Research On Capacitive Magneto-impedance Effect Based On Debye Model

With the development of composite materials,Piezo-magnetostriction"as a magnetoelectric composite material has made rapid progress in the study of its magnetoelectric coupling effect in recent years,especially as researchers understand the nature of magnetic-force-electrical coupling physics,the research of magnetoelectric composite materials has gradually developed from the physical properties of materials to the device performance of materials.For example,the piezoelectric transducer under the adjustment of the magnetic field can solve the problems of the resonance frequency shift and impedance mismatch caused by the transducer and the external factors,and ensure the working efficiency and stability of the transducer.The research of magnetic capacitance and magnetic impedance sensors also provides a design basis for low magnetic field detection.The principle of the magnetic capacitance and magnetic impedance sensor is the magnetic impedance and magnetic capacitance effect under the adjustment of the magnetic field.Since there is a certain relationship between the magnetic impedance effect and the magnetic capacitance effect,the change of the magnetic impedance can be used to study the change of the magnetic capacitance,and the change of the magnetic capacitance can also be used to verify the change trend of the magnetic impedance.This article studies the magnetic impedance effect from two aspects.?1?The change of magnetic impedance is not only related to the material of the magnetoelectric composite vibrator,but also has a great relationship with the polarization direction of the piezoelectric phase.Therefore,we studied the influence of the polarization direction of the piezoelectric body on the magnetic impedance effect of the magnetoelectric composite vibrator at room temperature from both theoretical and experimental aspects.?2?The experiment found that the demagnetization factor of the magnetostrictive phase also affects the magnetic impedance effect of the composite vibrator.Therefore,four kinds of magnetoelectric composite structures are designed to study the effect of the demagnetization factor on the magnetic impedance effect.The specific research content is as follows:?1?There is an inseparable relationship between the magnetic impedance of a magnetoelectric resonator and the polarization direction of the piezoelectric phase.This article uses a sandwich-structured magnetoelectric composite oscillator,the piezoelectric body is selected from lead zirconate titanate Pb(Zr_?1-x?Ti_x)O₃?PZT?,Selection of magnetostrictive phase Tb_?1-x?Dy_xFe_2-y?TDF?.Starting from the combination of length-polarized and thickness-polarized piezoelectric bodies and transverse magnetized magnetostriction,the experiment studies the change of the magnetic impedance and magnetic capacitance of the magnetoelectric composite vibrator with length polarization and thickness polarization at the resonance frequency with the magnetic field.Experiments show that the magnetic impedance of the piezoelectric-phase length-polarized magnetoelectric composite vibrator is much greater than the thickness-polarized magnetoelectric composite vibrator.?2?In piezoelectric polarization theory,Lorentz model and Debye model are usually used to explain the change of dielectric constant of piezoelectric body with frequency,Based on the Debye model,this paper studies the magneto-impedance effect of a thickness-polarized piezoelectric/magnetostrictive composite oscillator based on the piezoelectric equation and the wave equation theory of the composite oscillator.The reason that the magnetic impedance is much larger than that of the thickness-polarized piezoelectric/magnetostrictive composite vibrator.The influence of the polarization direction of the piezoelectric phase on the magnetic resolution of the magneto-electric composite vibrator at the resonant frequency is also studied.The relationship between capacitance and magnetic field was simulated numerically by using Matlab programming.The experimental results are basically consistent with the simulation.?3?Four kinds of magnetic-electric composite vibrator models are designed experimentally,which are mainly divided into two-layer magnetic-electric composite structures and three-layer magnetic-electric composite structures.The piezoelectric phases are all length-polarized,and the magnetostrictive phases have different TDF sizes?different demagnetization factors?,which are used to prove the effect of demagnetization factors on magnetic impedance.Experimental results show that,whether it is a two-layer magnetoelectric composite oscillator or a three-layer magnetoelectric composite oscillator,the larger the demagnetization factor,the smaller the magnetic impedance of the magnetoelectric composite oscillator.