Magnetostrictive-piezoelectric Composites Research Articles

Tunable self-biased magnetoelectric effect in magnetization-graded magnetoelectric composites

Magnetoelectric (ME) composites, which are magnetostrictive-piezoelectric composites, have garnered attention for use in various application fields owing to their large ME coupling compared with single-phase multiferroic materials. The maximum ME coupling is observed when an increased DC magnetic bias field is applied, which results in large devices with degraded sensitivity due to electromagnetic noise. To address this problem, a strong self-biased ME composite that generates the maximum ME response in a zero-bias field was proposed in this study. Highly self-biased ME composites were prepared by combining soft magnetic Ni and highly permeable Metglas magnetostrictive layers with a Pb(Mg1/3Nb2/3)O3–PbZrTiO3 piezoelectric single-crystal laminate structure and inducing a magnetization gradient. The maximum ME voltage value without a DC bias field was evaluated to be 4.2 V/cm∙Oe for an MMNPNMM (M: Metglas foil, N: nickel, P: PMN-PZT) structure, which is 625 % higher than that of conventional ME composites. Therefore, the relatively bulky means of the DC-bias application on ME materials could be eliminated, resulting in a simple ME device with a small volume using the magnetization gradient concept.

Self-Biased Bidomain LiNbO3/Ni/Metglas Magnetoelectric Current Sensor.

The article is devoted to the theoretical and experimental study of a magnetoelectric (ME) current sensor based on a gradient structure. It is known that the use of gradient structures in magnetostrictive-piezoelectric composites makes it possible to create a self-biased structure by replacing an external magnetic field with an internal one, which significantly reduces the weight, power consumption and dimensions of the device. Current sensors based on a gradient bidomain structure LiNbO3 (LN)/Ni/Metglas with the following layer thicknesses: lithium niobate—500 μm, nickel—10 μm, Metglas—29 μm, operate on a linear section of the working characteristic and do not require the bias magnetic field. The main characteristics of a contactless ME current sensor: its current range measures up to 10 A, it has a sensitivity of 0.9 V/A, its current consumption is not more than 2.5 mA, and its linearity is maintained to an accuracy of 99.8%. Some additional advantages of a bidomain lithium niobate-based current sensor are the increased sensitivity of the device due to the use of the bending mode in the electromechanical resonance region and the absence of a lead component in the device.

Magnetoelectric effect in magnetostrictive-piezoelectric composites containing magnetite nanoparticles

We report the use of nanoparticle (NP) magnetite, Fe3O4, in magnetostrictive-piezoelectric composites in trilayer laminate and single layer form. The magnetoelectric (ME) effect in both structures is highly anisotropic and linear up to 9 kOe. A trilayer laminated Fe3O4-NPs/PZT/Fe3O4-NPs composite displays the highest dc magnetic field response sensitivity, with dVME,ac/dHdc reaching 42 nV/Oe at a resonance frequency of 19.43 kHz. A slightly lower dVME,ac/dHdc of 35 nV/Oe is found for a single layer mixed composite containing Fe3O4 nanoparticles and BaTiO3 nanopowder at a resonance frequency of 0.4 kHz. The lowest ME response is observed for a single layer composite that had Fe3O4 nanoparticles and PZT powder where dVME,ac/dHdc is 1.4 nV/Oe at resonance (0.335 kHz). Our results show that composites containing Fe3O4 nanoparticles have potential applications that include wide magnetic field range vector magnetic field sensors – parallel magnetic field sensing using a trilayer configuration and perpendicular magnetic field sensing using a single layer configuration.

Electric field feedback for Magneto(elasto)Electric magnetometer development

Magneto(elasto)Electric (ME) sensors based on magnetostrictive-piezoelectric composites have been investigated to evaluate their performances to sense a magnetic signal. Previous results have shown that the dielectric loss noise in the piezoelectric layer exhibits as the dominant intrinsic noise at low frequencies, which limits the sensor performances. Also, it has intrinsically no DC capability. To avoid a part of this limitation, modulation detection methods are evaluated through a frequency up-conversion technique [1-4]. Moreover, classical magnetic field feedback techniques can be used to increase the dynamic range, the sensing stability and the system linearity, too. In this paper, we propose a new method to feedback the system by using both the magneto-capacitance modulation and an electric field feedback technique. Our development shows the feasibility of the method and the results match with the theoretical description and material properties. Even if the present results are not totally satisfactory, they give the proof of concept and yield a way for the development of very low power magnetometers.

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.

