Magnetic Coupling Effects Research Articles

Magnetic Texture in Insulating Single Crystal High Entropy Oxide Spinel Films.

Magnetic insulators are important materials for a range of next-generation memory and spintronic applications. Structural constraints in this class of devices generally require a clean heterointerface that allows effective magnetic coupling between the insulating layer and the conducting layer. However, there are relatively few examples of magnetic insulators that can be synthesized with surface qualities that would allow these smooth interfaces and precisely tuned interfacial magnetic exchange coupling, which might be applicable at room temperature. In this work, we demonstrate an example of how the configurational complexity in the magnetic insulator layer can be used to realize these properties. The entropy-assisted synthesis is used to create single-crystal (Mg0.2Ni0.2Fe0.2Co0.2Cu0.2)Fe2O4 films on substrates spanning a range of strain states. These films show smooth surfaces, high resistivity, and strong magnetic responses at room temperature. Local and global magnetic measurements further demonstrate how strain can be used to manipulate the magnetic texture and anisotropy. These findings provide insight into how precise magnetic responses can be designed using compositionally complex materials that may find application in next-generation magnetic devices.

Compact dual‐band bandpass filter with flexible passband frequencies and sharp skirt using cross coupling and mixed magnetic and electric coupling

This paper presents the design of a compact dual-band bandpass filter (DB-BPF) with flexible passband frequencies and sharp skirt. A pair of stub loaded stepped-impedance resonators (SL-SIRs) together with two different tri-section stepped-impedance resonators (TS-SIRs) constitute this DB-BPF. The low impedance sections of two SL-SIRs and one TS-SIR are realized by ring structure, on the one hand to acquire two independent resonant modes of SL-SIRs, and on the other hand to let the harmonic mode of TS-SIR be away from the upper passband. The cross coupling, the canceling effect of mixed electric and magnetic coupling (MEMC), and the virtual ground introduce the TZs, resulting in the sharp skirt property of proposed DB-BPF. Step-to-step design process is given to guide the DB-BPF design. As an example, a 0.9 / 1.8 GHz DB-BPF is designed and fabricated. The fabricated sharp skirts DB-BPF has a compact size of 0.079λg × 0.193λg, low passband loss of 0.84 / 0.98 dB and high band-to-band rejection of better than 40.6 dB.

Mitigating the effects of magnetic coupling between HV transmission line and metallic pipeline using slime mould algorithm

An aerial metallic pipeline experiences induced voltage if drawn in close vicinity of a high voltage power transmission line as suggested by Faraday's law of electromagnetic induction. Such voltages, if not appropriately mitigated, may prove fatal. This paper initially focuses on the evaluation of the induced voltage under the normal operating condition of power transmission lines followed by methods of passive mitigation of the induced voltages. The research also formulates the strategies to enhance mitigation efficiency by optimizing certain features of passive loop techniques using a new optimization algorithm called Slime Mould Algorithm (SMA). A 400 kV single circuit horizontal configuration line with an aboveground pipeline serves as a comprehensive test case to study the efficacy of the proposed algorithm. Results show that the induced voltage levels can be reduced up to 60% using the optimal location of loop conductors and the number of loops, in addition to using shielding material with high permeability. Comparing the obtained results with those obtained using Carson's formula and with genetic algorithm indicates the superior performance of the proposed technique.

Wave-like concentration profiles of a diamagnetic admixture in a cholesteric liquid crystal

The behavior of the orientation structure of a suspension of diamagnetic particles based on a cholesteric liquid crystal in an external magnetic field is theoretically studied. The effects of magnetic segregation and rigid homeotropic coupling between the liquid crystal matrix and admixture diamagnetic particles are taken into account. Within the framework of the continuum approach, a system of equations for the orientation equilibrium of the suspension was obtained using standard variational procedures. In the limit of weak magnetic fields, analytical dependences describing the behavior of the director vector field and the distribution of the admixture concentration along the suspension helix are obtained. A significant influence of the anisotropy parameter of the diamagnetic susceptibility subsystems on the wave-like concentration profiles in the suspension was revealed.

Dimensionality control of magnetic coupling at interfaces of cuprate-manganite superlattices.

