Magnetic Arrangement Research Articles

Design and analysis of PM‐assisted synchronous reluctance machine with shifted magnetic poles

AbstractThe authors present a new design of a PM‐assisted synchronous reluctance motor (PM‐SynRM) with uneven air‐gap length to improve the power factor and enhance the torque production capability. The rotor structure is modified to properly shift rotor magnetic poles and therefore (i) increases the back‐EMF and the electromagnetic torque, (ii) allows electromagnetic torque and reluctance torque components peak near the same current phase angle. The proposed solution is simple, does not require changing the arrangement of magnets and/or flux barriers and is applicable to all types of PM‐SynRMs. Sensitivity analysis is carried out to determine the extent of which the proposed magnetic pole shifting may impact the resultant torque profile. To assess the level of success, the electromagnetic characteristics of the proposed design (e.g. torque, power factor, and back‐EMF) are compared against the baseline structure under the same operating conditions. For verification purposes, Finite Element simulation results are validated via a series of analytical calculations and experimental measurements, and supported with detailed theoretical discussion.

Comparative Study of Amino-Functionalized Magnetic Mesoporous Arrangements for the Remediation of Persistent Organic Pollutants from Water Using Response Surface Methodology

Comparative Study of Amino-Functionalized Magnetic Mesoporous Arrangements for the Remediation of Persistent Organic Pollutants from Water Using Response Surface Methodology

Optimization of NdFeB Permanent Magnets Configuration for Spinal Cord Drug Delivery

Magnetic drug delivery is an effective method to decrease the side effects of traditional drug delivery methods. To enhance the efficiency of magnetic nanoparticle transport, a precise and cost-effective magnetic system is required. In this research, different arrangements of NdFeB magnets for drug delivery in human spinal cord were presented and then compared. Assummed magnetic nanoparticles are injected into the cerebrospinal fluid (CSF) and focused on the disease site with external magnets. The effects of these magnets on nanoparticles have been investigated. The results show that the arrangement of sharp magnets has a more accurate performance in delivering nanoparticles to the damage site than other arrangements. The designed magnetic system can improve the accuracy of drug delivery in the spinal cord compared to previous methods.

End effects of Halbach field magnet‐type linear motor

AbstractA linear motor that uses a finite length Halbach array as its magnetic field causes a thrust force ripple owing to end effects. In this paper, the theoretical and numerical analysis methods of the Halbach array are investigated. The results of the electromagnetic field analysis are compared to confirm the validity of the theoretical and numerical solutions. Moreover, we focus on the magnetic pole period and coil arrangement of the finite length Halbach field type linear motor to eliminate the influence of the end effects, and report the relationship with the end effects.

Magnetic super-structure and active surface role in the onset of magnetic excitons revealed in TbCu2 nanoparticles

Antiferromagnetic materials are receiving renewed interest on behalf of their potential for information technologies. Recent reports have also revealed how the physics governing such magnetic arrangements and their excitations become more complex compared to traditional ferromagnetic materials, especially at the nanoscale. Here, we address two main issues that are of prime interest to their technological transfer. First, using small-angle neutron scattering, we show the existence of a magnetic helix-like super-structure in a polycrystalline TbCu2 alloy, preserved at both bulk and nanoparticle ensembles of 8 nm. Second, using inelastic neutron scattering, we elucidate the magnetic excitons and the crystalline electric field energy level schemes of TbCu2 in bulk and nanoparticle ensembles. This allows to understad the effect of the surface broken symmetry on the quantum energy levels at the nanoscale, so as the key role of interfacial effects on the propagation of magnetic excitations. Our research provides insights for the realization of magnetic moment dynamics models based on complex nanometric super-structures, and for nanoparticles to be integrated in spintronics and information technology applications.

Design of an Electromagnetic Turnout Scheme for a Two-Line PMG of HTS Maglev Systems

The Maglev transport system is a new promising high-speed system of the future, which includes many different applications that ensure its fast and reliable operation. For the possibility of transferring rolling stock from one track to another, a turnout switch is needed. It has been proved that the electromagnetic turnout switch is one of the best choices for the Maglev switch systems because there are no moving parts. Some schemes and designs of an electromagnetic turnout switch have already been proposed, but still no schemes for entering into a real two-line permanent magnet guideway (PMG) of the Maglev system. In this article, the whole electromagnetic turnout switch for a two-line PMG is considered, electromagnetic turnout schemes have been developed for installation in a real full-scale two-line PMG of the Maglev system, and the main elements of an electromagnetic turnout switch are shown. The formulas for calculation of the total length of an electromagnetic turnout switch and the radius of the transfer curve were presented. Moreover, in this paper, the displacement of the magnetic axis of the left and right rails relative to the theoretical axis due to the arrangement of magnets in a way of checkerboard was studied.

