| Hexagonal barium ferrite BaFe12019, can be used in such micro-wave circulators et al. due to its large uniaxial magnetic anisotropy, large resistivity and high permeability at high frequencies. Barium ferrite films must be prepared in order to integrate micro-wave devices in micro-wave circuit. In this paper, RF magnetron sputtering was used to deposit barium ferrite films. The effects of sputtering and annealing parameters on the micro-structures and magnetic properties of barium ferrite films were studied. However, the thickness of barium ferrite films is required larger than 10μm to meet the micro-wave circulator. But the preference of film growth in the (001) direction and the magnetic properties of BaFe12019 film get bad with the increase of BaFe12019 film thickness. So, in order to improve the preference of film growth in the (001) direction of BaFe12019 thickness films, barium ferrite multilayers were prepared by depositing Al, MgO and BaFe12019 buffer layers. The followings are the main results of this work:With the increase of the substrate temperature, the preference of film growth in the (001) direction is decreased. The highest 4.56 kOe of Hcj and 0.82 of Mr ratio are achieved at the substrate temperature of 500℃. With the increase of the ratio of O2 and Ar, the Hcj and Mr ratio show a hump. When the ratio of the O2 and Ar is 10:90, the maximum of Hcj and Mr ratio achieved are 3.85 kOe and 0.80. This is also the case of increasing the sputtering power, where the two values have their maxima of 3.79 kOe and 0.82 at 80 W, respectively.The results show that buffering layer can improve the preference of film growth in the (001) direction, and then increase the Hcj and Mr ratio of BaFe12019 films. Compared to buffering layers of Al and MgO, the self-buffering produces the largest Mr ratio =0.7 and Hcj=3.63 kOe with film thickness about 10μm. When the annealing temperature is 1000℃, with the increase of annealing time, the Hcj and Mr ratio of the samples decrease. |
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