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The resonant magnetoelectric (ME) effect of Fe78Si9B13/Pb(Zr,Ti)O3 (FeSiB/PZT) composites with a surface-modified Fe78Si9B13 amorphous alloy has been studied. The surface-modified FeSiB can improve the ME coefficient at the resonant frequency by optimizing the magnetomechancial power conversion efficiency. The maximum ME coefficient of the surface-modified ribbons combined with soft PZT (PZT5) is two-thirds larger than that of the composites with fully amorphous ribbons. Meanwhile, the maximum value of the ME coefficient with surface-modified FeSiB ribbons and hard PZT (PZT8) is one-third higher compared with the fully amorphous composites. In addition, experimental results of magnetomechanical coupling properties of FeSiB/PZT composites with or without piezoelectric layers indicate that the power efficiency of the composites first decreases and then increases with the increase in the number of FeSiB layers. When the surface crystalline FeSiB ribbons are combined with a commercially available hard piezoelectric ceramic plate, the maximum magnetoelectric coupling coefficient of the ME composite reaches 5522 V/(Oe*cm), of which the electromechanical resonant frequency is 23.89 kHz. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) gyrators are unique circuit elements capable of direct conversion of the current to voltage or vice versa. In order to understand the power conversion and loss processes in the gyrators, an equivalent input loss factor has been developed in this paper based on Mason's model (equivalent circuit model). This factor serves to understand the loss transferring mechanism and to evaluate the conversion efficiency for the electric power in ME gyrators. Studies have been carried out for modeling the power conversion in both the solenoid and the ME core. Several important factors have been proposed and discussed to enhance the conversion efficiencies in the electric–magnetic–mechanical three-phase conversion process. A simplification of our equations reveals that the efficiency of the ME gyrator is related to the product of the effective coupling (k2 $_{\text{eff, m}}$) and mechanical quality (Qmech). According to our model, magnetic and electric materials with highk $_{\text{eff, m}}$ andQmechvalues are the key ingredients to enhance the efficiency of ME gyrators. We have successfully realized a power efficiency of 92% based on a Metglas/hard-PZT ME gyrator, which showed a good correlation to the predicted values. [ABSTRACT FROM AUTHOR]

The influence of yttrium (Y) ion substitution on the magneto-mechanical properties of nickel-zinc ferrite (Ni0.7Zn0.3YxFe2-xO4) or NZFO-Y and the power efficiency (η) of magnetoelectric (ME) gyrators consisting of NZFO-Y/Pb(Zr, Ti)O3 layers were studied. X-ray diffraction (XRD) of polycrystalline samples of NZFO-Y indicated that yttrium incorporated into the crystal lattice resulted in an enlargement of the lattice parameter. Also, the density and ionic hopping length were increased, and the porosity was decreased. Together, these resulted in significant changes in the magneto-mechanical coupling (k33,m) and mechanical quality (Qm) factors. It was found that k33,m decreased with the increasing Y content for 0 ≤ x ≤0.08, whereas Qm was increased. For x > 0.05, the values of k33,m and Qm were found to be nearly stable with increasing input power density (PD-Ms) up to 47 W/in3. Under this high power driving condition for 20 min, we found that the power conversion stability of ME gyrators was increased with the increasing Y content in the ferrite and that a maximum power conversion efficiency occurred near 77%. These findings offer the potential for ferrite-based ME gyrator applications in power electronic conversion devices. [ABSTRACT FROM AUTHOR]

This report is on a new class of magnetostatically tunable magneto-impedance and magneto-capacitance devices based on a composite of ferromagnetic Metglas and ferroelectric lead zirconate titanate (PZT). Layered magneto-electric (ME) composites with annealed Metglas and PZT were studied in a longitudinal in-plane magnetic field-transverse electric field (L-T) mode. It was found that the degree of tunability was dependent on the annealing temperature of Metglas. An impedance tunability (ΔZ/Z0) of ≥400% was obtained at the electromechanical resonance (EMR) frequency (fr) for a sample with Metglas layers annealed at Ta = 500oC. This tunability is a factor of two higher than for composites with Metglas annealed at 350oC. The tunability of the capacitance, (ΔC/C0), was found to be 290% and -135k% at resonance and antiresonance, respectively, for Ta = 500oC. These results provide clear evidence for improvement in static magnetic field tunability of impedance and capacitance of ME composites with the use of annealed Metglas and are of importance for their potential use in tunable electronic applications. [ABSTRACT FROM AUTHOR]

