JPH01319146A - Method and device for magneto-optical recording with magnetic field modulating system - Google Patents

Abstract

PURPOSE:To realize the magneto-optical recording of high density and low noise by changing the size of a modulating magnetic field, which is impressed with a magnetic head, in the local part of a magnetic thin film, which is heated with a light beam, and preventing magnetic field intensity from being uniform. CONSTITUTION:The heating area of a magnetic thin film 3 is dislocated from the central part of a magnetic head 1 only by a prescribed position and the magnetic field to have a gradient in the writing direction of information, namely, a moving direction 5 of a medium is impressed to an area, where a temperature is falling down, in the local part of the magnetic thin film 3. A modulating magnetic field impressed to the local part of the heated magnetic thin film 3 have an area, where the change of the magnetic field is sharp to the writing direction 5 of the information, to be the edge part of this modulating magnetic field. Then, a recording area 4 of the information, which are recorded to a magnetic thin film 3, is closed to a rectangular shape. Thus, since the recording area 4 is not overlapped, the recording of the high density and low noise can be achieved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magneto-optical recording method and apparatus using a magnetic field modulation method for recording information by changing the direction or magnitude of an applied magnetic field, and particularly relates to a magneto-optical recording method and apparatus that uses a magnetic field modulation method to record information by changing the direction or magnitude of an applied magnetic field. The present invention relates to a magneto-optical recording method using a magnetic field modulation method suitable for realizing magneto-optical recording of noise, and an apparatus for implementing the method.

[Conventional technology]

The third principle of the magneto-optical recording device using the conventional magnetic field modulation method
As shown in the figure. A local portion of a magnetic thin film 3 serving as a magneto-optical recording medium is heated by a light beam 2, and a uniform modulated magnetic field is applied to the local portion by a magnetic head 1. The magnetization of the heated magnetic thin film rlA3 is reversed depending on the direction of the modulated magnetic field, and the direction of magnetization is fixed by cooling the magnetic thin film and recorded as information. Magneto-optical recording using such a magnetic field modulation method is proposed in Japanese Patent Publication No. 60-1a&06.

[Problem to be solved by the invention]

In the above-described conventional magneto-optical recording device using the magnetic field modulation method, as shown in FIG. 5, for example, the shape of the recording area 4 reflects the temperature distribution during heating and cooling, and becomes crescent-shaped as shown in the figure. Therefore, when increasing the recording density in the information writing direction, the front and rear recording areas overlap, which hinders higher density. Well, since there is an acute angle part in the recording area 4, the domain wall energy in that part becomes high,
The shape of the recording area 4 tends to become unstable, causing noise.

An object of the present invention is to provide a magneto-optical recording method and apparatus using a magnetic field modulation method, which are suitable for solving the problems in the prior art described above and realizing high-density, low-noise magneto-optical recording. The object of the present invention is to provide a recording method and a device for carrying out the recording method.

[Means to solve the problem]

The above object of the present invention is achieved by recording by applying a non-uniform magnetic field to the area heated by the irradiation of the magnetic head light beam by utilizing the temperature characteristics of the magnetism and thin film in the magneto-optical recording medium. Ru.

That is, the present invention (1) shifts the heating region of the magnetic thin film 3 by a predetermined position from the center of the magnetic head 1, for example, as shown in FIGS. This is achieved by applying a magnetic field having a gradient to a localized portion of the heated magnetic thin film 3 where the temperature is decreasing.

The magneto-optical recording method using the magnetic field modulation method of the present invention includes a magnetic thin film serving as an information recording medium, a light beam that heats a local part on the magnetic thin film, and a light beam that heats a local part of the magnetic thin film heated by the light beam. In a method of performing magneto-optical recording using a magneto-optical recording device that includes at least a magnetic head that applies a modulated magnetic field, the magnitude of the modulated magnetic field applied by the magnetic head is such that the magnitude of the modulated magnetic field applied by the magnetic head is at a local portion of the magnetic thin film heated by the light beam. It is characterized by a variable magnetic field strength that is not uniform.

The modulated magnetic field application method in the magneto-optical recording method of the present invention has the following effects in the direction perpendicular to the information writing direction:
The magnitude of the modulated magnetic field applied over a sufficiently wider range than the size of the local portion of the heated magnetic thin film is uniform, and the modulated magnetic field applied in the information writing direction is It is characterized in that it is large in the high-temperature region immediately after heating in a localized portion of the thin film, and is small in the subsequent low-temperature region.

In the magneto-optical recording method of the present invention, the modulated magnetic field applied to a local portion of the heated magnetic thin film is as follows.

At the end of the modulated magnetic field, the change in the magnetic field has a steep slope with respect to the information writing direction, and the information recording area to be recorded on the magnetic thin film has a nearly rectangular shape. It is something to do.

