Maximum Magnetoelectric Research Articles

Enhancement of the magnetoelectric coupling in an A-line shape magnetostrictive/piezoelectric structure

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 αE 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.

Induced Magnetoelectric Effect Driven by Magnetization in BaFe<sub>12</sub>O<sub>19</sub>- P(VDF-TrFE) Composites

Films of BaFe12O19/poly(vinylidenefluoride)-trifluorethylene composites with 5, 10, and 20 wt% barium ferrite content have been fabricated. BaFe12O19 microparticles have the shape of thin hexagonal platelets, the easy direction of magnetization remaining along the c-axis, which is perpendicular to the plates. This fact allows for ferrite particles orientation in-plane and out-of-plane within the composite films, as confirmed by measured hysteresis loops. While the in-plane-induced magnetoelectric (ME) effect is practically zero, these composite films show a good out-of-plane ME with maximum ME coupling coefficient changes of 3, 17, and 2 mV/cm.Oe for the 5, 10, and 20 wt% barium ferrite content films, respectively. We conclude that this ME behavior appears to be driven by the magnetization process arising when we applied the external magnetic field. We have also measured the linear and reversible ME effect for low applied bias field, when magnetization process is still reversible.

Structural evolution and physical properties of multiferroic Bi0.9−xLa0.1PbxFeO3−x/2 ceramics

The polycrystalline samples of multiferroic Bi0.9−xLa0.1PbxFeO3−x/2 (x = 0–0.35) were prepared by the solid state reaction method and characterized by x-ray diffraction, field emission scanning electron microscopy, dielectric, magnetic, magnetodielectric (MD) and magnetoelectric (ME) measurements. A structural evolution from rhombohedral to pseudocubic structure was found to happen near x = 0.20. The changes and anomalies observed in magnetization were correlated with structural evolution and the development in microstructure. The ferroelectromagnetic measurements demonstrated Pb2+ doping to be a very effective method to realize the coexistence of weak ferromagnetism and ferroelectric in the ferroelectric R3c phase of BiFeO3. The MD and ME effects of Bi0.9−xLa0.1PbxFeO3−x/2 ceramics were first reported. A maximum ME voltage coefficient has been observed at x = 0.30. This work is helpful for understanding the ferroelectromagnetic behaviors and ME effect with complicated spin structures.

Synthesis and magnetoelectric effect of composites with CoFe2O4-epoxy embedded in 3–1 type porous PZT ceramics

Three-phase magnetoelectric (ME) composites of lead zirconate titanate (PZT)/cobalt ferrite CoFe2O4 (CFO)/epoxy were synthesized in sequence by a tert-butyl alcohol (TBA)-based freeze-casting technique, a chemical solution deposition method, and an impregnation process. The novel pseudo 3–0–1 type composite structure with a high content of CFO was examined using SEM and XRD. The composites showed not only stable and excellent dielectric behavior in a wide frequency range, but also good ferroelectricity and ferromagneticity at the same time, as can be seen from the typical electrical and magnetic hysteresis loops. The ME effect of the resultant 3–0–1 type ferroelectric/ferromagnet/polymer composites was found to be significantly dependent on the content of PZT and CFO. The maximum ME coefficient of 2.2mV/cmOe was observed when the PZT volume fraction is 0.5 and CFO mass fraction is 0.2. This synthesis route we proposed provides a new connectivity type of ME composite and shows potential applications in sensors and transducers.

Giant 2-D Magnetoelectric Effects in a Unique Magnetostrictive/Piezoelectric Heterostructure Without Interface Bonding

We develop a unique magnetoelectric (ME) heterostructure with giant 2-D ME effects by attaching magnetostrictive Metglas at the free end of a piezoelectric Pb(Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> )O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (PZT) cantilever, instead of interface bonding. The ME effects originate from flexural deformation of PZT plate driven by a mechanical force from Metglas. In experiments, the 1-D ME heterostructures induced different directional magnetic fields have been designed optimally. When the length of Metglas ribbon is 12 mm, the 1-D ME heterostructures have the maximum ME effects. After assembling the different optimal designed 1-D ME heterostructures, an ME heterostructure with 2-D ME characteristics is obtained. The 2-D heterostructure has two resonant frequencies, at about 88 and 115 kHz. The maximum resonant voltage coefficient (α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ME,r</sub> ) is 79 (V/cm Oe) when the heterostructure is in one direction of the magnetic field, and 45 (V/cm Oe) when the heterostructure is in the other direction of the magnetic field. The results demonstrate that this ME structure can be used as a multidimensional ME transducer.

