JP3443410B2 - Magneto-optical recording medium and reproducing method thereof - Google Patents

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 such as a magneto-optical disk, a magneto-optical tape, a magneto-optical card applied to a magneto-optical recording apparatus and a reproducing method thereof.

[0002]

2. Description of the Related Art At present, in a magneto-optical recording medium such as a magneto-optical disk which has been put into practical use as a new storage medium capable of realizing a higher recording density than a magnetic recording medium in which recording and reproduction are performed by using a magnetic head. Recently, research and development have been actively conducted to further improve the recording density.

The recording density of the above magneto-optical recording medium is
It depends on the size of the light beam used for reproduction on the recording medium. For example, when the recording bit diameter and the recording bit interval are smaller than the beam diameter of the light beam focused on the magneto-optical recording medium, a plurality of recording bits are present in the light beam, and each recording beam has a plurality of recording bits. The two recording bits cannot be separated and reproduced, and the reproduction characteristics deteriorate.

In order to solve the above-mentioned drawbacks of the magneto-optical recording medium, recently, a method of reproducing recorded bits smaller than the size of the light beam has been proposed.

Usually, in optical recording, a light beam is narrowed down to the diffraction limit by a condenser lens, so that its light intensity distribution becomes Gaussian distribution, and the temperature distribution on the recording medium also becomes almost Gaussian distribution. Therefore, the region having a temperature equal to or higher than a certain temperature is smaller than the light beam. Therefore, the above-mentioned method of reproducing a recording bit smaller than the size of the light beam attempts to involve only a region having a certain temperature or higher in the reproduction.

In carrying out the above method, an optical system provided with an exchange-coupling bilayer film comprising a read layer which is a perpendicular magnetization film having a high coercive force at room temperature and a recording layer which is a perpendicular magnetization film having a small coercive force at room temperature. A magnetic disk is used. Recording on this magneto-optical disk is performed by a usual magneto-optical recording method. The reproduction of the bits recorded on the magneto-optical disk is performed as follows. That is, an auxiliary magnetic field is applied in advance to the read layer by the auxiliary magnetic field generator, and initialization is performed so that the magnetization direction of the read layer is aligned in a predetermined direction. Next, the magneto-optical disk is irradiated with a reproducing beam to raise the local temperature and the magnetization information of the recording layer is transferred to the reading layer. By doing so, it is possible to reproduce the information of only the part where the temperature of the central part of the part irradiated with the reproduction beam has risen. Therefore, even a recording bit smaller than the light beam can be read.

However, when the above-mentioned magneto-optical disk is used, the auxiliary magnetic field generator must apply the auxiliary magnetic field before the reproducing operation. Also, during playback,
The recording bit transferred from the recording layer to the reading layer remains as it is even if the temperature of the portion is lowered. Therefore, when the light beam is moved to reproduce the next recorded bit, the previous recorded bit is still present in the light beam, and the remaining bits are also reproduced, which causes noise and It becomes a limitation when increasing the density.

Therefore, the inventors of the present application do not need an auxiliary magnetic field generator for initialization prior to the reproducing operation, and can avoid mixing of a signal from an adjacent bit (previous recording bit) which causes noise. A magneto-optical recording medium has been previously proposed (Japanese Patent Application No. 4-74605). This magneto-optical recording medium and the reproducing method using the same will be described below with reference to FIG. Incidentally, FIG. 7A is a view of the magneto-optical recording medium as viewed from the light beam irradiation side, and FIG. 7B is a view taken along the line AA of the magneto-optical recording medium of FIG. The magnetic states of the magnetic layers 51 and 52 are shown.

The above magneto-optical recording medium has a recording layer 52 having a Curie temperature point of about 150 ° C. and a reading layer 51 showing an in-plane magnetization state at room temperature and a perpendicular magnetization state at a reading temperature of about 50 ° C. or higher. And have. For recording on this magneto-optical recording medium, a recording magnetic field is applied to the magneto-optical recording medium and a high-power light beam is applied to the magneto-optical recording medium to raise the temperature of the recording layer 52 to near the Curie temperature. Done by. As a result, recording bits are formed on the recording layer 52.

On the other hand, the reproduction of the information recorded on the magneto-optical recording medium is performed as follows. First, the magneto-optical recording medium is irradiated with a light beam having a power lower than that at the time of recording. At this time, the light beam is moving in the direction indicated by arrow P relative to the recording medium, and the portion of the magneto-optical recording medium where the temperature is highest is located at a position deviated rearward from the center of the light beam. Will exist. For this reason, the region 83 (center of the region) where the temperature of the readout layer 51 rises to about 50 ° C. or higher due to the irradiation of the light beam to enable reading is located behind the region 72 (center of the region) irradiated with the light beam. It will be in a position deviated from. Then, only in the region 83, the read layer 51 is in a perpendicular magnetization state, and receives the exchange coupling force from the recording layer 52, and the magnetization direction of the read layer 51 becomes the same as the magnetization direction of the recording layer 52. Here, since there is a gap between the light beam irradiation region 72 and the region 83 that can be read due to the temperature rise in the readout layer 51, the information that is actually reproduced is in the light beam irradiation region 72. , And the information 63 existing in the readable area 83 is not reproduced.

As described above, since only the high temperature region in the light beam irradiation region 72 functions as a kind of optical aperture, the effective light spot contributing to the information reproduction is reduced and the detection resolution is improved. As a result, even if the recorded bits are smaller than the size of the light beam, it is possible to separately reproduce the recorded bits. And
The part of the read layer 51 where the temperature does not rise or the part where the temperature drops shows in-plane magnetization, so that the magneto-optical effect does not appear, and the information recorded in the recording layer 52 is masked by the in-plane magnetization of the read layer 51. It will not be read. As a result, it is possible to avoid mixing of signals from adjacent bits, which is a cause of noise. Further, the auxiliary magnetic field generator for initialization prior to the reproducing operation is unnecessary.

[0012]

FIG. 15 shows a case where the recording density is further increased in the above-mentioned magneto-optical recording medium.
Please consider by referring to. Incidentally, FIG. 7A is a view of the magneto-optical recording medium viewed from the light beam irradiation side, and FIG.
Shows the magnetization state of each of the magnetic layers 51 and 52 in the AA line cross section of the magneto-optical recording medium of FIG.

When the light beam irradiation region 72 in the readout layer 51 and the range 83 that can be read out due to the temperature rise due to the light beam irradiation are set in the same manner as in the case shown in FIG. 14, the light beam irradiation region. There are two pieces of information (information 93 and 93 ') existing in 72 and in the readable area 83, and it becomes impossible to separately reproduce each recording bit.

The present invention has been made in view of the above, and an object thereof is to provide the characteristics of the magneto-optical recording medium previously proposed by the inventor of the present application (such as avoiding signal mixing from the previous recording bit). A magneto-optical recording medium capable of improving the recording density by separately reproducing each recording bit even when the recording density is further increased as compared with the magneto-optical recording medium. To provide a method.

[0015]

In order to solve the above problems, the magneto-optical recording medium of the present invention has a recording layer which exhibits a perpendicular magnetization state at room temperature and maintains the perpendicular magnetization state from room temperature to the Curie temperature T _2. And is arranged on the incident side of the light beam with respect to the recording layer, and exhibits an in-plane magnetization state at room temperature, transitions to a perpendicular magnetization state at a temperature T ₁ or higher, and again at a temperature T ₃ or higher. And a middle layer which is provided between the read layer and the recording layer and which exhibits a perpendicular magnetization state at room temperature while transitioning to an in-plane magnetization state at a temperature of T ₃ or higher. ₁ , T ₂ , T ₃ are T ₁ <T
It is characterized in that the relationship of ₃ <T ₂ is satisfied.

Further, the magneto-optical recording medium of the present invention exhibits a perpendicular magnetization state at room temperature and has a Curie temperature T ₂ from room temperature.
A recording layer which maintains a perpendicular magnetization state up to and a light beam incident side with respect to the recording layer, which exhibits an in-plane magnetization state at room temperature, and shifts to a perpendicular magnetization state at a temperature of T ₁ or higher, A read layer that exhibits an in-plane magnetization state again at T ₃ or higher, and a perpendicular magnetization state that is provided between the read layer and the recording layer, exhibits a perpendicular magnetization state at room temperature, and has a Curie temperature T ₃ from room temperature.
Up to the temperature T
_{It is characterized in that 1} , ₁ , T ₂ and T ₃ satisfy the relationship of T ₁ <T ₃ <T ₂ .

Further, the magneto-optical recording medium of the present invention exhibits a perpendicular magnetization state at room temperature and has a Curie temperature T ₂ from room temperature.
A recording layer which maintains a perpendicular magnetization state up to and a light beam incident side with respect to the recording layer, which exhibits an in-plane magnetization state at room temperature, and shifts to a perpendicular magnetization state at a temperature of T ₁ or higher, A read layer that exhibits an in-plane magnetization state at T ₃ or higher and a read layer that is provided between the read layer and the recording layer, exhibits an in-plane magnetization state at room temperature, and has a Curie temperature T ₃ from room temperature.
Up to the temperature T
_{It is characterized in that 1} , ₁ , T ₂ and T ₃ satisfy the relationship of T ₁ <T ₃ <T ₂ .

Further, according to the reproducing method of the magneto-optical recording medium of the present invention, a region having a temperature of T ₁ or more and less than T ₃ is formed in the irradiation region of the reproducing light beam in the magneto-optical recording medium, and in the region, It is characterized in that the magnetization information of the recording layer is transferred to the reading layer and reproduced.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in Examples 1 to 3.

Reference Example 1 The following will describe one reference example of the present invention with reference to FIGS. 1, 7 and 8.

The magneto-optical disk as the magneto-optical recording medium of this reference example has a substrate 4, a transparent dielectric film 5, a readout layer 1, an intermediate layer 3, a recording layer 2 and a transparent dielectric film as shown in FIG. 6 and the overcoat film 7 are laminated in this order.

The read layer 1 exhibits an in-plane magnetization state at room temperature and shifts to a perpendicular magnetization state at a read temperature of temperature T ₁ or higher (see FIG. 8). As the read layer 1, for example, rare earth elements are used. Transition metals can be used.

The magnetic moments of the rare earth metal and the transition metal have different temperature characteristics, and the magnetic moment of the transition metal becomes larger than that of the rare earth metal at high temperatures. Therefore, when the readout layer 1 having the above characteristics is formed of a rare earth transition metal, the content of the rare earth metal is set to be higher than the compensating composition at room temperature, and the in-plane magnetization does not appear in the perpendicular magnetization at room temperature. At the same time, perpendicular magnetization is performed at the temperature T ₁ . As a result, when the temperature of the part irradiated with the light beam rises to the temperature T ₁ , the magnetic moment of the transition metal becomes relatively large and balances with the magnetic moment of the rare earth metal, so that the perpendicular magnetization is exhibited as a whole. Become.