The magneto-optical recording device using the magnetic field modulation method of the present invention includes a magnetic thin film serving as an information recording medium, a light beam that heats a local part on the magnetic thin film, and a light beam that heats a local part of the magnetic thin film heated by the light beam. comprising at least a magnetic head that applies a modulated magnetic field, and the intensity of the modulated magnetic field applied by the magnetic head changes in a local portion of the magnetic thin film heated by the light beam, giving non-uniform magnetic field strength;
At least an information writing means for forming an information recording area into a nearly rectangular shape, and an information reading means for reading out the information recorded by the information writing means using a transfer type magneto-optical head. It is characterized by:

[Effect]

In a magnetic thin film of a magneto-optical recording medium (in a temperature range above the compensation temperature, if one exists), the coercive force generally decreases as the temperature increases.

Therefore, magnetization is reversed only in the heated region of the magnetic thin film, allowing magneto-optical recording. The temperature distribution in the region heated by the light beam is, for example, as shown in the equimixture line 6 of the region heated by the light beam as shown in FIG. 4(a).

Then, when a magnetic field having the intensity distribution shown in FIG. 4(b) is applied to the heated region, for example, in the region where the modulated applied magnetic field is weak, the magnetization of only the high temperature portion is oriented in the direction of the applied magnetic field, and when the magnetic field is strong, In this region, the direction of magnetization is aligned in the direction of the applied magnetic field up to the low-temperature part, so the magnetization is aligned in the direction of the applied magnetic field, as shown in region 7, where the magnetization is aligned in the direction of the magnetic field, as shown in the shaded area in Figure 4 (a). . Therefore, the magnetic field can be modulated (on/off).
Recording area 4 created when turning off or reversing direction)
The shape is as shown in FIG. 4(c), and in the case of the conventional modulated magnetic field application method, it is a crescent shape as shown in FIG. 5, whereas in the present invention, it is a rectangular shape as shown in FIG. A recording area 4 close to 1 is formed. When the shape is close to a rectangle, the recording areas do not overlap, making it possible to achieve high-density recording.

〔Example〕

An embodiment of the present invention will be described below in more detail based on the drawings.

(Example 1) The basic configuration of this example is shown in FIG. magnetic head 1
For example, a single magnetic pole type head is used as the optical head 1, a semiconductor laser is used as the light beam 2, and the magnetic head and the semiconductor laser are arranged at opposing positions on opposite sides of the magneto-optical recording medium. At this time, the light beam 2 is shifted from the center of the magnetic head 1 so that the end of the magnetic head 1 is located in an area where the temperature is decreasing due to heating by the light beam 2.

In the magneto-optical recording medium, a magnetic thin film 3 is formed by sputtering on a transparent substrate 9 such as glass, and a protective film 8 is provided to prevent the magnetic thin film 3 from oxidizing. A groove (guide groove) for tracking is provided in advance on the transparent substrate 9. The light beam 2 was narrowed down to a spot with a diameter of 1.4 μI on the surface of the magnetic thin film 3 by a lens with a numerical aperture of 0.6, and the end of the magnetic head 1 was positioned to face the spot. The spot follows the eccentricity of the guide groove on the transparent substrate 9 and moves in a direction perpendicular to the moving direction 5 of the medium, but since the range of the magnetic field generated by the magnetic head 1 is sufficiently wide in that direction, The spot will be located at and act on the end of the magnetic head 1.

The size of the information recording area 4 written by this magneto-optical recording device is 0.7 μm in the radial direction, and the S density in the circumferential direction of the magneto-optical recording medium (the recording area 4 length) is determined by the recording frequency and is set to 0.5
It is possible to reduce the amount to less than μl. The shape of the recording area 4 is determined by the slope of the change in the magnetic field at the end of the applied magnetic field, and the steeper the change in the magnetic field in the recording area, the closer the shape of the recording area 4 becomes to a rectangle.

For reading (reading and reproduction), the same light beam as for writing (recording) is irradiated with low power, and detection is performed using the rotation of the polarization plane of the reflected light, that is, Kerr rotation.

(Example 2) In the above-mentioned Example 1, reading was performed using the same light beam as the writing light, but if a transfer type magneto-optical head is used, higher density recording can be realized.

As shown in FIG. 7, for writing, as in the first embodiment, a single-pole magnetic head 1 and a light beam 2 using a semiconductor laser are used.
Use. The magneto-optical recording medium is disk-shaped or tape-shaped, and a magnetic thin film 3 is formed by sputtering or coating on a transparent substrate 9 that is highly transparent to the writing light beam 2, and a protective film 8 is provided as necessary. . Note that it is preferable that the protective film 8 be thinner because the recording density can be increased.

For reading, magnetic transfer is performed on the magnetic transfer film 11 through a high magnetic permeability thin film having a thickness of 1000 mm. Magnetic transfer film 11
For this purpose, a material with a large Kerr rotation angle is used, and the Kerr rotation is detected by the light beam 2. It is also possible to share the magnetic head 1 for writing and the high magnetic permeability film 10 for reading.

When recorded using this magneto-optical recording device, 1 μen x 0.2
It is possible to form a recording area 4 of the order of .mu.-, and it is possible to realize magneto-optical recording with a high density of about 5 to 10 times that of conventional magneto-optical recording.

