A motor has a stator (4) and a rotor (3), the stator (4) having cores (9A) and drive coils (1) which generate magnetic fields for rotating the rotor (3). The stator (4) also has a yoke (9B,9C) surrounding the rotor (3) and the rotor (3) is positioned such that it is closer to one part (9B) of the outer periphery of the yoke than another part (9B) of the yoke. Such a motor is particularly suitable for use in a disk drive unit as a spindle motor (2) for rotating the disk (1). Then an actuator (12) for moving a head (11) may be located adjacent the part (9B) of the outer periphery of the yoke (9b,9C) which is closest to the rotor. This permits the head (11) to approach closely the axis of rotation of the disk (1) without the spindle motor (2) interfering with the movement of the head (11). The continuous yoke (9B,9C) prevents magnetic flux leakage from the spindle motor interfering with the actuator (12). The actuator (12) may itself have a yoke (9D) integral with the yoke (9B,9C) of the spindle motor (2), and/or other components in common.