The read-out layer 1 has a relatively large perpendicular magnetic anisotropy, and for example, the thickness of Dy is 50 nm.
_0.35 (Fe _0.5 Co _0.5 ) _0.65 can be used.
The temperature T _{1 at which} the read layer 1 changes from in-plane magnetization to perpendicular magnetization is preferably 40 ° C to 70 ° C.

The intermediate layer 3 has a perpendicular magnetization state at room temperature.
The room temperature to the Curie temperature T ₃Perpendicular magnetization state
Is a perpendicularly magnetized film that holds (see FIG. 8). This middle layer
Curie temperature T of 3₃Is the in-plane reading layer 1 described above.
Temperature T at which magnetization changes to perpendicular magnetization₁Set higher than
Done (T₁<T₃). As the intermediate layer 3, for example, the film thickness
Is 50 nm Ho_0.28(Fe_0.85Co_0.15)_0.72, Film thickness
Is Dy of 50 nm_0.21Fe_0.79Can be used
It The Curie temperature T of the intermediate layer 3₃Is 60 ° C to 90
C is preferred.

The recording layer 2 has a perpendicular magnetization state at room temperature.
The room temperature to the Curie temperature T ₂Perpendicular magnetization state
Is a perpendicularly magnetized film that holds (see FIG. 8). This recording layer
Curie temperature T of 2₂Is the curie of the intermediate layer 3 described above.
Temperature T₃Higher than (T₃<T₂). That is, above
Temperature T₁, T₂, T₃Is T₁<T₃<T₂ Have a relationship. As the recording layer 2, for example, the film thickness
Is Dy of 50 nm_0.23(Fe_0.82Co_0.18)_0.77use
can do. The Curie temperature T of the recording layer 2
₂Is preferably 120 ° C to 180 ° C.

The transparent dielectric film 5 is provided in order to improve the reproduction characteristics, that is, to enhance the magnetic Kerr rotation angle by the antireflection function.
N, SiN, AlSiN, AlSiON, TiO2 or the like can be used, and the film thickness thereof is set to a value obtained by dividing 1/4 of the wavelength of the reproduction light by the refractive index. For example, if the wavelength of the reproduction light is 8
When the thickness is 00 nm, the film thickness of the transparent dielectric film 2 is 10 nm to 8 nm.
It becomes about 0 nm. The transparent dielectric film 6 is a protective film made of a nitride such as AlN and has a film thickness of 50 n.
m.

In the above structure, recording on the magneto-optical disk is performed by applying a recording magnetic field to the magneto-optical disk and condensing the laser beam 8 of high power by the objective lens 9 to irradiate the magneto-optical disk. This is done by raising the temperature of layer 2 to near the Curie temperature T ₂ . As a result, recording bits are formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
Incidentally, FIG. 10A is a view of the magneto-optical disk as seen from the irradiation side of the laser beam 8, and FIG. 8B is a view taken along the line AA of the magneto-optical disk of FIG. Magnetic layer 1.2
-It shows the magnetization state of 3.

First, the magneto-optical disk is irradiated with the laser beam 8 having a power lower than that at the time of recording. At this time, the laser beam 8 is moving relative to the magneto-optical disk in the direction indicated by the arrow Q, and the portion of the magneto-optical disk where the temperature is highest is deviated rearward from the center of the laser beam 8. Will be in position. Therefore, the temperature of the readout layer 1 is changed to the temperature T by the irradiation of the laser beam 8.
_The region 33 (center of the region) that rises to ₁ or more is present at a position displaced rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. Further, the region 44 (center of the region) where the temperature of the intermediate layer 3 rises to the Curie temperature T ₃ or higher is the irradiation region 22 (center of the region) of the laser beam 8.
It is located at a position displaced backward with respect to.

Here, in the intermediate layer 3, the magnetization disappears in the region 44 where the temperature is the Curie temperature T ₃ or higher. On the other hand, the region other than the region 44 in the intermediate layer 3 shows a perpendicular magnetization state, and the exchange coupling force acting between the two layers of the recording layer 2 and the intermediate layer 3 causes the recording layer 2 to move.
The magnetization direction of is transferred to the intermediate layer 3.

Further, the read layer 1 exhibits a perpendicular magnetization state in the region 33 where the temperature rises to the temperature T ₁ or higher, while it exhibits an in-plane magnetization state in the regions other than the region 33. In this case, in the region of the read layer 1 that is inside the region 33 and outside the region 44, the magnetization direction of the intermediate layer 3 is read by the exchange coupling force acting between the two layers of the intermediate layer 3 and the read layer 1. Transferred to layer 1. That is, the magnetization information of the recording layer 2 is transferred to the reading layer 1 via the magnetization of the intermediate layer 3, and the magnetization direction of the reading layer 1 inside the region 33 and outside the region 44 is the recording layer 2. The same direction as the magnetization direction of.

As described above, the magnetization information of the recording layer 2 is transferred to the readout layer 1 via the magnetization of the intermediate layer 3, so that the Curie temperature T ₃ or higher of the intermediate layer 3 is reached. In the region 44 where the intermediate layer 3 is no longer magnetized, the magnetization information of the recording layer 2 is not transferred to the read layer 1. That is, the region 44 where the magnetization is no longer present in the intermediate layer 3
Then, the magnetization information of the recording layer 2 cannot apply the exchange coupling force to the reading layer 1. Therefore, the portion of the read layer 1 corresponding to the region 44 is in a free state in which the exchange coupling force from the intermediate layer 3 is not received, and its magnetization state is the characteristic of the read layer 1, that is, the perpendicular magnetic anisotropy. It depends on the size.

Since the read layer 1 of the present reference example has a relatively large perpendicular magnetic anisotropy, the read layer 1 retains the perpendicular magnetization state even in the region 44 where the exchange coupling force from the intermediate layer 3 does not exist. Therefore, in this reference example, an external magnetic field Hex for always aligning the magnetization directions of the read layer 1 corresponding to the region 44 in the same direction during reproduction is applied to the magneto-optical disk. Thus, information 13 ', 14' present in the region 44 to a temperature T ₃ or more is not being played.

As described above, the portion where the temperature becomes the highest on the magneto-optical disk during reproduction is located at a position deviated rearward from the center of the laser beam 8. For this reason,
In the irradiation region 22 of the laser beam 8, a part of the region 33 in which the temperature of the readout layer 1 becomes equal to or higher than the temperature T _{1 at} which the in-plane magnetization changes to the perpendicular magnetization, and the intermediate layer 3 has the Curie temperature T ₃ or higher. There will be a part of the area 44 that becomes Therefore, even if it exists in the area 33 where the temperature is equal to or higher than T ₁ , the information 14, 14 ′ that does not exist in the irradiation area 22 of the laser beam 8 is not reproduced.

Further, the region 33 in the readout layer 1
In the other regions, the in-plane magnetization state is maintained and the magneto-optical effect is not shown for the vertically incident light. Therefore, even if it exists in the irradiation area 22 of the laser beam 8, the information 12 ... Outside the area 33 where the temperature is equal to or higher than T ₁ is not reproduced.

From the above, the information reproduced by the irradiation of the laser beam 8 exists in the irradiation region 22 of the laser beam 8, and the temperature T at which the temperature of the readout layer 1 shifts from the in-plane magnetization to the perpendicular magnetization. present in the region 33 becomes ₁ or more, and, the intermediate layer 3 is only information 13 existing outside the area 44 of the Curie temperature T ₃ or more. As a result, in the magneto-optical disk of the present reference example, even if the recording bits are smaller than those of the magneto-optical recording medium previously proposed by the inventors of the present application (see Japanese Patent Application No. 4-74605), each recording bit is separated. It is possible to reproduce the recorded data, and the recording density can be remarkably improved.

Then, when the laser beam 8 moves to reproduce the next recorded bit, the temperature of the reproduction site is lowered and the read layer 1 is changed from the perpendicular magnetization to the in-plane magnetization.
Along with this, the region where the temperature is lowered does not exhibit the magneto-optical Kerr effect. Therefore, the information is not reproduced from the portion where the temperature is lowered, and the signal from the adjacent bit, which is a cause of noise, is not mixed.

Now, this reference example will be described more specifically. As target, Al, Gd, Dy, Ho, F
A polycarbonate disk substrate 4 having pregrooves and prepits was placed facing the target in a sputtering apparatus equipped with e and Co. The inside of this sputtering apparatus was evacuated to 1 × 10 ⁻⁶ Torr, then a mixed gas of argon and nitrogen was introduced into the apparatus, and electric power was supplied to an Al target to produce a gas pressure of 4 ×.
A transparent dielectric film 5 made of AlN was formed on the disk substrate 4 by performing sputter deposition at 10 ⁻³ Torr and a sputtering rate of 12 nm / min. This transparent dielectric film 5 is
As described above, the reproducing characteristic is improved, and the film thickness thereof is set to a value approximately 1/4 of the wavelength of the reproducing light divided by the refractive index. In this reference example, since the reproduction light having the wavelength of 800 nm is used, the film thickness of the transparent dielectric film 5 is set to 60 nm.

Next, the inside of the sputtering apparatus is again set to 1 × 1.
After evacuating to 0 ^-6 Torr, argon gas was introduced into the apparatus, and electric power was supplied to the targets of Dy, Fe and Co, the gas pressure was 4 × 10 ^-3 Torr, and the sputtering rate was 1
Sputter deposition was performed at 5 nm / min, and Dy _0.35 (Fe _0.5 Co _0.5 ) with a film thickness of 50 nm was formed on the transparent dielectric film 5.
_A readout layer 1 made of _0.65 was formed. The readout layer 1 was in the in-plane magnetization state at room temperature, transitioned to the perpendicular magnetization state at a temperature of 60 ° C. or higher (T ₁ = 60 ° C.), and the Curie temperature was 320 ° C.

Next, while stopping the electric power supplied to the Dy target, the electric power was supplied to the Ho target, and sputter deposition was performed under the same conditions as those for forming the read layer 1 described above. On top of the 50 nm thick Ho
_0.28 was formed (Fe _0.85 Co _0.15) intermediate layer 3 made of _0.72. The Curie temperature T _{3 of the} intermediate layer 3 is 90 ° C.
It was a perpendicular magnetization film.

Next, while stopping the electric power supplied to the Ho target, the electric power was supplied to the Dy target, and sputter deposition was performed under the same conditions as those for forming the readout layer 1 to thereby form the intermediate layer 3 described above. On top, Dy _0.23 with a film thickness of 50 nm
The recording layer 2 made of (Fe _0.82 Co _0.18 ) _0.77 was formed. The recording layer 2 was a perpendicular magnetic film having a compensation point at about room temperature, and its Curie temperature T ₂ was 160 ° C.

