JPH07192333A - Magneto-optical recording medium and its reproduction method - Google Patents

Abstract

PURPOSE:To obtain a high-resolution magneto-optical recording medium without need for a transferred magnetic film and an initializing magnetic field. CONSTITUTION:This recording medium has a reproducing magnetic film 13 and a recording magnetic film 14 on a substrate 11, and the reproducing magnetic film 13 is formed from material forming an intrasurface magnetized film in a first temp. range including room temp., forming a perpendicularly magnetized film in a second temp. range higher than the first temp. range and forming an intrasurface magnetized film in a third temp. range higher than the second temp. range. A magnetic coupling is caused between the reproducing magnetic film 13 and the recording magnetic film 14, and the recording magnetic domain is deformed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording and erasing by utilizing temperature rise by laser light and reading a recording signal by magneto-optical effect, and a reproducing method thereof.

[0002]

2. Description of the Related Art Magneto-optical recording is a thermomagnetic method in which a magnetic film is locally heated to a Curie point or a compensation temperature or higher by laser light to magnetize an irradiated portion of the magnetic film in the direction of an external magnetic field to form a recording magnetic domain. Recorded. The recording method for the magneto-optical recording medium includes a magnetic field modulation recording method in which the temperature of the recording magnetic film is raised by irradiating a laser beam of a constant intensity, and thermomagnetic recording is performed by an external magnetic field whose direction is modulated according to a recording signal. There is an optical modulation recording method in which an external magnetic field having a constant intensity is applied and a laser beam modulated according to a recording signal is irradiated to raise the temperature of a recording magnetic film to perform thermomagnetic recording.

In the conventional magneto-optical recording medium, when the recording magnetic domain becomes smaller than the reproducing light spot diameter, the magnetic domain before and after the recording magnetic domain to be reproduced is included in the detection range, and the reproduced signal becomes small due to the interference between them. There was a problem that the / N ratio was lowered.

In order to solve the problem, a magneto-optical recording medium as shown in FIG. 4 (Nikkei Electronics 1991.10.2)
8 no.539) has been proposed, which will be briefly described below. In FIG. 4, 40 is the disc moving direction, 41 is a recording and reproducing magnetic field, 42 is an initializing magnetic field, 43 is a reproducing magnetic film, 44 is a transfer magnetic film, 45 is an intermediate film, 46 is a recording magnetic film, and 47 is reproducing light. A spot, 48 is a recording magnetic domain, 49 is a region above the Curie temperature TC of the transfer magnetic film, 50 is an intermediate temperature region, and 51 is a low temperature portion in the reproducing light spot.

A recording signal is recorded on the recording magnetic film 46 by the recording magnetic domain 48.
Is thermomagnetically recorded, and the transfer magnetic film 44 is strongly exchange-coupled with the reproducing magnetic film 43. The intermediate film 45 is a film provided so that the domain wall becomes stable when the magnetization directions of the reproducing magnetic film 43 and the recording magnetic film 46 are aligned.

The reproducing operation of these film structures will be described below. Initially, the reproducing magnetic film 43 is aligned in the direction of the initializing magnetic field 42. At the time of reproduction, the temperature rises due to the irradiation of reproduction light, but a temperature distribution occurs on the recording medium. Here, since the coercive force of the reproducing magnetic film 43 decreases as the temperature rises, the recording magnetic film 4 in the temperature region 50.
The exchange coupling with 6 becomes dominant, and the magnetization direction is aligned with the magnetization direction of the recording magnetic film 46. Further, in the region 49 above the temperature Tc, the magnetization of the transfer magnetic film 44 disappears, so that the exchange coupling between the reproducing magnetic film 43 and the recording magnetic film 46 at that portion is interrupted, and the magnetization of the reproducing magnetic film 43 is reproduced. The direction of the magnetic field 41 is aligned. Therefore, both the low temperature region 51 and the high temperature region 49 in the reproduction light spot are masked, and the recording information is read out as the reproduction signal only from the temperature region 50, so that the recording magnetic domain is smaller than the size of the reproduction light spot. However, it can be reproduced without causing interference from the recording magnetic domains before and after.

