Magnetoelectric Sensors Research Articles

Low Frequency Magnetoelectric Sensor Without Bias Using Laminated Metglas/Quartz/Metglas Structure

Tremendous progress has been made on boosting the performance of magnetoelecric sensor to detect low frequency magnetic field signal by frequency multiplication based on magnetolectric composites. In this paper, a novel magnetoelectric sensor based on the laminated Metglas/piezoelectric quartz crystal/Metglas composites structure is presented. The Metglas foils are bonded symmetrically on both sides of the X-cut quartz crystal plate with epoxy. Experiments showed that the ME composites sensor was able to achieved a limit of detection of 11 pT for a low frequency magnetic field 1 Hz without any bias field through frequency multiplication method. The noise power spectrum density of the sensor has also been tested to be 3.93·10-6 V/Hz1/2 at 1 Hz. The results indicate that the proposed sensor has favorable features, which provides a cost-effective and high-performance approach for low frequency magnetic field measurement. Keywords: Low frequency, limit of detection, magnetoelectric sensor, piezoelectric quartz crystal.

Synthesis and characterization of flexible hybrid sandwich type of multiferroic P(VDF-TrFE)/CoFe2O4/BaTiO3 composite films

In this paper, we report on synthesis magnetoelectric (ME) sandwich type of BaTiO3-P(VDF-TrFE)/CoFe2O4-P(VDF-TrFE)/BaTiO3-P(VDF-TrFE) flexible composite. Nanoparticles of CoFe2O4 (35–40 nm) and BaTiO3 (110–130 nm) were chemically synthesized and then mixed severally with P(VDF-TrFE) copolymer. The sandwich type sample was fabricated using simple cast molding and blending techniques. Structural studies confirmed the phases and the formation of the sandwich magnetoelectric composite. The film showed good ferroelectric and ferromagnetic properties. The enhancement of the magnetoelectric effect for the composite is due to the good isolating circumstances of the piezomagnetic cobalt ferrite phase as well as the proper contact and bonding between the magnetostrictive and electrostrictive phases. The fabricated film could be a potential candidate for different magnetoelectric applications and sensors technology.

Magnetoelectric sensor for non-destructive testing

An original design of a magnetoelectric sensor for non-destructive testing (MSFNDT) is presented. A comparative analysis of the MSFNDT operation is carried out and the advantages in terms of technical and economic indicators are shown. A mathematical model with further theoretical calculations and analysis of the obtained analytical expressions with graphic-analytical images is developed. Experimental studies on propotype physical samples are carried out and the obtained theoretical positions are confirmed. The prospects of introducing the original design during flaw detection in the oil and gas industry are substantiated. Keywords eddy current transducers, longitudinal and transverse defects, error, a magnetic field, mathematical model, signal winding

Split-core magnetoelectric current sensor and wireless current measurement application

This paper proposed a split-core magnetoelectric current sensor consisting of a symmetric Terfenol-D/PZT/Terfenol-D composite, three magnetic core, a pair of permanent magnets and a packaging shell. The Terfenol-D/PZT/Terfenol-D element and three magnetic cores are connected in series to form a closed magnetic ring. In practical application, the sensor can be opened and closed during installation. For detecting the 50 Hz current, the detection sensitivity reaches 52.79 mV/A with R2 = 0.9988 in range of 10A to 1000A. In order to realize the wireless and self-powered measurement of current, this paper proposed a wireless current measurement system combining the split-core current sensor, a RMS detection module, a 4G-RTU module, a current transformer energy harvester and a monitoring platform. Within the allowable error range, the proposed measurement system can realize the wireless measurement of 50 Hz current. These results show that the proposed split-core magnetoelectric current sensor is expected to provide a new idea about current on-line monitoring for Internet of Things in Power Systems, which is of great significance and application.

Active Magnetoelectric Motion Sensing: Examining Performance Metrics with an Experimental Setup.

