversability of the obtained wormholes are examined, along with their asymptotic properties as well as possible observable effects. It is shown that by taking the interaction of these fields into account it is possible to control the physical characteristics of the wormholes.

On interactions of static magnetic fields

Abstract We investigated the interaction energy of a Gilbertian magnetic charge with each of the “point” magnetic field sources. Finally we extrapolated a Dirac string can only be defined if there is at most one Dirac monopole in the medium. If there is only one Dirac monopole/string in the universe, the probability of detecting it is essential zero, such that Dirac’s monopole would remain just a “theorist’s particle”.

Quantum breathers and modulational instability in quantum zigzag spin chains with alternative combination ferromagnetic and antiferromagnetic interactions in an external magnetic field

Abstract Quantum breathers properties and modulational instability in quantum zigzag spin chains with alternative combination ferro-antiferromagnetic interactions are carried out. For a few number of bosons, by using the number states method and numerical diagonalization, the energy spectrum, multi-quantum breathers states and theirs new properties are found. For a large number of bosons, based on the time dependent Hartree approximation and semi-discrete multiple-scale method, we provide a detailed analytical analysis, discuss conditions to obtain solitons bright localized solutions and predict the formation of instability regions in the system. In both configurations, we have constructed quantum breathers states and deduced their quantum energies. Furthermore the modulational instability analysis are done and the formation conditions of appearance instabilities regions predicted by our analytical investigations are found and are in full agreement. Convincing quantitative agreement has been found between the analytical approaches and the numerical simulations for the modulational instability. Experimental data on Rb2Cu2Mo3O12 are parameters used in this work.

Dynamic analysis of electromagnetic compaction of Ag-Cu-Sn multivariate mixed metal powders for brazing

Electromagnetic compaction is a preferable high energy rate forming process for brazing powders to improve the brazing performance. The dynamic analysis of electromagnetic compaction of Ag-Cu-Sn multivariate mixed metal powders was conducted by an electromagnetic-mechanical-thermal coupled model an d electromagnetic compaction tests. The coupled model consists of electrical circuit model, electromagnetic field model, kinematic model of driving board, thermal field model and powder compaction model, it can be used to make a complete dynamic analysis of the electromagnetic compaction including discharge current, eddy current, mutual interactions of magnetic fields, kinematic motion of driving board, compaction densification behaviors and the energy transfer. The electromagnetic compaction tests of Ag-Cu-Sn multivariate mixed metal powders were carried out with a self-developed WG-IV electromagnetic forming machine. The electromagnetic-mechanical-thermal coupled model has good agreement with the electromagnetic compaction tests, and can provide a more accurate dynamic analysis and optimized process design of electromagnetic compaction. An optimization study for higher relative density was completed by the coupled model, and the brazing performance of the optimized brazing sheet with higher relative density was evaluated to be advantageous in the brazing performance tests.

P‐140: Embedded NFC Antenna Display Design for Contactless EMVCo Application

A series of Near Field Communication (NFC) antenna was design for embedded in LCD display module attempt to pass analogue power transfer at 13.56MHz used for EMV@ (Europay, MasterCard and Visa) contactless payment transaction. However it was found that magnetic fields seems to seriously interfere by the display if antenna located behind the display module although increasing magnetic field strength of transmitter. As gradually built up the understanding of magnetic field interaction with LCD panel we find that is difficult to pass EMV@ contactless specification by antenna optimized design only if there’s no display modification. The antenna structure proposed in this paper has been designed and simulated with frequency solver CST 2018. Finally, we proposed a total solution, an optimized NFC antenna transmitter embedded with a modified LCD structure that can pass EMV@ contactless analogue power transfer criteria within specific testing volume.

Transverse spin susceptibilities of doped armchair graphene nanoribbon due to electron-phonon interaction

We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green's function approach in the context of Holstein model Hamiltonian. Specially, the effects of magnetic field and electron-phonon coupling strength on the plasmon modes of armchair graphene nanoribbon are investigated via calculating correlation function of charge density operators. Random phase approximation has been implemented to find the interacting dynamical charge susceptibility. The electrons in this systems interacts with each other by mediation of dispersionless Holstein phonons. Our results show the increase of electron phonon coupling strength leads to decrease intensity of charge collective mode Also the frequency position of the collective mode tends to higher frequencies with electron phonon coupling. We also show that the frequency positions of plasmon mode of armchair nanoribbon are not affected by increase of magnetic field. Furthermore the number of collective excitation mode increases with ribbon width in the presence of electron-phonon interaction. Finally the temperature dependence of static charge structure factor of armchair graphene nanoribbon is studied. The effects of both magnetic field, ribbon width and electron-phonon interaction on the static structure factor are addressed in details.

Optical pumping of ultracold thulium atoms to a lower level of the clock transition and study of their depolarisation

The atomic energy levels corresponding to states with the zero projection of the total angular momentum have a weak sensitivity to certain sources of shifts and, therefore, are widely used in precision spectroscopy. The optical pumping of ultracold thulium atoms to the ground state level with the zero projection of the total angular momentum is described. The population dynamics of this state due to magnetic dipole − dipole interaction in an external magnetic field is studied.

Flexible Magnetoelectrical Devices with Intrinsic Magnetism and Electrical Conductivity

AbstractDevelopment of flexible magnetoelectrical (ME) electronics has encountered huge challenges due to mechanical mismatch, environmental instability, and the weak electrical conductivity of extremely hard neodymium iron boron materials. A series of techniques involving mechanical milling, core–shell structure synthesis, printing electronics, and photonic sintering are developed to achieve composite materials and flexible ME devices demonstrated as sensors, circuit components, printed circuit boards circuits, and interfaces. These devices, which are mechanically compatible with the demands of flexible electronics, offer both excellent magnetism (coercivity &gt;2800 Oe) and electrical conductivity (&gt;41743 S m−1), allowing novel functions and simplified design that benefit from the coexistence and interaction of magnetic and electrical fields. These materials, devices, and process techniques serve as additions to the existing flexible‐electronics framework, and may also inspire development of more innovative ME devices and applications in biology, healthcare, industry, and consumer electronics.

Effect of Rashba and Dresselhaus spin-orbit interactions on a D0 impurity in a two-dimensional Gaussian GaAs quantum dot in the presence of an external magnetic field

Abstract The binding energy of a hydrogenic-like donor complex D 0 placed in a two-dimensional Gaussian quantum dot GaAs semiconductor is determined incorporating the Rashba and Dresselhaus spin-orbit interactions in the presence of an externally applied magnetic field. A unitary transformation is employed to deal with the spin-orbit interactions and their effects are incorporated up to second order in the coupling coefficients. The resulting Hamiltonian is solved variationally using a simple wave function. The results indicate that the Rashba spin-orbit interaction and the confining potential reduce the energy of the donor complex whereas the magnetic field enhances it. Interestingly enough, the binding energy is enhanced by the Dresselhaus spin-orbital interaction in the presence of a magnetic field and while it is reduced in the absence of it. Finally we study the effect of magnetic field and spin-orbit interactions on the magnetic moment and susceptibility.