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.

The development of advanced magnetoelectric (ME) composites necessitates high-performance materials that are capable of achieving high levels of ME coupling, minimal magnetic loss, and absence or limited reliance on external excitation sources. In this paper, a (2-2) connectivity ME laminate integrates multiple layers of FeSiB alloy (Metglas) and Pb (Mg, Nb) O3-PbTiO3 (PMN-PT) single crystal, achieving a remarkable ME coupling coefficient of 2033.4 V/Oe·cm (sevenfold rise) by laser thermal annealing treatment. Here, the laser-induced nanostructures on Metglas, with an oxidized insulation layer and soft and hard magnetic dipole layer improve the Magneto-electric-mechanical coupling with a mechanical quality factor (Qm) exceeding 350. More importantly, the interaction between amorphous and nanocrystalline dipoles triggers an Exchange Bias (EB) effect, leading to a self-biasing performance of 67.45 V/Oe·cm. Furthermore, the composite exhibits an excellent passive DC magnetic detection limit of 22 nT, and an improved weak AC magnetic detection limit down to 383 fT. These explorations offer the potential to enhance passive current measurement, and underwater communication, extend weak magnetic positioning and brain magnetic detection.

Acoustically actuated magnetoelectric (ME) antennas based on resonant magnetoelectric coupling within ferromagnetic/piezoelectric ME laminated composites have recently been considered as a promising solution for antenna miniaturization. However, its radiation performance has been theoretically overestimated, since the negative effects on performances due to the magnetization saturation and the nonlinear mechanical behavior that occur from high-field driving have not been paid enough attention. This work presents a unique equivalent-circuit-based numerical method to analyze the near-field resonance radiation performances of ME antennas driven by high electric fields. In this method, we establish an equivalent circuit of the converse magnetoelectric effect for a ME laminated composite to describe the operating principle of acoustically actuated electromagnetic radiation. The equivalent parameters related to resonance characteristics are determined by fitting the circuit model to the data from frequency response measurements of the near-field magnetic flux density. The validity of the model is verified by comparing the theoretical predictions with the experimental results, in the view of the volume fraction dependence of the mechanical resonance-related radiation characteristics of the fabricated ME composites. Based on the proposed model, the influence of driving voltage amplitude on near-field radiation performances is further analyzed by experimental fitting to the model, and the potential limiting factors of ME antennas are discussed according to the driving-amplitude dependence of parameters obtained from the fit. This work provides an effective and engineering-friendly approach to predict the evolution of ME antenna performances, leading a way to improve the performance limit for resonant magnetoelectric coupling.

In this work, a portable very low frequency (VLF) communication system based on magnetoelectric (ME) antennas is proposed. Based on hardware/software codesign, an efficient communication link tailored for VLF ME antennas realizes the transmission of multimedia files, such as pictures, characters, and music. The experimental results demonstrate the feasibility of using VLF ME antennas for cross-media communication, which also provide experimental evidence to support VLF cross-media communication.

Recently, piezoelectrically driven resonant magnetoelectric sensors have attracted increasing interest owing to their high sensitivity, compact size, and low power consumption. Here, we theoretically demonstrate the magnetic sensing performances of using the magnetic field-dependent magnetomechanical effects in a thin-film piezoelectric-on-silicon (TPoS) resonator. Equivalent circuit models are established to describe the sensing and intrinsic thermal noise characteristics of the mechanical resonator. In addition, the thermal-magnetic noise due to magnetic losses of magnetostrictive films is also considered into the modeling. Based on the signal and noise model, the influence of mechanical quality factor is analyzed in different driving cases. It is concluded that the limit of detection (LOD) can be significantly improved by increasing the quality factor in the case of low voltage driving, while the enhancement of quality factor has little effect on improving the LOD in the case of higher voltage driving, implying the importance of magnetic noise suppression.

For the application of high-frequency current detection in power systems, such as very fast transient current, lightning current, partial discharge pulse current, etc., current sensors with a quick response are indispensable. Here, we propose a high-frequency magnetoelectric current sensor, which consists of a PZT piezoelectric ceramic and Metglas amorphous alloy. The proposed sensor is designed to work under d15 thickness-shear mode, with the resonant frequency around 1.029 MHz. Furthermore, the proposed sensor is fabricated as a high-frequency magnetoelectric current sensor. A comparative experiment is carried out between the tunnel magnetoresistance sensor and the magnetoelectric sensor, in the aspect of high-frequency current detection up to 3 MHz. Our experimental results demonstrate that the d15 thickness-shear mode magnetoelectric sensor has great potential for high-frequency current detection in smart grids.