A comparative study on transient vibration suppression of magnetic nonlinear vibration absorbers with different arrangements

Nonlinear vibration absorbers (NVA) using magnets feature ease of implementation and outstanding tunability and have attracted much interest in vibration suppression in recent years. Through configuration design and optimization, magnetic NVA can exhibit different nonlinear characteristics such as monostability, bistability and tristability. This work performs a comprehensive comparative study on the transient vibration suppression performances of the NVAs with four different magnet arrangements based on the cantilever beam design, including the NVA with two repulsive magnets (2RMNVA), two attractive magnets (2AMNVA), three repulsive magnets (3RMNVA) and three attractive magnets (3AMNVA). Based on the dipole–dipole model of magnets, the dynamic model of the system containing different magnetic NVAs is established for numerical simulation and the key parameters of each NVA are optimized under different excitation levels. The influence of parameters on different magnetic NVAs is investigated. Based on the optimization configurations, the rate of the energy dissipation from the primary structure by different magnetic NVAs is compared by wavelet transform analysis. The results show that due to the largest oscillations of crossing outmost wells, the optimized 3RMNVA and 3AMNVA are the preferred configurations for magnetic NVA under different excitation levels. Meanwhile, through the verification and comparison with reported designs, the effectiveness of the optimization method and the optimized NVAs in this paper are confirmed. This work provides the approach and guidelines to design the effective NVA to suppress transient vibrations.

Self-powered elementary hybrid magnetoelectric sensor

There are numerous magnetic field sensors available, but no simple, robust, sensitive sensor for biomedical applications that does not require cryogenic cooling or shielding has yet been developed. In this contribution, a new approach for building a magnetoelectric field sensor is presented, which has the potential to fill this gap. The sensor is based on a resonant cantilever with a piezoelectric readout layer and a pair of opposing permanent magnets. One is attached to the cantilever, and the other one is fixed to a sample holder below. This new concept can be deduced from the most basic composite-based sensor [1], where the magnets interact analog to two particles in a polymer matrix. The bias-free, empirical measurements show a limit-of-detection of 46 pT/√Hz with a sensitivity of 2170 V/T using the sensor’s resonance frequency of 223.5 Hz under ambient conditions. The sensor fabrication is based on low resolution silicon technology, which promises high compatibility and the possibility to be integrated into MEMS devices. The design of this new sensor can be easily altered and adjusted according to the requirements of the specific sensor application. For example, tuning of the operating resonance frequency cannot solely be modified in the production of the cantilever but also by the arrangement of the permanent magnets. In addition, the concept can also be applied to energy harvesters. Beside possible mechanical excitation, the presence of a magnetic stray field alone allows the sensor to convert 20 µT into a power of 1.31 µW/cm³·Oe². The fact that the device does not require any DC bias field makes it very attractive for energy harvesting applications since this allows a purely passive operation. In this manuscript, the sensor assembly, measurements of directional sensitivity, noise level, limit-of-detection, evaluation for energy harvesting applications from magnetic fields and a quantitative sensor model are presented.

Field-free spin-orbit torque switching in interlayer exchange coupled Co/Ta/CoTb

This study investigates a T-type field-free spin-orbit torque device with an in-plane magnetic layer coupled to a perpendicular magnetic layer via a non-magnetic spacer. The device utilizes a Co/Ta/CoTb structure, in which the in-plane Co layer and the perpendicular CoTb layer are ferromagnetically (FM) coupled through the Ta spacer. ‘T-type’ refers to the magnetization arrangement in the FM/spacer/FIM structure, where the magnetization in FM is in-plane, while in FIM, it is out-of-plane. This configuration forms a T-shaped arrangement for the magnetization of the two magnetic layers. Additionally, ‘interlayer exchange coupling (IEC)’ denotes the interaction between the two magnetic layers, which is achieved by adjusting the material and thickness of the spacer. Our results show that an in-plane effective field from the IEC enables deterministic current-induced magnetization switching of the CoTb layer. The field-driven and the current-driven asymmetric domain wall motion are observed and characterized by magneto-optic Kerr effect measurements. The functionality of multistate synaptic plasticity is demonstrated by understanding the relationship between the anomalous Hall resistance and the applied current pulses, indicating the potential for the device in spintronic memory and neuromorphic computing.

