JPH0330137A - magneto-optical disk device - Google Patents

Abstract

PURPOSE:To quicken the transfer rate at information recording by controlling recording and erasure of the information only in the magnetization direction of a region (inverted magnetization region) in which the magnetization direction of the data region is not fixed. CONSTITUTION:A perpendicular magnetization film 2 is used for a recording medium, a data region recording the information and a guide region controlling the magnetization direction of the data region are arranged alternately. In the recording and erasure of the information, it is implemented by controlling the magnetization direction of the region where the magnetization direction of a data region is not fixed, that is, only the inverted magnetization region. Moreover, in order to ensure the magnetization inversion of the inverted magnetization region, the intensity of anti-magnetic field around the magnetization inversion region is controlled with the shape and irradiation energy by approaching at least two optical spots 3,4. Thus, overwrite is attained by having only to change the light intensity of the two light spots without applying the external magnetic field, then the transfer rate is quickened when the information is written.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an apparatus for recording, reproducing, and erasing information by irradiating a recording medium with a laser beam.

[Conventional technology]

Regarding overwriting by conventional optical modulation, Applied Physics Letters, 49 (8) (App
i. Phys, lett. 49 (8), 25
August 1986). According to this paper, the magnetization direction of the perpendicularly magnetized film is controlled by the intensity and irradiation time of the light spot. In principle, using a compensation point recording medium with a compensation point temperature higher than the surrounding temperature (or room temperature), the area to be recorded or erased is made to have a temperature higher than the compensation point by the irradiation energy of the light spot, and the irradiation area is The magnetization direction of the irradiated area is reversed by the demagnetizing field. However, although the irradiation energy values for recording and erasing are almost the same, the irradiation time slightly changes (
Since the erase pulse width must be approximately 172 to 1/3 of the recording pulse width to reverse the magnetization direction of the irradiated area, the size of the magnetization reversal area due to the demagnetizing field in the irradiated area of the light spot in the case of recording is The above paper shows that the size of the magnetization reversal region in the case of magnetization and erasure is different.

[Problem to be solved by the invention]

The above conventional technology does not take into account the control of the size of the magnetization switching region for recording and erasing, nor the stability of that region (reliable magnetization switching of the light spot irradiation region), and does not allow for high-density recording of data or transfer rate. Problems remained in terms of speed and reliability. An object of the present invention is to eliminate the above-mentioned drawbacks associated with erasing (or overwriting) in a magneto-optical disk device, and to reduce the strength of the demagnetizing field around the recording area or erasing area (reversed magnetization area) by optically The object of the present invention is to provide a recording/erasing method controlled by spot irradiation energy. At the same time, the objective is to increase the transfer rate when recording information.

[Means to solve the problem]

In order to achieve the above object, a perpendicular magnetization film is used in the recording medium, and data areas for recording information and guide areas for controlling the magnetization direction of the data areas are arranged alternately. Furthermore, in the data area, areas with fixed magnetization directions and areas with unfixed magnetization directions are arranged alternately, and initialization is performed so that the magnetization directions of the fixed magnetization areas and the guide areas of the data area are reversed. Recording and erasing information is
The magnetization direction of the area where the magnetization direction of the data area is not fixed (
This is done by controlling only the recording area or erasing area (reversed magnetization area). In addition, in order to ensure magnetization reversal in the recording area or erase area (reversed magnetization area), the strength of the demagnetizing field around the magnetization reversal area (the demagnetizing field from the fixed magnetization direction of the data area and the demagnetizing field from the guide area) must be adjusted. There is a method in which at least two light spots are placed close to each other and the magnetic field is controlled by the shape and irradiation energy.

