Magnetic BaFe/sub 12/O/sub 19/ with ultrafine crystallites was produced via a citric acid precursor method. Ester precursors that contained the required amount of Ba/sub 2+/ and Fe/sub 3+/ to form barium ferrites were prepared by chelating Ba/sub 2+/ and Fe/sub 3+/ with citric acid in an aqueous solution of nitrates and then reacting the solution with ethylene glycol at 353 K. The pH values of aqueous solutions were adjusted using ammonium hydroxide. The dried solid precursors were then pyrolyzed at 623, 873 and 1,073 K, respectively. The effects of pH of the starting aqueous solutions on the characteristics of the resultant powder were studied using SEM, TEM, EDM, XRD, and EDS. The experimental results showed that the powder obtained at 873 K or below was composed of .gamma.-Fe/sub 2/ O/sub 3/ and BaCO/sub 3/. At 1,073 K, submicron crystalline BaFe/sub 12/O/sub 19/ powder was obtained.