Study On Magnetoelastic Coupling Regulation Mechanism For Composite Multiferroic Devices

In recent years,the development of communication and computer technology has put forward requirements for miniaturization,high efficiency,low power consumption,and integration of antennas and random access memories.The radiation of traditional antennas depends on electromagnetic resonance,so their physical size is limited by the electromagnetic wave length,and the road to miniaturization has come to an end.To further reduce the size of the antenna,it is only possible to change this situation by breaking the shackles in principle.In addition,currently,random access memories derived from transistors are volatile and have high power consumption,which greatly restricts the further miniaturization and integration of memory chips.However,composite multiferrous devices composed of piezoelectric and magnetostrictive materials are expected to solve these difficulties.These types of devices have similarities in their structure,so even conclusions drawn from typical case studies using one of them still have universality.Therefore,the topic of this thesis focuses on the research on the mechanical loss and magnetic damping loss inside ferroelectric devices such as magnetoelectric antennas and novel magnetoelectric memories.The main work and innovations of this thesis are as follows.Based on the eddy current effect and aperture electromagnetic field theory of the device,a magnetic damping displacement analytical model for composite multiferrous devices was constructed.Using the differential form of the full current law and Faraday’s law of electromagnetic induction in Maxwell’s equations,combined with the constitutive relationship of magnetostrictive materials,the expression of induced alternating current driven by stress is derived.The interaction between the induced current and the magnetic flux generates Lorentz force in the opposite direction of resonance.Finally,the mechanical displacement model under the action of magnetic damping is obtained.Through finite element software analysis,it was found that the peak mechanical displacement at the resonant frequency of 2.76 GHz is approximately 14 nm,which is in good agreement with the analytical model.Simultaneously changing the thickness parameters in the mechanical displacement analysis model,it was found that when the thickness of the piezoelectric and magnetostrictive layers is equal,the mechanical displacement is relatively large.This is consistent with existing experimental research conclusions.The parameters such as thickness and damping factor that affect the mechanical displacement can regulate the magnetoresistive loss,providing a possible solution for the design of composite multiferrous devices.A mechanical loss model for composite multiferrous devices was constructed using elastic mechanics methods.The expression for the magnetoelectric coupling coefficient of composite multiferrous devices considering mechanical losses was derived by considering the stiffness constant of the material as a complex form.After introducing the complex stiffness constant,the mechanical quality factor and electromechanical coupling coefficient considering mechanical losses were derived through the definitions of wave number and sound speed.The total stored energy and average power under the influence of mechanical losses were calculated.Similarly,the mechanical quality factor of the magnetostrictive layer considering mechanical losses was derived,and the total stored energy and average radiation power of the layer were calculated.Finally,the mechanical quality factor of the composite structure was derived using the concept of volume proportion,and the expression for the magnetoelectric coupling coefficient of the composite structure under mechanical loss was given.Then,through finite element simulation,it was found that the mechanical quality factor decreases with the increase of mechanical loss,and the total energy storage also decreases with the increase of mechanical loss,which is consistent with the results generated by the analytical model and experimental testing.At non resonant frequencies,mechanical damping has almost no effect on the mechanical quality factor and energy,but at resonant frequencies,the impact is very significant and can deteriorate device performance.This provides a way to regulate mechanical losses and improve device efficiency through viscosity coefficient.