Magnetoelectric (ME) sensors with a form factor of a few millimeters offer a comparatively low magnetic noise density of a few / in a narrow frequency band near the first bending mode. While a high resonance frequency (kHz range) and limited bandwidth present a challenge to biomagnetic measurements, they can potentially be exploited in indirect sensing of non-magnetic quantities, where artificial magnetic sources are applicable. In this paper, we present the novel concept of an active magnetic motion sensing system optimized for ME sensors. Based on the signal chain, we investigated and quantified key drivers of the signal-to-noise ratio (SNR), which is closely related to sensor noise and bandwidth. These considerations were demonstrated by corresponding measurements in a simplified one-dimensional motion setup. Accordingly, we introduced a customized filter structure that enables a flexible bandwidth selection as well as a frequency-based separation of multiple artificial sources. Both design goals target the prospective application of ME sensors in medical movement analysis, where a multitude of distributed sensors and sources might be applied.

Application of magnetoelectric sensors in biomedicine

The prospects of applying highly sensitive magnetic field sensors based on the magnetoelectric effect in biomedicine are discussed in this paper. When developing highly sensitive magnetic field sensors, it is necessary to take into account the magnitude of the equivalent magnetic noise, as well as the mass and size dimensions and ease of use of the system that the sensor is included in. One of the most relevant areas discussed in the article is the application of magnetoelectric magnetic field sensors for magnetocardiography, magnetoencephalography, etc. These methods are non-invasive, have high sensitivity and are easy to use. They also have wide opportunities in detecting weak biomagnetic signals when examining the state of the human body and providing the necessary assistance.

Magnetoelectric Magnetic Field Sensors: A Review.

One of the new materials that have recently attracted wide attention of researchers are magnetoelectric (ME) composites. Great interest in these materials is due to their properties associated with the transformation of electric polarization/magnetization under the influence of external magnetic/electric fields and the possibility of their use to create new devices. In the proposed review, ME magnetic field sensors based on the widely used structures Terfenol—PZT/PMN-PT, Metglas—PZT/PMN-PT, and Metglas—Lithium niobate, among others, are considered as the first applications of the ME effect in technology. Estimates of the parameters of ME sensors are given, and comparative characteristics of magnetic field sensors are presented. Taking into account the high sensitivity of ME magnetic field sensors, comparable to superconducting quantum interference devices (SQUIDs), we discuss the areas of their application.

Processing Chain for Localization of Magnetoelectric Sensors in Real Time.

The knowledge of the exact position and orientation of a sensor with respect to a source (distribution) is essential for the correct solution of inverse problems. Especially when measuring with magnetic field sensors, the positions and orientations of the sensors are not always fixed during measurements. In this study, we present a processing chain for the localization of magnetic field sensors in real time. This includes preprocessing steps, such as equalizing and matched filtering, an iterative localization approach, and postprocessing steps for smoothing the localization outcomes over time. We show the efficiency of this localization pipeline using an exchange bias magnetoelectric sensor. For the proof of principle, the potential of the proposed algorithm performing the localization in the two-dimensional space is investigated. Nevertheless, the algorithm can be easily extended to the three-dimensional space. Using the proposed pipeline, we achieve average localization errors between 1.12 cm and 6.90 cm in a localization area of size .

Dependence of Modified Butterworth Van-Dyke Model Parameters and Magnetoimpedance on DC Magnetic Field for Magnetoelectric Composites.

This study investigates the impedance curve of magnetoelectric (ME) composites (i.e., Fe80Si9B11/Pb(Zr0.3Ti0.7)O3 laminate) and extracts the modified Butterworth–Van Dyke (MBVD) model’s parameters at various direct current (DC) bias magnetic fields Hdc. It is interesting to find that both the magnetoimpedance and MBVD model’s parameters of ME composite depend on Hdc, which is primarily attributed to the dependence of FeSiB’s and neighboring PZT’s material properties on Hdc. On one hand, the delta E effect and magnetostriction of FeSiB result in the change in PZT’s dielectric permittivity, leading to the variation in impedance with Hdc. On the other hand, the magnetostriction and mechanical energy dissipation of FeSiB as a function of Hdc result in the field dependences of the MBVD model’s parameters and mechanical quality factor. Furthermore, the influences of piezoelectric and electrode materials properties on the MBVD model’s parameters are analyzed. This study plays a guiding role for ME sensor design and its application.

