The electroplating process of zinc–nickel system under perpendicular magnetic field from chloride bath

We report the fabrication and testing, at 4.2 K, of an S1IS2FS3 device, where S, F, and I denote a superconductor (Nb), a ferromagnetic material (Permalloy), and an insulator (AlOx), respectively. The F layer covers about one half of the top electrode of the S1IS2 Josephson junction and is positioned off-center. Electric current, Itr, along the S3 electrode can change the magnetization of the F layer in such a way that, for one direction of Itr, a magnetic flux penetrates the junction perpendicular to the layers, whereas for the opposite direction, the perpendicular magnetic flux can be removed. In the former state, the modulation pattern of the Josephson critical current, Ic, in the magnetic field, H, may acquire minimum near H = 0 and restores its usual shape with maximum in the second state. These states can be used for building a compact cryogenic memory compatible with single flux quantum electronics.

The specific topology of the line centered square lattice (known also as the Lieb lattice) induces remarkable spectral properties as the macroscopically degenerated zero energy flat band, the Dirac cone in the low energy spectrum, and the peculiar Hofstadter-type spectrum in magnetic field. We study here the properties of the finite Lieb lattice with periodic and vanishing boundary conditions. We find out the behavior of the flat band induced by disorder and external magnetic and electric fields. We show that in the confined Lieb plaquette threaded by a perpendicular magnetic flux there are edge states with nontrivial behavior. The specific class of twisted edge states, which have alternating chirality, are sensitive to disorder and do not support IQHE, but contribute to the longitudinal resistance. The symmetry of the transmittance matrix in the energy range where these states are located is revealed. The diamagnetic moments of the bulk and edge states in the Dirac-Landau domain, and also of the flat states in crossed magnetic and electric fields are shown.

In the nonrelativistic or relativistic studies of the well-known effect of an infinitely long and infinitely thin solenoid containing magnetic flux Φ, the so-called Aharonov-Bohm (AB) field, in terms of the Dirac's fundamental unit of the magnetic flux , the magnetic flux Φ is usually expressed as a flux quantum number, which can be decomposed into two parts: the integer and the mantissa part. It has been commonly accepted in the literature that the integer part is unimportant and only the mantissa determines all the physical effects. In this paper, by investigating the AB effect on the the sojourn time of a two-dimensional (2D) inverted harmonic oscillator under a perpendicular uniform magnetic field, we show that the sojourn time depends upon the magnitude, rather than solely the mantissa of the magnetic flux quantum number. This then provides an example that can manifest the quantum effect of the integer part of the flux quantum number, the reason behind is explained via gauge transformation.

Recently, pandemics due to new viruses and pathogens have occurred worldwide. New species of viruses and pathogens are less effective than conventional drugs, so more effective treatments are needed. A tailor-made drug discovery research has been actively investigated. Human immune cells have cells called B lymphocytes. If we can analyze the immune mechanism by stimulating B-lymphocytes with antigens, identifying and capturing cells that respond to B-lymphocytes, we can develop highly efficient and low side effect drugs that are effective only against the causative pathogens. Therefore, a method to capture B lymphocytes modified with magnetic beads on magnetic micro-spot arrays by magnetic force is proposed. This method has been shown to be one of the most promising candidates for obtaining accurate genomic data because it can capture cells more rapidly than conventional capture methods. However, this method requires a perpendicular residual magnetic flux density (Mr⊥) in the perpendicular magnetic field that does not allow the B lymphocytes to flow out, because, although it is possible to capture B lymphocytes when a magnet is installed, there is a problem that the B lymphocytes flow out during the subsequent rinsing process. In this study, the plating conditions were investigated to improve the perpendicular magnetic anisotropy of cobalt (Co) based magnetic thin films. Alkaline degreasing and acid-activated copper (Cu) plates were used as substrates for the experiments. CoNiP, CoNiMnP and CoNiMnReP thin films were prepared by electroless plating under the plating bath composition and plating conditions as shown in Table 1. Vibrating sample magnetometer (VSM), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDS) were used for the evaluation. Fig. 1 shows the hysteresis curves of thin films plated with different bath compositions. Perpendicular residual magnetic flux density (Mr⊥) was 25 emu/cc for the CoNiP thin film and 219 emu/cc for the CoNiMnP thin film.The CoNiMnP thin film was found to improve Mr⊥ more than 8 times compared to the CoNiP thin film.It was found that the addition of MnSO4 5H2O improved the Mr⊥.The addition of MnSO4 5H2O may have enhanced Mr⊥ due to the effect of crystal magnetic anisotropy due to the vertical orientation of the c-axis of hcp Co.The perpendicular saturation magnetic flux density (Ms⊥) values were 818 emu/cc and 612 emu/cc for the CoNiMnP and CoNiMnReP thin films respectively.The results showed that the addition of NH4ReO4 reduced the Ms value with maintaining a high Mr⊥ values. Figure 1

