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This paper presents a study of magnetoelectric (ME) properties of the PZT/Terfenol-D composite with a varying number of layers. The composite consists of piezoelectric and magnetostrictive phases that are mechanically coupled. The purpose of this setup is to gain control over the electric polarization of a material via an external magnetic field. Unlike most similar composites, our samples utilize a commercial piezoelectric patch instead of pure PZT. At present, researchers face two main problems regarding magnetoelectric materials: (i) the effect is observed far below room temperature for single-phase materials, and (ii) the ME coupling is too weak to be commercially viable. Our research was carried out via the lock-in technique on two PZT/Terfenol-D samples we synthesized. Relatively strong room-temperature magnetoelectric coupling between piezoelectric and magnetostrictive phases was observed for both samples. Two types of characteristics were investigated: (i) ME voltage versus magnetic AC field frequency, and (ii) ME voltage versus magnetic DC field. We detected multiple, grouped signal peaks ascribed to different resonance modes. Uniquely, the peaks form band-like characteristics which might be an important step in bringing the materials closer to wider commercial use. [ABSTRACT FROM AUTHOR]

In this work, the mask method is applied to design a variety of topological structures in the magnetic layer. Different topological Mo/FeGa/AlN magnetoelectric (ME) devices were fabricated. Controlling the stress conduction mode between the magnetostrictive phase and the piezoelectric phase is one of the goals that enables the coexistence of normal stress and shear stress. In order to improve the ME performance of devices, the second purpose is to induce the ME anisotropy of devices through the magnetostrictive anisotropy caused by the topological structure. The circular topological Mo/FeGa/AlN devices produce the largest ME coupling coefficient along the length direction (7071 mV/cm Oe), which is 1.84 times higher than that of the planar devices (3853 mV/cm Oe). The maximum ME anisotropy coefficient (4.612) is determined from the strip topology ME device, which is 2.45 times higher than that of the planar device. [ABSTRACT FROM AUTHOR]

A dual-output magnetoelectric (ME) energy harvester consisting of strictly concentric toroidal Ni0.8Zn0.2Tb0.02Fe1.98O4/(Pb0.70Ba0.26Sr0.04)(Zr0.52Ti0.48)O3 (PbaS-4)/Ni0.8Zn0.2Tb0.02Fe1.98O4 composite with solenoid wound around it is presented and developed. In this case, spatial electromagnetic energy from power lines can be scavenged by ME element and the solenoid simultaneously, and then, the output power density was improved due to electromagnetic induction involved. Experimental results show that the maximum induced voltage can reach 15 mV (port I) and 1.2 mV (port II) for open-circuit conditions under the amplitude of 70 mA current driving of 50 Hz. Correspondingly, generated output power for ports I and II reaches 0.4285 and 30.1476 nW at optimum load resistances of 250 and $140~\Omega $ , respectively. Through these study results, new research paths to move forward with enhanced flexibility for device design of magnetic energy harvester in application in power line autonomous monitoring systems. Through these study results, new research paths to move forward with enhanced flexibility for device design of magnetic energy harvester were achieved in application of power line autonomous monitoring systems. [ABSTRACT FROM AUTHOR]

The direct nonlinear magnetoelectric (ME) effect and the magnetostriction of piezoelectric CsCuCl3 single crystals were comprehensively studied over a wide temperature range in stationary magnetic fields of up to 14 T. The direct nonlinear ME effect measurements were also performed in pulsed magnetic fields up to 31 T, at liquid helium temperature in the antiferromagnetic (AF) state for the crystallographic direction in which effect has the maximum value. The nonlinear ME effect was quadratic in the paramagnetic state for the whole range of magnetic fields. In the AF state the phase transition between different configurations of spins manifested itself as plateau-like peculiarity on the nonlinear ME effect. The nonlinear ME effect was saturated by the phase transition to the spin-saturated paramagnetic state. Two contributions to the nonlinear ME effects in CsCuCl3 were extracted from the experimental data: the intrinsic ME effect originated from the magnetoelectric interactions, and the extrinsic one, which resulted from a magnetostriction-induced piezoelectric effect. [ABSTRACT FROM AUTHOR]

A dc magnetoelectric sensor operating in ac voltage driving mode is developed based on a piezoelectric-magnetostrictive heterostructure having four thickness-polarized Pb(Zr, Ti)O3 piezoelectric plates bonded symmetrically on a length-magnetized Tb0.3Dy0.7Fe1.92 magnetostrictive plate to give an electrically parallel input and an electrically series output. The dc magnetic field sensing in the sensor is evaluated theoretically and experimentally and is found to originate from a unique ac voltage-driven, dc magnetic field-tuned resonance dc magnetoelectric effect in the heterostructure. An interestingly high, linear, and negative ac voltage-controlled dc magnetic field sensitivity of -1.3 mV/Oe/V is obtained in a broad range of dc magnetic field of 0-400 Oe by referencing an ac voltage of ⩽5V peak amplitude and 116 kHz frequency at the input of the heterostructure. [ABSTRACT FROM AUTHOR]

Delta-E effect sensors are based on magnetoelectric resonators that detune in a magnetic field due to the delta-E effect of the magnetostrictive material. In recent years, such sensors have shown the potential to detect small amplitude and low-frequency magnetic fields. Yet, they all require external magnetic bias fields for optimal operation, which is highly detrimental to their application. Here, we solve this problem by combining the delta-E effect with exchange biased multilayers and operate the resonator in a low-loss torsion mode. It is comprehensively analyzed experimentally and theoretically using various kinds of models. Due to the exchange bias, no external magnetic bias fields are required, but still low detection limits down to 350 pT / Hz at 25 Hz are achieved. The potential of this concept is demonstrated with a new operating scheme that permits simultaneous measurement and localization, which is especially desirable for typical biomedical inverse solution problems. The sensor is localized with a minimum spatial resolution of 1 cm while measuring a low-frequency magnetic test signal that can be well reconstructed. Overall, we demonstrate that this class of magnetic field sensors is a significant step towards first biomedical applications and compact large number sensor arrays. [ABSTRACT FROM AUTHOR]

