Device Design And Research On Bending Magnetoelectric Effect In Bi-layer Magnetoelectric Laminated Structures

By the combination of magnetostrictive materials and piezoelectric materials,layered magnetoelectric laminates have strong magnetoelectric coupling effect.The magnetoelectric coupling effect is divided into direct magnetoelectric effect that generates electric polarization by applying a magnetic field to the laminated material and converse magnetoelectric effect which generates magnetic polarization by applying an external electric field,and these two effects are widely concerned.The strong magnetoelectric effect showed by direct and converse magnetoelectric effect makes the magnetoelectric laminates have an important position in sensing,driving,microwave communication and other fields.Based on the constitutive relation of the piezoelectric layer and the magnetostrictive layer,a theoretical model of non-linear direct/converse magnetoelectric coupling coefficient is established for the asymmetric bilayer magnetoelectric laminated structure of magnetostrictive material/piezoelectric material,further the magnetoelectric coupling coeffcient under different stress,temperature,external magnetic field,material thickness ratio is studied.Aiming at magnetostrictive/piezoelectric asymmetric bilayer magnetoelectric laminate structure that is commonly used in ME sensor,a bilayer static nonlinear magneto-mechanical-electro-thermal coupled theoretical model is established,the model is based on the mechanical-electric linear constitution relation of piezoelectric layer and one-dimension nonlinear thermal-magneto-mechanical constitution relation of giant magnetostrictive material and also considering bending deformation caused by the asymmetric structure.In order to conveniently verify the validity of the model,magnetostrictive material and piezoelectric material are selected to prepare bilayer asymmetric magnetoelectric composite structure sample,whose static magnetoelectric coefficient are measured under different temperature and bias magnetic field.When the model is degenerated to a ME coefficient model without stress,compared to the experimental result,the predicted result of the model has good consistency both qualitatively and quantitatively,which verifies the validity of the model.Based on this,the influence of pre-stress,bias magnetic field,temperature,as well as different thickness ratio and piezoelectric materials on magnetoelectric coefficient and sensitivity is analysised through this model.Secondly,considering the non-volatility and sensitivity of the converse magnetoelectric effect,it has important potential in magnetic logic devices and microwave devices for adjusting magnetic properties by electric field.Considering that the bending resonance mode can achieve a relatively high converse magnetoelectric coupling effect at a relatively low frequency,the linear constitution relation of piezoelectric layer and the nonlinear thermal-magneto-mechanical constitution relation of giant magnetostrictive material are adopted to establish the equivalent circuit model of converse magnetoelectric effect under bending resonance in view of the nonlinear converse magnetoelectric effect of Terfenol-D/PMN-5H asymmetric bilayer magnetoelectric laminate structure under bending resonance.Based on this,the expressions of the nonlinear resonant converse magnetoelectric coefficient and the resonant frequency of the nonlinear bending resonant mode are obtained.According to this model,the variation trend of the nonlinear converse magnetostrictive coefficient of the bending resonant mode with the bias magnetic field,prestress,etc.can be predicted effectively,and it has good consistency both qualitatively and quantitatively with the experimental results of the bilayer bending resonant converse magnetoelectric coupling effect.Finally,in order to further discuss the relationship between the magnetoelectric coupling effect and the frequency of the bilayer magnetoelectric laminated structure under the bending mode,bilayer magnetoelectric laminated structural is manufactured.Recording and processing the experimental data under different bias magnetic fields and different resonant frequencies,then the converse magnetoelectric coefficient as a function of bias field and resonance frequency can be obtained.It is found that when the bias magnetic field is fixed,two resonance peaks of the converse magnetoelectric coupling coefficient appear with the change of the resonance frequency,corresponding to the bending resonance frequency and the length resonance,respectively.At the magnetic resonance frequency,the converse magnetoelectric coupling coefficient first increases and then decreases with the change of the bias magnetic field.The double-peak phenomenon of the converse magnetoelectric effect guarantees a larger magnetoelectric coefficient within a wider bias field,and the increase of the converse magnetoelectric coupling effect can be achieved through the regulation of the bias magnetic field and the resonant frequency.Later in the study of magnetoelectric material devices,it was found that the piezoelectric and magnetoelectric effects of the prismatic magnetoelectric composites are larger than those of the rectangular magnetoelectric composites,and they have greater stress sensitivity.On this basis,a new type of piezoelectric alarm and magnetoelectric sensor is designed.The nonlinear theoretical model of the direct and converse magnetoelectric coupling effect of the bilayer magnetoelectric laminated structure in the bending mode is further perfected in this paper,which provides a theoretical basis for the design of the magnetoelectric sensor.