Synthesis of BaFe12O19 Powder by Modified Coprecipitation and Spray Pyrolysis Methods

Fine barium hexaferrite (BaFe₁₂O₁₉) powder consisting of platelike particles with the magnetoplumbite structure, 30–60 nm in size, is synthesized at 550°C via rapid oxidation of a suspension of barium and iron(II) hydroxides with NaClO. The magnetic properties of BaFe₁₂O₁₉ powders prepared by modified coprecipitation and spray pyrolysis processes are described. The coercivity of fine BaFe₁₂O₁₉ powders is shown to be lower than that of bulk material, which is due to the presence of a magnetically inactive layer of noncollinear spins in the basal plane of the hexagonal particles. BaFe₁₂O₁₉ particles less than 10 nm in size are shown to be in a superparamagnetic state.