Highlights • Development of 1–2 type BaTiO 3 /CoFe 2 O 4 magnetoelectric thin films. • Synthesis of individually free-standing TiO 2 nanotubes via Ti anodizing. • Hydrothermal conversion of BaTiO 3 from TiO 2 nanotubes. • Dense filling of CoFe 2 O 4 in an interspace between BaTiO 3 nanotubes. Abstract In this study, individually free-standing piezoelectric nanotubes-based magnetoelectric thin films were synthesized by complexation of one-dimensional (1D) BaTiO 3 as the piezoelectric phase, and CoFe 2 O 4 as the magnetostrictive phase. Particularly, the individually TiO 2 free-standing nanotubes were developed onto a Ti substrate via metal anodizing to obtain a high standing stability of 1D piezoelectric structure and a filling volume of magnetostrictive phase, simultaneously for fabrication of magnetoelectric thin films. After BaTiO 3 perovskite conversion from the TiO 2 nanotubes, an enough volume still remains for sufficient self-filling of CoFe 2 O 4 between the BaTiO 3 nanotubes. Finally, BaTiO 3 /CoFe 2 O 4 magnetoelectric films were found to exhibit a dense structure being suitable for strong magnetostriction-mediated piezoelectric voltages. The structure design, based on individually free-standing nanotubes, would be feasible for flexible magnetoelectric devices such as health monitoring sensors, energy harvesters, and memory devices. [ABSTRACT FROM AUTHOR]

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We investigated the magnetoelectric properties of a new laminate composite material based on y +140°-cut congruent lithium niobate piezoelectric plates with an antiparallel polarized “head-to-head” bidomain structure and metglas used as a magnetostrictive layer. A series of bidomain lithium niobate crystals were prepared by annealing under conditions of Li2O outdiffusion from LiNbO3 with a resultant growth of an inversion domain. The measured quasi-static magnetoelectric coupling coefficient achieved |αE31| = 1.9 V·(cm Oe)−1. At a bending resonance frequency of 6862 Hz, we found a giant |αE31| value up to 1704 V·(cm Oe)−1. Furthermore, the equivalent magnetic noise spectral density of the investigated composite material was only 92 fT/Hz1/2, a record value for such a low operation frequency. The magnetic-field detection limit of the laminated composite was found to be as low as 200 fT in direct measurements without any additional shielding from external noises. [ABSTRACT FROM AUTHOR]

Lead-free multiferroic composites with enhanced magnetoelectric properties and sensitivity have potential for various multifunctional devices. The magnetoelectric behaviour of CoFe 2 O 4 -(Ba 0.85 Ca 0.15 ) (Zr 0.1 Ti 0.9 )O 3 , (CFO-BCZT) and substituted CFO-BCZT laminate composites prepared by epoxy bonding are investigated in this study. Magnetostrictive CoFe 2 O 4 (CFO) substituted with Ti (CTFO) resulted in a very high piezo-magnetic coefficient (q) of ∼290 × 10 −9  Oe −1 . Lead free piezoelectric (Ba 0.85 Ca 0.15 ) (Zr 0.1 Ti 0.9 )O 3 [BCZT] substituted with Ce 4+ (BCZCT) showed improved piezoelectric coefficients of d 33 ∼ 675 pC/N and g 33 ∼13 mV m/N. Two new trilayer multiferroic laminates were developed with a (2-2) composite connectivity by combining the pure and substituted ferroic phases. Magnetostrictive, ferroelectric, piezoelectric and magnetoelectric properties of CFO-BCZT and CTFO-BCZCT laminate composites were measured and compared in here. CTFO-BCZCT composite exhibited a large magnetoelectric response with a high ME coefficient (α ME ) of ∼950 mV/cm.Oe and also showed an improved magnetoelectric sensitivity at lower magnetic fields, making it a potential lead-free material for magnetoelectric sensing applications. [ABSTRACT FROM AUTHOR]

In this study, we propose a new bilayer-laminated magnetoelectric (ME) composite consisting of magnetostrictive Ni and Tb0.3Dy0.7Fe2 (Terfenol-D) plates and piezoelectric Pb(Zr,Ti)O3 (PZT) plate. The Ni–Terfenol–D-Ni/PZT composite is constructed and compared with the traditional Terfenol-D/PZT composite. The bias magnetic field and the electric field frequency dependences of the converse ME (CME) coefficient were investigated. It is shown that the Ni–Terfenol-D–Ni/PZT exhibits a large CME coefficient of 6.2 × 10−7 s/m at the electric field frequency of 42 kHz under a low bias magnetic field of 230 Oe, which results from the highly concentrated flux induced by Ni and the stress-interaction between Ni and magnetostrictive Terfenol-D. [ABSTRACT FROM AUTHOR]

Aiming to design magnetostrictive/piezoelectric asymmetric bilayer laminate structure that is commonly used in magnetoelectric (ME) sensor, a bilayer static nonlinear magneto-mechanical- electro-thermal coupled theoretical model which is about calculating ME coefficient and sensitivity is established. This model is based on the mechanical-electric linear constitutive relation of piezoelectric layer and one-dimension nonlinear thermal-magneto-mechanical constitutive relation of giant magnetostrictive material (GMM), in which the bending deformation caused by asymmetric structure has also been considered. The model shows universal applicability in the magnetostrictive/piezoelectric bilayer ME structure. In order to verify the validity of the model, magnetostrictive Terfenol-D and piezoelectric PZT are selected to constitute bilayer asymmetric ME composite structure sample, whose static ME coefficient is measured under different temperatures and bias magnetic fields. The model is degenerated to the ME coefficient model without stress, which shows a good predicted result being qualitatively and quantitatively consistent with experimental result confirming the validity of the model. Therefore, the nonlinear effects of pre-stress, bias magnetic field and environmental temperature, thickness ratio, as well as different piezoelectric materials on the ME coefficient and sensitivity were systematically investigated with our established model. The predicted result provides a roadway to improve static ME coefficient and sensitivity of devices by selecting different physic fields, materials, and thickness ratio for designing future ME sensors. [ABSTRACT FROM AUTHOR]

