A SURFACE-TREATED MAGNETIC POWDER AND A MOLDABLE PERMANENT MAGNET COMPOSITION CONTAINING THE SAME

摘要

A surface-treated magnetic powder from which may be formed a resin-bonded permanent magnet with large magnetic force and a high maximum energy product, which magnetic properties do not decreases even after long periods of time, is obtained by treating a magnetic powder comprising an alloy containing at least one rare earth metal and iron with a treatment agent comprising alkali-modified silica particles which are obtained by reacting silica particles having a mean particle diameter of from 0.005 to 0.1 mu m with an alkali in a manner such as to modify only the surface portion of the silica particles by the alkali.