Dynamic magnetic information storage or retrieval – Head – Head surface structure
Reexamination Certificate
1998-03-30
2003-01-14
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head surface structure
Reexamination Certificate
active
06507454
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to recording heads, and particularly to inductive heads having magnetic poles separated by a trimmed gap.
In the magnetic disc recording art, sliders are used to “fly” transducing heads at a design distance from the recording media. The slider usually includes rails having air-bearing surfaces to react against an air cushion formed by the rotating adjacent magnetic disc. The transducing head is typically fabricated into the slider and exposed to the trailing edge of a rail at the air-bearing surface. Cavities and other aerodynamic features on the slider cooperate to cause the head to be positioned the design distance from the rotating media.
The “width” of a magnetic head is defined by the radial width of the transducer, in relation to the adjacent track on the media. The “length” of the transducer is defined as the distance between the opposing ends of the sensor along the length of the adjacent track; the length being orthogonal to the width. In an inductive head, such as a write head or inductive read head, the width and length of the head is determined by the width and length of the transducing gap. Both the gap length and gap width are defined on the air-bearing surface of the slider. Control of the gap width is important, particularly in write heads where the gap width defines the width of the track being written. In read heads, the gap width is also important, since the width of the gap in a read head should be less than the width of the recorded track to minimize the risk of reading data from adjacent tracks simultaneously. However, the gap width of a read head should also be as wide as possible, within the bounds of the track, to maximizing recovered signal strength. Likewise, the length of a gap is important, since gap length affects recording density and strength.
Typically, the width of the gap in an inductive head is defined by recesses on each side of the intended gap. The recesses extend across the gap material and into the poles at each end (along the length) of the gap. Typically the recesses are etched into the air-bearing surface by ion etching with a focused ion beam. The focused ion beam removes a small amount of material approximately 0.2 microns in diameter. The beam is rastered back and forth across the region being etched to form recesses in the air-bearing surface. The recesses are in the form of rectangular troughs having very sharp features, including sharp internal corners and square edges. The recesses, being adjacent the gap, minimize magnetic flux outside the edges of the gap width, thereby minimizing the writing data outside the track on the disc (in the case of a write head). In the case of a read head, the recesses minimize the ability of the head to pick up stray flux from adjacent tracks. Thus, the recesses define the gap width.
One problem with present techniques of forming recesses adjacent the gap concerns the rastering of the ion beam. Ion milling requires highly precise machines and a considerable amount of time. The amount of time required by the ion milling process is directly related to the amount of material removed by the ion milling beam. The cost of manufacturing the recording head is directly related to the amount of time required to mill the recesses, and hence the amount of material milled. It is estimated that if the amount of material milled could be reduced by one-third, the cost per slider could be reduced by approximately $0.02. A facility manufacturing one million sliders per day could save up to $20,000.00 per day.
Accordingly, there is a need for a more efficient technique for forming the recesses defining the gap width of an inductive head.
BRIEF SUMMARY OF THE INVENTION
A slider according to the present invention includes an inductive magnetic head having first and second magnetic poles separated by a gap. The first and second poles and gap are supported on the slider with the gap having a gap length extending between the poles. A recess in the air bearing surface extends into at least the first magnetic pole and has a first portion having a length parallel to the gap length to define a gap width orthogonal to the gap length. The first portion of the recess has a curved depth defining a curved profile along its length.
In one embodiment, the magnetic head is a write head having a coil for carrying a write current so that the first and second poles and coil generate a write magnetic field having a write field strength in the confronting magnetic media, the write field strength being greater than a minimum media switching strength. The curved profile of the recess is arranged to shape the magnetic field strength in the magnetic media confronting the recess to a relatively flat profile along the length of the recess that is smaller than the minimum media switching strength.
In another embodiment, the recess has a second portion extending into the air bearing surface. The second portion of the recess has a length orthogonal to the gap length and a depth defining a curved profile along its length and intersecting the air bearing surface remote from the gap.
One aspect of the present invention resides in a process of forming recesses in the slider to define the gap width. More particularly, a slider is provided having a planar air bearing surface and first and second magnetic poles separated by a gap in the plane of the air bearing surface. The gap has a gap length extending between the poles. A first portion of a recess is etched into the air bearing surface adjacent the gap along a length parallel to the gap length and extending into at least the first magnetic pole. The first portion defines a gap width orthogonal to the gap length. The etching of the first portion forms a curved depth defining a curved profile along the length of the first portion.
In one embodiment of the process, the magnetic head is a write head having a coil for carrying a write current so that the first and second poles and coil generate a write magnetic field having a write field strength in the confronting magnetic media, the write field strength being greater than a minimum media switching strength. The etching of the curved profile of the recess is arranged to shape the magnetic field strength in the magnetic media confronting the recess to a relatively flat profile along the length of the recess that is smaller than the minimum media switching strength.
In another embodiment, the process includes etching a second portion of the recess into the air bearing surface along a length orthogonal to the gap length, the etching of the second portion forming a curved depth defining a curved profile along the length and width of the second portion.
REFERENCES:
patent: 4984118 (1991-01-01), Springer
patent: 5057956 (1991-10-01), Muratomi et al.
patent: 5402295 (1995-03-01), Suzuki et al.
patent: 5615069 (1997-03-01), Slade et al.
patent: 5675461 (1997-10-01), Aylwin et al.
patent: 5726841 (1998-03-01), Tong et al.
patent: 5850326 (1998-12-01), Takano et al.
patent: 3-78105 (1991-04-01), None
Berkowitz Jeffery K.
Meyer Dallas W.
Simpson Edward M.
Slade Steven B.
Evans Jefferson
Kinney & Lange , P.A.
Seagate Technology LLC
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