Studying multiferroic magnetoelectrics has been a focus field for the last decade and a half, and the exploration of new materials is one of the several aspects of this quest. Here we report on the synthesis and characterization of NiFe 2 O 4 -based multiferroic composites which employ (Ba,Ca)(Zr,Ti)O 3 as the ferroelectric/piezoelectric component and NiFe 2 O 4 as the magnetostrictive phase. We find that these composites show excellent magnetoelectric properties. Especially the composite with 30 vol% of NiFe 2 O 4 has a converse ME coefficient approximately two times larger than the previously reported one for BaTiO 3 -CoFe 2 O 4 composites. A relationship between the phase connectivity within these composites and the ME properties was explored by the time of flight secondary ion mass microscopy. We believe that our investigation will be helpful for the design of magnetoelectric materials as components of sensors and memory devices. [ABSTRACT FROM AUTHOR]

The properties of Fe–Ga thin films on PZT substrate were investigated in this paper. In the Fe–Ga/PZT (ME) devices the Fe–Ga magnetostrictive films act as a driver, therefore it should exhibit a good magnetic and mechanical properties. During sputtering, Ar pressure was changed and Fe–Ga thin films were obtained. It is shown that there is a strong relationship between the gas pressure and film adherence, conductivity, magnetic, and mechanical properties of Fe–Ga thin films. We found that the Fe–Ga/PZT devices with high Young’s modulus and high permittivity also performance good in the ME coupling test. The ME coefficient was 0.17 V/cm Oe at resonance frequency, although the thickness of Fe–Ga film only was about 300 nm. [ABSTRACT FROM AUTHOR]

Resonance magnetoelectric (ME) responses are investigated for the ME laminate heterostructure consisting of positive magnetostrictive material FeCuNbSiB, negative magnetostrictive material Ni and piezoelectric material PZT-8. On one hand, both a built-in magnetic field induced by the strong magnetic interactions between positive magnetostrictive and negative magnetostrictive materials and an intrinsic anisotropic field with obvious hysteresis and remnant magnetization in Ni layer result in a large zero-biased ME effect. The corresponding zero-biased ME voltage coefficient reaches 10.12 V/Oe (126.5 V/cm Oe), which is about 3 times larger than that of traditional Ni/PZT-8 (NP) laminate. On the other hand, the additional stress produced by the high magnetic permeability FeCuNbSiB layer enhances the magnetostriction of Ni layer and ME response. The corresponding maximum ME voltage coefficient (dVME/dHac) is 12.09 V/Oe (150.87 V/cm Oe) at bias magnetic field H\mathrm {dc} = 4 Oe. It is further found that even a step change of ac magnetic field less than 10−10 T can be clearly distinguished by the proposed ME composite. The value of ME voltage sensitivity to dc magnetic fields (dVME/dH \mathrm {dc}) reaches ~76.7 mV/Oe at H\mathrm {dc}= 5 Oe and H\mathrm {ac} =0.1 Oe. Correspondingly, the proposed laminate heterostructure is able to possess both strong ac and dc magnetic field sensitivities. [ABSTRACT FROM AUTHOR]

Composite structures which show magneto-electric (ME) coupling behavior have a wide range of engineering applications. In this work, a composite structure comprising of a ferroelectric and a magnetostrictive material is taken for investigation. First, the nonlinear responses of the ferroelectric material and the magnetostrictive material are studied separately by experiments. In order to predict the nonlinear response, a thermodynamically consistent macroscopic model is proposed for the ferroic materials. Model parameters are then estimated from the experimental data, and the simulated results based on the proposed model are presented. Results from the theoretical model are in agreement with the experimental data. Subsequently, a homogenization procedure is introduced to find out the nonlinear response of a layered ME composite structure, and the obtained results are discussed. [ABSTRACT FROM AUTHOR]

Size effects have been analyzed in the sensitivity and in the equivalent magnetic noise of three-layered ME sensors, working at the magnetoelastic resonance frequency of the magnetostrictive constituents. These effects have been studied in laminates of 4, 3 and 2 cm long, fabricated with metallic glasses of Fe 64 Co 17 Si 7 B 12 and with the piezoelectric polymer PVDF. It has been observed a decrease in the sensitivity to the applied AC and DC magnetic fields as reducing the length of the sensor. In the same way, the equivalent magnetic noise measurements performed in a mu-metal magnetic shielding chamber show a worsening in the performance of the sensors as reducing their length, ranging from 20 pT/Hz 1/2 for the 4 cm long ME sensor down to 103 pT/Hz 1/2 for the 2 cm one. [ABSTRACT FROM AUTHOR]

This paper describes the modeling of magnetoelectric (ME) effects for disk-type Terfenol-D (Tb0.3Dy0.7Fe1.92)/PZT (Pb(Zr,Ti)O3) laminate composite at low frequency by combining the advantages of the static elastic model and the equivalent circuit model, aiming at providing a guidance for the design and fabrication of the sensors based on magnetoelectric laminate composite. Considering that the strains of the magnetostrictive and piezoelectric layers are not equal in actual operating due to the epoxy resin adhesive bonding condition, the magnetostrictive and piezoelectric layers were first modeled through the equation of motion separately, and then coupled together with a new interface coupling factor kc, which physically reflects the strain transfer between the phases. Furthermore, a theoretical expression containing kc for the transverse ME voltage coefficient αv and the optimum thickness ratio noptim to which the maximum ME voltage coefficient corresponds were derived from the modified equivalent circuit of ME laminate, where the interface coupling factor acted as an ideal transformer. To explore the influence of mechanical load on the interface coupling factor kc, two sets of weights, i.e., 100 g and 500 g, were placed on the top of the ME laminates with the same thickness ratio n in the sample fabrication. A total of 22 T-T mode disk-type ME laminate samples with different configurations were fabricated. The interface coupling factors determined from the measured αv and the DC bias magnetic field Hbias were 0.11 for 500 g pre-mechanical load and 0.08 for 100 g pre-mechanical load. Furthermore, the measured optimum thickness ratios were 0.61 for kc = 0.11 and 0.56 for kc = 0.08. Both the theoretical ME voltage coefficient av and optimum thickness ratio noptim containing kc agreed well with the measured data, verifying the reasonability and correctness for the introduction of kc in the modified equivalent circuit model. [ABSTRACT FROM AUTHOR]