The dimensionality of the crystal structure plays a vital role in artificial heterostructures composed of different transition metal oxides. Nonlinear layer-thickness dependence of the exchange bias effect was observed in high-quality SrCuO2/La0.7Sr0.3MnO (LSMO) superlattices induced in the present work by dimensional evolution. In the SCO(n)/LSMO(8) superlattices with thickness below the critical value (5 u.c.), the exchange bias effect decreased and the saturated magnetization increased with increase in SCO thickness. By contrast, the exchange bias effect increased and the saturated magnetization decreased in S(n)L(8) superlattices with thickness above the critical value. This is because the lattice SCO material underwent a breathing-like structural transformation from the planar to a chain-like structure. The results indicate the interfacial superexchange coupling mainly present in the chain-like S(n)L(8) superlattices through X-ray absorption spectroscopy and first principles calculations. This superexchange coupling generated a weak localized magnetic moment to pin the adjacent ferromagnetic layer. However, in the thicker S(n)L(8) superlattices, evolution of magnetic properties was induced by the long-range antiferromagnetic order in the planar SCO layer. Our findings demonstrate that the dimensionality driven structural variation is an effective method to manipulate the electronic reconstruction and the associated physical properties, paving a pathway for the advancement of strongly correlated materials.

From antiferromagnetic to ferromagnetic exchange in a family of phenoxido-bridged heterodinuclear Cu(II)-Mn(II) complexes: A magneto-structural theoretical study

Density functional theory with a broken symmetry approach was performed on phenoxido-bridged heterodinuclear complexes [LCuMn(NO3)2], for which magneto-structural correlations were developed. Satisfactory results were obtained at the B3LYP*/TZV level, and the calculated J value of the magnetic coupling constant was − 35.24 cm−1, which is consistent with the experimental result of − 35.80 cm−1. The analysis of spin populations indicated that the paramagnetic centers Cu(II) and Mn(II) exhibit a spin delocalization mechanism. The study of magneto-structural correlations indicated that the magnetic coupling constant J value shows a linear correlation with the bond angle (θ) of Cu–O-Mn; for θ < 97.20°, the magnetic coupling effect between Cu(II) and Mn(II) transformed from an anti-ferromagnetic to a ferromagnetic interaction.

An improved 220‐GHz RF CMOS compact equivalent circuit model considering magnetic coupling effect

AbstractIn this study, an improved RF CMOS transistor compact equivalent circuit model is presented. Due to the finite resistivity of the substrate, the magnetic coupling effect between the interconnection line and the substrate affects the signal propagation at mm‐wave frequency range. To characterize transistors in the terahertz band, a sophisticated network is introduced to represent the magnetic field of interconnection lines and substrate image current. In addition, the parameters of the proposed model are extracted by an analytical method. By comparison with the reported model, the proposed model can significantly improve the phase accuracy. The comparison of calculation results and experimental data shows that the proposed model can well characterize the transistor up to 220 GHz.

Strain Induced Anisotropic Magnetic Behaviour and Exchange Coupling Effect in Fe-SmCo5 Permanent Magnets Generated by High Pressure Torsion

High-pressure torsion (HPT), a technique of severe plastic deformation (SPD), is shown as a promising processing method for exchange-spring magnetic materials in bulk form. Powder mixtures of Fe and SmCo5 are consolidated and deformed by HPT exhibiting sample dimensions of several millimetres, being essential for bulky magnetic applications. The structural evolution during HPT deformation of Fe-SmCo5 compounds at room- and elevated- temperatures of chemical compositions consisting of 87, 47, 24 and 10 wt.% Fe is studied and microstructurally analysed. Electron microscopy and synchrotron X-ray diffraction reveal a dual-phase nanostructured composite for the as-deformed samples with grain refinement after HPT deformation. SQUID magnetometry measurements show hysteresis curves of an exchange coupled nanocomposite at room temperature, while for low temperatures a decoupling of Fe and SmCo5 is observed. Furthermore, exchange interactions between the hard- and soft-magnetic phase can explain a shift of the hysteresis curve. Strong emphasis is devoted to the correlation between the magnetic properties and the evolving nano-structure during HPT deformation, which is conducted for a 1:1 composition ratio of Fe to SmCo5. SQUID magnetometry measurements show an increasing saturation magnetisation for increasing strain γ and a maximum of the coercive field strength at a shear strain of γ = 75.

