Magnetic disk drive

Details Magnetic disk drive Magnetic disk drive

1998-11-20

2001-06-12

Ometz, David L. (Department: 2754)

Dynamic magnetic information storage or retrieval

Record medium

Disk

Reexamination Certificate

active

06246544

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk drive and, more particularly, to a magnetic disk drive including a magnetoresistive (MR) device.
In a magnetic disk drive having a dense recording capability, a magnetic head records or reproduces data in or out of a magnetic disk while flying several nanometers (nm) above the disk. To further promote dense recording with such a disk drive, it is necessary to reduce a spacing between the head and the disk. To meet this requirement, U.S. Pat. No. 5,041,932 and Japanese Patent Application Nos. 7-65795, 8-055869 and 8-150968, for example, each discloses a system for recording data in a magnetic disk with a magnetic head contacting the disk. The system uses a three-pad slider in the mass domain of a head currently used in a flying head type recording system, and uses a lubricant. Particularly, U.S. Pat. No. 5,041,932 teaches that a magnetic head device is implemented by an induction type magnetic head. However, the current trend in the flying head type recording system is toward an MR head capable of further increasing the recording density.
An MR type magnetic head, however, brings about the following problems when recording or reproducing data in contact with the surface of a magnetic disk. When the disk includes a glass substrate, various faults ascribable to the sliding contact of the disk and including an increase in the resistance of an MR device and the damage of the device occur. The disk drive therefore lacks in durability. Further, when use is made of a magnetic disk customary with a flying head type recording system, sufficient contact and therefore dense recording cannot be implemented. Particularly, in the case of contact recording, the recording and reproducing characteristics are deteriorated due to the undulation of the disk. The flying head type recording system is not susceptible to the slow undulation of a disk other than the fine roughness of the disk.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication No. 6-28656.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a contact recording type magnetic disk drive capable of obviating electrical faults ascribable to the sliding contact of an MR head and a magnetic disk.
A magnetic disk drive of the present invention includes a magnetic recording med i um having a contact surface. A magnetic head includes a slider and an MR device. The slider contacts the contact surface of the medium before the MR device reproduces data out of the medium. The medium has a sheet resistance of less than 5 &OHgr;/cm
2
inclusive, as measured on the contact surface. The MR device is spaced from the contact surface by a recess of 15 nm. Alternatively, the MR device may be spaced from the contact surface of the medium by a recess of greater than 15 nm inclusive.


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