Although a single-pole head was used as the magnetic head in the above embodiment, other ring-type magnetic heads may also be used. It is sufficient that the modulated applied magnetic field is uniform over the entire range, and that the applied magnetic field is large in the high temperature part immediately after heating the medium and small in the subsequent low temperature part in the information writing direction. Furthermore, the configuration of the recording medium is not limited to the embodiment described above.

For example, as the transparent substrate 9, an acrylic or polycarbonate substrate can be used. A magneto-optical recording medium in which a dielectric film, a magnetic film, and a dielectric film are laminated in this order on the transparent substrate 9 can also be used. It is desirable to coat the uppermost layer of the magneto-optical recording medium with a suitable resin to prevent damage caused by collision with a magnetic head.

(Effect of the invention) FIG. 8 is a diagram showing the relationship between recording frequency (recording density), carrier wave (C), and noise (N). Conventional reproduction output 13
During high-frequency (high-density) recording, the carrier wave output decreases and noise increases; however, by using the modulated magnetic field application method of the present invention, the recording area of magneto-optical recording using the magnetic field modulation method can be shaped into a rectangular shape. Therefore, it is possible to realize magneto-optical recording with less noise (N) and less decrease in carrier-to-noise ratio (C/N) during high-density (high-frequency) recording.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of the configuration of a magneto-optical recording device using the magnetic field modulation method of the present invention, FIG. 2 is an explanatory diagram showing the principle of the modulated magnetic field application method of the present invention, and FIG. 3 is a conventional magnetic field modulation method. A schematic diagram showing the configuration of a magneto-optical recording device according to the method, FIG. 4 is an explanatory diagram showing the relationship between equimixing in the heating area by the light beam, magnetic field intensity distribution, and recording area in the present invention, and FIG. FIG. 6 is a schematic diagram showing the configuration of the magneto-optical recording device using the magnetic field modulation method exemplified in Example 1 of the present invention, and FIG. 8 is a schematic diagram showing the configuration of the magneto-optical recording device using the magnetic field modulation method illustrated in Example 2.
The figure is a graph showing the relationship between the reproduction output and the recording frequency of the magneto-optical recording device according to the embodiment of the present invention. 1...Magnetic head 2...Light beam 3...Magnetic thin film 4...Recording area 5...Movement direction of the medium 6...Equimixing of area heated by the light beam 7...Magnetic field Region 8 where magnetization is aligned in the direction... Protective film 9... Transparent substrate 10...
High magnetic permeability thin film 11...Magnetic transfer film 12...Movement direction of light beam, 13...Conventional reproduction output 14...Reproduction output in the embodiment of the present invention Patent attorney Junnosuke Nakamura 1st Figure 2 Figure 3 (C) Figure 4 Figure 5

Claims (1)

[Claims] 1. A magnetic thin film serving as an information recording medium, a light beam that heats a local portion of the magnetic thin film, and a modulated magnetic field applied to the local portion of the magnetic thin film heated by the light beam. In a method of performing magneto-optical recording using a magneto-optical recording device having at least a magnetic head, the magnitude of the modulated magnetic field applied by the magnetic head changes in a local portion of the magnetic thin film heated by the light beam, and the magnetic field strength increases. A magneto-optical recording method using a magnetic field modulation method characterized by non-uniformity. 2. Magneto-optical recording comprising at least a magnetic thin film serving as an information recording medium, a light beam that heats a local portion on the magnetic thin film, and a magnetic head that applies a modulated magnetic field to the local portion heated by the light beam. In a method of performing magneto-optical recording using a device, the magnitude of the modulated magnetic field applied over a sufficiently wider area than the local area of the heated magnetic thin film is uniform in the direction perpendicular to the information writing direction. and is characterized in that the modulated magnetic field applied in the information writing direction is large in a high temperature region immediately after heating in a local portion of the heated magnetic thin film, and is small in a subsequent low temperature region. A magneto-optical recording method using magnetic field modulation. 3. In the magneto-optical recording method according to claim 1 or 2, the modulating magnetic field applied to the heated local portion of the magnetic thin film is located at the end of the modulating magnetic field and in the information writing direction. The change in magnetic field has a steep slope with respect to
A magneto-optical recording method using a magnetic field modulation method, characterized in that the recording area of information recorded on a magnetic thin film has a nearly rectangular shape. 4. At least comprising a magnetic thin film serving as an information recording medium, a light beam that heats a local portion on the magnetic thin film, and a magnetic head that applies a modulated magnetic field to the local portion of the magnetic thin film heated by the light beam, and information writing in which the intensity of the modulated magnetic field applied by the magnetic head changes in a local portion of the magnetic thin film heated by the light beam, giving a non-uniform magnetic field intensity, so that the information recording area has a nearly rectangular shape. What is claimed is: 1. A magneto-optical recording device using a magnetic field modulation method, comprising at least a means for reading out information recorded by the information writing means using a transfer type magneto-optical head.