RING-SHAPED MAGNET AND MANUFACTURING METHOD THEREFOR

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PROBLEM TO BE SOLVED : To provide a ring-shaped magnet that can be incorporated into a spindle motor for HDDs whose specified size is less than 1 inch, for example, thus contributes to reduction in the size and thickness of a motor, is excellent in magnetic properties, and makes it possible to sufficiently ensure the performance and quietness of a motor. SOLUTION : Raw material alloy powder predominantly composed of R, T, and B is molded and sintered to obtain a ring-shaped rare-earth sintered magnet whose outside diameter is between 7 mm and 11 mm inclusive and whose thickness is between 0.4 mm and 1 mm inclusive. Poles are anisotropically oriented during molding, and magnetic poles whose number is between 8 and 24 inclusive are formed on the outer circumferential surface by magnetization after sintering. Its inside diameter is between 5 mm and 8 mm inclusive. R is at least one kind of rare-earth element. However, the rare-earth element is a concept containing Y. T is at least one kind of transition-mental element. The magnet is used in spindle motors for hard disk drives. The specified size of the hard disk drive is equal to or less than 1 inch. COPYRIGHT : (C)2006, JPO&NCIPI