A high efficiency self-biased magnetoelectric (ME) gyrator operating under zero magnetic bias field (HBias=0) was developed. It consists of a threephase nickel-zinc ferrite/Metglas/piezoelectric longitudinal-transverse (L-T) ME laminate and a solenoid. Laminates with different length-width (L/W) ratios, together with various thickness (number of Metglas foils) ratios between ferrite and Metglas layers, were studied. A maximum power conversion efficiency (η) of 72% was found at the fundamental electromechanical resonance for a high L/W ratio of 18.7. The high zero-bias η could be attributed to a higher mechanical quality factor (Qm) and the low demagnetization effect (Nz) of nickel-zinc ferrite laminates of higher L/W. Eliminating the external magnetic bias will facilitate miniaturization of ME gyrators for use in portable electronics and medical applications. [ABSTRACT FROM AUTHOR]

A magnetoelectric (ME) gradiometer consisting of two Metglas/Pb(Zr,Ti)O3 fiber-based sensors has been developed. The equivalent magnetic noise of both sensors was first determined to be about 60 pT/√Hz while using an H-field modulation technique. The common mode rejection ratio of a gradiometer based on these two sensors was determined to be 74. The gradiometer response curve was then measured, which provided the dependence of the gradiometer output as a function of the source-gradiometer-normalized distance. Investigations in the presence of vibration noise revealed that a ME gradiometer consisting of two ME magnetometers working under H-field modulation was capable of significant vibration rejection. The results were compared to similar studies of ME gradiometers operated in a passive working mode. Our findings demonstrate that this active gradiometer has a good vibration rejection capability in the presence of both magnetic signals and vibration noise/interferences by using two magnetoelectric sensors operated under H-field modulation. [ABSTRACT FROM AUTHOR]

The quasi-static magnetic field detection of a layer-bonded magneto(elasto) electric (ME) laminate has been investigated by measuring the in-plane electric capacitance via its interdigital electrodes close to the piezoelectric resonant frequency. The ME-layered composite is considered as a stress-induced dielectric effect because there is practically no direct response of the electric capacitance to an external magnetic field. The sensitivity is dominated by the magnetoelastic coupling in the magnetic layer and on the stress induced by the permittivity change in the piezoelectric layer. The low-frequency magnetocapacitance effect is sensitive to an external magnetic bias which can modulate the electric permittivity by producing a stress. The magnetoelastic coupling is another important parameter for this magnetic field detection mode. For a given magnetic field, the amplitude of the magnetostriction is directly related to this parameter as well. Therefore, an optimal magnetic bias can maximize the induced strain or stress which is coupled into the piezoelectric layer through the change of the electric permittivity in this layer. To evaluate the sensitivity and the noise performance by the magnetocapacitance effect, we have used the piezoelectric and magnetic constitutive equations to predict the permittivity dependence. Experimentally, this sensor achieved an equivalent magnetic noise spectral density, presently still limited, by the noise of the detection electronics, $\sim 100$ pT/ $\surd $ Hz at 1 Hz and offered a dc detection capability. With the model and experimental nonlinear factors, an equivalent sensor noise spectral density close to the pT/ $\surd $ Hz can be ultimately predicted considering the mechanical loss limitation of the sensor. [ABSTRACT FROM AUTHOR]

By using nonlinearity effects in magnetostrictive -piezoelectric laminated sensors, modulation techniques can transfer low-frequency signals to higher frequencies. Theory predicts that the transfer ability depends mainly on the amplitude of the carrier signal and the sensor nonlinearity. This was confirmed by our experiments. We present the first analysis on a ME noise model associated to a modulation technique. Furthermore, the overall equivalent magnetic noise was analyzed, and shown to be dominated only by the signal transfer ability and the output electrical noise level appearing around the carrier frequency. [ABSTRACT FROM PUBLISHER]

Taking advantage of magneto-elasto-electric interactions, new laminated composites of magnetostrictive and piezoelectric layers have been developed for highly sensitivity magnetoelectric (ME) sensors. The ME sensor design chosen in this study was based on long-type Metglas composites laminated together with piezoelectric fibers. In this paper, we analyze the expected limit of the magnetic noise of ME sensor versus its intrinsic characteristics and electronic setup. Theory calculations and experimental results are compared, and are well supported by noise measurements. Moreover, the presented results show very impressive performances in terms of the equivalent magnetic sensor noise. A 65 \ pT/\surdHz equivalent magnetic noise was achieved at 1 Hz, while reaching values as low as 70 fT/\surdHz near the ME resonant frequency. [ABSTRACT FROM PUBLISHER]