However, in the above magneto-optical recording medium,
The recording layer must have at least a three-layer structure of a reproducing magnetic film, a transfer magnetic film, and a recording magnetic film, which poses many manufacturing problems in terms of mass productivity and reliability, and also requires an initializing magnetic field. Had.

As a means for solving this, a magneto-optical recording medium using an in-plane magnetized film as a reproducing magnetic film as shown in FIG. 5 has been proposed (JP-A-5-81717). In FIG. 5, reference numeral 52 is a reproducing magnetic film, 53 is a recording magnetic film, 54 is a disc moving direction, 55 is reproducing light, 56 is a reproducing light spot, 57 is a high temperature portion in the reproducing light spot, and 58 is a reproducing light spot. A low temperature portion, 59 is a recording magnetic domain.

The reproducing operation of these film structures will be described below. The recording signal is recorded in the recording magnetic film 53 as recording magnetic domains 59 by thermomagnetic recording.
The reproducing magnetic film 52 is an in-plane magnetized film at room temperature, and becomes a perpendicular magnetized film at the high temperature portion 57 in the reproducing light spot. During reproduction, the temperature of the portion irradiated with the reproduction light rises, and a high temperature portion 57 and a low temperature portion 58 are formed due to the temperature distribution. Here, in the high temperature portion 57, the reproducing magnetic film 52 changes to a perpendicular magnetic film, and the magnetization direction of the recording magnetic film 53 is aligned by exchange coupling. Also, when the disk moves and the temperature drops, the reproducing magnetic film 52 changes to the in-plane magnetized film again, so that it is possible to reproduce a recording magnetic domain smaller than the reproducing light spot without an initializing magnetic field.

[0010]

In the magneto-optical recording medium in which an in-plane magnetized film is used as the reproducing magnetic film and the change thereof is used, there is an effect that the initialization magnetic field can be eliminated, but in the reproducing light spot. Since the signal is taken out only in the high temperature portion of, there is the following drawback.

1. Insufficient resolution 2. In order to solve the above problems, the present invention eliminates the need for a transfer magnetic film and an initializing magnetic field, and provides a high-performance magneto-optical recording medium with high resolution. The purpose is to obtain a reproducing method suitable for density recording.

[0012]

In order to achieve the above-mentioned object, a magneto-optical recording medium of the present invention has at least a reproducing magnetic film and a recording magnetic film on a substrate, and the reproducing magnetic film includes room temperature. An in-plane magnetization film in the first temperature region, a perpendicular magnetization film in the second region having a temperature higher than the first temperature region, and a second
It is characterized in that it becomes an in-plane magnetized film in a third region having a temperature higher than the temperature region of. In addition, the recording magnetic film records a signal as a magnetic domain, the reproducing magnetic film becomes a perpendicular magnetization film in the second temperature region by laser light irradiation, and the recording magnetic domain transferred by magnetic coupling with the recording magnetic film has a magneto-optical effect. The reproduction magnetic film is converted into an optical signal by an optical signal, and the reproduction magnetic film changes from the perpendicular magnetization film to the in-plane magnetization film in the third temperature region again due to the temperature distribution of the laser light. It is a characteristic magneto-optical recording medium.

Further, in the reproducing method for the magneto-optical recording medium of the present invention, the in-plane magnetized film is used as the reproducing magnetic film, and the third magnetic layer is used for reproducing.
Is a reproducing method for narrowing the region where the signal of the recording magnetic film is transferred to the reproducing magnetic film by heating to the temperature region of (1) and applying a reproducing magnetic field.

[0014]

The magneto-optical recording medium of the present invention having the above-described structure has the following effects. Recording magnetic domains are formed on the recording magnetic film by thermomagnetic recording.

