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.     

Magnetoelectric effect in multilayer ferromagnetic-piezoelectric structures and its application in electronics

Magnetoelectric effect in multilayer structures composed of magnetostrictive and piezoelectric layers, materials and technologies used to fabricate these structures, and the results of studying the magnetoelectric effect in them are considered. Magnetic field sensors, transformers, and voltage generators based on the magnetoelectric effect in multilayer structures are described.     

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.     

Electromechanical resonance in magnetoelectric layered structures

The magnetoelectric effect in layered composites has been considered in the cases of a thin rectangular plate and a thin disk under the condition that the sizes of the sample are smaller than the electromagnetic wave length. The theoretical model is based on the exact solution to the equations of motion of a medium and employs the material parameters of the initial components of the structure.     

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.     

纵向极化与磁化叠层复合材料磁电效应理论及计算

基于纵向极化压电材料及纵向磁化磁致伸缩材料的压电和压磁方程与磁电元件运动方程,给出磁电元件开路电压表达式;鉴于压电材料高输出阻抗的特点,考虑测试仪器的有限输入阻抗和传输信号引线电缆电容,通过建立等效电路模型推出了非开路情况下磁电电压计算式,取不同材料参数对磁电电压进行了数值计算.研究表明,材料参数、电路参数对输出电压均产生影响.对磁伸材料两端面受非均匀偏置磁场产生外力的非自由边界磁电效应进行研究发现,恒外力作用使压电元件产生不可检测的稳恒电压. 关键词： 纵向极化 磁电效应 磁电元件 层叠材料     

Self-sustained magnetoelectric oscillations in magnetic resonant tunneling structures

The dynamic interplay of transport, electrostatic, and magnetic effects in the resonant tunneling through ferromagnetic quantum wells is theoretically investigated. It is shown that the carrier-mediated magnetic order in the ferromagnetic region not only induces, but also takes part in intrinsic, robust, and sustainable high-frequency current oscillations over a large window of nominally steady bias voltages. This phenomenon could spawn a new class of quantum electronic devices based on ferromagnetic semiconductors.     

Nonlinear magnetoelectric effect in composite multiferroics

The theoretical and experimental studies of the nonlinear magnetoelectric effect in composite multiferroics in the low-frequency spectral region and in the electromechanical resonance region have been performed. It has been shown that such structures demonstrate a nonlinear magnetoelectric effect, which is quadratic in ac magnetic field strength at weak magnetic fields. In the region of the electromechanical resonance, the resonance excitation of an electric field occurs by means of ac magnetic field at a frequency lower than the resonance frequency by a factor of two. In the low-frequency spectral region, there is a difference of amplitude values of two neighboring voltage maxima due to the superposition of signals from the linear and nonlinear effects, and the difference is proportional to the dc magnetic field strength in weak fields. The results of the experimental study of the two-layer permendur-lead zirconate titanate structure are presented.     

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.     

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.     

Anisotropy of the magnetoelectric effect in terbium molybdate

Anisotropy of the nonlinear magnetoelectric effect in a single-crystal, single-domain sample of the β′ metastable ferroelectric paramagnetic phase of terbium molybdate Tb₂(MoO₄)₃ was studied experimentally in dc magnetic fields of up to 6 T at temperatures of 4.2 and 1.8 K. It was shown that the existing models of the magnetoelectric effect cannot explain the experimental dependences of magnetic field-induced electric polarization on the direction of the applied magnetic field. A model of the magnetoelectric effect is proposed that qualitatively describes the observed angular dependence of the magnetic field-induced electric polarization.     

Size effect study in magnetoelectric BiFeO3 system

In this paper, we report for the first time finite size effects on Néel temperature (T _N) of magnetoelectric BiFeO₃ system. Novel wet chemical route has been developed to produce fine particles of BiFeO₃ with controlled size and size distribution. Unlike other oxide systems, lattice volume contraction has been observed with decrease in particle size. The decrease in T _N is co-related to unit cell volume contraction occurring with reduction in particle size.     

Spin current and magnetoelectric effect in noncollinear magnets

A new mechanism of the magnetoelectric effect based on the spin supercurrent is theoretically presented in terms of a microscopic electronic model for noncollinear magnets. The electric polarization P(ij) produced between the two magnetic moments S(i) and S(j) is given by P proportional e(ij) X (S(i) X S(j)) with e(ij) being the unit vector connecting the sites i and j. Applications to the spiral spin structure and the gauge theoretical interpretation are discussed.     

Some properties of mis structures with a double-layer dielectric

The polarization properties of multilayer metal/silicon nitride/silicon dioxide/silicon structures have been studied. The dependence of the trapped charge in the double-layer dielectric on the magnitude and duration of the polarizing and depolarizing pulses and on the temperature is examined.Translated from Izvestiya Uchebnykh Zavedenii, Fizika, No. 4, pp. 46–50, April, 1973.     

Ultralow-frequency magnetoelectric effect in a multilayer ferrite-piezoelectric structure

The magnetoelectric effect is experimentally studied in a multilayer nickel zinc ferrite-lead zirconate titanate structure at frequencies of 10^?3–10 Hz that is placed in a harmonically modulated magnetic field of amplitude to 1 kOe. The nonlinearity of the ferrite magnetostriction and the conductivity of the films are shown to double the frequency and distort the shape of the magnetoelectric voltage. The magnetoelectric signal amplitude decreases linearly with decreasing field modulation frequency. The feasibility of using the magnetoelectric effect to detect ultralow-frequency magnetic fields is demonstrated.     

Parametric magnetoelectric effect in an AC magnetic field

Electric polarization is predicted to occur under the conditions of parametric instability of vibrations of magnetization in a longitudinal high-frequency magnetic field (parametric magnetoelectric effect). The requirements on materials are indicated favoring the observation of this effect. An example of such materials is the easy-plane antiferromagnet Cr₂TeO₆.     

Optical magnetoelectric effect in a submicron patterned magnet

The optical magnetoelectric effect, which is a nonreciprocal directional dichroic response, has been demonstrated in a submicron patterned magnet by monitoring the diffracted visible or near-infrared light intensity. An artificial magnetic superstructure is composed of chevron shaped ">" islands made of the ferromagnetic permalloy Ni(80)Fe(20) with a pitch of 1 microm on silicon substrate, in which both space inversion and time reversal symmetry are broken simultaneously. On the basis of the light-polarization angle and magnetic field H dependence, and also comparing the results with the those of the submicron square patterns, we show that the optical magnetoelectric effect emerges as the finite change (approximately 10(-3) at room temperature in H of 500 Oe) of the diffracted intensity.     

Enhancement of the magnetoelectric effect in thin ferroelectric films

The enhancement of the nonlinear magnetoelectric effect in a magnetic field is predicted for a ferroelectric film in a system consisting of ferroelectric and paraelectric layers in the vicinity of the size-induced ferroelectric phase transition. This effect is assumed to be maximum in semiconductor ferroelectrics.