Next, a mixed gas of argon and nitrogen was introduced into the sputtering apparatus, and electric power was supplied to the Al target, the gas pressure was 4 × 10 ^-3 Torr, and the sputtering rate was 12.
A transparent dielectric film 6 made of AlN was formed on the disk substrate 4 by performing sputter deposition at nm / min. Here, the transparent dielectric film 6 may have a thickness sufficient to protect the magnetic layers (recording layer 2, intermediate layer 3, reading layer 1) from corrosion such as oxidation. 5 in the reference example
The film thickness was 0 nm.

Next, an ultraviolet curable resin was applied onto the transparent dielectric film 6 by spin coating and then irradiated with ultraviolet rays to form an overcoat film 7 on the transparent dielectric film 6. A thermosetting resin may be used as the overcoat film 7.

The laser beam 8 is focused and irradiated by the objective lens 9 onto the magneto-optical disk manufactured as described above, and the relative linear velocity of the laser beam 8 with respect to the magneto-optical disk is 10 m / s. The disc was rotated. Then, while continuously irradiating the laser beam 8 of 10 mW for recording, a modulating magnetic field of ± 15 kA / m was modulated at a frequency of 10 MHz and applied to the magneto-optical disk. Inversion magnetic domains with a length of 0.5 μm could be formed.

Thereafter, the power of the laser beam 8 is set to 2 mW.
Then, when the recorded information is reproduced with a constant magnetic field (external magnetic field Hex) of +5 kA / m being applied to the magneto-optical disk, a reproduction signal of frequency 10 MHz is generated according to the inverted magnetic domain formed in the recording layer 2. Could be obtained from the readout layer 1. Further, when a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk in a state where the laser beam 8 of 10 mW for recording was continuously irradiated, the recording layer 2 had a period of 0.5 μm. 0.
An inverted magnetic domain having a length of 25 μm could be formed.

Thereafter, the power of the laser beam 8 is set to 2 mW.
Then, when the recorded information was reproduced with a constant magnetic field (external magnetic field Hex) of +5 kA / m being applied to the magneto-optical disk, a reproduced signal of a frequency of 20 MHz was generated according to the reversed magnetic domain formed in the recording layer 2. Could be obtained from the readout layer 1.

Comparative Example As a comparative example of Reference Example 1 above,
Recording and reproduction similar to those in Reference Example 1 were performed using the magneto-optical disk having the structure shown in FIG. 14 in which the intermediate layer 3 does not exist in the magneto-optical disk of Reference Example 1. When recording was performed at a frequency of 10 MHz, the frequency 1
I was able to obtain a 0MHz playback signal, but 20MHz
When recording was performed at the frequency of 2, the adjacent recording information could not be separated, and the reproduction signal at the frequency of 20 MHz could not be obtained.

Example 1 The following will describe an example of the present invention with reference to FIGS. 2, 7 and 8.

The magneto-optical disk as the magneto-optical recording medium of this embodiment is the same as the reference example 1 except that the read layer 201 is used instead of the read layer 1 of the reference example 1.
The structure and characteristics of each layer other than the readout layer 201, that is, the substrate, the transparent dielectric film, the intermediate layer, the recording layer, the transparent dielectric film, and the overcoat film are the same as those of the magneto-optical disk of FIG. Since it is the same as the reference example 1,
Each of these layers has the same reference numeral as in Reference Example 1,
Detailed description is omitted here (see FIG. 7).

Like the readout layer 1 of Reference Example 1, the readout layer 201 exhibits an in-plane magnetization state at room temperature and has a temperature of T ₁
(See FIG. 8) Although it is in a perpendicular magnetization state at the above reading temperature, the reading layer 1 of Reference Example 1 has a relatively large perpendicular magnetic anisotropy, whereas the present Example The reading layer 201 has a relatively small perpendicular magnetic anisotropy. As the readout layer 201, a rare earth transition metal can be used, and the thickness is 50 nm, for example.
Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 can be used.

The temperature T _{1 at which} the read layer 201 changes from in-plane magnetization to perpendicular magnetization is preferably 40 ° C to 70 ° C. The Curie temperature T ₃ of the intermediate layer 3 is 60 ° C to 9 ° C.
0 ° C is preferred. Also, the Curie temperature T of the recording layer 2
₂ is preferably 120 ° C to 180 ° C. The temperatures T ₁ , T _2, and T ₃ are in the relationship of T ₁ <T ₃ <T ₂ .

In the above structure, recording on the magneto-optical disk is performed by applying a recording magnetic field to the magneto-optical disk and converging the laser beam 8 of high power by the objective lens 9 to irradiate the magneto-optical disk. This is done by raising the temperature of layer 2 to near the Curie temperature T ₂ . As a result, recording bits are formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
Incidentally, FIG. 10A is a view of the magneto-optical disk as seen from the irradiation side of the laser beam 8, and FIG. 8B is a view taken along the line AA of the magneto-optical disk of FIG. Magnetic layer 201
-It shows the magnetization states of 2.3.

First, the magneto-optical disk is irradiated with the laser beam 8 having a power lower than that at the time of recording. At this time, the laser beam 8 is moving relative to the magneto-optical disk in the direction indicated by the arrow Q, and the region 33 (region where the temperature of the reading layer 201 rises to the temperature T ₁ or higher by irradiation of the laser beam 8) The center) of the laser beam 8 exists at a position displaced rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. Further, the region 44 (center of the region) where the temperature of the intermediate layer 3 rises to the Curie temperature T ₃ or higher exists at a position displaced backward with respect to the irradiation region 22 (center of the region) of the laser beam 8. Become.

In this case, the intermediate layer 3 is the same as in Reference Example 1.
In the above, the magnetization direction of the recording layer 2 is transferred to the intermediate layer 3 by the exchange coupling force acting between the two layers of the recording layer 2 and the intermediate layer 3 in the region other than the region 44 where the perpendicular magnetization state is exhibited.

In the read layer 201 as well,
As in the first reference example, in the region inside the region 33 and outside the region 44, the magnetization information of the recording layer 2 is transferred to the read layer 201 via the magnetization of the intermediate layer 3, and thus the magnetization direction thereof is changed. Is in the same direction as the magnetization direction of the recording layer 2.

Here, the readout layer 201 of this embodiment is
Since the perpendicular magnetic anisotropy is relatively small, in the region 44 where the exchange coupling force from the intermediate layer 3 does not exist, the in-plane magnetization state occurs and the magneto-optical effect is not exhibited for the vertically incident light. Therefore, the recording layer 2 corresponding to the area 44 is
The information 13 ′ and 14 ′ recorded in the read layer 201
Is no longer read because it is masked by the in-plane magnetization of. Therefore, in the present embodiment, it is not necessary to apply the external magnetic field Hex during reproduction, which is used in Reference Example 1 and always keeps the magnetization directions of the read layers corresponding to the regions 44 in the same direction.

As described above, the portion where the temperature becomes the highest on the magneto-optical disk during reproduction is located at a position deviated rearward from the center of the laser beam 8. For this reason,
In the irradiation region 22 of the laser beam 8, the readout layer 20 is provided.
The temperature T _{1 at which} the temperature of ₁ changes from in-plane magnetization to perpendicular magnetization
Only a part of the above-described region 33 and a part of the region 44 in which the intermediate layer 3 is at the Curie temperature T ₃ or higher are present. Therefore, even if the information 14 exists in the area 33, it does not exist in the irradiation area 22 of the laser beam 8.
14 'is not regenerated.

In the read layer 201, the in-plane magnetization state is maintained in the region other than the region 33, and the magneto-optical effect is not exhibited with respect to the vertically incident light. Therefore, even if it exists in the irradiation area 22 of the laser beam 8, the information 12 ... Outside the area 33 is not reproduced.

From the above, the information reproduced by irradiation of the laser beam 8 exists in the irradiation region 22 of the laser beam 8 and the temperature T at which the temperature of the readout layer 201 shifts from in-plane magnetization to perpendicular magnetization. present in the region 33 becomes ₁ or more, and, the intermediate layer 3 is only information 13 existing outside the area 44 of the Curie temperature T ₃ or more. This allows
The magneto-optical disk of the present embodiment reproduces each recording bit separately, even if the recording bits are smaller than those of the magneto-optical recording medium previously proposed by the present inventors (see Japanese Patent Application No. 4-74605). The recording density can be remarkably improved.

Then, when the laser beam 8 moves to reproduce the next recorded bit, the temperature of the previous reproducing portion decreases and the read layer 201 shifts from the perpendicular magnetization to the in-plane magnetization. Along with this, the region where the temperature is lowered does not exhibit the magneto-optical Kerr effect. Therefore, the information is not reproduced from the portion where the temperature is lowered, and the signal from the adjacent bit, which is a cause of noise, is not mixed.

Now, this embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
A polycarbonate disk substrate 4 having pregrooves and prepits was placed in the sputtering apparatus used in Reference Example 1 containing o, Fe, and Co so as to face the target. With this sputtering device, the transparent dielectric film 5 having a film thickness of 60 n was formed in the same manner as in Reference Example 1.
m of AlN, and the reading layer 201 of G having a thickness of 50 nm
_{d 0.28 (Fe 0.8 Co 0 .2} ) 0.72, film thickness as the intermediate layer 35
0 nm Dy _0.21 Fe _0.79 , film thickness 50 n as recording layer 2
m of Dy _0.23 (Fe _0.82 Co _0.18 ) _0.77 and a transparent dielectric film 6 of AlN having a film thickness of 50 nm were sequentially formed.

The readout layer 201 made of Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 is in-plane magnetized at room temperature and shifts to the perpendicular magnetized state at a temperature of 60 ° C. or higher (T ₁ = 6).
0 ° C.) and the Curie temperature was 350 ° C. The intermediate layer 3 made of Dy _0.21 Fe _0.79 was a perpendicular magnetic film having a Curie temperature T ₃ of 90 ° C. The recording layer 2 made of Dy _0.23 (Fe _0.82 Co _0.18 ) _0.77 was a perpendicular magnetization film having a compensation point at about room temperature, and its Curie temperature T ₂ was 160 ° C.

After that, an ultraviolet curable resin was applied onto the transparent dielectric film 6 by spin coating and then irradiated with ultraviolet rays to form an overcoat film 7 on the transparent dielectric film 6. A thermosetting resin may be used as the overcoat film 7.

The magneto-optical disk manufactured as described above is irradiated with the laser beam 8 focused by the objective lens 9 so that the relative linear velocity of the laser beam 8 with respect to the magneto-optical disk becomes 10 m / s. The disc was rotated. Then, while continuously irradiating the laser beam 8 of 10 mW for recording, a modulating magnetic field of ± 15 kA / m was modulated at a frequency of 10 MHz and applied to the magneto-optical disk. Inversion magnetic domains with a length of 0.5 μm could be formed.

