JPH09312043A - Magneto-optical recording medium and is production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high recording density by successively forming at least a reproducing layer, nonmagnetic intermediate layer, auxiliary reproducing layer, cutoff layer and recording layer in this order on a transparent substrate in such a manner that each layer except for the nonmagnetic intermediate layer has a specified Curie temp. SOLUTION: A first dialectic layer 12 of a SiN is formed to 70nm thickness on a polycarbonate substrate 11 having 1.1μm track pitch, and then a reproducing layer 13 of Gd0.26 (Fe0.70 Co0.30 )0.74 having 0eum/cc magnetization at room temp. and >=350 deg.C Curie temp. is formed to 20nm to 26nm thickness thereon. Then a nonmagnetic intermediate layer 14 of 5nm thickness, an auxiliary reproducing layer 15 of 30nm thickness, a cutoff layer 16 of 10nm thickness, a recording layer 17 of 40nm thickness, and a second dielectric layer of 18 to 30nm thickness are formed in this order. A protective coating 19 comprising a UV- curing resin is applied on the second dielectric layer 18. It is especially preferable that the nonmagnetic intermediate layer consists of one or more kinds of nitrides of Si, Al, Ti and Ta considering the stability and tenseness of the thin film.

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 that records, reproduces, and erases information by using light, and more specifically, it records information recorded in a size not larger than the optical diffraction limit of reproduction light. The present invention relates to a readable magneto-optical recording medium that performs super-resolution reproduction.

[0002]

2. Description of the Related Art For the purpose of further increasing the density of a magneto-optical recording medium, a magnetic super-resolution capable of reproducing information recorded at a size smaller than the optical diffraction limit of reproduction light has been proposed. ing. This method uses at least the reproducing layer and the recording layer, and by using a certain area of the beam spot irradiated with the reproducing light as a mask, the beam spot is substantially the same as that in which the beam spot is reduced. It has an effect, and utilizes the fact that there is a light intensity distribution in the beam spot and that the temperature rise is large at the rear in the beam traveling direction.

This method is roughly classified into two methods. One is an extinction type method in which the reproduction layer is brought into a specific state in a region where the temperature is equal to or higher than a certain level to use as a mask (for example, Japanese Patent Laid-Open Nos. 1-143041 and 1).
No. 143042), the other is an embossing type method in which the reproducing layer is in a specific state before reproducing, and the information recorded in the recording layer is transferred to the reproducing layer in an area where the temperature becomes a certain temperature or more ( For example, there is JP-A-3-93058). In the latter method, the crosstalk with the adjacent track is small because the reproduction layer is in a specific state even in the adjacent track. In addition, a magnetic super-resolution of a double mask type including both an embossed type and an extinct type (for example, Japanese Patent Laid-Open No. 4-271).
No. 039) is also proposed.

The magnetic super-resolution mainly operates by controlling the exchange coupling force between the reproducing layer and the recording layer. In addition, the magnetic layer has a three-layer structure of a reproducing layer, a non-magnetic intermediate layer and a recording layer. At room temperature during reproduction, the reproducing magnetic field uniformly initializes the magnetization of the reproducing layer in the direction opposite to the reproducing magnetic field, and when the reproducing beam raises the temperature above a certain temperature, the magnetic domains are transferred from the recording layer to the reproducing layer by magnetostatic coupling. Magnetic super-resolution has also been reported (for example, Japanese Journal of Applied
Physics Vol. 35 (1996) pp.410-414).

[0005]

Mark edge recording has been adopted as a method adopted after the quadruple density medium as a method for increasing the recording density of the magneto-optical recording medium. Although the magnetic super-resolution occurs due to the transfer or disappearance of magnetic domains, conventionally, either the rising edge or the falling edge of the reproduction signal is steeper than the other. When magnetic super resolution and mark edge recording were combined, the jitter (fluctuation) of the slower edge hindered the improvement of recording density. It is said that the double-mask type magnetic super-resolution improves the balance between rising and falling to some extent, but further improvement is desired. The problem to be solved by the present invention is to achieve a higher recording density by making the rising and falling edges of the reproduction signal steep in a well-balanced manner compared to the conventional magnetic super-resolution medium.

