Effects of Crystal Structure, Morphology and Ion Diffusion During Annealing on Magnetic Properties of Hexagonal Barium Ferrite Films

In this work, the effect of the crystal structures, morphology and ion diffusion on magnetic properties of the hexagonal barium ferrite films during the annealing process were studied. The structural characterization results demonstrated that the orientation, crystallinity and morphology of the films can be controlled by the anneal temperature. Good crystallinity and morphology of the film can be annealed at a temperature ≥ 1000°C, while the formation of BaFe_12−xAl_xO₁₉ phase occurred due to the ion diffusion when the annealing temperature reached 1200°C. Magnetic hysteresis loops showed that the saturation magnetization, coercivity and remanence ratio of the films were all influenced by crystal structures, morphology and ion diffusion. The platelet particle morphology and high crystallinity demonstrated a good magnetic film, but the ion diffusion mutated the magnetic parameters. Additionally, the first-order reversal curve diagram further verified that the change of crystallite sizes greatly influences the distribution of coercivity and interaction field. Consequently, the film annealed at 1000°C has a high out-of-plane c-axis orientation, high crystallinity with a full width at half maximum of 0.18° and high saturation magnetization of 358 emu/cm³, which can be applied in the microwave device.