Static Magnetoelectric Effect Research Articles

Identification of Antiferromagnetic Domains Via the Optical Magnetoelectric Effect.

The ultimate goal of multiferroic research is the development of a new-generation nonvolatile memory devices, where magnetic bits are controlled via electric fields with low energy consumption. Here, we demonstrate the optical identification of magnetoelectric (ME) antiferromagnetic (AFM) domains in the LiCoPO_{4} exploiting the strong absorption difference between the domains. This unusual contrast, also present in zero magnetic field, is attributed to the dynamic ME effect of the spin-wave excitations, as confirmed by our microscopic model, which also captures the characteristics of the observed static ME effect. The control and the optical readout of AFM/ME domains, demonstrated here, will likely promote the development of ME and spintronic devices based on AFM insulators.

Modeling of Magnetoelectric Effects in Magnetostrictive/Piezoelectric Laminated Composites Using the Energy Method

The current models of the resonant magnetoelectric (ME) effect are based on Newton’s equation of motion and some given conditions which are various in published papers. Even some results are in conflict with Gauss’s law in magnetics. This paper provides the energy method to model ME effects. The energy method is based on linear constitutive equations and the principle of minimum energy. By constructing and solving the constraint problem of the variational principle, more reasonable conditions are deduced for simplifying Newton’s motion equation. The induced additional fields of externally applied fields are considered during the process of deducing by Gauss’s law for electricity or magnetism. The coefficients of direct/converse ME effects are obtained and compared with the models in the previous papers. The proposed model avoids conflict with Gauss’s law and provides another insight into understanding the resonant and static ME effects.

Enhancing magnetoelectric effect in multiferroic composite bilayers via flexoelectricity

We employ the flexoelectricity to enhance the magnetoelectric (ME) (coupling) effect in multiferroic (MF) composites and structures. An analytical model is presented to predict the ME effect in a MF composite bilayer consisting of piezomagnetic and piezoelectric layers. The flexoelectric effect in the piezoelectric layer is taken into account. The static ME effect in the MF composite bilayer with free boundary conditions is investigated. The results indicate that flexoelectricity can dramatically enhance the ME effect in multiferroic composites and structures.

Magnetoelectric analysis of a bilayer piezoelectric/magnetostrictive composite system with interfacial effect

A magnetoelectric (ME) coupling model to analyze the influence of the interfacial properties on the ME behaviors of a bilayer composite system which consisting magnetostrictive (MS) and piezoelectric (PE) layers and works in bend mode are investigated in this article, and the closed form analytical solution is presented. The interface of the bilayer system between MS and PE layer is assumed to be imperfectly connected and is modeled by the shear-lag model. A sixth-order differential equation governing the displacement is derived and its analytical solution is derived. The effect of interfacial property on the static and dynamic ME behaviors includes the average output electrical power density of vibration-based ME bilayer system is discussed. The present analytic results can be degenerated to the ones for a bilayer system with perfect interfaces. It can be found that the interfacial properties play a critical role in the performance characteristics of the ME bilayer system. A quite different feature from previous work is that the static ME effect founded to be length size-dependent. The potential applications of this theoretical analysis can be found in evaluating the performance of the MS–PE composite with imperfectly interface.

Effect of spin excitations with simultaneous magnetic- and electric-dipole character on the static magnetoelectric properties of multiferroic materials

We derive a sum rule to demonstrate that the static magnetoelectric (ME) effect is governed by optical transitions that are simultaneously excited by the electric and magnetic components of light. The ME sum rule is applicable to a broad class of materials lacking the spatial inversion and the time-reversal symmetries, including multiferroic compounds. Due to the dynamical ME effect, the optical excitations in these materials can exhibit directional dichroism, i.e., the absorption coefficient can be different for counter-propagating light beams. According to the ME sum rule, the magnitude of the linear ME effect of a material is mainly determined by the directional dichroism of its low-energy optical excitations. An application of the sum rule to the multiferroic ${\mathrm{Ba}}_{2}$${\mathrm{CoGe}}_{2}$${\mathrm{O}}_{7}$, ${\mathrm{Sr}}_{2}$${\mathrm{CoSi}}_{2}$${\mathrm{O}}_{7}$, and ${\mathrm{Ca}}_{2}$${\mathrm{CoSi}}_{2}$${\mathrm{O}}_{7}$ shows that in these compounds the static ME effect is mostly governed by the directional dichroism of the spin-wave excitations in the giga-terahertz spectral range. On this basis, we argue that the studies of directional dichroism and the application of the ME sum rule promote the synthesis of new materials with large static ME effect.

Length effect on the ME coupling behavior of a simply supported finite composite cylinder

This work presents a three-dimensional exact solution to axisymmetric vibrations of a simply-supported piezoelectric/piezomagnetic composite cylinder. Both the static and harmonic driving magnetoelectric (ME) effects of the composite structure are investigated. It is shown in the numerical results that the length of the composite cylinder has significant effect on the ME effect and cannot be simply neglected. The increase of the length of the cylinder can enhance the static ME effect, while in the frequency driving case the increase of the length can decrease the resonance frequencies and enlarge the first few resonance peaks. The distributions of the electric potential in the piezoelectric layer are plotted to present the magnitude of the electric potential for each length.

Large multiple resonance of magnetoelectric effect in a multiferroic composite cylinder with an imperfect interface

AbstractThe magnetoelectric (ME) effect in a bilayered piezoelectric/piezomagnetic cylinder with an imperfect interface under harmonic excitation is solved analytically. We show that while the interface imperfection would always reduce the static ME effect, the imperfect interface could play a significant positive role in enhancing the ME effect in the frequency domain >100 kHz. Combining with the curvature of the cylinder and the mechanical boundary conditions, we further demonstrate that it is possible to excite large ME effect at double and even multiple resonance frequencies, a unique feature which should be important to various microwave devices, such as antennas.

Multiferroic behavior and magnetoelectric effect in [formula omitted] thick films

A CoFe 2O 4/Pb(Zr 0.53Ti 0.47)O 3 (CFO/PZT) multiferroic composite thick film assisted by polyvinylpyrrolidone (PVP) was prepared by a hybrid sol–gel processing and spin coating technique. Scanning electronic microscopy indicated a porous microstructure with a thickness of 6.2 μm. Pure PZT perovskite phase observed from x-ray diffraction suggested that the low ratio of CFO particles was deeply buried in the PZT matrix. Ferroelectric and ferromagnetic properties were observed simultaneously at room temperature as well as a lower leakage current compared with a CFO/PZT thin film. The dynamic and static magnetoelectric effects were strongly dependent on the applied DC/AC magnetic field but their values were very low. The results demonstrated the prediction that ferroelectric and ferromagnetic properties can induce a strong magnetoelectric coupling only if a dense microstructure was achieved.

One-dimensional equations for piezoelectromagnetic beams and magnetoelectric effects infibers

We derive one-dimensional equations for the extension and flexure with shear deformationof a piezoelectromagnetic beam with rectangular cross section from three-dimensionalequations. The equations obtained are used to analyze magnetoelectric effects infibers of piezoelectric/piezomagnetic composites. Both static magnetoelectriceffects and frequency-dependent magnetoelectric effects in time-harmonic motionsare examined. Various material and field orientations are considered. We alsomake comparisons between magnetoelectric effects in fibers and in thin films onsubstrates. Two-dimensional equations for laminated piezoelectric/piezomagneticplates are used in the analysis of the thin films. It is found that magnetoelectriceffects in fibers are significantly stronger than those in thin films on substrates.

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.