Dynamic magnetic information storage or retrieval – Head – Gap spacer
Reexamination Certificate
2001-02-05
2004-03-16
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Gap spacer
Reexamination Certificate
active
06707642
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to longitudinal magnetic recording heads, and more particularly relates to longitudinal recording heads with reduced side fringing for recording at high densities.
BACKGROUND INFORMATION
Magnetic hard disk drives incorporating longitudinal recording heads are well known. However, conventional longitudinal recording heads suffer from the disadvantage that at high recording densities the track density must be increased (with a corresponding decrease in bit aspect ratio), which requires a very narrow head. In particular, a track width cannot be defined which is smaller than the head track width plus approximately two times the gap length of the head in conventional designs. This limitation results from side fringing magnetic fields which spread at a distance on the order of the gap length from the both track sides across the track. Decreasing the gap length should reduce this characteristic side fringing region. However, as the gap length is decreased, the magnetic fields in the region of recording media along the track are also reduced. For example, at a 50 nm gap length, the maximum in-plane field component at a 10 nm flying height is less than 10,000 Oe, assuming a high moment (4&pgr;M
S
~20 kG) pole tip material is used. This field is not sufficient to record transitions clear enough for such high densities. At such high densities recording media are expected to have dynamic coercivity above 5,000 Oe, and approximately two times the coercivity is required to record sufficiently defined transitions. Therefore, there is a trade-off in decreasing the gap length.
U.S. Pat. No. 5,621,595 to Cohen, which is incorporated herein by reference, discloses a magnetic recording head with a pinched gap which is said to reduce side fringing magnetic fields in the gap region. However, the design of the pinched gap results in saturation in the pinched region, which can result in significant side fringing fields during operation. Furthermore, the pinched gap design is extremely sensitive to write currents.
The present invention has been developed in view of the foregoing, and to address other deficiencies of the prior art.
SUMMARY OF THE INVENTION
The present invention provides a thin-film recording head which minimizes side fringing. Side fringing is reduced by wrapping one of the write poles around the gap at the air bearing surface (ABS) while controlling the geometry of the wrapped around sides. A portion of the wrapped around sides of the write pole away from the air bearing surface may saturate during writing, while the sides at the air bearing surface carry a magnetic field below the saturation level of the pole material. Side fringing is thereby reduced without saturating the wrapped around sides at the ABS.
An aspect of the present invention is to provide a longitudinal recording head for use with a magnetic recording medium. The recording head includes first and second write poles defining a gap therebetween. Sides of the second write pole are wrapped around a portion of the first write pole. Magnetic flux is propagated through the wrapped around sides of the second write pole such that a portion of the wrapped around sides of the second pole located at an air bearing surface of the recording head do not saturate when portions of the wrapped around sides located away from the air bearing surface saturate. Another aspect of the present invention is to provide a longitudinal recording head for use with a magnetic recording medium which includes a first write pole and a second write pole defining a gap between the first and second write poles. Sides of the second pole are wrapped around a portion of the first pole, and the wrapped around sides have a cross sectional area located at an air bearing surface of the recording head that is greater than a cross sectional area located away from the air bearing surface.
These and other aspects of the present invention will be more apparent from the following description.
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Khizroev et al., U.S. Utility patent application Ser. No. 09/755,730, Entitled “Gapless Longitudinal Magnetic Recording Head with Flux Cavity”, Filed Jan. 5, 2001.
Khizroev et al., U.S. Utility patent application Ser. No. 10/031,320, Entitled “Longitudinal Magnetic Recording Heads with Variable-Length Gaps”, Filed Jan. 17, 2002.
Cao Allen
Pietragallo Bosick & Gordon
Seagate Technology LLC
Towner, Esq. Alan G.
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