Preparation And Properties Of CoNi/PZT Layered Magnetoelectric Composites

Electromagnetic composites are widely used in transducers,filters,and information storage because of their good magnetic coupling effect.There are many ways to compound magnetoelectric composites.Because of its relatively high magnetoelectric coupling coefficient and simpler preparation process,it has gained the favor of more scientific researchers.However,the theoretical analytical model for the magnetoelectric coupling of layered magnetoelectric composites in a large number of related research work is based on the assumption that the magnetostrictive layer and the piezoelectric layer have the same length and width,ignoring the magnetostrictive layer and pressure.The influence of geometrical effects such as the length and width ratio of the electrical layer on the magnetoelectric coupling coefficient.CoNi and PZT are magnetostrictive materials and piezoelectric materials with typical application values,respectively.In order to provide a basis for the design and application of CoNi/PZT layered magnetoelectric composite device,the numerical simulation analysis of the magnetoelectric coupling effect of CoNi/PZT layered composite structure is carried out,and the geometric effect on the magnetoelectric coupling coefficient is considered.At the same time,in order to meet the requirements of increasing the miniaturization and integration of electronic devices,the process conditions of PZT thin films,CoNi thin films and CoNi/PZT laminated composite thin films prepared by magnetron sputtering were studied.The main work and conclusions of the thesis are as follows:(1)According to the theory of elasticity,the theoretical model of magnetoelectric coupling is established.The analytic equation of the material and the equation of mechanical equilibrium condition are used to derive the expression of magnetoelectric coupling coefficient of CoNi/PZT layered composite structure.The magnetoelectriccoupling is analyzed by numerical simulation.Relationship between coefficients and two material parameters and different geometric size fractions.(2)The numerical simulation results show that the magnetoelectric coupling coefficient first increases with the increase of the thickness fraction of the piezoelectric layer to a maximum value,and then decreases with the further increase of the thickness fraction,and the magnetoelectric coupling coefficient is almost always When the thickness fraction of the piezoelectric layer is about 0.4,the maximum value is obtained;when the width fraction and the length fraction of the piezoelectric layer are changed in the interval of(0,1),the change of the width fraction is related to the magnetoelectricity caused by the change of the length fraction.The change in the coupling coefficient is more significant.(3)The PZT film was deposited by magnetron sputtering.It was found that the Pt electrode after heat treatment made the PZT film have better adhesion.The PZT film obtained by annealing at 650 °C for 5 min had good crystal structure,the surface was dense and the roughness was reduced.More(111)crystal phase is present,and the PZT film sample which is annealed by the PFM test and is electrodeposited has good piezoelectric properties.(4)The single-phase CoNi and CoNi/PZT layered composite films were prepared by magnetron sputtering.When the vacuum annealing temperature was 400?,the saturation magnetization of the CoNi film reached a maximum of 206.23 emu/cc.The coercive force was 105 Oe.The XRD characteristic peaks appear at 2? = 44.36°,51.68°,and76.37°,respectively,and the crystal plane orientations corresponding to the face-centered cubic structure CoNi are(111),(200),and(220)respectively.