Theory of the magnetoelectric effect in ferromagnetic-piezoelectric heterostructures

A theory of the magnetoelectric effect in ferromagnetic-piezoelectric bilayer structures is considered for platelike samples. The magnetoelectric voltage coefficient is expressed through the parameters characterizing the magnetic and piezoelectric phases. It is shown that the magnetoelectric voltage coefficient considerably increases in the region of electromechanical resonance. The thickness ratio between the ferromagnetic and piezoelectric phases at which the magnetoelectric voltage coefficient is maximum is determined. The calculated magnetoelectric voltage coefficients for Permendur-PZT (lead zirconate titanate) structures are presented and compared with the experimental data.     

基于能量转换原理的磁电层合材料低频磁电响应分析

提出了一种基于能量转换原理的磁致伸缩/压电层合材料低频磁电响应模型,并对不同层合结构的磁电响应特性进行了对比研究.该模型假定层合材料层间能量传递通过层间剪切力来实现,利用应力函数法分析了磁致伸缩层和压电层的应力与应变,求出了磁致伸缩层的应变能和存储磁场能以及压电层的应变能和电场能;利用Hamilton最小能量原理求出了层间剪切力的大小,获得了开路状态下层合材料的低频磁电响应模型.发现磁电电压系数与磁致伸缩材料的磁导率、泊松比、磁机耦合系数以及压电材料的泊松比、机电耦合系数等有关,并对这些参数的影响进行了分析.同时对两层和三层结构的层合材料磁电特性进行了对比研究,发现层合结构不同则获得的磁电系数公式不同,用相应的公式计算得到的误差才会最小.研究结果表明,本文的理论误差小于6.5%,与其他方法相比,本文的理论模型能更好地描述磁电层合材料的低频磁电响应特性.     

Magnetoelectric effect from the direct coupling of the Lorentz force from a brass ring with transverse piezoelectricity in a lead zirconate titanate (PZT) disk

A novel composite of brass ring and PZT disk shows a high dc magnetic field (H_dc) response when using the product effect of the Lorentz force effect from a metal ring in a dc magnetic field applied with ac electrical current, and the piezoelectric effect of piezoelectric material. The output voltage between the two faces of PZT shows a good linear response to the dc magnetic field (<1 kOe) under different ac electrical current inputs (<300 mA). The magnetoelectric coefficient is about ∼33.2 mV/T A. Simultaneously, the magnitude of its magnetoelectric coefficient can be manually controlled by an applied electrical current. This composite has the potential for applications in magnetoelectric transducers and sensors that work without coils even for static magnetic fields. PACS 85.80.Jm; 77.84.-S; 75.80.+q; 77.84.Dy; 77.65.-j     

Magnetoelectric effect in an asymmetric layered magnet-piezoelectric structure

The magnetoelectric effect in magnet-piezoelectric layered composite structures is discussed. The magnetoelectric voltage and the magnetoelectric coefficient are calculated taking into account bending deformations that accompany tensile and compressive strains in structures with asymmetric positions of magnetic layers relative to the neutral plane. It is demonstrated that bending deformations lead to a nonuniform distribution of the electric field over the thickness of the piezoelectric layer and to a nonmonotonic dependence of the magnetoelectric coefficient on the thickness ratio of the layers in the structure.     

偏置电压对磁致伸缩/压电层合换能结构磁电性能影响

分析和测试了偏置电压调整时PZT5/Terfenol-D/PZT8层合换能结构磁电性能. 提出了一种磁致伸缩/压电层合磁电换能结构的一阶谐振频率控制方法. 通过改变压电驱动层的直流电压对磁电层合结构的预应变进行改变, 从而调整谐振频率. 分析偏置电压、 应变、 弹性模量、 谐振频率和谐振磁电电压系数之间关系. 分析表明: 在较小应变情况下, 控制电压几乎可以线性调节谐振频率, 而层合结构谐振磁电电压系数几乎与偏置电压无关. 实验研究验证: 理论与实验结果较好吻合. 在-170 V-+170 V的偏置电压时, 谐振频率可以几乎线性调整. 最大频率调整量达到1 kHz, 偏置电压对一阶纵振频率的控制率达到: 2.94 Hz/V. 在偏置磁场为0-225 Oe时, 谐振频率调整量与偏置磁场无关. 偏置磁场会改变谐振磁电电压系数, 在大于178 Oe静态磁场偏置时, 磁电电压系数最大, 达到1.65 V/Oe.     

