ACICULAR FERROMAGNETIC METAL PARTICLES AND METHOD FOR PREPARATION OF THE SAME

摘要

ACICULAR FERROMAGNETIC METAL PARTICLES AND METHOD FOR PREPARATION OF THE SAME The specification discloses acicular ferromagnetic metal particles having a particle size of 0.1 to 1 .mu.m and a crystallite-size, of not more than about 215 .ANG. in the effective thickness of the crystallite in the direction perpendicular to the reflecting plane (110). These particles have a high coercive force of preferably not less than 1,400 oersteds and are useful for the preparation of highdensity magnetic recording tapes, video mother tapes, and permanent magnet materials The particles are formed by reducing with heating goethite particles which are prepared by treating a ferrous salt with a large amount of a basic agent, particularly an alkali metal hydroxide.