To reduce the cost of the magnet of magnetic circuits with opposing permanent
magnets by ensuring that inexpensive magnets having a low coercive force can be
used without substantial loss of magnetism caused by demagnetization fields, there
is provided a magnetic circuit with opposing permanent magnets, comprising: a pair
of permanent magnet units opposing each other across a gap, the pair of permanent
magnets being magnetized in thickness direction, wherein each of the permanent
magnet units comprises at least two types of permanent magnet pieces with different
coercive forces, and wherein, the permanent magnet piece that receives the largest
demagnetization force when the permanent magnet units are manufactured has a larger
coercive force than at least one other type of the permanent magnet piece; a yoke
magnetically coupled to the permanent magnet units, and provided outside of the
permanent magnet units and the gap; and a pair of pole pieces each arranged on
a gap side of an opposing surface of each of the permanent magnet units and having
a peripheral projection in opposing direction.