Magnetoelectric (ME) power efficiency is a more important property than the ME voltage or the current coefficients for power conversion applications. This paper introduces an analytical model that describes the relation between the external magnetic field and the power efficiency in layered ME composites. It is a two-phase model. The first fragment establishes the expression between the magnetic field strength and the temperature increase within an operating period. It uses a magneto-elasto-electric equivalent circuit model that was developed by Dong et al. Following previous investigations; the main loss source is the mechanical power dissipation. The second fragment links the power efficiency and the temperature increase in a heat-balanced system. This method is generally used by researchers in the piezoelectric field. The analytical model and the experimental data shows that the decrease of the power efficiency in a laminated composite is between 5% and 10% for a power density of 10 W/in3 (0.61 W/cm3) to 30 W/in3 (1.83 W/cm3). The failure mechanism/process of ME composites under high power density can be estimated/monitored by the proposed method for ME composites in practical applications. [ABSTRACT FROM AUTHOR]

Current-to-voltage conversion ratio (a) as a function of the magnetic bias, (b) as a function of the load resistor and (c) as a function of the power density. Input and output power levels (d) as a function of the magnetic bias, (e) as a function of the load resistor and (f) as a function of the power density. Power efficiency (g) as a function of the magnetic bias, (h) as a function of the load resistor and (i) as a function of the power density. • Achievement of a power efficiency of 95% in FeCoSiB/PZT magnetoelectric gyrators. • Measured magnetoelectric coefficient of 2200 (V/cm)/Oe at resonance; measured magnetoelectric charge coefficient of 32 (mC/cm2)/Oe at resonance; measured open loop current-to-voltage ratio of 50–60 kV/A at resonance. • Enlarged sizes increasing the magnetomechanical coupling factor between FeCoSiB layers and the coil in accordance with theoretical approaches. A Magneto-Electric (ME) gyrator with a superior power efficiency of 95 % has been achieved based on a two-phase solid-state ME laminate. This ME gyrator consists of a winding coil that generates a magnetic field as the first step to realize electromagnetic energy transfer. A magneto-electric composite, serving as the second step, then converts the power from magnetic to electric forms. The laminate consists of two iron-cobalt based amorphous alloy layers bonded to a lead zirconate titanate plate. It has a giant magneto-electric coefficient of around 2200 (V/cm)/Oe at its mechanical resonant frequency (≈ 44 kHz) in structure. Approaching methods based on maximum power transfer (MPT) efficiency theory and the equivalent loss factor (ELF) from the input port have been introduced to evaluate the power efficiency of the ME gyrator. The expected MPT efficiency is 96.5 % at a power volume density of 0.1 W/in3 (6.1 mWatt/cm3), and 93.2 % up to 20 W/in3 (1.22 W/cm3). The ELF explains that the magnetomechanical conversion efficiency is related to the volume of the magnetic phase which is the dominating term in the power efficiency. [ABSTRACT FROM AUTHOR]

Magneto-elasto-electric (ME) coupling heterostructures, consisting of piezoelectric layers bonded to magnetostrictive ones, provide for a new class of electromagnetic emitter materials on which a portable (area ~ 16 cm2) very low frequency (VLF) transmitter technology could be developed. The proposed ME transmitter functions as follows: (a) a piezoelectric layer is first driven by alternating current AC electric voltage at its electromechanical resonance (EMR) frequency, (b) subsequently, this EMR excites the magnetostrictive layers, giving rise to magnetization change, (c) in turn, the magnetization oscillations result in oscillating magnetic fields. By Maxwell's equations, a corresponding electric field, is also generated, leading to electromagnetic field propagation. Our hybrid piezoelectric-magnetostrictive transformer can take an input electric voltage that may include modulation-signal over a carrier frequency and transmit via oscillating magnetic field or flux change. The prototype measurements reveal a magnetic dipole like near field, demonstrating its transmission capabilities. Furthermore, the developed prototype showed a 104 times higher efficiency over a small-circular loop of the same area, exhibiting its superiority over the class of traditional small antennas. [ABSTRACT FROM AUTHOR]