Microstructure And Magnetic Properties Of Fe-Sm/Co-Sm Bilayer Films Prepared By Vacuum Thermal Evaporation Under High Magnetic Field

With the development of science and technology,the request of magnetic properties of magnetic materials in more and more fields is higher.The traditional single layer films are hard to meet the need of application.It is meaningful of multilayer films.Multilayer magnetic films were extensively studied by the researchers,but the optimization of magnetic multilayer film had a certain limit.So,external means to optimize magnetic were needed.Because grain boundary can hindered the movement of magnetic domain wall,and strong magnetic field(HMF)had an effect of magnetization energy and magnetic dipole interaction on films,so the different crystal states and HMF could have an important effect on microstructure and magnetic properties of thin films.Therefore,HMF was brought in the preparation process of crystal and amorphous FeSm single films,crystal CoSm single films and FeSm/CoSm bilayer films in this thesis to make use of HMF and different crystal states of bilayer films structure to control magnetic properties.For FeSm monolayer film,the influence of composition,thickness and HMF on the microstructure and magnetic properties of thin films were studied,and the composition and thickness of films with good magnetic properties were determined.For CoSm monolayer film,the influence of composition,heat treatment and HMF on the microstructure and magnetic properties of thin films were studied,and the composition of films with good magnetic properties were determined.For FeSm/CoSm bilayer films,the influence of the different crystalline states and HMF on microstructure and and magnetic properties of thin films were studied.Finally,the optimization of the bilayer films,HMF and different crystalline states of bilayer films on magnetic properties was determined.Main conclusions are as follows:(1)For FeSm monolayer films,the results showed that the composition could change crystal states of FeSm thin films,but HMF and thickness could't change.In terms of different ingredients,FeSm films(<5.8 at.%Sm)had a crystalline structure,mainly composed of alpha Fe phase;FeSm films(>13.9 at.%Sm)had an amorphous structure.With Sm component from the 5.8 at.%increased to 33.0 at.%,coercivity increased by 1227%,saturation magnetization decreased by 74%.HMF decreased coercivity and saturation magnetization.In terms of different films thicknesses,with the increase of thicknesses,saturation magnetization and coercivity of amorphous and crystalline thin films increased firstly and then decreased,and surface roughness increases.HMF reduced the saturation magnetization and coercivity of amorphous films,also reduced its surface roughness.(2)For CoSm monolayer films,the results showed that the composition and HMF could't change the CoSm crystal states,and 18.4 at.%Sm film still maintained a crystalline structure.As Sm composition increased from 6.3 at.%to 18.4 at.%,coercivity and saturation magnetization decreased,and surface line roughness reduced.HMF reduced the coercivity of films,but enhanced the saturation magnetization;reduced the surface roughness of 6.3 at.%Sm and 7.3 at.%Sm,but increased the surface roughness of 18.4 at.%Sm.(3)For FeSm/CoSm bilayer films,the results showed that compared with single CoSm films,HMF and different crystalline states of bilayer films optimized magnetic properties of thin films.Compared with the crystal bottom layer,saturated magnetization and coercivity of the bilayer films with amorphous bottom layer were increased.HMF significantly reduced the columnar width of the top CoSm films.HMF reduced surface roughness,coercivity and saturation magnetization of bilayer films with crystal bottom layer.HMF reduced coercivity and improved the saturation magnetization of bilayer films with amorphous bottom layer,more greatly.