The Preparation And Microwave Soft Magnetic Properties Of Co₂Feal-based Thin Films

With the rapid development of modern electronic devices and data transmission technology, the higher requirements, such as high saturation magnetization, low coercive force and high ferromagnetic resonance frequency, were desire in magnetic components like the vertical magnetic recording head, thin-film micromagnetic inductor, etc.In this dissertation, Co2FeAl and (Co2FeAl)1-x(Si)x high-frequency ferromagnetic thin films were prepared by an oblique sputtering method in a magnetron sputtering device. The high-frequency ferromagnetic properties and theoretical origination for high uniaxial magnetic anisotropy of the films were investigated. The investigation details were summarized as follows:Firstly, Co2FeAl films were prepared by an oblique sputtering method, using radio frequency (RF) power. The effects of argon flow, working pressure, the sputtering time and power on the in-plane uniaxial magnetic anisotropy (UMA) were investigated. The optimal preparation conditions were obtained, i.e. argon flow of5sccm, working pressure of0.11Pa, sputtering time for15min, and sputtering power of80W. According to these conditions, Co2FeAl films with good microwave soft magnetic properties, such as the HK of239Oe,fFMR of4.4GHz, and coercive force of34Oe, were prepared at room temperature. These results imply that the Co2FeAl film is a promising magnetic material in application of microwave devices.Secondly, nanocrystalline Co2FeAl soft magnetic thin films with a tunable in-plane uniaxial magnetic anisotropy were prepared by an oblique sputtering method. The thin films without any annealing treatment or magnetic field induction exhibit higher in-plane uniaxial magnetic anisotropic field, which can be attributed to the film thickness gradient due to the oblique sputtering. For the sample position from n=1to9, the Hk is49,69,79,119,139,171,199,219,239Oe, respectively. Accordingly,fFMR also gradually increases from1.95GHz to4.4GHz. The Si-doped Co2FeAl films were prepared using radio frequency power supply by an oblique sputtering method with several Si slices pasting on the Co2FeAl target. The optimal high-frequency ferromagnetic performances with HK of213Oe, HC of20Oe, Ms of1076emu/cm3, and fFMR of4.3GHz, were achieved under the conditions of doping two Si slices and sputtering power of80W.