The multimodal magnetoelectric effect in the ring-shaped magnetostrictive–piezoelectric bulk composites

The theoretical and experimental investigation of the direct magnetoelectric effect in the ring-type structures made of the bulk magnetostrictive–piezoelectric composites has been presented. The analytical expression for the magnetoelectric voltage coefficient has been obtained using the effective parameters method. The frequency dependence of this parameter is also analyzed. The dependence of the resonant frequency and the amplitude of this effect of the geometrical parameters of the ring for the first and second oscillation modes are presented. The experimental investigation of the direct magnetoelectric effect for the ring-type composite specimens consisting of the nickel ferrite spinel–PZT bulk composite is done. The obtained experimental data are in good agreement with the theoretical predictions.

Uniformity of direct and converse magnetoelectric effects in magnetostrictive–piezoelectric composites

In this paper, we theoretically and experimentally confirmed the uniformity of magnetoelectric (ME) coupling coefficients for the direct and converse ME (DME and CME) effects in longitudinal-transverse (L-T) mode magnetostrictive–piezoelectric two-phase composites, both at low frequencies and in the electromechanical resonance region. We also discussed the flaws in previous measurements of the ME coupling coefficients, which led to misunderstandings in the uniformity between the DME and CME effects. Our current work provided a correct method to correctly understand ME coupling in magnetostrictive-piezoelectric two-phase composites.

Effect of magnetic domain structure on longitudinal and transverse magnetoelectric response of particulate magnetostrictive-piezoelectric composites

Phase field modeling and simulation reveal that the magnetoelectric response of particulate magnetostrictive-piezoelectric composites sensitively depends on the magnetic domain structures of magnetostrictive phase. It is found that the longitudinal and transverse magnetoelectric coefficients of particulate composites with isotropic two-phase microstructures can be effectively tailored by controlling the magnetic domain structures. It is shown that engineered magnetic domains via controlled internal residual stress through appropriate processing, such as co-sintering under external stress (rather than isostatic pressing) in analogy to stress annealing of magnetostrictive materials, provide a powerful means to optimize magnetoelectric responses of particulate composites without fabricating anisotropic two-phase microstructures (e.g., laminate, fiber/rod).

The effects of interface misfit strain and surface tension on magnetoelectric effects in layered magnetostrictive-piezoelectric composites

A nonlinear model is proposed to study low-frequency magnetoelectric (ME) effects in layered magnetostrictive-piezoelectric composites, taking into account the effects of interface misfit strain and surface stress. As a specific case, L-T mode of Terfenol-D/lead zirconate titanate (PZT) composites is investigated. The results show that flexural deformation can suppress the ME voltage coefficient, especially for elevated Terfenol-D volume fraction. Interface misfit strain demonstrates a notable impact on the ME voltage coefficient, and this strain-mediated ME effect is intensified with increasing interface misfit strain. Owing to residual surface tension, the ME voltage coefficient is found to be size-dependent when the thickness of Terfenol-D/PZT layered composite reduces to the nanoscale. In addition, substrate effect on ME voltage coefficients is evaluated.

Resonance magnetoelectric effects in a piezoelectric bimorph

Studies in recent years have focused mainly on strain mediated magnetoelectric (ME) effects in magnetostrictive-piezoelectric composites. This report is on resonance ME effects in a piezoelectric bimorph. The effect arises due to combination of piezoelectricity and the Ampere force on the sample that carries an ac electric current and placed in a bias magnetic field. The ME coefficient is as high as 16.5 V/(A kOe) at 153 Hz due to bending oscillations. Estimated ME coefficients are in agreement with the data.

Shape demagnetization effect on layered magnetoelectric composites

Magnetoelectric (ME) voltage coefficient of plate layered magnetostrictive-piezoelectric composites was always considered independent of the in-plane size due to the oversimplification in ME theoretical models. Here we report that the ME voltage coefficient depends on the in-plane size owing to shape demagnetization effect on magnetostriction. Both theoretical analysis and experimental results indicate that ME voltage coefficient of layered ME composites changes with the variation in in-plane sizes (length and width). ME coefficient increases with a rise in in-plane sizes, and different aspect ratio also results in different ME coefficients. Proper design of in-plane shape will greatly promote the develop-ment of ME devices.

Magnetoelectric effect in hybrid magnetostrictive-piezoelectric composites in the electromechanical resonance region

An expression for the description of the frequency-dependent magnetoelectric response in hybrid magnetostrictive-piezoelectric multiferroic composites is presented by using constitutive and motion equations. The calculations show that the values of the magnetoelectric voltage coefficient of the composites in the region of an electromechanical resonance sharply increase and exceed a low-frequency value by more than two orders of magnitude, which is in reasonable agreement with recent experimental data. The enhanced magnetoelectric response at the electromechanical resonance is dependent on the interface losses.