PROBLEM TO BE SOLVED: To provide a dipole ring magnetic circuit having a high magnetic field strength and demagnetization resistance.SOLUTION: A dipole ring magnetic circuit 1 comprises a plurality of permanent magnet pieces 3 arranged annularly so that the magnetization direction is rotated in semicircle, and a substantially one-way magnetic field 9 is generating with uniform intensity in an internal space 7 surrounded by the permanent magnet pieces 3. More than one permanent magnet piece 3 has a magnetization direction 4 which makes an angle of 150-210 degrees with respect to the direction of the uniform magnetic field 9 on a plane perpendicular to the central axis of the annular shape (hereinafter, referred to "specific magnet piece"). At least in the specific magnet pieces 3a, 3b, 3c, the closer to the internal space in the radial direction of the annular shape, the higher the value of magnetic coersive force.COPYRIGHT: (C)2012,JPO&INPIT【課題】高い磁場強度と減磁耐性を有するダイポールリング磁気回路を提供する。【解決手段】半周で磁化方向が一回転するように環状に配列された複数の永久磁石片3を備え、該永久磁石片3で囲まれた内部空間7に実質的に一方向の磁場9を均一な強度で発生している磁気回路1であって、前記永久磁石片3の2つ以上が環状形状の中心軸に対して垂直な面上、前記均一磁場9の方向に対して磁化方向4が150度~210度の角度をなし(以下、「特定磁石片」という)、少なくとも前記特定磁石片3a、3b、3cにおいて、前記環状形状の径方向に沿って前記内部空間に近いほど保磁力の値が高くなっている、ダイポールリング磁気回路。【選択図】 図1
