Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-01-10
2003-12-23
Letscher, George J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06667848
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to perpendicular magnetic recording heads, and more particularly relates to recording heads which include means for suppressing unwanted noise from the soft magnetic underlayer of the recording disk.
BACKGROUND INFORMATION
Perpendicular magnetic recording systems have been developed for use in computer hard disk drives. An approach to perpendicular magnetic recording requires the use of recording media with a magnetically soft underlayer which provides a flux path from the trailing pole to the leading pole of the writer. The soft underlayer enables substantially stronger fields than can be generated with a ring head in conventional longitudinal recording systems. The soft underlayer also provides sharper field gradients which enable writing on high coercivity media. In addition, the soft underlayer also helps during the read operation. During the read back process, the soft underlayer produces the image of magnetic charges in the magnetically hard layer, effectively increasing the magnetic flux coming from the media. This provides a higher playback signal.
One of the challenges of implementing perpendicular recording is to resolve the problem of soft underlayer noise. The noise is caused by fringing fields generated by magnetic domains, or uncompensated magnetic charges, in the soft underlayer that can be sensed by the reader. For the write process to be efficient, high moment materials, e.g., B
S
<20 kG, may be used for the soft underlayer. If the magnetic domain distribution of such materials is not carefully controlled, very large fringing fields can introduce substantial amounts of noise in the read element. Not only can the reader sense the steady-state distribution of magnetization in the soft underlayer, but it can also affect the distribution of magnetization in the soft underlayer, thus generating time-dependent noise. Both types of noise should be minimized.
The present invention has been developed in view of the foregoing.
SUMMARY OF THE INVENTION
The present invention provides a perpendicular magnetic recording head which magnetically biases the soft underlayer of the magnetic recording media. By forcing substantial magnetic flux into the body of the soft underlayer, the magnetic domain walls are effectively driven out of the soft underlayer, particularly in the region underneath the read-part of the recording head. The reduction or elimination of magnetic domain walls suppresses unwanted noise that would otherwise be caused by the domain walls.
An aspect of the present invention is to provide a perpendicular magnetic recording head including at least one magnetic recording element, and means for generating a magnetic field which reduces noise from a soft magnetic underlayer of a recording medium during operation of the magnetic recording element.
Another aspect of the present invention is to provide a perpendicular magnetic recording head including at least one magnetic recording element, and at least one noise-suppressing magnetic field generating element spaced apart from the magnetic recording element.
A further aspect of the present invention is to provide a perpendicular magnetic recording system. The system includes a perpendicular magnetic recording medium having a hard magnetic recording layer and a soft magnetic underlayer, and a perpendicular magnetic recording head positionable over the medium having at least one magnetic recording element and at least one magnetic field generating element positioned to generate a noise-suppressing magnetic field in the soft magnetic underlayer in a region of the medium under the recording element.
These and other aspects of the present invention will be more apparent from the following description.
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IBM Technical Disclosure Bulletin. “Perpendicular Recording Media with Patterned Magnetic Underlayer to Reduce Readback Signal Envelope Modulation.” Mar. 1987, IBM, vol. 29, Issue 10, pp. 4256-4266.*
Sharat Batra, U.S. Utility patent application Ser. No. 09/759,948, Perpendicular Magnetic Recording Head With Radial Magnetic Field Generator Which Reduces Noise From Soft Magnetic Underlayer of Recording Disk, filed Jan. 12, 2001.
Khizroev Sakhrat
Litvinov Dmitri
Beacham C. R.
Letscher George J.
Pietragallo Bosick & Gordon
Seagate Technology LLC
Towner, Esq. Alan G.
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