Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-11-07
2003-12-02
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S690000, C428S900000, C427S128000, C427S129000, C427S130000, C264S430000, C264S483000, C204S192200, C204S192340, C204S192100
Reexamination Certificate
active
06656614
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for texturing substrate surfaces by means of ion implantation processing, e.g., substrates utilized in the manufacture of magnetic recording media, and to magnetic media obtained thereby. The invention has particular utility in texturing the CSS landing zone of hard disk magnetic media such as are employed in computer-related applications.
BACKGROUND OF THE INVENTION
Hard disk-type magnetic media are widely utilized in various applications, particularly in the computer industry. A conventional longitudinal recording, hard magnetic disk-type medium
1
commonly employed in computer-related applications is schematically depicted in
FIG. 1
, and comprises a substantially rigid, non-magnetic metal substrate
10
, typically of an aluminum (Al) alloy, such as an aluminum-magnesium (Al—Mg) alloy, having sequentially deposited thereon a plating layer
11
, such as of amorphous nickel-phosphors (Ni—P); an amorphous seed layer
12
A, e.g., of NiAl; a polycrystalline underlayer
12
B, 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”) formed, as is known, by sputtering of a carbon target in an appropriate atmosphere or by ion beam deposition (“IBD”) utilizing appropriate precursor gases; and a lubricant topcoat layer
15
, typically of a perfluoropolyether compound applied, as is known, by dipping, spraying, etc. The magnetic layer
13
, typically comprised of a Co-based alloy, may be formed by sputtering techniques and includes polycrystallites epitaxially grown on the polycrystalline Cr or Cr-based alloy underlayer
12
B.
In operation of medium
1
, the magnetic layer
13
can be locally magnetized by a write transducer, or write “head”, to record and thereby store information therein. The write transducer or head creates a highly concentrated magnetic field which alternates direction based on the bits of information to be stored. When the local magnetic field produced by the write transducer is greater than the coercivity of the material of the recording medium layer
13
, the grains of the polycrystalline material at that location are magnetized. The grains retain their magnetization after the magnetic field applied thereto by the write transducer is removed. The direction of the magnetization matches the direction of the applied magnetic field. The magnetization of the recording medium layer
13
can subsequently produce an electrical response in a read transducer, or read “head”, allowing the stored information to be read.
Thin film magnetic recording media are conventionally employed in hard disk form for use with disk drives for storing large amounts of data in magnetizable form. Typically, one or more disks are rotated about a central axis in combination with data transducer heads. In operation, a typical contact start/stop (“CSS”) method commences when the transducer head, carried by an air-bearing slider, begins to slide against the surface of the disk as the disk begins to rotate. Upon reaching a predetermined high rotational speed, the head floats in air at a predetermined distance from the surface of the disk due to dynamic pressure effects caused by the air flow generated between the sliding surface of the head and the disk. During reading and recording 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 head can be freely moved in both the circumferential and radial directions, allowing data to be recorded on and retrieved from the disk at a desired position. Upon terminating operation of the disk drive, the rotational speed of the disk decreases and the head again begins to slide against the surface of the disk and eventually stops in contact with and pressing against the surface of the disk. Thus, the transducer head contacts the disk surface whenever the disk is stationary, accelerated from the static position, and during deceleration just prior to completely stopping. Each time the head and disk assembly is driven, the sliding surface of the head repeats the cyclic sequence consisting of stopping, sliding against the surface of the disk, floating in air, sliding against the surface of the disk, and stopping.
The air bearing design for the head slider/transducer utilized for CSS-type operation as described above provides an interface between the slider and the disk which prevents damage to the disk over the life of the disk/slider/transducer head system, and provides damping in the event the disk drive system undergoes mechanical shock due to vibrations of external origin. The air bearing also provides the desired spacing between the transducer and the disk surface. A bias force is applied to the slider by a flexure armature in a direction toward the disk surface. This bias force is counter-acted by lifting forces from the air bearing until an equilibrium state is achieved. The slider will contact the disk surface if the rotating speed of the disk is insufficient to cause the slider to “fly”, as during startup and shut-down phases of the CSS cycle. If the slider contacts a data region of the disk, the data may be lost and the disk permanently damaged.
Referring now to
FIG. 2
, shown therein in simplified, schematic perspective view, is a conventionally configured magnetic hard disk
30
having a CSS (i.e., “landing”) zone
36
and a data (i.e., recording) zone
40
. More specifically,
FIG. 2
illustrates an annularly-shaped magnetic hard disk
30
including an inner diameter
32
and an outer diameter
34
. Adjacent to the inner diameter is an annularly-shaped, inner CSS or “landing” zone
36
. When disk
30
is operated in conjunction with a magnetic transducer head (not shown in the drawing), the CSS or “landing” zone
36
is the region where the head makes contact with the disk surface during the above-described start-stop cycles or other intermittent occurrences. In
FIG. 2
, the radially outer edge of the CSS or “landing” zone
36
is indicated by line
38
, which is the boundary between CSS zone
36
and data zone
40
where information in magnetic form is stored within the magnetic recording medium layer of disk
30
.
It is generally considered desirable for reliably and predictably performing reading and recording operations, and essential for obtaining high areal density magnetic recording, that the transducer head be maintained as close to the disk surface as possible in order to minimize its flying height. Thus, a smooth disk surface is preferred, as well as a smooth opposing surface of the transducer head, thereby permitting the head and the disk to be positioned in very close proximity, with an attendant increase in predictability and consistent behavior of the air bearing supporting the transducer head during motion. However, if the head surface and the recording surface are too flat, the precision match of these surfaces gives rise to friction and “stiction”, i.e., a combination of friction and “stickiness” (resulting from viscous shear forces) at the disk surface which causes the transducer head to adhere to the surface, particularly after periods of non-use, thereby making it more difficult for the transducer head to initiate movement therefrom. Excessive stiction and friction during the start-up and stopping phases of the above-described cyclic sequence causes wear of the transducer and disk
25
surfaces, eventually leading to what is referred to as “head crash”. Another drawback associated with smooth disk surfaces is lack of durability resulting from the very small amount of lubricant which is retained thereon. Thus, there are competing goals of minimizing transducer head flying height (as by the use of smooth surfaces) and reducing transducer head/disk friction (as by avoiding use of smooth surfaces).
Conventional practices for addressing these apparent competing objectives include providing at least the CSS or “lan
Gui Jing
Li Xinwei
Ma Xiaoding
Tang Huan
Kiliman Leszek
McDermott & Will & Emery
Seagate Technology LLC
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