JP3210916B2 - Reproduction method of magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for reproducing a magneto-optical recording medium such as a magneto-optical disk, a magneto-optical tape, a magneto-optical card, etc., applied to a magneto-optical recording apparatus.

[0002]

2. Description of the Related Art At present, 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 / reproduction is performed using a magnetic head has been advanced. Recently, research and development for further improving the recording density have become active.

[0003] The recording density of the magneto-optical recording medium is determined by the recording density.
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 exist in the light beam, and One recording bit cannot be separated and reproduced, resulting in deterioration of reproduction characteristics.

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

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

In performing the above method, a light having an exchange-coupling two-layer film comprising a readout 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 normal magneto-thermo-magnetic 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 to the readout layer in advance by the auxiliary magnetic field generator, and initialization is performed so that the magnetization direction of the readout layer is aligned with a predetermined direction. Next, the magneto-optical disk is irradiated with a reproducing beam to raise the local temperature and transfer the magnetization information of the recording layer to the reading layer. In this case, information can be reproduced only from the portion where the temperature of the central portion of the portion irradiated with the reproduction beam has increased. Therefore, it is possible to read even a recording bit smaller than the light beam.

However, when the above-described magneto-optical disk is used, an auxiliary magnetic field must be applied by an auxiliary magnetic field generator prior to a reproducing operation. Also, during playback,
The recording bit transferred from the recording layer to the readout layer remains as it is even when the temperature of the portion drops. For this reason, when the light beam is moved to reproduce the next recording bit, the previous recording bit is still present in the light beam, so that the remaining bits are also reproduced. This is 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 a reproducing operation, and can avoid signal contamination 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). The magneto-optical recording medium and a reproducing method using the medium will be described below with reference to FIG. FIG. 2A is a diagram of the magneto-optical recording medium viewed from the light beam irradiation side, and FIG. 2B is a diagram showing each of the magneto-optical recording media of FIG. This shows the magnetization state of the magnetic layers 51 and 52.

The magneto-optical recording medium has a recording layer 52 having a Curie temperature point of about 150 ° C. and a read layer 51 having an in-plane magnetization state at room temperature, but having a perpendicular magnetization state at a reading temperature of about 50 ° C. or higher. And In recording on the 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. It is performed by Thereby, recording bits are formed on the recording layer 52.

On the other hand, reproduction of information recorded on the magneto-optical recording medium is performed as follows. First, a light beam having a lower power than during recording is applied to the magneto-optical recording medium. At this time, the light beam is moving relative to the recording medium in the direction indicated by the arrow P, and the portion having the highest temperature on the magneto-optical recording medium is located at a position shifted backward 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 light beam irradiation and the data can be read is located behind the light beam irradiation region 72 (center of the region). Will be present at a position deviated from Then, in only the region 83, the readout layer 51 is in a perpendicular magnetization state, and receives the exchange coupling force from the recording layer 52, so that the magnetization direction of the readout layer 51 is the same as the magnetization direction of the recording layer 52. Here, since there is a shift between the light beam irradiation area 72 and the area 83 in which reading is possible due to the temperature rise in the readout layer 51, information to be actually reproduced is stored in the light beam irradiation area 72. , And only the information 63 existing in the readable area 83, and the other information is not reproduced.

As described above, only the high temperature region in the light beam irradiation region 72 acts as a kind of optical aperture, so that the effective light spot contributing to information reproduction is reduced, and the detection resolution is improved. As a result, even with recording bits smaller than the size of the light beam, each recording bit can be separated and reproduced. And
Since a portion of the readout layer 51 where the temperature does not rise or a portion where the temperature is lowered shows in-plane magnetization, the magneto-optical effect is not exhibited, and information recorded on the recording layer 52 is masked by the in-plane magnetization of the readout layer 51. It will not be read. As a result, it is possible to avoid mixing of signals from adjacent bits that cause noise. Further, an auxiliary magnetic field generator for initialization prior to the reproducing operation is not required.

[0012]

FIG. 15 shows a case where the recording density of the magneto-optical recording medium is further increased.
Let's think about it. FIG. 3A is a diagram of the magneto-optical recording medium viewed from the light beam irradiation side, and FIG.
5A shows the magnetization state of each of the magnetic layers 51 and 52 in the section taken along the line AA of the magneto-optical recording medium of FIG.

When the irradiation area 72 of the light beam in the readout layer 51 and the range 83 in which reading is possible due to the temperature rise due to the irradiation of the light beam are the same as those shown in FIG. There are two pieces of information (information 93 and 93 ') existing in the readable area 83 and in the readable area 83, and it becomes impossible to separate and reproduce each recording bit.