Mechanical antennas that are driven by external mechanical oscillation and acoustic self-resonance have been demonstrated for portable very low-frequency (VLF) electromagnetic (EM) wave transmitting. However, the mechanical relaxation, caused by the energy transition between mechanical and EM energies during signal modulation, limits the modulation rate of mechanical antennas. Here, we use direct antenna amplitude modulation (DAAM) to enhance the modulation rate of the proposed magnetoelectric (ME) antenna. First, we construct a nonlinear converse ME (CME) equivalent circuit model to optimize the dc magnetic field and operating frequency. The relaxation of Young's modulus of the magnetic layer is gradually eliminated with the increase of modulation rate until Young's modulus and radiation intensity of the ME antenna are no longer changed. Ideally, the modulation rate of DAAM is half of the carrier rate, but the actual value is lower than the ideal value due to the overshoot and ringing from the modulation coil. Under the carrier frequency of 27.6 kHz and the modulation frequency of 6 kHz, the bit rate of DAAM reaches up to 12 kbps, which is six times higher than that of the conventional electrical modulation. Our work demonstrates the potential of portable ME antenna for practical high-rate VLF EM communication.

Very low frequency (VLF, 3-30 kHz) electromagnetic (EM) waves are widely used in areas such as mining, underwater communications, etc., because of their relatively large skin depth that enables long-distance propagation in a lossy medium. Mechanical antennas driven by acoustic oscillation or external mechanical movements have been proven to be promising candidates for low-frequency (LF) transmitters. Unfortunately, the mechanical relaxation in modulation caused by the motion inertia of mechanical antennas limits modulation rates. Here, we developed a high-rate active phase modulation (APM) scheme that can eliminate the mechanical relaxation and approach the theoretical maximal bit rate in a magnetoelectric (ME) antenna. The proposed ME antenna is based on a three-layered acoustic resonator with a length of only 8 cm and a total efficiency of 3.59x10(-14) , which is closer to Chu's limit. The proposed APM is realized by the 180 degrees phase reversal of the bias magnetic field provided by a modulating coil. The high bit rate of 18 kbps at the resonant frequency of 27.75 kHz is demonstrated by using APM, one order of magnitude higher than that of passive phase modulation (PPM) due to the effective suppression of mechanical relaxation in such 180 degrees phase variation.

Magnetostrictive/piezoelectric composite structures with novel magneto-electric transduction mechanism have been used to design portable antennas. To simplify the analysis of the multi-field coupling within the magnetoelectric (ME) composites, a lumped equivalent circuit model with electromagnetic duality is proposed in this work. Based on the model, the transceiver performances of ME antennas operating in dual mechanical resonance modes are studied and the lumped parameters are extracted to calculate the transmission characteristics of the ME antenna pair. Both the calculation and experimental results suggest that the transmission performance can be significantly improved by the inductor matching of the ME receiver.

Magnetoelectric (ME) composites exhibit extremely high sensitivity for magnetic field at the fixed resonant frequency, due to the strong strain-mediated ME coupling. However, wideband magnetic field detection is still challenging, as the ME coefficient depends strongly on the frequency. In this work, we propose a magnetoelectric sensor composed of three ME units in series/parallel connections, which works at dual modes to extend the frequency range with high signal-to-noise ratio (SNR). The SNR is enhanced by about 22.68 dB and the bandwidth is broadened from 100 Hz to 1 kHz, with a high sensitivity for frequency conversion mode by series/parallel connections. Limits of detections (LoDs) as low as 207 pT and 460 pT are demonstrated at 1 kHz and 100 kHz, respectively, showing promising applications in wideband magnetic field detection.

To investigate the impact of structural damages on the comfort level of suspension footbridges under human-induced vibrations, this study addresses the limitations of traditional manual testing, which often entails significant manpower and material resources. The aim is to achieve rapid estimation and health monitoring of comfort levels during bridge operation. To accomplish this, the study combines finite-element simulation results to establish a data-driven library and introduces three distinct machine learning algorithms. Through comparative analysis, a machine learning-based method is proposed for quick evaluation of bridge comfort levels. Focusing on the Yangjiadong Suspension Bridge, the study evaluates and researches the comfort level of the structure under the influence of human-induced vibrations. The findings revealed a relatively low base frequency and high flexibility. Additionally, when considering the mass of individuals, peak acceleration decreased. The predictive performance of the Artificial Neural Network (ANN) model was found to be superior when accounting for multi-parameter damages, yielding root mean square error (RMSE), mean absolute percentage error (MAPE), and R-squared (R2) values of 0.03, 0.02, and 0.98, respectively. Moreover, the error ratio of the generalization performance analysis was below 5%. Furthermore, the study identified a damage coefficient of 0.13 for the bridge’s main cable, hanger, and steel longitudinal beam. Under a crowd density of 0.5 people per square meter, the predicted peak acceleration was 1.098 m/s2, with a model error of less than 10% compared to the observed value of 1.004 m/s2. These results underscore the model’s effectiveness in swiftly evaluating bridge comfort levels, thereby offering valuable insights for the health monitoring of bridge comfort levels.

