Converse Magnetoelectric Coefficient Research Articles

Modeling the Converse Magnetoelectric Effect in the Low-Frequency Range.

This article is devoted to the theory of the converse magnetoelectric (CME) effect for the longitudinal, bending, longitudinal-shear, and torsional resonance modes and its quasi-static regime. In contrast to the direct ME effect (DME), these issues have not been studied in sufficient detail in the literature. However, in a number of cases, in particular in the study of low-frequency ME antennas, the results obtained are of interest. Detailed calculations with examples were carried out for the longitudinal mode on the symmetric and asymmetric structures based on Metglas/PZT (LN); the bending mode was considered for the asymmetric free structure and structure with rigidly fixed left-end Metglas/PZT (LN); the longitudinal-shear and torsional modes were investigated for the symmetric and asymmetric free structures based on Metglas/GaAs. For the identification of the torsion mode, it was suggested to perform an experiment on the ME structure based on Metglas/bimorphic LN. All calculation results are presented in the form of graphs for the CME coefficients.

Analytical solutions for resonant radiation performance of bending-mode magnetoelectric antennas

This paper proposes analytical solutions for the resonant radiation performance of bending-mode magnetoelectric (ME) antennas. The strain-mediated Converse ME (CME) coupling model of bending-mode ME antennas is first established by solving nonlinear constitutive equations and bending governing equations using the elastic mechanics method. Then, the calculated magnetic flux and electric displacement are employed to propose a resonant radiation field model based on the dipole method. The numerical results for the CME coefficient show a good agreement with the experimental data. It can be observed that the volume fraction ratio of the piezoelectric layer can control the CME coefficient and radiation efficiency with the same variation trend since it can determine the bending strain via changing the location of the neutral layer of the ME antennas, which also demonstrates the strain-mediated essence of the ME antennas. In addition, the volume fraction ratio can tune the resonant frequency within a wide range. The gain of the ME antenna is stable and higher than −168 dB with the volume fraction ratio ranging from 0.2 to 0.7. The tensile stress and compressive stress have the opposite effect on the resonant frequency at low and high bias magnetic fields. Meanwhile, the tensile (compressive) stress is beneficial for both the radiation and gain in the low (high) bias field region. This model may facilitate the understanding of the bending-mode radiation mechanism of ME antennas and provide a basis for designing asymmetric ME antennas.

Magneto‐Mechano‐Electric Antenna for Portable VLF Transmission

AbstractWireless communication has always been an indispensable element in the modern information‐based society. Beyond the commercial electrical antenna, very low frequency (VLF) mechanical antennas have recently become research hotspot since their combination of miniaturization and favorable radiation efficiency in lossy electrically conductive environments. However, their usage is challenged due to the relatively limited radiation capability and modulation bandwidth. This study demonstrates an improved high‐efficiency magnetoelectric (ME) mechanical antenna based on the magneto‐mechano‐electric (MME) effect, realized via the synergistic effect of piezo‐driven magnets motion and converse magnetoelectricity (ME). Converse ME coefficient and radiation measurement show that the MME antenna demonstrates superior performance over a normal ME antenna. The oscillation magnet serves as an extra vibrating magnetic dipole besides the ME composite and thus brings radiation enhancement to the mechanical antenna. Furthermore, digital signal modulations are conducted with a VLF carrier signal to enable anti‐interference and anti‐attenuation communication. In view of the exemplary demonstration, the MME effect‐based antenna is expected to provide a new strategy for mechanical antenna improvement and shows tremendous potential for conductive environments communication applications.

