Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Patent
1996-11-08
2000-05-09
Dinh, Tan
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
428694MM, G11B 1100
Patent
active
060613076
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optomagnetic recording medium, a recording/reproducing system for optomagnetic recording medium, and a recording/reproducing apparatus for optomagnetic recording medium, and more particularly to the laminated structure of a magnetic layer of an optomagnetic recording medium in which a multi-valued recording is possible, a multi-valued recording system which uses such an optomagnetic recording medium, and the construction of a magnetic head which is suitable for multi-valued recording for an optomagnetic recording medium.
BACKGROUND ART
In the field of optomagnetic recording media, the improvement of a recording density is one of the most important technical subjects. As means for improving the recording density of an optomagnetic recording medium is hitherto proposed a system in which a signal is recorded with multi values. The multi-valued recording system is disclosed by, for example, 13th-Lecture Abstracts of the Society of Applied Magnetism of Japan (1989), p. 63 or Japanese Journal of Applied Physics, Vol. 28 (1989) Supplement 28-3, pp. 343-347.
In the known multi-valued recording system, a plurality of magnetic layers having different coercive forces are laminated and the intensity of a magnetic field applied to the magnetic layers is modulated multi-stepwise to invert the magnetization of a specified magnetic layer selectively. It is said that according to this system, the 4-valued recording of a signal becomes possible with the provision of three magnetic layers having different coercive forces.
In the known multi-valued recording system, however, when an optomagnetic recording medium is irradiated with a laser beam at the time of recording of a signal so that the temperature of each magnetic layer is raised up to the vicinity of its Curie temperature, there is little difference in coercive force between the magnetic layers. Therefore, it is actually difficult to cause the selective inversion of the magnetization of each magnetic layer. Even if the selective inversion of the magnetization of each magnetic layer is possible in a laboratory level by strictly adjusting the magnetic characteristic of each magnetic layer while strictly controlling a laser intensity and an external magnetic field intensity at the time of recording, the mass production of such optical recording media and recording/reproducing apparatuses is impossible from the aspect of cost. Also, since margins for changes in laser intensity and external magnetic field intensity at the time of recording become remarkably small, it is impossible to maintain a stable recording/reproducing state for a long time and hence there is no practicability by any possibility. If the recording of a signal is performed in a state in which the temperature of each magnetic layer is not raised up to the vicinity of the Curie temperature or a difference in coercive force between the magnetic layers is sufficiently large, the above inconvenience will not be encountered but a large magnetic field is necessitated for the recording and erasion of a signal. This brings about another serious inconvenience that a magnetic field generating device such as a magnetic head and hence a recording/reproducing apparatus become large in size and a power consumption is increased. In this case too, therefore, the practisation is actually impossible.
In the following, the inconveniences of the prior art will be explained in more detail on the basis of FIGS. 142A, 142B, 142C and 142D. For facilitating the explanation, the following explanation will now be made taking as an example an optomagnetic recording medium in which two magnetic films (or magnetic layers) having their coercive force versus temperature characteristics represented by symbols A and B in FIG. 142B are laminated on a substrate.
(1) The temperature of a portion irradiated with a recording laser beam is raised up to a temperature equal to or higher than the Curie temperature of each magnetic layer or in the vicinity thereof. Therefore, even if a differen
REFERENCES:
patent: 4938915 (1990-07-01), Saito
patent: 5159584 (1992-10-01), Yanagida et al.
patent: 5278809 (1994-01-01), Ogata
patent: 5398219 (1995-03-01), Itoh et al.
patent: 5440531 (1995-08-01), Sato et al.
patent: 5449566 (1995-09-01), Fujii et al.
Digests of the 13th annual conference on Magnetics in Japan 1989 (13), pp. 62-64, No month available.
Proceedings of the International Symposium on Optical Memory, Kobe, 1989 (E1803), pp. 343-347, No month available.
S. Tsunashima, Exchange Coupled Films for Magnetooptic Recording Applications, IEEE Translation Journal on Magnetics in Japan, vol. 7, No. 8, Aug. 1992.
Patent Abstracts of Japan, vol. 015, No. 327 (P-1240) Aug. 20, 1991 (JP 03 119538 A).
Patent Abstracts of Japan, vol. 013, No. 424 (P-934), Sep. 21, 1989 (JP 01 155533 A).
Patent Abstracts of Japan, vol. 015, No. 469 (P-1281), Nov. 27, 1991 (JP 03 201232 A).
Patent Abstracts of Japan, vol. 013, No. 191 (P-867), May 9, 1989 (JP 01 017248 A).
Patent Abstracts of Japan, vol. 018, No. 330 (P-1758), Jun. 22, 1994 (JP 06 076390 A).
Ishitsuka Kazuko
Ishizaki Osamu
Ohnuki Satoru
Ohta Norio
Sakemoto Akito
Dinh Tan
Hitachi Maxell Ltd.
LandOfFree
Magneto-optical recording medium having a plurality of magnetic does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magneto-optical recording medium having a plurality of magnetic , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magneto-optical recording medium having a plurality of magnetic will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1071744