Search Results (85)

This study investigates an IPS-type Metglas/PMN-PT laminated magnetoelectric composite and its feasibility as a reciprocal mechanical magnetoelectric antenna for low-frequency transmission and reception. Finite-element simulations under quasi-static and frequency-domain conditions reveal strong magnetoelectric coupling under an optimal DC bias field, with both the direct magnetoelectric effect (DME) and converse magnetoelectric effect (CME) exhibiting pronounced resonance near 14.5 kHz, governed by the same longitudinal extensional vibration mode. Five IPS samples were fabricated and experimentally characterized. All devices showed resonant frequencies within 14.1–14.5 kHz, peak DME coefficients of 3.0 × 10⁶ to 3.9 × 10⁶ pC/Oe, and peak CME coefficients of 12.0~15.8 Oe·cm/V, confirming good fabrication consistency, transmit–receive reciprocity, and array-integration potential. The parallel IPS antenna generated a magnetic flux density of 37 nT at 1 m, and exhibited an equivalent magnetic noise of 63 fT/Hz^1/2 at 14.45 kHz. These results demonstrate that the proposed IPS structure combines high-sensitivity reception with efficient low-frequency transmission, showing strong potential for miniaturized, low-power, and long-range magnetic communication and underwater communication applications. Full article

We explore the interaction of a plane electromagnetic wave with a topological insulator (TI) cylinder that is coated with homogeneous magnetized ferrite. TIs display exotic electromagnetic responses due to topological magnetoelectric (TME) phenomena. An analytic theory for the electromagnetic scattering from a TI scatterer is developed. The analytical expressions of the polarized electromagnetic fields for the transverse magnetic (TM) case are formulated. The so-called unknown scattering coefficients are derived by implementing the boundary conditions (BCs) on the surface of a TI. The scattering characteristics of plane waves by a TI scatterer are numerically simulated and discussed. The numerical results demonstrate that the scattering characteristics are strongly influenced by the external magnetic field, axion angle, thickness of coating layer, and incident operating wave frequency. This work could provide valuable theoretical insights into the scattering phenomena of optical waves and find promising applications in optical manipulation, particle radiation force and torque, optical diagnosis, metamaterial structures, and wave optics in random media. Full article

This paper presents a compact magneto-electric dipole (MED) antenna optimized for wideband circularly polarized (CP) radiation for 5G applications. It incorporates a staircase-shaped electric dipole with trimmed corners to excite orthogonal modes for enhanced CP performance. The proposed single-layer MED antenna achieves a $20.6\%$ wide-impedance bandwidth ($|S_{11}| <-10$ dB, $22.97$–$28.12$ GHz) and $21.9\%$ CP bandwidth ($AR<3$ dB, $22.23$–$27.83$ GHz) with a compact footprint of $15\times 15\times 1.6{\mathrm{mm}}^3$. There is a symmetrical radiation pattern with a co-to-cross polarization ratio $>23$ dB and a stable gain of $8.8$ dBi. An equivalent circuit model is optimized via particle swarm optimization (PSO). The optimized MED antenna is utilized to investigate various CP-MIMO configurations and wideband sequential arrays. Next, a $1\times 2$ CP-MIMO antenna system is developed, employing polarization diversity in parallel and mirror configurations. Isolation is improved by etching a ground slot between the MED elements, yielding isolation levels of below $-20$ dB and $-23$ dB, respectively. Further, a $2\times 2$ CP-MIMO configuration is designed and evaluated. This arrangement demonstrates an envelope correlation coefficient (ECC) of $1\times {10}^{-3}$ and a diversity gain of approximately 10 dB across the operating bandwidth. Finally, a sequential array is designed that applies a ${90}^{\circ }$ sequential rotation and phase excitation to MED elements for high-gain CP 5G communications. Here, various array sizes are evaluated, with an $8\times 8$ MED array providing CP radiation ($AR\le 1$ dB) from 20 to 30 GHz with enhanced impedance and axial ratio bandwidths and stable gain with a peak value of $27.47$ dBi. Full article

