Acicular ferromagnetic iron oxide particles and process for producing the same.

摘要

There are provided acicular berthollide particles comprising crystalline particles expressed by the formula FeOx (1.33 </= x < 1.5) and modified with a specific amount of zinc ions and a process producing the same which comprises the steps of oxidizing acicular magnetic iron oxide particles expressed by the formula FeOx (1.0 < x < 1.33) and modified with a specific amount of zinc ions which are produced by (a) heating and dehydrating acicular hydrous iron oxide particles containing a specific amount of a zinc component, reducing, and heating the particles under specific conditions, or (b) reducing acicular iron oxide particles containing a specific amount of a zinc component and heating the particles under specific conditions, or (c) heating acicular magnetic iron oxide particles expressed by the formula FeOx (1.0 < x < 1.33) containing a specific amount of zinc ions under specific conditions.