Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-11-20
2004-02-10
Rickman, Holly (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S212000, C428S336000, C428S611000, C428S667000, C428S678000, C428S690000, C428S900000, C427S128000, C427S130000, C427S131000
Reexamination Certificate
active
06689496
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the benefit of a Japanese Patent Application No. 2000-107078 filed Apr. 7, 2000, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to magnetic recording media, methods of producing magnetic recording media and magnetic storage apparatuses, and more particularly to a magnetic recording medium which is suited for high-density recording, a method of producing such a magnetic recording medium, and a magnetic storage apparatus provided with such a magnetic recording medium.
2. Description of the Related Art
The recording density of longitudinal magnetic recording media such as magnetic disks has increased considerably due to the reduction of media noise and the development of magnetoresistive heads and spin valve heads. A typical magnetic recording medium has a stacked structure comprising a substrate, an underlayer, a magnetic layer and a protection layer which are stacked in this order. The underlayer is made of Cr or a Cr-based alloy, and the magnetic layer is made of a Co-based alloy.
A method of reducing the media noise is proposed in a U.S. Pat. No. 5,693,426, for example. According to this proposed method, an underlayer made of NiAl is used to control the crystal structure of the magnetic layer, so as to reduce the media noise and to improve the recording and reproducing characteristics such as the resolving power.
However, in order to cope with the recent demands to realize an even higher recording density, it has become necessary to further improve various characteristics of the magnetic recording medium. More particularly, it is necessary to further reduce the crystal grain size of the various layers including the magnetic layer, to accurately control the crystal grain size, and to improve the crystal orientation of the various layers.
In the conventional magnetic recording media, there is a problem in that it is difficult to further improve the coercivity and squareness ratio and to reduce media noise.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful magnetic recording medium, a method of producing the magnetic recording medium, and a magnetic storage apparatus, in which the problem described above is eliminated.
Another and more specific object of the present invention is to provide a magnetic recording medium, a method of producing the magnetic recording medium, and a magnetic storage apparatus, which can further improve the coercivity and squareness ratio and reduce the media noise.
Still another object of the present invention is to provide a magnetic recording medium comprising a substrate, a nonmagnetic seed layer provided on the substrate, and a magnetic layer provided on the nonmagnetic seed layer via one or a plurality of layers, where the nonmagnetic seed layer is made of NiAl having an oxygen concentration of approximately 1500 to 4000 ppm. According to the magnetic recording medium of the present invention, it is possible to improve the coercivity and squareness ratio, and to reduce the media noise of the magnetic recording medium.
A further object of the present invention is to provide a method of producing a magnetic recording medium having a nonmagnetic seed layer provided on a substrate, and a magnetic layer provided on the nonmagnetic seed layer via one or a plurality of layers, comprising the step of forming the nonmagnetic seed layer by growing NiAl at a temperature in a range of approximately 200° C. to 280° C. According to the method of the present invention, it is possible to realize a magnetic recording medium having improved coercivity and squareness ratio and reduced media noise.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
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Komura Haruhiro
Okamoto Iwao
Umeda Hisashi
Yoshida Yuki
Fujitsu Limited
Greer Burns & Crain Ltd.
Rickman Holly
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