The present invention has been made in view of the above, and has as its object to provide the features of the magneto-optical recording medium previously proposed by the inventor of the present invention (such as being able to avoid signal mixing from the previous recording bit). The present invention provides a magneto-optical recording medium capable of improving the recording density, in which even if the recording density is further increased than that of the magneto-optical recording medium, each recording bit can be separated and reproduced. It is in.

[0015]

The present invention solves the above problems.
This was done to solve the problem
Indicates a perpendicular magnetization state, perpendicular from room temperature to Curie temperature T ₂
A recording layer for maintaining a magnetized state, and an optical beam
At the entrance side of the
To On the other hand, reading to migrate to a perpendicular magnetization state at a temperature above T ₁
A readout layer, provided between the readout layer and the recording layer,
While showing a perpendicular magnetization state at room temperature, at temperatures above T ₃
An intermediate layer that transitions to an in-plane magnetization state;
T ₁ , T ₂ , and T ₃ satisfy the relationship of T ₁ <T ₃ <T ₂
A method for reproducing a magneto-optical recording medium, comprising:
The irradiation area of the reproducing light beam in the body, T ₃ or T ₂ Not
A region where the temperature is full is formed, and
Blocking transfer of magnetization from the recording layer to the readout layer
It is characterized by.

According to the present invention, an external magnetic field is applied during reproduction.
And, I and the T ₃ or more temperature in the readout layer
The direction of magnetization in the region is the same direction according to the external magnetic field
It is characterized by being aligned with.

According to the present invention, an external magnetic field is applied during reproduction.
Without the I and the T ₃ or more temperature in the readout layer
Characterized in that the direction of magnetization in the region
You.

Further , the present invention relates to a method for producing a perpendicular magnetized state at room temperature.
Perpendicular magnetization from room temperature to Curie temperature T ₂
Recording layer and light beam incident on the recording layer
While showing an in-plane magnetization state at room temperature,
Readout layer to migrate to the perpendicular magnetization at a temperature above T ₁
Provided between the readout layer and the recording layer,
At room temperature to the Curie temperature T ₃
An intermediate layer that maintains a perpendicular magnetization state until the temperature T
Light in which ₁ , T ₂ and T ₃ satisfy the relationship of T ₁ <T ₃ <T ₂
A method for reproducing a magnetic recording medium, wherein the magneto-optical recording medium is
Within the irradiation area of the reproduction light beam at T ₃ or more and less than T ₂
Forming an area having a temperature of
When the transfer of magnetization from the layer to the readout layer is interrupted,
Without applying an external magnetic field to the readout layer.
The direction of magnetization in the region where the temperature is ₃ or more is directed in the in-plane direction
It is characterized by that.

Also, the present invention relates to a method for producing a perpendicular magnetization at room temperature.
Perpendicular magnetization from room temperature to Curie temperature T ₂
Recording layer and light beam incident on the recording layer
While showing an in-plane magnetization state at room temperature,
Readout layer to migrate to the perpendicular magnetization at a temperature above T ₁
Provided between the readout layer and the recording layer,
At room temperature to the Curie temperature T ₃
An intermediate layer that maintains an in-plane magnetization state until the temperature T
Light in which ₁ , T ₂ and T ₃ satisfy the relationship of T ₁ <T ₃ <T ₂
A method for reproducing a magnetic recording medium, wherein the magneto-optical recording medium is
Within the irradiation area of the reproduction light beam at T ₃ or more and less than T ₂
Forming an area having a temperature of
When the transfer of magnetization from the layer to the readout layer is interrupted,
Without applying an external magnetic field to the readout layer.
The direction of magnetization in the region where the temperature is ₃ or more is directed in the in-plane direction
It is characterized by that .

[0020]

The operation will be described below.

According to the above configuration, when the light beam is irradiated on the magneto-optical recording medium to be used, the temperature distribution of the irradiated portion becomes a Gaussian distribution. Area and the temperature T3
The region where the temperature is equal to or higher than the temperature T1 or higher is smaller.

Further, since the light beam moves relatively to the magneto-optical recording medium at a predetermined linear velocity, the portion of the medium where the temperature is highest is shifted backward from the center of the light beam. Will be in place. Therefore, the light beam irradiation area, a part of the temperatures T ₁ or more regions (and the temperature T ₃ or a portion of the region) is present, it is present in the region to a temperature above T ₁ On the other hand, recording bits that do not exist in the light beam irradiation area are not reproduced.

In addition, in a portion of the readout layer outside the region above the temperature T ₁ , the in-plane magnetization state is maintained, and the magneto-optical effect is not exhibited for the vertically incident light. Therefore, even if present in the light beam irradiation area, the recording bits existing outside temperatures T ₁ or more regions are not reproduced.