Magnetoelectric (ME) sensors based on piezoelectric/ferromagnetic composites have been investigated extensively due to their resonance-enhanced ME coupling effect and high sensitivity for magnetic field, especially at resonant frequency. However, the sensitivity drops rapidly when the frequency drifts away from resonance, making it unsuitable for low-frequency applications. Frequency modulation has been proposed as an effective method to up-convert the frequency of the desired signal into the mechanical resonance. In this work, we study the optimized amplitude and frequency of the modulation field, which improve the sensitivity at low frequency by two orders of magnitude without increasing the noise level. Magnetic field of 200 pT is detected at 10 Hz with a near-flat frequency response in the range of 1–100 Hz, showing promising potential for low-frequency applications in smart grid and renewable energy.

Finding an efficient way for underwater communication with a portable antenna at very low frequency (VLF 3–30 kHz) is challenging since the conventional electrical antennas require the size to be larger than 1/10 of the wavelength. Recently, acoustically driven antennas were proposed to realize portable VLF communication in air but lack the demonstration in a lossy environment. Here, we reported the first VLF underwater communication system based on a pair of acoustically actuated magnetoelectric (ME) antennas with small size of 10 cm in length. A theoretical analysis of reflection and radiation performance of the ME antenna was conducted, where the electromechanical resonance (EMR) frequency and effective magnetic dipole moment were estimated, and a near-field coupling model of a pair of ME antennas was further established. The results of theoretical predictions and finite element model (FEM) simulations were then compared with experimental measurements and their differences were discussed. A prototype of underwater communication system based on the ME antenna pair was finally presented, where a binary digital modulation with a bit rate of 100 b/s has been demonstrated, confirming the feasibility of ME antennas for portable underwater communication.

A magnetoelectric (ME) sensor of face-shear type is demonstrated based on the ME composite consisting of (PbMg $_{{0}.{33}}$ Nb{0}.{67}O{3}}{)}_{{1}-{x}-(PbTiO $_{{3}}{)}_{x}$ piezoelectric single crystal (abbreviated as PMN-PT) and Metglas amorphous alloy. The face-shear strain is induced in PMN-PT via the magnetostriction of Metglas under a magnetic field, which generates an ME voltage through the ${d}_{{36}}$ piezoelectric coefficient. The proposed sensor reveals a high ME coupling coefficient of 48.8 V/cm Oe at resonant frequency ( $\sim $ 107.5 kHz), which is self-biased with the capability to detect ac magnetic fields of 4.58 nT at 1 kHz and 10.43 pT at resonant frequency, respectively. The self-biased face-shear mode ME sensor exhibits great potential for weak magnetic field detection.

The flexible electronics have application prospects in many fields, including as wearable devices and in structural detection. Spintronics possess the merits of a fast response and high integration density, opening up possibilities for various applications. However, the integration of miniaturization on flexible substrates is impeded inevitably due to the high Joule heat from high current density (1012 A/m2). In this study, a prototype flexible spintronic with device antiferromagnetic/ferromagnetic heterojunctions is proposed. The interlayer coupling strength can be obviously altered by sunlight soaking via direct photo-induced electron doping. With the assistance of a small magnetic field (±125 Oe), the almost 180° flip of magnetization is realized. Furthermore, the magnetoresistance changes (15~29%) of flexible spintronics on fingers receiving light illumination are achieved successfully, exhibiting the wearable application potential. Our findings develop flexible spintronic sensors, expanding the vision for the novel generation of photovoltaic/spintronic devices.

