Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2000-07-03
2002-06-04
Dinh, Tan (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C369S013260
Reexamination Certificate
active
06400654
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a magnetic recording device and a magnetic recording and reproducing device which perform magnetic recording in a recording medium by increasing the temperature thereof using a light beam, etc., and to a method of performing such magnetic recording.
BACKGROUND ART
In the field of optical memory elements, in addition to read-only memories such as the compact disk, recent years have seen the development of recordable memories. Of these, memory elements such as the magneto-optical disk have already been put to practical use.
Such a magneto-optical disk in practical use is a recording medium which uses a perpendicularly magnetized film such as a thin film of a rare earth-transition metal alloy. Information is recorded therein by applying an external magnetic field while projecting laser light thereon. Reproducing from such a magneto-optical disk, on the other hand, makes use of the so-called Kerr effect, in which, when laser light is projected onto the magneto-optical disk, the direction of rotation of the polarization plane of light reflected therefrom changes depending on the presence or absence of recorded information.
With regard to recording and reproducing methods for other types of recording media, one conventional method which has been proposed is a recording and reproducing method for a recording medium made of ferromagnetic material of, for example, CrO
2
. In this recording and reproducing method, recording is performed by reducing coercive force by projecting laser light onto the recording medium and applying an external magnetic field thereto using a magnetic recording head, and reproducing is performed magnetically using a magnetic reproducing head.
However, in the foregoing recording and reproducing method, since the magnetic reproducing head is used to magnetically reproduce information, information cannot be reproduced from tracks narrower than the width of the magnetic reproducing head (its width in the track width direction, i.e., perpendicular to the track direction).
Therefore, methods such as the following have been proposed for recording and reproducing using tracks narrower than the magnetic head width, and for preventing crosstalk from adjacent tracks.
Japanese Unexamined Patent Publication No. 4-95201/1992 (Tokukaihei 4-95201) discloses a recording and reproducing method using a recording medium made of ferrimagnetic material. In this method, during recording, the temperature of a track of the recording medium to be recorded is increased to the vicinity of its Curie temperature by projecting a light beam along the track, and information is recorded in the track by using a magnetic recording head to apply an external magnetic field thereto. During reproducing, domains opposite the magnetic reproducing head on both sides of a track of the recording medium to be reproduced are heated to the vicinity of the magnetic compensation temperature thereof by projecting light beams onto those domains, and the magnetic reproducing head performs reproducing magnetically.
Further, Japanese Unexamined Patent Publication No. 4-176034/1992 (Tokukaihei 4-176034) discloses a recording and reproducing method using a recording medium made of ferrimagnetic material having a compensation point substantially at room temperature. In this method, during recording, the temperature of a track of the recording medium to be recorded is increased to the vicinity of its Curie temperature by projecting a light beam along the track, and information is recorded in the track by using a magnetic recording head to apply an external magnetic field thereto. During reproducing, magnetization of a domain to be reproduced is increased by projecting a light beam along a track of the recording medium to be reproduced, and a magnetic reproducing head performs reproducing magnetically.
However, in each of the foregoing conventional recording and reproducing methods, due to the influence of a temperature distribution at the recorded bit during recording, the recorded marks are in the form of crescents. For this reason, when using an ordinary magnetic head, increasing linear recording density is likely to lead to crosstalk between adjacent recorded bits in the track direction, and reproducing signal power is also decreased, making accurate reproducing difficult.
A method of resolving the foregoing problems which has been proposed in the past is to perform reproducing using a reproducing head of shape like a crescent. However, manufacture of a crescent-shaped reproducing head leads to further problems, such as complicating the manufacturing process and increasing manufacturing costs.
DISCLOSURE OF THE INVENTION
The present invention was made in view of the foregoing problems with the conventional art, and it is an object hereof to provide a magnetic recording device and a magnetic recording method which are capable of suppressing crosstalk and realizing higher recording density than conventionally. Another object of the present invention is to provide a magnetic recording and reproducing device capable of suppressing crosstalk and realizing higher recording density than conventionally.
(i) In order to attain the foregoing object, a magnetic recording device according to the present invention performs recording using a recording medium having a recording layer made of ferrimagnetic material, and comprises a magnetic head, which applies an external magnetic field to the recording medium during recording; and local temperature increasing means (such as a laser light source), which increase the temperature of the recording medium in a domain thereof opposite the magnetic head but excluding a domain for recording (such as the track to be recorded).
The recording medium made of ferrimagnetic material has a magnetic compensation point, and coercive force increases with increase in temperature. At the magnetic compensation point, residual magnetization is zero, and coercive force is infinite. Accordingly, as specified above, during recording, the local temperature increasing means locally increase the temperature of the domain of the recording medium opposite the magnetic head but outside the domain for recording, so as to give the surrounding domain a greater coercive force than the domain for recording. Then the magnetic head applies to the domain opposite the magnetic head a magnetic field greater than the coercive force of the domain for recording (i.e., its coercive force at room temperature), and smaller than the coercive force in the domain of increased temperature. Thus it is possible to record information accurately in the domain for recording.
At this time, the domain whose temperature is increased by the local temperature increasing means is a domain other than the domain for recording. Accordingly, when recording information using the foregoing magnetic recording device, the temperature distribution rarely extends to the actual domain for recording. For this reason, if the foregoing magnetic recording device is used, the shape of the recorded marks can be made substantially rectangular, thus reducing crosstalk.
Further, since information was conventionally recorded at the Curie temperature, the domain for recording was the area of increased temperature. For this reason, conventionally, the size of the recorded domain was equivalent to the width of the local temperature increasing means (the diameter of a light beam spot, track width of a heater, etc.).
With the present invention, in contrast, since the area whose temperature is increased by the local temperature increasing means is not the actual domain for recording, but the surrounding domain, the size of the domain for recording is not limited by the diameter of the light beam spot.
(ii) In the foregoing magnetic recording device, the domain whose temperature is increased by the local temperature increasing means is preferably made up of domains adjacent to the domain for recording, on both sides thereof.
When the domain for recording is one side of a domain of the recording medium opposite the magn
Katayama Hiroyuki
Sawamura Shinzo
Dike Bronstein Roberts & Cushman
Dinh Tan
Intellectual Property Practice Group of Edwards & Angell, LLP
Sharp Kabushiki Kaisha
LandOfFree
Magneto-optical recording and reproducing device capable of... 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 and reproducing device capable of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magneto-optical recording and reproducing device capable of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2972617