A theory of the inverse magnetoelectric effect in layered magnetostrictive–piezoelectric structures

A theory of the inverse magnetoelectric effect in layered structures has been presented. The theory is based on solving the equations of elastodynamics and electrostatics separately for the magnetostrictive and piezoelectric phases, taking into account the conditions at the interface between the phases. Expressions for the coefficient of inverse magnetoelectric conversion through the parameters characterizing the magnetostrictive and piezoelectric phases have been obtained. Theoretical dependences of the inverse magnetoelectric conversion coefficient on the frequency of the alternating-current electric field for the three-layer PZT–Ni–PZT structure and the two-layer terfenol-D–PZT structure have been calculated. The results of the calculations are in good agreement with the experimental data.     

磁致伸缩/压电层叠复合材料磁电效应分析

采用有限元分析软件COMSOL5.0建立了三维悬臂梁模型,分析了磁致伸缩/压电/磁致伸缩叠层复合材料的磁电系数α_(ME),并就几何参数对复合结构磁电系数的影响进行了优化分析.首先,利用稳态求解器研究了磁电层状复合结构内部的应力、应变、位移以及电势分布情况,利用瞬态求解分析了磁电复合结构各变量动态分布规律;其次,应用小信号频域分析研究了该结构的谐振频率以及在不同偏置磁场对输出电压的影响,结果表明,随着直流偏置磁场的增加,输出电压逐渐减小.改变复合材料不同层的厚度,分析了磁电层与压电层厚度比t_m/t_p对磁电系数的影响,结果表明,随着厚度比增加,α_(ME)逐渐增大,其增加速率逐渐减小;最后,分析了磁电系数α_(ME)随复合结构面积、长宽比的变化情况.分析表明,α_(ME)随磁电复合结构面积的增加逐渐增加,其增加速率逐渐减小;当磁电复合结构面积恒定时,其磁电系数随长宽比L/W增加表现出先增加后减小的趋势,存在最优值.     

高磁导率材料FeCuNbSiB对超磁致伸缩/压电层合材料磁电性能的影响

采用超磁致伸缩材料TbxDy_1-xFe₂(x≈0.3)(Terfenol-D)、压电材料PbZrxTi_1-xO₃(PZT)和高磁导率材料FeCuNbSiB构造了新型的层合结构.由于引入高磁导率材料FeCuNbSiB改变了Terfenol-D的内部磁场分布,并且在磁场作用下,FeCuNbSiB发生形变对Terfenol-D产生应力,增大了Terfeno 关键词： 磁电效应 磁致伸缩材料 压电材料 高磁导率材料     

Frequency dependence of the magnetoelectric effect in a magnetostrictive-piezoelectric heterostructure

The frequency dependence of the magnetoelectric effect in a magnetostrictive-piezoelectric heterostructure is theoretically studied by solving combined magnetic, elastic, and electric equations with boundary conditions. Both the mechanical coupling coefficient and the losses of the magnetostrictive and piezoelectric phases are taken into account. The numerical result indicates that the magnetoelectric coefficient and the resonance frequency are determined by the mechanical coupling coefficient, losses, and geometric parameters. Moreover, at the electromechanical resonance frequency, the module of the magnetoelectric coefficient is mostly contributed by the imaginary part. The relationship between the real and the imaginary parts of the magnetoelectric coefficient fit well to the Cole-Cole circle. The magnetostrictive-piezoelectric heterostructure has a great potential application as miniature and no-secondary coil solid-state transformers.     

