Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-02-02
2003-05-13
Rickman, Holly (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S611000, C428S667000, C428S336000, C428S900000, C427S128000, C427S131000
Reexamination Certificate
active
06562488
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to magnetic recording media, such as thin film magnetic recording disks, and to a method of manufacturing the media. The invention has particular applicability to high areal density magnetic recording media exhibiting low noise, and high coercivity.
BACKGROUND
The increasing demands for higher areal recording density impose increasingly greater demands on thin film magnetic recording media in terms of remanant coercivity (Hr), magnetic remanance (Mr), coercivity squareness (S*), medium noise, i.e., signal-to-medium noise ratio (SMNR), and narrow track recording performance. It is extremely difficult to produce a magnetic recording medium satisfying such demanding requirements.
The linear recording density can be increased by increasing the Hr of the magnetic recording medium and by decreasing the medium noise, as by maintaining very fine magnetically non-coupled grains. Medium noise in thin films is a dominant factor restricting increased recording density of high-density magnetic hard disk drives, and 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.
It is recognized that the magnetic properties, such as Hr, Mr, S* and SMNR, which are critical to the performance of a magnetic alloy film, depend primarily upon the microstructure of the magnetic layer.
In order to increase Hr, magnetic alloys containing platinum (Pt), such as Co—Cr—Pt—tantalum (Ta) alloys have been employed. Although Pt enhances film Hr, it was found that Pt also increases media noise. Accordingly, it has become increasingly difficult to achieve high areal recording density while simultaneously achieving high SMNR and high Hr.
In copending U.S. patent application Ser. No. 09/496,342, filed Feb. 2, 2000, now U.S. Pat. No. 6,403,241, claiming priority from Provisional Application Serial No. 60/129,306 filed Apr. 14, 1999, entitled “CoCrPtB MEDIUM WITH A 1010 CRYSTALLOGRAPHIC ORIENTATION,” a magnetic recording medium is disclosed comprising a CoCrPtB magnetic layer.
A magnetic recording medium having a CoCrPtTaNb magnetic layer has been reported. Hideyuki Akimoto et al., “Magnetic Interaction in Co—Cr—Pt—Ta—Nb Media: Utilization of Micromagnetic Simulation,” IEEE Transactions an Magnetics, Vol. 34, No. 4, pp. 1597-1599, 1998. However, it was found that difficulties exist in identifying the intergranular exchange coupling constant (h
e
) via magnetic property measurements and transmission electron microscopy (TEM) observation of actual media. Also, Hideyuki does not disclose the use of B in the magnetic layer.
CoCrPtTaNb and CoCrPtB were used for magnetic recording media and were reported in the literature. Assignee's patent application Ser. No. 09/406,816, filed Sep. 18, 1999, now U.S. Pat. No. 6,461,750, entitled “Magnetic Recording Medium with Dual Magnetic Layer and High In-Plane Coercivity,” the entire disclosures of which are hereby incorporated herein by reference, disclosed a medium structure with CoCrPtTaNb alloy. Mrt is continuing to decrease from the current level, for higher areal density products, in order to support smaller inter-bit transitions.
There is a need to find a magnetic alloy, which features low noise and high coercivity (Hc) at low Mrt. There also exists a need for high areal density magnetic recording media exhibiting high Hr and high SMNR. There exists a need for magnetic recording media containing a glass or glass ceramic substrate exhibiting high Hr, and high SMNR.
SUMMARY OF THE INVENTION
An advantage of this invention is a magnetic recording medium for high areal recording density exhibiting low noise and high Hr.
Another advantage of this invention is a method of manufacturing a magnetic recording medium suitable for high areal recording density and exhibiting low noise and high Hr.
Additional advantages and features of this invention will be set forth in part in the description that follows and in part will become apparent to those having ordinary skill in the art upon examination of the following description and from the knowledge gained by practicing the invention. The advantages of this invention may be realized and obtained and are particularly pointed out in the claims.
According to this invention, the foregoing and other advantages are achieved by a magnetic recording medium comprising a substrate and a magnetic layer comprising Co, Cr and B and at least 3 other elements. A 6-element magnetic layer gave certain advantages over recording media having 4-element magnetic layers.
Another aspect of this invention is a method of manufacturing a magnetic recording medium, comprising depositing a sub-seed layer on a substrate; depositing a seed layer on the sub-seed layer, an underlayer on the seed layer; an intermediate layer on the underlayer and depositing a magnetic layer on the intermediate layer. The magnetic layer comprises Co, Cr and B and at least 3 other elements.
Additional advantages of this invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiments of this invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out this invention. As will be realized, this invention is capable of other and different embodiments, and its details are capable of modifications in various obvious respects, all without departing from this invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.
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Akimoto H., et al., IEEE Transactions on Magnetics (1998), 34(4):1597-1599.
Chen Qixu (David)
Harkness, IV Samuel Dacke
Huang Lin
Leu Charles
Ranjan Rajiv Yadav
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