Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2003-02-11
2004-10-19
Pianalto, Bernard (Department: 1762)
Stock material or miscellaneous articles
Composite
Of metal
C101S034000, C204S471000, C427S123000, C427S127000, C427S128000, C427S129000, C427S130000, C427S131000, C427S132000, C427S133000, C427S250000, C427S259000, C427S261000, C427S265000, C427S270000, C427S272000, C427S275000, C427S282000, C427S299000, C427S307000, C427S383100, C427S404000, C427S443100, C427S585000, C428S692100, C428S900000
Reexamination Certificate
active
06805966
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and devices for forming magnetic transition patterns in a layer or body of magnetic material. The invention has particular utility in the formation of servo patterns in the surfaces of magnetic recording layers of magnetic data/information storage and retrieval media, e.g., hard disks.
BACKGROUND OF THE INVENTION
Magnetic recording media are widely used in various applications, e.g., in hard disk form, particularly in the computer industry for storage and retrieval of large amounts of data/information in magnetizable form. Such media are conventionally fabricated in thin film form and are generally classified as “longitudinal” or “perpendicular”, depending upon the orientation (i.e., parallel or perpendicular) of the magnetic domains of the grains of the magnetic material constituting the active magnetic recording layer, relative to the surface of the layer.
A portion of a conventional thin-film, longitudinal-type recording medium
1
utilized in disk form in computer-related applications is schematically depicted in FIG.
1
and comprises a non-magnetic substrate
10
, typically of metal, e.g., an aluminum-magnesium (Al—Mg) alloy, having sequentially deposited thereon a plating layer
11
, such as of amorphous nickel-phosphorus (NiP), a polycrystalline underlayer
12
, typically of chromium (Cr) or a Cr-based alloy, a magnetic layer
13
, e.g., of a cobalt (Co)-based alloy, a protective overcoat layer
14
, typically containing carbon (C), e.g., diamond-like carbon (“DLC”), and a lubricant topcoat layer
15
, typically of a perfluoropolyether compound applied by dipping, spraying, etc.
In operation of medium
1
, the magnetic layer
13
is locally magnetized by a write transducer or write head (not shown in
FIG. 1
for simplicity) to record and store data/information. The write transducer creates a highly concentrated magnetic field which alternates direction based on the bits of information being stored. When the local magnetic field applied by the write transducer is greater than the coercivity of the recording medium layer
13
, then the grains of the polycrystalline medium at that location are magnetized. The grains retain their magnetization after the magnetic field applied by the write transducer is removed. The direction of the magnetization matches the direction of the applied magnetic field. The pattern of magnetization of the recording medium can subsequently produce an electrical response in a read transducer, allowing the stored medium to be read.
A typical recording system
20
utilizing a thin-film, vertically oriented, perpendicular-type magnetic medium
1
′ is illustrated in
FIG. 2
, wherein reference numerals
10
,
11
,
12
A,
12
B and
13
′, respectively, indicate the substrate, plating layer, soft magnetic underlayer, at least one non-magnetic interlayer, and vertically oriented, hard magnetic recording layer of perpendicular-type magnetic medium
1
, and reference numerals
7
and
8
, respectively, indicate the single and auxiliary poles of single-pole magnetic transducer head
6
. Relatively thin interlayer
12
B (also referred to as an “intermediate” layer), comprised of one or more layers of non-magnetic materials, serves to (1) prevent magnetic interaction between the soft underlayer
12
A and the hard recording layer
13
′ and (2) promote desired microstructural and magnetic properties of the hard recording layer. As shown by the arrows in the figure indicating the path of the magnetic flux &phgr;, flux &phgr; is seen as emanating from single pole
7
of single-pole magnetic transducer head
6
, entering and passing through vertically oriented, hard magnetic recording layer
13
′ (which, as is known, may comprise a Co-based alloy, an iron oxide, or a multilayer magnetic superlattice structure) in the region above single pole
7
, entering and travelling along soft magnetic underlayer
12
A for a distance, and then exiting therefrom and passing through vertically oriented, hard magnetic recording layer
13
′ in the region above auxiliary pole
8
of single-pole magnetic transducer head
6
. The direction of movement of perpendicular magnetic medium
1
past transducer head
6
is indicated in the figure by the arrow above medium
1
.
With continued reference to
FIG. 2
, vertical lines
9
indicate grain boundaries of each polycrystalline (i.e., granular) layer of the layer stack constituting medium
1
. As apparent from the figure, the width of the grains (as measured in a horizontal direction) of each of the polycrystalline layers constituting the layer stack of the medium is substantially the same, i.e., each overlying layer replicates the grain width of the underlying layer. Not shown in the figure, for illustrative simplicity, are a protective overcoat layer
14
, such as of a diamond-like carbon (DLC) formed over hard magnetic layer
13
′, and a lubricant topcoat layer
15
, such as of a perfluoropolyethylene material, formed over the protective overcoat layer. As with the longitudinal-type recording medium
1
shown in
FIG. 1
, substrate
10
is typically disk-shaped and comprised of a non-magnetic metal or alloy, e.g., Al or an Al-based alloy, such as Al—Mg having an Ni—P plating layer
11
on the deposition surface thereof, or substrate
10
is comprised of a suitable glass, ceramic, glass-ceramic, polymeric material, or a composite or laminate of these materials; soft underlayer
12
A is typically comprised of an about 500 to about 4,000 Å thick layer of a soft magnetic material selected from the group consisting of Ni, NiFe (Permalloy), Co, CoZr, CoZrCr, CoZrNb, CoFe, Fe, FeN, FeSiAl, FeSiAlN, etc.; thin interlayer
12
B typically comprises an up to about 100 Å thick layer of a non-magnetic material, such as TiCr; and hard magnetic layer
13
′ is typically comprised of an about 100 to about 250 Å thick layer of a Co-based alloy including one or more elements selected from the group consisting of Cr, Fe, Ta, Ni, Mo, Pt, V, Nb, Ge, and B, iron oxides, such as Fe
3
O
4
and &dgr;-Fe
2
O
3
, or a (CoX/Pd or Pt)
n
multilayer magnetic superlattice structure, where n is an integer from about 10 to about 25, each of the alternating, thin layers of Co-based magnetic alloy is from about 2 to about 3.5 Å thick, X is an clement selected from the group consisting of Cr, Ta, B, Mo, and Pt, and each of the alternating thin, non-magnetic layers of Pd or Pt is about 1 Å thick. Each type of hard magnetic recording layer material has perpendicular anisotropy arising from magneto-crystalline anisotropy (1
st
type) and/or interfacial anisotropy (2
nd
type).
A typical contact start/stop (CSS) method employed during use of disk-shaped media involves 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 mutually 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 is freely movable 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.
Adverting to
FIG. 3
, shown therein, in simplified, schematic plan view, is a magnetic recording disk
30
(of either longitudinal or perpendicular type) 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 relativel
Formato Christopher
Gui Jing
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