MAGNETIC IRON OXIDE PIGMENT AND MANUFACTURE

摘要

Magnetic iron oxide pigments having a monomolecular coating of a cobalt compound useful in magnetic signal recordings having a dependence of coercivity on temperature in the temperature range of from 76 K to 298 K of less than 0.13 kA/mK and having a coercivity on powder compressed to 0.9 g/cm3 of greater than 51 kA/m are prepared applying a preliminary coating of Fe3O4 or a bertholloid compound to a magnetic iron oxide core material having the composition FeOx where x is a number from 1.33 to 1.55 and then covering the preliminary coating with a cobalt compound.