JP2001266426A - Magneto-optical recording medium and reproducing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium having a simple film structure and capable of transferring a magnetic domain from a recording layer to a reproducing layer with high resolution and to provide a reproducing unit for enlarging/reproducing the magnetic domain from the magneto-optical recording medium without using an alternating magnetic field. SOLUTION: This magneto-optical recording medium 10 is provided with a translucent substrate 1, an underlaid layer 2, a reproducing layer 3, a mask layer 4, a recording layer 5 and a protection layer 6. In the layer 4 an intra- surface magnetization film is transformed into a perpendicularly magnetized film at the first temperature T1 and the magnetization is deleted at the second temperature T2 higher than the first temperature T1. In the layer 3 an intra- surface magnetization film is transformed into a perpendicularly magnetized film at the third temperature T3 lower than the first temperature T1. The magnetic domain in the layer 5 in enlarged and transferred to the layer 3 by applying a DC magnetic field to the medium 10 to reproduced the signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magneto-optical recording medium for recording a signal, and a reproducing apparatus for reproducing a signal from the magneto-optical recording medium by a magnetic domain enlarging method.

[0002]

2. Description of the Related Art Magneto-optical recording media have attracted attention as rewritable, large-capacity, and highly reliable recording media, and have begun to be put to practical use as computer memories and the like. Recently, the recording capacity is 6.0 Gby.
tes's magneto-optical recording medium is AS-MO (Advanced)
d Storage Magneto Optica
l disk) standard and is about to be put to practical use.

[0003] Further, a 14 Gbyte by magnetic domain expansion reproduction method for reproducing signals by enlarging and transferring magnetic domains of a recording layer to a reproduction layer.
A magneto-optical recording medium having a recording capacity of es has also been proposed. In the signal reproduction from the magneto-optical recording medium by the magnetic domain expansion reproduction method, a magnetic domain of the recording layer is transferred and expanded to the reproduction layer by applying an alternating magnetic field having a constant period from a direction perpendicular to the magneto-optical recording medium, and the transfer is performed. -The detection was performed by detecting the expanded magnetic domain with a laser beam.

When a magnetic domain of a recording layer is transferred to a reproducing layer, a magnetic domain present on a higher temperature side than a magnetic domain to be transferred to the reproducing layer is prevented from being transferred to the reproducing layer by a low Curie temperature magnetic layer. However, the magnetic domains existing on the lower temperature side than the magnetic domains to be transferred to the reproducing layer are prevented from being transferred to the reproducing layer by the in-plane magnetic film.

[0005]

However, in the structure of the conventional magneto-optical recording medium, the magnetic domain existing on the higher temperature side than the magnetic domain to be transferred to the reproducing layer and the magnetic domain existing on the lower temperature side from the magnetic domain to be transferred to the reproducing layer. Since the magnetic layers for preventing transfer to the reproducing layer with existing magnetic domains are separate magnetic layers, the film structure is complicated, and there is a problem that it is difficult to control the temperature distribution of each magnetic layer.

Accordingly, the present invention solves such a problem, and a magneto-optical recording medium having a simple film structure and capable of transferring magnetic domains from a recording layer to a reproducing layer with high resolution, and using an alternating magnetic field from the magneto-optical recording medium. It is an object of the present invention to provide a reproducing apparatus that performs magnetic domain expansion reproduction without using the magnetic disk.

[0007]

The invention according to claim 1 includes a recording layer, a mask layer formed in contact with the recording layer, and a reproduction layer formed in contact with the mask layer. The mask layer is an in-plane magnetic film at room temperature, changes into a perpendicular magnetic film at a first temperature higher than room temperature, and is a magnetic layer whose magnetization disappears at a second temperature higher than the first temperature. It is a recording medium.