Assessing the stability of Kagome D019-Mn3Ga (0001) surfaces: A first-principles study

Using non-collinear spin-polarized first-principles calculations, we have investigated the properties of the hexagonal D019 (0001) Mn3Ga surface. Two different surface terminations were considered: type-1 and type-2, with opposite chiralities. In the case of pristine surfaces, the Kagome triangular AFM character remains on the surface and in inner layers, with a slight increase in the surface magnetic moments due to the low coordination of the surface atoms. An increase in the remnant out-of-plane FM character compared to the bulk is also noticed. The effect of Ga or Mn vacancies on both surfaces was also investigated. Ga vacancies in the 2nd monolayer are more stable than in other layers. Such vacancies distort the triangular AFM configuration of the neighboring layers. Despite this, the AFM layer-by-layer nature remains. Conversely, Mn vacancies stabilize in the most exposed layer. In this case, the neighboring layers completely lose the triangular alignment. However, Mn atoms rearrange to preserve the AFM layer-by-layer character. Upon evaluating the thermodynamic stability of these surfaces, we observe that the pristine Kagome AFM magnetic surfaces are the most stable. Ga vacancies are the least stable configurations because they break down the super-exchange interaction that holds the Kagome magnetic arrangement. Finally, our calculations show that the Kagome magnetic arrangement at the surface is stabilized by both the magnetic (Mn) and non-magnetic (Ga) atoms. Therefore, it is expected that D019-Mn3Ga will not present low-index reconstructions induced by vacancies.

Experimental characterization of the flowline of a lithium film formed using an electromagnetic thruster for a RAON prototype charge stripper

This paper describes the variable optimization of a lithium charge-stripper device for the Rare isotope Accelerator complex for ON-line experiences (RAON) and the experimental characterization of a lithium film formed for the charge removal of uranium using a magnetohydrodynamic liquid metal circulation system. To this end, liquid lithium charge stripper was fabricated to form a thin lithium film flow through collisions between a liquid lithium jet and a planar deflector. The flow characteristics of the lithium film were analyzed through simulation and waterjet experiments in terms of the liquid lithium film thickness. To circulate the liquid lithium, a mechanically safe electromagnetic thruster with precise pressure control was designed by analyzing its electromagnetic and hydraulic parameters through finite element simulation. The analysis of the geometrical arrangement of the permanent magnet and input current of the thruster revealed that compared to existing electromagnetic thrusters, the nominal input current of the newly-constructed thruster was reduced to 57% and its weight reduced to 6%, while facilitating easy maintenance. The optimized nozzle diameter and angle of the lithium charge stripper was 0.7 mm and 34°, respectively. Further, the formation of a 22-µm thick liquid lithium thin film required to obtain the 79+ charge state of uranium was confirmed at an input current of 107 A.

Effects of external magnetic field arrangements on thermomagnetic convection in ferrofluid around heated Micro-wire

Thermomagnetic convective cooling of a heated micro-wire in quiescent ferrofluid is experimentally investigated under various non-uniform external magnetic fields produced by permanent magnets. In the past studies, in most of the cases for this geometry the external magnetic field is applied under forced convection conditions. This work provides the first published data set of heat transfer from a microwire in quiescent ferrofluid (free convection conditions) under various arrangements of external magnetic fields produced by permanent magnets. For the different arrangements, magnetic flux density and Kelvin body force density are calculated to aid discussions of the observed effects. The experiment tracked the transient temperature rise of a heated micro-wire, highlighting effects of applied magnetic field orientation, symmetry, and strength. The results showed that greater non-uniformity in radial magnetic field could enhance the cooling effects with up to 7% reduction in the heated wire temperature rise. A magnetic field aligned with the heated wire axis produced only a minor enhancement of 3% in heat transfer in contrast to application of radial magnetic fields. Surprisingly, a stronger external magnetic field did not always result in better heat transfer. Magnetophoresis of ferro-particles induced by the external magnetic field was found to be an important consideration when using permanent magnets for ferrofluid applications.

