Magnetic Direction Research Articles

Incoherent scattering ion line spectra of vortex beams by magnetized ionospheric plasma with bi-Maxwellian distribution

Abstract Incoherent scattering theory is one of the important means of plasma parameter diagnosis. The incoherent scattering of vortex beams carrying orbital angular momentum can bring new incremental information to plasma diagnosis. Based on the angular spectrum theory of Bessel vortex beams and the theory of incoherent scattering, this paper studies the incoherent scattering of the ionospheric magnetized plasma to vortex electromagnetic waves under the bi-Maxwellian distribution along the magnetic field drift. The numerical results show that when the angle between the scattering wave vector and the magnetic field direction is small, the ion spectral lines have an obvious frequency shift. When the angle is close to 90°, the ion line spectra produce harmonic oscillation, and the drift speed restrains this oscillation phenomenon. The linear Doppler shift will shift the spectral line as a whole, while the rotating Doppler shift of the vortex beam will weaken the spectral line oscillation. This work may provide a possibility for further research on the scattering of vortex beams by magnetized plasma and the development of ionospheric plasma irregularities parameter inversion.

5 cm OH Masers in Northern Star Formation Regions

We present a 6.0 GHz excited-state OH maser survey toward 155 northern star formation regions utilizing the Shanghai Tianma Radio Telescope. In total, we detect 44 6.0 GHz OH masers, 8 of which are new detections (one at 6016 MHz, two at 6030 MHz, and five at 6035 MHz). Of these 44 detected 6.0 GHz OH masers, 13 sites exhibit 6030 MHz OH masers, all 44 sites show the 6035 MHz transition, one site (G009.620+0.194) has the only 6016 MHz OH maser, and one site (W3(OH)) shows the only 6049 MHz OH maser. The 6016 MHz OH maser is the first OH maser of this transition detected in star formation regions. Investigations of the association between 6030/6035 MHz OH masers with 1665 MHz ground-state OH, 6.7 GHz methanol, and 22 GHz water masers show that 1665 MHz OH masers are good indicators of 6.0 GHz OH masers (29% detection rate), which is consistent with previous results. The majority (more than 77%) of 6030 and 6035 MHz OH masers are associated with 6.7 GHz methanol and/or 22 GHz water masers. Comparison between our spectra with previous spectra, we find that only two sources remain fairly stable since their discoveries. We identify 80 Zeeman pairs in 32 6.0 GHz OH maser sites with typical magnetic field strengths of less than 10 mG. The magnetic field directions derived from these 32 maser sites with Zeeman pairs are consistent with previous work, which indicates that the 6.0 GHz OH masers may be potential tracers of the large-scale Galactic magnetic field.

Spatial magnetic force and magnetic energy density analysis of microsphere medium in high gradient magnetic fields: a 3D simulation

Abstract High gradient magnetic separation technology is the key technology for green and efficient separation and purification of mineral resources. Existing studies are vague about the division of the attraction and repulsion zones of the medium, and there are fewer explorations of the effect of various conditions on the attraction zones. In this work, a novel method for calculating the magnetic force is derived, which provides an accurate calculation of the 3D magnetic force. The attraction and repulsion zones are divided clearly by analyzing the relationship between the spatial angle of the spherical medium and the magnetic force density per unit volume, with the magnetic force density per unit volume tangent to the spherical surface as the dividing line. The attraction and repulsion zones are divided by β = 30°~35°, and the attraction region accounts for 45%~50% of the total space volume. Furthermore, the influence of different conditions on the attraction zone is studied. It was found that the zone of attraction decreases as one moves away from the spherical medium, which results in an ellipsoid with the effective zone of attraction of the spherical medium having the magnetic field direction as its long axis. The attraction region increases from 45.49% to 49.87% of the space occupied with increasing the relative permeability of the spherical medium. It does not affect the proportion of the attraction zone in space by changing the background magnetic field and the size of the spherical medium, but it will change the depth of the magnetic force. It provides a theoretical basis for the design of high-efficiency magnetic media, and gives a reference for further improving the selection effect of high gradient magnetic separation technology on fine and weak magnetic particles.