Further, according to the above-mentioned reproducing method, the temperature T
_{In three} or more regions, the magnetization of the intermediate layer disappears (or enters an in-plane magnetization state), so that the magnetization information of the recording layer is not transferred to the readout layer.

[0026] Therefore, only the recording bits existing in the outside temperature region and T ₃ or more at a temperature above T ₁ of the temperature region is transferred to the readout layer.

Therefore, in the magneto-optical recording medium, the reproduction resolution can be improved, and the recording density can be improved.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in Examples 1 to 6.

Embodiment 1 One embodiment of the present invention will be described below with reference to FIGS. 1, 7 and 8.

As shown in FIG. 7, the magneto-optical disk as the magneto-optical recording medium of this embodiment 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. 6, the overcoat film 7 is laminated in this order.

[0031] The readout layer 1 shows the plane magnetization at room temperature, which shifts to perpendicular magnetization at a temperature above T ₁ read temperature (see FIG. 8), as the readout layer 1, for example, rare earth 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 a high temperature. 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 larger than that of the compensating composition at room temperature, and the in-plane magnetization is not exhibited at room temperature but perpendicular. while so, it keeps the so that the perpendicular magnetization at the temperature T _1. Thus, when the temperature of the site where the light beam is irradiated is increased to the temperature T _1, the magnetic moment of the transition metal becomes relatively large, it balances the magnetic moment of the rare-earth metal, as shown perpendicular magnetization as a whole Become.

The readout layer 1 has a relatively large perpendicular magnetic anisotropy, for example, a Dy film having a thickness of 50 nm.
May be used _{0.35 (F e 0 .5 Co 0.5} ) 0.65.
Incidentally, temperatures T ₁ to the readout layer 1 shifts to perpendicular magnetization from in-plane magnetization is preferably 40 ° C. to 70 ° C..

The intermediate layer 3 has a perpendicular magnetization state at room temperature.
From the room temperature to the Curie temperature T _ThreePerpendicular magnetization up to
(See FIG. 8). This middle layer
Curie temperature T of 3_ThreeMeans that the readout layer 1 is in-plane
Temperature T for transition from magnetization to perpendicular magnetization₁Set higher than
(T₁<T_Three). As the intermediate layer 3, for example, a film thickness
Is 50nm Ho_0.28(Fe_0.85Co_0.15)_0.72, Film thickness
Is 50 nm Dy_0.21Fe_0.79Etc can be used
You. The Curie temperature T of the intermediate layer 3_ThreeIs 60 ° C. to 90
C is preferred.

The recording layer 2 is perpendicularly magnetized at room temperature.
From the room temperature to the Curie temperature T _TwoPerpendicular magnetization up to
(See FIG. 8). This recording layer
Curie temperature T of 2_TwoIs the Curie of the intermediate layer 3 described above.
Temperature T_ThreeHigher than (T_Three<T_Two). That is, on
Recording temperature T₁, T_Two, T_ThreeIs T₁<T_Three<T_Two Is in a relationship. As the recording layer 2, for example, a film thickness
Is 50 nm Dy_0.23(Fe_0.82Co_0.18)_0.77use
can do. The Curie temperature T of the recording layer 2
_TwoIs preferably from 120C to 180C.

The transparent dielectric film 5 is provided for improving reproduction characteristics, that is, for enhancing the rotation angle of the magnetic Kerr by an anti-reflection function.
N, SiN, AlSiN, AlSiON, TiO _{2 and the} like can be used, and the film thickness is set to a value obtained by dividing 波長 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 thickness of the transparent dielectric film 2 is 10 nm to 8
It is about 0 nm. The transparent dielectric film 6 is a protective film made of, for example, a nitride such as AlN and has a thickness of 50 n.
m.

In the above configuration, when recording is performed on the magneto-optical disk, a recording magnetic field is applied to the magneto-optical disk, and a high-power laser beam 8 is condensed by the objective lens 9 and irradiated onto the magneto-optical disk. It carried out by raising the temperature of the layer 2 to the vicinity of the Curie temperature T _2. Thereby, a recording bit is formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
FIG. 2A is a view of the magneto-optical disk as viewed from the side irradiated with the laser beam 8, and FIG. 2B is a sectional view taken along line AA of the magneto-optical disk of FIG. Magnetic layers 1 and 2
3 shows the magnetization state of 3.

