ε-IRON OXIDE TYPE FERROMAGNETIC POWDER, PROCESS FOR PRODUCING THE SAME, AND ε-IRON OXIDE TYPE FERROMAGNETIC POWDER-CONTAINING COMPOSITION

摘要

PROBLEM TO BE SOLVED: To provide ε-iron oxide type ferromagnetic powder with high dispersion stability over time and a process for producing the same.SOLUTION: Provided is the ε-iron oxide type ferromagnetic powder having a powder pH in a range of 4.8 to 6.8. The process for producing the same comprises: subjecting a precursor of a ε-iron oxide type ferromagnetic to a coating formation treatment; performing heat treatment on the precursor after the coating formation treatment to convert the precursor to the ε-iron oxide type ferromagnetic; subjecting the ε-iron oxide type ferromagnetic to a coating removal treatment; and subjecting the ε-iron oxide type ferromagnetic powder obtained after the coating removal treatment to an acid treatment. The pH of the ε-iron oxide type ferromagnetic powder to be produced is controlled by adjusting treatment conditions of at least one of treatments selected from a group consisting of the coating formation treatment, the coating removal treatment and the acid treatment.SELECTED DRAWING: None