Equations of magnetic field of transformer steel sheets

This study described a method for determining the magnetic field in transformer steel sheets for any magnetisation direction. In the proposed approach, limiting hysteresis loops for the rolling and transverse directions were used. These loops, which were determined separately in both directions, were modified depending on the direction of magnetisation. The assumed area of the magnetic field occurrence was divided into elementary segments, and the appropriate components of field strength and flux density were assigned to the edges and elementary segments of the grid dividing this area. The relationships between the flux density and field strength along both the rolling and transverse directions in the elementary segments were introduced into the equations of the magnetic field distribution, which were based on Maxwell’s equations in the integral form. These equations facilitated the determination of changes in the magnetic field, considering the magnetic hysteresis. The correctness of these equations was validated through comparisons of the results of numerical calculations with the analogous results of measurements performed using a laboratory package of transformer sheets.

Designing van der Waals layers for ferromagnetic quantum spin Hall phase

Most theoretically predicted and experimentally confirmed quantum spin Hall effects (QSHEs) are limited to zero-moment magnets. In this study, we theoretically anticipate the QSHE in ferromagnets and the quantum anomalous Hall effect (QAHE) in antiferromagnets through van der Waals stacked layers, where the magnetization direction is confined to the in-plane. We introduce a search rule for constructing ferromagnetic (FM) quantum spin Hall insulator (QSHI) and antiferromagnetic (AFM) quantum anomalous Hall insulator (QAHI) and further predict a real material of the LuN2/GaS/LuN2 van der Waals multilayer by first-principles calculations. Our results demonstrate the superposition and elimination of Chern numbers under mirror symmetry and time-reversal symmetry, and they further indicate that FM QSHI and AFM QAHI can be converted through deflection magnetization. These findings broaden the material class for QSHE and QAHE and propose a scheme for constructing FM QSHI and AFM QAHI.

Research on magnetic field distribution characteristics of 2G-HTS dynamo in superconducting wireless power supply applications

Abstract The high-temperature superconducting (HTS) dynamo injects direct current (DC) into the winging of superconducting machines through non-electrical contact, solving issues such as thermal leakage in traditional current leads and current decay due to flux motion, joint resistance and AC losses. However, it has been observed that the DC output voltage decreases with an increasing air gap between the rotor magnet and HTS stator. To increase the output of the HTS dynamo at a fixed gap, this study employs an efficient numerical model based on the equivalent current method to investigate the magnetic field distribution of the magnets with different structural parameters. The relationship between the magnetic field distribution of the rotor magnet and the open-circuit voltage of the stator is established and extensively validated against simulation modeling and experimental data. Experimental results indicate that the rotor’s magnetic field distribution and the stator’s magnetic field penetration influence the open circuit voltage of the HTS dynamo. Specifically, when the distance between adjacent magnets is large, the magnetic field penetration occurs only on both sides of the stator, causing circuit voltage to increase initially and then decrease with the magnet distance decreases. A reverse point opposite to the magnetic field direction on both sides is generated at the center of the stator when the distance decreases further, which increases the average induced current density, and suppresses the downward trend. By optimizing the magnetic field distribution of the rotor magnets on the stator, the DC output power of the dynamo can be effectively improved. This model and the results contained in this article provide a comprehensive theoretical basis for researchers to compare and optimize their own modeling and experiment of the HTS dynamo.