Tuning the Performance of Acoustically Actuated Magnetoelectric Antenna via Magnetic and Mechanical Stimuli

Magnetoelectric (ME) antenna operates at the acoustic wave resonance rather than EM wave resonance, thus it shows significant superiority for developing compact antennas and antenna arrays. The simulation of ME antenna involves the nonlinear coupling of Electrostatics, Solid Mechanics, and Magnetic physics, making it difficult to model such devices. This paper proposes a fully multi-field coupled model for the ME antenna, in which the nonlinear magnetostrictive model is taken into account. The nonlinear magnetization is solved and then AC and DC simulations are performed by coupling different physics. The effects of magnetic bias and pre-stress on the converse magnetoelectric (CME) coupling and near-field radiation are discussed for the first time, to regulate the performance of the ME antenna with fixed dimensions. The results indicate that the magnetic bias and pre-stress can change the resonance frequency, CME coefficient, and near-field radiation of ME antenna. Particularly, it should be noted that pre-stress has the opposite effect in the low and high regions of the bias field. The near-field radiation is significantly enhanced by applying a proper magnetic bias or pre-stress. This simulation may facilitate the understanding of nonlinear CME behavior and provide a basis for designing nonlinear active and tunable ME antenna.

A two-dimensional multi-field coupling model for converse magnetoelectric effect in acoustically actuated antennas

The radiation performance of acoustically actuated magnetoelectric (ME) antennas is originated from converse magnetoelectric (CME) effect that converts the electric field to magnetic field due to strain coupling. This paper presents a two-dimensional model for the CME effect of ME antennas with considering a fully magneto-elastic coupled characteristic of magnetostrictive materials. The nonlinear magnetostrictive relation is equivalent to a linear-like form using the equivalent parameter method. The coupled effects of magnetic bias and pre-stress on the CME coupling are discussed. The prediction for the CME coefficient shows a good agreement with the experimental data. The results indicate that pre-stress and magnetic bias have a strong-coupled effect on the CME effect. In addition, optimal loading modes are obtained for improving the CME effect. The radiations of ME antennas have not yet been obtained. Nevertheless, the results in this work may provide a basis for further investigation on the radiations.

Increased Magnetoelectric Coupling in Porous Nanocomposites of CoFe2O4 and BiFeO3 with Residual Porosity for Switchable Magnetic Devices

In this work, multiferroic thin-film nanocomposites were synthesized by coating the inside of mesoporous, cobalt ferrite (CoFe2O4 or CFO) with varying thicknesses of piezoelectric bismuth ferrite (BiFeO3 or BFO) grown by atomic layer deposition (ALD). Since ALD allows for precise control of the BFO layer thickness, the amount of residual porosity inside the pores can be controlled. Upon electrical poling, the piezoelectric BFO strains to be under out-of-plane tension, and since BFO is covalently bound to CFO, this tensile stress is transferred from BFO to CFO. CFO is a negative magnetostrictive material, meaning its magnetization should decrease in the direction of tension. This decrease in magnetization was observed in out-of-plane magnetometry experiments. Interestingly, the magnetization changes were found to be largest in the samples with the most residual porosity, despite the fact that they contained the smallest volume of BFO. Indeed, while the fully filled samples had a similar magnetoelectric coefficient to other dense nanostructured BFO-CFO composites reported in the literature, composites with the most residual porosity showed an exceptionally large converse magnetoelectric coefficient of 1.2 × 10–6 s m–1, an order of magnitude higher than dense composites. Strain transfer was confirmed using high-resolution X-ray diffraction. Samples with more residual porosity showed larger strain changes, corroborating the magnetization data. This suggests that magnetoelectric coupling can be optimized by engineering residual porosity into multiferroic composites. Such systems have profound effects for a broad range of switchable magnetic devices, particularly in the microwave and spintronic space.

Display of converse and direct magnetoelectric effect in double perovskite LaYFe2O6