First, the magneto-optical disk is irradiated with the laser beam 8 having a lower power than during 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 where the temperature is highest on the magneto-optical disk is shifted backward from the center of the laser beam 8. Will be in place. Therefore, the temperature of the readout layer 1 is reduced by the irradiation of the laser beam 8 to the temperature T.
_The region 33 (the center of the region) that rises to _one or more is located at a position shifted backward with respect to the irradiation region 22 (the center of the region) of the laser beam 8. The region 44 (the center of the region) where the temperature of the intermediate layer 3 rises to the Curie temperature T ₃ or more is the irradiation region 22 (the center of the region) of the laser beam 8.
Exists at a position shifted rearward with respect to.

[0040] Here, in the above intermediate layer 3, the temperature of the Curie temperature T ₃ or more areas 44, so that the magnetization disappears. On the other hand, portions other than the region 44 in the intermediate layer 3 exhibit 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 have a perpendicular magnetization state.
Is transferred to the intermediate layer 3.

Further, the readout layer 1, an area 33 where its temperature rises to a temperature above T _1, while exhibiting perpendicular magnetization state, thus showing an in-plane magnetization state at a site other than the region 33. In this case, the magnetization direction of the intermediate layer 3 is read out by the exchange coupling force acting between the intermediate layer 3 and the readout layer 1 in the region of the readout layer 1 that is inside the region 33 and outside the region 44. Transferred to layer 1. That is, the magnetization information of the recording layer 2 is transferred to the readout layer 1 via the magnetization of the intermediate layer 3, and the magnetization direction of the readout layer 1 in the region 33 and outside the region 44 is In the same direction as the magnetization direction.

As described above, since the magnetization information of the recording layer 2 is transferred to the readout layer 1 via the magnetization of the intermediate layer 3, the temperature becomes higher than the Curie temperature T ₃ of the intermediate layer 3. Thus, in the region 44 where the magnetization is no longer present in the intermediate layer 3, the magnetization information of the recording layer 2 is not transferred to the readout layer 1. That is, the region 44 where the magnetization is no longer present in the intermediate layer 3
In this case, the magnetization information of the recording layer 2 cannot exert an exchange coupling force on the readout layer 1. Therefore, the portion of the readout layer 1 corresponding to the region 44 is in a free state that does not receive the exchange coupling force from the intermediate layer 3, and its magnetization state depends on the characteristics of the readout layer 1, that is, the perpendicular magnetic anisotropy. It will depend on the size.

Since the readout layer 1 of this embodiment has a relatively large perpendicular magnetic anisotropy, the perpendicular magnetization state is maintained even in the region 44 where there is no exchange coupling force from the intermediate layer 3. Therefore, in the present embodiment, at the time of reproduction, an external magnetic field _Hex is applied to the magneto-optical disk so that the magnetization direction of the readout layer 1 corresponding to the region 44 is always aligned in the same direction. 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 having the highest temperature on the magneto-optical disk during reproduction is located at a position shifted backward from the center of the laser beam 8. For this reason,
The exposure area 22 of the laser beam 8, a portion of the temperature above T ₁ to a region 33 of transition from temperature in-plane magnetization of the readout layer 1 to perpendicular magnetization, and the intermediate layer 3 is the Curie temperature T ₃ or more Is a part of the region 44 which becomes. Therefore, even if it exists in the region 33 where the temperature is equal to or higher than the temperature T ₁ , the information 14 and 14 ′ that does not exist in the irradiation region 22 of the laser beam 8 is not reproduced.

The above-mentioned region 33 in the readout layer 1
In other parts, the in-plane magnetization state is maintained and does not show the magneto-optical effect with respect to the vertically 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 having the temperature T ₁ or higher is not reproduced.

As described 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 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. As a result, the magneto-optical disk of the present embodiment separates each recording bit from the magneto-optical recording medium proposed by the present inventors (see Japanese Patent Application No. 4-74605). And reproduction can be performed, and the recording density can be significantly improved.

When the laser beam 8 moves and reproduces the next recording bit, the temperature of the previously reproduced portion decreases, and the readout layer 1 shifts from perpendicular magnetization to in-plane magnetization.
Along with this, the portion where the temperature has decreased no longer exhibits the magneto-optical Kerr effect. Therefore, information is not reproduced from the portion where the temperature is lowered, and a signal from an adjacent bit which causes noise is not mixed.