[0006]

As a result of intensive studies, the present inventor has found that both rising and falling are steep to the limit by combining transfer due to magnetostatic coupling and disappearance of magnetic domains due to breakage of exchange coupling. The present invention has been completed by discovering that

That is, the present invention has a laminated structure in which at least a reproducing layer, a non-magnetic intermediate layer, a reproducing auxiliary layer, a cutting layer and a recording layer are laminated in this order on a transparent substrate, and the reproducing layer, the reproducing auxiliary layer, The Curie temperatures of the cutting layer and the recording layer are respectively T _c1 ,
If T _c2 , T _c3 , and T _c4 , then T _c3 <T _c4 , T _c2 >
A magneto-optical recording medium, characterized in that T _c4 and T _c1 > T _c4 . Further, at a temperature lower than a predetermined temperature T _s2 near the Curie temperature of the cutting layer, the recording magnetic domain recorded in the recording layer is a recording layer. Is transferred to the reproduction assisting layer, and by applying a reproducing magnetic field during reproduction, the temperature T
The magnetic domain of the auxiliary reproduction layer disappears at the temperature of _s2 or more, and the magnetic domain does not exist in the reproducing layer at room temperature because the magnetization is aligned in the direction of the reproducing magnetic field.
_At a temperature T _s1 less than _s2 , a recording magnetic domain is transferred from the reproduction auxiliary layer to the reproduction layer by magnetostatic coupling, and at the temperature T _s2 , the magnetic domain of the reproduction auxiliary layer disappears and the magnetic domain of the reproduction layer also disappears. It is a characteristic magneto-optical recording medium. The reproducing method of the present invention is the reproducing method of the magneto-optical recording medium for reproducing the information recorded on the recording layer as described above.

Hereinafter, the present invention will be described in detail.

A basic example of the structure of the magneto-optical medium of the present invention is shown in FIG.
Shown in In this example, the first dielectric layer 1 is formed on the transparent substrate 11.
2, the reproducing layer 13, the non-magnetic intermediate layer 14, the reproducing auxiliary layer 15,
Thin films are laminated in this order on the cutting layer 16, the recording layer 17, and the second dielectric layer 18. Usually, a protective coat 19 made of an ultraviolet curable resin or the like is applied on the second dielectric layer 18.

The principle of recording / reproducing of the magneto-optical recording medium of the present invention will be described with reference to FIG. Recording on the magneto-optical recording medium of the present invention is performed, for example, by applying a recording magnetic field 26 in the recording direction and raising the temperature of the recording layer 25 to a Curie temperature T _c4 or higher with a pulse laser beam 27. After the recording, the recording magnetic domain recorded in the process of the temperature decrease is transferred from the recording layer 25 to the reproduction auxiliary layer 23. At the time of reproducing, by applying the reproducing magnetic field 30 to the reproducing auxiliary layer 23, the magnetic domain of the reproducing auxiliary layer 23 which is in contact with the portion 32 having a predetermined temperature T _s2 or more near the Curie temperature T _c3 of the cutting layer 24 disappears. On the other hand, the reproduction layer 21
At room temperature, the magnetization is aligned in the direction of the reproducing magnetic field 30, so that no magnetic domain exists, that is, the first mask 33 is formed, and at the temperature T _s1 higher than room temperature and not higher than T _s2, reproduction assist is performed by magnetostatic coupling. Magnetic domains are transferred from the layer 23 to the reproducing layer 21. A very steep rise occurs in the reproduced signal as the magnetic domains are transferred. Further, above the temperature T _s2 , the magnetic domain of the reproduction auxiliary layer 23 disappears and at the same time the magnetic domain of the reproduction layer 21 disappears to become the second mask 35. With the disappearance of this magnetic domain, a very sharp fall occurs in the reproduced signal.