Improved magnetic properties of Sr0.93Sm0.10Fe11.97O19/Fe3O4 composite powders by substitution of Sm and magnetic exchange coupling effect

M-type hexagonal Sr0.93SmxFe12.07−xO19 and Sr0.93Sm0.1Fe11.97O19/Fe3O4 (SSFO/Fe3O4) composites are prepared by the ball-milling-assisted ceramic process and the solvothermal method, respectively. Substitution of Fe3+ ions by Sm3+ ions can significantly enhance the specific saturation magnetization (Ms), remanence (Mr), and coercivity (Hc) of Sr0.93SmxFe12.07−xO19. Increase in coercivity is attributed to an increase in the magnetrocrystalline anisotropy and a reduction in the particle size after substitution of Fe3+ ions by Sm3+ ions. Sr0.93Sm0.10Fe11.97O19 has the highest specific saturation magnetization value (71.16 emu/g). By contrast, 2.91% increase in specific saturation magnetization and 22.86% increase in coercivity for SSFO/Fe3O4 composite with 4:1 mass ratio of hard to soft ferrites are observed, respectively, as compared to the pure SSFO. Besides, SSFO/Fe3O4 composite with 4:1 mass ratio of hard to soft ferrites behaves higher Mr (33.80 emu/g) and Hc (2624.27 Oe) values than theoretically calculated values of 30.60 emu/g and 1722.72 Oe, indicating the presence of strong exchange coupling interaction between the hard SSFO and soft Fe3O4 phases.

A Non Inverting Soft Switching Buck Boost Converter Closed Loop and It’s Performance Against Various Converters

A Non-inverting soft switching buck-boost Converter is presented. One of the major hurdles that every converters face is switching losses. This loss is associated with the switches that are used to build the converters. To overcome this, magnetic coupling effect has been introduced to the proposed converter. This magnetic coupling effect helps the converter to obtain an adjustable soft switching range. Theoretically, it has been said that soft switching results in zero switching losses. That way, the losses due to switching can be neglected and that helps in improving the overall efficiency. In the paper, we have proposed a soft switching non inverting buck-boost converter and compared its performance characteristics with various other converters.

Dependence of electromagnetic wave absorption properties on the topography of Ni anchoring on reduced graphene oxide

Specific topographic Ni anchoring on reduced graphene oxide (rGO) composites show an astronomical potential as effective wave absorbers due to the synergistic electromagnetic loss effects. Herein, Ni/rGO composites with different topography were successfully prepared via hydrothermal in-situ reduction method. The structure and morphology characteristics revealed that particle-like, chain-like, coin-like and flower-like Ni were closely anchored onto rGO, respectively. The electromagnetic wave absorption (EMA) performance revealed that chain-like Ni/rGO exhibited the optimal reflection loss of -43.7 dB with a thickness of 1.8 mm as well as the EAB of 6.1 GHz at 2.0 mm among all samples due to the good impedance match and the synergistic dielectric and magnetic losses. Besides, one conclusion can be drawn that excellent magnetic coupling effect and impedance matching were the main reasons for significantly improving the EMA performance. Considering the systematic dependence of morphology on EMA, this work provides a perspective for designing high-performance absorbing materials.

Coupling effects in hub motor and optimization for active suspension system to improve the vehicle and the motor performance

For electric vehicles (EVs) driven by in-wheel motor (IWM), the motor is directly integrated into the wheel. The coupling effects caused by the magnet gap deformation (MMG) in the motor and further enhanced by the unbalanced electromagnetic force (UEF) and the road excitation deteriorate the performance of EVs. However, few researchers have explored the coupling effects based on permanent magnet synchronous in-wheel motor and methods to suppress them. In this paper, the integrated model addressing the mechanical–electrical–magnetic coupling effects between the electromagnetic excitation in the permanent magnet synchronous motor (PMSM) and the transient dynamics in EVs is developed. The function mechanism of UEF-MMG deformation coupling circle is investigated and its influences on the performance of EV are explored. Moreover, using particle swarm optimization (PSO) algorithm, a multi-objective optimization method for active suspension system is proposed to solve the negative coupling effects. The simulation results indicate that the optimized active suspension system which considers the multi-field coupling effects of the IWM can effectively reduce the UEF caused by the eccentricity in the motor. Furthermore, it can attenuate the multi-field coupling effects and remarkably improve the ride comfort of EVs. The proposed multi-objective optimization method demonstrates a potential application in engineering practice.