Thereafter, the power of the laser beam 8 is set to 2 mW.
When the recorded information was reproduced as described above, a reproduced signal having a frequency of 10 MHz could be obtained from the read layer 201 according to the inverted magnetic domain formed in the recording layer 2. In the present example, the constant magnetic field (external magnetic field Hex) that was necessary during reproduction in Reference Example 1 was not required.

When a 10 mW laser beam 8 for recording was continuously irradiated, a modulating magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk. 0.25 in 5 μm cycle
It was possible to form inverted magnetic domains with a length of μm.

Thereafter, the power of the laser beam 8 is set to 2 mW.
When the recorded information was reproduced as described above, a reproduced signal having a frequency of 20 MHz could be obtained from the read layer 201 according to the inverted magnetic domain formed in the recording layer 2.

Reference Example 2 Another reference example of the present invention will be described below with reference to FIGS. 3, 7 and 8.

The magneto-optical disk as the magneto-optical recording medium of the present reference example is the same as the magneto-optical disk of the above reference example 1 except that the intermediate layer 303 is used instead of the intermediate layer 3 of the above reference example 1. Each of the layers other than the intermediate layer 303, that is, the substrate, the transparent dielectric film, the readout layer, the recording layer, the transparent dielectric film, and the overcoat film, has the same configuration and various characteristics as in Reference Example 1. Therefore, the same reference numerals as those in Reference Example 1 are attached to each of these layers, and detailed description thereof is omitted here (see FIG. 7).

The intermediate layer 303 exhibits a perpendicular magnetization state at room temperature and an in-plane magnetization state at a temperature T ₃ (see FIG. 8). For example, the thickness of Dy _0.13 (Fe _0.5
May be used Co _{0 .5) 0.87} like. Temperature T at which the intermediate layer 303 transitions from perpendicular magnetization to in-plane magnetization
₃ is preferably 60 ° C to 90 ° C.

The temperature T _{1 at which} the read layer 1 changes from in-plane magnetization to perpendicular magnetization is preferably 40 ° C to 70 ° C.
The Curie temperature T ₂ of the recording layer 2 is 120 ° C.-18.
0 ° C is preferred. Then, each temperature T ₁ · T ₂ · T
₃ has a relationship of T ₁ <T ₃ <T ₂ .

In the above structure, recording on the magneto-optical disk is performed by applying a recording magnetic field to the magneto-optical disk and condensing the laser beam 8 of high power by the objective lens 9 to irradiate the magneto-optical disk. This is done by raising the temperature of layer 2 to near the Curie temperature T ₂ . As a result, recording bits are formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
Incidentally, FIG. 10A is a view of the magneto-optical disk as seen from the irradiation side of the laser beam 8, and FIG. 8B is a view taken along the line AA of the magneto-optical disk of FIG. Magnetic layer 1.2
-It shows the magnetization state of 303.

First, the laser beam 8 having a power lower than that at the time of recording is applied to the magneto-optical disk. At this time, the laser beam 8 is moving in the direction indicated by the arrow Q relative to the magneto-optical disk, and the temperature of the readout layer 1 is raised to the temperature T ₁ or higher by irradiation of the laser beam 8 (region 33 (region The center) of the laser beam 8 exists at a position displaced rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. Further, the region 44 (center of the region) where the temperature of the intermediate layer 303 rises to the temperature T ₃ or higher is present at a position deviated rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. .

Here, in the intermediate layer 303, in the region 44 having a temperature of T ₃ or higher, the perpendicular magnetization state is changed to the in-plane magnetization state. On the other hand, the region 4 in the intermediate layer 303
In the regions other than 4, the perpendicular magnetization state is held, and the magnetization direction of the recording layer 2 is transferred to the intermediate layer 303 by the exchange coupling force acting between the two layers of the recording layer 2 and the intermediate layer 303.

Further, the read layer 1 exhibits a perpendicular magnetization state in the region 33 where the temperature rises to the temperature T ₁ or higher, while it exhibits an in-plane magnetization state in the regions other than the region 33. In this case, in the region of the read layer 1 that is inside the region 33 and outside the region 44, the magnetization direction of the intermediate layer 303 is read by the exchange coupling force acting between the two layers of the intermediate layer 303 and the read layer 1. Transferred to layer 1. That is, the magnetization information of the recording layer 2 is transferred to the reading layer 1 via the magnetization of the intermediate layer 303, and the magnetization direction of the reading layer 1 inside the region 33 and outside the region 44 is the recording layer 2. The same direction as the magnetization direction of.

As described above, since the magnetization information of the recording layer 2 causes the exchange coupling force to act on the read layer 1 via the magnetization of the intermediate layer 303, the intermediate layer 303 is in-plane in the region 44 during reproduction. In the magnetized state, the exchange coupling force that the magnetization information of the recording layer 2 exerts on the read layer 1 becomes significantly smaller than that in the case where the intermediate layer 303 is in the perpendicular magnetized state outside the region 44. As described above, in the region 44 where the exchange coupling force acting between the recording layer 2 and the read layer 1 is extremely weakened, the magnetization state of the read layer 1 is the characteristic of the read layer 1, that is, the perpendicular magnetic anisotropy. It depends on the size of sex.

Since the read layer 1 of this reference example has a relatively large perpendicular magnetic anisotropy, the recording layer 2 via the intermediate layer 303 is used.
Even in the above-mentioned region 44 where the exchange coupling force from the is extremely weak, the perpendicular magnetization state is maintained and the magnetization direction of the recording layer 2 tends to be the same direction. However, since the exchange coupling force acting between the recording layer 2 and the read layer 1 is very weak, by applying an appropriate external magnetic field Hex to the read layer 1, it is inside the region 33 and outside the region 44. While the magnetization information transferred from the recording layer 2 is held in the reading layer 1 in the above, the magnetization direction of the portion corresponding to the region 44 in the reading layer 1 can be always aligned in the same direction. Therefore, by applying an appropriate external magnetic field Hex to the readout layer 1 during reproduction, the temperature T ₃
The information 13 'and 14' existing in the above area 44 is not reproduced.

As described above, the portion where the temperature becomes the highest on the magneto-optical disk at the time of reproduction exists at a position deviated rearward from the center of the laser beam 8. For this reason,
In the irradiation region 22 of the laser beam 8, there are a part of the region 33 having the temperature T ₁ or higher and a part of the region 44 having the temperature T ₃ or higher. Therefore, even if it exists in the region 33 where the temperature is equal to or higher than T ₁ , the information 14 and 14 ′ which does not exist in the irradiation region 22 of the laser beam 8 is not reproduced.

[0083] In the region other than the region 33 to a temperature above T ₁ in the readout layer 1, the in-plane magnetization state is maintained, it does not exhibit magneto-optical effect with respect to the vertical incident light. Therefore, even if the information 12 exists in the irradiation area 22 of the laser beam 8, the information 12 outside the area 33 where the temperature is equal to or higher than T ₁ ...
Is not played.

From the above, the information reproduced by the irradiation of the laser beam 8 exists in the irradiation region 22 of the laser beam 8 and the temperature T at which the temperature of the readout layer 1 shifts from the in-plane magnetization to the perpendicular magnetization. _A region 44 that exists in the region 33 where the temperature is ₁ or more and the intermediate layer 303 has a temperature T ₃ or higher.
It is only the information 13 existing outside. As a result, in the magneto-optical disk of the present reference example, even if the recording bits are smaller than those of the magneto-optical recording medium previously proposed by the inventors of the present application (see Japanese Patent Application No. 4-74605), each recording bit is separated. It is possible to reproduce the recorded data, and the recording density can be remarkably improved.

Then, when the laser beam 8 moves to reproduce the next recording bit, the temperature of the previous reproducing portion lowers and the read layer 1 shifts from the perpendicular magnetization to the in-plane magnetization.
Along with this, the region where the temperature is lowered does not exhibit the magneto-optical Kerr effect. Therefore, the information is not reproduced from the portion where the temperature is lowered, and the signal from the adjacent bit, which is a cause of noise, is not mixed.

Here, this reference example will be described more specifically.

As targets, Al, Gd, Dy, H
Sputtering used in Reference Example 1 containing o, Fe and Co
Pregrooves and prepits in the casting device
Target the disk substrate 4 made of polycarbonate
They were placed facing each other. With this sputtering device,
In the same manner as in Consideration 1, the transparent dielectric film 5 has a film thickness of 60 n.
m AlN, Dy with a film thickness of 50 nm as the readout layer 1
_0.35(Fe_0.5Co_0.5) _0.65, The thickness of the intermediate layer 303
50 nm Dy_0.13(Fe_0.5Co_0.5)_0.87, Recording layer 2
With a film thickness of 50 nm_0.23(Fe_0.82Co_0.18)
_0.77, AlN with a thickness of 50 nm is used as the transparent dielectric film 6 in this order.
Formed next.

The readout layer 1 made of Dy _0.35 (Fe _0.5 Co _0.5 ) _0.65 has an in-plane magnetization state at room temperature.
Transition to perpendicular magnetization state at temperatures above 0 ° C (T ₁ = 60 ° C)
The Curie temperature was 320 ° C. The intermediate layer 30 made of Dy _0.13 (Fe _0.5 Co _0.5 ) _{0.87 is also used.}
No. 3 exhibited a perpendicular magnetization state at room temperature, transitioned to an in-plane magnetization state at a temperature of 90 ° C. or higher (T ₃ = 90 ° C.), and its Curie temperature was 380 ° C. In addition, the above Dy _0.23 (Fe
_The recording layer 2 made of _0.82 Co _0.18 ) _0.77 is a perpendicular magnetization film having a compensation point at about room temperature, and its Curie temperature T ₂
Was 160 ° C.

After that, an ultraviolet curable resin was applied onto the transparent dielectric film 6 by spin coating and then irradiated with ultraviolet rays to form an overcoat film 7 on the transparent dielectric film 6. A thermosetting resin may be used as the overcoat film 7.

The magneto-optical disk manufactured as described above is irradiated with the laser beam 8 condensed by the objective lens 9 so that the relative linear velocity of the laser beam 8 with respect to the magneto-optical disk becomes 10 m / s. The disc was rotated. Then, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk in a state where the laser beam 8 of 10 mW for recording was continuously irradiated. It was possible to form a reversed magnetic domain having a length of 0.25 μm.

After that, the power of the laser beam 8 is set to 2 mW.
Then, when the recorded information was reproduced with a constant magnetic field (external magnetic field Hex) of +5 kA / m being applied to the magneto-optical disk, a reproduced signal of a frequency of 20 MHz was generated according to the reversed magnetic domain formed in the recording layer 2. Could be obtained from the readout layer 1.

[Embodiment 2] Another embodiment of the present invention will be described below with reference to FIGS. 4 and 7.

