| As we enter the era of big data,the huge amount of data has higher requirements for data storage devices.If the magnetic field can be controlled by electric field at the micro-nano scale,the density of information storage devices can be further improved,which is helpful to solve the problem.As a multifunctional material,multiferroic materials have magnetoelectric coupling effect between different ferroic order parameters,which is better than the property of a single ferroic material.The film heterojunction of 2-2 type in nanoscals is composite film structure obtained by coating a ferromagnetic film on a ferroelectric substrate,which can obtain a strong magnetoelectric coupling performance.With the development of “spin electronics”,electric charge,spin,orbit and lattice parameters at the interface bring the way to further optimize the magnetoelectric coupling performance.The multi-layer film system is conducive to the study of magnetoelectric coupling effect and various physical mechanisms in a multi-dimensional way at the nanoscale,Compared with single-layer films,multi-layer film systems have superior performance.This thesis analyzes the laws of magnetoelectric performance changes under different coupling mechanisms from single layer to multi-layer,and reveals the potential interaction mechanism in multi-layer films.This thesis takes FM/NM type heterojunction as the main research subject,and the main research contents are as follows:Firstly,four ferromagnetic films of Ni Fe? Fe Al? Fe Co and Fe Co V were prepared by magnetron sputtering on the substrates of silicon,Pt/Ti/SiO2/Si and piezoelectric single crystal,and the physical properties were characterized.The results show:?1?the surface morphology and properties of the films meet the experimental requirements;?2?Ni Fe alloy as the ferromagnetic layer has the best ferromagnetic resonance effect;?3?the ferromagnetic resonance effect and the quality of the deposited film by Pt/Ti/SiO2/Si as the substrate are superior to other samples.Secondly,in the heterojunction constructed with Pt/Ti/SiO2/Si as the substrate,the transition layer Ti and the polarization layer Pt have a great influence on the morphology of the film,which will bring about changes in the magnetic properties of the film.In this thesis,the heterojunction with Au?Ag?Cu as polarization layer and Ta as transition layer was prepared.Through the morphology and ferromagnetic resonance performance,the best polarization layer was determined to be Ag.The transition Ta layer acts as a buffer.Based on the above research,the configuration of the multi-layer magnetoelectric heterojunction was determined.Finally,based on the preparation of multilayer,the adjustmengt of the electric field to the ferromagnetic resonance effect of the heterojunction was studied.In the FM/FE heterojunction,the ferromagnetic resonance frequency and the intensity of the resonance changes with the applied electric field.After introducing the spin pump effect,in the two systems of multilayer FM/NM/FE and FM/NM/FM/FE,when an electric field was applied to the magnetoelectric heterojunction for the first time,it was observed that the film ferromagnetic resonance curve changed drastically near the crystal phase transition electric field.Under the electric field that the crystal can withstand,the intensity of the ferromagnetic resonance increases almost linearly with the applied electric field when the electric field is applied again.In the multi-layer system,it can be intuitively seen that the influences of the phase transformation process and the stress in the crystal on the ferromagnetic film under electric field. |
PDF Full Text Request