On the other hand, at the time of reproducing, by irradiating the reproducing magnetic film with laser light, the reproducing magnetic film changes from the in-plane magnetized film to the perpendicular magnetized film due to the temperature rise, and the recording magnetic domain is magnetically coupled with the recording magnetic film. Is transferred, and the recording signal is read out as an optical signal by the magneto-optical effect in which the polarization plane of the reflected light or the transmitted light rotates depending on the magnetization direction of the recording magnetic domain. At this time, a temperature distribution is generated in the reproducing spot, and the reproducing magnetic film becomes a perpendicularly magnetized film only in the second temperature region. Therefore, in the reproducing light spot, the first and third temperature regions are formed. A magnetic domain is masked.

By applying a reproducing magnetic field Hr during reproduction, the exchange coupling force Hc between the reproducing magnetic film and the recording magnetic film is H.
In the region where r> Hc, even if the reproducing magnetic film is a perpendicularly magnetized film, it is directed in the direction of the reproducing magnetic field, so that the range of the recording magnetic domain transferred is smaller than the second temperature region. Therefore, the reproduction area can be further narrowed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical recording medium according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a magneto-optical recording medium according to an embodiment of the present invention. In FIG. 1, 11 is a substrate made of glass, plastic or the like, 12 and 15 are protective films made of a ZnS film, 13 is a reproducing magnetic film made of a GdFeCo film, 14 is a recording magnetic film made of a TbFeCo film, 16
Is a protective layer made of an epoxy acrylate resin.
Here, each film on the substrate 11 is formed by a sputtering method or a vacuum evaporation method, and the protective layer 16 is formed by a spin coating method after the film formation is completed. The respective film thicknesses of the protective films 12 and 15 are 60 to 120 nm, the reproducing magnetic film 13 is 10 to 80 nm,
The recording magnetic film 14 has a thickness of 30 to 100 nm.

FIG. 2 shows the operation of the magneto-optical recording medium of one embodiment of the present invention. In FIG. 2, (a) shows the coercive force of the reproducing magnetic film with respect to temperature, and (b) shows the upper diagram near the reproducing light spot on the disk. 21 is a region of the in-plane magnetized film, 22 is a region of the perpendicular magnetized film, 23 is a reproducing light spot, 24 is a third temperature region in the reproducing light spot, 25 is a second temperature region in the reproducing light spot, 26 Is the first temperature region in the reproducing light spot, 27 is the disc moving direction, and 28 is the recording magnetic domain.

As shown in FIG. 2, the coercive force of the reproducing magnetic film increases with temperature, and decreases when it exceeds the compensation temperature Tcomp.
As the temperature of the reproducing magnetic film increases, the first temperature region 26
In the in-plane magnetized film in, the perpendicular magnetic film in the second temperature region 25 is formed, and in the third temperature region 24, the in-plane magnetized film is formed again. During reproduction, a temperature distribution is formed in the area irradiated with the reproduction light, so that the third temperature area 24, the first temperature area 26, and the second temperature area 2 in between are located in the reproduction light spot.
There are five. At this time, since the reproducing magnetic film is an in-plane magnetized film in the third temperature region 24 and the first temperature region 26, exchange coupling with the recording magnetic film does not occur and only in the second temperature region 25. It acts as a perpendicular magnetization film, and exchange coupling works strongly with the recording magnetic film. Therefore, the recording signal can be reproduced from a part of the reproduction light spot.

FIG. 3 is a simplified diagram showing the operation when reproducing is performed using a magneto-optical recording medium of one embodiment of the present invention while applying a reproducing magnetic field during reproduction. (A) shows the change in coercive force with respect to the temperature of the reproducing magnetic film, where the horizontal axis represents temperature and the vertical axis represents the strength of coercive force. (B) shows the state of magnetization of the recording layer at that time. Here, 31 is a reproducing magnetic film, 32 is a recording magnetic film, 33 is a reproducing magnetic field, and 34 is a region where the exchange coupling force Hc between the reproducing magnetic film and the recording magnetic film is smaller than the reproducing magnetic field Hr (Hr> Hc).