Needless to say, in order to maintain the recording magnetic domains recorded in the recording layer, the maximum temperature reached by the recording medium during reproduction must be less than the Curie temperature tT _c4 of the recording layer. , The magnetostatic coupling between the reproduction layer and the reproduction auxiliary layer
In order to maintain any temperature in the reproduction state, the Curie temperature T _c1 of the reproduction layer and the Curie temperature T of the reproduction auxiliary layer
Both _c2 must be higher than the Curie temperature T _{c4 of the} recording layer (T _c1 > T _c4 , T _c2 > T _c4 ). Further, in order for the cutting layer to function so as to obstruct the transfer of the recording magnetic domain recorded in the recording layer to the auxiliary reproduction layer at a predetermined temperature as described above and to eliminate the magnetic domain of the auxiliary reproduction layer, The Curie temperature T _c3 of the layer needs to be lower than the Curie temperature T _c4 of the recording layer (T _c3 <T _c4 ).

Now, referring to FIG. 3, it will be described in more detail how one recording magnetic domain temporally changes on the reproducing layer side. In the state of FIG. 3A, the recording domain does not appear in the reproducing layer due to the first mask 42. Here, the reproducing magnetic field is H _r , the reproducing layer magnetization is M _s1 , the reproducing layer coercive force is H _c1 ,
The domain wall energy of the reproducing layer is σ _w1 , the average size of the recording magnetic domain is r, and the static magnetic field from the auxiliary recording layer to the reproducing layer is H.
_{If s} is satisfied, the first mask 42 is generated if the following expression (I) is satisfied.

H _c1 <H _r + σ _w1 / (2M _s1 · r) −H _s (I) In order to satisfy the formula (I), M _s1 and H _s may be small at room temperature.

Next, as shown in FIG. 3B, T _s2 is higher than room temperature.
At the temperature T _s1 below, magnetic domains are transferred from the auxiliary reproduction layer to the reproduction layer by magnetostatic coupling. For that purpose, the following formula (II) may be satisfied in the vicinity of the region 43 where the temperature is higher than T _{s1 and} lower than T _s2 .

H _c1 <H _s −H _r −σ _w1 / (2M _s1 · r) (II) In order to satisfy this expression, if M _s1 and H _s are sufficiently large in the region 43 and H _c1 is small. Good.

Further, in order for the magnetic domains of the auxiliary reproduction layer to disappear in the region 44 above the temperature T _s2 , the magnetization of the auxiliary reproduction layer is set to M _s2 ,
The reproducing auxiliary layer has a film thickness h ₂ , the reproducing auxiliary layer has a coercive force H _c2 ,
Σ _{w2 is} the domain wall energy of the auxiliary recording layer, and σ is the interface domain wall energy due to exchange coupling between the reproducing layer and the recording layer through the cutting layer.
_{If i} , then the following equation (III) should be satisfied.

H _c2 <H _r + σ _w2 / (2M _s2 · r) −σ _i / (2M _s2 · h ₂ ) ... (III) By satisfying the formula (III), the magnetic domain of the reproduction auxiliary layer disappears,
Along with this, if the following equation (IV) is satisfied, disappearance of the magnetic domain of the reproducing layer, which is a change from (c) to (d) in FIG.

H _c1 <H _s + H _r + σ _w1 / (2M _s1 · r) (IV) When the magnetic domain is sufficiently smaller than the beam spot, the change from (a) to (b) in FIG. Simultaneously with the start of transfer, the entire magnetic domain instantly emerges in a wider area than the area 43, so that the rising edge of the reproduction signal becomes abrupt. Further, when the magnetic domain is sufficiently smaller than the beam spot, the change from (c) to (d) in FIG. 3 does not occur until the disappearance of the magnetic domain in the region 44 (III) and (IV) are satisfied at the same time. At the same time, the entire magnetic domain disappears instantly, and the fall of the reproduction signal becomes abrupt. According to the present invention based on the above principle, the rising and falling edges of the reproduced signal are sharp.

The reproducing magnetic field H _r is appropriately selected, and the composition (I) of each layer is adjusted by adjusting the composition and film thickness of each layer as described later.
~ (IV) is easily satisfied. Here, the reproducing magnetic field H _r is usually 50 to 400 Oe.