Large Magnetoelectric Effect in FeCuNbSiB/FeGa/PZT Multilayer Composite at Low Optimum Bias

We report a large magnetoelectric (ME) effect in FeCuNbSiB/FeGa/PZT multilayer composite at low optimum bias magnetic field (Hdc). Due to the great differences in the magnetic permeability and coercivity between FeCuNbSiB foils and FeGa alloys, the strong magnetization gradients are achieved, which induce an additional internal magnetic field in FeGa alloys. As a result, the optimum Hdc of FeGa/PZT composite decreases dramatically by attaching multilayer FeCuNbSiB foils. The experimental results demonstrate that: 1) the optimum Hdc of FeCuNbSiB/FeGa/PZT composite with one layer FeCuNbSiB foil reaches 62 Oe, which is only one-tenth of that of FeGa/PZT composite (606Oe); 2) the maximum ME voltage coefficient (MEVC) at resonance (α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ME,r</sub> ) of FeCuNbSiB/FeGa/PZT composite with four-layer FeCuNbSiB foils can reach 115.8V/cm Oe, which is ~2.3 times higher than that of FeGa/PZT composite; and 3) the maximum zero-biased MEVC at resonance (α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ME,zero</sub> ) is up to 58.2 V/cm Oe for FeCuNbSiB/FeGa/PZT composite with four-layer FeCuNbSiB foils. It provides great opportunities for such potential applications as the small-size and high-performance magnetic field sensors.

Size effects on the magnetoelectric response on PVDF/Vitrovac 4040 laminate composites

Tri-layered and bi-layered magnetoelectric (ME) flexible composite structures of varying geometries and sizes consisting on magnetostrictive Vitrovac and piezoelectric poly(vinylidene fluoride) (PVDF) layers were fabricated by direct bonding. From the ME measurements it was determined that tri-layered composites structures (magnetostrictive–piezoelectric–magnetostrictive type), show a higher ME response (75 V cm−1 Oe−1) than the bi-layer structure (66 V cm−1 Oe−1). The ME voltage coefficient decreased with increasing longitudinal size aspect ratio between PVDF and Vitrovac layers (from 1.1 to 4.3), being observed a maximum ME voltage coefficient of 66 V cm−1 Oe−1. It was also observed that the composite with the lowest transversal aspect ratio between PVDF and Vitrovac layers resulted in better ME performance than the structures with higher transversal size aspect ratios. It was further determined an intimate relation between the AreaPVDF/AreaVitrovac ratio and the ME response of the composites. When such ratio values approach 1, the ME response is the largest. In addition the ME output value and magnetic field response were controlled by changing the number of Vitrovac layers, which allows the development of magnetic sensors and energy harvesting devices.

Magnetoelectric coupling characteristics of five-phase laminate composite transducers based on nanocrystalline soft magnetic alloy

A five-phase laminate composite transducer based on nanocrystalline soft magnetic FeCuNbSiB alloy is presented, whose magnetoelectric (ME) coupling characteristics have been investigated. It is found that the resonant ME voltage coefficient of FeCuNbSiB/Terfenol-D/Pb(Zr1-x,Tix)O3 (PZT)/Terfenol-D/FeCuNbSiB (FMPMF) five-phase transducer is much larger than that of traditional Terfenol-D/PZT/Terfenol-D (MPM) transducer, resulting from the enhancement of the effective mechanical quality factor and effective piezomagnetic coefficient of the transducers. Appropriate FeCuNbSiB layer thickness is propitious to the resonant and low-frequency ME coupling characteristics. The maximum resonant ME voltage coefficient achieves 4.81 V/Oe with FeCuNbSiB layer thickness is 60 μm under the DC bias magnetic field Hb = 77 Oe, which is 1.48 times as great as that of traditional MPM transducer. In addition, the maximum ME voltage coefficient at low frequency is 51.2 mV/Oe under the DC bias magnetic field Hb = 442 Oe, which is 1.26 times as great as that of traditional MPM transducer. It indicates that the mentioned five-phase laminate composite transducers have great potential for the application of highly sensitive dc magnetic field sensing and vibration energy harvesting.

