Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
1999-10-01
2002-05-28
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C360S110000
Reexamination Certificate
active
06396774
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an information reproducing device which copies information magnetically recorded on an information recording medium, and an information reproducing method for reproducing information copied on the information reproducing device by utilizing the magneto-optical effect.
Recently, the recording density of magnetic recording and optical recording has been greatly increased and the recording and reproducing techniques have been developed; consequently, there have been ever-increasing demands for higher-density information recording. Here, various means for recording information on a recording medium using a magnetic film and for reproducing the information have been known. For example, in the case of a magnetic disk used as a recording medium, after information has been magnetically recorded, leakage flux from a recorded mark is detected by using a ring head or a thin-film head. Moreover, in the case of a magneto-optical disk used as a recording medium, after information has been magnetically recorded (in this case, particularly referred to as thermo-magnetic recording), a light beam which has been narrowed down to approximately its diffraction limit is emitted to the medium, and a change in the magneto-optical effect occurring in the magnetic film at this time is detected.
Moreover, another method has been proposed in which after information has been recorded on a recording medium using a magnetic film, an information reproducing device having a magnetic substance is brought close to the recording medium so as to copy the magnetization direction of the information, and a light beam which has been narrowed down to approximately its diffraction limit is emitted to the information reproducing device so that a change in the magneto-optical effect occurring in the magnetic substance is detected. In this method, the information recorded on the recording medium is copied on the information reproducing device, and then reproduced.
FIG. 1
is an explanatory drawing that shows a reproducing method using a conventional information reproducing device. This information reproducing device has been reported in “Signal Read-out Characteristic of Floating Magnetic Head Using Magnetic Garnet”, THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS, TECHNICAL REPORT OF IEICE, MR97-84, CPM97-176 (1998-03), p.
1-p.7.
In the Figure, the encircled portion shows an enlarged view. A reproducing head is placed on a face of a magnetic recording medium
14
having recording bits
15
in which information is magnetically recorded. The reproducing head is a floating magnetic head in which a slider section
10
is supported by a suspension
3
. The slider section
10
is constituted as follows: A magnetic garnet film
16
is formed on a GGG (gadolinium, gallium, garnet) substrate
18
through crystal growth, thereon is formed a reflection film
17
made of titanium and a protective film
19
made of SiO
2
. The slider section
10
faces the magnetic recording medium
14
on the protective film
19
side.
In this reproducing head, upon reproducing, a leakage magnetic flux from the magnetic recording medium
14
is copied onto the magnetic garnet film
16
with the result that respective magnetization directions maintained by recording bits
15
,
15
. . . are formed on the magnetic garnet film
16
. A laser beam is emitted onto the magnetic garnet film
16
so that copied information is reproduced by detecting a change in the magneto-optical effect. Since the magnetic garnet exhibits a great magneto-optical effect, a greater reproducing signal can be obtained by reproducing information from the magnetic garnet film
16
. However, the problem with this reproducing head is that in the case of recording wavelengths of not more than 2 &mgr;m, the amplitude of the reproducing signal drops greatly, failing to reproducing information recorded with a high density.
Moreover, Japanese Patent Application Laid-Open No. 62-75955 (1987) has suggested a magneto-optical recording/reproducing head using a garnet film. This magneto-optical recording/reproducing head has recording and reproducing functions, is provided with a head having the garnet film that exhibits in-plane magnetization, and copies or induces information from a magnetic recording medium. Then, by magneto-optically reproducing the magnetization direction of the garnet film, it is possible to obtain a reproduced signal with a high level. The information reproducing device using such a garnet film has been proposed by various other references (Japanese Patent Application Laid-Open No. 47-1244(1972), Japanese Patent Application Laid-Open No. 56-37839(1981), Japanese Patent Application Laid-Open No. 61-214260(1986), Japanese Patent Application Laid-Open No. 61-214261(1986), Japanese Patent Application Laid-Open No. 6-325422(1994), etc.).
In the case when the information reproducing device which uses the garnet having a high magneto-optical effect is used for magneto-optical reproduction, a reproduced signal having a high level is obtained; however, as described earlier, this device fails to reproduce information recorded with a high density. Moreover, none of the above-mentioned patent applications specifically disclose the dimension and the magnetic characteristics of the garnet film, and the dimension of the head, etc., making it difficult to put this device into practical use.
BRIEF SUMMARY OF THE INVENTION
The present invention has been devised to solve the above-mentioned problems, and one objective of the present invention is to provide an information reproducing device which can copy and reproduce information of an information recording medium that has been recorded with a high density by using a magnetic-substance chip having single-magnetic domain structure. Moreover, another objective of the present invention is to provide an information reproducing head, an information recording/reproducing head and an information reproducing method, which are allowed to reproduce information of an information recording medium that has been recorded with a high density by using such an information reproducing device.
An information reproducing device of the present invention faces to an information recording film so as to copy a magnetic flux to be reproduced, characterized by including a magnetic-substance chip having mono-magnetic domain structure.
The magnetic substance forms stripe magnetic domains, and has a specific magnetic domain width in a demagnetization state in accordance with composition of the magnetic substance. In the present invention, the dimension of the magnetic-substance chip in the magnetic-domain forming direction is set smaller than the above-mentioned specific magnetic domain width; therefore, the magnetic-substance chip has the mono-magnetic domain structure. Therefore, in the case when the width dimension of the magnetic-substance chip is greater than a recording mark formed on an information recording film, the magnetic flux of the recording mark formed on the information recording film is copied on the magnetic-substance chip in an enlarged manner during reproduction. Here, since the magnetic-substance chip forms only one magnetic domain over the entire area, it can detect, with high precision, a change in the magneto-optical effect at the time of an inversion in the magnetization direction. In this case, although the minimum recording mark formed on the information recording film has a smaller dimension than the magnetic-substance chip, an area which is determined by the temperature distribution of the information recording film and the inclination of the magnetic-substance chip to the information recording film during reproduction is copied onto the magnetic-substance chip.
The information reproducing device of the present invention is characterized in that the magnetic-substance chip is being formed into a predetermined dimension by etching a magnetic substance that has been grown on a substrate.
Therefore, since the crystal growth of the magnetic-substance is ma
Fujimaki Tohru
Matsumoto Koji
Fujitsu Limited
Greer Burns & Crain Ltd.
Huber Paul W.
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