In this work a magnetoelectric (ME) current sensor design based on a magnetoelectric effect is presented and discussed. The resonant and non-resonant type of ME current sensors are considered. Theoretical calculations of the ME current sensors by the equivalent circuit method were conducted. The application of different sensors using the new effects, for example, the ME effect, is made possible with the development of new ME composites. A large number of studies conducted in the field of new composites, allowed us to obtain a high magnetostrictive-piezoelectric laminate sensitivity. An optimal ME structure composition was matched. The characterization of a non-resonant current sensor showed that in the operation range to 5 A, the sensor had a sensitivity of 0.34 V/A, non-linearity less than 1% and for a resonant current sensor in the same operation range, the sensitivity was of 0.53 V/A, non-linearity less than 0.5%. [ABSTRACT FROM AUTHOR]

In this study, a new kind of magnetoelectric (ME) structure is designed with Terfenol-D, PZT-5A and nonmagnetic and nonelectric trestle. The configuration of this ME structure presents “A-line” type, PZT-5A and Terfenol-D are respectively bonded with the trestles, which adopt the knuckle joint assembly. Differently from the conventional ME layered structure, in the new structure, the deformation of the PZT-5A of larger size is driven by a Terfenol-D layer of smaller size at an external magnetic field. Since the driven force is applied at the ends of piezoelectric layer through the trestles, the whole piezoelectric layer can be completely stretched or compressed, and the larger voltage should be induced. For the new ME structure with mica trestle, the maximum value of α E is twice higher than that for the conventional laminated ME structure. Furthermore, a wider range of response frequency is also observed in this structure. For the new ME structure with ABS trestle, the experimental results indicate that the maximum ME voltage coefficient is measured as high as 31.85 V/cm Oe at 405 Oe. [ABSTRACT FROM AUTHOR]

In this manuscript, we examine ways to create multiferroic composites with controlled nanoscale architecture. We accomplished this by uniformly depositing piezoelectric lead zirconate titanate (PZT) into templated mesoporous, magnetostrictive cobalt ferrite (CFO) thin films to form nanocomposites in which strain can be transferred at the interface between the two materials. To study the magnetoelectric coupling, the nanostructure was electrically poled ex situ prior to magnetic measurements. No samples showed a change in in-plane magnetization as a function of voltage due to substrate clamping. Out-of-plane changes were observed, but contrary to expectations based on total PZT volume fraction, mesoporous CFO samples partially filled with PZT showed more change in out-of-plane magnetization than the sample with fully filled pores. This result suggests that residual porosity in the composite adds mechanical flexibility and results in greater magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

In this manuscript, we examine ways to create multiferroic composites with controlled nanoscale architecture. We accomplished this by uniformly depositing piezoelectric lead zirconate titanate (PZT) into templated mesoporous, magnetostrictive cobalt ferrite (CFO) thin films to form nanocomposites in which strain can be transferred at the interface between the two materials. To study the magnetoelectric coupling, the nanostructure was electrically poled ex situ prior to magnetic measurements. No samples showed a change in in-plane magnetization as a function of voltage due to substrate clamping. Out-of-plane changes were observed, but contrary to expectations based on total PZT volume fraction, mesoporous CFO samples partially filled with PZT showed more change in out-of-plane magnetization than the sample with fully filled pores. This result suggests that residual porosity in the composite adds mechanical flexibility and results in greater magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

In this study the frequency dependence of harmonic hysteretic magnetoelectric (ME) effect in magnetostrictive-piezoelectric laminate was investigated. Taking into account the nonlinear magnetostrictive effect and the structural vibration, a ME dynamic model was proposed to quantitatively describe the frequency-dependent hysteretic characteristics. The model was validated by comparing the simulated ME response with experiment at both the quasi-static and high frequency conditions. As the frequency increases, the shape evolution of the ME hysteresis loop from crescent to butterfly and ellipse was observed. Moreover, the influences of the magnetic bias field, damping ratio and magnetostrictive loss factor were also investigated. It was found that the dynamic ME hysteresis was the combined result of competition between the first two orders of harmonic components and the corresponding phase shift. The former was controlled by the frequency doubling and the mechanical resonance effect, and the latter was originated from the magnetostrictive loss and mechanical damping. [ABSTRACT FROM AUTHOR]

A novel magnetoelectric (ME) laminated composite structure is proposed in this work, aiming to provide a good self-vibration cancellation performance under the magnetic field detection environment. The proposed structure consists of two Terfenol-D magnetostrictive alloy plates which are revised and length-magnetized by two NdFeB magnets bonded on the top surface of a thickness-polarized Pb(Zr, Ti)O3 (PZT) ceramic plate with separate electrodes. Experiments have shown that great vibration suppression up to 44 dB under harmonic disturbance was observed. The ME coefficient of the proposed structure also reaches up to ~29 mV/Oe at non-resonance frequency and 758 mV/Oe at resonance frequency of 79 kHz which is ~2 times larger than the traditional L–T Terfenol-D/PZT bilayer configuration of the same scale. Such performance improvement is achieved based on the bi-directional magnetic field bias (HBias) of two NdFeB magnets in magnetostrictive layer, internal in-series electrical wire connection in piezoelectric layer. The proposed design has great potential to be used for industrial applications associated with heavy environmental vibration noise. [ABSTRACT FROM AUTHOR]