Fabrication and characterization of shape anisotropy AlN/FeCoSiB magnetoelectric composite films

The shape anisotropy magnetoelectric (ME) composite films composed of piezoelectric AlN film and magnetostrictive FeCoSiB strips film were fabricated successfully by means of hard-mask during sputter deposition. The results demonstrated that the ME anisotropy factor K was strongly dependent on the number of FeCoSiB strips. If the number of strips is not more than eight, the ME anisotropy factor K increases slowly with increasing the strips' number. In addition, ME anisotropy factor K increases sharply when the number is more than eight. Furthermore, as the number of FeCoSiB strips increases to ten, the maximum ME anisotropy factor K reaches up to a value of 135, close to the theoretical value 175. However, by calculation, the ME anisotropy factor K will reach up to 11,357 if the FeCoSiB strips are prepared to possess the value of 1μm in width by high precision photo-etching technology. In that case, the noise signal will be reduced to 5nT. The shape anisotropy AlN/FeCoSiB ME composite films prepared in this work show great potential application in magnetic field detection in view of good ME anisotropy property.

Magnetoelectric Bi3.25Nd0.75Ti3O12–La0.6Ca0.4MnO3 composite thin films derived by SOL–GEL method

Magnetoelectric (ME) Bi3.25Nd0.75Ti3O12–La0.6Ca0.4MnO3 (BNT–LCMO) composite thin films were deposited on Pt/Ti/SiO2/Si(100) substrates by a simple SOL–GEL method and spin-coating process with two different deposition sequences: BNT/LCMO/Pt/Ti/SiO2/Si(BLP) and LCMO/BNT/Pt/Ti/SiO2/Si(LBP). Our results show the composite thin films exhibit both good ferroelectric and magnetic properties, as well as a ME effect. BLP thin films have larger maximum ME voltage coefficient values than LBP structured thin films. The deposition sequence has a notable effect on the ferroelectric and magnetic properties and ME coupling behavior of the bi-layer thin films.

Raman spectra, photoluminescence, magnetism and magnetoelectric coupling in pure and Fe doped BaTiO3 nanostructures

Abstract Structural, microstructural, Raman spectroscopy, photoluminescence, saturation magnetization and magnetoelectric (ME) measurement of BaTiO3 (BFT0) and BaFe0.01Ti0.99O3 (BFT1) nanostructures have been studied. BFT0 and BFT1 were prepared by a hydrothermal method of processing temperature 180 °C/48 h. The X-ray diffraction pattern shows the coexistence of cubic/tetragonal and hexagonal phases for BFT0 and cubic/tetragonal for BFT1. The Raman spectra confirm the coexistence of tetragonal and hexagonal phases in BFT0 and cubic in BFT1. Transmission electron microscopy images show nanorods of hexagonal shaped faces for BFT0 and cubic shaped nanowires for BFT1. The resulting mechanism of the formation of these nanostructures is discussed. The experimental and theoretical results by photoluminescence are related to the degree of disorder existing in both BFT0 and BFT1 and suggest the presence of localized states existing inside of the band gap which are directly affected for degree of order–disorder. A strong ferromagnetism in BFT1 and diamagnetism in BFT0 is observed by magnetic hysteresis. As BFT1 is ferromagnetic, the value of linear coefficient, α called Magnetoelectric (ME) coefficient is calculated as ∼16 mV/Oe cm at a fixed frequency of 850 Hz. This ME coefficient α corresponds to induction of polarization by a magnetic field or of magnetization by an electric field. The observed optimum dc bias field at which the maximum ME coupling occurs is ∼750 Oe.

Magnetoelectricity in coated fibrous composites of piezoelectric and piezomagnetic phases

This paper studies the effective magnetoelectric (ME) behavior of coated fibrous composites made of piezoelectric and piezomagnetic phases. We employ a micromechancial model, the two-level recursive scheme together with the Mori–Tanaka method, to evaluate the ME effect of the composites. The magnitudes and trends of the solutions are in good agreement with the calculations by the finite element analysis. Based on this model, we find the optimal volume fractions of the inclusion, the ratio of the radii between the core and shell for maximum ME coupling. Further, we correlate the ME effect with the material parameters of the constituent phases and propose useful engineering guide to the development of new ME coated fibrous composites.