The magneto-optical disk as the magneto-optical recording medium of this embodiment is the same as the reference example 2 except that the read layer 401 is used instead of the read layer 1 of the reference example 2.
The magneto-optical disk has the same structure as that of the magneto-optical disk, and each layer other than the read layer, that is, the substrate, the transparent dielectric film, the intermediate layer, the recording layer, the transparent dielectric film, and the overcoat film have the same structure and various characteristics. Since these layers are the same as those in Reference Example 2, the same reference numerals as those in Reference Example 2 are given to these layers, and detailed description thereof is omitted here (see FIG. 7). In addition, the read layer 401 of this embodiment is the read layer 20 shown in the first embodiment.
1 has the same configuration and various characteristics as those of No. 1 and detailed description thereof will be omitted here.

The temperature T _{1 at which} the read layer 401 changes from in-plane magnetization to perpendicular magnetization is preferably 40 ° C to 70 ° C. The temperature T ₃ of the intermediate layer 303 transitions to the plane magnetization from perpendicular magnetization is preferably 60 ° C. to 90 ° C.. Also,
Curie temperature T ₂ of the recording layer 2 is preferably 120 ° C. to 180 ° C.. The temperatures T ₁ , T _2, and T ₃ are T ₁ <
The relationship is T ₃ <T ₂ .

In the above structure, recording on the magneto-optical disk is performed by applying a recording magnetic field to the magneto-optical disk and condensing the laser beam 8 of high power by the objective lens 9 to irradiate the magneto-optical disk. This is done by raising the temperature of layer 2 to near the Curie temperature T ₂ . As a result, recording bits are formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
Incidentally, FIG. 10A is a view of the magneto-optical disk as seen from the irradiation side of the laser beam 8, and FIG. 8B is a view taken along the line AA of the magneto-optical disk of FIG. Magnetic layer 401
-It shows the magnetization state of 2.303.

First, the magneto-optical disk is irradiated with the laser beam 8 having a power lower than that at the time of recording. At this time, the laser beam 8 is moving in the direction indicated by the arrow Q relative to the magneto-optical disk, and the temperature of the readout layer 1 is raised to the temperature T ₁ or higher by irradiation of the laser beam 8 (region 33 (region The center) of the laser beam 8 exists at a position displaced rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. Further, the region 44 (center of the region) where the temperature of the intermediate layer 303 rises to the temperature T ₃ or higher is present at a position deviated rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. .

In this case, as in Reference Example 1, the above intermediate layer 3 was used.
In No. 03, the magnetization direction of the recording layer 2 is transferred to the intermediate layer 303 by the exchange coupling force acting between the two layers of the recording layer 2 and the intermediate layer 303 in the region other than the above-mentioned region 44 showing the perpendicular magnetization state. .

Also in the read layer 401,
As in the second reference example, in the region inside the region 33 and outside the region 44, the magnetization information of the recording layer 2 is transferred to the readout layer 401 via the magnetization of the intermediate layer 303,
The magnetization direction is the same as the magnetization direction of the recording layer 2.

Here, the readout layer 401 of this embodiment is
Since the perpendicular magnetic anisotropy is relatively small, the exchange coupling force from the intermediate layer 3 is very weak in the above-mentioned region 44, which is in-plane magnetized and exhibits a magneto-optical effect with respect to vertically incident light. Disappear. Therefore, the information 13 ', 14' recorded in the recording layer 2 corresponding to the area 44 is masked by the in-plane magnetization of the read layer 401 and is not read. Therefore, in this embodiment, during reproduction,
The external magnetic field Hex for constantly aligning the magnetization directions of the read layers corresponding to the regions 44, which is required in the reference example 2, is not necessary.

As described above, the portion where the temperature becomes the highest on the magneto-optical disk at the time of reproduction exists at a position deviated rearward from the center of the laser beam 8. For this reason,
In the irradiation region 22 of the laser beam 8, the read layer 40 is formed.
The temperature T _{1 at which} the temperature of ₁ changes from in-plane magnetization to perpendicular magnetization
Only a part of the above-described region 33 and a part of the region 44 in which the intermediate layer 3 is at the Curie temperature T ₃ or higher are present. Therefore, even if the information 14 exists in the area 33, it does not exist in the irradiation area 22 of the laser beam 8.
14 'is not regenerated.

From the above, the information reproduced by the irradiation of the laser beam 8 exists in the irradiation region 22 of the laser beam 8 and the temperature T at which the temperature of the read layer 401 shifts from the in-plane magnetization to the perpendicular magnetization. present in the region 33 becomes ₁ or more, and, the intermediate layer 3 is only information 13 existing outside the area 44 of the Curie temperature T ₃ or more. This allows
The magneto-optical disk of the present embodiment reproduces each recording bit separately, even if the recording bits are smaller than those of the magneto-optical recording medium previously proposed by the present inventors (see Japanese Patent Application No. 4-74605). The recording density can be remarkably improved.

Then, when the laser beam 8 moves to reproduce the next recording bit, the temperature of the previous reproducing portion lowers and the read layer 401 shifts from the perpendicular magnetization to the in-plane magnetization. Along with this, the region where the temperature is lowered does not exhibit the magneto-optical Kerr effect. Therefore, the information is not reproduced from the portion where the temperature is lowered, and the signal from the adjacent bit, which is a cause of noise, is not mixed.

Now, this embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
A disk substrate 4 made of Paris carbonate having a pre-groove and a pre-pit was placed in opposition to the target in the sputtering apparatus used in Reference Example 1 provided with o, Fe and Co. With this sputtering device, the transparent dielectric film 5 having a film thickness of 60 n was formed in the same manner as in Reference Example 1.
m of AlN, and G of 50 nm in thickness as the readout layer 401.
_{d 0.28 (Fe 0.8 Co 0 .2} ) 0.72, Dy 0.13 (Fe 0.5 Co 0.5) of thickness 50nm as the intermediate layer 303 _0.87, Dy _0.23 film thickness 50nm as the recording layer 2 (Fe _0.82 Co _0.18)
0.77 , AlN having a film thickness of 50 nm was sequentially formed as the transparent dielectric film 6.

The read layer 401 made of Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 is in-plane magnetized at room temperature and shifts to the perpendicular magnetized state at a temperature of 60 ° C. or higher (T ₁ = 6).
0 ° C.) and the Curie temperature was 350 ° C. Further, the intermediate layer 303 made of Dy _0.13 (Fe _0.5 Co _0.5 ) _0.87 described above exhibits a perpendicular magnetization state at room temperature and shifts to an in-plane magnetization state at a temperature of 90 ° C. or higher (T ₃ = 90 ° C.), The Curie temperature was 380 ° C. Also, the above Dy
_The recording layer 2 made of _0.23 (Fe _0.82 Co _0.18 ) _0.77 was a perpendicular magnetization film having a compensation point at about room temperature, and its Curie temperature T ₂ was 160 ° C.

After that, an ultraviolet curable resin was applied onto the transparent dielectric film 6 by spin coating and then irradiated with ultraviolet rays to form an overcoat film 7 on the transparent dielectric film 6. A thermosetting resin may be used as the overcoat film 7.

The laser beam 8 is condensed and irradiated by the objective lens 9 onto the magneto-optical disk manufactured as described above, and the relative linear velocity of the laser beam 8 with respect to the magneto-optical disk is 10 m / s. The disc was rotated. Then, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk in a state where the laser beam 8 of 10 mW for recording was continuously irradiated. It was possible to form a reversed magnetic domain having a length of 0.25 μm.

Thereafter, the power of the laser beam 8 is set to 2 mW.
When the recorded information was reproduced as described above, a reproduced signal having a frequency of 20 MHz could be obtained from the read layer 401 according to the inverted magnetic domain formed in the recording layer 2. In the present example, the constant magnetic field (external magnetic field Hex) that was necessary during reproduction in Reference Example 2 was not required.

Reference Example 3 Regarding one reference example of the present invention,
The following is a description with reference to FIGS. 5, 7, and 8.

The magneto-optical disk as the magneto-optical recording medium of the present reference example is the same as the magneto-optical disk of the above reference example 1 except that the intermediate layer 503 is used instead of the intermediate layer 3 of the above reference example 1. Each of the layers other than the intermediate layer 503, that is, the substrate, the transparent dielectric film, the readout layer, the recording layer, the transparent dielectric film, and the overcoat film, has the same configuration and various characteristics as those of Reference Example 1. Therefore, the same reference numerals as those in Reference Example 1 are attached to each of these layers, and detailed description thereof is omitted here (see FIG. 7).

The intermediate layer 503 is an in-plane magnetized film that exhibits an in-plane magnetized state at room temperature and maintains the in-plane magnetized state from room temperature to the Curie temperature T ₃ (see FIG. 8). For example, the film thickness is 50 nmDy _0.09. Fe _0.91 or the like can be used. The Curie temperature T ₃ of the intermediate layer 503 is 6
0 ° C to 90 ° C is preferable.

The temperature T _{1 at which} the read layer 1 shifts from in-plane magnetization to perpendicular magnetization is preferably 40 ° C to 70 ° C.
The Curie temperature T ₂ of the recording layer 2 is 120 ° C.-18.
0 ° C is preferred. Then, each temperature T ₁ · T ₂ · T
₃ has a relationship of T ₁ <T ₃ <T ₂ .

In the above structure, recording on the magneto-optical disk is performed by applying a recording magnetic field to the magneto-optical disk and condensing the high power laser beam 8 by the objective lens 9 to irradiate the magneto-optical disk. This is done by raising the temperature of layer 2 to near the Curie temperature T ₂ . As a result, recording bits are formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
Incidentally, FIG. 10A is a view of the magneto-optical disk as seen from the irradiation side of the laser beam 8, and FIG. 8B is a view taken along the line AA of the magneto-optical disk of FIG. Magnetic layer 1.2
-The magnetization state of 503 is shown.

First, the magneto-optical disk is irradiated with the laser beam 8 having a power lower than that at the time of recording. At this time, the laser beam 8 is moving relative to the magneto-optical disk in the direction indicated by the arrow Q, and the portion of the magneto-optical disk where the temperature is highest is deviated rearward from the center of the laser beam 8. Will be in position. Therefore, the temperature of the readout layer 1 is changed to the temperature T by the irradiation of the laser beam 8.
_The region 33 (center of the region) that rises to ₁ or more is present at a position displaced rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. In addition, the region 44 (center of the region) where the temperature of the intermediate layer 503 rises to the Curie temperature T ₃ or higher exists at a position displaced rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. Become.

Here, in the intermediate layer 503, the magnetization disappears in the region 44 where the temperature is the Curie temperature T ₃ or higher, while in the regions other than the region 44,
The in-plane magnetization state is maintained. Further, in the read layer 1, the region 33 where the temperature rises to the temperature T ₁ or higher is in the perpendicular magnetization state, while the region other than the region 33 holds the in-plane magnetization state. Therefore, the read layer 1 is exchanged from the recording layer 2 through the in-plane magnetization of the intermediate layer 503 in the region 33 having the temperature T ₁ or higher and the region outside the region 44 having the temperature T ₃ or higher. Upon receiving the binding force, the recording layer 2 is oriented in the same direction as the magnetization direction.