This paper investigates the resonant bending-mode response of cantilever magnetoelectric (ME) sensors, with focus on the magnetic behavior in an external applied magnetic field, in a theoretical study. A system of coupled linear elastostatic/elastodynamic and electrostatic/magnetostatic equations is solved using 2-D and 3-D finite-element method simulations. The magnetic field is applied at the boundaries of an air-filled volume, surrounding the whole ME sensor, to consider the geometry-dependent deformation of the magnetic field in the presence of materials with high permeability. The deformation of the magnetostrictive (MS) material is calculated and generates an electric potential across a piezoelectric (PE) layer. Structuring the conductive MS layer is necessary to define a pickup region, if the MS layer is produced on top of the PE layer, to enhance the sensor output. For efficient excitation of the resonant bending mode, the tip of the cantilever also needs to be covered with an MS material. Thus, an air gap is necessary to electrically insulate both MS regions and has to be as small as possible to not decrease the magnetic field penetrating into the MS layer. The induced electric potential across the pickup region is optimized for a Metglas-AlN-Si thin-film ME sensor with an length:width:height ratio of 100:20:3. 2-D simulations are performed showing reasonable agreement in induced voltage with approximately 20% deviation compared with 3-D simulations, but with much lower computation times. [ABSTRACT FROM AUTHOR]

In this paper both linear and nonlinear magnetoelectric (ME) effects have been investigated intensively. In order to obtain magnetic amplification, we fabricated 3 multi-push–pull mode magnetoelectric laminated composites metglas/PMNT/metglas based on dumbbell-shaped metglas. The linear magnetoelectric charge coefficient is enhanced to 2600 pC/Oe at 2 Hz based on dumbbell-shaped metglas and it increases as the end-flange width of the dumbbell-shaped metglas increases at 2 Hz, respectively. Based on these 3 ME composites, we establish an active mode nonlinear modulation system for ME magnetic sensor, the sensitivity of which are enhanced to 80, 100 and 102 pT / √ Hz at 1 Hz for the composites with the end-flange width 20, 15 and 10 mm, respectively, via nonlinear ME　modulation method. Strain distribution simulations illustrate the theoretically accurate amplification of the dumbbell-shaped geometry. The center strains of 3 dumbbell-shaped metglas decrease as the width of end-flanges decreases [ABSTRACT FROM AUTHOR]

To replace lead zirconium titanate in magnetoelectric (ME) composites owing to concerns regarding its toxicity, we investigate the ME coupling in bilayer composites comprising lead-free Li x (K 0.5 Na 0.5 ) 1 − x Nb 1 − y Ta y O 3 (LKNNT) (piezoelectric) and CoFe 2 O 4 (magnetostrictive) phases. We prepare the LKNNT ceramics and measure its piezoelectric coefficient d 31 , a crucial ingredient determining ME couplings, for several Li ( x = 0.03 , 0.035 , 0.04 ) and Ta ( y = 0.15 , 0.2 , 0.25 ) concentrations, and find that the highest d 31 occurs at y = 0.2 for all the values of x studied here. We then evaluate both the transverse ( α E , 31 ) and the longitudinal ( α E , 33 ) low-frequency ME coupling coefficients of our composites, for each the above composition of ( x , y ). At x = 0.03 , we find the usual scenario of α E , 31 and α E , 33 , i.e., the strongest ME coupling occurs when d 31 is maximal, namely at y = 0.2 . On the other hand, interestingly, we also obtain the strongest ME coupling when the LKNNT layer has a relatively weaker d 31 , e.g., at y = 0.25 for x = 0.035 and y = 0.15 for x = 0.04 , following from the interplay of d 31 and other ingredients (e.g., dielectric constant). Our calculated ME couplings, with α E , 31 in magnitude around twice of α E , 33 , are comparable to those in lead-based composites. The effect of the volume fraction and interface parameter on the ME coupling is also discussed. [ABSTRACT FROM AUTHOR]

Nonlinear magneto-electric response characteristics of giant magnetostrictive-piezoelectric composite sensors in harmonic and stochastic magnetic fields are studied in this paper. Van der Pol nonlinear differential items are introduced to explain the hysteresis phenomena of both giant magnetostrictive material and piezoelectric ceramics. The nonlinear dynamic model of giant magnetostrictive-piezoelectric composite sensors in harmonic and stochastic magnetic fields is developed. The expression of dynamic response of the system is obtained, and the bifurcation characteristics of the system are analyzed. The results of this paper are helpful for optimal design and improvement of giant magnetostrictive-piezoelectric composite sensors. [ABSTRACT FROM PUBLISHER]

CoFe2O4 (core)/BiFeO3 (shell) nanoparticles are prepared by varying the relative molar concentration of core and shell materials (40%CoFe2O4-60%BiFeO3, 50%CoFe2O4-50%BiFeO3, and 60%CoFe2O4-40%BiFeO3). The core-shell nature is confirmed from transmission electron microscopy on these samples. A plot of ΔM (=MFC-MZFC) vs temperature suggests the presence of two types of spin dynamics: (a) particle size dependent spin blocking and (b) spin-disorder. These two spin dynamic processes are found to contribute independently to the generation of magnetoelectric voltage. Very clear first order and second order magnetoelectric voltages are recorded. The resemblance of the first order magnetoelectric coefficient vs temperature plot to that of building up of order parameters in the mean field theory suggests that spin disorder can act like one of the essential ingredients in building the magnetoelectric coupling. The best result is obtained for the 50-50 composition sample, which may be due to better coupling of magnetostrictive CoFe2O4, and piezoelectric BiFeO3, because of the optimum thickness of shell and core. [ABSTRACT FROM AUTHOR]

The theoretical and experimental investigation of the direct magnetoelectric effect in the ring-type structures made of the bulk magnetostrictive-piezoelectric composites has been presented. The analytical expression for the magnetoelectric voltage coefficient has been obtained using the effective parameters method. The frequency dependence of this parameter is also analyzed. The dependence of the resonant frequency and the amplitude of this effect of the geometrical parameters of the ring for the first and second oscillation modes are presented. The experimental investigation of the direct magnetoelectric effect for the ring-type composite specimens consisting of the nickel ferrite spinel-PZT bulk composite is done. The obtained experimental data are in good agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]

