Coating processes – Direct application of electrical – magnetic – wave – or... – Ion plating or implantation
Reexamination Certificate
2001-10-12
2004-06-22
Pianalto, Bernard (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Ion plating or implantation
C427S128000, C427S129000, C427S130000, C427S131000, C427S132000, C427S255400, C427S256000, C427S282000, C427S331000, C427S399000, C427S533000, C427S548000, C427S599000
Reexamination Certificate
active
06753043
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application discloses subject matter similar to subject matter disclosed in U.S. patent application Ser. No. 09/912,065, filed on Jul. 25, 2001.
FIELD OF THE INVENTION
The present invention relates to thermally stable, high coercivity, high area density, patterned magnetic recording media, and to a method for manufacturing same. The invention has particular applicability in the fabrication of thermally stable, high areal density media with integrally formed servo patterns.
BACKGROUND OF THE INVENTION
Thin film magnetic recording media, e.g., in hard disk form, are conventionally employed for storing large amounts of data/information in magnetizable form. Referring now to
FIG. 1
, shown therein, in simplified, schematic cross-sectional view, is a portion of a dual-sided, thin-film magnetic disk medium
1
of the type contemplated by the present invention, comprising a substantially rigid, non-magnetic substrate
10
, typically comprised of an aluminum (Al) alloy, e.g., Al—Mg. Alternative materials for use as substrate
10
include glass, ceramics, glass-ceramics composites and laminates, polymers, and other non-magnetic metals and alloys. Al-based substrate
10
is provided, in sequence, at both major surfaces, with a polished and/or textured amorphous Ni-P underlayer
12
, a polycrystalline seed layer
14
, typically a Cr-based layer deposited by sputtering, a magnetic layer
16
comprised of a ferromagnetic material, e.g., an oxide or a Co-based alloy, a protective overcoat layer
18
, typically of a diamond-like carbon (DLC) material, and a lubricant topcoat layer
20
, e.g., of a fluorine-containing polymer.
Adverting to
FIG. 2
, shown therein, in simplified, schematic plan view, is a magnetic recording disk
30
having a data zone
34
including a plurality of servo tracks, and a contact start/stop (CSS) zone
32
. A servo pattern
40
is formed within the data zone
34
, and includes a number of data track zones
38
separated by servo tracking zones
36
. The data storage function of disk
30
is confined to the data track zones
38
, while servo tracking zones
36
provide information to the disk drive which allows a read/write head to maintain alignment on the individual, tightly-spaced data tracks.
Although only a relatively few of the servo tracking zones are shown in
FIG. 2
for illustrative simplicity, it should be recognized that the track patterns of the media contemplated herein may include several hundreds of servo zones to improve head tracking during each rotation of the disk. In addition, the servo tracking zones need not be straight radial zones as shown in the figure, but may instead comprise arcs, intermittent zones, or irregularly-shaped zones separating individual data tracks.
In operation of such disk-type media, a typical contact start/stop (CSS) method involves use of a floating transducer head gliding at a predetermined distance from the surface of the disk due to dynamic pressure effects caused by air flow generated between the sliding surfaces of the transducer head and the disk. During reading and recording (writing) operations, the transducer head is maintained at a controlled distance from the recording surface, supported on a bearing of air as the disk rotates, such that the transducer head can be freely moved in both the circumferential and radial directions, thereby allowing data to be recorded and retrieved from the disk at a desired position in a data zone.
In conventional hard disk drives, data is stored in terms of bits along the data tracks. In operation, the disk is rotated at a relatively high speed, and the magnetic head assembly is mounted on the end of a support or actuator arm, which radially positions the head on the disk surface. If the actuator arm is held stationary, the magnetic head assembly will pass over a circular path on the disk, i.e., over a data track, and information can be read from or written to that track. Each concentric track has a unique radius, and reading and writing information from or to a specific track requires the magnetic head to be located above that track. By moving the actuator arm, the magnetic head assembly is moved radially on the disk surface between tracks. Many actuator arms are rotatable, wherein the magnetic head assembly is moved between tracks by activating a servomotor which pivots the actuator arm about an axis of rotation. Alternatively, a linear actuator may be used to move a magnetic head assembly radially inwardly or outwardly along a straight line.
To record information on the disk, the transducer creates a highly concentrated magnetic field in close proximity to the magnetic recording medium. During writing, the strength of the concentrated magnetic field directly under the write transducer is greater than the coercivity of the recording medium, and grains of the recording medium at that location are magnetized in a direction which matches the direction of the applied magnetic field. The grains of the recording medium retain their magnetization after the magnetic field is removed. As the disk rotates, the direction of the writing magnetic field is alternated, based on bits of the information being stored, thereby recording a magnetic pattern on the track directly under the write transducer.
On each track, eight “bits” typically form one “byte” and bytes of data are grouped as sectors. Reading or writing a sector requires knowledge of the physical location of the data in the data zone so that the servo-controller of the disk drive can accurately position the read/write head in the correct location at the correct time. Most disk drives use disks with embedded “servo patterns” of magnetically readable information. The servo patterns are read by the magnetic head assembly to inform the disk drive of track location. In conventional disk drives, tracks typically include both data sectors and servo patterns and each servo pattern typically includes radial indexing information, as well as a “servo burst”. A servo burst is a centering pattern to precisely position the head over the center of the track. Because of the locational precision needed, writing of servo patterns requires expensive servo-pattern writing equipment and is a time consuming process.
A conventional approach to the servo-sensing problem comprises the use of mechanical voids or depressions in the magnetic layer between tracks formed by stamping or otherwise physically marking a pattern on the disk to function as servo patterns. A magnetic material layer is then applied at a constant thickness over the entire disk surface. When this type of disk is used, the distance from the magnetic head to magnetic material in the depressions is further than the distance from the magnetic head to magnetic material in the data track. The increased distance both reduces the strength of the signal from the depressions and reduces the contribution from the depressions to the magnetic field sensed by the read/write head.
While the depressions or voids formed in the disk are helpful in increasing track density, they tend to reduce the tribological performance of the disk assembly. For example, during operation of the magnetic recording medium, the slider no longer travels over a smooth surface and thus causes several mechanical performance drawbacks. These drawbacks include modulation of fly height when encountering servo patterns, fly height perturbations due to topographical changes from the track width definition, glide defects from the stamping process, and disk distortion due to the servo patterning process. Therefore, it is considered preferable to provide the servo pattern without incurring variations in surface topography.
Several approaches to forming servo-patterns are disclosed in the prior art. For example, U.S. Pat. No. 6,153,281 and U.S. Pat. No. 5,858,474, both to Meyer et al., disclose a magnetic medium having permanently defined boundaries between data tracks and a constant surface smoothness. The servo-patterns may be formed, at least in part, by a variety of techniques including
Kuo David S.
Li Xinwei
Pianalto Bernard
Seagate Technology LLC
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