Asymmetric and symmetric magnetoelectric (ME)-laminated composites with magnetostrictive layer FeNi and piezoelectric layer PZT are prepared. The longitudinal resonance ME voltage coefficient in the symmetric composite is approximately 1.57 times that in the asymmetric composite with same constituents due to the flexural deformation and asymmetric stress distribution in the asymmetric structure. By bonding an additional high-permeability FeSiB, combining FeSiB with FeNi forms magnetization-graded ferromagnetic materials. A stronger maximum ME voltage coefficient, a dual-peak phenomenon, and a self-bias ME effect are observed. The maximum ME voltage coefficients for asymmetric and symmetric composites reach 3.10 V/Oe and 5.67 V/Oe by adjusting the thickness of the FeCuNbSiB layer. The maximum zero-bias ME voltage coefficients for asymmetrical and symmetrical composite materials reach 2.19 V/Oe at 25 µm thickness of FeSiB and 2.87 V/Oe at 75 µm thickness of FeSiB. Such high performances enable the ME composites to possess ideal sensing and make them promising for self-bias current sensor applications. Full article

A multiphysics-coupled 2–2 cement-based magnetoelectric composite model is established in COMSOL 6.2. This model is used to not only systematically investigate the magnetoelectric-coupling behavior, but also quantify the effects of the magnetic field, frequency, and layer-thickness ratio on the material’s magnetoelectric properties. The results demonstrate that the model effectively reproduces the internal stress–strain distribution and voltage evolution. Specifically, the magnetostrictive and piezoelectric layers exhibit mechanical responses with pronounced non-uniformity, which is attributed to boundary effects. The bias magnetic field plays a crucial regulatory role: the output voltage increases linearly from 0 to 2000 Oe and then saturates at higher fields. Under an alternating magnetic field, the composite exhibits pronounced resonance characteristics, whose frequency is jointly governed by structural dimensions and the bias field. The dynamic response was further analyzed using the magnetic flux density modulus, displacement profiles at selected locations, and voltage evolution across the piezoelectric layer. Notably, the thickness of each functional phase exerts a pronounced and distinct influence on the composite’s magnetoelectric coupling, with markedly different trends between phases. Optimization results show that a thin piezoelectric layer combined with a thick magnetostrictive layer yields the highest magnetoelectric performance. Additionally, the longitudinal and transverse magnetoelectric coefficients exhibit markedly different coupling mechanisms—this is owing to the misalignment between the magnetic-field and electric-polarization directions, and this difference further reveals the intrinsic anisotropy of the magnetoelectric response. Overall, this study provides a crucial theoretical foundation for the design and optimization of high-performance cement-based magnetoelectric composites. Full article

This report is on Co and Ti substituted M-type barium and strontium hexagonal ferrites that are reported to be single phase multiferroics due to a transition from Neel type ferrimagnetic order to a spiral spin structure that is accompanied by a ferroelectric polarization in an applied magnetic field. The focus here is the nature of magnetoelectric (ME) interactions in the bilayers of ferroelectric PZT and Co and Ti substituted BaM and SrM. The ME coupling in the ferrite-PZT bilayers arise due to the transfer of magnetostriction-induced mechanical deformation in a magnetic field in the ferrite resulting in an induced electric field in PZT. Polycrystalline Co and Ti doped ferrites, Ba (CoTi)_x Fe_12−2xO_19, (BCTx), and Sr (CoTi)_x Fe_12−2xO₁₉ (SCTx) (x = 0–4) were found to be free of impurity phases for all x-values except for SCTx, which had a small amount of α-Fe₂O₃ in the X-ray diffraction patterns for x ≤ 2.0. The magnetostriction for the ferrites increased with applied filed H to a maximum value of around 2 to 6 ppm for H~5 kOe. BCTx/SCTx samples showed ferromagnetic resonance (FMR) for x = 1.5–2.0, and the estimated anisotropy field was on the order of 5 kOe. The magnetization increased with the amount of Co and Ti doping, and it decreased rapidly with x for x > 1.0. Measurements of ME coupling strengths were conducted on the bilayers of BCTx/SCTx platelets bonded to PZT. The bilayer was subjected to an AC and DC magnetic field H, and the magnetoelectric voltage coefficient (MEVC) was measured as a function of H and frequency of the AC field. For BCTx-PZT, the maximum value of MEVC at low frequency was ~5 mV/cm Oe, and a 40-fold increase at electromechanical resonance (EMR). SCTx–PZT composites also showed a similar behavior with the highest MEVC value of ~14 mV/cm Oe at low frequencies and ~200 mV/cm Oe at EMR. All the bilayers showed ME coupling for zero magnetic bias due to the magnetocrystalline anisotropy field in the ferrite that provided a built-in bias field. Full article