The super/normal phase boundary of a two-dimensional (2D) superconducting wire network exhibits characteristic Little-Parks oscillation as a function of the magnetic frustration α (perpendicular magnetic flux piercing the unit cell). The fine structure of the Tc(H) curve reflects the edge of the so-called Hofstadter butterfly spectrum which represents the Bloch band of tight binding electrons on a corresponding 2D lattice under a perpendicular magnetic field. Thus the Tc(H) curve has local maxima at simple fractional values of α, which correspond to stable vortex configurations. In this work, we address the case in which superconducting network is subjected to both a spatially modulated magnetic field and a uniform magnetic field. We measured the dependence of the Tc(H) curve on the field modulation amplitude β (expressed in terms of flux per plaquette) and compared the results with the corresponding Hofstadter butterfly spectra calculated by the matrix diagonalization method. The nature of super/normal transition in 2D superconducting wire networks and Josephson junction arrays has been a subject of extensive studies. The transition at zero magnetic field is generally understood in terms of Kosterlitz-Thouless (KT) transition, the hallmark of which is a “universal jump” at T=TKT of the exponent in the power law current-voltage (I-V) characteristics. The super/normal transition in magnetic fields is governed by subtle competition between the vortex-vortex interactions and the interaction of a vortex with the pinning potentials both periodic and random. In particular, the overall interaction of the vortex system with the periodic potential should be sensitive to the value of α. Various models of phase transitions including, melting and floating of a vortex solid, vortex glass (VG) phase transition, and formation commensurate domains have been theoretically proposed and experimentally pursued. However, there still remain ambiguities in the comparison of the experimental data and theoretical models, so that the nature of superconducting transition in networks has so far been elusive. In order to shed light on the issue, we conducted I-V characteristics measurement in the present system with spatially varying magnetic field which is different from the usually studied case of uniform applied field.

Purpose: To develop the enabling algorithmic techniques which allow forward-peaked adaptive angular meshing to be compatible with angular advection of magnetic fields within a deterministic Grid Based Boltzmann Solver (GBBS) for MRI-guided radiotherapy, and establish appropriate energy adaptive meshing schemes which minimize total numerical degrees of freedom while preserving high dosimetric accuracy for parallel and perpendicular magnetic fields. Methods: A framework to independently adapt angular mesh resolution and basis function refinement of forward and backscattering hemispheres is developed, uniquely accommodating angular advection introduced by magnetic fields. Upwind stabilization techniques to accurately transfer fluence between hemispheres having different discretization are established. To facilitate oblique beam and magnetic field orientations, cardinal forward-peaked mesh orientations were devised to balance requirements for acyclic space-angle sweep ordering, while ensuring the beam predominantly overlaps the forward hemisphere. Energy-dependent fluence anisotropy is investigated, leading to adaptive angular meshing schemes for parallel and perpendicular magnetic fields. Calculated dose distributions were validated against GEANT4 Monte Carlo calculations on slab geometry and anthropomorphic phantoms. Results: Forward-peaked and isotropic energy adaptive angular meshing schemes were developed for parallel and perpendicular magnetic fields respectively, which reduce the number of elements solved by 52.8% and 47.7% respectively compared to static discretization using 32 quadratic elements while retaining over 97% of points passing the gamma 1%/1 mm criterion against Monte Carlo. Conclusions: Techniques to preserve angular upwind-stabilization between hemispheres of a forward-peaked mesh and establish an acyclic directed space-angle sweep graph enabled energy-adaptive meshing schemes to be developed while accurately solving for magnetic fields. This substantially reduced the numerical degrees of freedom while retaining excellent dosimetric agreement with Monte Carlo. These algorithmic underpinnings contribute towards a fast deterministic GBBS for MRI-guided radiotherapy.

