NADELFOERMIGE, KOBALTMODIFIZIERTE EISENOXIDE UND VERFAHREN ZU IHRER HERSTELLUNG

摘要

The invention relates to acicular, cobalt-modified iron oxides consisting of a core of an iron oxide of the formula FeOx having values for X of 1.33 to 1.5 and a ferrite shell containing, based on the total amount of material, a total of 0.4 to 12% by weight of cobalt ions and up to 5% by weight of iron(II) ions, which iron oxides are distinguished by improved ageing resistance, particularly with regard to the coercive force, and a process for their preparation.