Apparatus for applying magnetic field and magneto-optical disk storage having such apparatus

A magneto-optical disk storage means comprising:

• an apparatus for providing a magnetic field of either polarity comprising:
• a permanent magnet which applies a magnetic field to a recording surface of a magneto-optical disk, the permanent magnet having an approximately cylindrical shape, said permanent magnet being pivotally supported along its axis, respective semicircular portions of the circular section of the permanent magnet being magnetized as north and south poles, said permanent magnet having a pair of opposing arcuate sides defined by a diameter of said circular section;
• a driving coil having a pair of spaced, loop portions positioned proximate to the exterior of said permanent magnet, each of said loop portions being positioned on the same side of said permanent magnet, the spacing of the loop portions being such that the arcuate distance from one loop portion to a corresponding point on the other loop portion along the circumference of said permanent magnet is less than 180.degree., said coil being formed such that a portion of said permanent magnet is embraced by said coil, the rotation and positioning of said permanent magnet, and hence the magnetic field provided by said apparatus, being controlled by one of the strength and direction of the current flowing in said driving coil;
• and
• an optical head which locally radiates a laser beam onto the recording surface of the magneto-optical disk.

A magneto-optical disk storage unit comprising:

• a pivotally supported permanent magnet, said permanent magnet having portions magnetized as north and south poles for applying a magnetic field of either polarity to a magneto-optic disk, the magnetic field being perpendicular to a recording surface of said magneto-optic disk;
• a driving coil located in the vicinity of said permanent magnet for electromagnetically engaging said permanent magnet;
• control means, coupled to said driving coil, for providing current pulses to said driving coil so that said permanent magnet is rotated by said electromagnetic engagement;
• and
• servo circuit means, coupled to said control means, for energizing said driving coil to maintain said permanent magnet stopped at a predetermined position when said permanent magnet is not being rotated by the current pulses from said control means.

A magneto-optical disk storage unit comprising:

• a pivotally supported permanent magnet, said permanent magnet having portions magnetized as north and south poles for applying a magnetic field of either polarity to a magneto-optic disk, the magnetic field being perpendicular to a recording surface of said magneto-optic disk;
• a driving coil located in the vicinity of said permanent magnet for electromagnetically engaging said permanent magnet;
• control means, coupled to said driving coil, for providing a current pulse to said driving coil so that said permanent magnet is rotated by said electromagnetic engagement;
• detection means for detecting an angular displacement of the permanent magnet;
• and
• braking means, coupled to said control means, for supplying a current pulse to said driving coil for a predetermined time period when an angular displacement detected by said detection means reaches a predetermined value, so that said permanent magnet experiences a torque in a direction opposite to a direction in which said permanent magnet is being rotated to bring the permanent magnet to a desired position.