高温单相多铁性材料与强磁电耦合效应

高温多铁性与强磁电耦合效应是多铁性材料研究领域的两个核心内容。文章首先介绍了已知单相多铁性材料的分类,然后简要综述了一些具有高温多铁性与强磁电耦合效应的代表性材料体系,包括螺旋磁结构六角铁氧体、电荷有序化合物、金属—有机骨架材料等。     

Nonlinear magnetoelectric interactions in composite multiferroic structures

A theory of magnetoelectric interactions in ferromagnetic-ferroelectric composite structures is presented. Resonant frequency doubling and magnetic field mixing effects in the planar structure of a lead zirconate-titanate amorphous ferromagnetic film are investigated experimentally.     

Microscopic origin of magnetoelectric coupling in noncollinear multiferroics

An universal microscopic mechanism to understand the interplay between the electric and magnetic degrees of freedom in noncollinear multiferroics is developed. In a system with a strong spin-orbit coupling, we show that there is a pure electric mechanism that the ferroelectricity is generated by noncollinear magnetism through an electric current cancellation process, which saves the pure electric energy. This mechanism provides a simple estimation and sets a physical limitation of the value of ferroelectricity in noncollinear multiferroic materials.     

Nonlinear magnetoelectric response of a bulk magnetostrictive-piezoelectric composite

Magnetoelectric effect in a bulk composite of nickel ferrite and lead zirconate titanate has been investigated by applying an ac magnetic field with no bias field. The measurements were carried out in the low-frequency region for harmonic magnetic field modulation with amplitude up to 3 kOe. The electric field induced by out-of-plane magnetic field exceeds that induced by in-plane magnetic field by approximately 4 times. Nonlinearity of ferrite magnetostriction of the sample results in a doubling in the frequency and a strong distortion of the ME signals. The magnetically induced voltage can be found by integrating the ordinary ME voltage coefficient over magnetic field.     

Low-frequency magnetoelectric effect in a Galfenol-PZT planar composite structure

The forward and inverse magnetoelectric (ME) effects are experimentally studied in a two-layer planar structure containing mechanically coupled Galfenol and PZT plates. The process of production of polycrystalline Galfenol plates and their magnetic and magnetostriction characteristics are described. For the forward ME conversion, the dependences of the amplitude of the voltage generated by the structure on the magnitude and orientation of a dc magnetic field and the frequency and amplitude of a modulating magnetic field are measured. For the inverse ME conversion, the dependences of the amplitude of the change in the magnetic induction of the structure on the dc magnetic field and the frequency of an ac electric field applied to the structure are measured. The efficiencies of the forward and inverse ME conversion are estimated for the case of low-frequency field modulation and under conditions of the resonance excitation of bending and longitudinal mechanical vibrations in the structure.     

层状磁电复合材料谐振频率下的巨磁电容效应

对三明治复合结构Tb_xDy_1-xFe_2-y/Pb(Zr, Ti)O₃/Tb_xDy_1-xFe_2-y的电容与频率及磁场的函数关系进行了实验和理论研究. 实验发现,该复合材料样品的电容随频率的增加而出现多个谐振峰,并且其谐振点随磁场的增加而发生频移. 在谐振点附近,观察到样品的阻抗随磁场的增加由容抗性转变为感抗性,从而同时观察到巨大的正磁电容效应和负磁电容效应. 由复合材料的弹性力学本构方程出发,对该类样品的电容随频率及磁场的变化进行了理论模拟. 结果显示,模拟曲线与实验结果符合得很好. 理论表明该磁致伸缩/压电复合材料的磁电容效应源于磁场诱变的铁磁相柔顺系数. 关键词： 层状复合材料 界面弹性耦合 磁电容效应     

Frequency response of magnetoelectric effect in piezoelectric-magnetostrictive disk-ring composite structures

A theoretical model is presented for frequency dependence of magnetoelectric (ME) effect in piezoelectric-magnetostrictive disk-ring composite structures. Expressions for ME voltage coefficients in piezoelectric-magnetostrictive (PE-MS) disk-ring and MS-PE disk-ring are obtained by solving elastodynamic equations. The calculated resonance frequency and frequency dependence of ME voltage coefficients are in good agreement with the experimental results. This model indicates better mechanical coupling in disk-ring structure than that in traditional layered structure, and this may be responsible for the enhancing ME effect. The analysis suggests the disk-ring composites structures are promising for magnetoelectric applications.     