In this paper, large zero-biased magnetoelectric (ME) effects are experimentally demonstrated in a five-phase laminate composite consisting of high-permeability Fe-based soft magnetic alloy FeCoV, giant magnetostrictive material Terfenol-D, and piezoelectric ceramic Pb(Zr1−x, Tix)O3 (PZT). The coupling effects between FeCoV and Terfenol-D result in a build-in magnetic bias due to their different magnetic permeability and coercivity. As a result, an obvious increase in resonant ME voltage coefficient (MEVC) at zero dc magnetic bias field ( H\text {dc}) for FeCoV/Terfenol-D/PZT/Terfenol-D/FeCoV (FMPMF) composite is obtained. The experimental results demonstrate that the optimum zero-biased resonant MEVC ( \alpha \text {ME,r}) of FMPMF composites with three-layer FeCoV foils can reach 19.6 V/cm Oe, which is 1.75 times as great as that of traditional Terfenol-D/PZT/Terfenol-D (MPM) laminate composites. A low-frequency MEVC ( \alpha \text {ME,l}) of 176 mV/cm Oe is achieved, which is 2.45 times higher than that of the MPM laminate composites. The induced zero-biased ME voltage of FMPMF laminate composite shows an excellent linear relationship to ac magnetic field both at the low frequency (1 kHz) and the resonance frequency (115.14 kHz) over a wide range. This laminate composite shows promising applications for high-sensitivity and small-size magnetic-sensing devices without bias. [ABSTRACT FROM AUTHOR]

A broadband current-sensing device with frequency-conversion mechanism consisting of Terfenol- D/Pb(Zr.Ti)O3 (PZT)/Terfenol-D magnetoelectric laminate and Fe73.5Cu1Nb3Si13.5B9 nanocrystalline flux concentrator is fabricated and characterized. For the purpose of acquiring resonance-enhanced sensitivity within broad bandwidth, a frequency-modulation mechanism is introduced into the presented device through the nonlinearity of field-dependence giant magnetostrictive materials. The presented configuration provides a solution to monitor the weak currents and achieves resonanceenhanced sensitivity of 178.4 mV/A at power-line frequency, which exhibits ~3.86 times higher than that of direct output at power-line frequency of 50 Hz. Experimental results demonstrate that a weak step-change input current of 1 mA can be clearly distinguished by the output amplitude or phase. This miniature current-sensing device provides a promising application in power-line weak current measurement. [ABSTRACT FROM AUTHOR]

The magnetoelectric effect in a three-phase particulate magnetoelectric composite is experimentally studied with specific interest in the dependence on the inducing magnetic field up to 300 Oe. A particulate magnetoelectric composite consisting 30 vol% of PVDF, 63 vol% of PZT and 7 vol% of Terfenol-D is fabricated in lab followed by the inducing magnetic field along the diameter direction in the process of hot pressing. It is observed that the change of inducing magnetic field influences the value of the magnetoelectric coefficient. This is partly attributed to the oriented domain walls promote the increase of the magnetostrictive coefficient of Terfenol-D, and partly attributed to the contraction deformation of Terfenol-D which causes the decrease of the coupling coefficient between PZT, TD and PVDF, which together influence the change of the magnetoelectric coefficient. In addition to the inducing magnetic field, the influence of the bias magnetic field in the process of testing to the magnetoelectric coefficient is examined at different fixed resonance frequency. A maximum of magnetoelectric coefficient 82.58 mV/(cm Oe) is obtained when the inducing magnetic field H i = 200 Oe and the bias magnetic field H dc = 1000 Oe. When H i < 200 Oe, the increase of the magnetostrictive coefficient of Terfenol-D plays a leading role which leads to increasing magnetoelectric response. In the H i range of 200 Oe < H i < 300 Oe, the decrease of the coupling coefficient between PZT, TD and PVDF plays a leading role and the magnetoelectric coefficient drops along the increase of the inducing magnetic field. [ABSTRACT FROM AUTHOR]

By considering the jump effect of magnetostrictive materials, a novel structure of PZT-ring/TDF-strip magnetoelectric composite is proposed to achieve magnetically tunable electromechanical resonance with a DC bias magnetic field. With the jump effect induced piezomagnetic coefficient of the Tb 0.3 Dy 0.7 Fe 1.92 strip, the resonance properties of the Pb(Zr,Ti)O 3 ring are theoretically studied and experimentally measured. The highly consistent results prove that the proposed composite has two resonant frequencies with improved sensitivity (133 Hz/Oe) and enhanced resolution (722 ppm/Oe) of resonance shift, which provide the feasibility of magnetically tunable electromechanical resonance with a low magnetic field and suggest the application potential for controllable sonar transducer. [ABSTRACT FROM AUTHOR]

A novel nonlinear theoretical model including eddy-current effect and demagnetization effect is presented for predicting magnetoelectric (ME) response in self-biased magnetostrictive/piezoelectric composites with the magnetization-graded ferromagnetic materials. The model is developed based on the nonlinear constitutive relationships of magnetostrictive material, motion equation for the composite plate, and ME equivalent circuit method. In this theoretical model, the equivalent magnetic charge theory is used for analyzing the influence of magnetostrictive material FeCuNbSiB on the effective magnetic field inside the Terfenol-D and the non-zero piezomagnetic coefficient at zero bias, in which the interface coupling parameter £ and the magnetic field dependence of mechanical quality factor are taken into consideration. The theoretical results indicate that the variation of ME voltage coefficients with applied dc magnetic field are in good agreement with the experimental results both under low and resonant frequency conditions. It confirms the validity and reliability of the obtained nonlinear theoretical model. Furthermore, self-biased effect and the difference between the low frequency and resonant ME voltage coefficient with H dc are discussed in details. The theoretical model plays an important role in the comprehensive understandings of dynamic ME response properties for self-biased laminate composites and the designing and fabricating ME devices. [ABSTRACT FROM AUTHOR]