In the magneto-optical recording medium according to the first aspect, when the temperature of the magneto-optical recording medium is increased by irradiating a laser beam, a region of the mask layer having a temperature lower than the first temperature has in-plane magnetization. Holding, the region from the first temperature to the second temperature changes to a perpendicular magnetization film, and the magnetization disappears in the region above the second temperature. Then, the magnetic domains existing in the region of the recording layer at the first temperature or lower are prevented from being transferred to the reproducing layer by the in-plane magnetic film of the mask layer, and are transferred to the region of the recording layer at the second temperature or higher. In the existing magnetic domain, transfer by exchange coupling to the reproducing layer is prevented by the region where the magnetization of the mask layer has disappeared. Then, in the recording layer, only magnetic domains existing in a region from the first temperature to the second temperature can be transferred to the mask layer and the reproducing layer by exchange coupling.

Therefore, according to the first aspect of the present invention, by applying a DC magnetic field to the magneto-optical recording medium at the time of reproducing a signal, the magnetic domain of the recording layer existing in the region of the second temperature or higher is changed to the mask layer. Is not transferred to the reproducing layer by magnetostatic coupling via the region where the magnetization has disappeared, and only the magnetic domains existing in the region from the first temperature to the second temperature can be clearly transferred to the reproducing layer.

[0010] The invention according to claim 2 provides a recording layer,
A mask layer formed in contact with the recording layer; and a reproducing layer formed in contact with the mask layer, wherein the mask layer is an in-plane magnetic film at room temperature, and is a perpendicular magnetic film at a first temperature higher than room temperature. And the reproducing layer is an in-plane magnetized film at room temperature, the magnetization of which disappears at a second temperature higher than the first temperature.
The magneto-optical recording medium is a magnetic layer that changes into a perpendicular magnetization film at a third temperature lower than the first temperature.

In the magneto-optical recording medium according to the second aspect, when the temperature of the magneto-optical recording medium is increased by irradiating a laser beam, a region of the mask layer having a temperature lower than the first temperature has in-plane magnetization. Holding, the region from the first temperature to the second temperature changes to a perpendicular magnetization film, and the magnetization disappears in the region above the second temperature. Further, a region of the reproducing layer having a temperature equal to or higher than the third temperature changes from an in-plane magnetic film to a perpendicular magnetic film. Then, the magnetic domains existing in the region of the recording layer at the first temperature or lower are prevented from being transferred to the reproducing layer by the in-plane magnetic film of the mask layer, and are transferred to the region of the recording layer at the second temperature or higher. In the existing magnetic domain, transfer by exchange coupling to the reproducing layer is prevented by the region where the magnetization of the mask layer has disappeared. Then, of the recording layer, only the magnetic domains existing in the region from the first temperature to the second temperature are transferred to the mask layer by exchange coupling, and the magnetic domains transferred to the mask layer are reproduced by enlarging the magnetic domains. Transferred to the layer.

Therefore, according to the second aspect of the present invention, by applying a DC magnetic field to the magneto-optical recording medium at the time of reproducing a signal, the magnetic domain of the recording layer existing in the region of the second temperature or higher is changed to the mask layer. Is not transferred to the reproducing layer by magnetostatic coupling via the region where the magnetization has disappeared, and only the magnetic domains existing in the region from the first temperature to the second temperature can be clearly transferred to the reproducing layer.

Further, each magnetic domain of the recording layer can be enlarged and transferred to the reproducing layer without applying a magnetic field (including an alternating magnetic field) for expanding the magnetic domain. The invention according to claim 3 is:
3. A reproducing apparatus for reproducing a signal from a magneto-optical recording medium according to claim 2, wherein the magnetic head applies a DC magnetic field to the magneto-optical recording medium, and irradiates the magneto-optical recording medium with laser light, and reflects the reflected light. It is a reproducing apparatus including an optical head for detecting.