[Effect 1] In a recording medium using a perpendicular magnetization film, a data area in which information is recorded is sandwiched between guide areas that control the magnetization direction of the data area, and the data area is fixed with a reverse magnetization area of approximately the same degree. The magnetized regions are arranged alternately, and the magnetization direction of the fixed magnetization regions of the data region and the magnetization direction of the guide region are initialized to be opposite to each other. Furthermore, the magnetization directions of the reversed magnetization region and the fixed magnetization region of the data area and the magnetization direction of the guide region match when no data is recorded. Thereby, the densest pattern recorded in the data area is uniquely determined. This is because the information recording and reproducing method is bit edge, and the fixed magnetization area recorded in advance is the minimum edge. Furthermore, even when the magnetization direction of the inverted magnetization region is set to be the same as the fixed magnetization direction, a highly reliable reproduction signal can be obtained because the length between the fixed magnetization regions recorded in advance corresponds to the information. I can do it. Furthermore, by utilizing the fact that the densest pattern recorded in the data area is uniquely determined, it is possible to use the densest pattern as a self-clock. This makes it possible to accurately irradiate a light spot onto the reversed magnetization region of the data region. Furthermore, by controlling the inverted magnetization region, even if the size of the fixed magnetization region changes slightly, the reproduced signal can be easily corrected by using the close-packed pattern as a self-clock. ．． [Embodiment] An embodiment of the present invention will be described below with reference to FIG. The recording medium is formed of a substrate 1 and a perpendicular magnetization film 2, and the perpendicular magnetization film 2 is attached to the surface of the substrate 1 by a method such as sputtering. First, the magnetization direction of the perpendicular magnetization 12 is initialized to one direction. The initialization method is to generate a large magnetic field in a certain direction using an electromagnet, place the recording medium in that magnetic field, and then
The magnetization direction of the perpendicular magnetization film 2 is changed from the perpendicular magnetization PIA 2 to the substrate l.
This is done by pointing in the direction of (downward). The data area in which information is recorded is sandwiched between guide areas that control the magnetization direction of the data area. The magnetization direction of the region and the magnetization direction of the guide region are opposite to each other. Further, in the non-recording state, the magnetization directions of the reversed magnetization region and the fixed magnetization region of the data area are reversed to each other, and the magnetization direction of the reversed magnetization region and the magnetization direction of the guide region are the same. The magnetization direction of the perpendicular magnetization film 2 during the initialization is perpendicular magnetization II! ! Since the magnetization direction is downward in all 12 regions, this magnetization direction is taken as the magnetization direction of the reverse magnetization region of the guide region and the data region. In order to form a fixed magnetization region in the data region, a light spot is formed in the direction of the data region of the perpendicular magnetization film 2, and the light spot is irradiated on the region to be made into a fixed magnetization region, and the temperature is raised to above the Curie point. An upward fixed magnetization region is formed using the demagnetizing field caused by the downward magnetization of the perpendicularly magnetized film 2 during the initialization. Alternatively, it may be formed by applying a constant upward magnetic field. Furthermore, it is also possible to form by a magnetic transfer method. Control of the magnetization direction of the reverse magnetization region of the data area will be explained using FIG. Figure 2 shows the reversed magnetization region (
/l! of the reverse magnetization region (non-magnetized region) when a light spot is irradiated on the region (a region sandwiched between fixed magnetization regions) to raise the temperature to the Curie point or higher. ! ! The opposite of the encirclement? This shows the influence of the world. Strictly speaking, it is necessary to consider the influence of all demagnetizing fields around the reversed magnetization region. however,
By considering the influence of the demagnetizing fields from the two fixed magnetization regions and the two guide regions adjacent to the reversed magnetization region, it is possible to conduct an almost exact examination. Thereby, the influence of the demagnetizing field from the surroundings on the non-magnetized region is reduced by the downward demagnetizing field H from the two fixed magnetized regions adjacent to the non-magnetized region.
It is determined by d■, Hd, and the upward demagnetizing field Hg, yHgz from the two guide regions. The overall effective demagnetizing field He that affects the non-magnetized region is: Hc=Hd1+Hd2+Hg,+Hg2 (1)
