Abstract: In a magnetic head, at least its upper insulating layer is formed of a resin having a glass transition temperature of 70° C. to 100° C., a porous material, or polyimide, or the ABS is polished at a high temperature, so when the temperature increases, a deformation, which can reduce a decrease in floating height, an increase in the danger of crash, and an increase TA on the part of a magnetic disk apparatus, does not occur on the ABS side.

Abstract: An objective lens for focusing a laser beam onto an optical information medium is disclosed. The objective lens comprises a lens body and a flange portion arranged on the periphery of the lens body. The surface of the lens body facing the optical information medium is formed with a convex shape having a radius of curvature R as follows: 0.05 m<R<0.5 m. In this way, a dynamic pressure is generated due to the convex-shaped surface and the rotation of the optical disk. This generates a buoyancy which overcomes the maximum acceleration of the objective lens. In this manner, it becomes possible to avoid collision of the objective lens with the optical information medium even in the presence of relative tilts, such as tangential tilts, radial tilts, and shift tilts, between the optical information medium and the objective lens.

Abstract: A magnetic disk for writing and reading information by a contact reading method comprises a plurality of asperities upon the surface of the disk. For extending the life of the disk by reducing wear, the plurality of asperities are fabricated such that the average radius of curvature of the plurality of asperities is greater than one thousand times the maximum height of the plurality of asperities on the surface. This ratio between the radius of curvature of the asperities and the surface relief of the asperities ensures a smooth surface and an extended wear life for the magnetic disk.

Abstract: A disk drive apparatus comprises a disk for recording data and a drive motor for rotating the disk. The disk has obverse and reverse sides, a center hole, an unlevel portion with an uneven flatness on the obverse and reverse sides, situated around the center hole, and a level portion situated outside the unlevel portion and having level surfaces on the obverse and reverse sides. The disk is mounted on a hub of the motor such that the hub is passed through the center hole. The hub has at its one end a supporting portion facing the level portion of the disk. A disk retainer, having a press portion facing the level portion of the disk, is attached to the other end of the hub so as to press the disk toward the supporting portion.

Abstract: According to the present invention, there is provided a magnetic disk memory system.