A magnetic coupling wind energy harvester for unmanned surface vehicles

Energy harvesting from the surrounding environment is an effective method to develop a self-powered system and achieve ocean environment monitoring by unmanned surface vehicles. However, a series of challenges, such as narrow wind speed range and low output power, hinder the practical application of wind energy harvesters in real conditions. To tackle these problems, a wind energy harvesting system with double magnets coupling mechanism based on piezoelectric and electromagnetic effect was proposed to enhance wind speed bandwidth and improve output power. The symmetrical opposite magnet arrangement can reduce the start-up torque and boost the adaptability and robustness under the low wind speed environment. In addition, three magnet configurations are explored and corresponding output performances are compared and evaluated. The optimal magnet configuration is obtained in low wind speed conditions. The finite element method analyzes the magnetic coupling mechanism's dynamic performance and electrical properties. The analysis shows that the optimal mode of magnet arrangement can reduce resistance torque by 32.9 % compared with the traditional mode. The experimental results reveal that the proposed double magnets coupling mechanism can broaden wind bandwidth by 1.5 m/s at the low wind speed zone. Additionally, the hybrid energy harvester can obtain maximum average power of 22.2 mW and light up 138 light-emitting diodes. The self-powered application of commercial sensors for unmanned surface vehicles and outdoor tests verified the feasibility and effectiveness of the proposed wind energy harvesting system.

Spin Control and Multifunctional Photocurrent Switch in Chiral Hybrid Organic–Inorganic Perovskites

Chiral-induced spin selectivity effect provides a new strategy for manipulating electron spin, which has potential applications in various spin-related fields. Here, the spin-selective electronic transport and photocurrent response of (R,S-MBA)2PbI4 are investigated systematically by first-principles calculations. The minimum periodic chiral hybrid system has stable spin filtering ability. Different from achiral magnetic tunnel junctions (MTJs), the resistance of chiral MTJs depends on the chirality of (R,S-MBA)2PbI4 and magnetization arrangement of ferromagnetic electrodes. Additionally, the photon energy and magnetization arrangement of electrodes can be used to switch the spin channel and photocurrent direction. At a photon energy of 3.0 eV, chiral MTJs can transfer from separating spin into outputting highly spin-polarized photocurrent by changing the magnetization arrangement of electrodes. Chiral spin control and multifunctional photocurrent switch of Fe/(R,S-MBA)2PbI4/Fe MTJs provide important information for the design of chiral spintronic and nanoscale electronic devices.

Ferromagnetic coupling mechanism and vacancy defect regulation strategy of V-doped LiMgAs

First-principles calculations were conducted to investigate the electronic structure and magnetic coupling mechanism of V-doped LiMgAs. The regulation strategy of Li vacancy defects on magnetism was also adopted. The results showed that all the designed defective configurations exhibited thermodynamic stability evaluated from the formation energy. The V nearest neighbor doping configuration occupied the lowest formation energy of −9.26eV and performed the strongest stability. V dopant had advantages in magnetic introduction and the maximum atomic magnetic moment in this study was 6.40 μB/V. The ground state of the magnetic coupling was determined by the energy difference of the doping configurations for magnetic ions antiferromagnetic and ferromagnetic arrangements. The magnetic dopants existed in Li(MgV)As system by ferromagnetic coupling and the ferromagnetic stability weakened with the increase of the V atom separation. The incorporation of Li vacancy defect promoted the enhancement of ferromagnetism. The optimal design configuration was V atoms nearest neighbor doping with one Li vacancy defect with the energy difference of 0.27eV, which performed the strongest ferromagnetic stability. The removal of Li ion introduced the additional itinerant hole carrier and elevated the non-localized characteristics of the carriers in p-d hybrid orbitals, which facilitated the electron exchange between magnetic ions. In this paper, a novel type of dilute magnetic semiconductor with controllable carriers was designed and the mechanism of ferromagnetic coupling was revealed, which provided a theoretical reference for the subsequent studies.

Carbide twist drill surface polishing and cutting edge passivating based on magnetic field-assisted shear thickening

The multi-field compound polishing method based on the shear thickening has been applied to the processing of various hard materials due to its characteristics of low damage and adaptability to complex surface shapes. The surface defects on the carbide twist drill are usually produced during the grinding. This paper proposes a magnetic field-assisted shear thickening polishing (MASTP) method based on shear thickening and pumping effect, aiming to enhance surface quality of twist drill and passivate cutting edges to improve its cutting performance. The microscopic material removal mechanism of the twist drill and the rheological properties of magnetic shear thickening fluid were analyzed. The magnetic field intensity distribution in the polishing area for two types of magnetic pole arrangements is simulated. A numerical simulation was used to investigate the effect regularity of the polishing gap and spindle speed on the flow field shear stress. Experimental validation was carried out based on the processing platform. The results show the effects of processing parameters on twist drill surface roughness improvement rate and edge radius correspond to the simulated shear stress. After 60 min of polishing, the surface roughness improvement rate reached 94.7% and 80.4% at the body clearance and margin of the twist drill, respectively. The passivating radius of the major cutting edge can reach 12.92 μm, while the passivating radius of the minor cutting edge can reach 15.73 μm. At the same time, the edge defects caused by the grinding are also removed.

