Converse Magnetoelectric Research Articles

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.

Giant converse magnetoelectric effect in a multiferroic heterostructure with polycrystalline Co2FeSi

To overcome a bottleneck in spintronic applications such as those of ultralow-power magnetoresistive random-access memory devices, the electric-field control of magnetization vectors in ferromagnetic electrodes has shown much promise. Here, we show the giant converse magnetoelectric (CME) effect in a multiferroic heterostructure consisting of the ferromagnetic Heusler alloy Co2FeSi and ferroelectric-oxide Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) for electric-field control of magnetization vectors. Using an in-plane uniaxial magnetic anisotropy of polycrystalline Co2FeSi film grown on PMN-PT(011), the nonvolatile and repeatable magnetization vector switchings in remanent states are demonstrated. The CME coupling coefficient of the polycrystalline Co2FeSi/PMN-PT(011) is over 1.0 × 10−5 s/m at room temperature, comparable to those of single-crystalline Fe1-xGax/PMN-PT systems. The giant CME effect has been demonstrated by the strain-induced variation in the magnetic anisotropy energy of Co2FeSi with an L21-ordered structure. This approach can lead to a new solution to the reduction in the write power in spintronic memory architectures at room temperature.

Magnetoelectric response and internal friction in two-layer ceramic composites based on Mn0.4Zn0.6Fe2O4 magnetostrictor and PbZr0.53Ti0.47O3 piezoelectric

Magnetoelectric (ME) and anelastic properties of two-layer ceramic composites based on Mn0.4Zn0.6Fe2O4 magnetostrictor and PbZr0.53Ti0.47O3 piezoelectric at DC magnetic field strengths of 0–220 Oe, temperatures of 293–393 K, and volume fractions of PbZr0.53Ti0.47O3 of 0.40–0.67 were studied. It was found that a converse ME coupling coefficient α31 increases with the DC magnetic field strength Н1, passes through a maximum with the volume fraction ν, and decreases as temperature T rises. Dependences of α31 on Н1, ν, and T are explained using a model of effective parameters of a heterogeneous medium. The inverse correlation is revealed between α31 and an internal friction at resonant frequencies. Dependences of the internal friction on Н1, ν, and T are associated with the interaction of ferroelectric domain boundaries with crystal-lattice defects.

Resonance magnetoelectric effect in a composite ferromagnet–dielectric–piezoelectric Langevin-type resonator

The direct and converse magnetoelectric (ME) effects in a Langevin-type resonator are observed and investigated for the first time. The resonator comprised a disk made of lead–zirconate titanate ceramic, located between two sapphire cylinders, with layers of amorphous ferromagnet glued to its side surfaces. ME effects were observed at frequencies of bending (∼70 kHz) and longitudinal (∼200 kHz) oscillations of the resonator upon its excitation by ac magnetic and electric fields. The field conversion efficiency for the direct ME effect was α E ≈ 31 V (Oe−1 cm−1). The magnetization modulation efficiency for the converse ME effect reached α B ≈ 0.72 G cm−1 V−1. The nonlinear ME effects such as frequency doubling, frequency mixing, and resonance frequency shift are observed at high field amplitudes. The magnitude of both the direct and converse ME effects in the resonator is controlled by an external dc magnetic field. The Langevin-type ME resonators can be used in highly sensitive magnetic field sensors, controlled resonators and transformers, and other components of electronics and microsystem technology.

Theoretical analyses of magnetoelectric effects for magnetostrictive/radial mode piezoelectric transformer composite under dual ac stress and magnetic field modulation

Magnetoelectric (ME) composite based on the converse magnetoelectric (CME) effect is promising for the high sensitivity dc and low-frequency magnetic field detection application, however, the performance is restricted by the stress modulation ability of piezoelectric phases and the narrow bandwidth. This work presents a nonlinear equivalent circuit model to design a new ME composite consisting of magnetostrictive layers/radial mode piezoelectric transformer/magnetostrictive layers under dual ac magnetic field and stress modulation. The theoretical model is based on the nonlinear constitutive relationships of magnetostrictive material, motion equation with imperfect interface condition, and improved ME equivalent circuit. This model cannot only predict the resonant ME effects of electrically modulated ME composite under the dual ac stress and magnetic field drive, but can also predict the conventional CME and mutual inductance effects separately. Specifically, the theoretical prediction indicates that with negligible extra power consumption, the dual modulated ME composite provides higher dc and low-frequency magnetic field sensitivity with frequency conversion method and significantly wider bandwidth compared to the conventional CME effect. Such theoretical predictions are further verified by the experimental results of Metglas/piezoelectric transformer/Metglas and Terfenol-D/piezoelectric transformer/Terfenol-D laminate. The theoretical study plays a guiding role in designing the new ME magnetometer with low power consumption, high sensitivity, and wide bandwidth.

