Effective Piezomagnetic Coefficient Research Articles

Fabrication, Modeling and Characterization of Magnetostrictive Short Fiber Composites.

Magnetostrictive materials have a wide variety of applications due to their great capability as sensors and energy-harvesting devices. However, their brittleness inhibits their applications as magnetostrictive devices. Recently, we developed a continuous magnetostrictive Fe-Co-fiber-embedded epoxy matrix composite to increase the flexibility of the material. In this study, we fabricated random magnetostrictive Fe-Co short fiber/epoxy composite sheets. It was found that the discontinuous Fe-Co fiber composite sheet has the magnetostrictive properties along the orientation parallel to the length of the sheet. Finite element computations were also carried out using a coupled magneto-mechanical model, for the representative volume element (RVE) of unidirectional aligned magnetostrictive short fiber composites. A simple model of two-dimensional, randomly oriented, magnetostrictive short fiber composites was then proposed and the effective piezomagnetic coefficient was determined. It was shown that the present model is very accurate yet relatively simple to predict the piezomagnetic coefficient of magnetostrictive short fiber composites. This magnetostrictive composite sheet is expected to be used as a flexible smart material.

Enhanced piezomagnetic coefficient of cobalt ferrite ceramics by Ga and Mn doping for magnetoelectric applications

The magnetic, magnetostrictive, and electrical properties of Ga- and Mn-doped cobalt ferrite are reported as a function of composition. Materials with improved functionality for magnetoelectric composites are obtained. Magnetic characterizations reveal the effectiveness of the dopants to reduce the typically high magneto-crystalline anisotropy of cobalt ferrite and significantly enhance piezomagnetic coefficients. CoGa0.15Fe1.85O4 ceramic shows large effective piezomagnetic coefficient q11, 3.9 × 10−6 kA−1 m, which is among the highest values reported for cobalt ferrite-based ceramics. Additionally, a two order of magnitude increase of resistivity is found after doping, which makes this material specially suitable for particulate composites. On the contrary, CoMn0.25Fe1.75O4 ceramic has the highest value of q11+q21 (∼1.9 × 10−6 kA−1 m), which is the relevant parameter for laminated composites. Analytical calculations of the transverse magnetoelectric coefficient α31E for bilayers containing these optimized magnetostrictive phases are also reported, and they demonstrate their high potential for developing new magnetoelectric composites.

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.

Self-biased magnetoelectric coupling characteristics of three-phase composite transducers with nanocrystallin soft magnetic alloy

This paper reports the self-biased magnetoelectric (ME) effects in composites consisting of high-permeability Fe-based nanocrystalline soft magnetic alloy Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB), pure nickel (Ni) and piezoelectric lead zirconate titanate (PZT). The FeCuNbSiB ribbons are fabricated on traditional laminates Ni/PZT/Ni through two modes: the attached mode (F–NPN–F) and the laminated mode (F/NPN/F). The F–NPN–F composite sufficiently reveals that the high-permeability FeCuNbSiB ribbons concentrate more magnetic flux in magnetostrictive Ni, which results in the self-biased ME effects of F–NPN–F. For the F/NPN/F composite, the FeCuNbSiB acts as the dynamic driver to enhance the effective piezomagnetic coefficient of Ni. The giant self-biased ME effects of F/NPN/F are because of the internal magnetic field between Ni and FeCuNbSiB due to their different magnetic characteristics. The influences of the numbers of FeCuNbSiB layers (L) on the resonant ME voltage coefficients (α ME,r ) for F–NPN–F and F/NPN/F composites are investigated in detail. The experiments demonstrate that the maximum α ME,r at zero-biased field is 80 V/cm Oe for F–NPN–F with L = 2, and 85 V/cm Oe for F/NPN/F with L = 4. This paper demonstrates that these two ME composites are suitable for achieving zero-biased ME transducers, power-free magnetic field sensors and energy harvesters.