Giant self-biased converse magnetoelectric (CME) effects with obvious hysteretic behaviors are systematically investigated in two-phase SmFe2/PZT [Pb(Zr1-x, Tix)O3] multiferroic laminates at room temperature. Taking advantage of the huge anisotropic field of SmFe2 plate, large remnant CME coupling is provoked by this field instead of permanent magnets to bias the laminate. Consequently, bitable magnetization status switching is realized through a smaller ac voltage far below the electric coercive field in the absence of magnetic bias field. Experiments demonstrate that a large remnant CME coefficient (αCME) of 0.007 mG/V is achieved, exhibiting ~50 times higher CME coefficient than the previous laminate composite multi-phase magnetostrictive plates. These results provide promising applications for realization of high-density magnetoelectric random access memories (MERAMs) devices with lower energy consumption. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) effect in multiferroic or ferroelectric/ferromagnetic composite thin films occurs through the elastic coupling between the piezoelectric properties of ferroelectric and magnetostrictive properties of ferromagnetic component. To obtain high elastic coupling and ME effect, we introduced PZT [Pb(Zr0.52, Ti0.48)O3] as a ferroelectric materials and CuFO (CuFe2O4) as ferromagnetic materials because of their high piezoelectric coefficient and magnetostrictive properties among various metal-oxide materials. To evaluate ME effect, we prepared CuFO/Pt/PZT/Pt hybrid thin films directly on Pt/TiO2/SiO2/Si substrate by using ion beam sputtering and spin-coating method. We investigated the microstructures and morphologies of hybrid thin films by XRD and SEM, the ferroelectric and ferromagnetic behaviors of hybrid films were examined by measuring polarization and magnetization hysteresis loops vs. electric and magnetic field. Magnetoelectric coefficients were calculated by measured magnetoelectric voltages using magnetoelectric measurement system. In this research, we’ll discuss the relations between annealing temperatures and multiferroic properties. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically and experimentally confirmed the uniformity of magnetoelectric (ME) coupling coefficients for the direct and converse ME (DME and CME) effects in longitudinal-transverse (L-T) mode magnetostrictive-piezoelectric two-phase composites, both at low frequencies and in the electromechanical resonance region. We also discussed the flaws in previous measurements of the ME coupling coefficients, which led to misunderstandings in the uniformity between the DME and CME effects. Our current work provided a correct method to correctly understand ME coupling in magnetostrictive-piezoelectric two-phase composites. [ABSTRACT FROM AUTHOR]

Highlights: [•] The magnetostrictive and piezoelectric phases are coupled through shear stress in strip–ring composite structure. [•] Size effects of magnetically tuned electromechanical resonances. [•] The influence of single magnetic field on resonant frequencies shift in magnetoelectric composites. [Copyright &y& Elsevier]

Direct and converse magnetoelectric effects are two opposite processes, which were integrated in a model based on equivalent circuit. Following the piezoelectric and magnetostrictive constitutive equations, we obtained magnetic-mechanical-electric equations, and then built a symmetric equivalent circuit about the magnetoelectric coupling. We equivalently analyzed the direct and converse magnetoelectric effects with this equivalent circuit. The numerical calculations fit the reported results very well, including the magnetoelectric changes with the thickness ratio and frequency, the relative lower converse magnetoelectric resonance frequency, and the phase increase of π around the direct and converse magnetoelectric resonance frequencies. This model helps us understand the magnetoelectric properties deeply, especially for the converse magnetoelectric effect. [ABSTRACT FROM AUTHOR]

Phase field modeling and simulation reveal that the magnetoelectric response of particulate magnetostrictive-piezoelectric composites sensitively depends on the magnetic domain structures of magnetostrictive phase. It is found that the longitudinal and transverse magnetoelectric coefficients of particulate composites with isotropic two-phase microstructures can be effectively tailored by controlling the magnetic domain structures. It is shown that engineered magnetic domains via controlled internal residual stress through appropriate processing, such as co-sintering under external stress (rather than isostatic pressing) in analogy to stress annealing of magnetostrictive materials, provide a powerful means to optimize magnetoelectric responses of particulate composites without fabricating anisotropic two-phase microstructures (e.g., laminate, fiber/rod). [ABSTRACT FROM AUTHOR]

Finite element method (FEM) simulations are performed to investigate the sensitivity to dc magnetic fields of magnetoelectric sensors on cantilever substrates with trenches or weights at different positions. For a simple layered cantilever, a 15% higher signal voltage across the piezoelectric layer is obtained for optimally positioned electrodes and an insulating magnetostrictive material. A further 25% increase in the signal voltage is achieved for a trenched cantilever design with a pick-up region. [ABSTRACT FROM AUTHOR]

We have studied a magnetoelectric (ME) effect that is nonlinear with respect to the alternating magnetic field. It is established that resonance excitation of an alternating electric field takes place in magnetostrictive-piezoelectric bilayer structures under the action of alternating magnetic field at a frequency that is half as small as the electromechanical resonance frequency. The nonlinear ME effect, in contrast to the linear one, does not depend on the constant (magnetizing) bias field and is quadratic with respect to the alternating magnetic field. [ABSTRACT FROM AUTHOR]

A polymer-based magnetoelectric 2-2 composite was fabricated in a thin film approach by direct spin coating of polyvinylidenefluoride-co-trifluoroethylene onto a Metglas substrate without the usage of an adhesive for the mechanical coupling between the piezoelectric and magnetostrictive materials. For a prototype single-sided clamped cantilever, a magnetoelectric coefficient as high as 850Vcm-1 Oe-1 is observed at its fundamental bending mode resonance frequency at 27.8 Hz and a detection limit of 10 pTHz-1/2 at its second bending mode resonance frequency at 169.5 Hz. [ABSTRACT FROM AUTHOR]