Here, this embodiment will be described more specifically. Al, Gd, Dy, Ho, F
In a sputtering apparatus provided with e and Co, a polycarbonate disk substrate 4 having pregrooves and prepits was disposed so as to face the target. After evacuating the inside of the sputtering apparatus to 1 × 10 ⁻⁶ Torr, a mixed gas of argon and nitrogen was introduced into the apparatus, and power was supplied to an Al target to obtain a gas pressure of 4 × 10 ⁻⁶ Torr.
A transparent dielectric film 5 made of AlN was formed on the disk substrate 4 by sputtering at 10 ⁻³ Torr at a sputtering speed of 12 nm / min. This transparent dielectric film 5
As described above, this is for improving the reproduction characteristics, and the film thickness is set to a value obtained by dividing 1/4 of the wavelength of the reproduction light by the refractive index. In this embodiment, since the reproducing light having the wavelength of 800 nm is used, the 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 evacuation to 0 ^-6 Torr, argon gas was introduced into the apparatus, power was supplied to the Dy, Fe, and Co targets, and the gas pressure was 4 × 10 ^-3 Torr and the sputtering rate was 1
Sputter deposition is performed at 5 nm / min, and a 50 nm-thick Dy _0.35 (Fe _0.5 Co _0.5 ) film is formed on the transparent dielectric film 5.
_A readout layer 1 of _0.65 was formed. The readout layer 1 was in an in-plane magnetization state at room temperature, shifted to a perpendicular magnetization state at a temperature of 60 ° C. or higher (T ₁ = 60 ° C.), and had a Curie temperature of 320 ° C.

Next, while the power supplied to the Dy target was stopped, power was supplied to the Ho target, and sputter deposition was performed under the same conditions as those for forming the readout layer 1. On top, a 50 nm thick Ho
_0.28 was formed (Fe _0.85 Co _0.15) intermediate layer 3 made of _0.72. This intermediate layer 3 has a Curie temperature T ₃ of 90 ° C.
Of the perpendicular magnetization film.

Next, while the power supplied to the Ho target was stopped, power was supplied to the Dy target, and sputter deposition was performed under the same conditions as those for forming the readout layer 1. On top, a 50 nm thick Dy _0.23
A recording layer 2 made of (Fe _0.82 Co _0.18 ) _0.77 was formed. This recording layer 2 was a perpendicular magnetization 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 is introduced into the sputtering apparatus, power is supplied to the Al target, and a gas pressure of 4 × 10 ^-3 Torr and a sputtering rate of 12
A transparent dielectric film 6 made of AlN was formed on the disk substrate 4 by sputtering at a rate of nm / min. Here, the transparent dielectric film 6 only needs to have a thickness capable of protecting the magnetic layers (the recording layer 2, the intermediate layer 3, and the readout layer 1) from corrosion such as oxidation. In the embodiment, 5
The thickness was set to 0 nm.

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

A laser beam 8 is condensed and irradiated by the objective lens 9 onto the magneto-optical disk manufactured as described above, and the laser beam 8 is irradiated so that the relative linear velocity of the laser beam 8 to the magneto-optical disk becomes 10 m / s. The disk was rotated. 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 10 MHz and applied to the magneto-optical disk. Inverted magnetic domains having a length of 0.5 μm could be formed.

Thereafter, the power of the laser beam 8 is increased by 2 mW.
Then, when a constant magnetic field (external magnetic field H _ex ) of +5 kA / m was applied to the magneto-optical disk, the recorded information was reproduced. According to the reversal magnetic domain formed in the recording layer 2, the reproduction at a frequency of 10 MHz was performed. A signal could be obtained from the readout layer 1. When a 10 mW laser beam 8 for recording was continuously irradiated, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk. With 0.
Inverted magnetic domains having a length of 25 μm could be formed.

Thereafter, the power of the laser beam 8 is increased by 2 mW.
The recorded information was reproduced under the condition that a constant magnetic field (external magnetic field _Hex ) of +5 kA / m was applied to the magneto-optical disk, and the reproduction at a frequency of 20 MHz was performed according to the inverted magnetic domain formed in the recording layer 2. A signal could be obtained from the readout layer 1.

Comparative Example As a comparative example of the first embodiment,
The same recording and reproduction as in Example 1 were performed using the magneto-optical disk of Example 1 in which the intermediate layer 3 did not exist and having the configuration shown in FIG. When recording was performed at a frequency of 10 MHz, the frequency 1
Although a reproduced signal of 0 MHz could be obtained,
In the case where recording was performed at the frequency described above, adjacent recording information could not be separated, and a reproduced signal having a frequency of 20 MHz could not be obtained.

Embodiment 2 Another embodiment of the present invention will be described below with reference to FIGS. 2, 7 and 8.

The magneto-optical disk as the magneto-optical recording medium of this embodiment is different from that of the first embodiment except that the read layer 201 is used instead of the read layer 1 of the first embodiment.
Each of the layers other than the readout layer 201, namely, the substrate, the transparent dielectric film, the intermediate layer, the recording layer, the transparent dielectric film, and the overcoat film have the same configuration and various characteristics. , Since it is the same as the first embodiment,
Each of these layers is denoted by the same reference number as in Example 1,
Detailed description is omitted here (see FIG. 7).