Avalanche hazard prediction remains a crucial task for mountainous regions worldwide. This study presents the development and field testing of a prototype automated avalanche hazard monitoring system designed for the East Kazakhstan region. The system integrates a snow avalanche station (including temperature, humidity, and pressure sensors; a magnetoelectric wind sensor; a data logger; and devices for autonomous operation), a temperature snow measuring rod, an API (application programming interface) service for storing weather and climate parameters in a database, and a web interface. Powered by autonomous solar energy solutions, the system ensures continuous, high-resolution monitoring of key environmental parameters. Using initial test datasets, we analyzed the specific strengths and weaknesses of the developed monitoring system using the example of one avalanche site. Avalanche prediction was performed using regression analysis (logistic regression). The evaluation of the model showed a high forecasting accuracy, with recognition rates exceeding 98%. The obtained regression coefficients can be used to predict avalanches based on meteorological data collected using the proposed equipment. The developed solution holds significant promise for improving avalanche risk management practices and can be expanded for broader application in both national and international contexts. Full article

Composites of ferromagnetic and ferroelectric phases are of interest for studies on mechanical strain-mediated coupling between the two phases and for a variety of applications in sensors, energy harvesting, and high-frequency devices. Nanocomposites are of particular importance since their surface area-to-volume ratio, a key factor that determines the strength of magneto-electric (ME) coupling, is much higher than for bulk or thin-film composites. Core–shell nano- and microcomposites of the ferroic phases are the preferred structures, since they are free of any clamping due to substrates that are present in nanobilayers or nanopillars on a substrate. This review concerns recent efforts on ME coupling in coaxial fibers of spinel or hexagonal ferrites for the magnetic phase and PZT or barium titanate for the ferroelectric phase. Several recent studies on the synthesis and ME measurements of fibers with nickel ferrite, nickel zinc ferrite, or cobalt ferrite for the spinel ferrite and M-, Y-, and W-types for the hexagonal ferrites were considered. Fibers synthesized by electrospinning were found to be free of impurity phases and had uniform core and shell structures. Piezo force microscopy (PFM) and scanning microwave microscopy (SMM) measurements of strengths of direct and converse ME effects on individual fibers showed evidence for strong coupling. Results of low-frequency ME voltage coefficient and magneto-dielectric effects on 2D and 3D films of the fibers assembled in a magnetic field, however, were indicative of ME couplings that were weaker than in bulk or thick-film composites. A strong ME interaction was only evident from data on magnetic field-induced variations in the remnant ferroelectric polarization in the discs of the fibers. Follow-up efforts aimed at further enhancement in the strengths of ME coupling in core–shell composites are also discussed in this review. Full article

A giant magnetoelectric coefficient has been discovered in laminated magnetoelectric composites incorporating piezoelectric and magnetostrictive layers, which reveals a high sensitivity in AC magnetic field detection under a DC bias field. However, the DC-biased magnetoelectric composites are not capable of detecting DC magnetic fields due to the interference with the DC signal to be measured. Here, we demonstrate a portable magnetoelectric gaussmeter based on torque effect that can detect both DC and AC magnetic fields. The proposed gaussmeter is equipped with a magnetoelectric sensor, a charge amplification module, a signal processing circuit, a power module, a data processing program, a display module, etc. The proposed gaussmeter indicates such performance indexes as an intensity range of 0~10 Oe, frequency range of DC~500 Hz, AC detection limit of 0.01 Oe, DC detection limit of 0.08 Oe, and frequency resolution of 1 Hz. Being powered by a power adapter (or a battery) of 5V 2A, the whole device system is pocket-size, low-cost, and highly portable, demonstrating its potential for magnetic field detection as a distributed sensor. Full article