This work reports the simultaneous observation of converse magnetoelectric (CME) and direct magnetoelectric (DME) effects in LaYFe2O6. The structural, magnetic, and magnetoelectric properties of LaYFe2O6, prepared by the sol-gel auto-combustion method and sintered at various temperatures, have been studied. The x-ray powder diffraction study suggests the double perovskite structure with symmetries P21nm (∼90%) and Pbnm (∼10%). The alternate ordering of La and Y ions is confirmed by the neutron powder diffraction (ND) study, which also suggests the antiferromagnetic (AFM) ordering of spins. AFM behavior is also manifested by the magnetic field-dependent magnetization (M) measurement. A higher P21nm phase content is desirable in the context of magnetoelectricity. Magnetic transition (∼700 K) is asserted in the temperature-dependent M measurement. The isothermal magnetization study shows weak ferromagnetism probably due to gradually increasing spin canting with temperature until the transition temperature. The highest CME coefficient (∼2.26 mOe cm/V) as well as DME coefficient (∼0.45 mV/cm Oe) in this material are recorded. True magnetoelectricity for temperature as high as 400 K opens up a new avenue on the playground of magnetoelectric (ME)-based applications.

A very low frequency (VLF) antenna based on clamped bending-mode structure magnetoelectric laminates

As the development of wireless communication devices tends to be highly integrated, the miniaturization of very low frequency (VLF) antenna units has always been an unresolved issue. Here, a novel VLF mechanical communication antenna using magnetoelectric (ME) laminates with bending-mode structure is realized. ME laminates combines magnetostrictive Metglas amorphous ribbons and piezoelectric 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 single crystal plates. From the simulation, we confirmed that the ME laminates can reduce the resonance peak from 18 kHz to 7.5 kHz by bending-mode structure. Experiment results show the resonance frequency can be farther reduced to 6.3 kHz by clamping one end of the ME antenna. The ME laminate exhibits a giant converse ME coefficient of 6 Oe cm V−1 at 6.3 kHz. The magnetic flux density generated by the ME antenna has been tested along with distance ranging from 0 to 60 cm and it is estimated that a 1 fT flux could be detected around 100 m with an excitation power of 10 mW.

Direct evidence of mutual control of ferroelectric polarization and magnetization in Y-type hexaferrite BaSrCo2Fe12-Al O22 ceramics

Hexaferrites that exhibit the intrinsic and strong magnetoelectric (ME) coupling effect have been considered the most promising candidate for single-phase multiferroics. Currently, the strong ME coupling effect in this system was widely reported in single crystal form, while it is rare in polycrystalline one. In this work, Y-type hexaferrite BaSrCo2Fe12-xAlxO22 (x = 0.0, 0.3, 0.6 and 0.9) ceramics were manufactured with conventional solid-state reaction. Their magnetic, dielectric, and ME coupling properties were systematically surveyed. It was revealed that Al doping could result in a high magnetic transition temperature of ~ 345 K for x = 0.9. Also, the ferroelectric polarization and abnormal magnetodielectric properties were significantly enhanced which could be maintained down to 200 K. Most interestingly, the sample x = 0.9 displayed strong direct and converse ME coefficients of ~ 400 ps/m and ~ 900 ps/m at 150 K, respectively. Therefore, these results reveal that Al doping can broaden our understanding of the Y-type hexaferrite in room-temperature multiferroics.

Enhancing Converse Magnetoelectric Coupling Through Strain Engineering in Artificial Multiferroic Heterostructures.

Magnetoelectric materials present a unique opportunity for electric field-controlled magnetism. Even though strain-mediated multiferroic heterostructures have shown unprecedented increase in magnetoelectric coupling compared to single-phase materials, further improvements must be made before ultra-low power memory, logic, magnetic sensors, and wide spectrum antennas can be realized. This work presents how magnetoelectric coupling can be enhanced by simultaneously exploiting multiple strain engineering approaches in heterostructures composed of Fe0.5Co0.5/Ag multilayers on (011) Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 piezoelectric crystals. When grown and measured under strain, these heterostructures exhibit an effective converse magnetoelectric coefficient in the order of 10-5 s m-1: the highest directly measured, non-resonant value to-date. This response occurred at room temperature and at low electric fields (<2 kV cm-1). This large effect is enabled by magnetization reorientation caused by changing the magnetic anisotropy with strain from the substrate and the use of multilayered magnetic materials to minimize the internal stress from deposition. Additionally, the coercive field dependence of the magnetoelectric response under strain suggests contributions from domain-mediated magnetization switching modified by voltage-induced magnetoelastic anisotropy. This work highlights how multicomponent strain engineering enables enhanced magnetoelectric coupling in heterostructures and provides an approach to realize energy-efficient magnetoelectric applications.

