Resonant Magnetoelectric Research Articles

Edge geometry effects on resonance response of electroplated cylindrical Ni/PZT/Ni magnetoelectric composites

Trilayer Ni/PZT/Ni cylindrical magnetoelectric (ME) composites were prepared by electrodeposition, a process, which creates sub-millimeter raised edges due to current concentration near sharp points. The ME response in both axial and vertical modes was measured with the edges, with only outer edges removed, and with both outer and inner edges removed. The ME voltage coefficient improved at resonance by 40% and 147% without the edges in the vertical and axial modes, respectively. The observed improvements in three different samples were only present at the ME resonance and no changes were detected outside of the ME resonance. Mechanical quality factor at resonance also improved with no effect on the resonant frequency. Experimentally demonstrated minor geometry changes resulted in substantial ME improvement at resonant frequency. This study demonstrates device performance optimization. The observed effects have been attributed to improved vibrations in terms of decreased damping coefficient and enhanced vibration amplitude at resonance.

Spin pumping in a composite high overtone bulk acoustic wave resonator

A new way of generating a pure spin current using a magnetoelectric composite high-overtone bulk acoustic-wave resonator (HBAR) based on a layered Al–ZnO–Al–Gd3Ga5O12–Y3Fe5O12–Pt structure is proposed. It is established that the efficiency of generating the rf magnetic field driving the spin current by this method exceeds that of sources which use surface acoustic waves for the excitation of magnetic dynamics and is not inferior to the efficiency of usual electromagnetic ways of exciting a pure spin current that employ microwave cavities.

Пороговый датчик магнитных полей на основе автогенератора с магнитоэлектрическим резонатором

Пороговый датчик магнитных полей на основе автогенератора с магнитоэлектрическим резонатором

Strain induced giant magnetoelectric coupling in KNN/Metglas/KNN sandwich multilayers

A lead-free magnetoelectric composite with sandwich layers of K0.5Na0.5NbO3 (KNN)/Co76Fe14Ni4Si5B (Metglas)/KNN is fabricated as a cantilever and it is characterized for its magnetic, ferroelectric, and magnetoelectric properties. Giant magnetoelectric (ME) coupling is recorded under both resonant and sub resonant conditions and the data are presented here. The observed magnetoelectric coupling coefficient reaches a maximum of 1321 V/cm Oe at resonance (750 Hz) and 9.5 V/cm Oe at a sub-resonant frequency of 50 Hz. The corresponding theoretical calculations are provided for comparison. High magnetostriction as well as initial permeability, fairly good piezoelectric properties, and low dielectric constant cumulatively contribute to the giant magnetoelectric properties in the present system. The high resonance and sub resonance ME coupling voltages make the system ideal for transducers and energy harvesting device applications.

Origin of Large Phase Shift and Magnetoelectric Resonance in Magnetoelectric Laminate Composite

Magnetoelectric composites enjoy large magnetoelectric transfer efficiency at resonance frequency, accompanying a large phase shift. We prepared two magnetoelectric laminate composites to research the origin of large phase shift and magnetoelectric characteristics by electric-field-induced strain and magnetic-field-induced strain. The piezoelectric part plays a dominant role in both the direct and converse magnetoelectric resonances. The electromechanical resonance inspires direct and converse magnetoelectric resonant peaks, and results in the magnetoelectric phase shift of near $\pi $ around the resonance frequency. However, the magnetostrictive part is difficult to inspire the magnetoelectric resonance and phase shift.

Self-biased and wide resonance band magnetoelectric effect in series-connected SrFe12O19/Metglas/Pb(Zr, Ti)O3 composites

Self-biased and wide resonance band magnetoelectric (ME) response is realized in the series-connected SrFe12O19/Metglas/ Pb(Zr, Ti)O3 composites. Both ME composites fabrication and series-connecting method are optimized in this paper. It is found that 2/5—length ratio between SFO ribbon and PZT plate is proposed to maintain the ME resonance property in the ME composites, and that series-connecting the ME components by opposite polarizations with each other is the proposal method to achieve wide resonance band ME response. Without external magnetic field, the self-biased ME composites show a resonance enhanced ME response of over 117 mV Oe−1 in a 30 kHz bandwidth frequency window. Our ME composites present a good potential for application in broadband magnetic field sensors and energy harvesters.

