The Preparation Of Sendust Alloy Films And Its Magnetic Properties

Nowadays, with the rapid development of electronic information technology, there are more and more high requirements in signal processing for electronic products such as mobile phones and computers. Compared with traditional absorbing materials such as ferrite, metal powder, because of various advantages of Sendust alloy films, such as low weight, thin thickness, wide frequency band width, powerful wave absorbing ability, etc, it has attracted great attention and has been applied widely in electronic equipments, especially in electromagnetic absorbing and shielding techniques. Pure thin Sendust alloy films with high adhesion to substrates and good absorbing ability can be fabricated using magnetron sputtering method.At present, the investigation on preparing Sendust alloy films using magnetron sputtering method mainly focuses on the influence of sputtering parameters on the properties of the film, such as: inlet gas flow, substrate temperature, sputtering power, and so on. However, there is much fewer studies on the influence of film thickness, special structures of the film, such as multilayered Sendust alloy film structure using C film as an interlayer. There is also very few investigations on the influence of applied magnetic field when depositing the films. Thus, in this paper, firstly, serials of Sendust alloy films with different thickness were prepared using magnetron sputtering method and the influence thickness on the micro structure, electromagnetic properties were investigated. After that, multilayered Sendust/C films with different thickness of each Sendust alloy films were prepared. The influence of film thickness and film structure on the microstructure and magnetic properties of the films were studied. Then, researches on the influence of vacuum annealing process were carried out. Finally, we applied an oriented magnetic field onto the substrate when depositing the Sendust film, trying to modify the microstructure of magnetic domain of the films to get better magnetic performance. The followings are some results:(1) Serials of soft magnetic Sendust alloy films with different thickness were prepared using magnetron sputtering method, and the effect of thickness on the surface morphology, magnetic domain structure and surface resistivity of the films were studied. It was shown that Sendust alloy films with different thickness can be stably fabricated under certain conditions: substrate temperature 150oC; sputtering voltage 520 V and sputtering current 0.69 A; gas flow rate, 20 sccm, respectively. When depositing time was 30 min(with the film thickness of about 385 nm), the surface of the film is smoother with smaller surface roughness. It has clear magnetic domain morphology with good soft magnetic properties. The magnetization(Ms) and coercive force(Hc) of the film measured by a vibrating sample magnetometer(VSM) are 769.48 emu/cm3 and 33.63 Oe, respectively.(2) The surface of Sendust/C multilayered film is smoother than that of Sendust alloy monolayer. It was suggested that the ferromagnetic layer of the as deposited Sendust/C multilayer might be a mixture of crystalline and amorphous phases, since the crystallinity of the films measured by the X-ray Diffraction(XRD) is not high. VSM data shows that except two-layer film, the Ms of three-layer, four-layer and five-layer Sendust/C film was higher than that of single-layer Sendust alloy film. Compared with Sendust alloy monolayer, the Ms of five-layer Sendust/C film increases by 27.94%. The coercive force decreases with decreasing thickness of the ferromagnetic layer in the multilayered structure with the maximum reduction of coercive force up to 58.13%.(3) After being vacuum annealed at 500 oC, the grain size of the films grew obviously and the stress was reduced. The peak intensity of XRD patterns was also enhanced. DO3 superlattice structure can be clearly confirmed in XRD patterns after annealing, which indicates that Si atoms and Al atoms were dissolved into the lattice of ?-Fe forming an ordered solid solution. After annealing, stripe-like magnetic domains were seen through magnetic force microscopy(MFM), which might be somehow related with the decreasing of internal stress.(4) A preliminary study on the influence of applied orientational magnetic field on the microstructure of Sendust alloy films was also carried out in this paper. It was found that the orientational magnetic field can affect the arrangement of magnetic particles to form more ordered domain structure when deposited onto the substrate. The growth type and magnetic properties of the films can also be changed.