Magnetic and structural properties of Ba–ferrite films prepared by sol-gel processing

The magnetic properties and microstructure of barium ferrite films (BaFe12O19) coated by a sol-gel technique involving a spin coating of metal-organic compounds are investigated. The in-plane magnetic properties and the grain size are controlled by a Fe/Ba atomic ratio in the coating solution and annealing conditions. The in-plane coercivity increases as the decrease of the Fe/Ba ratio and the increase of the annealing temperature. Maximum value of 4–6 kOe is obtained at the Fe/Ba ratio of 2–8 with the annealing at 900 °C for 10 min. At these preparation conditions, the c axis of the hexagonal barium ferrite is slightly oriented parallel to the film plane. The grain size decreases as the decrease of the Fe/Ba ratio. The films with the Fe/Ba ratio of 4–6 show a grain size of almost one-tenth of that of the sputtered films without additives such as Cr2O3 or CoTi. The smaller grain size of the sol-gel-coated films is probably due to the high nucleation density at the annealing process.