According to a third aspect of the present invention, when a laser beam is emitted from the optical head and a DC magnetic field is applied from the magnetic head, the temperature of the mask layer of the magneto-optical recording medium is lower than the first temperature. Region retains in-plane magnetization, the region from the first temperature to the second temperature changes to a perpendicular magnetization film, and the region above the second temperature loses magnetization. Further, a region of the reproducing layer having a temperature equal to or higher than the third temperature changes from an in-plane magnetic film to a perpendicular magnetic film. Then, the first of the recording layers
The magnetic domain existing in the region below the temperature is prevented from being transferred to the reproducing layer by the in-plane magnetic film of the mask layer. In the recording layer, the magnetic domain existing in the region of the second temperature or higher is prevented from being transferred to the reproducing layer by exchange coupling due to the region where the magnetization of the mask layer has disappeared, and the region where the magnetization of the mask layer has disappeared. Even when the magnetic field is transferred to the reproducing layer by magnetostatic coupling, magnetization in the same direction as the direction of the DC magnetic field appears in the region of the reproducing layer adjacent to the region where the magnetization of the mask layer disappears due to the DC magnetic field applied from the magnetic head. However, the magnetization of the magnetic domain of the recording layer is not reflected. Then, of the recording layer, only the magnetic domains existing in the region from the first temperature to the second temperature are transferred to the mask layer by exchange coupling, and the magnetic domains transferred to the mask layer are reproduced by enlarging the magnetic domains. Transferred to the layer. The magnetic domain transferred to the reproducing layer is detected by a laser beam.

Therefore, according to the third aspect of the present invention, the magnetic domains of the recording layer existing in the region at the second temperature or higher during the reproduction of the signal are magnetostatically coupled via the region where the magnetization of the mask layer has disappeared. Thus, only the magnetic domains existing in the region from the first temperature to the second temperature can be clearly transferred to the reproducing layer without being transferred to the reproducing layer. Further, each magnetic domain of the recording layer can be enlarged and transferred to the reproducing layer without applying a magnetic field (including an alternating magnetic field) for expanding the magnetic domain.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to the drawings. Referring to FIG. 1, a magneto-optical recording medium 10 according to the present invention includes a light-transmitting substrate 1, an underlayer 2,
It includes a reproducing layer 3, a mask layer 4, a recording layer 5, and a protective layer 6. The translucent substrate 1 is made of glass, polycarbonate, or the like, the underlayer 2 is made of SiN, and the reproducing layer 3 is
The mask layer 4 is made of rare earth-rich GdFeCo.
GdxFe1-x (x: 0.25 to 0.35), the recording layer 5 is made of TbFeCo, and the protective layer 6 is
It is made of SiN. Then, SiN constituting the underlayer 2,
GdFeCo forming the reproducing layer 3, GdxFe1-x (x: 0.25 to 0.35) forming the mask layer 4, TbFeCo forming the recording layer 5, and SiN forming the protective layer 6 are formed by DC sputtering. Alternatively, it is formed by an RF sputtering method.

The thickness of each layer is 40 to 8 for the underlayer 2.
0 nm, reproduction layer 3 is 50 to 200 nm, and mask layer 4 is 5
The recording layer 5 has a thickness of 30 to 100 nm, and the protective layer 6 has a thickness of 40 to 80 nm. The base layer 2 is made of a transparent substrate 1
When the reproducing layer 3 is directly formed thereon, it is used to prevent the magnetic properties of the reproducing layer 3 from being deteriorated. After forming the base layer 2, the base layer 2 is sputter-etched by a predetermined thickness. The reproduction layer 3 may be formed.

The reproducing layer 3 is an in-plane magnetized film at room temperature.
The magnetic layer changes into a perpendicular magnetization film at about 00 ° C. The mask layer 4 is an in-plane magnetized film at room temperature,
This is a magnetic layer that changes into a perpendicular magnetic film at about 200 ° C. and disappears at about 200 ° C. Here, the temperature at which the mask layer 4 changes from an in-plane magnetization film to a perpendicular magnetization film is defined as a first temperature T1, the temperature at which magnetization disappears is defined as a second temperature T2, and the reproducing layer 3 is shifted from the in-plane magnetization film to a perpendicular magnetization film. Assuming that the temperature at which the film changes is a third temperature T3, the first temperature T1 is in the range of 120 to 170 ° C., the second temperature T2 is in the range of 150 to 220 ° C.,
The third temperature T3 is in a range from 90 to 120C.

GdxFe1-x constituting the mask layer 4
Is a magnetic film which is an in-plane magnetized film at room temperature and whose magnetization disappears at a predetermined temperature or higher when the content x of Gd is in the range of 0.25 to 0.40. By setting x in the range of 0.25 to 0.35, a magnetic film is obtained which changes from an in-plane magnetic film to a perpendicular magnetic film at a first temperature and disappears at a second temperature.

