Coercivity for Ba-ferrite superfine particles

Intrinsic coercivity for Co and Ti substituted Ba-ferrite superfine particles free from agglomeration, and the particle agglomeration effect, were investigated by measuring coercivity for Ba-ferrite particles dispersed and attached onto SiO 2 particles. The coercivity for small aspect ratio (diameter to thickness ratio) Ba-ferrite platelet particles increases with decreasing the Ba-ferrite concentration in the samples and attains a constant value, which can be regarded as the intrinsic particle coercivity. Small aspect ratio Ba-ferrite platelet particles showed coercivity decrease with particle agglomeration, while large aspect ratio particles showed coercivity increase. The particles with intermediate aspect ratio showed no coercivity change due to particle agglomeration. The coercivity increase with increasing agglomeration, which seems to be characteristic behavior for Ba-ferrite platelet particles, is caused by a formation of particle stacking agglomeration, which behaves like particles with small aspect ratio.