FERRITE POWDER FOR BONDED MAGNET, METHOD FOR PRODUCING SAME AND BONDED MAGNET USING SAME

摘要

In a bonded magnet, the energy product, which is the product of the residual magnetic flux density (Br) and the coercive force (Hc), should be enlarged. When a particle size of a ferrite powder for a bonded magnet is reduced to increase the coercive force, however, jamming is reduced and Br is lowered. When the particle size is enlarged to increase the magnetic flux density, in contrast thereto, the coercive force is lowered. To enlarge the energy product, therefore, both Br and Hc should be enlarged. A ferrite powder, which has a large particle size, occurs as beautiful crystals and shows little lowering in the coercive force upon pressurization, is obtained by mixing a ferrite powder, which has been baked at a temperature of 1050-1300oC under saturated vapor pressure of a chloride, with a ferrite micropowder having a small particle size, and annealing the mixture at a temperature of 800-1100oC. A bonded magnet produced by using this powder has an energy product greater than or equal to 2.0 MGOe.