Next, the operation will be described with reference to FIG. When the temperature of the reproducing magnetic film 31 rises due to the irradiation of reproducing light, it changes from the in-plane magnetized film to the perpendicular magnetized film and is aligned with the recording magnetic film 32 by exchange coupling. Then, as the temperature further rises, it changes to the in-plane magnetized film again, and the exchange coupling between the reproducing magnetic film and the recording magnetic film is interrupted. At this time,
By applying the reproducing magnetic field 33 as shown in FIG. 5, the magnetization direction of the reproducing magnetic film 31 changed to the perpendicular magnetization film in the region of Hr> Hc of the reproducing magnetic film in the second temperature region is forced to the direction of the reproducing magnetic field. Hr <Hc in a narrower range, that is, in the second temperature range.
It is possible to read the recorded information in the area.

In the magneto-optical recording medium of this embodiment, ZnS films were used as the protective films 12 and 15. However, instead of the ZnS film, other chalcogenide film, oxide film such as TaO ₂ film, SiN, etc. A nitride film such as a film or a film of a compound thereof may be used. In this embodiment, the reproducing magnetic film 13 is a GdFeCo film, and the recording magnetic film 14 is T.
Although an epoxy acrylate resin is used as the bFeCo film and the protective layer 16, both surfaces may be bonded with a urethane resin or a hot melt adhesive, and each magnetic film may be a rare earth-transition metal ferrimagnetic film or MnB.
A Mn-based magnetic film such as iAl or another magnetic material may be used.

[0024]

As is clear from the above description of the embodiments, the magneto-optical recording medium of the present invention reads while masking the recording magnetic domain during reproduction, so that not only the linear recording density is improved but also the reproduction magnetic film is formed. Since the property of changing from the in-plane magnetized film to the perpendicular magnetized film is utilized, not only does the initialization magnetic field become unnecessary, but the recording layer may have a two-layer structure of a reproducing magnetic film and a recording magnetic film, and the number of laminated layers is reduced. be able to.

By applying a reproducing magnetic field during reproduction, the area where the recording signal is transferred can be further narrowed down, and higher density can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of a magneto-optical recording medium according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the magneto-optical recording medium of one embodiment of the present invention.

FIG. 3 is an operation diagram of a magneto-optical recording medium according to an embodiment of the present invention.

FIG. 4 is a configuration diagram illustrating the operation of a conventional magneto-optical recording medium.

FIG. 5 is a configuration diagram illustrating the operation of a conventional magneto-optical recording medium.

[Explanation of symbols]

 11 substrate 12 protective film 13 reproducing magnetic film (GdFeCo-based magnetic film) 14 recording magnetic film (TbFeCo-based magnetic film) 15 protective film 16 protective layer 21 in-plane magnetized film region 22 perpendicularly magnetized film region 23 reproducing light spot 24 reproduction Third temperature region in light spot 25 Second temperature region in reproduction light spot 26 First temperature region in reproduction light spot 27 Disk moving direction 28 Recording magnetic domain 31 Reproducing magnetic film 32 Recording magnetic film 33 Reproducing magnetic field 34 Area of Hr> Hc

Claims (3)

[Claims] 1. A substrate having at least a reproducing magnetic film and a recording magnetic film, wherein the reproducing magnetic film is an in-plane magnetized film in a first temperature region including room temperature, and a second magnetic film having a temperature higher than the first temperature region. Between the reproducing magnetic film and the recording magnetic film only in the second temperature region, the material being the perpendicular magnetization film in the region 2 and the in-plane magnetization film in the third region having a temperature higher than the second temperature region. A magneto-optical recording medium characterized in that the magnetic domain is magnetically coupled to deform the recording magnetic domain. 2. When reproducing the information recorded on the magneto-optical recording medium according to claim 1, a reproducing portion of the reproducing magnetic film is in the second temperature region, and a portion other than the reproducing portion is the first or first portion. A reproducing method of a magneto-optical recording medium, which comprises heating to a temperature range of 3 and reproducing. 3. A reproducing method of a magneto-optical recording medium according to claim 2, wherein a reproducing magnetic film is reproduced by applying a magnetic field having a predetermined intensity.