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

摘要

A bonded magnet is required to have a large energy product, which is the product of magnetization Br and coercive force Hc. However, in a ferrite powder for a bonded magnet, when the particle diameter is reduced to improve the coercive force, the packing properties are impaired, and the Br is lowered.
When the particle diameter is increased to improve the magnetization, the coercive force is lowered.
Therefore, to increase the energy product, both the Br and Hc must be increased.
A ferrite powder that has a large particle size, is composed of smooth crystals, and suffers only a small reduction in coercive force even after pressurization is obtained by mixing a fine ferrite powder having a small particle size with a ferrite powder calcined at a temperature of 1050°C to 1300°C in the presence of a chloride at its saturated vapor pressure and then annealing the mixture at 800°C to 1100°C.
A bonded magnet produced using the powder has an energy product of 2.0 MGOe or more.