Near-Field HF-RFID and CMA-Based Circularly Polarized Far-Field UHF-RFID Integrated Tag Antenna

This research proposes an integrated high-frequency (HF) and ultrahigh-frequency (UHF) passive radio frequency identification (RFID) tag antenna for near-field (13.56 MHz) and far-field (920–925 MHz) communication. This tag antenna is advantageous for the applications with lossy material in the near-field communication and mitigates polarization loss in the far-field communications. The HF-RFID tag antenna is of square spiral structure, and the circularly polarized UHF-RFID structure consists of a square loop radiator with cascading loop feeding and shorted stub. The structure of HF-RFID tag antenna situated inside the circularly polarized UHF-RFID tag can avoid the significant effect of the near-field magnetic coupling from the square loop. The UHF-RFID tag antenna is realized by using characteristic mode analysis for wideband circular polarization. The HF-RFID structure is conjugate-matched with NXP NT3H2111 chip, and the UHF-RFID structure is conjugate-matched with NXP G2X chip. Simulations were carried out, and an antenna prototype was fabricated. The experimental results reveal that the radiation pattern of UHF-RFID tag antenna is bidirectional with a gain of 0.31 dBic. The impedance bandwidth covers the frequency range of 903–944 MHz, and the axial ratio in boresight direction at 922.5 MHz is 1.67 dB, with the axial ratio bandwidth over 863–938 MHz. The maximum near-field and far-field reading ranges are 4.9 cm and 8.7 m. The proposed integrated dual-band passive tag antenna is operationally ideal for HF-RFID and UHF-RFID applications.

Antiphase synchronization and central symmetrical antiphase synchronization in magnetic field coupled circuits

The dynamics of memristor-based RLC circuit is explored on the effects of magnetic field coupling through a transformer in the circuit. With the increasing strength of magnetic field coupling, the two coupled RLC circuits firstly break the reflectional symmetry by transiting from double-scroll attractors to single-scroll attractors and then break the translational symmetry with two attractors in different sizes and shapes. The two single-scroll attractors are locked in antiphase synchronous states for positive magnetic field coupling while transit to a new kind of dynamic regime, named as central symmetrical antiphase synchronization (CSAS) for negative magnetic field coupling. Moreover, the single-scroll attractors in inphase synchronization or in CSAS may coexist with asynchronous states in some interval of coupling strength. The dynamics of the anti-synchronization and the CSAS of the coupled memristor-based circuits have potential applications in nonvolatile memories, neuromorphic devices to simulate learning, adaptive and spontaneous behaviors.

Tunable Spin-Wave Tunneling Junction

Like the Esaki (tunneling) diode in electric circuits, the spin-wave can transmit through nonmagnetic materials that can be regarded as “insulators” for magnonic circuits. Researchers have discovered the tunability of this spin-wave tunneling by using the external voltage acting on the effective magnetic coupling between two separated magnets.

Magnetic resonance energy transfer for in vivo glutathione susceptibility weighted imaging

Glutathione (GSH) plays a vital role in maintaining biological redox homeostasis. Accordingly, accurate imaging of glutathione in vivo is of great significance. Herein, we propose a magnetic resonance energy transfer (MRET) strategy based on a distance-dependent magnetic exchange coupling effect (MECE), which can realize GSH detection within tumors in vivo by susceptibility weighted imaging (SWI). Fe3O4 nanoparticles (NPs) and CoFe2O4 NPs linked with cystamine (Fe3O4–S–S–CoFe2O4) have been successfully designed as SWI nanoprobes. After the disulfide bonds are broken by excess GSH in the tumor, the increase in the distance between Fe3O4 NPs and CoFe2O4 NPs will induce a decrease of MECE and magnetic susceptibility. As a result, the changes in the SWI signals are used for tumor GSH detection in vivo. Experimental results in vitro and in vivo demonstrate that the Fe3O4–S–S–CoFe2O4 SWI nanoprobe can sensitively detect concentrations of GSH in tumors. Hence, this strategy not only improves the sensitivity of the GSH response in SWI but also provides a powerful basis for the design of other responsive functional MRI nanoprobes.

