To reduce the leakage of magnetic flux from a permanent magnet to the outside by magnetizing each magnetic pole of an inner-periphery side to magnetic flux density that is higher than of each outer-periphery side.

Magnetic poles 114 and 115 that exist at the inner-periphery side of a permanent magnet 108 are magnetic poles for applying a magnetic flux to each of a space 104. For example, the magnetic poles 114 an 115 are N and S poles, respectively. The magnetic pole parts 114 and 115 are orientated so that a hard ferrite material in a forming material can generate a magnetic force and are magnetized to a magnetic flux density higher than that of outer- periphery sides 114' and 115', respectively. With a magnetic path 116 that exists inside the permanent magnet 108 for magnetically connecting the magnetic poles 114 and 115, those other than the magnetic poles 114 and 115 are all magnetic paths in the permanent magnets 108 other than the magnetic poles 114' and 115' are also included. In the magnetic path 116, a number of power- shaped hard ferrite materials are not aligned, and the magnetic flux densities are lower than those of the magnetic poles 114 and 115.