Stacked magnetic resonators for MRI RF coils decoupling

Parallel transmission is a very promising method to tackle B1+ field inhomogeneities at ultrahigh field in magnetic resonant imaging (MRI). This technique is however limited by the mutual coupling between the radiating elements. Here we propose to solve this problem by designing a passive magneto-electric resonator that we here refer to as stacked magnetic resonator (SMR). By combining numerical and experimental methodologies, we prove that this novelty passive solution allows an efficient decoupling of elements of a phased-array coil. We demonstrate the ability of this technique to significantly reduce by more than 10dB the coupling preserving the quality of images compared to ideally isolated linear resonators on a spherical salty agar gel phantom in a 7T MRI scanner.

A loop-gap resonator for chirality-sensitive nuclear magneto-electric resonance (NMER).

Direct detection of molecular chirality is practically impossible by methods of standard nuclear magnetic resonance (NMR) that is based on interactions involving magnetic-dipole and magnetic-field operators. However, theoretical studies provide a possible direct probe of chirality by exploiting an enantiomer selective additional coupling involving magnetic-dipole, magnetic-field, and electric field operators. This offers a way for direct experimental detection of chirality by nuclear magneto-electric resonance (NMER). This method uses both resonant magnetic and electric radiofrequency (RF) fields. The weakness of the chiral interaction though requires a large electric RF field and a small transverse RF magnetic field over the sample volume, which is a non-trivial constraint. In this study, we present a detailed study of the NMER concept and a possible experimental realization based on a loop-gap resonator. For this original device, the basic principle and numerical studies as well as fabrication and measurements of the frequency dependence of the scattering parameter are reported. By simulating the NMER spin dynamics for our device and taking the (19)F NMER signal of enantiomer-pure 1,1,1-trifluoropropan-2-ol, we predict a chirality induced NMER signal that accounts for 1%-5% of the standard achiral NMR signal.

Layer thickness and sequence effects on resonant magnetoelectric coupling in Ni/Pb(Zr,Ti)O3 cylindrical composites

Ni/Pb(Zr,Ti)O3/Ni, Ni/Pb(Zr,Ti)O3 and Pb(Zr,Ti)O3/Ni cylindrical layered magnetoelectric (ME) composites with different Ni layer thickness were prepared by electrodeposition. The resonant ME effect was studied in both axial and vertical modes. The optimal DC magnetic field increases with Ni layer thickness and resonant ME voltage coefficients are maximum at intermediate Ni layer thickness for all cases. The resonant ME effect is also influenced by magnetostrictive and piezoelectric layer sequence. The Pb(Zr,Ti)O3/Ni cylinder has the best ME performance because of the highest axial ME voltage coefficient, almost highest vertical ME voltage coefficient and lowest optimal DC magnetic field in both modes. This work provides guidance to optimize ME performance in cylindrical layered ME composites.

Integrated Magnetics and Multiferroics for Compact and Power-Efficient Sensing, Memory, Power, RF, and Microwave Electronics

The coexistence of electric polarization and magnetization in multiferroic materials provides great opportunities for realizing magnetoelectric (ME) coupling, including electric field control of magnetism, or vice versa, through a strain-mediated ME coupling in layered magnetic/ferroelectric multiferroic heterostructures. Strong ME coupling has been the enabling factor for different multiferroic devices, which, however, has been elusive, particularly at RF/microwave frequencies. In this paper, most recent progress on new integrated multiferroic devices for sensing RF and microwave electronics will be presented, including novel RF Nano-electro-mechanical systems ME resonators with picotesla sensitivity for dc magnetic fields and novel gigahertz magnetic and multiferroic integrated inductors with a wide operation frequency range of $0.3\sim 3$ GHz, a high quality factor close to 20, and a voltage tunable inductance of 50% $\sim 150$ %. At the same time, we will also demonstrate other tunable RF devices, including integrated non-reciprocal tunable bandpass filter with ultrawideband isolation more than 13 dB. These novel magnetics and multiferroic devices show great promise for applications, such as compact, lightweight, and power-efficient sensing, memory, RF, and microwave integrated electronics.