Enhanced magnetoelectric coupling in Pb(Zr0.52Ti0.48)O3 film-on-CoFe2O4 bulk ceramic composite with LaNiO3 bottom electrode

By chemically depositing a conductive LaNiO3 (LNO) electrode layer onto dense CoFe2O4 (CFO) ceramics, the magnetoelectric (ME) response in Pb(Zr0.52Ti0.48)O3 (PZT)/CFO film-on-substrate system was significantly enhanced. Structural, morphological, ferroelectric, and piezoelectric analysis was performed for the present PZT/LNO/CFO film-electrode-substrate composites, whereby improved electric-related output was demonstrated. It was further shown that the maximum ME coefficient αE31 could reach up to 155 mV/cm Oe, which was about 2.6 times higher than that in PZT film-on-CFO ceramics without bottom electrode layer. Further enhancement of ME response could be expected by preparing high-quality electrode layer with optimal thickness and improved fabrication processing for such film-electrode-substrate composites.

Microscale 1–3-type lead-free piezoelectric/ferrite composites fabricated by a modified dice-and-fill method

This paper introduces a facile method to fabricate magnetoelectric (ME) composites with microscale lead-free piezoceramic pillars embedded in a ferrite matrix without high-temperature co-sintering. The microscale piezoceramic pillars with a sectional width of about 150 µm were obtained from lead-free piezoceramic discs by a dicing method. The spacing between the pillars was backfilled with cobalt ferrite (CFO) nanoparticles, and then a liquid epoxy was infiltrated into the backfilled spacing to bond the filled particles and the pillars. The ME property of the resultant 1–3-type piezoelectric/ferrite composites was verified and found to be significantly dependent on the filling density of the CFO powder, which could be adjusted by repeating the filling step. A maximum ME voltage response of up to 302 µV Oe−1 was obtained in a 700 µm high composite with pillars of 150 µm width and 200 µm spacing. The present method provides a potential way to fabricate finescale multiferroic composites for microdevice applications.

Theoretical model for geometry-dependent magnetoelectric effect in magnetostrictive/piezoelectric composites

A quasistatic theoretical model including geometry effect is presented for predicting the magnetoelectric (ME) coefficients in a ME multilayer composite consisting of magnetostrictive and piezoelectric layers. The model is developed based on average-field method considering the geometry effect. The model characterizes the ME coefficient in terms of not only the parameters of two composite components and the thickness fraction but also the length and width fractions for the piezoelectric or magnetostrictive components. Analytical predictions indicate that the width and length fractions strongly influence the maximum ME coefficient and the corresponding thickness fraction also. Clearly, geometry effects cannot be ignored in predicting ME coefficient. Theoretical ME coefficients are also compared to experimental test data, demonstrating excellent agreement.

Giant magnetoelectric coupling in laminate thin film structure grown on magnetostrictive substrate

Highly dense 1 μm-thick piezoelectric film was deposited on magnetostrictive substrate [platinized nickel-zinc ferrite (NZF)]. A strong magnetic coupling between the piezoelectric film and magnetostrictive NZF substrate was measured exhibiting the maximum magnetoelectric (ME) coefficient on the order of 140 mV/cm Oe at the conditions of HDC = 50 Oe and HAC = 1 Oe at f = 1 kHz. This giant ME coupling under low DC magnetic field condition is attributed to effective elastic coupling. A rotation-type dynamic strain distribution was observed on the PZT film surface which provides information about the nature of elastic coupling.

Preparation and magnetoelectric properties of NiFe2O4–PZT composites obtained in-situ by gel-combustion method

Magnetoelectric composites of xNiFe2O4–(1 − x)Pb(Zr,Ti)O3 with x = 2, 5, 10, 20, 30% were prepared by citrate–nitrate combustion using PZT-based template powders. In order to ensure a better connectivity of dissimilar phases, we have used chemical methods for preparation in situ composites, followed by adequate sintering procedure. The structural, microstructural and functional properties of di-phase magnetoelectric composites of NiFe2O4–PZT are reported. The XRD analysis is demonstrating the synthesis of pure ferrite phase directly on the ferroelectric templates. An excellent mixing was obtained in the composite powders, as proved by a detailed SEM analysis. The magnetic and dielectric behaviors of the ceramic composites vary with the ratio of the two phases. The dielectric behavior is greatly influenced by the magnetic phase. The magnetoelectric (ME) coefficient was measured as a function of applied DC magnetic field. The maximum ME coefficient (dE/dH) varies from 0.0011 mV/(cm Oe) to 0.5 mV/(cm Oe) with increasing of NF addition.

