Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
1997-07-25
2001-01-16
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S336000, C428S690000, C428S690000, C428S900000
Reexamination Certificate
active
06174597
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording apparatus using a dispersed magnetic recording medium.
In recent years, the recording information amount has increased along with the improvement in performance of computers, digitization of image and audio information, and the improvement in image quality. With the spread of small-size computers, storage devices have been downsized. As a result, a higher recording/reproduction ability is required of such devices particularly in the use of hard disks.
Realization of a high recording density of a magnetic recording medium such as a hard disk requires a magnetic recording layer having a large coercive force. For example, thin magnetic films formed from a Co-based alloy such as CoNiCr and CoCrM (M=Ta, Pt) have large coercive forces due to large magnetocrystalline anisotropy. These thin magnetic films, however, have strong medium noise. The medium noise is caused by a strong magnetic interaction which acts between crystal grains when the thin magnetic film forms a stable magnetic domain. As a reproduction head, a magnetoresistive head (MR head) and a giant magnetoresistive head (GMR head) such as a spin valve have been used because of high sensitivities. Although the system noise is reduced by using such a high-sensitivity reproduction head, the influence of the medium noise of the magnetic recording medium becomes more prominent. Therefore, reducing the medium noise becomes more and more important.
To reduce the medium noise, the use of a dispersed magnetic recording medium in which magnetic grains are dispersed in a nonmagnetic matrix is examined. In the dispersed magnetic recording medium, a reduction in medium noise is expected because the exchange interaction between magnetic grains is reduced by the nonmagnetic matrix present between the magnetic grains. However, in the dispersed magnetic recording medium, a yet further reduction in medium noise is demanded, and a further improvement is required in this respect.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a low-noise magnetic recording apparatus having a dispersed magnetic recording medium.
According to the present invention, there is provided a magnetic recording apparatus comprising a magnetic recording medium comprising a substrate and a magnetic recording layer formed on the substrate and having a structure in which magnetic grains are dispersed in a nonmagnetic matrix, means for recording magnetic information on the magnetic recording medium, and means for reproducing magnetic information from the magnetic recording medium wherein the magnetic grains are separated from the substrate by a part of the matrix and form a substantially single layer parallel to a main surface of the substrate.
According to the present invention, there is provided another magnetic recording apparatus comprising a magnetic recording medium comprising a substrate and a magnetic recording layer formed on the substrate and having a structure in which magnetic grains are dispersed in a nonmagnetic matrix, means for recording magnetic information on the magnetic recording medium, and means for reproducing magnetic information from the magnetic recording medium wherein the magnetic grains have a flat shape along a film surface, and an exchange interaction between adjacent magnetic grains in an in-plane direction is smaller than that in a perpendicular direction.
According to the present invention, there is provided still another magnetic recording apparatus comprising a magnetic recording medium comprising a substrate and a magnetic recording layer formed on the substrate and having a structure in which magnetic grains are dispersed in a nonmagnetic matrix, means for recording magnetic information on the magnetic recording medium, and means for reproducing magnetic information from the magnetic recording medium wherein the magnetic grains include island-like magnetic grains, and an average value of angles defined by side surfaces of the island-like magnetic grains and a surface of the substrate is not more than 75°.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
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Ichihara Katsutaro
Kikitsu Akira
Nakamura Futoshi
Ogiwara Hideo
Yusu Keiichiro
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Kiliman Leszek
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