Observation of field-free spin–orbit torque switching in a single crystalline (Ga,Mn)(As,P) ferromagnetic film with perpendicular anisotropy

We report the observation of field-free spin–orbit torque (SOT) magnetization switching in a single layer of (Ga,Mn)(As,P) ferromagnetic film exhibiting perpendicular magnetic anisotropy. The SOT switching phenomenon is characterized by distinct transitions between two Hall resistance (HR) states during current scans. When subjected to an in-plane bias field, the observed switching chirality in the HR hysteresis loop consistently aligns with SOT induced by spin polarization arising from Rashba- and Dresselhaus-type spin–orbit fields within the tensile-strained crystalline structure of the (Ga,Mn)(As,P) film. Remarkably, in the present experiments, we observe SOT switching even in the absence of an external bias field, and with its chirality depending on the direction of initial magnetization. We attribute this field-free switching to symmetry breaking facilitated by an internal coupling field, the orientation of which is determined by the external field experienced as the magnetization is initialized. Further evidence supporting the presence of such a coupling field includes a shift in the field-scan HR hysteresis depending on the direction of initialized magnetization. Structural analysis reveals a surface layer enriched in Mn and O, indicating the presence of oxide-based magnetic structures that are magnetically coupled to the (Ga,Mn)(As,P) film. The temperature dependence of field-free SOT switching corroborates this explanation, as the internal coupling field disappears above 40 K, consistent with the expected magnetic transition of the Mn3O4 structure. Our discovery of field-free SOT magnetization switching in a single-layer film represents a significant advancement, offering a novel pathway for the development of simpler and more energy-efficient spintronic devices.

A Special Kind of Interplanetary Coronal Mass Ejection

Abstract It is generally believed that Coronal mass ejections (CMEs) have magnetic flux rope structures because of their helical shapes. However, only about 30-40% of interplanetary CMEs (ICMEs) have a local magnetic flux rope structure. The usually explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete magnetic flux rope structure, or some processes destruct these magnetic flux rope structure. Several studies suggest that some ICMEs inherently possess disordered magnetic fields and consequently exhibit no magnetic flux-rope structures. We introduce a special kind of ICMEs. They have low magnetic field magnitude and stable magnetic field direction, relatively fast expansion speed, lower proton temperature and density. Their all three measured magnetic field components are relatively stable. We want to know whether these ICMEs also have magnetic flux rope structures or not. We identified 20 special ICMEs and analyzed their evolution based on their observed characteristics. We took a special ICME as example, which had apparent rope configuration at 1 AU but evolved to a special ICME at 5.4 AU, to illustrated that this kind of ICMEs may come from magnetic clouds (MCs) whose rope structure had been being stretched due to expansion. We inferred that the missing of obvious flux rope structure may be due to the expansion of MCs, not the flank crossing effect. However, more than 50% of the events were associated with dominant x-component of the magnetic filed, which indicates a leg crossing. Therefore, the detection of part of these special ICMEs may also be results of leg crossing effect.

The effect of hydrostatic pressure on electric transport properties of bulk black arsenic phosphorus single crystals

Black arsenic phosphorus AsxP1-x (b-AsxP1-x), as a novel two-dimensional material, has recently attracted great attention owing to their exotic physical properties. Here, we report a systematic study of the pressure dependence of electric transport properties in b-As0.75P0.25 single crystal. At ambient pressure, b-As0.75P0.25 shows an extrinsic semiconducting behavior, and the magnetoresistance (MR) has an obvious dependence on the magnetic field direction, resulting in an anisotropic MR effect. With the applied hydrostatic pressure, the crystal exhibits a tendency towards metallic behavior, whereas at pressures above 1.0-1.3GPa, the resistivity starts to increase at low temperatures. This picture is simultaneously supported by low temperature high-pressure MR measurements. Taking into account the negative and positive contributions to the MR, we have been able to propose a modified two-band model to describe the MR properties. The analysis of the MR data reveals the coexistence of high-mobility electrons and holes with nearly identical carrier densities. Above the critical pressure, the density of the electron that remains dominant increases with pressure while the electron mobility decreases significantly under pressure, leading to a transition in resistivity. This work has implications to both the fundamental understanding of bulk b-As0.75P0.25 and studies of two-carrier correlated materials.