becomes. Therefore, by changing the magnitude of the overall effective demagnetizing field that affects the non-magnetized region, the temperature of the non-magnetized region is lowered, and the direction of magnetization when magnetization occurs can be arbitrarily controlled. be able to. An embodiment in which the magnetization direction of the reversed magnetization region of the data area is set to be the same as the fixed magnetization direction will be described with reference to FIG. In FIG. 3(a), adjacent first light spot 3 and second light spot 4 are scanned in the direction of the data area. The first light spot 3 is a substantially elliptical light spot with its long axis on the guide region side, and the second light spot 4 is
It is a nearly circular light spot. When the second light spot 4 is scanned in an area where the magnetization direction of the reversed magnetization region in the data area is set to be the same as the fixed magnetization direction, the light intensity of the second light spot 4 is increased to set the reverse magnetization region in the same direction as the fixed magnetization direction. The temperature should be higher than the Curie point temperature (Tc). Almost simultaneously, the light intensity of the first light spot 3 is made smaller than the light intensity of the second light spot 4,
To reduce the influence of the demagnetizing field Hd in the fixed magnetization region. The magnitude of the demagnetizing field Hd1 in the fixed magnetization region depends on the temperature (T) and decreases as the light intensity of the second optical spot 4 increases, so the demagnetizing field Hd in this case is expressed as a function of temperature. Let it be Hd(T). ) To make the effective demagnetizing field Hc in equation (1) an upward magnetic field, the light intensity of the second light spot 4 is set so as to satisfy the following conditions. Hd(T) + Hd. <Hg+Hg2(2)
FIG. 3(b) shows a state in which the magnetization direction of the reversed magnetization region of the data area is set to be the same as the fixed magnetization direction through the above process. The black part in the figure is the recorded area, and the magnetization direction of this area is upward. Next, a case will be described in which the magnetization direction of the reverse magnetization region of the data area is set to be opposite to the fixed magnetization direction using FIG. In FIG. 4(a), as explained in FIG. 3, the magnetization direction of the reversed magnetization region of the pre-recorded data area is set to the direction opposite to the fixed magnetization direction (the magnetization direction when not recorded). A state in which the first light spot 3 is scanned over the area is shown. The light intensity of the first light spot 3 is increased to make the reversed magnetization region equal to or higher than the Curie point temperature (Tc). Let these magnetic fields be Hg(T) and Hga(T). Almost simultaneously, the light intensity of the second light spot 4 is made smaller than the light intensity of the first light spot 3, or almost no light is irradiated. The demagnetizing field Hd2 in this case is assumed to be Hd2 (di). Here, in order to make the effective demagnetizing field Hc in equation (1) a downward magnetic field, the light intensities of the first optical spot 3 and the second optical spot 4 are set as described above so as to satisfy the following conditions. Hg(T) + Hlh(T) < Hd+
Hdz(T) (3) FIG. 4(b) shows a state in which the magnetization direction of the reverse magnetization region of the data area is set to be opposite to the fixed magnetization direction through the above process. The broken line area in the figure is the erased area, and the magnetization direction is downward. This is the same direction as the magnetization direction when recording is not performed. As mentioned above, recording and erasing are performed using the first light spot 3.
By changing the light intensity of the second light spot 4,
, (3), overwriting becomes possible because it does not depend on the magnetization direction of the area to be recorded or erased. As a means for forming two light spots on a recording medium, as described in Japanese Patent Application Laid-Open No. 60-246033,
It is easily achievable. When applied to this embodiment, a circular light spot is formed with a short wavelength, and an elliptical light spot is formed with a long wavelength. This is because a shorter wavelength can form a smaller light spot and is very effective in increasing the density of information. In addition, by aligning the bonding direction of the semiconductor laser in the direction perpendicular to the data area, the elliptical light spot can be created using the far field pattern (ellipse) of the semiconductor laser.
is reflected and formed on the recording medium. This has the effect of simplifying the optical system. Furthermore, light spots may be formed with the same wavelength. Information is reproduced by using the second light spot 4, which is approximately circular, to detect the intensity of reflected light from the recording medium in accordance with the Kerr rotation angle due to the magnetization direction of the data area. Furthermore, since the distance over which the magnetization direction of the data area changes can be made to correspond to information, it is possible to increase the density of data. Furthermore, even if the size of the fixed magnetized regions changes somewhat due to overwriting, the reproduced signal can be easily corrected by utilizing the fact that the minimum interval of the fixed magnetized regions is a close-packed pattern.