In this work, a tachometer based on a Metglas/PZT/Metglas magnetoelectric (ME) composite was developed to achieve high-precision rotational speed measurement over a wide temperature range (−70 °C to 160 °C). The tachometer converts external magnetic signals into electrical signals through the ME effect and operates stably in extreme temperature environments. COMSOL Multiphysics software was used for simulation analysis to investigate the ME response characteristics of the composite in such environments. To evaluate the properties of the ME composite under different conditions, its response characteristics at various frequencies, DC bias, and temperatures were systematically investigated. A permanent magnet and a DC motor were used to simulate gear rotation, and the voltage output was analyzed by adjusting the position between the sensor and the DC motor. The results show that the measured values of the ME tachometer closely match the set values, and the tachometer demonstrates high measurement accuracy within the range of 480 to 1260 revolutions per minute (rpm). Additionally, the properties of the ME composite at different temperatures were examined. In the temperature range from −70 °C to 160 °C, the ME coefficients exhibit good regularity and stability, with the measured trend closely matching the simulation results, ensuring the reliability and accuracy of the ME tachometer. To verify its practicality, the measurement capability of the ME tachometer was comprehensively tested under extreme temperature conditions. The results show that in high-temperature environments, the tachometer can accurately measure speed while maintaining a high signal-to-noise ratio (SNR), demonstrating excellent anti-interference ability. The proposed ME tachometer shows promising application potential in extreme temperature conditions, particularly in complex industrial environments that require high reliability and precision. Full article

Using Green’s function theory and a microscopic model, the multiferroic properties of ${\mathrm{Co}}_4{\mathrm{Nb}}_2{\mathrm{O}}_9$ are investigated theoretically. There are some discrepancies in the discussion of the electric and dielectric behavior of CNO with and without external magnetic fields. We try to clarify them. It is observed that the polarization and the dielectric constant do not show a peak at the antiferromagnetic phase transition temperature $T_N$ without an external magnetic field h. But applying h, there appears a peak around the Neel temperature $T_N$, which increases with increasing h and then shifts to lower temperatures. The magneto-dielectric coefficient MD$(T,h)$ is also calculated. Moreover, the magnetization rises with an increasing external electric field below the Neel temperature. This shows strong magnetoelectric coupling in ${\mathrm{Co}}_4{\mathrm{Nb}}_2{\mathrm{O}}_9$. The obtained results are compared with the existing experimental data. There is a good qualitative agreement. Full article

Improving the hardness and wear resistance of die cutting tools is an important issue in the study of the service life of die cutting equipment. Using laser cladding technology, nickel-based composite coatings with varying BiFeO₃ contents were prepared on a 45 steel substrate, because BiFeO₃ can have an effect on the dilution rate and microstructure of the sample; morover BiFeO₃ is a new type of multiferroic material with certain magneto-electric coupling effects which can be prepared for the study of added magnetic fields. The microstructure and morphology were characterized to determine the optimal BiFeO₃ content. Based on the optimal addition of BiFeO₃, a comparative analysis was conducted to investigate the effect of different magnetic field strengths under a composite energy field on the microstructure, hardness, and wear resistance of Ni-based WC cladding layers. The results show that the optimal addition of BiFeO₃ was 5 wt%. At this concentration, there were no significant porosity defects in the coating, and the dilution rate was appropriate (4.77%). Additionally, the interface bonding strength was also increased. With optimal BiFeO₃ addition, stirring with different magnetic field strengths was applied to the cladding layer, and the results show that the aspect ratio of the cladding layer gradually increased with increasing the alternating magnetic field strength. When the magnetic field strength in the composite energy field was 40 mT, the microstructure was fine and uniform, the hardness of the cladding layer reached the highest level, about 925.2 HV_1.0, the wear resistance was also the best, the friction coefficient of the cladding layer was about 0.54, and the width of the wear mark was about 0.53 mm. Full article