Experimental investigation of liquid metal droplet flow affected by a time-dependent magnetic field

Abstract The present study investigates experimentally the effects of a time-dependent and spatially inhomogeneous magnetic field on liquid metal droplet flow down an inclined substrate. The flow is solely excited by the electromagnetic interactions between the electrically conducting melt and the applied magnetic field. The metal droplet consists of the eutectic alloy GaInSn which is liquid at room temperature. The magnetic field is generated in the gap between two metallic disks that are equipped with a special geometric arrangement of permanent magnets and put into a measured rotation. During the experiments, a droplet of a measured volume is positioned on an electrically non-conducting substrate that is slightly inclined against the horizontal direction. Droplet and substrate are placed in between the two rotating magnetic disks. In our experiments, we record the electromagnetically excited flow of the droplet downwards onto the substrate using a high-speed camera system. Applying standard techniques of digital image processing, we measure both the displacement position and velocity of the droplet as a function of time. We observe that, depending on the rotation rate of the disks and angle of inclination, the magnetic field eventually triggers this spreading process. In more detail, by evaluating the recorded data, we find that the magnetic field excites capillary waves at the free surface of the droplet. These surface waves contribute to a redistribution of volume towards the contact line formed at the downward-facing end tip of the droplet. This mode of transport steepens the contact angle, allowing the droplet to move. Besides the fundamental aspect of this work, the present study may contribute to the electromagnetic control of both the production of metallic microfibers and metallurgic coating processes as well as to the non-contact electromagnetic flow measurement technique of Lorentz force velocimetry applied to liquid metal free-surface flows.

An Efficient and Stable Embedded Multi-U-Shaped Column Rotary Transformer

Inductively Coupled Power Transfer (ICPT) technology can be used to solve the problems of high friction loss, overheating and low stability caused by conductive slip rings on rotating power supply equipment. An improved Embedded Multi-U-Shaped Column Rotary Transformer (EMUCRT) based on the ICPT and spliced core structure is proposed in this paper. It has a higher coupling coefficient and can transmit power more efficiently and stably due to the primary magnetic core is embedded inside the secondary magnetic core. Compared with the one-piece core structure, the spliced type is more flexible due to its loose magnetic core arrangement. Its primary coil can still transmit energy stably after offset by a certain distance, so the structure has good anti-misalignment ability. On the basis of analyzing its magnetic core arrangement and magnetic circuit model, the optimal magnetic core specifications and quantities of primary and secondary side are obtained by theoretical calculation and simulation. In order to verify the high efficiency, rotational stability and anti-misalignment characteristics of the structure, an experimental prototype was built. The results show that EMUCRT can transmit energy efficiently and has good rotational and offset stability.

Influence of streamwise and spanwise wall magnet arrays on near-wall MHD turbulence

ABSTRACT The effect of a permanent, localised and non-uniform magnetic field on the near-wall turbulence in a fully developed channel flow is analysed through direct numerical simulations. The magnetic field distribution is obtained by an arrangement of magnets placed on the upper and lower channel walls, producing preferentially either a streamwise (i.e. in the main flow direction) or a spanwise magnetic field component. The wall shear stress is drastically reduced under the effect of the streamwise arrangement of the wall magnets wherein both streamwise and wall-normal magnetic fields are involved. The magnetic braking effect leads to an important increase of the body force. Paradoxically enough, the small-scale turbulent activity is significantly increased above the low buffer layer in this case. On the opposite, imposing a magnetic field with a predominant spanwise component reduces tremendously the population of the turbulent shear stress producing eddies by directly affecting the regeneration of the buffer layer quasi-streamwise vortices. The flow is quasi-relaminarised between the magnets in the low-buffer and viscous sublayers. The wall shear increases in a predictable and deterministic way over the magnets, wherein the wall normal magnetic field component induces electric current loops.

Effect of permanent magnets in optimized arrangement for levitation support on vibration characteristics of levitated flexible steel plate

In the production line of thin steel plates, contact conveyance by rollers causes deterioration in the surface quality of the plates. To solve this problem, our research group has been continuously investigating the optimal placement of permanent magnets in hybrid magnetic levitation systems. In this study, when a thin steel sheet was magnetically levitated, the effect of the horizontal electromagnet position on the gap between the steel sheet and the permanent magnet was investigated through a permanent magnet configuration optimized using a genetic algorithm.