The Study On The Magnetic Anisotropy And Dynamic Magnetization Property Of Amorphous FeCo-based Soft Magnetic Alloy Thin Film

Amorphous FeCo-based alloy films have excellent electromagnetic properties in the GHz band,which is superior to the traditional ferrite and permalloy materials.In order to meet the damping,resonant frequency,and permeability requirements of amorphous FeCo-based soft magnetic alloys under different application backgrounds,it is very important to study the relevant magnetization mechanism to provide theoretical guidance for its design and preparation.In the amorphous FeCo-based soft magnetic alloy films,the effective anisotropy field is an important factor in determining the static and dynamic magnetic properties of the films.In order to explain the effective anisotropy field in different magnets,the researchers proposed various anisotropic physical models,e.g.local anisotropy,surface anisotropy,random anisotropy,and interfacial anisotropy.Usually,the opposite field is equivalent in one direction,in order to analyze simply.In order to analyze and explain the magnetic properties of the films essentially,this dissertation takes into account that the magnet energy is the most fundamental factor to determine the effective anisotropy field.The physical model is constructed from the energy point of view to study the anisotropic field and the dynamic magnetic properties what are effectted by thickness,grain size,interface,and micro structure.The method of FeCo-based amorphous soft magnetic thin film based on the internal energy control is proposed to realize the multi-resonance,broadband and controllable resonant frequency of the film.The main researches of this dissertation are as follows:1.Based on the thickness of the film,the regular transition points in the range of 80 nm ~ 100 nm is found,and the mechanism of the natural resonance frequency transition is proposed from the magnetostatic energy.With the increase of film thickness,the domain wall structure of the film will change,so that the resonance frequency with the film thickness is no longer regularity.The study of the effect of domain wall variation on resonant frequency provides a new guidance for film thickness selection.2.With the presentation of the amorphous Ta buffer layer between the amorphous FeCo-based soft magnetic alloy film and the Si substrate,Ta layer can improve the film's resonant frequency is proved.The characteristics of the resonant frequency of the film with temperature are measured,and the effect of the internal stress on anisotropic field and resonance frequency is analyzed.The interface effect between Ta and FeCo layer makes the vertical anisotropy of the thin film,and the existence of vertical anisotropy makes the resonant frequency sensitive to temperature,which provides the theoretical basis for the temperature stability of the resonant frequency of the film.3.Based on the annealing treatment of amorphous FeCo-based soft magnetic alloy films,the change of structure and magnetic properties is studied,systematically.The change of anisotropy with grain growth and particle formation is made out.The growth of the grains makes the magnetocrystalline anisotropy gradually replace the induced anisotropy.The formation of the individual particles makes the shape factor of the film change.The imaginary part of the permeability can maintain at 50 or more and the damping reaches 0.18 in the range of 0.5 GHz ~ 5.5GHz,by controlling the grain size and particle size.4.The microstructures of amorphous FeCo-based soft magnetic alloy films are proposed,and the correlation between natural resonance frequency and anisotropy is calculated theoretically.The shape anisotropy caused by the structure and the induced anisotropy caused by the induced field exist in the film at the same time,which determines the magnetic domain structure,as well as the effective anisotropy and resonance frequency.Through the design of antidot,the resonant frequency can be improved,and broadband,multi-peak characteristics can be achieved.This dissertation is of significance to the preparation of amorphous FeCo-based soft magnetic alloy films.The anisotropic field and dynamic magnetic properties analysis method are used to prepare amorphous FeCo-based soft magnetic alloy films with different magnetic properties for different requirements Provides a design idea.