FIG. 2 shows GdxFe1-x (x: 0.25 to
0.35) is shown. The target is Gd and Fe
Gd is set to 0.25 to 0.3 by applying RF power to each target independently and performing sputtering.
GdFe contained in the range of 5 can be formed. Referring to FIG. 3, each magnetic domain of recording layer 5 of magneto-optical recording medium 10 is
A mechanism for transferring images with high resolution will be described. When the laser beam LB is irradiated from the reproduction layer 3 side, the temperature distribution becomes steep on the side of the traveling direction DR1 from the optical axis LB0 of the laser beam LB, and a broad temperature distribution is provided on the rear side of the traveling direction DR1 from the optical axis LB0. Distribution.

Based on the temperature distribution, the magnetic domain 5 of the recording layer 5
The region of 0 becomes a predetermined temperature or higher. Further, in the mask layer 4, a region at or above the first temperature T1 changes from an in-plane magnetization film to a perpendicular magnetization film, and magnetization of the region at or above the second temperature T2 disappears. Then, of the reproducing layer 3, the third temperature T3
The above region changes from an in-plane magnetization film to a perpendicular magnetization film. Then, in the region of the mask layer 4 adjacent to the magnetic domain 50 of the recording layer 5, the magnetic domain 40 having the magnetization 41 in the same direction as the magnetization 51 of the magnetic domain 50 appears by exchange coupling. In this case, the magnetic domains 52 and 53 existing on the lower temperature side than the magnetic domains 50 of the recording layer 5.
Are transferred to the reproduction layer 3 by the in-plane magnetization 43 of the mask layer 4, and the magnetic domain 54 existing on the higher temperature side than the magnetic domain 50,
In the region 55, transfer to the reproducing layer 3 by exchange coupling is prevented by the region 42 in which the magnetization of the mask layer 4 has disappeared. Therefore,
Only the magnetic domain 50 of the recording layer 5 is used as the magnetic domain 40 as the mask layer 4.
The magnetic domains 40 of the mask layer 4 are transferred by exchange coupling to
The magnetic domain 30 having the magnetization 31 in the same direction as the magnetization 41 is transferred to the reproducing layer 3 by exchange coupling. In this case, the reproducing layer 3 changes from the in-plane magnetic film to the perpendicular magnetic film at the third temperature T3 lower than the mask layer 4, so that the magnetic domain 30 of the reproducing layer 3 is changed.
Is larger than the magnetic domain 40 of the mask layer 4. On the other hand, the magnetic domains 54 and 55 existing on the higher temperature side than the magnetic domains 50 of the recording layer 5 may be transferred to the reproducing layer 3 by magnetostatic coupling through the region 42 where the magnetization of the mask layer 4 has disappeared. In the present application, a DC magnetic field 7 is applied from the outside. Then, the reproducing layer 3 adjacent to the region 42 where the magnetization of the mask layer 4 has disappeared.
Region 32 has magnetization in the same direction as DC magnetic field 7.
Further, since a region 33 adjacent to the region 32 of the reproducing layer 3 can also be changed to a perpendicular magnetization film, the magnetic domain of the recording layer 5 may be transferred, but the region 33 deviates from the spot diameter of the laser beam LB. Therefore, even if the magnetic domain of the recording layer 5 is transferred to the area 33, the signal reproduction is not affected.

As a result, only the magnetic domains 50 of the recording layer 5 are transferred to the mask layer 4 and the reproducing layer 3 by the exchange coupling, and the magnetic domains are enlarged and transferred, and the magnetic domains 30 of the reproducing layer 3 are detected by the laser beam LB. The magnetic domain 50 is detected. In the magneto-optical recording medium 10, the mask layer 4 has a first temperature T1.
On the lower temperature side, the in-plane magnetized film is retained to prevent the transfer of magnetic domains by exchange coupling from the recording layer 5 to the reproducing layer 3, and on the higher temperature side than the second temperature T2, the magnetization disappears and reproduction from the recording layer 5 is performed. It has a function of preventing transfer of magnetic domains to the layer 3 by exchange coupling, and transferring only magnetic domains of the recording layer 5 existing between the first temperature T1 and the second temperature T2 to the reproducing layer 3 by exchange coupling. It is a magnetic material.