Effect of Er substitution on the magnetic, Mössbauer spectroscopy and dielectric properties of CoFe2−xErxO4 (x = 0.00, 0.01, 0.03, 0.05) nanoparticles

The effect of Er content on sol-gel derived CoFe2−xErxO4, (x = 0.00, 0.01, 0.03, 0.05) nanoparticles was investigated by XRD, FTIR, SEM, Mössbauer spectroscopy, magnetic and dielectric measurements. The formation of cubic spinel structure and the presence of molecular bonding of functional groups were confirmed by XRD and FTIR spectroscopy. The average crystallite size is reduced from 61 to 18 nm with the increase of Er content. The decrease in crystallite size is due to the suppression of grain growth upon Er3+ occupation at the octahedral site. SEM study revealed the formation of nano size particles which dispersed uniformly. Mössbauer spectra, taken at room temperature (RT) confirmed the presence of ferromagnetic sextets demonstrating the existence of Fe both in the tetrahedral and octahedral sites. The magnetic properties were measured at 300 K, 100 K and 5 K using a Physical Properties Measurements System (PPMS). The saturation magnetization (Ms) of CoFe2O4 was found to be 95.92 emu/g which is much higher than the bulk ferrite (80.8 emu/g) and the maximum Ms 120 emu/g was found for 0.01 Er content. The coercivity increases with the increase of Er content which has a direct relationship with crystallite size and single-domain behavior of nanoparticles. The maximum coercivity is found to be 855 KA/m at 5 K which is the highest compared to the rare earth doped ferrites. The impedance analysis fallouts the relative permittivity and dielectric loss decrease while AC conductivity increases with increasing frequency for all samples. The obtained results signify CoFe2−xErxO4 as a potential candidate for magneto-electric sensors and high frequency electromagnetic devices application.

Lead-free laminated structures for eco-friendly energy harvesters and magnetoelectric sensors

The ferromagnetic and ferroelectric laminated structure has been utilized to study the magnetoelectric (ME) effect, which holds great potential to fabricate micro-electro-mechanical devices with a high figure of merit. Designed a laminated heterostructure using ribbons of Metglas (Fe–Co–Si–B alloy) having high magnetic permeability and lead-free piezoelectric composites of 0.92(Na0.5Bi0.5)TiO3-0.08BaTiO3 (NBT-BT) to generate the significant magnitude of direct ME voltage. The displacement-voltage measurements of NBT-BT yield a high response showing the nature of the piezoelectricity effect. The strength of ME coupling is determined from the ME voltage coefficient (αME), ME measurements have been carried out in the range of 0–6 kHz frequencies. The magnitude of the direct ME effect was found about 45–50 mV/Oe.cm over a low magnetic field of less than ±8 kOe. The real-time ME effect produced nearly 274.5 and 280.2 mV of ME voltages for the applied field of 200 and 300 Oe, respectively. It shows that the trilayer composite structure may be used as weak magnetic field sensors and energy harvesters.

Ambient effect on the Curie temperatures and magnetic domains in metallic two-dimensional magnets

The emergent magnetic two-dimensional (2D) materials provide ideal solid-state platforms for a broad range of applications including miniaturized spintronics, nonreciprocal optics, and magnetoelectric sensors. Owing to the general environmental sensitivity of 2D magnets, the understanding of ambient effects on 2D magnetism is critical. Apparently, the nature of itinerant ferromagnetism potentially makes metallic 2D magnets insensitive to environmental disturbance. Nevertheless, our systematic study showed that the Curie temperature of metallic 2D Fe3GeTe2 decreases dramatically in the air but thick Fe3GeTe2 exhibits self-protection. Remarkably, we found the air exposure effectively promotes the formation of multiple magnetic domains in 2D Fe3GeTe2, but not in bulk Fe3GeTe2. Our first-principles calculations support the scenario that substrate-induced roughness and tellurium vacancies boost the interaction of 2D Fe3GeTe2 with the air. Our elucidation of the thickness-dependent air-catalyzed evolution of Curie temperatures and magnetic domains in 2D magnets provides critical insights for chemically decorating and manipulating 2D magnets.