Engineering new limits to magnetostriction through metastability in iron-gallium alloys

Magnetostrictive materials transduce magnetic and mechanical energies and when combined with piezoelectric elements, evoke magnetoelectric transduction for high-sensitivity magnetic field sensors and energy-efficient beyond-CMOS technologies. The dearth of ductile, rare-earth-free materials with high magnetostrictive coefficients motivates the discovery of superior materials. Fe1−xGax alloys are amongst the highest performing rare-earth-free magnetostrictive materials; however, magnetostriction becomes sharply suppressed beyond x = 19% due to the formation of a parasitic ordered intermetallic phase. Here, we harness epitaxy to extend the stability of the BCC Fe1−xGax alloy to gallium compositions as high as x = 30% and in so doing dramatically boost the magnetostriction by as much as 10x relative to the bulk and 2x larger than canonical rare-earth based magnetostrictors. A Fe1−xGax − [Pb(Mg1/3Nb2/3)O3]0.7−[PbTiO3]0.3 (PMN-PT) composite magnetoelectric shows robust 90° electrical switching of magnetic anisotropy and a converse magnetoelectric coefficient of 2.0 × 10−5 s m−1. When optimally scaled, this high coefficient implies stable switching at ~80 aJ per bit.

Large converse magnetoelectric effect in Sm doped Pb(Mg1/3Nb2/3)-PbTiO3 and NiFe2O4 laminate composite

The magnetoelectric bilayer composite Sm-doped Pb(Mg1/3Nb2/3)-PbTiO3/NiFe2O4 (Sm:PMN-PT/NFO) developed in this study exhibits a converse magnetoelectric coefficient (αCME) of 0.34 G cm/V at resonance. This value is at least an order of magnitude higher than any previously reported αCME for polycrystalline ferrite-based laminate composites. The large CME coefficients in both dc- and self-biased modes are attributed to the high transverse piezoelectric coefficient (d31 ∼ −421 pC/N) of the piezoelectric phase Sm:PMN-PT. High converse magnetoelectric coefficient and characteristic advantages of ferrite-based magnetoelectric (ME) materials such as low eddy current losses make this composite a potential candidate for the ME devices operating in the converse mode. In particular, its performance characteristics for two applications —voltage to current converter, and as a magnetic switch —have been investigated. The laminate composite exhibits current to voltage conversion performance of 14 mA/V at the resonance frequency. The performance characteristics as a magnetic switch show that the bi-stable states separated by 25 G can be realized through an AC signal of 5V.

Enhancement of magnetoelectric (ME) coupling by using textured magnetostrictive alloy in 2-2 type ME laminate

Abstract In this study, we have investigated the effect of crystallographic orientation of magnetostrictive Galfenol (Fe83Ga17) on magnetoelectric (ME) coupling in 2-2 type ME laminates. (001) oriented Galfenol is fabricated by directional solidification method and textured along with two different directions, i.e., (001) along the length direction and (001) along the thickness direction and laminated with piezoelectric 32-mode PMN-PZT single crystal to form ME laminates. The length textured Galfenol shows 37% higher magnetostriction than that of thickness textured Galfenol. Similarly, ME laminate with length textured Galfenol (32-L) possesses higher ME coefficients than that of ME laminate with thickness textured Galfenol (32-T) at both the off-resonance and resonance conditions. At the resonance frequency, 32-L laminate showed around 150% higher direct and converse ME coefficients as compared to that of 32-T laminate owing to the higher magnetostriction of length textured Galfenol.