A Soft-Switching Non-Inverting Buck–Boost Converter With Efficiency and Performance Improvement

This letter proposed a new soft-switching non-inverting buck–boost converter (NIBBC) by introducing the magnetic coupling effect to an existing soft-switching dc/dc converter. The new NIBBC obtains two superiorities: one magnetic core is removed to improve the efficiency; the magnetic coupling effect can give an adjustable soft-switching range. Operating principles and converter characteristics of the new NIBBC are presented. An experimental prototype of the new NIBBC is built, and switching waveforms and the efficiency are measured. Experimental results show that the new NIBBC can obtain soft-switching conditions and has efficiency improvement comparing to hard-switching converter and another soft-switching dc/dc converter.

An Efficient Cell-Based Smoothed Finite Element Method for Free Vibrations of Magneto-Electro-Elastic Beams

Magneto-electro-elastic (MEE) materials are widely used in intelligent structure systems owing to their electronic, mechanical and magnetic coupling effects. To overcome the over-stiffness of the finite element method (FEM) stiffness matrix and simulate the free vibration of MEE structures more accurately, we introduced the gradient smoothing technique into MEE multi-physical-field FE model and thereby deduced the cell-based smoothed finite element method (CS-FEM) equations of MEE materials. The MEE beams and layered beam affected by the coupling effect of multiple physical fields under different boundary conditions were computed by CS-FEM, after comparing results with those of FEM and reference solutions, the accuracy and efficiency of CS-FEM were validated.

An ensemble learning estimation of the effect of magnetic coupling on switching frequency value in wireless power transfer system for electric vehicles

Wireless power transmission (WPT) systems of small power levels used in the medical and communications sectors have been developed in recent years for tens of kW power levels for charging stations of electric vehicles. In wireless charging systems, power transfer is provided by magnetic coupling using coreless transformers, and in these systems, power electronics circuit design is the crucial point. The inductor behavior as a series resonance circuit element required in the power electronics circuit of WPT systems varies according to the magnetic coupling positioning errors between the primary and secondary sides of the coreless transformer. Therefore, the considering that the resonant capacitor value is constant in the resonance tank circuit, the switching frequency value in the power electronics circuit must be adaptively controlled so that the transferred power value can be carried out efficiently. In this study, the parametric simulations have been performed using Ansys-Electronics software to adaptively control the switching frequency value in the inverter circuit depending on the magnetic coupling coefficients in the WPT circuit designed at a power value of 25 kW. Based on the data obtained from these simulation studies according to different scenarios, the switching frequency value can be changed adaptively and thus the WPT efficiency can be kept at a certain level by providing resonance in each condition. Also, 105 efficiency data were obtained by using Ansys-Electronics parametric solver for many variables such as coreless transformer, resonant circuit parameters of power electronic circuit, switching frequency and magnetic coupling. The WPT efficiency is predicted by ensemble decision trees algorithm. The results show that the estimation with ensemble decision trees is quite successful.

Magnetic coupling and flextensional amplification mechanisms for high-robustness ambient wind energy harvesting

Harvesting wind energy is becoming increasingly significant for its availability and abundance in the ambient environment, which is a promising strategy to develop self-powered small-scale electromechanical systems. However, the drawbacks of the current small-scale wind energy harvesters, namely, low robustness, narrow wind speed range, and low output power hinder the application in natural environment. Here, we propose an innovative approach for rotational piezoelectric wind energy harvesting using magnetic coupling and force amplification mechanisms, which has a higher equivalent piezoelectric coefficient, better robustness and broader wind speed range for application. Thanks to the reasonable symmetrical opposite magnetic arrangement, the resistance torque has been reduced significantly while the effective force can be maximized. The effective magnetic coupling modes are clarified, and the corresponding dynamic models are established. The effects of key parameters on the output performance are analyzed and the effects of assembly errors on reluctance torque are discussed as well. The performances of the proposed harvester are investigated through laboratory experiments and outdoor natural wind tests. The results show that the established model can characterize the energy harvester precisely. In an outdoor natural wind environment, the prototype is able to work continuously for more than 12,000 s with the wind speed from ~3 m/s to ~10 m/s. After a long period of experiments, no damage to the prototype is observed. Besides, the proposed harvester can generate high and relatively stable open-circuit voltages from low wind speeds to high wind speeds. These results reveal that the proposed harvester has high robustness and broad wind speed range for the application.