Enhanced Sensitivity With Five-Phase Heterostructure Magnetoelectric Sensor at Low Magnetic Bias Field

In this paper, we have proposed a five-phase heterostructure magnetoelectric (ME) sensor with high-permeability Fe-based nanocrystalline soft-magnetic alloy FeCuNbSiB, ferromagnetic alloy with constant elasticity FeNi and piezoelectric ceramic lead zirconium titanate (PZT). A built-in magnetic field induced by a spatially varying magnetization within the heterostructure leads to a zero-biased ME response. The corresponding zero-biased ME coefficient reaches as high as 43.75 V/ $\text {cm}\cdot \textrm {Oe}$ (3.5 V/Oe). Meanwhile, an additional stress produced by FeCuNbSiB is transferred to FeNi, which enhances the effective resonant strain coefficient for FeCuNbSiB/FeNi at low magnetic bias and decreases the required optimum dc magnetic bias $H_{\mathrm{opt,dc}}$ . Hence, the maximum resonant ME coefficient is found to reach 51.5 V/ $\text {cm}\cdot \textrm {Oe}$ (4.12 V/Oe) at $H_{\mathrm{opt,dc}}$ of only 33 Oe. $H_{\mathrm{opt,dc}}$ for our proposed ME sensor is about one-tenth of that for FeNi/PZT/FeNi. Correspondingly, the five-phase heterostructure ME sensor is able to possess the strong ME sensitivity at low bias or even zero bias.

Strong self-biased magnetoelectric charge coupling in a homogenous laminate stack for magnetic sensor

In this study, we report a strong self-biased magnetoelectric (ME) charge coupling in homogenous two-phase magnetostrictive/piezoelectric laminate stack. The proposed ME stack Ni/PZT-stack is made up of hard-processing Nickel foils (Ni) and a tape-casting multilayer Pb(Zr, Ti)O3 (PZT) plate with high capacitance. Resonant ME couplings of Ni/PZT-stack with different thickness ratio (n) of Ni foil are investigated in detail. The experimental results show that the Ni/PZT-stack with n = 0.4 has maximum zero-biased resonant ME charge coefficient (αQ,r) of 47.52 nC/Oe, which is far larger higher than that previously reported for other ME laminates. The proposed self-biased miniature ME structure may be useful for multifunctional devices such as electromagnetic energy harvesting, magnetic-to-electric generators or magnet field sensing based on a charge-detection method.

Nonlinear resonant magnetoelectric coupling model for dual-peak phenomenon in magnetoelectric laminates

We investigated the dual-peak phenomenon in the response curve of the magnetoelectric (ME) coupling coefficient versus magnetic field for Terfenol-D/PZT/Terfenol-D tri-layer magnetoelectric laminated composites. Using nonlinear constitutive relations for the magnetostrictive material, an expression for the resonance ME coefficient that considers nonlinear resonance mechanical loss is established with the aid of the equivalent circuit method. The established model effectively predicts the complex behavior related to dual-peak phenomenon in regard to pre-stress, bias magnetic field, frequency of the alternating magnetic field, and nonlinear mechanical loss, and explains the origin of the dual peaks. The response curves obtained are consistent with experimental results. It can be found from the further predictions that in a given resonance frequency band, selecting an appropriate pre-stress can regulate two peaks in dual-peak curve, so that a giant ME coupling effect is obtained on the first peak, or a stronger resonance peak is achieved by adjusting stress to merge two peaks. With our resonance ME dual-peak model, we also demonstrate a giant ME coupling by regulating the dual-peak resonances by pre-stress engineering.

Unidirectional terahertz light absorption in the pyroelectric ferrimagnetCaBaCo4O7

Spin excitations were studied by absorption spectroscopy in CaBaCo4O7 which is a type-I multiferroic compound with the largest magnetic-order induced ferroelectric polarization ({\Delta}P=17mC/m2) reported, so far. We observed two optical magnon branches: a solely electric dipole allowed one and a mixed magnetoelectric resonance. The entangled magnetization and polarization dynamics of the magnetoelectric resonance gives rise to unidirectional light absorption, i.e. that magnon mode absorbs the electromagnetic radiation for one propagation direction but not for the opposite direction. Our systematic study of the magnetic field and temperature dependence of magnon modes provides information about the energies and symmetries of spin excitations, which is required to develop a microscopic spin model of CaBaCo4O7.

Magnetoelectric Coupling Characteristics of Multiphase Laminate Heterostructures Based on FeCuNbSiB Nanocrystalline Soft Magnetic Alloy

