Peter Finkel

Voltage control of magnetism in FeGaB/PIN-PMN-PT multiferroic heterostructures for high-power and high-temperature applications

We report strong voltage tuning of magnetism in FeGaB deposited on [011]-poled Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) ternary single crystals to achieve more than 2 times broader operational range and increased thermal stability as compared to heterostructures based on binary relaxors. Voltage-induced effective ferromagnetic resonance field shift of 180u2009Oe for electric field from −6.7u2009kV/cm to 11u2009kV/cm was observed in FeGaB/PIN-PMN-PT heterostructures. This strong magnetoelectric coupling combined with excellent electric and temperature stability makes FeGaB/PIN-PMN-PT heterostructures potential candidates for high-power tunable radio frequency/microwave magnetic device applications.

Giant magnetoelectric effect in nonlinear Metglas/PIN-PMN-PT multiferroic heterostructure

In this paper, we demonstrate high converse magnetoelectric (ME) coupling in a Metglas/Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) laminated ME composite by exploiting stress and field induced reversible ferroelectric-ferroelectric phase transitions in a relaxor ferroelectric single crystal. The approach exploits large transformational strain induced by low applied electric field in a PIN-PMN-PT crystal that was mechanically stressed close to a rhombohedral to orthorhombic phase transformation. The ME coefficient was enhanced by an order of magnitude as compared to the linear piezoelectric regime, with a maximum value of 1.3u2009×u200910−7 s m−1 in non-resonant mode. This phenomenon can thus be exploited to provide improvements in the development of ME devices and magnetic sensors.

Mechanical Noise Limit of a Strain-Coupled Magneto(Elasto)electric Sensor Operating Under a Magnetic or an Electric Field Modulation

The mechanical noise limit of a strain-coupled magneto(elasto)electric composite has been investigated when a magnetic or an electric field modulation is applied to sense a low-frequency magnetic field and access dc field measurement capabilities. The sensitivity and noise of such a composite sensor were derived from constitutive equations based on the piezoelectric and ferromagnetic material properties. The analysis was used to evaluate the equivalent noise floor of the composite sensor and to explain the origin of noise by constituting a mechanically coupled electromagnetic model. Experimental measurements revealed a good fit with the proposed model. For example, an equivalent magnetic noise level of ~60 pT/Hz at 1 Hz with dc capability was achieved using an appropriate field modulation.

Sensitivity and Noise Evaluation of a Bonded Magneto(elasto) Electric Laminated Sensor Based on In-Plane Magnetocapacitance Effect for Quasi-Static Magnetic Field Sensing

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, ~100 pT/√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/√Hz can be ultimately predicted considering the mechanical loss limitation of the sensor.

Energy harvesting using the FER–FEO phase transformation in [011] cut single crystal PIN-PMN-PT

This study addresses the effects of frequency and load resistance on energy harvesting using a mechanically excited ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN-PMN-PT) single crystals. The crystals were mechanically driven through the phase transformation, and voltage across a resistive load was measured. The effects of frequency and resistive load on the electrical energy generated were measured. Over the range of frequencies and load impedances tested, the crystals behaved as a charge source. The current increased linearly with frequency, and the voltage increased linearly with load impedance. Impedance matching to maximize the energy harvested is discussed. The energy harvested using the phase transformation was on average 27 times, with a peak of 108 times, the energy harvested using the same crystals operating in the linear piezoelectric regime under the same stress excitation amplitude.

Frequency reconfigurable phase modulated magnetoelectric sensors using ΔE effect

Magnetoelectric composites have shown promise in low power magnetic field sensing with responsive detection of low frequency fields through the modulation of electromechanical resonance by exploiting a nonlinearity in magnetoelastic properties (ΔE effect). There is also the as-of-yet unrealized potential of tuning this effect to further enhance the shift in resonant frequency of these devices. In the present work, the magnetic field sensitivity was modulated in a bending mode stress reconfigurable sensor through the application of uniaxial tensile stress, reaching up to 8% f0/mT. The minimum magnetic noise floor was determined by detecting the frequency shift using a phase locked loop circuit and was found to directly correspond to the maximum in magnetic field sensitivity that resulted from the ΔE effect.

Magnetoelectric gradiometer with enhanced vibration rejection efficiency under H-field modulation

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 ...

Tunable Magnetoelectric Bending Resonance for Sensing Static Magnetic Fields

Bilayered magnetostrictive-piezoelectric composites exhibit a resonant enhancement of magnetoelectric coupling when operated under bending mode. Such composites are of importance for achieving ultrasensitive magnetometers for quasi-static magnetic fields detection by measuring the parameter variations near the resonant frequency. The detection performance is limited by diverse noise processes appearing in the composite and associated electronics, such as extrinsic interferences due to environmental vibrations and temperature variations and also loss noise related to energy dissipations in the composite. The noise source, in bending mode, is due to thermomechanical dissipations. In this paper, the field detection performance relating to this noise in a doubly clamped magnetoelectric composite is investigated by means of modulation techniques.

Non-resonant electromechanical energy harvesting using inter-ferroelectric phase transitions

Non-resonant electromechanical energy harvesting is demonstrated under low frequency excitation (<50u2009Hz) using [110]C-poled lead indium niobate-lead magnesium niobate-lead titanate relaxor ferroelectric single crystals with compositions near the morphotropic phase boundary. The efficiency of power generation at the stress-induced phase transition between domain-engineered rhombohedral and orthorhombic ferroelectric states is as much as four times greater than is obtained in the linear piezoelectric regime under identical measurement conditions but during loading below the coercive stress of the phase change. The phase transition mode of electromechanical transduction holds potential for non-resonant energy harvesting from low-frequency vibrations and does not require mechanical frequency up-conversion.

Investigation of a Bending-Mode Magneto(Elasto)electric Sensor Using a Phase Modulation With a PLL

Bending-mode magnetostrictive-piezoelectric sensors clamped at its two extremities show promising results for an enhancement of its magnetic field sensitivity by using a phase modulation (PM) technique. In this operating mode, the sensor is excited by an external carrier at its bending resonant frequency. The results of such a magnetic field sensing by a magneto(elasto)electric bilayer when using a PM technique with a phase locked loop circuitry are presented. The aim of this method is to follow the phase shift at the bending resonant frequency of the sensor, which is proportional to the applied magnetic field for the small-signal regime. We obtained a magnetic sensitivity of ~1.5 kV/T and an equivalent magnetic noise level around 80 nT/