Magnetoelectric effect and magnetostriction in the paramagnetic piezoelectric NiSO4 · 6H2O

The direct magnetoelectric effect, the magnetostriction, and the magnetic moment in piezoelectric paramagnetic NiSO₄ · 6H₂O single crystals is comprehensively studied over a wide temperature range in magnetic fields up to 14 T for several magnetic field directions with respect to crystallographic axes. At temperatures above 20 K, the magnetoelectric effect is rigorously quadratic in magnetic field over the entire magnetic field range. As the temperature decreases, the region of quadratic behavior shifts toward low fields. To explain the magnetoelectric effect, the contribution of the magnetostriction-induced piezoelectric effect is considered. It is shown that the piezoelectric effect may be neglected at the helium temperature, where the magnetoelectric effect is high, since its value does not exceed 1%. However, the relative contribution of the piezoelectric effect increases to 10% at T = 40 K, where the magnetoelectric polarization decreases strongly. In contrast to the earlier assumption that the magnetoelectric effect is rapidly and fully saturated in fields higher than 3 T, complete saturation is actually not detected even at 14 T.     

铁电/铁磁三相颗粒复合材料的磁电性能计算

采用格林函数方法给出了三相复合材料的磁电系数的解析式，对稀土-铁合金/压电陶瓷/高分子（Terfenol-D/PZT/PVDF）三相颗粒复合材料的磁电系数进行了计算.计算结果给出了复合材料的磁电性能与材料显微结构的关系，包括三相颗粒复合材料的磁电性能随组分、颗粒的长径比、PZT颗粒的电极化方向以及外磁场的变化趋势，可为实验设计提供参考和指导.通过合理设计，三相磁电复合材料的性能可以达到数百mV/A.作为一种新的磁电复合材料，三相颗粒复合材料有望成为一种新型高性能易制备的磁电材料. 关键词： 磁电效应 复合材料 格林函数     

Studies on lead-free multiferroic magnetoelectric composites

Lead-free multiferroic magnetoelectric composites consisting of ferrimagnetic Ni_0.93Co_0.02Mn_0.05Fe_1.95O₄ (NMF) and ferroelectric Na_0.5Bi_0.5TiO₃ (NBT) phases were synthesized by the solid-state sintering method. The presence of constituent phases in composites was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A systematic study of dc conductivity as a function of temperature (RT −450 °C) revealed that the conduction is due to small polarons. The effect of constituent phase variation on the dielectric constant and piezoelectric strength (d₃₃) was examined. The composites exhibited typical magnetic hysteresis (M–H) loops at room temperature. Furthermore, magnetoelectric (ME) output was evaluated as a function of applied magnetic field, which is a product property of the constituent phases. The compound 50% NMF–50%NBT is a new lead-free magnetoelectric composite with 155 μV/cm ME output, which may have potential applications.     

Magnetoelectric effect in bilayer magnetostrictive-piezoelectric structure. Theory and experiment

Bilayer magnetostrictive-piezoelectric structures have certain advantages compared to bulk composites and this allows us to consider them as perspective materials for the development of devices based on the magnetoelectric effect. The theory of magnetoelectric effect in bilayer magnetostrictive-piezoelectric structure is presented taking into account the thickness dependence amplitude of the mechanical oscillations for the structures in form of rectangular plate. The equation for frequency dependence of the ME effect in the region on the electromechanical resonance was obtained, using motion equation, elastodynamics and electrostatic equations for the magnetostrictive, piezoelectric phases and taking into account the boundary conditions on the interface. The cases of longitudinal and transverse orientations of the electric and magnetic fields were considered. It is shown that the thickness dependence of the ME voltage coefficient has the maximum. The dependence between frequency and the thickness ratio of the layers is presented for both the theory and experiment.     