Over the last decade, multiferroic laminate heterostructures, consisting of the piezoelectric layer (such as PZT) and the magnetostrictive layer (such as Terfenol-D), have attracted considerable attention due to their high Curie or Neel temperature and large magnetoelectric (ME) effect at room temperature. The ME laminate materials have demonstrated potential in many applications such as transducers, actuators, magnetic field sensors, energy harvesters, and other devices [1]. ME effect in the multiferroic laminated heterostructures is essentially attributed to the elastic coupling between the piezoelectric and magnetostrictive layers [2]. The effective piezomagnetic coefficient and effective mechanical quality factor play a key role in the performance of the ME materials. However, owing to the small values of the mechanical quality factor and relative permeability, the ME voltage coefficient of the traditional Terfenol-D/PZT (MP) composites is difficult to increase [3, 4]. The nanocrystalline FeCuNbSiB soft magnetic alloy would be a good solution, according to the large interface stress-strain coupling effects. In this paper, a series of FeCuNbSiB/Terfenol-D/PZT (F/M/P) multi-phase laminate heterostructures are presented (Fig. 1), whose ME coupling characteristics have been investigated. Compared to traditional MPM, the ME coupling characteristics of the proposed FMPMF heterostructures were significantly improved. The resonant and low-frequency ME voltage coefficient of the proposed F/M/P heterostructures could be tuned by controlling the layer numbers N. When N is 7 (FMPMPMF), the maximum value of resonant ME voltage coefficient achieves 8.69 V/Oe, which is about 3.65 times higher than that for FMP, 1.81 times higher than that for FMPMF (Fig. 2(a)). Meanwhile, the maximum value of low-frequency ME voltage coefficient for FMPMPMF heterostructures achieves 69.6 mV/Oe at H b =378 Oe (Fig. 2(b)). Remarkably, it indicates that the F/M/P heterostructures have great potential as far as its application in highly sensitive dc magnetic field sensing and vibration energy harvesting.

Zero-Biased Magnetoelectric Effects in Five-Phase Laminate Composites With FeCoV Soft Magnetic Alloy

Magnetoelectric (ME) response has attracted continuously increasing interest in the past decades due to its potential applications in many new multifunctional devices, including magnetic storage, magnetic sensors, current sensors, and energy harvesters.[1] In general, single-phase ME materials are difficult to be utilized in such devices because the ME responses are weak and mostly appear at low temperature. Compared to single-phase ME materials, Magnetoelectric composites consisting of piezoelectric materials (e.g., PZT and PMN-PT) and magnetostrictive materials (e.g., Terfenol-D and Metglas) exhibit strong ME responses at room temperature, and meet the demands of practical application. However, in order to obtain high piezomagnetic coefficient and ME response, most of the reported ME composites require an external bias magnetic field (H bias ) that increases their sizes and costs.[2] To overcome these limitations, more and more researchers have focused on zero-biased ME effects in the composites. Recently, some studies have attempted to achieve high zero-biasd ME response with different methods. For example, Mandal et al. have reported that ME composite of PZT and graded NZFO show an enhancement in the ME coefficient at zero bias. [3]Yang et al. demonstrated a methodology for achieving zero-biased ME response by changing the electrical connections in a sandwiched ME structure of NKNLS-NZF/Ni/NKNLS-NZF. These methods are difficult to realize and require special synthesis process. In fact, utilizing an internal magnetic bias of the magnetostrictive materials in ME composite is a feasible way to solve thisproblem. In this paper, a new zero-biased five-phase laminate composite consists of FeCoV/Terfenol-D/Pb(Zr 1 - x , Ti x )O 3 (PZT)/Terfenol-D/FeCoV (FMPMF) is presented, whose magnetoelectric (ME) coupling characteristics have been investigated. Due to the different magnetic characteristics between FeCoV and Terfenol-D (such as permeability, saturation magnetization and magnetostriction), an internal magnetic field is formed in the compound magnetostrictive layers. It is found that the resonant ME voltage coefficient of five-phase laminate composite is much larger than that of traditional Terfe-nol-D/PZT/Terfenol-D (MPM) laminate composite at zero bias. The experimental results show that the zero-biased resonant ME voltage coefficient strongly depends on the thickness of FeCoV layers as shown in Fig.1. When the thickness of FeCoV layers is 90μm, we obtain the optimum resonant ME voltage cofficient of 1.96 V/Oe at the zero magnetic bias field, which is 1.75 times as great as that of MPM laminate composite. Furthermore, a low-frequency ME voltage coefficient of 50.4 mV/Oe is achieved, which is 2.1 times higher than that of the MPM laminate composite. Meanwhile, the induced zero-bias ME voltage of FMPMF laminate composite shows an excellent linear relationship to ac magnetic field both at the low frequency (1kHz) and the resonant frequency (115.14kHz) as shown in Fig.2. It indicates that the proposed zero-biased five-phase laminate composite shows promising applications for high sensitive dc magnetic field sensors, zero-biased ME transducers and small-size energy harvesters.

