Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
1998-09-24
2001-04-17
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S336000, C428S690000, C428S900000
Reexamination Certificate
active
06218003
ABSTRACT:
TECHNICAL FIELD
The present invention relates to magnetic recording media, such as thin film magnetic recording disks. The present invention has particular applicability to high areal density magnetic recording media exhibiting low noise, high remanent coercivity and reduced recording signal modulation.
BACKGROUND ART
The requirement for increasingly high areal recording density imposes increasingly greater demands on thin film magnetic recording media in terms of remanent coercivity (Hr), magnetic remanance (Mr), coercivity squareness (S*), medium noise, i.e., signal-to-noise ratio (SNR), and narrow track recording performance. Efforts to produce a magnetic recording medium satisfying such demanding requirements confront significant challenges.
The linear recording density can be increased by increasing the coercivity of the magnetic recording medium. However, this objective can only be accomplished by decreasing the medium noise, as by maintaining very fine magnetically non-coupled grains. Medium noise is a dominant factor restricting increased recording density of high density magnetic hard disk drives. Medium noise in thin films is attributed primarily to inhomogeneous grain size and intergranular exchange coupling. Accordingly, in order to increase linear density, medium noise must be minimized by suitable microstructure control.
A conventional longitudinal recording disk medium is depicted in FIG.
1
and comprises a substrate
10
, typically an aluminum (Al)-alloy, such as an Al-magnesium (AlMg) alloy, plated with a layer of amorphous nickel-phosphorus (NiP). Alternative substrates include glass, ceramic and glass-ceramic materials, plastics, silicon, as well as graphite. There are typically sequentially sputter deposited on each side of substrate
10
an optional adhesion enhancement layer
11
,
11
′, e.g., chromium (Cr) or a Cr alloy, a seedlayer
12
,
12
′, such as NiP, an underlayer
13
,
13
′, such as Cr or a Cr alloy, a magnetic layer
14
,
14
′, such as a cobalt (Co)-based alloy, and a protective overcoat
15
,
15
′, such as a carbon-containing overcoat. Typically, although not shown for illustrative convenience, a lubricant topcoat is applied on the protective overcoat
15
,
15
′.
It is recognized that the magnetic properties, such as Hr, Mr, S* and SNR, which are critical to the performance of a magnetic alloy film, depend primarily upon the microstructure of the magnetic layer which, in turn, is influenced by the underlying layers, such as the underlayer. It is recognized that underlayers having a fine grain structure are highly desirable, particular for epitaxially growing fine grains of hexagonal close packed (HCP) Co alloys deposited thereon.
As the demand for high areal recording density increases, the requirements for high recording signal, low media noise and narrow transitions become increasingly difficult to simultaneously satisfy, thereby imposing great demands on film structure design and fabrication techniques. Efforts have been made to explore new types of magnetic and underlayer materials, design new multi-layer thin film structures and manipulate various thin film deposition parameters in attempting to improve magnetic properties and information read/write processes. However, there remains a need for increasingly high areal recording density magnetic recording media exhibiting Hr, high SNR, and narrow signal pulse.
DISCLOSURE OF THE INVENTION
An advantage of the present invention is a high areal recording density magnetic recording medium exhibiting low noise, high Hr and a narrow signal pulse.
Additional advantages and other features of the present invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following only to be learned from the practice of the present invention. The objects and advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to the present invention, the foregoing and other advantages are achieved in part by a magnetic recording medium comprising: a non-magnetic substrate; a first underlayer comprising chromium (Cr) or a Cr alloy, containing titanium dioxide (TiO
2
) dispersed therein; and a magnetic layer.
Another aspect of the present invention is a magnetic recording medium comprising: a glass, ceramic or glass-ceramic substrate, a first underlayer on the substrate, the first underlayer comprising Cr or a Cr alloy, containing TiO
2
dispersed therein; a second underlayer on the first underlayer, the second underlayer containing a Cr alloy; and a magnetic layer on the second underlayer.
Additional advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment of the present invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out the present invention. As will be realized, the present invention is capable of other and different embodiments, and its details are capable of modifications in various obvious respects, all without departing from the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.
REFERENCES:
patent: 5314745 (1994-05-01), Okumura
patent: 5456978 (1995-10-01), Lal
patent: 5681635 (1997-10-01), Nelson
patent: 5700593 (1997-12-01), Okumura
patent: 5789056 (1998-08-01), Bian
patent: 5800931 (1998-09-01), Lee
patent: 5851656 (1998-12-01), Ohkubo
patent: 5939202 (1999-08-01), Ataka
patent: 5983673 (1999-11-01), Xiong
Ranjan Rajiv Y.
Wu Zhong (Stella)
Kiliman Leszek
McDermott & Will & Emery
Seagate Technology LLC
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