Since the magneto-optical recording medium of the present invention has two masks, it is a double mask type super-resolution medium. However,
In the conventional double-mask type super-resolution medium, as shown in FIG. 4, the change from (a) to (b) starts to be transferred in the region 53, and at the same time, the entire magnetic domain is instantly raised in a wider area than the region 53. However, the change from (c) to (d) changes because the magnetization of the second mask in the region 54 is in the same direction as the recording magnetic domain. The recording magnetic domain raised in () is caused by being gradually absorbed by the magnetic domain of the second mask as the disk moves, and the fall of the reproduced signal is gentler than the rise. Even in the conventional double mask type super resolution, it has been proposed in Japanese Patent Laid-Open No. 4-255946 that both the first and second masks face in the opposite direction to the recording magnetic domain. However, according to the experiments by the present inventors, Since it is difficult to adjust the transfer and disappearance in a well-balanced manner and the noise becomes high, the effect equivalent to that of the present invention cannot be obtained.

In the magneto-optical recording medium of the present invention, like the conventional double mask type super-resolution medium, the first mask masks the adjacent tracks, so that signal leakage (crosstalk) from the adjacent tracks occurs. small.

The reproducing layer and the reproduction assisting layer are made of a vertically magnetized film having a small coercive force, and the recording layer is made of a vertically magnetized film having a large coercive force. The cutting layer may be a perpendicular magnetic film or a perpendicular magnetic film at any temperature from room temperature to the Curie temperature.
The reproducing layer, the reproducing auxiliary layer, the cutting layer, and the magnetic layer of the recording layer are preferably made of a rare earth transition metal alloy. Equation (I
) And (II), the magnetizations of the reproduction layer and the reproduction auxiliary layer at room temperature are preferably 50 emu / cc or less.

The reproduction layer and the reproduction auxiliary layer are preferably rare earth-transition metal alloys mainly containing GdFeCo. Also a cutting layer,
The recording layer is preferably a rare earth transition metal alloy mainly containing TbFeCo or DyFeCo. The Curie temperature of the regeneration layer and regeneration auxiliary layer is 3 to maintain a high Kerr rotation angle during regeneration.
It is preferably at least 00 ° C. The Curie temperature of the recording layer is preferably 200 ° C. or higher and 300 ° C. or lower in view of recording sensitivity and reproduction stability. The Curie temperature of the cutting layer is preferably 100 ° C. or more and 200 ° C. or less, and particularly preferably 50 ° C. or more lower than the Curie temperature of the recording layer.

The thickness of the reproducing layer is 10 nm because it serves as a mask.
The above is necessary, and 50 nm or less is preferable in order to prevent the reproducing layer from being inverted due to the leakage magnetic field from the reproducing auxiliary layer, and conversely not excessively affecting the reproducing auxiliary layer.

In order to easily transfer from the reproduction auxiliary layer to the reproduction layer, the thickness of the reproduction auxiliary layer is preferably 10 nm or more,
The thickness is preferably 60 nm or less so that transfer from the recording layer to the auxiliary reproduction layer easily occurs. It is preferable that the thickness of the reproduction auxiliary layer is equal to or larger than that of the reproduction layer in order to prevent the reproduction auxiliary layer from being inverted due to the leakage magnetic field from the reproduction auxiliary layer and adversely affecting the reproduction auxiliary layer excessively.

The thickness of the cutting layer is preferably 5 nm or more and 50 nm or less. If it is thinner than 5 nm, it becomes difficult to break the exchange bond at the Curie temperature T _c3 , and if it is thicker than 50 nm, the transfer from the recording layer to the reproduction assisting layer near room temperature may become unstable and the recording sensitivity may be deteriorated. It is not preferable. The reproduction stability increases as the thickness of the recording layer increases, but it is preferably 15 nm or more and 60 nm or less in consideration of recording sensitivity.

The non-magnetic intermediate layer basically operates if it is a non-magnetic substance at a temperature of around room temperature or higher. The thickness of the non-magnetic intermediate layer is required to be 1 nm or more in order to break the exchange coupling, and 30 nm or less in order to magnetostatically couple the reproduction auxiliary layer and the reproduction layer.