Numerical simulations of MHD effect on convective heat transfer characteristics in bubbles coalescence process

In this numerical study, the coalescence characteristic of a coaxial bubble pair and its influence on the liquid-to-wall convection heat transfer are investigated under different magnetic field intensities, magnetic field directions, and wall confinement ratios by adopting the volume of fluid (VOF) method. The results reveal that in the direction of heat flow, the toroidal vortices around the bubbles are dampened and even vanish completely after applying the spanwise magnetic fields, while the toroidal vortices only get away from the hot wall in the presence of the transverse magnetic fields. Correspondingly, the convective heat transfer on the hot wall is suppressed to varying degrees under the magnetic fields in different directions. The inhibitory action of the magnetic field on the heat transfer becomes stronger with the decreasing separation distance (s*) between the coaxial bubbles. The total increment of heat transfer (Nu*) is a decreased function of Hartmann number (Ha) and that decreased amplitude of Nu* under the spanwise magnetic field is nearly twice that of the transverse magnetic field. Additionally, the variations of Nu* are independent of the wall confinement ratio (Cr) for Ha < 400, while the Cr has an obvious effect on Nu* for Ha > 400 and the values of Nu* are considerably smaller at a larger Cr. The results about the effect of the magnetic field and wall confinement on the two-phase heat transfer can be referenced in the cooling system design of fusion reactor.

Research on magnetic force of magnetic seal in aero-engine

Aiming at the magnetic seal in an aero-engine accessory, the range of magnetic force required for the normal operation of the magnetic seal is analyzed. The finite element analysis method based on the Maxwell stress tensor method is used to calculate the magnetic force between the dynamic ring and the magnetic static ring in the magnetic sealing system. The magnetic force under different magnetization modes and gaps is tested by the magnetic measuring test bench, which verifies the correctness of the magnetic calculation method. The effects of permanent magnet material, permanent magnet magnetization direction, magnetic seal structural parameters, and working conditions on the magnetic force between the dynamic ring/magnetic static ring in the magnetic seal are analyzed. Under the same structure, the magnetic force of NeFeB35, SmCo28, Alnico5, and Ferrite as magnetic static rings is compared. The results show that NdFeB35 has the largest magnetic force, SmCo28 is second, Alnico5 and Ferrite are relatively small, and their magnetic forces are about 1/4 to 1/5 of the first two materials. When the rotor or the casing is moving axially, NeFeB35 and SmCo28 materials with large magnetic force should be selected to meet the normal working requirements. Under the same material, the magnetic forces of axial, radial, and radiative magnetization modes are compared. the ratio of magnetic force under axial, radiative, and radial magnetization is about 2.3:1.1:1. If NeFeB35 and SmCo28 materials are axially magnetized, their magnetic forces will exceed the allowable range, which will increase the seal wear. The increase in the inner diameter of the dynamic ring and the gap between the dynamic ring and the magnetic static ring causes a decrease in the magnetic force. The increase in temperature affects the magnetic properties of permanent magnetic material, which leads to the decline of magnetic force between the dynamic ring and the magnetic static ring. The increase in rotor speed leads to the acceleration of the fluctuation frequency of the magnetic force. Still, the maximum and minimum values of the magnetic force under different speeds remain unchanged, and the maximum fluctuation rate is less than 3%. According to the analysis results, the fitting formula of magnetic force calculation is presented by the orthogonal test and the least squares method.

Spin-Selective Charge Transfer-SERS Driven Label-Free Enantioselective Discrimination of Chiral Molecules on Ag Nanoparticle-Decorated Ni Nanorod Arrays.