The domain structure fundamentally determines the piezoelectric/ferroelectric performance of ferroelectric materials. To understand the correlation between macro-properties and microstructure, the evolution of domain structure should be clearly figured out. Here, the diffraction-plane-transformation (DPT) model is proposed for the domain evaluation in BS-PT piezoelectric ceramics of rhombohedral crystalline structure. The transformation between different crystal planes is accurately revealed by the DPT model. Then, non-180° domain reversal in rhombohedral 0.4BiScO3–0.6PbTiO3 piezoelectric ceramics (abbreviated as BS-PT) can be quantitatively estimated, whether in electric poling or thermal depoling processes. Experimentally, the correlations between piezoelectric coefficients, electromechanical coupling properties, and non-180° domain reversal percentage are investigated. It is proven that the DPT model provides an effective method for the non-180° domain estimation in rhombohedral crystalline ceramics.

Very low frequency (VLF) is a characteristic frequency band in the radio spectrum. Due to its large skin depth, the signal can penetrate through water and rock, with strong anti-interference ability and long propagation distance. It is gradually applied in underwater communication and geological exploration. Mechanical antennas that driven by external mechanical driving and acoustic self-resonance have been proved to be excellent in VLF electromagnetic (EM) wave signal transmitters. However, mechanical relaxation caused by the signal modulation during resonator energy switching limits the modulation rates of ME antennas. As widely recognized, direct Antenna Modulation (DAM) can solve this problem effectively. This paper reports a portable VLF magnetoelectric (ME) antenna and a novel DAM, i.e., amplitude Shift Keying (ASK), which can eliminate the mechanical relaxation during modulation. The proposed magnetoelectric (ME) antenna is based on a three-layered acoustic resonator structure, with a length of 8 cm, (one-millionth of the EM wavelength). The amplitude switching in the proposed DAM-ASK is achieved by switching the bias magnetic field provided by the modulation coil. The measured bit rate of DAM-ASK is up to 12kbps (f mod = 6 kHz, while f carrier = 27.68 kHz), which is 6 times higher than that of normal modulation.

Magnetoelectric (ME) composites are found to be sensitive to both the intensity and the orientation of external magnetic field, therefore, they have been developed as compasses for in-plane AC magnetic field detection. However, the angular sensitivity of ME compasses is still low compared to other compasses, due to their insensitive resonant mode and poor coupling structure. Here, we propose a ME compass working at L-T mode by using a Metglas/PZT composite that integrated with a calibration algorithm. Detection of the intensity and di-rection of in-plane AC magnetic field is demonstrated synchronously with intensity and angle sensitivities of 0.001 Oe and +/- 0.1 degrees, respectively. In addition, when the calibration algorithms are applied, the angular sensi-tivity is significantly enhanced to +/- 0.02 degrees, one order of magnitude higher than that of other reported ME compasses, demonstrating a great potential for applications in magnetic positioning, magnetic field calibration, and other magnetic detection technologies.

A magnetic field sensor consisting of a surface acoustic wave (SAW) generator and a cantilever beam with NdFeB permanent magnets are developed. The working principle of this magnetic sensor relies on the center frequency shift of the SAW device under the magnetic field as a consequence of the torque-effect-induced deformation of the cantilever, which changes the stress on the piezoelectric LiNbO 3 and the spacing between the interdigital transducers (IDTs). Compared with other magnetic sensors based on acoustic resonance, the performance of our proposed sensor is greatly enhanced due to the structural design by incorporating the magnetic torque effect. High sensitivity of 1277.69 kHz/Oe and a large percentage change in frequency of 5.177% are achieved in this magnetic sensor near a resonant frequency of 848 MHz. The proposed magnetic sensor based on SAW and torque effect exhibits great potential for applications in magnetic field detection.

Exchange bias between ferromagnetic and antiferromagnetic layers has been widely utilized in spintronic devices. Controlling the exchange bias in magnetic multilayers by an electric field (E-field) has been proposed as a low-power solution for manipulating the macroscopic properties such as exchange bias fields and magnetization values, while how the magnetic domains respond to the E-fields has rarely been reported in an exchange-biased system. Here, we realize the vector imaging of reversible electrical modulation of magnetization reversal in exchange-biased CoFeB/IrMn/PMN-PT (011) multiferroic heterostructures, utilizing in-situ quantitative magneto-optical Kerr effect (MOKE) microscopy. Under the electrical control, magnetic domains at −80 Oe rotate reversibly between around 160° and 80°–120°, whose transverse components reverse from 225° to 45° correspondingly. Moreover, pixel-by-pixel comparisons are conducted to further imply the reversible magnetization reversal by E-fields. E-field-induced reversible magnetization reversal is also demonstrated without applying external magnetic fields. Vector imaging of electrical manipulation of exchange bias is of great significance in understanding the magnetoelectric effect and the development of next-generation spintronic devices.