Coated acicular magnetic iron oxide particles

摘要

Coated acicular magnetic iron oxide particles having an average major axial diameter of from 0.15 to 0.50 mu m, and comprising: (i) acicular magnetic iron oxide seed particles, containing from 0.05 to 1.0 wt% of phosphorus, calculated as P, based on the weight of the coated acicular magnetic iron oxide particles; (ii) a spinel ferrite inner layer containing cobalt disposed on each seed particle; and (iii) a further coating layer comprising a hydroxide of magnesium disposed on the spinel ferrite layer.