Enantioselective discrimination is critical in several fields, particularly in pharmaceutics and clinical drug research. Chiral molecules possess unique charge transfer properties, showing an enantioselective preference for electron spin orientation when interacting with the magnetic surface. Here, we developed spin-selective charge transfer (SSCT)-based label-free surface-enhanced Raman scattering (SERS) achiral magnetic substrates for the enantioselective discrimination of chiral molecules without creating asymmetric chiral adsorption sites. The e-beam-based glancing angle deposition (GLAD) technique was utilized to construct achiral magnetic surface-enhanced Raman scattering (SERS) substrates by decorating Ag nanoparticles over Ni nanorods. SERS spectroscopy was carried out on significant enantiomers, including cystine, alanine, and DOPA (l-3-(3,4-dihydroxyphenyl) alanine). An external electromagnet was used to manipulate the magnetic substrate's spin polarization by altering the magnetic field's direction. Subsequently, SERS spectra were acquired. Based on the magnetic field's direction, there is a complementary variation in the intensities of SERS spectra of the enantiomers. The SSCT process between molecule-metal complexes synergized with the magnetic field direction to control the electron spin, leading to SERS-based enantioselective discrimination. This label-free, easy, yet practical approach offers a characteristic paradigm shift from the recent complex approaches for chiral detection and separation.

Multiple Weyl fermions and topological phase transition in two-dimensional ferromagnetic CrS2.

The study of topological states in two-dimensional (2D) systems, especially with magnetic properties, has recently gained significant attention owing to their potential in spintronics and nanotechnology. Here, we propose a 2D ferromagnetic (FM) material, CrS2, which hosts multiple Weyl points (WPs) and can undergo a topological phase transition by rotating the magnetization direction. Based on first-principles calculations, we identify distinct Weyl points around the Fermi level: W1, W2, and W3. These points appear in both spin channels and include various types: type-I, type-II and type-III WPs. Corresponding Fermi arcs are clearly observed at the material edges. CrS2 displays a FM ground state with the easy magnetization direction along the c-axis. When the magnetization direction is rotated in the x-y plane, the W1 and W3 points open gaps, with the gap values remaining the same in all magnetization directions. The W2 can maintain a crossing at specific in-plane magnetization directions, indicating that the material retains its Weyl state. Additionally, we examine the effects of biaxial and uniaxial strains on electronic properties. Weyl points remain stable under biaxial strain of less than ±5%, but they disappear under uniaxial strain. In summary, our work proposes a 2D FM material with multiple coexisting Weyl fermions, where the topological states can be tuned by an external magnetic field.

High Electrical Conductance in Magnetic Emission Junction of Fe3GeTe2/ZnO/Ni Heterostructure via Selective Spin Emission through ZnO Ohmic Barrier.

The insulator is essential for magnetic tunneling junction (MTJ) that increases magnetoresistance (MR) by decoupling magnetization directions between two ferromagnets. However, wide bandgap tunnel barrier blocks the thermionic emission of electrons, significantly reducing electrical conductance through MTJ. Here, a magnetic emission junction (MEJ) is demonstrated for the first time using an Fe3GeTe2 (FGT)/ZnO/Ni heterostructure with very high electrical conductance. The conduction band of ZnO (electron affinity 4.6eV) aligns with Fermi levels (EF) of FGT (4.47eV) and Ni (4.58eV) ferromagnets and forms an Ohmic barrier, enabling free spin-electron emission through ZnO barrier and high electrical conductance. In contrast to the typical positive MR in MTJ by majority spin tunneling, negative MR is observed in FGT/ZnO/Ni MEJ. The minority spin electrons of Ni, with maximum states near the EF, are dominantly emitted to FGT over the ZnO barrier, while majority spin electrons of Ni, with maximum states below the EF, are blocked by it. In the FGT/FGT/ZnO/Ni heterostructure, the MR ratio is further increased by combining positive and negative MR at the MTJ (FGT/FGT) and MEJ (FGT/ZnO/Ni), respectively. As a result, FGT-MEJ exhibits 10-1000 orders higher conductance than other 2D-MTJs, while MR ratio remains similar to other 2D-MTJs.

