Effect of annealing temperature on the properties of BaFe12O19 thin films deposited on GGG (1 1 1) substrates by pulsed laser deposition

In this work, BaFe12O19 thin films with perpendicular magnetic anisotropy have been deposited on GGG (1 1 1) substrates by pulsed laser deposition in an oxygen atmosphere using a KrF excimer laser. The effects of annealing temperature on the microstructural, magnetic, and microwave properties of BaFe12O19 thin films were investigated. It is found that the properties of BaFe12O19 films are very sensitive to the annealing temperature, and excellent films are obtained when the annealing temperature is above 900 °C. X-ray diffraction diagrams show that films annealed at higher temperatures (≥950 °C) have better crystallization and higher perpendicular orientation. Atomic force images show the surface morphology of annealed films above 900 °C to be very smooth, with a minimum roughness of 0.754 nm. Hysteresis loops reveal that the saturation magnetization of the films annealed above 1000 °C is similar to that of bulk barium ferrite, and the maximum value of 4676 Gs is obtained at 1100 ℃. The anisotropy field increases with the increase in annealing temperature, reaching a maximum of 18.0 kOe at 1050 °C. The remanence ratio and saturation magnetization also show an upward trend as the annealing temperature rises. The film annealed at 1100 °C shows a very narrow ferromagnetic resonance linewidth with a width of about 256 Oe at 39 GHz. And the ferromagnetic resonance linewidth of the films decreases as the temperature rises, which means that films annealed at higher temperatures have less microwave loss.