The Magnetoelectric Effect Research Of Magnetoelectric Laminated Structure

Magnetoelectric (ME) laminated materials, especially laminate ME composites made bycombining magnetostrictive and piezoelectric layers, exhibit excellent ME effects, and meet thedemands of practical application for sensors, transducers etc. In laminated ME composites, the MEeffect is derived from the coupling between a magnetostrictive effect in the magnetostrictive layersand a piezoelectric effect in the piezoelectric layers. Elastic deformation is produced by an externalmagnetic field applied to the magnetostrictive layers by means of magnetostriction, and the strain isthen transmitted to the piezoelectric layers, resulting in an induced charge output from thepiezoelectric effect.(1) We adopt three layers of film for the model, in which the upper and the lower layer areelectrodes. We analyze the pure thickness-stretch vibration of a elastic plate, piezoelectric plate,magnetoelectric plate with electrodes, respectively. The equations of coupling vibration areobtained for the plate with two electrodes of unequal thickness. An exact solution is obtained forthickness-stretch vibrations. Some numerical results are figured and presented by means of Matlab.Results show the piezoelectric and magnetoelectric effects on the thickness-stretch vibrationsfrequency. The effects of unequal electrodes are also investigated, which needs to be considered inthe design of very thin and high-frequency resonators.(2) The testing platform of magnetoelectric effect are designed and built, through which wecan test the magnetoelectric effect of the layered ME specimen. We also introduce the preparativemethod of the ME specimen. According to the experiment results, ME coefficient is much higherwhen working around resonant frequency. The resonant frequency of the ME specimen decreaseswith the increasing basic magnetic field, reaches a minimum and then increases. The increasingbasic magnetic field also makes ME coefficient increasing rapidly then decreasing a little. That′sbecause the bias magnetic field can reduce the current loss of the specimen. We further test theeffect of a tiny bias magnetic field (10-5T) on the resonant frequency and ME coefficient, and testsensitivity of the ME specimen. Through above experiments, the optimal bias magnetic field canbe determined about300Oe..(3) We also study shear-horizontal (SH) waves in a crystal plate of rotated Y-cut quartz incontact with a viscous fluid. The crystal plate and the fluid are governed by the equations of anisotropic elasticity and the theory of Newtonian fluids. A transcendental equation that determinesthe dispersion relations of the waves is obtained. Approximate analytical solutions to the equationare presented for the case of low viscosity fluids and the case of long waves whose wavelength ismuch larger than the plate thickness. The effects of the fluid thickness, viscosity and density on thedispersion relations of the waves are examined. The results obtained are fundamental and useful tothe understanding and design of acoustic wave fluid sensors.