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 ¿-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 ¿-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.