In the frame work of the critical state model (CSM), the magnetic response of a thin type-II superconducting disk that carries a radial transport current and is subjected to an applied magnetic field have been studied. To this end, we have studied the process of the magnetic flux-penetration. For a disk initially containing no magnetic flux but carrying a radial current, when a perpendicular magnetic field is applied, magnetic flux-penetration occurs in three stages: (1) the magnetic flux gradually penetrates from the edges of the disk until an instability occurs, (2) there is a rapid inflow of magnetic flux into the disk’s central region, which becomes resistive, and (3) magnetic flux continues to enter the disk, while persistent azimuthal currents flow in an outer annular region where the net current density is equal to J c . Also the behavior of a current-carrying disk subjected to an AC magnetic field is calculated. The magnetic flux, the current profiles and the magnetization hysteresis loops are calculated for several commonly used J c (B) dependences. Finally, the results of the applications of the local field-dependent of the critical current density J c (B) are compared with those obtained from the Bean model.

Magnetic helicity flux gives information about the topology of a magnetic field passing through a boundary. In solar physics applications, this boundary is the photosphere and magnetic helicity flux has become an important quantity in analysing magnetic fields emerging into the solar atmosphere. In this work we investigate the evolution of magnetic helicity flux in magnetohydrodynamic (MHD) simulations of solar flux emergence. We consider emerging magnetic fields with different topologies and investigate how the magnetic helicity flux patterns correspond to the dynamics of emergence. To investigate how the helicity input is connected to the emergence process, we consider two forms of the helicity flux. The first is the standard form giving topological information weighted by magnetic flux. The second form represents the net winding and can be interpreted as the standard helicity flux less the magnetic flux. Both quantities provide important and distinct information about the structure of the emerging field and these quantities differ significantly for mixed sign helicity fields. A novel aspect of this study is that we account for the varying morphology of the photosphere due to the motion of the dense plasma lifted into the chromosphere. Our results will prove useful for the interpretation of magnetic helicity flux maps in solar observations.

Previously, we have investigated a perpendicular magnetic field dependence of Josephson current through Nb/Al-AlOx/Nb junctions, and have found that the Josephson current was irreversibly-modulated when a strong magnetic field was applied in the direction perpendicular to the junction plane. In the present study, we have investigated this perpendicular magnetic field dependence of Josephson current in detail by applying parallel magnetic fields (Hx, Hy) and a perpendicular magnetic field Hz from three directions. A main peak of Fraunhofer diffraction pattern in Ic-(Hx, Hy) characteristics shifted from the origin of (Hx, Hy) plane when the perpendicular magnetic field Hz was applied in the Josephson junction. Furthermore, the main peak did not return to the origin of the (Hx, Hy) plane even though the magnetic field Hz was removed. This meant that the magnetic flux was trapped in a superconducting thin film by application of the magnetic field Hz.

Introduction. In accordance with one of the ways of solving the problem of increasing the smoothness of the vehicles, a controlled suspension is proposed, which is created on the basis of the use of «smart» materials – magnetorheological elastomers, the mechanical properties of which, in particular, damping, can be changed with the help of a controlling magnetic field. This is implemented with the help of the magnetorheological actuator of the suspension control system, which has the form of an elastic bushing of the suspension arm, consisting of several electrically connected in series toroid-like coils (with a core of magnetorheological elastomer). The device is powered by current, the value of which is controlled by the operator, or automatically, depending on the road profile and driving mode. Magnetorheological actuators (elastic bushings) are placed in the holes of the suspension levers instead of standard rubber ones and combined with a controlled current source. Thus, the suspension becomes controllable, which makes it possible to set the necessary vibration damping of the vehicle body to increase its smoothness. Problem. The disadvantage of the previous designs of the magnetorheological actuator is the insufficient amount of the magnetic flux density and the unevenness of its distribution within the elastic bushings. As a result, the damping properties of such controlled suspensions become insufficiently effective, which reduces the possibility of increasing the smoothness of the vehicles. The purpose of the work is to increase the damping properties of the magnetorheological actuator of the vehicle suspension control system, which will increase the control efficiency. The task is to improve the design of the performing magnetorheological device, to carry out calculations and develop a calculation scheme of the study, to determine the average magnetic flux density value and its distribution across the cross-section of the device, to calculate the dependence of the device damping indicator on the magnetic flux density, to compare the damping indicators of the improved device with previously known ones. Methodology. Research tasks were solved on the basis of magnetic field analysis using methods of magnetic field theory and SOLIDWORKS® and FEMM software packages, as well as analysis of the dependence of the damping properties of bushings from magnetorheological elastomers on magnetic flux density. A description of the design and principle of operation of the magnetorheological actuator of the vehicle suspension characteristics control system is given, based on which the calculation scheme was developed. Results. The results of research calculations showed that the average value of magnetic flux density in the proposed design of the device reached 0.85 T, its distribution became fairly uniform, and there were no zones where it was abnormally small. For the first time, the dependence of the damping index on the magnetic flux density of the controlling magnetic field has signs of scientific novelty. It was found that this indicator for the proposed design of the device increased by 22 % compared to previous other designs, which will increase the efficiency of the control system and the smoothness of the vehicle. A positive result was achieved due to the following features of the proposed design of the suspension actuator: the elastic sleeve consists of several coaxially located actuators made of anisotropic magnetorheological elastomer, in which the conglomerates of the ferromagnetic filler during the manufacturing process are located collinear to the direction of the angular deformations of the sleeve and the control magnetic field flux density vector, and the devices have control coils located on their surfaces, which are made of conductive elastic elastomer and electrically connected in a series circuit. Originality. The control method, previous designs and construction of this controlled suspension are protected by patents of Ukraine. Practical value. The direction of further research is to optimize the parameters of the control coils in order to reduce the energy consumption for them and to protect them from overheating. References 20, figures 10.

