US Patent 7616406 Disk apparatus and magnet for magnetic circuit

A rotary type actuator comprises an actuator assembly rotatably attached to a base and supporting a head at an end thereof via an arm and supporting a coil at the other end thereof, and a magnetic circuit unit having a yoke and a magnet secured to the base. The latch mechanism has a projection arranged from the inner periphery of the magnet provided in the magnetic circuit toward the rotational center and a latching magnet which produces an attraction force directed toward the latch position caused by leaking magnetic flux between itself and the projection near the latch position where the actuator assembly is in contact with the stopper and holds it at the latch position.