Preparation Of BaFe₁₂O₁₉ Thin Films By Sol-Gel Method And Characterization Of Magnetic Properties

Barium ferrite (BaFe12O19, BaM) is a ferrimagnetic oxide with a hexagonal crystal structure. M-type BaM hexaferrites have relative high coercivity, large saturated magnetization, excellent chemical stability, mechanical hardness, corrosion resistance and huge uniaxial anisotropy energy. It has been widely used in permanent magnets, microwave devices and so on.In this paper, BaFe12O19films were prepared by Sol-Gel method with nitrate as raw materials and citric acid as complexing agent. The phase influence about different precursor sol, heat treatment temperature and time, citric acid for preparing BaFe12O19films were all studied and optimized by contrast experiments. On the basis of this, the influence on BaFe12O19structure and magnetic properties by Al3+and Co2+substituted were researched respectively. The main contents and conclusions are as followings:BaFe12O19films were synthesized by Sol-Gel method with iron nitrate, barium nitrate as reactants and citric acid as complexing agent. The contrast experimental results showed that the pre-sol could be synthesized if the molar ratio of iron nitrate to barium nitrate was6.5and citric acid to barium nitrate was7.5. Each wetting layer was heating to300℃first and holding for10minutes, then heating to450℃and holding for another10minutes, repeating this process several times until we got the required thickness. At last the films’ heat treatment temperature was850℃, holding for2.5hours. By this technique we will get the Ms and He of the BaFe12O19film are about202.2emu/cm3,3011.3Oe respectively.BaAlxFe12-xO19films by Al3+substituted Fe3+were prepared referring to the pure BaFe12O19films’preparation process. Research showed that, Saturation magnetization and remanent magnetization showed a decreasing trend when x value increased. However, coercive forece increased monotonously with the increased of x value. He is about 3298.99Oe. BaCoyFe12-yO19powders by Co2+substituted Fe3+were prepared referring to the pure BaFe12O19powders’preparation process. Research showed that, In the power samples, as y value increased, the saturation magnetization, the remanent magnetization and the coercive force went up first then down.