As described above, the magnetization information of the recording layer 2 is transferred to the readout layer 1 via the in-plane magnetization of the intermediate layer 503, so that the intermediate layer 503 has no magnetization. In the region 44, the magnetization information of the recording layer 2 is not transferred to the reading layer 1. That is, in the region 44 where the magnetization does not exist in the intermediate layer 503, the magnetization information of the recording layer 2 is
The exchange coupling force cannot be applied to the readout layer 1. Therefore, the region 44 in the readout layer 1
The portion corresponding to is in a free state in which it is not subjected to the exchange coupling force from the intermediate layer 503, and its magnetization state depends on the characteristics of the read layer 1, that is, the magnitude of perpendicular magnetic anisotropy.

Since the read layer 1 of the present reference example has a relatively large perpendicular magnetic anisotropy, it maintains the perpendicular magnetization state even in the region 44 where the exchange coupling force from the intermediate layer 503 does not exist. Therefore, in this reference example, an external magnetic field Hex for always aligning the magnetization directions of the read layer 1 corresponding to the region 44 in the same direction during reproduction is applied to the magneto-optical disk. Thus, information 13 ', 14' present in the region 44 to a temperature T ₃ or more is not being played.

As described above, the portion where the temperature becomes the highest on the magneto-optical disk during reproduction is located at a position deviated rearward from the center of the laser beam 8. For this reason,
In the irradiation region 22 of the laser beam 8, a part of the region 33 in which the temperature of the readout layer 1 becomes equal to or higher than the temperature T _{1 at} which the in-plane magnetization changes to the perpendicular magnetization, and the intermediate layer 503 has the Curie temperature T ₃ or higher. There will be a part of the area 44 that becomes Therefore, even if it exists in the area 33 where the temperature is equal to or higher than T ₁ , the information 14, 14 ′ that does not exist in the irradiation area 22 of the laser beam 8 is not reproduced.

Further, the region 33 in the readout layer 1
In the other regions, the in-plane magnetization state is maintained and the magneto-optical effect is not shown for the vertically incident light. Therefore, even if it exists in the irradiation region 22 of the laser beam 8, the information 12 ... Outside the region 33 where the temperature is equal to or higher than T ₁ is not reproduced.

From the above, the information reproduced by the irradiation of the laser beam 8 exists in the irradiation region 22 of the laser beam 8 and the temperature T at which the temperature of the read layer 1 shifts from the in-plane magnetization to the perpendicular magnetization. present in the region 33 becomes ₁ or more, and, the intermediate layer 503 is only information 13 existing outside the area 44 of the Curie temperature T ₃ or more. As a result, in the magneto-optical disk of the present reference example, even if the recording bits are smaller than those of the magneto-optical recording medium previously proposed by the inventors of the present application (see Japanese Patent Application No. 4-74605), each recording bit is separated. It is possible to reproduce the recorded data, and the recording density can be remarkably improved.

Then, when the laser beam 8 moves to reproduce the next recording bit, the temperature of the previous reproducing portion lowers and the read layer 1 shifts from perpendicular magnetization to in-plane magnetization.
Along with this, the region where the temperature is lowered does not exhibit the magneto-optical Kerr effect. Therefore, the information is not reproduced from the portion where the temperature is lowered, and the signal from the adjacent bit, which is a cause of noise, is not mixed.

Here, this reference example will be described more specifically.

As targets, Al, Gd, Dy, H
Sputtering used in Reference Example 1 containing o, Fe and Co
Pregrooves and prepits in the casting device
Targeting the disc substrate 4 made of Paris carbonate
They were placed facing each other. With this sputtering device,
In the same manner as in Consideration 1, the transparent dielectric film 5 has a film thickness of 60 n.
m AlN, Dy with a film thickness of 50 nm as the readout layer 1
_0.35(Fe_0.5Co_0.5) _0.65, The film thickness as the intermediate layer 503
50 nm Dy_0.09Fe_0.91, The recording layer 2 has a film thickness of 50
nm Dy_0.23(Fe_0.82Co_0.18)_0.77, Transparent dielectric
As the film 6, AlN having a film thickness of 50 nm was sequentially formed.

The read layer 1 made of Dy _0.35 (Fe _0.5 Co _0.5 ) _0.65 has an in-plane magnetized state at room temperature.
Transition to perpendicular magnetization state at temperatures above 0 ° C (T ₁ = 60 ° C)
The Curie temperature was 320 ° C. The intermediate layer 503 made of Dy _0.09 Fe _0.91 described above exhibited an in-plane magnetization state at room temperature, and its Curie temperature T ₃ was 90 ° C. The recording layer 2 made of Dy _0.23 (Fe _0.82 Co _0.18 ) _0.77 was a perpendicular magnetization film having a compensation point at about room temperature, and its Curie temperature T ₂ was 160 ° C.

After that, an ultraviolet curable resin was applied onto the transparent dielectric film 6 by spin coating and then irradiated with ultraviolet rays to form an overcoat film 7 on the transparent dielectric film 6. A thermosetting resin may be used as the overcoat film 7.

The laser beam 8 is focused and irradiated by the objective lens 9 on the magneto-optical disk manufactured as described above, and the relative linear velocity of the laser beam 8 with respect to the magneto-optical disk is 10 m / s. The disc was rotated. Then, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk in a state where the laser beam 8 of 10 mW for recording was continuously irradiated. It was possible to form a reversed magnetic domain having a length of 0.25 μm.

Thereafter, the power of the laser beam 8 is set to 2 mW.
Then, when the recorded information was reproduced with a constant magnetic field (external magnetic field Hex) of +5 kA / m being applied to the magneto-optical disk, a reproduced signal of a frequency of 20 MHz was generated according to the reversed magnetic domain formed in the recording layer 2. Could be obtained from the readout layer 1.

[Embodiment 3] Another embodiment of the present invention will be described below with reference to FIGS. 6 and 7.

The magneto-optical disk as the magneto-optical recording medium of the present embodiment is the same as the reference example 3 except that the read layer 601 is used instead of the read layer 1 of the reference example 3.
The magneto-optical disk has the same structure as that of the magneto-optical disk, and each layer other than the read layer, that is, the substrate, the transparent dielectric film, the intermediate layer, the recording layer, the transparent dielectric film, and the overcoat film have the same structure and various characteristics. Since it is the same as the reference example 3, these layers are denoted by the same reference numerals as the reference example 3 and detailed description thereof is omitted here (see FIG. 7). In addition, the read layer 601 of this embodiment is the read layer 20 shown in the first embodiment.
1 has the same configuration and various characteristics as those of No. 1 and detailed description thereof will be omitted here.

The temperature T _{1 at which} the read layer 601 changes from in-plane magnetization to perpendicular magnetization is preferably 40 ° C to 70 ° C. The Curie temperature T ₃ of the intermediate layer 503 is 60 ° C.
90 degreeC is preferable. Also, the Curie temperature T of the recording layer 2
₂ is preferably 120 ° C to 180 ° C. The temperatures T ₁ , T _2, and T ₃ are in the relationship of T ₁ <T ₃ <T ₂ .

In the above structure, the recording on the magneto-optical disk is performed by applying the recording magnetic field to the magneto-optical disk and condensing the high power laser beam 8 by the objective lens 9 to irradiate the magneto-optical disk. This is done by raising the temperature of layer 2 to near the Curie temperature T ₂ . As a result, recording bits are formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
Incidentally, FIG. 10A is a view of the magneto-optical disk as seen from the irradiation side of the laser beam 8, and FIG. 8B is a view taken along the line AA of the magneto-optical disk of FIG. Magnetic layer 601
-It shows the magnetization state of 503.2.

First, the magneto-optical disk is irradiated with the laser beam 8 having a power lower than that at the time of recording. At this time, the laser beam 8 is moving relative to the magneto-optical disk in the direction indicated by the arrow Q, and the portion of the magneto-optical disk where the temperature is highest is deviated rearward from the center of the laser beam 8. Will be in position. Therefore, the temperature of the readout layer 1 is changed to the temperature T by the irradiation of the laser beam 8.
_The region 33 (center of the region) that rises to ₁ or more is present at a position displaced rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. In addition, the region 44 (center of the region) where the temperature of the intermediate layer 503 rises to the Curie temperature T ₃ or higher exists at a position displaced rearward with respect to the irradiation region 22 (center of the region) of the laser beam 8. Become.

In this case, in the same manner as in Reference Example 3, in the intermediate layer 503, the magnetization disappears in the region 44 having the Curie temperature T ₃ or higher, while in the regions other than the region 44. , The in-plane magnetization state is maintained. Further, in the read layer 601, the region 33 in which the temperature rises above the temperature T ₁ tends to exhibit the perpendicular magnetization state, while the region other than the region 33 retains the in-plane magnetization state. Become. Therefore, the temperature T
_{In the} region 33 of ₁ or more and the region of the region 44 of temperature T ₃ or more, the read layer 601 receives the exchange coupling force from the recording layer 2 via the in-plane magnetization of the intermediate layer 503, It will be oriented in the same direction as the magnetization direction of the recording layer 2.

In the second embodiment, when the intermediate layer 303 shows the in-plane magnetization state in the region 44, the read layer 401 having a relatively small perpendicular magnetic anisotropy shows the in-plane magnetization state. As described above, this is due to the decrease in magnetization of the intermediate layer 303 existing in the region 44 having the highest temperature due to the temperature increase, and in the region 44, the exchange coupling force acting between the read layer 401 and the intermediate layer 303 is exerted. Is extremely weak (see FIG. 4 above).

On the other hand, in the region 44 in which the magnetization does not exist in the intermediate layer 503, the magnetization information of the recording layer 2 cannot apply the exchange coupling force to the reading layer 1. Therefore, the portion of the read layer 1 corresponding to the region 44 is in a free state in which the exchange coupling force from the intermediate layer 503 is not received, and the magnetization state thereof is the characteristic of the read layer 601, that is, the perpendicular magnetic anisotropy. It depends on the size.

Here, the readout layer 601 of this embodiment is
Since the perpendicular magnetic anisotropy is relatively small, in the above-mentioned region 44 where the exchange coupling force from the intermediate layer 503 does not exist, the in-plane magnetization state occurs and the magneto-optical effect is not exhibited for the vertically incident light. Therefore, the information 13 ′ and 14 ′ recorded in the recording layer 2 corresponding to the area 44 is stored in the read layer 6
It is not masked by the in-plane magnetization of 01 and is not read. Therefore, in the present embodiment, the external magnetic field Hex for constantly aligning the magnetization directions of the read layers corresponding to the regions 44, which was necessary in the reference example 3, during reproduction.
No longer needed.