Significant improving magnetoelectric sensors performance based on optimized magnetoelectric composites via heat treatment

Laminated magnetoelectric (ME) composites consisting of magnetostrictive and piezoelectric materials have been investigated and proved to realize strong ME coupling, which shows great benefits to fabricate high sensitivity ME magnetic sensors. In this work, optimized L–T mode ME composites consisting of heat-treated Metglas ribbons and [110]-oriented Mn-doped 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 (Mn-doped PMN-PT) single crystal fibers were reported, which achieves giant ME coupling and ultrahigh ME electric field coefficient of 4.26 × 104 V cm−1 Oe−1 at the electromechanical resonance. The equivalent magnetic noise of the ME sensor based on the proposed ME composites is only 2.89 fT Hz−1/2 at the electromechanical resonance, which exhibits great prospect in the application of precision magnetic field detection. Based on the characterization of heat-treated Metglas samples and the finite element simulation of the ME composites, the improved performance of the ME composites and ME sensors can be attributed to the enhanced properties of heat-treated Metglas (higher piezomagnetic coefficient d 33,m, higher induced magnetic flux density and lower mechanical loss) due to the enhancement of nanocrystallization and the stronger magnetic flux concentration effect corresponding to the dimension of the Metglas ribbons.

Improving the performances of PMNT crystals to enhance the responsivity of the magnetoelectric sensors with MPP structure via alternating current polarization

Magnetoelectric (ME) sensors based on coupling principle of “magneto-mechano-electric” have drawn much attention in past few years. With further research, it is proved that the detection capability of the ME sensors with “multi-push-pull” (MPP) structure can reach to the current level of commercial fluxgate, showing a great application prospect in the fields of weak magnetic field detection. In this work, the alternating current polarization (ACP) method is the first to be applied to improve the ME response of ME composites with MPP structure. Poling conditions, including temperature, voltage and frequency, are well discussed in this paper. Moreover, the combination of finite-element simulations and experiments are employed to identify the optimal poling conditions. According to the PFM images, the improvement of piezoelectricity after ACP method may come from the high domain wall densities. Furthermore, two ME sensors with MPP structure prepared by the direct current polarization (DCP) method and the ACP method are compared. ME response in quasi-state condition and resonant condition are both improved, and equivalent magnetic noise (EMN) decreases from 4.07 pT/Hz1/2@1 Hz to 3.62 pT/Hz1/2@1 Hz after the ACP method, demonstrating a significant increase in detection capability.

A working-point perturbation method for the magnetoelectric sensor to measure DC to ultralow-frequency-AC weak magnetic fields simultaneously

Magnetoelectric (ME) sensors for the weak magnetic field measurement have attracted a lot of attention because of their high sensitivity and easy integration. However, the ME sensor performs well only at its working-point under a direct current (DC) bias field (Hbias) and mechanical resonance frequency (fres). The measurement of DC to ultralow frequency (0–100 Hz) weak magnetic fields has increasing demands, such as in geomagnetic anomaly fields, geological and mineral exploration, magnetocardiography, and magnetoencephalography. Unfortunately, fres of ME sensors is on the order of several tens of kilohertz, which is far higher than the ultralow frequency desired. Moreover, if the operation frequency deviates from fres, the sensitivity will deteriorate rapidly. In this study, a working-point perturbation method was used to measure the weak magnetic fields at 0–100 Hz with a high magnetic field resolution. (1) The perturbation of fres using an ultralow frequency (fac) magnetic field results in two modulation peaks with frequencies of fres ± fac. The frequency and resolution of the measured alternating current magnetic field can be obtained by varying fac and the modulation depth. A resolution around 1 nT for fac > 10 Hz and a lowest operation frequency of 0.1 Hz were achieved using our measurement system. (2) A high field resolution of 3 nT (better than the frequency perturbation method with a resolution of 16 nT at 0.1 Hz) can be achieved by the perturbation of Hbias at fres because the ME sensor is still working at the quasi-working-point and helped by lock-in amplifier technology.

Sea urchin-like Ni encapsulated with BaTiO3 to form multiferroic core-shell structures for room temperature magnetoelectric sensors

Since core-shell structures are known to have a high surface area to volume ratio, they are preferred for next-generation memory device applications that require effective strain transfer at the ferroic interface. The present investigation reports the encapsulation of sea urchin-like Ni nanoparticles using BaTiO3 nanoparticles to realize room temperature ME coupled Ni@BaTiO3 system. The magnetic, electric and magnetoelectric properties of Ni nanoparticles partially coated with BaTiO3 provide enough evidence for the existence of ME coupling between Ni and BaTiO3 at their interface. Additionally, we have observed an exchange bias shift upon field cooling, which confirms the presence of the Ni-NiO-BaTiO3 interface in the Ni@BaTiO3 core-shell. The obtained magnetoelectric coupling coefficient of Ni@BaTiO3 composite is 225 µV cm−1 Oe−1. The present study reveals that chemically derived sea urchin-like Ni@BaTiO3 core-shell architecture can be a promising way to design strongly coupled multiferroic memory devices and sensors.

