Bacon & Thomas
Radial anisotropic ring magnet with a sinusoidal waveform and producing method thereof
 A magnet is formed as a ring magnet and magnetized by radial application of a magnetic field while the intensity of the magnetic field is changed periodically along the circumference of the ring magnet to give a circumferentially sinusoidal waveform distribution of magnetic flux density to the ring magnet in the magnetized state of the magnet. 
Daido Tokushuko Kabushiki Kaisha
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H01F Y10S H02K H02K H01F
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Yasuaki Hiyoshi Norio
Kasai Yamada Yoshikawa