The readout layer 201 exhibits an in-plane magnetization state at room temperature, like the readout layer 1 of the first embodiment, and has a temperature T _1.
(See FIG. 8) The perpendicular magnetization state is obtained at the above read temperature. The read layer 1 of the first embodiment has a relatively large perpendicular magnetic anisotropy. Has a relatively small perpendicular magnetic anisotropy. As the readout layer 201, a rare earth transition metal can be used.
Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 can be used.

The temperature T _{1 at which} the readout layer 201 shifts 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 from 120C to 180C. Each of the temperatures T ₁ , T _2, and T ₃ has a relationship of T ₁ <T ₃ <T ₂ .

In the above configuration, when recording is performed on the magneto-optical disk, a recording magnetic field is applied to the magneto-optical disk, and a high-power laser beam 8 is condensed by the objective lens 9 and irradiated onto the magneto-optical disk. It carried out by raising the temperature of the layer 2 to the vicinity of the Curie temperature T _2. Thereby, a recording bit is formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
FIG. 2A is a view of the magneto-optical disk as viewed from the side irradiated with the laser beam 8, and FIG. 2B is a sectional view taken along line AA of the magneto-optical disk of FIG. Magnetic layer 201
It indicates the magnetization state of 2.3.

First, the laser beam 8 having a lower power than during recording is irradiated on the magneto-optical disk. At this time, the laser beam 8 is the magneto-optical disc has moved in the direction indicated by the relative arrows Q with respect to the region 33 (region where the temperature rises to a temperature above T ₁ of the readout layer 201 by irradiation of the laser beam 8 Of the laser beam 8 is located at a position shifted backward with respect to the irradiation area 22 of the laser beam 8 (the center of the area). Moreover, (the central area) area 44 in which the temperature of the intermediate layer 3 is raised to the Curie temperature T ₃ or more, and be located at a position deviated backward with respect to the irradiation region 22 of the laser beam 8 (the center of the area) Become.

In this case, as in the first embodiment, the intermediate layer 3
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 a portion showing the perpendicular magnetization state other than the region 44.

In the readout layer 201,
As in the first embodiment, the magnetization information of the recording layer 2 is transferred to the readout layer 201 via the magnetization of the intermediate layer 3 in the region 33 and outside the region 44, so that the magnetization direction 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, the region 44 where there is no exchange coupling force from the intermediate layer 3 is in an in-plane magnetization state, and does not exhibit the magneto-optical effect with respect to perpendicular incident light. Therefore, the recording layer 2 corresponding to the area 44
Information 13 'and 14' recorded in the readout layer 201
Is no longer read by being masked by the in-plane magnetization. Therefore, in the present embodiment, it is not necessary to apply the external magnetic field _Hex used in the first embodiment to always align the magnetization direction of the readout layer corresponding to the region 44 in the same direction during reproduction.

As described above, at the time of reproduction, the portion having the highest temperature on the magneto-optical disk is located at a position shifted backward from the center of the laser beam 8. For this reason,
In the irradiation area 22 of the laser beam 8, the readout layer 20 is provided.
Temperature T _{1 at which} the temperature of ₁ shifts from in-plane magnetization to perpendicular magnetization
Part of the region 33 to be higher, and, and only part of the region 44 where the intermediate layer 3 is the Curie temperature T ₃ or more are present. Therefore, the information 14 that does not exist in the irradiation area 22 of the laser beam 8 even though it exists in the area 33.
14 'is not reproduced.

Further, in the portion other than the region 33 in the readout layer 201, the in-plane magnetization state is maintained, and the magneto-optical effect is not exhibited for the vertically 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 is not reproduced.

As described 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 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 this embodiment can reproduce even smaller recording bits than the magneto-optical recording medium proposed by the inventors of the present application (see Japanese Patent Application No. 4-74605). And the recording density can be significantly improved.

Then, when the laser beam 8 moves to reproduce the next recording bit, the temperature of the previously reproduced portion decreases, and the readout layer 201 shifts from perpendicular magnetization to in-plane magnetization. Along with this, the portion where the temperature has decreased no longer exhibits the magneto-optical Kerr effect. Therefore, information is not reproduced from the portion where the temperature is lowered, and a signal from an adjacent bit which causes noise is not mixed.

