PURPOSE: To enhance acid resistance and stability for storage while improving dispersing property, etc. by a method wherein the surfaces of particles are covered with the salt of lanolinic acid with regard to the treatment for the metallic powder available as the recording element of a magnetic recording medium.

CONSTITUTION: The metallic magnetic powder is steeped in an organic solvent in which the salt of lanoling fatty acid is dissolved, and extremely uniform and minute films on the surface s of particles are obtained. Thus, the acid resistance is remarkably enhanced, and the storing property and stability are improved. And when preparing the magnetic material by using the films, the dispersing property and filling property of the magnetic powder can be improved.