Highly sensitive fiber vector magnetic field sensor based on an open-cavity Mach-Zehnder interferometer filled with magnetic fluid

In this paper, we proposed and demonstrated a highly sensitive fiber vector magnetic field sensor utilizing an open-cavity Mach-Zehnder interferometer (MZI) filled with magnetic fluid. The MZI sensor was fabricated using large-offset splicing technique to form an open cavity, facilitating the easy introduction of magnetic fluid samples into the open cavity. The MZI sensor was then encapsulated in a glass capillary containing diluted magnetic fluid. As the applied magnetic field varies, the refractive index of the magnetic fluid undergoes a corresponding change, subsequently inducing a shift in the transmission spectrum of the MZI. By monitoring the wavelength shift of the transmission spectrum, we can accurately detect the intensity of the magnetic field. The proposed sensor can achieve vector magnetic field measurement because of the axially asymmetric open-cavity MZI. The maximum sensitivity to magnetic field direction is 0.260 nm/°. Notably, the proposed sensor achieves an ultrahigh sensitivity, reaching an value of −17.306 nm/mT within the range of 4 mT to 7 mT. In addition, a temperature sensitivity of 2.236 nm/℃ is obtained within the temperature range of 30 ℃ to 65 ℃. Given its advantages, including high sensitivity, compact size and low cost, our MZI sensor holds immense potential for diverse applications in magnetic field measurement.

Paleolatitudinal movements of the eastern Sakarya Zone from Jurassic to Eocene

The study area covers a region oriented north-south from the Black Sea coastline in the north to the Kelkit Basin in the south within the eastern Sakarya Zone in northern Türkiye. The objective of this study is to investigate the paleolatitudinal movements of the eastern Sakarya Zone during the Jurassic-Eocene time interval through paleomagnetism. Various volcanic and sedimentary units (e.g., the Şenköy, Berdiga, Mescitli, Çatak, Kızılkaya, and Çağlayan Formations) spanning the time interval from the Early Jurassic to Middle Eocene were identified. A total of 98 locations belonging to Early/Middle Jurassic to Eocene volcanic and sedimentary units were selected for paleomagnetic core sample collection. The samples were subjected to demagnetization through thermal and alternating field methods. Characteristic remanent magnetization directions (ChRM) were obtained. Isothermal remanent magnetization (IRM) and high temperature susceptibility (HTS) measurements were made to identify the minerals responsible for magnetization. To ascertain whether magnetization was acquired through rock formation or as a consequence of subsequent tectonic processes, conglomerate and fold tests were performed. The results showed that magnetization was acquired before folding, i.e., the rocks have primary magnetization. Polarity tests were also conducted using coeval normal and reverse polarity sites. The results indicate that the mean magnetization direction for the Early-Middle Jurassic is 18.1°/55.2° (D/I) and 3.3°/51.5° (D/I) for sedimentary and volcanic rocks, respectively, and 348.7°/46.7° (D/I) for Late Jurassic/Early Cretaceous sedimentary rocks. In the Late Cretaceous period, the mean magnetization direction is 8.0°/49.3° (D/I) and 9.1°/47.0° (D/I) for sedimentary and volcanic rocks, respectively. In the case of the Early/Middle Eocene, the mean magnetization direction is 348.6°/52.7° (D/I) and 5.9°/48.8° (D/I) for sedimentary and volcanic rocks, respectively. In this study, the E/I correction was applied to the Late Jurassic/Early Cretaceous sedimentary rocks, and paleolatitude data obtained from sedimentary rocks were also utilized. Our paleomagnetic results indicate that the eastern Sakarya Zone was situated at latitudes spanning from 27.9° to 35.7° during the Early Jurassic - Middle Eocene time interval. In consequence, the eastern Sakarya Zone constituted a portion of the southern margin of the Eurasian continent during the Late Jurassic and Middle Eocene periods.