Here, the present embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
In the sputtering apparatus used in Example 1 provided with o, Fe, and Co, a polycarbonate disk substrate 4 having pre-grooves and pre-pits was disposed so as to face the target. With this sputtering apparatus, as in the first embodiment, the transparent dielectric film 5 has a film thickness of 60 n
m AlN, 50 nm thick G as the readout layer 201
_{d 0.28 (Fe 0.8 Co 0 .2} ) 0.72, film thickness as the intermediate layer 35
Dy _0.21 Fe _{0.79 with} a thickness of 0 nm and a thickness of 50 n for the recording layer 2
mDy _0.23 (Fe _0.82 Co _0.18 ) _0.77 , and 50 nm thick AlN as the transparent dielectric film 6 were sequentially formed.

The readout layer 201 made of Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 has an in-plane magnetization state at room temperature, and shifts to a perpendicular magnetization state at a temperature of 60 ° C. or more (T ₁ = 6).
0 ° C.) and its Curie temperature was 350 ° C. The intermediate layer 3 made of Dy _0.21 Fe _0.79 was a perpendicular magnetization 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 almost room temperature, and its Curie temperature T ₂ was 160 ° C.

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

A laser beam 8 is condensed and illuminated by the objective lens 9 onto the magneto-optical disk manufactured as described above, and the laser beam 8 is irradiated so that the relative linear velocity of the laser beam 8 to the magneto-optical disk becomes 10 m / s. The disk was rotated. 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 10 MHz and applied to the magneto-optical disk. Inverted magnetic domains having a length of 0.5 μm could be formed.

Thereafter, the power of the laser beam 8 is reduced to 2 mW.
When the recorded information was reproduced in this manner, a reproduced signal having a frequency of 10 MHz was obtained from the readout layer 201 in accordance with the inverted magnetic domains formed in the recording layer 2. In the present embodiment, the constant magnetic field (external magnetic field H _ex ) that was required at the time of reproduction in the first embodiment was unnecessary.

Further, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk while continuously irradiating the laser beam 8 of 10 mW for recording. 0.25 at 0.5 μm period
Inverted magnetic domains having a length of μm could be formed.

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

[Embodiment 3] Another embodiment 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 this embodiment is the same as the magneto-optical disk of the first embodiment except that the intermediate layer 303 is used instead of the intermediate layer 3 of the first embodiment. The configuration and various characteristics of each layer 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 are the same as those of the first embodiment. Therefore, these layers are denoted by the same reference numerals as in the first embodiment, 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, Dy _0.13 (Fe _0.5
May be used Co _{0 .5) 0.87} like. The temperature T at which the intermediate layer 303 shifts from perpendicular magnetization to in-plane magnetization.
₃ is preferably from 60C to 90C.

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

In the above configuration, when recording is performed on the magneto-optical disk, a recording magnetic field is applied to the magneto-optical disk, and a high-power laser beam 8 is condensed by the objective lens 9 and irradiated onto the magneto-optical disk. It carried out by raising the temperature of the layer 2 to the vicinity of the Curie temperature T _2. Thereby, a recording bit is formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
FIG. 2A is a view of the magneto-optical disk as viewed from the side irradiated with the laser beam 8, and FIG. 2B is a sectional view taken along line AA of the magneto-optical disk of FIG. Magnetic layers 1 and 2
It shows the magnetization state of 303.

First, the laser beam 8 having a lower power than during recording is irradiated on the magneto-optical disk. At this time, the laser beam 8 is the magneto-optical disc has moved in the direction indicated by the relative arrows Q with respect to the region 33 (region where the temperature of the readout layer 1 is increased to a temperature above T ₁ by irradiation of the laser beam 8 Of the laser beam 8 is located at a position shifted backward with respect to the irradiation area 22 of the laser beam 8 (the center of the area). The region 44 where the temperature of the intermediate layer 303 is increased to the temperature T ₃ or more (the center of the area) will be present at a position offset rearwardly relative to the irradiation region 22 of the laser beam 8 (the center of the area) .

Here, in the intermediate layer 303, the transition from the perpendicular magnetization state to the in-plane magnetization state occurs in the region 44 at the temperature T ₃ or higher. On the other hand, the region 4 in the intermediate layer 303
In regions other than 4, the perpendicular magnetization state is maintained, and the exchange coupling force acting between the recording layer 2 and the intermediate layer 303 transfers the magnetization direction of the recording layer 2 to the intermediate layer 303.

[0088] Also, the readout layer 1, an area 33 where its temperature rises to a temperature above T _1, while exhibiting perpendicular magnetization state, thus showing an in-plane magnetization state at a site other than the region 33. In this case, the magnetization direction of the intermediate layer 303 is read out at a portion of the readout layer 1 in the region 33 and outside the region 44 due to the exchange coupling force acting between the intermediate layer 303 and the readout layer 1. Transferred to layer 1. That is, the magnetization information of the recording layer 2 is transferred to the readout layer 1 via the magnetization of the intermediate layer 303, and the magnetization direction of the readout layer 1 inside the region 33 and outside the region 44 is In the same direction as the magnetization direction.