Coronal mass ejections: a driver of severe space weather

We studied the modulation characteristics of the Josephson current through the Nb/Al–AlO x /Nb tunnel junction by applying an external magnetic field parallel to the junction plane two-dimensionally. We can obtain much information about uniformity in a tunnel barrier through a two-dimensional scan of the external magnetic fields. Furthermore, we also studied the modulation characteristics of the Josephson current when the magnetic field is applied in the direction perpendicular to the junction plane. The Josephson current is reduced when the strong perpendicular magnetic field is applied to the Josephson junction because the magnetic flux is trapped in Nb superconducting thin film. In this paper, we attempt to restore the reduced Josephson current due to the trapped magnetic flux by applying the alternating magnetic field perpendicular to the junction plane. When the perpendicular magnetic field of 150 A/m was applied to the Josephson junction and then the perpendicular magnetic field of 150 A/m was removed, the Josephson current was reduced from 0.6 to 0.45 mA. We restored the Josephson current to 0.5 mA by applying the alternating magnetic field of 100 A/m in the direction perpendicular to the junction plane.

We investigate the real-time dynamics of the chiral magnetic effect in quantum electrodynamics (QED) and quantum chromodynamics (QCD). We consider a field configuration of parallel (chromo)electric and (chromo)magnetic fields with a weak perpendicular electromagnetic magnetic field. The chiral magnetic effect induces an electromagnetic current along this perpendicular magnetic field, which we will compute using linear response theory. We discuss specific results for a homogeneous sudden switch-on and a pulsed (chromo)electric field in a static and homogeneous (chromo)magnetic field. Our methodology can be easily extended to more general situations. The results are useful for investigating the chiral magnetic effect with heavy ion collisions and with lasers that create strong electromagnetic fields. As a side result we obtain the rate of chirality production for massive fermions in parallel electric and magnetic fields that are static and homogeneous.

This paper deals with the design and operating characteristics analysis of electromagnetic suspension (EMS) system. The EMS system consists of a rail, a U-shaped iron core, a high temperature superconductor (HTS) coil, a couple of DC control coils. The HTS coil generates a high magnetic field in the U-shaped iron coil and the rail. As wall as, the U-shaped iron core can be attracted by the coupled high magnetic field. We calculated turns and operating current conditions of HTS coil considering the decay of critical current when perpendicular magnetic fields are applied to the HTS coil. In addition to the design of the HTS coil, a Linear Quadratic (LQ) control method used to design the DC control coils that control the gap distance between the rail and U-shaped iron core. That is, if the gap distance is varied due to the several external disturbances, the DC control coils generated a magnetic field and then keep the constant interval. Thus, the operation of DC control coils would affect the magnetic flux density at the air gap. In this study, we verified the effect of distributions of magnetic flux density using finite element method (FEM) and MATLAB Simulink simulations. Furthermore, we numerically calculated the appropriate control current of DC control coils and the perpendicular magnetic field density on the HTS coil under the external disturbance. Based on these results, the appropriately combined current conditions and control method of EMS system to realize the stable levitation force were achieved.

D.c. magnetization study of fine-filamentary NbTi superconductors