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

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Abstract
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.