Anisotropic spin-driven ferroelectricity and magnetoelectric effect in a Y-type hexaferrite

We report a systematic study on the magnetic, dielectric, and magnetoelectric (ME) properties of the Y-type hexaferrite (Ba0.4Sr1.6)Zn2(Fe11.3Al0.7)O22 single crystal. The phase diagrams were established by the observed magnetic anomalies under magnetic field and temperature scans for the in-plane and out-of-plane cases. Intrinsic large anisotropy in the magnetodielectric and converse ME effects was revealed. The spin-driven electric polarizations induced in the ab-plane and out-of-plane were found to be closely related to the transverse conical and alternating longitudinal conical spin structures, respectively. The amplitudes of varied magnetization ΔM are about ∼0.128 μB/f.u and ∼0.0178 μB/f.u. in the E oscillating between ±1 MV/m at 100 K, corresponding to the converse ME effect coefficient of ∼3500 ps/m and ∼480 ps/m for the in-plane and out-of-plane cases, respectively. All these results demonstrate the essential and unique spin-order-induced anisotropic ferroelectricity and ME properties in these Y-type hexaferrites.

Improved sensitivity and bandwidth of hybrid magnetic sensor based on electrically modulated amorphous magnetic alloy/piezoelectric composite

This study reports an electrically modulated dc and low frequency magnetic sensor with high sensitivity and wide bandwidth. It is based on multiferroic composites consisting of amorphous magnetic alloy Metglas/piezoelectric transformer (i.e., Pb(Zr,Ti)O3/Pb(Zr,Ti)O3)/Metglas layers winded with capacitor connected excitation coils and pickup coils. By electrically exciting the piezoelectric transformer winded with coils, the periodically induced stress and magnetic field modulate the magnetization of Metglas simultaneously and cause the change of magnetic flux within the pickup coils. The output voltage is further enhanced with the resonant converse magnetoelectric (CME) and mutual inductance effects at the mechanical and LC resonance frequency, respectively. Furthermore, the asymmetric wide bandwidth property of hybrid magnetic sensor provides the enhanced low frequency magnetic field sensitivity with negligible extra power consumption compared to the CME effect. When the magnetic sensors are excited with 5 V voltage at the resonance frequency and applied with 10 Hz magnetic field, the hybrid magnetic sensor achieves the maximum magnetic field sensitivity of 2.20 V/Oe and this is about 4.89 times as high as that of CME effect (0.45 V/Oe). The limit of detection for 10 Hz magnetic field is also noticeably improved from 2.97 nT for CME effect to 590pT for the hybrid magnetic sensor.

Prediction of Strong Converse Magnetoelectric Effect in Nb‐Doped BaTiO3‐Based Polar Metals

The origin of the converse magnetoelectric (CME) effect in the Nb‐doped BaTiO3 (NBTO) polar metal is investigated by density functional theory. Unlike the Fe doping system, where the magnetic moment is chiefly contributed by eg orbitals of the Fe atom, the magnetic moment of the NBTO system is mainly contributed by the dxz/dyz orbitals of Ti (Nb) atoms and highly depends on the polarization intensity. When the in‐plane compressive strain η ≤ −2%, the magnetic moment of the NBTO system is zero because electrons predominantly occupy the dxy orbitals. However, the switching process of the ferroelectric polarization induces a strong CME effect with significant magnetic moment changes. Especially, the magnetic moment changes in the NBTO system with the compressive strain η ≤ −2%, which is dozens of times of that of the unstrained NBTO system. These results are useful for designing new ultrafast and low‐power information storage devices with remarkable electrically controlled magnetism.