The rotation speed of the magneto-optical recording medium 10 is set to 2.0 to
3.0 m / s, the intensity of the irradiated laser beam LB is 1.5 to
By setting the power to 3.0 mW, the first
The area not less than the temperature T1 and not more than the second temperature T2 can be set to be about the shortest domain length of the recording layer 5, and each magnetic domain of the recording layer 5 can be independently transferred to the reproducing layer 3 by exchange coupling.

As is apparent from the above description, the magneto-optical recording medium 10 enlarges and transfers each magnetic domain of the recording layer 5 to the reproducing layer 3 by applying a DC magnetic field without applying an alternating magnetic field. Is a magneto-optical recording medium capable of reproducing
The strength of the magnetic field 7 is ± 50 to 200 Oe. The process of reproducing a signal from the magneto-optical recording medium 10 will be described with reference to FIG. Before the signal is reproduced, the recording layer 5
Magnetic domains having magnetizations having different directions depending on the signals to be recorded are formed, and the reproducing layer 3 and the mask layer 4 have in-plane magnetization (see FIG. 4A). Then, when the laser beam LB is irradiated from the reproduction layer 3 side, as described with reference to FIG. 3, only the magnetic domains 50 of the recording layer 5 become the magnetic domains 40 and 30 to the mask layer 4 and the reproduction layer 3. The magnetic domain 30 of the reproducing layer 3 is detected by the laser beam LB, and the magnetic domain 50 of the recording layer 5 is detected (see FIG. 4B). Then, the laser beam LB moves, and the magnetic domains 30, 4
When the temperatures of the regions 0 and 50 decrease, the reproducing layer 3 and the mask layer 4 return from the perpendicular magnetization film to the in-plane magnetization film, and return to the initial state (see FIG. 4C). Therefore, FIG.
Through the process (c), each magnetic domain of the recording layer 5 is enlarged and transferred to the reproducing layer 3 to reproduce a signal.

The magnetic film constituting the mask layer 4 of the magneto-optical recording medium 10 is Gd _x Fe _1-x (x: 0.25 to 0.35)
Not limited to, (Gd _x Fe _1-x ) _1-y Al _y (x: 0.25 to
0.35, y: 0 to 0.15). FIG. 5 shows (Gd _x Fe _1-x ) _1-y Al _y (x: 0.25 to 0.35,
y: 0 to 0.15). Target is G
GdFeAl containing Gd in the range of 0.25 to 0.35 can be formed by independently applying RF power to each target and performing sputtering. (Gd _x Fe _1-x ) _1-y Al _y (x: 0.25 to
(0.35, y: 0 to 0.15) is also a magnetic film in which the magnetization changes from an in-plane magnetization film to a perpendicular magnetization film at the first temperature T1 and disappears at the second temperature T2.

Further, (Gd _x Fe _1-x ) _1-y Al _y (x:
(0.25 to 0.35, y: 0 to 0.15), the second temperature T2 differs depending on the Al content. FIG. 6 shows (Gd ₂₅ Fe ₇₅ ) _1-y Al _y (y: 0 to 0.1) with respect to the Al content.
5) shows a change in the Curie temperature (= second temperature T2). As the content of Al increases, (Gd ₂₅ Fe ₇₅ )
_{1- y Al y (y: 0~0.15} ) Curie temperature is lowered, the Curie temperature (= the second temperature T2): one hundred and fifty to twenty-two
The Al content for achieving 0 ° C. is 0 to 15 at. % Range.

