| 摘要 |
A method of producing a cylindrical permanent magnet having a multipole surface anisotropy. The method comprises the steps of: preparing a metal mold cooperating with a lower punch in defining therein a cylindrical compacting cavity, the metal mold being provided in the inner peripheral surface thereof with field coils corresponding in number to the number of the magnetic poles of the magnet to be produced; charging the compacting cavity with a ferromagnetic powder having a magnetic anisotropy; energizing the field coils to impart a magnetic anisotropy to the ferromagnetic powder while compacting the powder between an upper punch and the lower punch to form a compact; demagnetizing the formed compact followed by a firing; and magnetizing the fired compact in the same direction as the anisotropy. The method is characterized in that the field coils produce pulse magnetic field the intensity of which is not smaller than 3.5x103 ampere-turn/m when measured at the outer peripheral surface of the compacting cavity, thereby attaining a multipole surface anisotropy on the compact.
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