On the effect of inhomogeneous magnetoelectric (flexomagnetoelectric) interaction on the spectrum and properties of magnons in multiferroics

The features of the magnon spectrum in easy-plane multiferroics (such as BiFeO₃), which allow inhomogeneous magnetoelectric (flexomagnetoelectric) interaction P[(L?)L ? LdivL], where L and P are the antiferromagnetic moment and electric polarization, respectively, have been theoretically analyzed. It has been shown that, in contrast to the magnon spectrum of a usual easy-plane antiferromagnet, a multiferroic with this magnetic structure is characterized by, first, the interaction between magnons of both branches propagating along the weak ferromagnetic moment and the appearance of a minimum (or zero) of the frequency of one of the branches, which reflects the instability of the system with respect to the transition to an inhomogeneous state with increasing flexomagnetoelectric interaction and, second, the nonequivalence (nonreciprocity) of the propagation of spin waves along and against the antiferromagnetism vector, which coincides with the toroidal moment in this system.     

Terfenol-D/PZT磁电复合材料的磁电相位移动研究

采用粘合法制备了叠层结构的块体Terfenol-D/PZT磁电复合材料,测量了不同频率下的磁电回线,采用新的极坐标下的方式做图.从极坐标下的磁电回线中可以看出,随直流磁场的变化,非谐振频率下的磁电相位发生了轻微移动,移动幅度随频率的增加而增加;而在谐振频率下,伴随着巨磁电效应,磁电相位发生了显著移动,移动幅度达到了近90°.与粉末Terfenol-D/环氧树脂/PZT磁电复合材料对比之后表明,非谐振频率下块体Terfenol-D/PZT的磁电相位移动主要由涡流引起;而谐振频率下大幅度相位移动则主要来源于Terfenol-D的磁致弹性变化.     

Room-temperature giant magnetotranstance effect in single-phase multiferroics

Single-phase multiferroic materials are usually considered useless because of the weak magnetoelectric effects,low operating temperature,and small electric polarization induced by magnetic orders.As a result,current studies on applications of the magnetoelectric effects are mainly focusing on multiferroic heterostructures and composites.Here we report a room-temperature giant effect in response to external magnetic fields in single-phase multiferroics.A low magnetic field of 1000 Oe applied on the spin-driven multiferroic hexaferrites BaSrCo_2 Fe_(11)AlO_(22) and Ba_(0.9)Sr_(1.1)Co_2 Fe_(11)AlO_(22) is able to cause a huge change in the linear magnetoelectric coefficient(α_E=dE/dH) by several orders,leading to a giant magnetotranstance(GMT) effect at room temperature.The GMT effect is comparable to the well-known giant magnetoresistance(GMR) effect in magnetic multilayers,and thus opens up a door toward practical applications for single-phase multiferroics.     

Investigation of magnetostrictive/piezoelectric multilayer composite with a giant zero-biased magnetoelectric effect

In this paper, we investigate the resonance magnetoelectric (ME) effect in the middle supported multilayer composites consisting of high-permeability Fe-based nanocrystalline soft magnetic alloy Fe_73.5Cu₁Nb₃Si_13.5B₉ (FeCuNbSiB), Nickel (Ni), and piezoelectric Pb(Zr_1?x Ti _x )O₃ (PZT). The coupling effect between positive magnetostrictive FeCuNbSiB and negative magnetostrictive Ni results in the build-in magnetic bias due to their different magnetic permeability and coercivity. As a result, a giant resonance ME voltage coefficient (α _ME,r ) at zero DC magnetic bias field (H _dc) and multi-peaks of α _ME,r for FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB composite are observed. The experimental results show that the giant zero-biased α _ME,r strongly depends on the thickness of FeCuNbSiB ribbon. The maximum zero-biased α _ME,r is up to 86 V/cm?Oe for FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB with four-layer FeCuNbSiB ribbons, which is ～500 times higher than that of the previously reported NKNLS-NZF/Ni/NKNLS-NZF trilayer composite. Compared with the peak α _ME,r and the optimum H _dc of Ni/PZT/Ni composite, the largest peak α _ME,r of FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB composite with four-layer FeCuNbSiB ribbons increases ～185 %, and the optimum H _dc decreases ～300 Oe, respectively. Based on the nonlinear magnetostrictive constitutive relation and the magnetoelectric equivalent circuit, a theoretical model of α _ME,r versus H _dc is built under free boundary conditions. Calculated zero-biased α _ME,r and α _ME,r versus H _dc are in good agreement with the experimental data. This laminate composite shows promising applications for high-sensitivity power-free magnetic field sensors, zero-biased ME transducers and small-size energy harvesters.     

Temperature characteristics of magnetoelectric interaction in langatate-ferromagnet composite resonators

Magnetoelectric interaction in a layered langatate-hysteretic ferromagnet structure is observed with no bias magnetic field applied. The temperature characteristics of interaction are determined mainly by the properties of the ferromagnetic layer. Raising the temperature weakens the coupling between layers and lowers the efficiency of interaction.     