Influence of layer-to-layer electric and magnetic interactions on a magnetoelectric coefficient at high frequencies

We analyze the influence of electric and magnetic interconnection between the components of a magnetoelectric on its magnetoelectric coefficient at high frequency of the external electric and magnetic field. We interpret the obtained results on the basis of the existence in such structures of probing electromagnetic fields. It is shown that allowing for electric and magnetic field capture through the mechanical subsystem leads to a decrease in the magnetoelectric coefficient.     

The physics of magnetoelectric composites

This paper gives an overview about the basic ideas of magnetoelectric materials. Up to now single-phase materials show the magnetoelectric effect only below room temperature. Mixing a magnetostrictive with a piezoelectric component is a way to overcome this limitation. This delivers a composite which can exhibit a magnetoelectric effect even at room temperature and higher. Possible candidates for these composites (piezoelectric as well as magnetostrictive) are shown, examples from literature and own results are given. The most important coupling mechanism (magnetization, magnetostriction, local stress, charge) between the magnetostrictive and the piezoelectric phase are discussed. Hints for a direct coupling between the electric polarization and the magnetization are also presented. Different measurement methods for determining the magnetoelectric coefficient are discussed. Representative results as obtained on a technical useful composite between 50% Co-Ferrite+50% BaTiO₃ are given. The behavior of a simple “mixed” structure with that of a “core-shell” structure is compared. The later gives a 20-times larger magnetoelectric coefficient.     

Low-frequency magnetic energy harvest using multiferroic composite plates

It is shown with a theoretical bending model that a laminated plate with piezoelectric and piezomagnetic layers can be used to harvest magnetic energy at relatively low frequencies. The output electric power and the energy conversion efficiency are calculated. The load dependence of the magnetoelectric coupling coefficient is obtained.     

有限输入阻抗下压电/磁伸层叠材料磁电效应理论及实验

将磁致伸缩材料及压电材料本构方程与运动方程结合,考虑压电材料具有的高输出阻抗的特点及测试设备的有限输入阻抗和传输信号引线电容对磁电效应输出电压的影响,推出了Terfenol-D巨磁伸材料与横向极化Pb(Zr_1-xTi_x)O₃压电材料的磁电效应理论,研制了由一维磁伸材料构成的三明治结构元件并对其性能进行了测试,采用考虑了测试系统有限输入阻抗后建立的磁电效应理论结果与实验结果更符合.理论结果表明磁电元件在有限输入阻抗 关键词： 磁电效应 有限输入阻抗 压电/磁伸复合 一维磁伸材料     

Magnetoelectric effect in amorphous FeNiSiC ferromagnet-piezoelectric planar structures

The magnetoelectric (ME) effect is studied in composite two- and three-layer disk structures containing magnetostriction layers of an amorphous FeNiSiC ferromagnet and a lead zirconate titanate piezoelectric layer. Due to a high magnetostriction (∼33 × 10⁻⁶) and a low saturation field (∼200 Oe), an FeNiSiC layer has a high piezomagentic coefficient, which results in an effective ME coupling in low fields (∼25 Oe). The ME effect is ∼0.2 V cm⁻¹ Oe⁻¹ at a low frequency and increases to 11.9 and 13.2 V cm⁻¹ Oe⁻¹ when bending and in-plane mechanical vibrations are excited in a resonance manner in the structures at frequencies of ∼8.2 and ∼170.0 kHz, respectively. Structures containing amorphous FeNiSiC layers are promising for magnetic field transducers and electric energy generators and converters.     

磁电异质结及器件应用

磁电异质结是由铁磁和铁电材料通过连接层耦合而成,其磁电效应来源于铁电相的压电效应和铁磁相的磁致伸缩效应.相对于颗粒混相磁电复合材料,层状磁电异质结材料具有更高的磁电耦合系数和更低的介电损耗,使得其在磁场传感器、能量收集器、天线以及存储器等领域都有着巨大的应用前景.本综述重点总结了磁电异质结材料的发展历程以及相关应用领域的最新进展,最后评述了磁电异质结材料发展的挑战和前景展望.