A comparison of converse magnetoelectric coupling effect of YIG film on FE and AFE ceramic substrates

The magnetoelectric properties of laminated heterostructures consisting of ferromagnetic yttrium iron garnet (YIG) films deposited on antiferroelectric (AFE) (Pb0.97La0.02)(Zr0.6Sn0.3Ti0.1)O3 (PLZST) and on ferroelectric (FE) 0.75Pb(Mg1/3Nb2/3)O3-0.25Pb(Zr0.48Ti0.52)O3 (PMN-PZT) ceramics are compared in this work. In particular, the Converse Magneto Electric (CME) coefficient is evaluated for these two types of structures. When the electric field is applied on an AFE ceramic, the CME coefficient peaks at the switching field and, without bias magnetic field, the maximum value is 11.6 × 10−8 s/m. In case of a FE ceramic, at the electric coercive field, the CME coefficient can reach 17 × 10−8 s/m at 0 Oe. Each structure has advantages and disadvantages depending on the applications.

Electrical Manipulation of Magnetic Anisotropy in a Fe81Ga19/Pb(Mg1/3Nb2/3)O3 - Pb(ZrxTi1−x)O3 Magnetoelectric Multiferroic Composite

Magnetoelectric composites are an important class of multiferroic materials that pave the way towards a new generation of multifunctional devices directly integrable in data storage technology and spintronics. This study focuses on strain-mediated electrical manipulation of magnetization in an extrinsic multiferroic. The composite includes 5 nm or 60 nm Fe$_{81}$Ga$_{19}$ thin films coupled to a piezoelectric (011)-PMN-PZT. The magnetization reversal study reveals a converse magnetoelectric coefficient $\alpha_\mathrm{CME,max} \approx 2.7 \times {10^{-6}}$ s.m$^{-1}$ at room temperature. This reported value of $\alpha_\mathrm{CME}$ is among the highest so far compared to previous reports of single-phase multiferroics as well as composites. An angular dependency of $\alpha_\mathrm{CME}$ is also shown for the first time, arising from the intrinsic magnetic anisotropy of FeGa. The highly efficient magnetoelectric composite FeGa/PMN-PZT demonstrates drastic modifications of the in-plane magnetic anisotropy, with an almost 90$^{\circ}$ rotation of the preferential anisotropy axis in the thinner films under an electric field E = 10.8 kV.cm$^{-1}$. Also, the influence of thermal strain on the bilayer's magnetic coercivity is compared to that of a reference bilayer FeGa/Glass at cryogenic temperatures. A different evolution is observed as a function of temperature, revealing a substrate thermo-mechanical influence which has not yet been reported in FeGa thin films coupled to a piezoelectric material.

Multiphysics computational analysis of multiferroic composite ring structures

Due to the importance of composite multiferroic structures in numerous applications including sensing, actuation, and communication, concerted analytical and experimental efforts have been afforded to these types of structures in pursuit of fundamental understanding of their behavior in the presence of different stimuli. In this study, a finite element-based Multiphysics computational framework was established to investigate a multiferroic composite ring structure consisting of an inner Terfenol-D magnetostrictive ring and an outer lead zirconate titanate (PZT) piezoelectric ring. In a precursor to the full composite investigation, the computational framework was applied to a standalone Terfenol-D magnetostrictive ring structure and was found to capture the intricacies of the interaction of the magnetic field and the geometry including magnetic shielding and shape anisotropy. When extended to the composite structure, the computational model continued to perform reasonably well in comparison to previous experimentally reported data. The forecasted converse magnetoelectric coefficient of a PZT/Terfenol-D concentric composite ring structure was found to be 357 mG/V, which is in excellent agreement with 334 mG/V experimentally reported coupling coefficient for the same geometry. Moreover, the measured and calculated mechanical strains were in reasonable agreement; given the underlying assumptions of the computational model. Future work should focus on further developing the computational model to include the nonlinear magnetostrictive and piezoelectric constitutive relationship as well as the time-dependence of the response to accelerating the development cycle of devices based on magnetoelectric composites.

