Preparation of Acicular Barium Ferrite Particles and Their Magnetic Properties

Methods for producing acicular barium ferrite particles for use in coated tape media were studied, and their magnetic and other properties were investigated. Acicular α-FeOOH particles were dispersed in a BaCl₂ solution, and NaHCO₃ added to precipitate BaCO₃ on the particle surfaces. After washing and addition of B₂O₃, P₂O₅, or Bi₂O₃, particles were fired at 800 to 900°C; addition of B₂O₃ and firing at 850°C were found to produce good particle properties. In particular, on starting with 1.5 to 1.75 mole BaCO₃ to 12 moles α-FeOOH, adding 0.5 wt% B₂O₃ and firing at 850°C, Ba ferrite particles had a saturation magnetization of 40 emu/g, coercive force of 3200 Oe and Curie temperature of 443°C, with a strong magnetic anisotropy directed normal to the particle longitudinal axis.