To prevent crack and latent crack from being produced upon calcination and hence improve the yield by setting within a specific range a difference between residual magnetic flux densities on the outer peripheral side and the inner diameter side of a cylindrical ansotropic ferrite magnet, on the basis of a pole coil method.
When a mixture where methyl cellulose and water are added and blended in ferrite magnetic powder is extruded and molded, a mold is attached to the tip end of an extruder and a cylinder having an outer diameter of 25.8 and an inner diameter of 8.00 is extruded to produce a molded product. The molded product is cut into a predetermined length and is conveyed into a 2 pole oriented yoke for magnetization. Upon the magnetization non- magnetic spacers 5, 6 are entered between the surfaces of oriented magnetic poles 2, 3 of the oriented yoke, and the thickness between the spacers 5, 6 is changed and processed after drying and calcination, whereby a difference between residual magnetic flux densities on the outer peripheral side of the molded product 1 and the inner diameter side of the same is set to fall within 8%. Thus, crack and latent crack are prevented from being produced upon calicination.
YAMAMOTO MIKIO
MATSUSHIMA JUNJI
NODA TOKUYUKI
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