The non-magnetic intermediate layer is preferably composed of one or more nitrides selected from nitrides of Si, Al, Ti and Ta, in view of stability and denseness of the thin film. .

The nonmagnetic intermediate layer is made of Al, Au, Ag,
By mainly composing one or more metal elements selected from the group consisting of Pt and Pd, it is possible to enhance the reflection of light from the non-magnetic intermediate layer and reduce the thickness of the reproducing layer. Therefore, it is expected to reduce the influence from the reproduction layer to the reproduction auxiliary layer and increase the margin of the reproduction magnetic field.

Further, by constructing the non-magnetic intermediate layer from one or more elements selected from rare earth elements, the reflection of light from the non-magnetic intermediate layer is enhanced without affecting the recording sensitivity for reproduction. It is possible to reduce the layer thickness.

The material of the substrate is polycarbonate,
A resin such as amorphous polyolefin or glass is preferable.

SiN, ZnS, A for the purpose of increasing the Kerr rotation angle on the laser beam incident side of the reproducing layer.
It is also effective to provide a first dielectric layer made of 1N or the like and having a thickness of about 70 nm. This thickness can be appropriately changed in order to adjust the reflectance of the medium and the reproduction signal strength. Further, in order to adjust the recording laser power and the like, on the side opposite to the laser light incident side, for example, Al having a thickness of about 20 nm is used.
It is also possible to provide a heat diffusion layer such as an alloy film, or to provide a second dielectric layer for protecting the thin film, and a protective film such as a protective coat made of an acrylic UV-curable resin as described above. is there.

Further, C is added to the magnetic layer to improve the corrosion resistance.
It is possible to add an element such as r, Ti, or Ta, but it is not particularly limited.

[0034]

The present invention will be described below in more detail with reference to examples.

(Example 1, Comparative Example 1 and Comparative Example 2) FIG.
A magneto-optical recording medium as shown in was prepared. First made of SiN on a polycarbonate (PC) substrate 11 with a track pitch of 1.1 μm by magnetron sputtering.
A dielectric layer 12 is formed to a thickness of 70 nm, and a reproducing layer 13 of Gd _0.26 (Fe _0.70 Co _0.30 ) _0.74 having a magnetization of 0 emu / cc (compensation composition) at room temperature and a Curie temperature of 350 ° C. or higher is formed on the dielectric layer 12.
0 nm or 26 nm, the nonmagnetic intermediate layer 14 made of SiN is 5 nm, the reproduction assisting layer 15 of Gd _0.25 (Fe _0.70 Co _0.30 ) _0.75 is 30 nm, and the Curie temperature is 160 ° C.
b _0.21 (Fe _0.97 Co _0.03 ) _{0.79 with} a cutting layer 16 of 10 n
m, Curie temperature of 270 ° C. Tb _0.22 (Fe _0.85 Co
_0.15 ) _0.78 recording layer 17 having a thickness of 40 nm and a second dielectric layer 18 made of SiN having a thickness of 30 nm were laminated in this order. Second
A protective coat 19 made of an ultraviolet curable resin was applied on the dielectric layer 18.

As Comparative Example 1, a magneto-optical recording medium similar to that of Example 1 was prepared except that the reproducing layer 13 and the nonmagnetic intermediate layer 14 were omitted. Further, as Comparative Example 2, a magneto-optical recording medium similar to that of Example 1 was prepared except that the reproduction assisting layer 15 and the cutting layer 16 were omitted.

A recording frequency of 15 MH was set on the manufactured magneto-optical recording medium at a linear velocity of 7.5 m / s so that the recording mark length would be 0.25 μm (which is regarded as half of the mark pitch).
Recording was carried out using a laser beam of 680 nm (NA of objective lens = 0.55) with z and duty of 33%. Using the same light, the reproduction laser power was 2.5 mW, the reproduction magnetic field was 150 Oe, and the carrier-to-noise ratio (C / N) was measured with a spectrum analyzer. In addition, the jitter (fluctuations on the time axis) at the front and rear edges of the reproduced waveform was measured with a jitter analyzer. Jitter measurement result is 0.25
The time corresponding to the mark of micron is 33T for 2T
Is shown as a ratio to the window width (1T). Table 1 shows the measurement results.