Enhanced Magnetoelectric Effect in Permendur/Pb(Zr0.52Ti0.48)O3 Laminated Magnetostrictive/Piezoelectric Composite

In this work, after investigating three typical magneto-electric (ME) composites, Permendur/Pb(Zr0.52Ti0.48)O3(PZT), Metglas/PZT, and Tefenol-D/PZT, with the same dimensions and different saturation magnetostriction and magnetic permeability, the most excellent ME performance is observed in the Permendur/PZT laminates, which agrees well with the predicted results from the figure of merit. The low-frequency and resonance ME coefficients of Permendur/PZT composite are ~23.1 V/Oe.cm and ~309 V/Oe.cm at the optimal dc bias magnetic field of ~250 Oe, respectively. The strong ME effect of Permendur/PZT composite gives it potential in practical magnetic sensitive device applications.

Theoretical study on nonlinear magnetoelectric effect and harmonic distortion behavior in laminated composite

A theoretical model is established for nonlinear magnetoelectric (ME) effect and harmonic distortion behavior in laminated composite, in which the complex nonlinear mechanical-thermo-magnetic characteristics of magnetostrictive phase are taken into consideration. Both the low-frequency and the resonant ME effects are derived by the elastic mechanics method. In this model, the output ME voltage is divided into three parts: a dc term, a linear ac term and a nonlinear ac term. Considering the temperature effect, this model is adopted to predict the dependences of ac voltages on bias magnetic field, frequency of ac magnetic field, the volume fraction of piezoelectric phase and interfacial parameter. Then, the competition relationship between linear and nonlinear ac voltages is discussed. To clearly describe the nonlinear characteristics of the proposed sample, a distortion factor θ is used for characterizing the harmonic distortion behaviors. The dependences of θ on the frequency of ac magnetic field and temperature under different ac magnetic fields are also studied. Finally, the predictions of harmonic distortion behaviors with changing bias magnetic field are obtained. The calculated linear ME coefficient shows a good agreement with the previous experimental data. It showed that: linear ac voltage and linear piezomagnetic coefficient present the same trend as the bias magnetic field increases, and nonlinear ac voltage shows the same trend as the absolute value of nonlinear piezomagnetic coefficient with increasing bias magnetic field; with temperature increasing, the output ME voltages decrease; operating temperature has a minimal effect on the required magnetic field corresponding to the optimal value of the output ME voltages, while it cannot alter the optimal value of piezoelectric phase's volume fraction; the nonlinear ac voltage presents more resonant frequencies than the linear one in the same range. Also, a definite multiple relationship is observed between the corresponding resonant frequencies of linear and nonlinear voltages; a larger θ leads to a more serious harmonic distortion, which is influenced by the frequency of ac magnetic field and temperature; bias magnetic field can be applied to adjust the harmonic distortion behaviors.

Anisotropy of the magnetoelectric effect in tri-layered composites based on single-crystalline piezoelectrics

A numerical and experimental study of the anisotropy of the magnetoelectric (ME) response in tri-layered composites based on single-crystalline piezoelectrics has been carried out. Quasi-static and resonant direct ME measurements were performed on Metglas/Piezoelectric/Metglas tri-layered structures featuring thin foils of the magnetostrictive Metglas alloy and differently oriented piezocrystals of LiNbO3 (LNO) and GaPO4 (GPO). The transversal ME effects were found to be strongly dependent on the direction of the applied in-plane magnetic bias fields as well as the orientation of the crystals. Multiple peaks of the ME response were observed corresponding to different contour resonance modes of the piezocrystals. The largest ME coefficient of up to 249 V/(cm·Oe) was observed for a composite with a 41 °Y-cut LNO crystal at 323.1 kHz. In summary, we have shown that crystalline lead-free LNO and GPO can exhibit relatively large anisotropic ME effects in multilayers. The relations between the directional ME coupling and the material constants of the differently oriented piezocrystals were pinpointed. The precise control of this orientation should therefore allow one to engineer almost any desired quasi-static and resonant ME anisotropic properties for any specific application.

Microwave Magnetochiral Dichroism in the Chiral-Lattice Magnet Cu_{2}OSeO_{3}.

Through broadband microwave spectroscopy in Faraday geometry, we observe distinct absorption spectra accompanying magnetoelectric (ME) resonance for oppositely propagating microwaves, i.e., directional dichroism, in the multiferroic chiral-lattice magnet Cu_{2}OSeO_{3}. The magnitude of the directional dichroism critically depends on the magnetic-field direction. Such behavior is well accounted for by considering the relative direction of the oscillating electric polarizations induced via the ME effect with respect to microwave electric fields. Directional dichroism in a system with an arbitrary form of ME coupling can be also discussed in the same manner.