Local Strain Distribution in ZnO Microstructures Visualized with Scanning Nano X‐Ray Diffraction and Impact on Electrical Properties

The fast and contact‐free detection of biomagnetic vital signs can benefit clinical diagnostics in medical care, emergency services, and scientific studies, hugely. A highly sensitive magnetoelectric sensor for the detection of biomagnetic signals combined with the piezotronic effect is a promising path to increase the signal detection limit. Herein, the results of three ZnO microrods examined by nano X‐ray diffraction and current–voltage curves to investigate the crystalline structure influence on the Schottky contact properties are presented. The measurements reveal different strain distributions for the three rods and that these are linked with the electrical properties, showing that the crystalline quality has a direct influence on the Schottky contact properties. An analytical model is created to determine the influence of the stress. Although rotation of the strain orientation changes the strain appearance in the measurement, it does not affect the Schottky contact properties.

Investigation of Magnetoelectric Sensor Requirements for Deep Brain Stimulation Electrode Localization and Rotational Orientation Detection.

Correct position and orientation of a directional deep brain stimulation (DBS) electrode in the patient’s brain must be known to fully exploit its benefit in guiding stimulation programming. Magnetoelectric (ME) sensors can play a critical role here. The aim of this study was to determine the minimum required limit of detection (LOD) of a ME sensor that can be used for this application by measuring the magnetic field induced by DBS. For this experiment, a commercial DBS system was integrated into a head phantom and placed inside of a state-of-the-art Superconducting Quantum Interference Device (SQUID)-based magnetoencephalography system. Measurements were performed and analyzed with digital signal processing. Investigations have shown that the minimum required detection limit depends on various factors such as: measurement distance to electrode, bandwidth of magnetic sensor, stimulation amplitude, stimulation pulse width, and measurement duration. For a sensor that detects only a single DBS frequency (stimulation frequency or its harmonics), a LOD of at least 0.04 pT/Hz is required for 3 mA stimulation amplitude and 60 s pulse width. This LOD value increases by an order of magnitude to 0.4 pT/Hz for a 1 kHz, and by approximately two orders to 3 pT/Hz for a 10 kHz sensor bandwidth. By averaging, the LOD can be reduced by at least another 2 orders of magnitude with a measurement duration of a few minutes.

AC/DC dual-mode magnetoelectric sensor with high magnetic field resolution and broad operating bandwidth

In this study, a dual-mode Metglas/Pb(Zr,Ti)O3 magnetoelectric (ME) sensor was prepared for measuring weak magnetic fields. It is interesting to note that this ME sensor can work at alternating current (AC) and direct current (DC) dual-modes with high field resolution. In AC mode, a very accurate AC magnetic field resolution of 0.8 nT was achieved at a mechanical resonance frequency of 72.2 kHz; moreover, the operating frequency band for resolution better than 1 nT is as wide as 3.4 kHz. We proposed a DC bias field perturbation (DBFP) method to detect the DC magnetic field using lock-in amplifier technology. As a result, an ultra-accurate DC field resolution of 0.9 nT with noise power spectral density as low as 100 pT/Hz was obtained in the studied ME sensor via the DBFP method. The dual-mode ME sensor enables simultaneous measurement for DC and AC magnetic fields with wideband and accurate field resolution, which greatly enhances the measurement flexibility and application scope.

Advances in the modification and device integration of multiferroic bismuth ferrite

As a single-phase multiferroic oxide, BiFeO3 (BFO) is suitable for applications such as magnetoelectric memories, sensors and actuators. However, BFO suffers from high leakage current density and small magnetization. And the BFO in film form is apt to react with Pt bottom electrode during the thermal treatment. In addition, its required high processing temperatures can not be compatible well with the interconnect technologies for semiconductor. In this review, we summarize both the improvement in leakage characteristics and enhancement of magnetic properties of BFO. The effects of buffer layers on properties and device integration of BFO thin films are also introduced.