[0038]

[Table 1]

As shown in Table 1, as for C / N, compared with Comparative Example 1 which is an annihilation type super-resolution medium and Comparative Example 2 which is a conventional super-resolution medium using only magnetostatic coupling. The reproduction layer of Example 1 having a reproduction layer of 26 nm has a reproduction layer of about 3 dB and the reproduction layer of 20 nm
In the sample No. 2, it is about 2 dB higher. This is mainly because a steep rise was similarly obtained at the front and rear edges, as can be seen from the jitter values in Table 1. Since both the front and rear edge jitters are small, in Example 1, Comparative Example 1 and Comparative Example 2
Higher recording density is possible compared to.

When the crosstalk was measured after recording at the recording frequency of 7 MHz, in Example 1 and Comparative Example 3,
45 dB or less, whereas in Comparative Example 2 -30 dB
Therefore, it was shown that the present invention has a crosstalk as good as that of the conventional super-resolution medium using only magnetostatic coupling.

Example 2 Gd _0.26 (Fe _0.70 C
o _0.30 ) _0.74 reproducing layer 13 of 20 nm, non-magnetic intermediate layer 1
A magneto-optical recording medium having the same structure as in Example 1 was prepared _except that 4 was Al _0.98 Cr _0.02 alloy and the thickness was 10 nm.
The same measurement as in Example 1 was performed. Table 1 shows the measurement results.

Example 3 Gd _0.26 (Fe _0.70 C
o _0.30 ) _0.74 reproducing layer 13 of 20 nm, non-magnetic intermediate layer 1
A magneto-optical recording medium was manufactured in the same manner as in Example 1 except that Dy was 4 and the thickness was 10 nm, and the same measurement as in Example 1 was performed. Table 1 shows the measurement results.

As shown in Table 1, in Examples 2 and 3, even if the thickness of the reproducing layer was 20 nm, a high C / N and small jitter similar to those of the sample having the reproducing layer of 26 nm in Example 1 were obtained. Was given. This is mainly due to the fact that the Kerr rotation angle of the reproducing layer increases due to the high reflectance of the non-magnetic intermediate layer. In addition, although the reproducing characteristic of Example 2 is slightly better than that of Example 3, the recording power is higher by about 20%. By using a non-magnetic intermediate layer having a low thermal conductivity as in Example 3, a considerably high linear velocity can be supported and a high C / N and transfer rate can be obtained. Further, regarding the reproducing magnetic field, 110 to 220 for the sample having the reproducing layer thickness of 26 nm in Example 1.
In the range of Oe, the thickness of the reproducing layer in Examples 1 to 3 is 2
It was found that for the sample of 0 nm, good C / N was obtained in the range of 100 to 250 Oe, and the margin of the reproducing magnetic field was expanded by reducing the thickness of the reproducing layer.

[0044]

As is clear from the above description, according to the present invention, it is possible to read information recorded with a size far exceeding the optical diffraction limit of reproduction light with a high CNR. Further, the magneto-optical recording medium and the reproducing method thereof according to the present invention are suitable for edge recording because the jitter of both the rising edge and the falling edge of the reproduced signal is small. Further, since the crosstalk is small, a recording density exceeding that of the conventional double mask type super resolution medium is possible.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an example of a laminated structure of a magneto-optical recording medium of the present invention.

FIG. 2 is a conceptual diagram showing the principle of super-resolution reproduction of the magneto-optical recording medium of the present invention.

FIG. 3 is a conceptual diagram showing a temporal transition of transfer and disappearance of a recording magnetic domain on a reproducing layer during reproduction of the magneto-optical recording medium of the present invention.

FIG. 4 is a conceptual diagram showing the temporal transition of the transfer of a recording magnetic domain on the reproducing layer and the absorption into the second mask during reproduction of a conventional double-mask type super-resolution magneto-optical recording medium.