Converse magneto-electric effects in a core\u2013shell multiferroic nanofiber by electric field tuning of ferromagnetic resonance

This report is on studies directed at the nature of magneto-electric (ME) coupling by ferromagnetic resonance (FMR) under an electric field in a coaxial nanofiber of nickel ferrite (NFO) and lead zirconate titanate (PZT). Fibers with ferrite cores and PZT shells were prepared by electrospinning. The core–shell structure of annealed fibers was confirmed by electron- and scanning probe microscopy. For studies on converse ME effects, i.e., the magnetic response of the fibers to an applied electric field, FMR measurements were done on a single fiber with a near-field scanning microwave microscope (NSMM) at 5–10 GHz by obtaining profiles of both amplitude and phase of the complex scattering parameter S11 as a function of bias magnetic field. The strength of the voltage-ME coupling Av was determined from the shift in the resonance field Hr for bias voltage of V = 0–7 V applied to the fiber. The coefficient Av for the NFO core/PZT shell structure was estimated to be − 1.92 kA/Vm (− 24 Oe/V). A model was developed for the converse ME effects in the fibers and the theoretical estimates are in good agreement with the data.

Modeling of electromagnetic radiation-induced from a magnetostrictive/piezoelectric laminated composite

Magnetoelectric (ME) materials can realize the conversions between electric and magnetic energy. Different from the previous studies, the electromagnetic (EM) radiation of ME materials has been adequately considered in this work. The electrical energy input can be converted into the dynamic magnetization oscillation by converse magnetoelectric (CME) effect. The antennas operate at their acoustic resonance frequency, which provides a new idea for antenna miniaturization. We analyze the CME effect and EM radiation from a vibrating ME laminated composite. The results show that the ME heterostructure resembles an ideal magnetic dipole in terms of radiating EM waves. This structure reduces the antenna size by several orders of magnitude, suggesting vast superiority of controlling magnetizations to generate EM radiation at a micro-scale.

Strong Converse Magnetoelectric Effect in a Composite of Weakly Ferromagnetic Iron Borate and Ferroelectric Lead Zirconate Titanate

This report is on a model and experiment on the nature of mechanical-strain-mediated converse magnetoelectric (CME) effect in a composite of single-crystal iron borate, a canted antiferromagnet with a weak ferromagnetic moment, and ferroelectric lead zirconate titanate (PZT). The piezoelectric strain generated in PZT by an electric field E manifested as a shift in the quasiferromagnetic resonance (FMR) field in iron borate due to strong magnetoelastic interactions. The CME interaction strength determined from data on field shift in FMR versus E is 46--54 MHz cm/kV at 5.5--6.5 GHz. The strength of the CME is comparable to values reported for composites of ferrimagnetic oxides and PZT. A model that considers the effect of piezoelectric deformation on magnetic order parameters and magnetic resonance in iron borate is proposed for the CMEs in the composite and estimated ME coupling coefficients are in good agreement with data. The E tunability of the high-frequency AFMR mode at about 300 GHz is estimated to be on the order of 1.7 MHz kV/cm and is very small relative to the quasi-FMR mode. Composites of iron borate and ferroelectrics are very attractive for use in dual electric field and magnetic field tunable signal processing devices due to strong CME interactions and the need for a rather small bias magnetic field compared with traditional ferrimagnetic oxide based devices.

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.

Engineering Resonance Modes for Enhanced Magnetoelectric Coupling in Bilayer Laminate Composites for Energy Harvesting Applications

The magnetoelectric (ME) effect in composites, a strain-mediated coupling phenomenon between piezoelectric and magnetostrictive phases, has a wide range of technological applications. Here, ME coupling phenomena are explored in $\mathrm{Pb}$-free piezoelectric, $0.5\mathrm{Ba}({\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}){\mathrm{O}}_{3}\text{\ensuremath{-}}0.5({\mathrm{Ba}}_{0.7}{\mathrm{Ca}}_{0.3}){\mathrm{Ti}\mathrm{O}}_{3}$ and piezomagnetic ${\mathrm{Ni}\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ bilayer laminate composites. The direct and converse ME coupling strengths are found to be enhanced at the electromechanical resonance modes, rather than at the off-resonance frequencies. Here, it is proposed to further enhance the ME coupling strength at electromechanical resonance modes by the in-phase superimposition of the radial and second bending modes via varying the bilayer thickness, which, in turn, varies the volume fraction of the bilayer. The proposed enhanced ME coupling is experimentally demonstrated at a theoretically envisaged bilayer thickness of about 1.8 mm. This results in a large direct ME coupling coefficient of $22.5\phantom{\rule{0.1em}{0ex}}\mathrm{V}\phantom{\rule{0.1em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.1em}{0ex}}\mathrm{O}{\mathrm{e}}^{\ensuremath{-}1}$, which is around 100% more than the values observed at individual resonance modes. The results are further validated by calculations from theoretical models. The method adopted in this work gives a roadmap to the significant enhancement of the ME effect in laminate composites.

