Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2002-04-25
2004-08-10
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C427S523000, C427S528000, C427S531000, C427S128000, C427S130000
Reexamination Certificate
active
06773556
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for forming thin film magnetic recording media containing magnetic particles with uniform barriers to magnetic reversal without significant sacrifice in signal-to-medium noise ratio (SMNR), and to magnetic media obtained thereby. The present invention is of particular significance or utility in the manufacture of thermally stable, high SMNR and hence high areal recording density magnetic recording media, suitable for use in computer-related applications, e.g., hard disks.
BACKGROUND OF THE INVENTION
Magnetic recording media and devices incorporating same are widely employed in various applications, particularly in the computer industry for data/information storage and retrieval applications, typically in disk form. Conventional thin-film type magnetic media, wherein a fine-grained polycrystalline magnetic alloy layer serves as the active recording layer, are generally classified as “longitudinal” or “perpendicular”, depending upon the orientation of the magnetic domains of the grains of magnetic material.
A portion of a conventional longitudinal recording, thin-film, hard disk-type magnetic recording medium
1
commonly employed in computer-related applications is schematically illustrated in
FIG. 1
in simplified cross-sectional view, and comprises a substantially rigid, non-magnetic metal substrate
10
, typically of aluminum (Al) or an aluminum-based alloy, such as an aluminum-magnesium (Al—Mg) alloy or a suitable glass, ceramic, glass-ceramic, or polymeric material, or a composite or laminate of these materials, having sequentially deposited or otherwise formed on a surface
10
A thereof a plating layer
11
, such as of amorphous nickel-phosphorus (Ni—P); a seed layer
12
A of an amorphous or fine-grained material, e.g., a nickel-aluminum (Ni—Al) or chromium-titanium (Cr—Ti) alloy; a polycrystalline underlayer
12
B, typically of Cr or a Cr-based alloy; a magnetic recording layer
13
, e.g., of a cobalt (Co)-based alloy with one or more of platinum (Pt), Cr, boron (B), etc.; a protective overcoat layer
14
, typically containing carbon (C), e.g., diamond-like carbon (“DLC”); and a lubricant topcoat layer
15
, e.g., of a perfluoropolyether. Each of layers
11
-
14
may be deposited by suitable physical vapor deposition (“PVD”) techniques, such as sputtering, and layer
15
is typically deposited by dipping or spraying.
In operation of medium
1
, the grains in the magnetic layer
13
are locally aligned by a write transducer, or write “head”, to record and thereby store data/information therein. While moving over the surface of medium
1
, 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 magnetization direction of the grains (i.e., single magnetic domain particles) of the polycrystalline material at that location is aligned in the direction of the applied magnetic field. The grains retain their alignment after the magnetic field applied thereto by the write transducer is removed. Thus the magnetization direction of the grains matches the direction of the magnetic field applied thereto. The magnetization pattern 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.
In perpendicular magnetic recording media, residual magnetization is formed in a direction perpendicular to the surface of the magnetic medium, typically a layer of a magnetic material on a suitable substrate. Very high linear recording densities are obtainable by utilizing a “single-pole” magnetic transducer or “head” with such perpendicular magnetic media.
A typical perpendicular recording system
20
utilizing a vertically oriented magnetic medium
21
with a relatively thick soft magnetic underlayer, a relatively thin hard magnetic recording layer, and a single-pole head, is illustrated in
FIG. 2
, wherein reference numerals
22
,
23
,
24
, and
25
, respectively, indicate the substrate, soft magnetic underlayer, at least one non-magnetic interlayer, and vertically oriented, hard magnetic recording layer of perpendicular magnetic medium
21
, and reference numerals
27
and
28
, respectively, indicate the single and auxiliary poles of single-pole magnetic transducer head
26
. Relatively thin interlayer
24
(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
23
and the hard recording layer
25
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
27
of single-pole magnetic transducer head
26
, entering and passing through vertically oriented, hard magnetic recording layer
25
in the region above single pole
27
, entering and travelling along soft magnetic underlayer
23
for a distance, and then exiting therefrom and passing through vertically oriented, hard magnetic recording layer
25
in the region above auxiliary pole
28
of single-pole magnetic transducer head
26
. The direction of movement of perpendicular magnetic medium
21
past transducer head
26
is indicated in the figure by the arrow above medium
21
.
With continued reference to
FIG. 2
, vertical lines
29
indicate grain boundaries of each polycrystalline (i.e., granular) layer of the layer stack constituting medium
21
. 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, such as of a diamond-like carbon (DLC) formed over hard magnetic layer
25
, and a lubricant topcoat layer, such as of a perfluoropolyethylene material, formed over the protective overcoat layer. Substrate
22
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 on the deposition surface thereof, or substrate
22
is comprised of a suitable glass, ceramic, glass-ceramic, polymeric material, or a composite or laminate of these materials; underlayer
23
is typically comprised of an about 2,000 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.; interlayer
24
typically comprises an up to about 100 Å thick layer of a non-magnetic material, such as TiCr; and hard magnetic layer
25
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 element 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).
Efforts are continually being made with the aim of increasing the areal recording density, i.e., the bit density, or bits/unit area, by increasing the signal-to-medium noise ratio (hereinafter “SMNR”) of the magneti
Brockie Richard Michael
Richter Hans Jurgen
McDermott Will & Emery LLP
McDonald Rodney G.
Seagate Technology LLC
LandOfFree
Method for energy barrier equalization of magnetic recording... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for energy barrier equalization of magnetic recording..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for energy barrier equalization of magnetic recording... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3268820