Black magnetic iron oxide particles for magnetic toner and process for producing the same

摘要

Black magnetic particles having an average particle diameter of from 0.1 to 0.3 mu m, which comprises: (a) black spinel iron oxide particles as core particles; and (b) a coat comprising spinel iron oxide particles provided on the surface of each core particle, the content of FeO in a surface layer having a thickness of from the surface of each black magnetic iron oxide particle to about 3.5% of the radius of the particle, being from 8 to 14% by weight based on the weight of Fe contained in the surface layer.