Heterogeneous multiferroics: Magnetoelectricity and piezoelectric effect

Physics of the Solid State - The concentration and frequency dependences of the effective magnetoelectric, dielectric, piezoelectric, and piezomagnetic constants of two-dimensional conducting...     

Dynamic magnetoelectric effect in terbium molybdate

The electric polarization induced in ferroelectric terbium molybdate by a magnetic field linearly varying with time is measured. The measurements are performed in fields up to 19 T at different specified rates of change in the magnetic field at temperatures of 273 and 219 K. The results obtained indicate that there are magnetoelectric effects of two types. One of them is a conventional magnetoelectric effect, which is appropriately referred to as the static magnetoelectric effect. The other effect is characterized by the fact that the electric polarization increases with an increase in the rate of change in the magnetic field and relaxes with time to zero at a fixed nonzero field. This phenomenon is termed the dynamic magnetoelectric effect.     

FeCuNbSiB对FeNi/PZT复合结构磁电效应的影响

构造了FeCuNbSiB/FeNi/PZT磁电复合结构并与FeNi/PZT复合结构进行了对比研究.分析了高磁导率材料FeCuNbSiB对FeNi磁场的影响机理,研究了FeCuNbSiB/FeNi/PZT三相复合结构的磁电效应.实验表明,在FeNi/PZT两相层合结构中黏接FeCuNbSiB层后:1)最优偏置磁场从200 Oe降低到55 Oe,最大谐振磁电电压系数从1.59 V/Oe增大到2.77 V/Oe;2)在低偏置磁场中,层合结构磁电电压转换系数提高了1.7—7.8倍;3)层合结构的磁电电压对静态磁场 关键词： 层合结构 最优偏置磁场 高磁导率 磁电电压转换系数     

Nonlinear magnetoelectric effects in an isotropic disordered dielectric in nonuniform fields

Theoretical analysis allowing experimental observation of nonlinear magnetoelectric effects in isotropic disordered dielectric in nonuniform electric and magnetic fields is carried out.     

Temperature behavior of magnetoelectric interaction in composite PZT-nickel disk resonators

The temperature dependences of the characteristics of magnetoelectric interaction in composite disk resonators made up of Ni and PZT layers are studied. Measurements are taken on monolithic resonators, prepared by electrolytic deposition of Ni on PZT, and resonators prepared by gluing Ni and PZT layers. In the temperature interval 220–380 K, the frequency of the monolithic resonators changes by up to 16% and that of the glued resonators, by 4.5%. It is shown that the efficiency of magnetoelectric interaction declines with increasing temperature, since (i) the piezoelectric modulus and piezomagnetic coefficient of the layers vary, (ii) the PZT permittivity rises, and (iii) the layer-to-layer adhesion weakens due to softening of the glue. The results can be used in developing techniques for stabilizing the magnetoelectric interaction characteristics of composite structures.     

Surface magnetoelectric effect in ferromagnetic metal films

A surface magnetoelectric effect is revealed by density-functional calculations that are applied to ferromagnetic Fe(001), Ni(001), and Co(0001) films in the presence of an external electric field. The effect originates from spin-dependent screening of the electric field which leads to notable changes in the surface magnetization and the surface magnetocrystalline anisotropy. These results are of considerable interest in the area of electrically controlled magnetism and magnetoelectric phenomena.     

Theory of magnetoelectric effect in double-layer ferromagnetic-piezoelectric structures

A theory of magnetoelectric effect in double-layer ferromagnetic-piezoelectric plate-shape structures is presented. Using the material and motion of continuum equations, an expression for the magnetic coefficient is derived in terms of the parameters characterizing the magnetic and piezoelectric phases. It is shown that in the region of electromagnetic resonance there is a considerable increase in the magnetoelectric coefficient value. A relationship is obtained between the ferromagnetic and piezoelectric thicknesses for which the magnetoelectric coefficient is maximal. The coefficients calculated for the structures based on permendure — plumbum zirconate-titanate are given, and the results of calculations are compared to the experimental data.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 3–6, December 2004.     

偏置磁场对磁致伸缩/弹性/压电层合材料磁电效应的影响

根据磁致伸缩材料的非线性本构关系得到其动态杨氏弹性模量和动态压磁系数,结合等效电路法得到磁致伸缩/弹性/压电层合材料的磁电效应与磁致伸缩材料的动态杨氏弹性模量和动态压磁系数的关系,讨论了偏置磁场对这种层合材料的谐振频率和谐振磁电电压转换系数的影响.理论推导和实验结果均表明,存在最佳偏置磁场使磁致伸缩/弹性/压电层合材料的谐振磁电电压转换系数最大. 关键词： 磁致伸缩/弹性/压电层合材料 磁电效应 偏置磁场 非线性本构关系