Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-03-04
2001-10-30
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S900000, C427S178000, C427S129000, C427S130000, C204S192200
Reexamination Certificate
active
06309765
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording medium suitable as a recording medium for a hard disc device and a process for producing it.
2. Discussion of Background
In recent years, magnetic recording media have been developed for high density recording. Accordingly, a medium having a low noise and being excellent in S/N, is required. Heretofore, as a means to obtain high coercive force, it has been reported to employ NiAl having B2 structure as a seed layer (IEEE TRANSACTIONS ON MAGNETICS, vol.30, pp3951-3953, No. 6, 1994, EP 0704839A1).
However, no mention is made in such a report about a change of the noise characteristics of a medium depending upon the oxygen content of the seed layer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a magnetic recording medium having a noise substantially reduced and being capable of high density recording, by selecting the oxygen content of a seed layer, and a process for its production.
The present invention has been made to accomplish the above object and provides a magnetic recording medium comprising a non-ferromagnetic substrate and a magnetic recording layer formed on the substrate with an underlayer of Cr or a Cr alloy interposed therebetween, which has a seed layer between the substrate and the underlayer, wherein said seed layer is made of a material which contains at least 30 ppm of oxygen and which has a B2 crystal structure.
REFERENCES:
patent: 5693426 (1997-12-01), Lee et al.
patent: 5846648 (1998-12-01), Chen et al.
patent: 6077603 (2000-06-01), Zhang
patent: 6110582 (2000-08-01), Wu
patent: 6117570 (2000-09-01), Chen
patent: 0 704 839 (1996-04-01), None
Li-Lien Lee, et al., “NiAI Underlayers For CoCrTa Magnetic Thin Films,” IEEE Transactions on Magnetics, vol. 30, No. 6, (Nov. 1994), pp. 3951-3953.
Hiruma Takehiko
Imakawa Makoto
Mitarai Kazuhiko
Suekane Michinobu
Asahi Komag Co., Ltd.
Kiliman Leszek
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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