Magnetoelectric coupling in multiferroic heterostructure of rf-sputtered Ni–Mn–Ga thin film on PMN–PT

In this paper, we report a preparation of multiferroic heterostructure from thin film of Ni–Mn–Ga (NMG) alloy and lead magnesium niobate–lead titanate (PMN–PT) with effective magnetoelectric (ME) coupling between the film as ferromagnetic material and PMN–PT as piezoelectric material. The heterostructure was prepared by relatively low temperature (400°C) deposition of the film on single crystal of piezoelectric PMN–PT substrate using rf magnetron co-sputtering of Ni50Mn50 and Ni50Ga50 targets. Magnetic measurements by Superconducting Quantum Interference Design (SQIUD) Magnetometer and Vibrating Sample Magnetometer (VSM) on the film revealed that the film is in ferromagnetically ordered martensitic state at room temperature with saturation magnetization of ∼240emu/cm3 and Curie temperature of ∼337K. Piezoresponse force microscopy (PFM) measurement done at room temperature on the substrate showed the presence of expected hysteresis loop confirming the stability of the piezoelectric state of the substrate after deposition. Room temperature ME voltage coefficient (αME) of the heterostructure was measured as a function of applied bias dc magnetic field in Longitudinal–Transverse (L–T) ME coupling mode by lock-in technique. A maximum ME coefficient αME of 3.02mV/cmOe was measured for multiferroic NMG/PMN–PT heterostructure which demonstrates that there is ME coupling between the film as ferromagnetic material and PMN–PT as piezoelectric material.

Study of magnetic properties and magnetoelectric effect in (x) Ni0.5Zn0.5Fe2O4+(1−x)PZT composites

Magnetoelectric (ME) composites consisting of ferrite phase (x) Ni0.5Zn0.5Fe2O4+ferroelectric phase (1−x)Pb Zr0.8Ti0.2O3 (Lead Zirconate Titanate—PZT) in which x (mol%) varies between 0 and 1 (0.0≤x≤1.0) was synthesized by double sintering ceramic method. The presence of constituent phases of ferrite, ferroelectric and their composites was confirmed by X-ray diffraction studies. The hysteresis measurement was used to study magnetic properties such as saturation magnetization (MS) and magnetic moment (μB). The existence of single domain (SD) particle in the ferrite phase and mixed (SD+MD) particle in the composites was studied from AC susceptibility measurements. ME voltage coefficient for each mol% of ferrite phase was measured as a function of applied DC magnetic field and at the same time influence of magnetic field on ME response and resistivity of composites was studied. The maximum ME voltage coefficient of 0.84mV/cmOe was observed for 15% of ferrite phase and 85% of ferroelectric phase in the composites.

Magnetoelectricity of lateral 1-3 type composites with CoFe2O4 ferromagnetic microstrips embedded in (K,Na)NbO3-based piezoceramic substrate

Microscale 1-3-type-like magnetoelectric (ME) composites with ferromagnetic microstrips laterally embedded in a piezoelectric ceramic substrate were fabricated by a dice-and-insert method. Mechanically sliced microstrips of Li/Ta-modified (K,Na)NbO3 lead-free ceramics and CoFe2O4 ceramics were used as the piezoelectric and piezomagnetic phases, respectively, which were inserted into each other and bonded together by epoxy. The ME properties of such 1-3-type-like composites with piezoelectric substrates were verified. The maximum ME coefficient was found to vary with the strip size, substrate thickness, and thickness of epoxy bonding layers. A maximum value of 48 mV/(cm·Oe) was achieved. In addition, a special anisotropy was obtained in the present lateral 1-3 type ceramic composites and made it have potential applications in detecting magnetic field directions.