Converse Magnetoelectric Composite Resonator for Sensing Small Magnetic Fields

Magnetoelectric (ME) thin film composites consisting of sputtered piezoelectric (PE) and magnetostrictive (MS) layers enable for measurements of magnetic fields passively, i.e. an AC magnetic field directly generates an ME voltage by mechanical coupling of the MS deformation to the PE phase. In order to achieve high field sensitivities a magnetic bias field is necessary to operate at the maximum piezomagnetic coefficient of the MS phase, harnessing mechanical resonances further enhances this direct ME effect size. Despite being able to detect very small AC field amplitudes, exploiting mechanical resonances directly, implies a limitation to available signal bandwidth along with the inherent inability to detect DC or very low frequency magnetic fields. The presented work demonstrates converse ME modulation of thin film Si cantilever composites of mesoscopic dimensions (25 mm × 2.45 mm × 0.35 mm), employing piezoelectric AlN and magnetostrictive FeCoSiB films of 2 µm thickness each. A high frequency mechanical resonance at about 515 kHz leads to strong induced voltages in a surrounding pickup coil with matched self-resonance, leading to field sensitivities up to 64 kV/T. A DC limit of detection of 210 pT/Hz1/2 as well as about 70 pT/Hz1/2 at 10 Hz, without the need for a magnetic bias field, pave the way towards biomagnetic applications.

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.

Magnetoelectric composite coupled by bonding material in energy trapping vibration for RF/microwave devices

AbstractIn this work, the magnetoelectric (ME) coupling and electrical impedance of thickness extensional vibration mode in ME composite are investigated. The piezoelectric and magnetostrictive layers are adhered by epoxy, which acts as a central substrate layer, and the vibration is trapped by the electrodes located at the center of the piezoelectric material so as to generate energy trapping vibration mode. Parametric studies are performed to evaluate the influences of epoxy thickness and electrode dimensions on ME coupling and electrical impedance. It is found that the ME coupling increases to a peak value as the central epoxy thickness increases, and then it decreases because of the clamping effect. Therefore, an optimal thickness of the epoxy layer exits to achieve the maximum ME effect. In the converse ME effect, the electrical impedance decreases and then increases vs the thickness increase of the central substrate. In addition, the electrical impedance declines as the electrode radius increases. It is numerically demonstrated that good impedance matching can be achieved by properly design of the electrode dimensions.

A low-power and high-sensitivity magnetic field sensor based on converse magnetoelectric effect

Tremendous progress has been made in boosting the realization of magnetoelectric (ME) magnetometers based on the direct ME effect (DME) for bulk ME laminates. In this work, we studied the potential of an electrically driven bulk magnetic field sensor based on the converse ME effect (CME). Starting from a discussion about the dependence of the induced voltage from the pickup coil on coil parameters and the CME coupling process, we then experimentally measured the optimized bias field in the off resonance region and observed the double-peak phenomenon that occurred within the resonance window. More importantly, the optimization with respect to the sample's dimension, excitation voltage, and frequency was conducted to improve the sensing capability for low-frequency magnetic fields. It was experimentally found that a limit of detection (LoD) of ∼115 pT for a magnetic field of 10 Hz and ∼300 pT for a magnetic field of 1 Hz was achieved when exciting the ME laminate at 1 V without any bias field. In this case, the power consumption for the ME laminate is only 0.56 mW, which is much lower compared to tens of milliwatts (10–100 mW) for optically pumped or flux gate sensors (excluding the power consumption from the electronics) and also shows advantages over conventional ME magnetic field sensors based on DME with a current pump.

Direct and converse magnetoelectric effects of sandwiched composites worked in shear-shear mode studied by uniform equivalent circuit

There are few theoretical and experimental studies on shear-shear (S-S) mode magnetoelectric composites due to the complex shear vibration theories and high resonance frequency. In this article, a uniform equivalent circuit is proposed to analyze direct magnetoelectric (DME) and converse magnetoelectric (CME) effects of S-S mode sandwiched composites. The results show DME and CME changes of S-S mode are similar to that of L-T mode and L-L mode, but S-S mode has a higher DME coefficient near the resonance frequency. This research provides an effective theoretical method for the ME research and a route for the ME devices at high frequency.