Ferroelectric-ferromagnetic multilayers: A magnetoelectric heterostructure with high output charge signal

Multiferroic composites and heterostructures comprising ferroelectric and ferromagnetic materials exhibit room-temperature magnetoelectric (ME) effects greatly exceeding those of single-phase magnetoelectrics known to date. Since these effects are mediated by the interfacial coupling between ferroic constituents, the ME responses may be enhanced by increasing the density of interfaces and improving their quality. A promising material system providing these features is a ferroelectric-ferromagnetic multilayer with epitaxial interfaces. In this paper, we describe theoretically the strain-mediated direct ME effect exhibited by free-standing multilayers composed of single-crystalline ferroelectric nanolayers interleaved by conducting ferromagnetic slabs. Using a nonlinear thermodynamic approach allowing for specific mechanical boundary conditions of the problem, we first calculate the polarization states and dielectric properties of ferroelectric nanolayers in dependence on the lattice mismatch between ferroic constituents and their volume fractions. In these calculations, the ferromagnetic component is described by a model which combines linear elastic behavior with magnetic-field-dependent lattice parameters. Then the quasistatic ME polarization and voltage coefficients are evaluated using the theoretical strain sensitivity of ferroelectric polarization and measured effective piezomagnetic coefficients of ferromagnets. For Pb(Zr0.5Ti0.5)O3−FeGaB and BaTiO3−FeGaB multilayers, the ME coefficients are calculated numerically as a function of the FeGaB volume fraction and used to evaluate the output charge and voltage signals. It is shown that the multilayer geometry of a ferroelectric-ferromagnetic nanocomposite opens the way for a drastic enhancement of the output charge signal. This feature makes biferroic multilayers advantageous for the development of ultrasensitive magnetic-field sensors for technical and biomedical applications.

Magnetoelectric coupling characteristics of five-phase laminate composite transducers based on nanocrystalline soft magnetic alloy

A five-phase laminate composite transducer based on nanocrystalline soft magnetic FeCuNbSiB alloy is presented, whose magnetoelectric (ME) coupling characteristics have been investigated. It is found that the resonant ME voltage coefficient of FeCuNbSiB/Terfenol-D/Pb(Zr1-x,Tix)O3 (PZT)/Terfenol-D/FeCuNbSiB (FMPMF) five-phase transducer is much larger than that of traditional Terfenol-D/PZT/Terfenol-D (MPM) transducer, resulting from the enhancement of the effective mechanical quality factor and effective piezomagnetic coefficient of the transducers. Appropriate FeCuNbSiB layer thickness is propitious to the resonant and low-frequency ME coupling characteristics. The maximum resonant ME voltage coefficient achieves 4.81 V/Oe with FeCuNbSiB layer thickness is 60 μm under the DC bias magnetic field Hb = 77 Oe, which is 1.48 times as great as that of traditional MPM transducer. In addition, the maximum ME voltage coefficient at low frequency is 51.2 mV/Oe under the DC bias magnetic field Hb = 442 Oe, which is 1.26 times as great as that of traditional MPM transducer. It indicates that the mentioned five-phase laminate composite transducers have great potential for the application of highly sensitive dc magnetic field sensing and vibration energy harvesting.

Enhanced magnetoelectric effects in composite of piezoelectric ceramics, rare-earth iron alloys, and shape-optimized nanocrystalline alloys

An enhancement for magnetoelectric (ME) effects is studied in a three-phase ME architecture consisting of two magnetostrictive Terfenol-D (Tb(0.3)Dy(0.7)Fe(1.92)) plates, a piezoelectric PZT (Pb(Zr,Ti)O3) plate, and a pair of shape-optimized FeCuNbSiB nanocrystalline alloys. By modifying the conventional shape of the magnetic flux concentrator, the shape-optimized flux concentrator has an improved effective permeability (μ(eff)) due to the shape-induced demagnetizing effect at its end surface. The flux concentrator concentrates and amplifies the external magnetic flux into Terfenol-D plate by means of changing its internal flux concentrating manner. Consequently, more flux lines can be uniformly concentrated into Terfenol-D plates. The effective piezomagnetic coefficients (d(33m)) of Terfenol-D plate and the ME voltage coefficients (α(ME)) can be further improved under a lower magnetic bias field. The dynamic magneto-elastic properties and the effective magnetic induction of Terfenol-D are taken into account to derive the enhanced effective ME voltage coefficients (α(ME,eff)), the consistency of experimental results and theoretical analyses verifies this enhancement. The experimental results demonstrate that the maximum d(33m) in our proposed architecture achieves 22.48 nm/A under a bias of 114 Oe. The maximum α(ME) in the bias magnetic range 0-900 Oe reaches 84.73 mV/Oe under the low frequency of 1 kHz, and 2.996 V/Oe under the resonance frequency of 102.3 kHz, respectively. It exhibits a 1.43 times larger piezomagnetic coefficient and a 1.87 times higher ME voltage coefficient under a smaller magnetic bias of 82 Oe than those of a conventional Terfenol-D/PZT/Terfenol-D composite. These shape-induced magnetoelectric behaviors provide the possibility of using this ME architecture in ultra-sensitive magnetic sensors.