E-tunable magnetic susceptibility and reversible magnetization switching in YIG/Pt/PMN-PZT/Pt heterostructure by low electric and magnetic fields

The electric field (E) controlled magnetism in the multiferroic heterostructure comprising polycrystalline yttrium iron garnet (YIG) film, Pt electrodes, and lead magnesium niobate-lead zirconate titanate (PMN-PZT) ceramic is presented in this work. The electric-field-dependent magnetization and susceptibility of YIG film reveal the strain-mediated transformation of magnetocrystalline anisotropy. A strong converse magnetoelectric (CME) effect has been observed in the YIG/Pt/PMN-PZT/Pt heterostructure, and the CME coefficient can reach 17 × 10−8 s/m at 0 Oe and 4.2 kV/cm. The reversible magnetization switching by means of a low voltage pulse (±4.6 kV/cm) can be realized at 0 Oe in the YIG/Pt/PMN-PZT/Pt heterostructure, and the E-tunable susceptibility can reach Δχ/χ0+ = 55.5% at 20 Oe and 4 kV/cm. These results show great potential in power-efficient magnetoelectric components for information storage and tunable devices.

E-field control of magnetization and susceptibility of AFE-based YIG/PLZST heterostructure

The magnetoelectric properties of a laminated heterostructure consisting of ferromagnetic yttrium iron garnet (YIG) film and antiferroelectric (Pb0.97La0.02) (Zr0.6Sn0.3Ti0.1)O3 (PLZST) ceramic is, for the first time, reported in this work. The electric-field-controlled susceptibility, a shift of the coercive magnetic field and magnetization variations are demonstrated in YIG/PLZST multiferroic heterostructure. A large variation of the relative magnetic susceptibility is observed, practically 33% at a low magnetic field of 10 Oe. A sharp reduction of magnetization occurs at the antiferroelectric-ferroelectic phase transition field of PLZST ceramic. Thus the converse magnetoelectric coefficient peaks at the switching field and the maximum can reach 11.6 × 10−8 s/m without bias magnetic field. These features indicate that antiferroelectric materials can also be alternative candidates to combine with ferromagnetic materials for magnetoelectric tunable devices.

Anomalous Magnetoelectric Coupling Effect of CoFe2O4–BaTiO3 Binary Mixed Fluids

We report an anomalous magnetoelectric coupling effect of CoFe2O4–BaTiO3 binary mixed fluids, which were prepared by distributing surfactant treated (oleic acid) magnetic CoFe2O4 and ferroelectric BaTiO3 nanoparticles into highly insulating base fluid (silicone oil). A strong coupling effect in this mixed fluid has been observed, in which both the remnant polarization/magnetization and coercive electric/magnetic field are found to be enhanced visibly in the presence of an external magnetic/electric field. Colossal converse and direct magnetoelectric coupling coefficients are estimated to be αH = 1.22 × 10–4Oe·cm/V and αE = 2.52 × 104 V/(cm·Oe), respectively. Moreover, this coefficient clearly depends on the volume fraction of the two kinds of particles and the applied external magnetic/electric field. Even more amazing, CoFe2O4 also shows a strong magnetoelectric coupling effect with a coefficient as high as 4.2 × 10–5 Oe·cm/V. Further analysis indicates that the aggregated, chain-like structure of the pa...

Electric field tuning of magnetization in an antiferroelectric‐based heterostructure: Example of NMG/PLZST/NMG

AbstractA magnetoelectric (ME) heterostructure was fabricated by depositing a Ni‐Mn‐Ga (NMG) magnetic film on an antiferroelectric (AFE) PLZST—(Pb, La)(Zr, Sn, Ti)O3—ceramic substrate. Significant and reversible electric field‐induced relative magnetization changes (∆M/M0) were firstly observed in this magnetic/AFE heterostructure, and the ∆M/M0 vs electric field loops have been found to correspond well with the strain‐electric field curve of PLZST ceramic. The maximum ∆M/M0 variation can reach 15%, indicating an obvious strain‐mediated converse magnetoelectric (CME) effect. A maximum CME coefficient of 1.14 × 10‐9 s/m was obtained at the switching electric fields of PLZST. The collected results suggest that AFE materials with a large electric‐field‐induced phase transition strain could be alternative candidates in ME coupling heterostructures.