Abstract: Magnetoelectric effect in multiferroic materials is widely studied for its fundamental interest and practical applications. The magnetoelectric effect observed for single phase multiferroics is usually small. A much larger effect can be obtained in composites consisting of magnetostrictive and ferroelectric phases. This paper investigates the magnetoelectric effect of multilayer (laminated) structure consisting of 7 nickel ferrite and 8 PFN relaxor layers. It describes the synthesis and tape casting process for Ni0.3Zn0.62Cu0.08Fe2O4 ferrite and relaxor PbFe0.5Nb0.5O3 (PFN). Magnetic susceptibility, hysteresis, ZFC–FC curves and dependencies of magnetization versus temperature for PFN relaxor and magnetoelectric composite were measured with a vibrating sample magnetometer (VSM) in an applied magnetic field up to 85kOe at a temperature range of 10–400K. Parallel and perpendicular magnetostriction of the pure ferrite and bulk and laminated composites were measured at room temperature as a function of the magnetic field (0.3–6.5kOe). Magnetoelectric effect at room temperature was investigated as a function of the static magnetic field (0.3–6.5kOe) and the frequency of the sinusoidal magnetic field (0.01–6.5kHz). At lower magnetic field, the magnetoelectric coefficient increases slightly before reaching a maximum and then decreases. The magnetoelectric coefficient α ME increases continuously as the frequency is raised, although this increase is less pronounced in the 1–6.5kHz range. The maximum values of magnetoelectric coefficient attained for the layered composites exceed about 50mV/(Oecm). [Copyright &y& Elsevier]

A theory of the magnetoelectric effect in a bilayer magnetostrictive-piezoelectric structure is presented. As objects of research, structures in the form of nickel-lead zirconate-titanate and permendur-lead zirconate-titanate based plates are chosen. Joint solution of the motion equation for a magnetostrictive and piezoelectric medium and of the constitutive equations yields an expression for the magnetoelectric voltage coefficient in the region of electromechanical resonance. [ABSTRACT FROM AUTHOR]

This paper investigates the suitability of two-dimensional (2D) finite-element method (FEM) simulations to model the quasi-static bending-mode response of cantilever magnetoelectric (ME) sensors. We compute the deformation of the cantilever due to an applied magnetic field across the magnetostrictive (MS) layer as well as the generated voltage across the piezoelectric (PE) layer by solving a system of coupled linear elastostatic/elastodynamic and electrostatic/magnetostatic equations. In the 2D FEM formulation a plane-stress boundary condition is employed. Both 2D and 3D FEM results are compared for varying cantilever length and width. For cantilevers with \length\gg\height\gg\width good agreement is obtained between 2D and 3D results. For cantilevers obeying the condition \length\gg\width\gg\height, a systematic deviation occurs between 2D and 3D results as the plane-stress condition does not model the situation in the center of the cantilever. For a length:width:height ratio of 25:5:1, a difference in generated voltage of \sim12% is obtained for the Terfenol-D–PZT–Si material system. Especially for cantilevers with high aspect ratios, we show that 2D FEM simulations are sufficient to investigate the ME properties. [ABSTRACT FROM AUTHOR]

Abstract: Magneto-electric (ME) characteristics of the ferromagnetic/ferroelectric Fe70Pd30/PZT/Fe70Pd30 thin composites were investigated. The ME composites composed of the ferroelectric PZT phase (center layer, t: 260μm) and the ferromagnetic, magnetostrictive Fe70Pd30 phase (t: 30–90μm) glued on both the surfaces of PZT were fabricated. The rapidly solidified Fe70Pd30 ribbon mainly consists of fct martensitic phase with a large magnetostriction and fcc austenite (parent) phase. According to the DC bias magnetic field dependency of the output ME voltage ( V ME) at an AC magnetic field of 1.0Oe with an operation frequency of 1kHz for the composites, the increasing in thickness of magnetostrictive layers showed remarkable improvement of V ME values. For the composite with 90μm Fe–Pd layers, maximum V ME value of 13.9mV was obtained at 60Oe of the DC field, which is about two times higher than that of the composite with 30μm Fe–Pd layers. Additionally the V ME value of the serial circuit was monotonically enhanced by the serial circuit connection, and the composites exhibited a very large peak at a resonant frequency of 61–68kHz. [Copyright &y& Elsevier]

Highly sensitive AC magnetic field sensors are presented using magnetoelectric composites consisting of magnetostrictive and piezoelectric phases. They are offering passive nature, high sensitivity, large effect enhancement at mechanical resonance, and large linear dynamic range. Thin-film magnetoelectric 2-2 composites benefit from perfect coupling between the piezoelectric and magnetostrictive phases and from the reduction in size which is essential for high spatial resolution. Their design uses AlN and a plate capacitor or PZT with interdigital electrodes and magnetostrictive amorphous FeCoSiB single layers or exchanged biased multilayers. At mechanical resonance and depending on the geometry, extremely high ME coefficients of up to 9.7 kV/cm Oe in air and up to 19 kV/cm Oe under vacuum were obtained. To avoid external DC magnetic bias fields, composites consisting of exchanged biased multilayers serving as the magnetostrictive component with a maximum magnetoelectric coefficient at zero magnetic bias field are employed. Furthermore, the anisotropic response of these exchanged biased composites can be utilized for three-dimensional vector field sensing. Sensitivity and noise of the sensors revealed limits of detection as good as to 2.3 pT/Hz1/2 at mechanical resonance. Sensitivity between 0.1 and 1000 Hz outside resonance can be enhanced through frequency conversion using AC magnetic bias fields. [ABSTRACT FROM AUTHOR]

The non-linear magnetoelectric (ME) effect of Metglas/Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructures has been studied. Such effect holds promise for modulation mode ME sensor applications that require no dc bias. The non-linear ME coefficient was found to be highly dependent on the derivative of the piezomagnetic strain coefficient, which could be increased by increasing the Metglas length due to magnetic flux concentration. The non-linear ME coefficient was equal to 9.5 V/(cm-Oe2) at Hdc = -1 Oe and 7.5 V/(cm-Oe2) at Hdc = 0 Oe for a structure with 10 cm long Metglas foils. [ABSTRACT FROM AUTHOR]