【Effect of the invention】

According to the present invention, two
This has the effect of allowing overwriting by simply changing the light intensity of one light spot. Furthermore, overwriting is possible even when a certain weak magnetic field is applied from the outside. Furthermore, since overwriting is possible, the transfer rate when writing information is increased. Also. Even if the size of the fixed magnetized region changes slightly due to overwriting, the reproduced signal can be easily corrected by taking advantage of the fact that the minimum interval of the fixed magnetized region is a close-packed pattern. It is suitable for high-density storage, enables highly sensitive signal detection, and has the effect of improving data reliability.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the magnetization direction of a recording medium and its arrangement in an embodiment of the present invention, and FIG. 2 is a perspective view of a recording medium for explaining the principle of an overwrite method in an embodiment of the present invention. FIG. 3 is a perspective view showing the magnetization direction and its arrangement, FIG. 3 is a perspective view showing the magnetization direction and arrangement of a recording medium showing a recording method in an embodiment of the invention, and FIG. 4 is an embodiment of the invention. FIG. 2 is a perspective view showing the magnetization direction of a recording medium and its arrangement, showing an erasing method in FIG. Explanation of symbols 1... Substrate, 2... Perpendicular magnetization film, 3... ↓ light spot 1-, 3... 2nd light spot Fig. 3 conduit 2.

Claims (1)

[Claims] 1. A recording medium having at least two laser light sources and a magneto-optical effect, and at least two laser light sources in a predetermined area of the recording medium.
In a magneto-optical disk device comprising an optical system that irradiates two light spots, the recording medium is a perpendicularly magnetized film,
A data area for recording information and a guide area for controlling the magnetization direction of the data area are arranged alternately, and fixed areas and unfixed areas are arranged alternately in the magnetization direction in the data area. The magnetization direction of the data region and the guide region are initialized so that they are reversed, and information is recorded and erased by controlling only the magnetization direction of the region where the magnetization direction of the data region is not fixed (inverted magnetization region). A magneto-optical disk device characterized by: 2. The magneto-optical disk according to claim 1, wherein one of the two light spots has a substantially circular shape, and the other has an elliptical shape with a long axis in a direction perpendicular to the data area. Device. 3. The magneto-optical disk according to claim 1, wherein the means for forming the elliptical light spot according to claim 2 is made so that the bonding direction of the semiconductor laser coincides with the direction perpendicular to the data area. Device. 4. The magneto-optical disk device according to claim 1, wherein the two optical spots as described in claim 2 are arranged in the data area direction. 5. The magnitude of magnetization of the recording and erasing area according to claim 1, the demagnetizing field of the data area surrounding the recording and erasing area, and the demagnetizing field of the guide area are determined by the two lights according to claim 2. 2. The magneto-optical disk device according to claim 1, wherein the magnetization direction of the recording and erasing areas is controlled by controlling the intensity of the light of the spot. 6. The magneto-optical disk device according to claim 1, wherein in the data area, the fixed magnetization area is larger than the reversed magnetization area. 7. The magneto-optical disk device according to claim 1, wherein the size of the circular light spot as described in claim 2 is smaller than the fixed magnetization area of the data area. 8. The elliptical light spot according to claim 1, wherein the size of the elliptical light spot in the long axis direction is approximately the same as or smaller than the interval between adjacent data areas. Magneto-optical disk device.