This report is on magneto-electric (ME) interactions in bulk composites with coaxial fibers of nickel–zinc ferrite and PZT. The core–shell fibers of PZT and Ni_1−xZn_xFe₂O₄ (NZFO) with x = 0–0.5 were made by electrospinning. Both kinds of fibers, either with ferrite or PZT core and with diameters in the range of 1–3 μm were made. Electron and scanning probe microscopy images indicated well-formed fibers with uniform core and shell structures and defect-free interface. X-ray diffraction data for the fibers annealed at 700–900 °C did not show any impurity phases. Magnetization, magnetostriction, ferromagnetic resonance, and polarization P versus electric field E measurements confirmed the ferroic nature of the fibers. For ME measurements, the fibers were pressed into disks and rectangular platelets and then annealed at 900–1000 °C for densification. The strengths of strain-mediated ME coupling were measured by the H-induced changes in remnant polarization P_r and by low-frequency ME voltage coefficient (MEVC). The fractional change in P_r under H increased in magnitude, from +3% for disks of NFO–PZT to −82% for NZFO (x = 0.3)-PZT, and a further increase in x resulted in a decrease to a value of −3% for x = 0.5. The low-frequency MEVC measured in disks of the core–shell fibers ranged from 6 mV/cm Oe to 37 mV/cm Oe. The fractional changes in P_r and the MEVC values were an order of magnitude higher than for bulk samples containing mixed fibers with a random distribution of NZFO and PZT. The bulk composites with coaxial fibers have the potential for use as magnetic field sensors and in energy-harvesting applications. Full article

Pure Bi₇Fe₃Ti₃O₂₁ ceramic material and gadolinium ion (Gd³⁺)-doped ones were prepared by solid-state reaction method using simple oxides. The findings of the XRD measurements confirmed the initial author’s assumption that the dopant ions substituted in perovskite blocks influenced the dimensions of the unit cell parameters. All obtained materials are single-phase and show an orthorhombic structure with the Fm2m space group. Microstructure studies show that the admixture gadolinium doping changes the microstructure of the base material, changing grain shapes from plate-like to rounded. The temperature dependences of the electric permittivity have shown the existence of a maximum, the temperature location of which depends on both the frequency and the concentration of Gd³⁺ ions. The highest values of electric permittivity were characteristic of the material with an admixture of Gd³⁺ ions in the amount of x = 0.6 (f = 1 kHz), and the lowest values were for material with x = 0.2 (f = 1 kHz). Studies of the magnetoelectric effect have shown that the strongest coupling between magnetic and electrical properties was demonstrated by a material doped with Gd³⁺ ions in the amount of x = 0.2, for which the magnetoelectric coupling coefficient is equal to α = 12.58·10⁻⁹ s/m. Full article

The search for novel materials with enhanced characteristics for the advancement of flexible electronic devices and energy harvesting devices is currently a significant concern. Multiferroics are a prominent example of energy conversion materials. The magnetoelectric conversion in a flexible composite based on a piezopolymer layer and a magnetic elastomer layer was investigated. The study focused on investigating the dynamic magnetoelectric effect in various configurations of external alternating and constant homogeneous magnetic fields (L-T and T-T configurations). The T-T geometry exhibited a two orders of magnitude higher coefficient of the magnetoelectric effect compared to the L-T geometry. Mechanisms of structure bending in both geometries were proposed and discussed. A theory was put forward to explain the change in the resonance frequency in a uniform external field. A giant value of frequency tuning in a magnetic field of up to 362% was demonstrated; one of the highest values of the magnetoelectric effect yet recorded in polymer multiferroics was observed, reaching up to 134.3 V/(Oe∙cm). Full article