[Explanation of symbols]

11 Transparent Substrate 12 First Dielectric Layer 13, 21 Reproducing Layer 14, 22 Non-Magnetic Intermediate Layer 15, 23 Reproducing Auxiliary Layer 16, 24 Cutting Layer 17, 25 Recording Layer 18 Second Dielectric Layer 19 Protective Coating 26 Recording Magnetic Field 27 recording pulse laser beam 28 medium moving direction 29 area where recording layer has reached Curie temperature T _c4 or higher 30 reproducing magnetic field 31, 41, 51 reproducing laser beam and beam spot 32 predetermined temperature T near the Curie temperature T _{c3 of the} cutting layer _s2
The above parts 33, 42, 52 First masks 34, 43, 53 Regions where magnetic domains are transferred to the reproducing layer 35, 44, 54 Second masks 45, 55 Recording magnetic domains

Claims (8)

[Claims] 1. A reproducing substrate, a non-magnetic intermediate layer, a reproduction auxiliary layer, a cutting layer, and a recording layer are laminated in this order on a transparent substrate, and the reproduction layer, the reproduction auxiliary layer, and the cutting layer. , The Curie temperatures of the recording layers are T _c1 , T _c2 , T _c3 and T, respectively.
_A magneto-optical recording medium, characterized in that when _c4 , T _c3 <T _c4 , T _c2 > T _c4 , T _c1 > T _c4 . 2. _Below a predetermined temperature T _s2 near the Curie temperature of the cutting layer, the recording magnetic domain recorded in the recording layer has been transferred from the recording layer to the reproduction auxiliary layer, and by applying a reproduction magnetic field during reproduction, In the reproducing auxiliary layer, the magnetic domain of the reproducing auxiliary layer disappears at the temperature above the temperature T _s2 , and in the reproducing layer, the magnetization is aligned in the direction of the reproducing magnetic field at room temperature, so that there is no magnetic domain. At a temperature T _s1 which is higher than the temperature T _s2 , a recording magnetic domain is transferred from the reproduction auxiliary layer to the reproduction layer by magnetostatic coupling, and at the temperature T _s2 , the magnetic domain of the reproduction auxiliary layer disappears and at the same time the magnetic domain of the reproduction layer also disappears. The magneto-optical recording medium according to claim 1, which is erased. 3. The reproducing layer, the reproducing auxiliary layer, the cutting layer and the recording layer are made of a rare earth transition metal alloy, and the magnetization of the reproducing layer and the reproducing auxiliary layer at room temperature is 50 emu / cc or less. The magneto-optical recording medium according to claim 1 or 2. 4. The magneto-optical recording medium according to claim 3, wherein the reproduction layer and the reproduction auxiliary layer are made of a rare earth transition metal alloy mainly containing GdFeCo. 5. The non-magnetic intermediate layer is Si, Al, Ti, Ta.
The magneto-optical recording medium according to claim 1 or 2, wherein the magneto-optical recording medium is composed of one or more nitrides selected from the above-mentioned nitrides. 6. The non-magnetic intermediate layer is made of Al, Au, Ag, P.
The magneto-optical recording medium according to claim 1 or 2, which is mainly composed of one or more metal elements selected from the group consisting of t and Pd. 7. The magneto-optical recording medium according to claim 1, wherein the non-magnetic intermediate layer is composed of one or more elements selected from rare earth elements. 8. A reproducing auxiliary is performed by transferring a recording magnetic domain recorded in the recording layer from the recording layer to a reproducing auxiliary layer at a temperature lower than a predetermined temperature T _s2 near the Curie temperature of the cutting layer and applying a reproducing magnetic field during reproducing. In the layer, the magnetic domain of the auxiliary reproduction layer at the temperature above the temperature T _s2 is extinguished, and in the reproducing layer, the magnetization is aligned in the direction of the reproducing magnetic field at room temperature so that the magnetic domain does not exist. Temperature T less than _s2
The magnetic domain is transferred from the reproduction auxiliary layer to the reproduction layer by magnetostatic coupling at _s1 , and the magnetic domain of the reproduction auxiliary layer disappears at the same time as the magnetic domain of the reproduction auxiliary layer disappears at the temperature T _s2. 8. A method of reproducing the magneto-optical recording medium according to any one of items 7 to 7.