Further, the mask layer 4 of the magneto-optical recording medium 10
May be a magnetic material obtained by adding one element selected from Cu, Si, Ti, Ta, Au, and Cr to GdFe. In this case, the added Cu, Si, Ti, Ta,
The amounts of Au and Cr are the same as in the case of Al. With reference to FIG. 7, a reproducing apparatus that reproduces a signal from the magneto-optical recording medium 10 by the magnetic domain expansion reproduction method will be described. The playback device 200 includes an optical head 20 and a playback signal amplification circuit 60.
, Synchronization signal generation circuit 70, servo circuit 80, servo mechanism 90, spindle motor 100, comparator 110, decoder 120, drive signal generation circuit 130
, The magnetic head drive circuit 140 and the laser drive circuit 15
0 and a magnetic head 160.

The optical head 20 irradiates the magneto-optical recording medium 10 with laser light and detects the reflected light. The reproduction signal amplification circuit 60 amplifies the focus error signal, tracking error signal, optical signal, and reproduction signal detected by the optical head 20 to predetermined levels, and outputs the focus error signal and the tracking error signal to the servo circuit 80. , And outputs a light signal to the synchronization signal generation circuit 70 and a reproduced signal to the comparator 110. Here, the optical signal is a signal based on a shape periodically formed of wobbles, pits, and the like on the magneto-optical recording medium 10, and is a signal serving as a reference for generating a so-called external synchronization signal.

The synchronizing signal generation circuit 70 generates a pulse signal corresponding to the center of each component constituting the optical signal based on the input optical signal, and a certain number of periodic signals exist between the components of the pulse signal. To generate a synchronization signal. Then, it outputs the generated synchronization signal to servo circuit 80, comparator 110, and decoder 120. The servo circuit 80 controls the servo mechanism 90 to perform focus servo and tracking servo of an objective lens (not shown, the same applies hereinafter) in the optical head 20 based on the input focus error signal and tracking error signal. The spindle motor 100 is rotated at a constant rotation speed in synchronization with the input synchronization signal. Servo mechanism 90
Is based on the control from the servo circuit 80.
Focus servo and tracking servo of the objective lens in the middle are performed. The spindle motor 100 rotates the magneto-optical recording medium 10 at a constant rotation speed.

The comparator 110 synchronizes with the synchronization signal from the synchronization signal generation circuit 70 and
Are compared at a predetermined level. The decoder 120 decodes the reproduction signal in synchronization with the synchronization signal from the synchronization signal generation circuit 70, and outputs it as reproduction data. The drive signal generating circuit 130 drives a drive signal for generating a DC magnetic field from the magnetic head 160 based on control from a control circuit (not shown) and a semiconductor laser (not shown, the same applies hereinafter) in the optical head 20. A drive signal for generating a DC magnetic field is output to the magnetic head drive circuit 140, and a drive signal for driving the semiconductor laser is output to the laser drive circuit 120. The magnetic head drive circuit 140 drives the magnetic head 130 based on the input drive signal, and the magnetic head 160 applies a DC magnetic field to the magneto-optical recording medium 10. Laser drive circuit 15
0 drives the semiconductor laser in the optical head 20 based on the input drive signal.
A laser beam having an intensity of 3.0 mW is applied to the magneto-optical recording medium 1.
Irradiate to zero.

When the magneto-optical recording medium 10 is mounted on the reproducing apparatus 200, the control circuit (not shown) operates the servo circuit 8 so that the spindle motor 100 rotates at a predetermined rotation speed.
0, the servo circuit 80 rotates the spindle motor 100 at a predetermined rotation speed as described above, whereby the magneto-optical recording medium 10 rotates at a predetermined rotation speed.
Further, the control circuit controls the drive signal generation circuit 130 so as to generate a drive signal for irradiating the magneto-optical recording medium 10 with laser light of a predetermined intensity from the optical head 20. As a result, the drive signal generation circuit 130 generates a drive signal for driving the semiconductor laser in the optical head 20 and outputs the drive signal to the laser drive circuit 150. Then, as described above, the laser drive circuit 150 drives the semiconductor laser in the optical head 20, and the optical head 20 irradiates the magneto-optical recording medium 10 with laser light of a predetermined intensity and detects the reflected light. Then, the detected focus error signal, tracking error signal, and optical signal are output to the reproduction signal amplification circuit 60, and the optical head 20
Focus servo and tracking servo of the middle objective lens are performed, and a synchronization signal is generated. Thereby, the laser beam from the optical head 20 is applied to the groove or land of the magneto-optical recording medium 10.