Magnetoelectric Transducer Employing Piezoelectric Ceramic/Ferromagnetic Alloy/High-Permeability FeCuNbSiB Composite

This feature of rather large magnetoelectric (ME) coupling at the resonance enables the ME composites to possess great ME energy conversion ability. This paper proposes a new type of ME transducer fabricated from the ferromagnetic alloy FeNi-FACE, high-permeability FeCuNbSiB (Fe73.5Cu1Nb3Si13.5B9) and piezoelectric PZT-8H to achieve the strong ME coupling. On one hand, the effective mechanical quality factor (Qm) of the transducer is significantly high because of the high quality factor values of FeNi-FACE, PZT-8H and FeCuNbSiB respectively. On the other hand, FeCuNbSiB acts as the dynamic driver to enhance the effective piezomagnetic coefficient d33 of the FeNi-FACE. A high ME voltage coefficient (MEVC) and a high ME power output can be obtained since the MEVC and power output at resonance strongly depend on the d33 and the Qm. The experimental results show that the strain coefficient of the FeNi-FACE/FeCuNbSiB laminate at resonance achieves 250 nm/A under Hdc = 23 Oe, which is 6.02 times as high as that for a single FeNi-FACE layer. The maximum MEVC at resonance (αr) achieves 4.65 V/Oe, which is 1.6 times larger than that of the previous Terfenol-D/PZT/Terfenol-D (MPM) composite transducer. The new transducer can obtain an output power of 103.7 μW under a resonant excitation Hac = 0.4 Oe, which is ~16 times higher than that of the previous ultrasonic-horn-substrate composite transducer and decreases the size by nearly 75%.

High sensitivity magnetic sensor consisting of ferromagnetic alloy, piezoelectric ceramic and high-permeability FeCuNbSiB

A high sensitivity magnetoelectric (ME) composite sensor employing a type of ferromagnetic constant-elasticity alloy (FeNi-FACE), piezoelectric Pb(Zr,Ti)O 3 (PZT-8H) and high-permeability FeCuNbSiB (Fe 73.5Cu 1Nb 3Si 13.5B 9) is developed. The FeCuNbSiB ribbon with the high permeability serves as the dynamic driver to increase the effective piezomagnetic coefficient d 33 of the FeNi-FACE. At the same time, the FeCuNbSiB/FeNi-FACE/PZT-8H/FeNi-FACE/FeCuNbSiB (FeFPFFe) composite sensor exhibits a higher effective mechanical quality factor ( Q m), which is ∼7.7 times higher than that of Terfenol-D/PZT-8H/Terfenol-D (MPM) sensor. As the ME voltage at resonance is directly proportional to the product of piezomagnetic coefficient and Q m, a stronger ME effect can be achieved. The experimental results show that the resonance ME voltage coefficient (MEVC) of the FeFPFFe sensor at H dc = 119 Oe achieves 4.367 V/Oe, which is ∼1.41 times higher than that of FeNi-FACE/PZT-8H/FeNi-FACE (FPF) sensor. Furthermore, ∂ V ME / ∂ H dc for the FeFPFFe sensor achieves ∼22.5 m V/Oe at H dc = 31 Oe under resonant drive conditions of H ac = 0.1 Oe, which is ∼20 times higher than that of the previous reported Terfenol-D/Pb(Zr,Ti)O 3/Terfenol-D composite transducer. Thus the FeFPFFe sensor has highly sensitive ac or dc magnetic field sensing.