Effects Of Annealing On The Electromagnetic Properties Of FeCoB-SiO₂ Nano-Magnetic Thin Films

The Fe-based and Co-based alloy nano-film materials are considered to be used as newly potential microwave-absorbing materials on account of the high permeability and high loss of these nano-film materials. Annealing is an important technology during the preparation of nano-granular magnetic films. As the electromagnetic properties of the magnetic thin films is more and more difficult to meet the requirements, the post-annealing of magnetic thin films has been one of the most important investigated methods.In this paper, the changes of electromagnetic properties in different annealing conditions of magnetic thin films for ultra-high frequency applications have been studied. By comparing the microwave magnetic spectrum curve and the theoretical curve of the annealed FeCoB-SiO2 magnetic thin films, the optimization of technologic parameter has been realized.Based on the preparation process and annealing method of thin film, we analyzed the sputtering and vacuum annealing process of the FeCoB-SiO2 magnetic nano-films. An annealing system with a GZL-1200 vacuum annealing oven was accomplished, which included a full small size thin film annealing system fitting to our equipments. A scheme was set up to do the annealing process successfully, which resolved the problems in the fixing and transporting of nano-film specimens.The electromagnetic properties of specimen under different annealing process were compared by the change of the annealing condition. FeCoB-SiO2 discontinuous magnetic multilayer nano-films annealed under 200-300℃for one hour showed a pretty high Hk being compared to other annealing process. The experimental results were concluded as follow: FeCoB-SiO2 nano-film showed both high permeability and magnetic loss under GHz band by changing the annealing process. Both of the real part and imaginary part of complex permeability of FeCoB-SiO2 nano-film were larger than 200. The resistance of the nano-film specimen could reach as high as 1.67m?·cm. This annealing process could be adopted in the study of radar–absorbing materials.