Thereafter, a control circuit (not shown) controls the drive signal generation circuit 130 to generate a drive signal for generating a DC magnetic field, and the drive signal generation circuit 130
A drive signal for generating a DC magnetic field is generated and output to the magnetic head drive circuit 140. Then, as described above, the magnetic head 160 writes the D
When the C magnetic field 7 is applied, each magnetic domain of the recording layer 5 of the magneto-optical recording medium 10 is enlarged and transferred to the reproducing layer 3 independently by the mask layer 4 by exchange coupling, and the optical head 20 is enlarged and transferred to the reproducing layer 3. By detecting the reflected light from the magnetic domain, a reproduced signal due to the magnetic domain expansion is detected.

The reproduced signal detected by the optical head 20 is supplied to the comparator 110 via the reproduced signal amplifier circuit 60.
After being synchronized by the comparator 110 in synchronization with the synchronization signal, the signal is decoded by the decoder 120 in synchronization with the synchronization signal and output as reproduction data. As a result, signals can be reproduced from the magneto-optical recording medium 10 in a magnetic domain enlarged manner only by applying a DC magnetic field by the reproducing apparatus 200.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a magneto-optical recording medium according to the present invention.

FIG. 2 shows conditions for forming GdxFe1-x (x: 0.25 to 0.35) constituting a mask layer of the magneto-optical recording medium shown in FIG.

FIG. 3 is a diagram illustrating a reproducing mechanism of the magneto-optical recording medium shown in FIG.

FIG. 4 is a diagram for explaining a process of reproducing a signal from a magneto-optical recording medium.

FIG. 5 shows a configuration of a mask layer of the magneto-optical recording medium shown in FIG. 1 (Gd _x Fe _1-x ) _1-y Al _y (x: 0.25 to 0.3)
5, y: 0 to 0.15).

FIG. 6 shows (Gd ₂₅ Fe ₇₅ ) _1-y Al _y (y: 0) shown in FIG.
FIG. 4 is a diagram showing the Al content dependence of the Curie temperature of ０．１0.15).

FIG. 7 is a block diagram of a playback device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 translucent substrate, 2 underlayer, 3 reproducing layer, 4 mask layer, 5 recording layer, 6 protective layer, 7 DC magnetic field, 10 magneto-optical recording medium, 30, 40, 50, 52, 53, 54,
55 magnetic domains, 31, 41, 43, 51 magnetization, 32, 3
3, 42 area, 20 optical head, 60 reproduction signal amplification circuit, 70 synchronization signal generation circuit, 80 servo circuit, 9
0 Servo mechanism, 100 Spindle motor, 110
Comparator, 120 decoder, 130 drive signal generation circuit, 140 magnetic head drive circuit, 150 laser drive circuit, 160 magnetic head

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Yamaguchi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. F-term (reference) 5D075 AA03 CF03 EE03 FF12

Claims (3)

[Claims] 1. A recording layer, comprising: a mask layer formed in contact with the recording layer; and a reproducing layer formed in contact with the mask layer, wherein the mask layer is an in-plane magnetic film at room temperature. A magneto-optical recording medium that is a magnetic layer that changes into a perpendicular magnetization film at a first temperature higher than room temperature and loses magnetization at a second temperature higher than the first temperature. 2. A recording layer, comprising: a mask layer formed in contact with the recording layer; and a reproduction layer formed in contact with the mask layer, wherein the mask layer is an in-plane magnetized film at room temperature. A magnetic layer that changes to a perpendicular magnetization film at a first temperature higher than room temperature and loses magnetization at a second temperature higher than the first temperature; and the reproducing layer is an in-plane magnetization film at room temperature. A magneto-optical recording medium that is a magnetic layer that changes into a perpendicular magnetization film at a third temperature lower than the first temperature. 3. A reproducing apparatus for reproducing a signal from a magneto-optical recording medium according to claim 2, wherein: a magnetic head for applying a DC magnetic field to the magneto-optical recording medium; An optical head for irradiating and detecting reflected light thereof.