Structure And Magnetic Properties Of Fe-based Soft Magnetic Bilayer Films

In recent years,high-frequency soft magnetic films play a more and more important role with the development of small size,integration and high-frequency electronic technology and electronic equipment.In order to achieve operational frequency of GHz range,the fundamental requirements for the employed magnetic film are high saturation magnetization,large uniaxial anisotropy and so on.And Fe-based soft magnetic films have relatively large 4πM_s,which satisfies one of the conditions of high frequency application of soft magnetic films.At the same time,there are more and more kinds of composite materials in memory,transducer,drive and sensor.FeGa magnetostrictive material is a kind of special functional material.It has a large magnetostrictive coefficient,good ductility,strong compressive ability.And it is more sensitive to stress,Which makes it easy to induce anisotropy.It is hoped that the functional devices can be developed in miniaturization,integration and high frequency with other Fe-based soft magnetic films.It has been attracted much attention in information and communication technology fields.In order to get the high frequency application,it is very important to further improve magnetism of FeGa films.In this paper,A series of FeGa/FeCo,FeGa/FeNi films were prepared with different conditions.And the structure,morphology and magnetism of films are studied.The main contents are organized as follow:Firstly,there has been studied on the structure,morphology and magnetism of FeGa films with different thickness and heat treatment temperature.It is found that:(1)H_c increases,M_r/M_s decreases and 4πM_s firstly increases then decreases with increasesd FeGa film thickness.(2)The density of FeGa film gradually inclines to low,H_s gradually increases and 4πM_s shows a tendency of decrease then increase with increasing heat treatment temperature from RT to 800 ~oC;as well as maximum value is about 14 kGs.The above results have laid a foundation for the study of Fe-based magnetostrictive soft magnetic bilayer films.Secondly,based on the previous work,we have been studied on the structure,morphology and magnetism of FeGa/FeCo films with different preparation condition.And the results show that:(1)The bilayer FeGa/FeCo films present the magnetic spring structure and the films have the better anisotropy with a applied external field for FeGa layer.(2)The substrates for FeGa/FeCo films can be choosed according to own requirement.On Si substrate,The FeGa/Fe Co film is uniform,continuous and smooth,which has the smaller particle size and H_s,moderate H_c,larger M_r/M_s and4πM_s.The FeGa/FeCo film on the Cu substrate has the larger particle size,larger H_c,larger H_s,moderate M_r/M_s and smaller 4πM_s.(3)The effects of stress on the magnetic properties of FeGa/FeCo films have been studied by applying different stress strain on Cu and PET substrates.The results show that the effect of tensile stress on the morphology of the FeGa/FeCo film is stronger and the anisotropy of films is larger for Cu substrate.On the contrary,the compressive stress has a stronger effect on the morphology of the film on PET substrate,and the anisotropy is larger in this condition.(4)The structure,morphology and magnetism of the FeGa/FeCo are studied by changing the substrate temperature from RT to 500 ~oC in the deposition process.It is found that,the particle size and H_c of the FeGa/FeCo films decreases,and the anisotropy firstly increases and then decreases with the increasing of substrate temperature.(5)As the increase of heat treatment temperature,the grain size of the film gradually increases and the quality of the film is poor.The H_s and H_c of FeGa/FeCo films increase with the improving of heat treatment temperature.And M_r/M_s of FeGa/FeCo films firstly increases and then decreases with the increase of heat treatment temperature.Finally,there has been studied on the structure,morphology and magnetism of FeGa/FeNi films with different preparation condition.(1)The bilayer FeGa/FeNi films present better anisotropy and double resonance peaks with a applied external field for FeGa layer.The H_c,4πM_s and H_k of the FeGa/Fe Ni films gradually increase with the increase of FeGa layer thickness.And when the FeGa thickness is 25 nm,it presents an obvious exchange spring structure.(2)The better anisotropy of bilayer FeGa/FeNi films is induced by oblique sputtering.And the anisotropy of bilayer FeGa/FeNi films remains the same with the increasing oblique sputtering angle from32 and 40~o.(3)The effect of stress on the magnetic properties of FeGa/FeCo films are studied by applying different stress on Cu and PET substrates.The tensile stress has a greater influence on the magnetization of EA of FeGa/FeCo films on PET substrate.And the anisotropy of films is larger with tensile stress.On the contrary,the tensile stress has a stronger effect on the magnetization of HA of Fe Ga/FeCo films on Cu substrate,and the anisotropy is larger in this condition.