Dependence of divertor turbulence on plasma density and current in TCV

Abstract To reliably predict the distribution of heat and particle fluxes at the target plates of tokamaks, a comprehensive understanding of turbulence throughout the entire Scrape-Off-Layer (SOL) is imperative. This study examines divertor turbulence systematically across a broad parameter range on the TCV tokamak, including variations in magnetic field direction, plasma current I p ∈ [ 140 , 320 ] kA, edge safety factor q 95 ∈ [ 2.6 , 4.7 ] and Greenwald fraction f G ∈ [ 0.18 , 0.6 ] . The TCV X-point Gas Puff Imaging (GPI) system is used to measure 2D filament properties in the inner and outer divertor region. The fluctuation levels in the divertor are found to strongly increase with density (to 80% over most of the SOL) while remaining insensitive to I p . The previously identified divertor-localized filaments (DLF), located on the bad curvature side of the outer divertor leg, are found to be a common feature on TCV, while no filaments are observed in the PFR. DLFs are present over most of the parameter space and in both field directions. However, they are absent, or appear only closer to the target, for sufficiently large Λ div ≳ 10 or q 95 ≳ 3.7 . Across both I p and f G scans, some clear trends with Λ div are found for divertor filament sizes and velocities, and with target fall-off lengths of density and heat flux profiles at the outer target. This study provides important experimental insights to turbulent transport in the divertor also for comparison with self-consistent, turbulence simulations and extrapolation to future reactor conditions.

A comparative study on the lamella effect and properties of atomized iron powder and reduced iron powder in Fe-based soft magnetic composites

We prepared Fe soft magnetic composites (SMCs) with lamellar structure by using the flaky Iron powder, and studied the effects of types of iron powder on the microstructure and properties of Fe SMCs. The results show that the atomized iron powder and the reduced iron powder are deformed into flaky structure after ball milling, and these flaky iron powder have greater magnetic susceptibility and eddy current diameter perpendicular to the magnetic flux direction. In addition, compared with flaky gas atomized iron powder, the flaky reduced iron powder has large aspect ratio and lower coercivity. Therefore, the Fe SMCs with flaky reduced iron powder exhibit relatively high permeability (82) and low eddy current loss (0.033 W/kg at 50 kHz, 0.05 T), which shows the potential possibility of application at high frequency.

The Influence of Homogenous Magnetic Field Intensity on Surface Properties of Ni Thin Films Deposited from Citrate Baths and Their Role in Hydrogen Production

Magnetic fields influence the deposition process and its current efficiency. They have a remarkable influence on thin films’ surface characteristics and catalytic properties. Here, we study the correlation between the magnetic flux density and the current efficiency of the deposition process in the presence of a magnetic field with different intensities in different directions: the directions parallel and perpendicular to the electrode surface. We also show how the magnetic field direction impacts the surface roughness. Furthermore, we also analyze the impact of these synthesized films on the hydrogen evolution reaction (HER) when using them as electrocatalysts and how the application of a magnetic field in two dissimilar orientations influences the surface roughness and wettability. The synthesized Ni films are characterized using a scanning electron microscope (SEM), X-ray diffraction (XRD), and atomic force microscopy (AFM).

Analysis of the air gap magnetic field in cylindrical magnetic couplings based on mathematical and finite element approach

The air gap magnetic field of a magnetic coupling plays a crucial role in the examination of its static torque and eddy current losses. Precise characterization of the air gap magnetic field is essential for ensuring the accuracy of performance assessments of the magnetic coupling. This study focuses on the cylindrical magnetic coupling as the subject of investigation, employing mathematical analysis and finite element methods to evaluate and quantify the magnetic field properties. The study establishes a mathematical model of the magnetic field of a magnetic coupling based on electromagnetic field principles and the superposition theorem. An analytical formula for the magnetic flux density distribution of the air-gap magnetic field is derived. Subsequently, a three-dimensional magnetic field finite element model is created using the finite element method to numerically calculate the air gap magnetic field and validate the analytical formula. The research also explores the periodic distribution characteristics of the magnetic field in the air gap, analyzing axial differences in magnetic flux density value and direction distribution influenced by end effects.