Influence of calcium on properties of strontium and barium ferrites for magnetic media prepared by combustion

For preparation of the strontium (SrFe 1 2 O 1 9 ) and barium (BaFe 1 2 O 1 9 ) hexaferrite powder, with CaO additive used in magnetic recording we used a new method, which is an improved variant of the coprecipitation method. According to this method, named self combustion, the reacting substances are metal nitrates and ammonium hydroxide. The CaO additive improves the coercitivity of hexaferrites and a better control of the grain growth is achieved.