As described above, the part where the temperature becomes the highest on the magneto-optical disk during reproduction is located at a position deviated rearward from the center of the laser beam 8. For this reason,
In the irradiation region 22 of the laser beam 8, the readout layer 60 is provided.
The temperature T _{1 at which} the temperature of ₁ changes from in-plane magnetization to perpendicular magnetization
Only a part of the above-described region 33 and a part of the region 44 in which the intermediate layer 3 is at the Curie temperature T ₃ or higher are present. Therefore, even if the information 14 exists in the area 33, it does not exist in the irradiation area 22 of the laser beam 8.
14 'is not regenerated.

In the read layer 601, the in-plane magnetization state is maintained in the region other than the region 33, and the magneto-optical effect is not exhibited with respect to the vertically incident light. Therefore, even if it exists in the irradiation area 22 of the laser beam 8, the information 12 ... Outside the area 33 is not reproduced.

From the above, the information reproduced by the irradiation of the laser beam 8 exists in the irradiation region 22 of the laser beam 8, and the temperature T at which the temperature of the read layer 601 shifts from the in-plane magnetization to the perpendicular magnetization. present in the region 33 becomes ₁ or more, and, the intermediate layer 3 is only information 13 existing outside the area 44 of the Curie temperature T ₃ or more. This allows
The magneto-optical disk of the present embodiment reproduces each recording bit separately, even if the recording bits are smaller than those of the magneto-optical recording medium previously proposed by the present inventors (see Japanese Patent Application No. 4-74605). The recording density can be remarkably improved.

Then, when the laser beam 8 moves to reproduce the next recording bit, the temperature of the previous reproducing portion lowers and the read layer 601 shifts from the perpendicular magnetization to the in-plane magnetization. Along with this, the region where the temperature is lowered does not exhibit the magneto-optical Kerr effect. Therefore, the information is not reproduced from the portion where the temperature is lowered, and the signal from the adjacent bit, which is a cause of noise, is not mixed.

Now, this embodiment will be described more specifically.

As a target, Al, Gd, Dy, H
A disk substrate 4 made of Paris carbonate having a pre-groove and a pre-pit was placed in opposition to the target in the sputtering apparatus used in Reference Example 1 provided with o, Fe and Co. With this sputtering device, the transparent dielectric film 5 having a film thickness of 60 n was formed in the same manner as in Reference Example 1.
m of AlN, and G of 50 nm in thickness as the readout layer 601.
_{d 0.28 (Fe 0.8 Co 0 .2} ) 0.72, film thickness 50nm of Dy _0.09 Fe _0.91 as an intermediate layer 5033, the recording layer 2 as a film thickness 50nm of _{Dy 0.23 (Fe 0.82 Co 0.18)} 0.77, film as a transparent dielectric film 6 AlN having a thickness of 50 nm was sequentially formed.

The read layer 601 made of Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 is in-plane magnetized at room temperature, and shifts to perpendicular magnetized at temperatures of 60 ° C. or higher (T ₁ = 6).
0 ° C.) and the Curie temperature was 350 ° C. The intermediate layer 3 made of Dy _0.09 Fe _0.91 described above exhibits an in-plane magnetization state at room temperature, and its Curie temperature T ₃ is 90 ° C.
Met. In addition, the above-mentioned Dy _0.23 (Fe _0.82 Co _0.18 )
_The recording layer 2 made of _0.77 is a perpendicular magnetization film having a compensation point at about room temperature, and its Curie temperature T ₂ was 160 ° C.

After that, an ultraviolet curable resin was applied onto the transparent dielectric film 6 by spin coating and then irradiated with ultraviolet rays to form an overcoat film 7 on the transparent dielectric film 6. A thermosetting resin may be used as the overcoat film 7.

The laser beam 8 is condensed and irradiated by the objective lens 9 to the magneto-optical disk manufactured as described above, and the relative linear velocity of the laser beam 8 with respect to the magneto-optical disk is 10 m / s. The disc was rotated. Then, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk in a state where the laser beam 8 of 10 mW for recording was continuously irradiated. It was possible to form a reversed magnetic domain having a length of 0.25 μm.

Thereafter, the power of the laser beam 8 is set to 2 mW.
When the recorded information was reproduced as described above, a reproduced signal having a frequency of 20 MHz could be obtained from the readout layer 601 according to the inverted magnetic domain formed in the recording layer 2. In the present example, the constant magnetic field (external magnetic field Hex) that was required during reproduction in Reference Example 3 was not required.

Reference Example 4 Reference Example 4 will be described below with reference to FIGS. 9 to 13.

The magneto-optical disk as the magneto-optical recording medium of the present Reference Example 4 includes a substrate 701, a transparent dielectric film 702 and a first dielectric film 702.
Magnetic layer 703, third magnetic layer 704, second magnetic layer 705,
The transparent dielectric film 706 and the overcoat film 707 are laminated in this order, and each of the magnetic layers 703 to 70 is formed.
An exchange coupling force acts between the five.

The substrate 701, the transparent dielectric film 702,
The transparent dielectric film 706 and the overcoat film 707 are
Since the respective configurations and characteristics of the substrate 4, the transparent dielectric film 5, the transparent dielectric film 6 and the overcoat film 7 of Reference Example 1 are the same, detailed description thereof will be omitted here.

The first magnetic layer 703 is a perpendicular magnetization film which exhibits a perpendicular magnetization state at room temperature and maintains the perpendicular magnetization state up to the Curie temperature T ₇₁ . The first magnetic layer 703 has the functions of both a recording layer and a reproducing layer, and its Curie temperature T ₇₁ is set higher than the Curie temperature of the second magnetic layer 705. As the first magnetic layer 703,
For example, a rare earth transition metal such as GdDyFeCo can be used. Since the function of the reproducing layer is important for the first magnetic layer 703, it is desirable that the Curie temperature T ₇₁ is high and the Kerr rotation angle Θk is large. In this reference example, Gd _0.10 Dy _0.13 Fe _0.54 Co _0.23 having a film thickness of 50 nm is used as the first magnetic layer 703. The Curie temperature T ₇₁ of this Gd _0.10 Dy _0.13 Fe _0.54 Co _0.23 is as high as 300 ° C., and this Gd _0.10 D
The Kerr rotation angle Θk when y _0.13 Fe _0.54 Co _0.23 is irradiated with a laser beam having a wavelength of about 800 nm is relatively large at about 0.4. Therefore, Gd _0.10 Dy _0.13 Fe
_0.54 Co _0.23 is an excellent reproducing layer.

The first magnetic layer 703 is made of the above-mentioned GdDyF.
The present invention is not limited to eCo, and other than that, for example, GdTbFeCo, TbFeCo, DyFeCo,
It may be GdNbFe, NbTbFeCo, Pt / Co, Pd / Co, or the like. In particular, the first magnetic layer 703
As GdNbFe, NbTbFeCo, Pt / Co
Alternatively, when Pd / Co is used, larger reproduction performance can be obtained with reproduction light having a short wavelength. Therefore, by using a short wavelength laser beam to reduce the beam diameter, it is possible to achieve higher recording density. There is.

The second magnetic layer 705 is a perpendicular magnetization film that exhibits a perpendicular magnetization state at room temperature and maintains the perpendicular magnetization state from room temperature to the Curie temperature. The second magnetic layer 705 is
Since the function as a recording layer is required, the Curie temperature is set to the lowest among the three magnetic layers 703 to 705. As the second magnetic layer 705, for example,
Rare earth transition metals such as TbFeCo can be used. In this reference example, the second magnetic layer 705 has a film thickness of 10
0 nm Tb _0.20 Fe _0.75 Co _0.05 is used. The Curie temperature of Tb _0.20 Fe _0.75 Co _0.05 is relatively low at 150 ° C. and is excellent as a recording layer.

The second magnetic layer 705 is made of the above TbFeC.
It is not limited to o, and other than that, for example,
It may be DyFeCo, GdTbFe, TbFe, DyFe, or the like.

Here, in FIG. 11, Gd _0.10 Dy _0.13 Fe
_A first magnetic layer 703 made of _0.54 Co _0.23 and Tb _0.20 F
The temperature dependence of the coercive force with the second magnetic layer 705 made of e _0.75 Co _0.05 is shown.

In the case of this reference example, an external magnetic field is applied to the magneto-optical disk at the time of recording, but as shown in the figure, since the magnitude of this external magnetic field is set to 200 Oe, the second magnetic layer The temperature at which 705 causes magnetization reversal (hereinafter referred to as the second magnetic layer magnetization reversal temperature) T ₇₂ , that is, the second magnetic layer 7
The temperature at which the coercive force of 05 becomes smaller than the magnitude of the external magnetic field (200 Oe) corresponds to about 145 ° C.

The third magnetic layer 704 serves as an intermediate layer that mediates exchange coupling between the first magnetic layer 703 and the second magnetic layer 705, and exhibits an in-plane magnetization state at room temperature. It is set so as to exhibit a perpendicular magnetization state at a temperature higher than the above-mentioned second magnetic layer magnetization reversal temperature T ₇₂ . As the third magnetic layer 704, for example, a rare earth transition metal such as GdFeCo can be used. In this reference example, the third
As the magnetic layer 704, Gd _0.23 Fe _{0.46 with} a film thickness of 40 nm is used.
Co _0.31 is used. This Gd _0.23 Fe _0.46 Co _0.31
Indicates an in-plane magnetization state at room temperature, the temperature T _{73 at} which the magnetization shifts to perpendicular magnetization is about 170 ° C. (> T ₇₂ ≈145 ° C.), and the perpendicular magnetization state is maintained up to the Curie temperature of 300 ° C.

In this reference example, the transparent dielectric film 5 is made of AlN having a film thickness of 80 nm, and the transparent dielectric film 6 is made of a film thickness of 5 nm.
A 0 nm AlN film and an ultraviolet curable resin film are used as the overcoat film 7.

In the above structure, information is recorded on the magneto-optical disc by applying an external magnetic field of 200 Oe to the magneto-optical disc and condensing the laser beam 8 of high power by the objective lens 9. This is performed by irradiating the magnetic disk and raising the temperature of the second magnetic layer 705 to near the Curie temperature.

Here, in FIG. 10, the information bit 721 formed in the track and the irradiation of the laser beam 8 raise the temperature of the second magnetic layer magnetization reversal temperature T ₇₂ or higher, and the second magnetic layer 705 causes the magnetization reversal. The region (hereinafter, referred to as the second magnetic layer magnetization reversal region) 722 and the temperature T _{73 at which} the third magnetic layer 704 shifts from the in-plane magnetization to the perpendicular magnetization become equal to or higher than the third temperature.
The relative relationship between the magnetic layer 704 and a region exhibiting perpendicular magnetization (hereinafter, referred to as a third magnetic layer perpendicular magnetization region) 723 is shown.
Here, it is assumed that the information is already recorded in both tracks adjacent to the track on which the recording is actually performed, and the already recorded information is displayed as a black-filled bit pattern. . The magneto-optical disk is moving in the direction indicated by arrow R with respect to the laser beam 8.

