Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2002-12-17
2004-10-19
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06807027
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of electronic data storage and retrieval systems. In particular, the present invention relates to a perpendicular write pole of a transducing head having a nonmagnetic seedlayer.
In an electronic data storage and retrieval system, a transducing head typically includes a writer for storing magnetically-encoded information on a magnetic disc and a reader for retrieving that magnetically-encoded information from the magnetic disc. The reader typically consists of two shields and a magnetoresistive (MR) sensor positioned between the shields. Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor. This change in resistivity of the MR sensor can be detected by passing a current through the MR sensor and measuring a voltage across the MR sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary.
The writer typically consists of two magnetic poles, or a magnetic core, separated from each other at an air bearing surface (ABS) of the write head by a write gap and connected to each other at a region away from the ABS. Positioned between the two poles are one or more conductive coil layers encapsulated by insulating layers. The writer and the reader are often arranged in a merged configuration in which a shared pole serves as both a shield in the reader and a magnetic pole in the writer.
The magnetic poles can be deposited by either a sputtering-type process or by electrodeposition. In the latter case, an electrically-conductive seedlayer upon which the magnetic pole can be plated through a photoresist mask is necessary to allow for metal ion reduction and hence, formation of the pole. Conventionally, the seedlayer is formed of a material that is also magnetically-conductive, such that the seedlayer becomes a magnetically-active part of the pole.
The writer can be arranged as either a longitudinal writer or a perpendicular writer. In either case, the general structure of the writer is similar, although the actual operation and dimensions of its elements will differ substantially. In a longitudinal writer, the poles are commonly referred to as a bottom pole and a top pole, while in a perpendicular writer, the poles are commonly referred to as a return pole and a main pole.
To write data to a longitudinal magnetic media, a time-varying electrical current, or write current, is caused to flow through the conductive coil. The write current produces a time-varying magnetic field through the top and bottom poles that bridges the write gap between the two poles at the ABS of the transducing head. The longitudinal magnetic media is passed near the ABS of the transducing head at a predetermined distance such that a magnetic surface of the media passes through the magnetic field. As the write current changes direction, the magnetic field changes in intensity and direction. This type of writer is referred to as a longitudinal writer because the generated magnetic field causes bits to be written to the magnetic media in the plane of the magnetic media.
A perpendicular magnetic media differs from a longitudinal magnetic media in the direction in which the magnetization in the recording surface is held. For a longitudinal media, the magnetization is held in a direction substantially parallel to the surface of the media, while for a perpendicular media, the magnetization is held in a direction substantially normal to the surface of the media. To enable data to be perpendicularly recorded, perpendicular media generally are formed of two layers: a soft magnetic underlayer having high permeability and a media layer having high perpendicular anisotropy.
To write data to the perpendicular magnetic media, a time-varying write current is caused to flow through the conductive coil, which in turn produces a time-varying magnetic field through the main pole and the return pole. The magnetic media is then passed near the ABS of the writer at a predetermined distance such that the media passes through the magnetic field. With a perpendicular writer, the main and return poles are spaced further apart than the top and bottom poles of the longitudinal writer, and the underlayer of the magnetic media in essence acts as a third pole of the writer; that is, the magnetic field bridges the gap from main pole to the underlayer, passing through the media layer, and then subsequently bridges the gap between the underlayer and return pole, again passing through the media layer. To ensure that the magnetic field does not write data on this return path, the return pole is substantially larger than the main pole at the ABS such that the magnetic field through the media layer will not be concentrated sufficiently to overcome the intrinsic magnetization of the media.
Perpendicular writers currently are being pursued as an option over longitudinal writers for increasing areal bit density of magnetic media. As described above, the main pole of a perpendicular writer is generally formed by plating a magnetic material through a photoresist mask, which in turn requires the deposition of an electrically-conductive seedlayer. Conventionally, this seedlayer is formed of a material that is also magnetically-conductive, such that the seedlayer becomes a magnetically-active part of the pole.
Importantly, when designing a perpendicular writer, a thickness of the main pole at the ABS is preferably minimized to diminish off-track writing at skew. Additionally, only a trailing edge of the main pole of a perpendicular writer contributes to the writing process. Thus, a thicker main pole will not improve the quality of the written data. Conventionally, a longitudinal writer will have a thickness in a range of about one micrometer to about two micrometers, while a perpendicular writer will have a thickness of less than about one micrometers. The conventional magnetic seedlayers upon which the main pole is plated, however, make it difficult to minimize the thickness of the main pole. Also, because the writer leaves an imprint of a shape of the main pole at the ABS on the media, a square-shaped main pole is preferred. Again, the conventional magnetic seedlayers contribute to the aspect ratio of the main pole, rendering the main pole less square in shape.
BRIEF SUMMARY OF THE INVENTION
A perpendicular write head includes a main pole, a return pole, and conductive coils. The main pole includes a seedlayer and a magnetic layer that is plated upon the seedlayer. The seedlayer is nonmagnetic, electrically conductive, and corrosion-resistant. The return pole is separated from the main pole by a gap at an air bearing surface of the write head and is coupled to the main pole opposite the air bearing surface. The conductive coils are positioned at least in part between the main pole and the return pole.
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Bell Alison Mary
Johnston Alan Biggar
McGeehin Peter Kevin Mark
Seagate Technology LLC
Tupper Robert S.
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