Laser beam 8 in the presence of the external magnetic field
The irradiation causes the magnetization reversal of the second magnetic layer 705 in the second magnetic layer magnetization reversal region 722, and a recording bit is formed on the second magnetic layer 705.

Then, the recording bit formed on the second magnetic layer 705 is finally magnetically transferred and stored in the first magnetic layer 703 by exchange coupling via the third magnetic layer 704. . In this case, the second magnetic layer 705 is actually
The magnetic transfer between the first magnetic layer 703 and the
This means that the third magnetic layer 704 is limited only to the region exhibiting perpendicular magnetization. That is, when the third magnetic layer 704 is in the in-plane magnetization state, the exchange coupling force acting between the first magnetic layer 703 and the second magnetic layer 705 becomes very weak, and the magnetization state of the second magnetic layer 705 changes. It is not transferred to the first magnetic layer.

Here, the temperature T ₇₃ at which the third magnetic layer 704 shifts from in-plane magnetization to perpendicular magnetization is set higher than the second magnetic layer magnetization reversal temperature T ₇₂ , and the third magnetic layer perpendicular magnetization region is set. Since 723 is smaller than the second magnetic layer magnetization reversal region 722, as a result, recording bits relatively smaller than the recording bits formed in the second magnetic layer 705 are formed in the first magnetic layer 703. Will be.

By the way, as shown in the figure, the magnetization reversal region 722 of the second magnetic layer 705, which is a recording layer, is affected by the thermal diffusion in the lateral direction and the track direction at the time of recording. Even up to the bit recorded immediately before, the magnetization state of the recorded portion of the second magnetic layer 705 is disturbed.

However, the portion of the second magnetic layer 705 where the magnetization state is disturbed is the third magnetic layer 704.
Masked by the in-plane magnetization of the first magnetic layer 703.
Is not magnetically transferred to. That is, in the magneto-optical disk of this reference example, the influence of the thermal interference generated in the second magnetic layer 705 does not reach the first magnetic layer 703 for finally recording information. 1 magnetic layer 70
Almost no disturbance of the information already recorded in 3 occurs. Therefore, highly reliable and high-density bit information is recorded on the first magnetic layer 703 of the magneto-optical disk.

Next, information was recorded on the magneto-optical disk of the present reference example and the magneto-optical disk of the present reference example in which the third magnetic layer 704 was omitted, under the conditions shown in Table 1 below. FIG. 12 shows changes in C / N of the reproduced signal with respect to the track pitch when the information recorded on each magneto-optical disk is reproduced under the conditions shown in Table 1 below. In the figure, the solid line shows the case of using the magneto-optical disk of this reference example, and the dotted line shows the case of using the conventional magneto-optical disk without the third magnetic layer 704.

[0169]

[Table 1]

As is apparent from the figure, as the track pitch is narrowed to increase the density, the third magnetic layer 704 is formed.
In the case of a conventional type (exchange coupling double-layered film structure) magneto-optical disk that does not have the above, the C / N of the reproduced signal is significantly deteriorated due to the influence of crosstalk between adjacent tracks during recording. On the other hand, in the case of the magneto-optical disk having the exchange-coupling three-layer film structure of the present reference example, crosstalk between adjacent tracks during recording is suppressed, and even if the density becomes high, the deterioration of C / N of the reproduced signal is slight. Is.

Therefore, by using the magneto-optical disk of this reference example, the recording density can be improved without increasing the load on the device system side.

The first to third magnetic layers 703 of this reference example are also provided.
.About.705 are used only as the recording layer, and as shown in FIG.
The intermediate layer and the readout layer used in Nos. 3 to 3 can be stacked in this order to form an exchange coupling five-layer film structure. That is, since it is the first magnetic layer 703 that actually stores high-density information in the exchange-coupling three-layer film of this reference example, the first magnetic layer 703 is not used as a read layer and is used only as a recording layer. This first magnetic layer 703 is made to function, and
3, the recording layer 2 shown in Reference Examples 1 to 3 is used. The magneto-optical recording medium using such an exchange-coupling five-layer film has the effect that the resolution at the time of reproduction can be improved as shown in Examples 1 to 3 and Reference Examples 1 to 3, and at the same time the recording medium is adjacent to the recording medium. This also has the effect of avoiding the adverse effects of heat interference on the recording bits, and can realize high-density recording of information.

In each of the above embodiments and reference examples, the magneto-optical disk was described as the magneto-optical recording medium, but the present invention is not limited to this, and the magneto-optical tape,
It can also be applied to magneto-optical cards and the like.

The specific embodiments or examples made in the section of the detailed description of the invention are merely for clarifying the technical contents of the present invention, and are not limited to such specific examples. It should not be construed in a narrow sense, and various modifications can be made and implemented within the spirit of the present invention and the scope of the above claims.

[0175]

According to the magneto-optical recording medium of the present invention, a recording bit much smaller than the irradiation area of the light beam can be reproduced, so that the recording density can be remarkably improved.

Further, according to the reproducing method of the magneto-optical recording medium of the present invention, among the bits recorded in the recording layer, the recording bit reproduced by irradiation of the light beam exists in the irradiation region of the light beam. Moreover, since only the recording bits are present in the region where the temperature is not lower than T ₁ and lower than T ₃ , the recording density can be remarkably improved.

[Brief description of drawings]

FIG. 1 shows Reference Example 1 and is an explanatory diagram showing a magnetization state of each magnetic layer of a magneto-optical disk irradiated with a laser beam.

FIG. 2 shows Example 1 and is an explanatory diagram showing a magnetization state of each magnetic layer of a magneto-optical disk irradiated with a laser beam.

FIG. 3 shows Reference Example 2 and is an explanatory diagram showing a magnetization state of each magnetic layer of a magneto-optical disk irradiated with a laser beam.

FIG. 4 shows Example 2 and is an explanatory diagram showing a magnetization state of each magnetic layer of a magneto-optical disk irradiated with a laser beam.

FIG. 5 shows Reference Example 3 and is an explanatory diagram showing a magnetization state of each magnetic layer of a magneto-optical disk irradiated with a laser beam.

FIG. 6 shows Example 3 and is an explanatory diagram showing a magnetization state of each magnetic layer of a magneto-optical disk irradiated with a laser beam.

FIG. 7 is an explanatory diagram showing a configuration of the magneto-optical disk shown in FIGS. 1 to 6.

8 is an explanatory diagram showing the temperature dependence of the coercive force of each magnetic layer of the magneto-optical disk of FIGS.

FIG. 9 is a diagram illustrating a fourth reference example and is an explanatory diagram illustrating a configuration of a magneto-optical disk.

FIG. 10 shows a relative relationship between an information bit pattern formed on the magneto-optical disk, a region in which the second magnetic layer causes magnetization reversal due to laser beam irradiation, and a region in which the third magnetic layer exhibits perpendicular magnetization. FIG.

FIG. 11 is a first magnetic layer and a second magnetic layer of the magneto-optical disk.
It is explanatory drawing which shows the temperature dependence of the coercive force of a magnetic layer.

FIG. 12 is an explanatory diagram showing a change in C / N of a reproduction signal with respect to a track pitch of the magneto-optical disk and a magneto-optical disk in which only the third magnetic layer is omitted from the magneto-optical disk.

FIG. 13 is an explanatory diagram showing a configuration in which an intermediate layer and a read layer of the magneto-optical disc of FIGS. 1 to 6 are further laminated on the first to third magnetic layers of the magneto-optical disc.

FIG. 14 is an explanatory diagram showing a magnetization state of each magnetic layer when a magneto-optical recording medium of Japanese Patent Application No. 4-74605 is irradiated with a laser beam.

FIG. 15 is an explanatory diagram showing a magnetization state of each magnetic layer when a laser beam is applied to the magneto-optical recording medium on which high density recording is performed.

[Explanation of symbols]

1.201.401.601 Read-out layer 2 recording layers 3.303.503 Middle layer 4 substrates 5.6 Transparent dielectric film 8 Laser beam (light beam) 701 substrate 702/706 Transparent dielectric film 703 First magnetic layer 704 Third magnetic layer 705 Second magnetic layer

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Takahashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) Kenji Ota 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Sharp Corporation (56) Reference JP 5-205336 (JP, A) JP 5-84212 (JP, A) JP 5-12732 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 11/105

Claims (4)

(57) [Claims] 1. A perpendicular magnetization state is exhibited at room temperature,
To Curie temperature T ₂Recording that maintains the perpendicular magnetization state up to
Layers and It is arranged on the incident side of the light beam with respect to the recording layer and kept at room temperature.
Shows the in-plane magnetization state at the temperature T₁Vertical magnetism
The temperature T₃With the above, the in-plane magnetization state can be
The readout layer shown, It is provided between the read layer and the recording layer, and is stored at room temperature.
Shows a perpendicular magnetization state while the temperature T₃In-plane magnetization
Having an intermediate layer that transitions to the state₁, T ₂, T₃
But, T₁<T₃<T₂ The magneto-optical recording medium characterized by satisfying the relationship
body. 2. A perpendicular magnetization state at room temperature,
To Curie temperature T ₂Recording that maintains the perpendicular magnetization state up to
Layers and It is arranged on the incident side of the light beam with respect to the recording layer and kept at room temperature.
Shows the in-plane magnetization state at the temperature T₁Vertical magnetism
The temperature T₃With the above, the in-plane magnetization state can be
The readout layer shown, It is provided between the read layer and the recording layer, and is stored at room temperature.
Indicates a perpendicular magnetization state, from room temperature to Curie temperature T₃Until
It has an intermediate layer that holds the perpendicular magnetization state, Above temperature T₁, T₂, T₃But, T₁<T₃<T₂ The magneto-optical recording medium characterized by satisfying the relationship
body. 3. A perpendicular magnetization state at room temperature,
To Curie temperature T ₂Recording that maintains the perpendicular magnetization state up to
Layers and It is arranged on the incident side of the light beam with respect to the recording layer and kept at room temperature.
Shows the in-plane magnetization state at the temperature T₁Vertical magnetism
The temperature T₃With the above, the in-plane magnetization state can be
The readout layer shown, It is provided between the read layer and the recording layer, and is stored at room temperature.
Indicates the in-plane magnetization state, from room temperature to Curie temperature T₃Until
It has an intermediate layer that maintains the in-plane magnetization state, and has the temperature T₁,
T₂, T₃But, T₁<T₃<T₂ The magneto-optical recording medium characterized by satisfying the relationship
body. 4. The reproducing method for the magneto-optical recording medium according to claim 1, wherein the reproducing light beam is irradiated onto the magneto-optical recording medium,
A reproducing method for a magneto-optical recording medium, which comprises forming an area having a temperature of T ₁ or more and less than T ₃ and transferring the magnetization information of the recording layer to a reading layer in the area to reproduce.