As described above, since the magnetization information of the recording layer 2 exerts an exchange coupling force on the readout 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 magnetization state, the exchange coupling force exerted on the readout layer 1 by the magnetization information of the recording layer 2 is significantly smaller than that in the case where the intermediate layer 303 is in the perpendicular magnetization state outside the region 44. As described above, in the region 44 in which the exchange coupling force acting between the recording layer 2 and the readout layer 1 is extremely weak, the magnetization state of the readout layer 1 depends on the characteristics of the readout layer 1, that is, the perpendicular magnetic anisotropy. It depends on the size of the sex.

The readout layer 1 of this embodiment has a relatively large perpendicular magnetic anisotropy.
In the region 44 where the exchange coupling force from the recording layer 2 becomes very weak, the perpendicular magnetization state is maintained and the recording layer 2 is directed in the same direction as the magnetization direction. However, since the exchange coupling force acting between the recording layer 2 and the readout layer 1 is very weak, by applying an appropriate external magnetic field _Hex to the readout layer 1, the readout layer 1 is in the region 33 and the region 44 With the magnetization information transferred from the recording layer 2 retained in the read layer 1 outside, the magnetization direction of the portion corresponding to the region 44 in the read layer 1 can always be aligned in the same direction. . Thus, by applying appropriate external magnetic field H _ex to the readout layer 1 during reproducing, information 13 present in the region 44 to a temperature T ₃ or more ', 14' is not to be reproduced.

As described above, at the time of reproduction, the portion having the highest temperature on the magneto-optical disk is located at a position shifted backward from the center of the laser beam 8. For this reason,
In the irradiated area 22 of the laser beam 8, a portion of the temperature above T ₁ in a region 33, and will be present some of the region 44 to a temperature T ₃ or more. Therefore, even if present in the region 33 to a temperature above T _1, the information 14, 14 that is not in the irradiated region 22 of the laser beam 8 'is not reproduced.

In the read layer 1 other than the region 33 where the temperature is equal to or higher than the temperature T ₁ , the in-plane magnetization state is maintained, and the magneto-optical effect is not exhibited for the vertically incident light. Therefore, even if present in the irradiated region 22 of the laser beam 8, the information 12 in the outer region 33 to a temperature above T ₁ ...
Does not play.

As described above, 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 in-plane magnetization to perpendicular magnetization. _A region 44 existing in the region 33 where the temperature is equal to or higher than 1 and the temperature of the intermediate layer 303 being equal to or higher than the temperature T ₃
Only the information 13 outside exists. As a result, the magneto-optical disk of the present embodiment separates each recording bit from the magneto-optical recording medium proposed by the present inventors (see Japanese Patent Application No. 4-74605). And reproduction can be performed, and the recording density can be significantly improved.

Then, when the laser beam 8 moves to reproduce the next recording bit, the temperature of the previously reproduced portion drops, and the readout layer 1 shifts from perpendicular magnetization to in-plane magnetization.
Along with this, the portion where the temperature has decreased no longer exhibits the magneto-optical Kerr effect. Therefore, information is not reproduced from the portion where the temperature is lowered, and a signal from an adjacent bit which causes noise is not mixed.

Here, this embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
Sputtering used in Example 1 with o, Fe, and Co
Pre-groove and pre-pit in
Using the polycarbonate disk substrate 4 as the target
They were placed facing each other. With this sputtering equipment,
As in the first embodiment, the transparent dielectric film 5 has a film thickness of 60n.
m AlN, Dy having a thickness of 50 nm as the readout layer 1
_0.35(Fe_0.5Co_0.5) _0.65And the thickness of the intermediate layer 303.
50nm Dy_0.13(Fe_0.5Co_0.5)_0.87, Recording layer 2
Dy with a film thickness of 50 nm_0.23(Fe_0.82Co_0.18)
_0.77AlN having a thickness of 50 nm is sequentially formed as the transparent dielectric film 6.
Next formed.

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 a temperature of 0 ° C or higher (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 used.}
No. 3 showed a perpendicular magnetization state at room temperature, shifted to an in-plane magnetization state at a temperature of 90 ° C. or more (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 almost room temperature, and its Curie temperature T ₂
Was 160 ° C.

Thereafter, an ultraviolet curable resin was applied on the transparent dielectric film 6 by spin coating, and then irradiated with ultraviolet light to form an overcoat film 7 on the transparent dielectric film 6. Note that a thermosetting resin may be used as the overcoat film 7.

A laser beam 8 is condensed and illuminated by the objective lens 9 onto the magneto-optical disk produced as described above, and the laser beam 8 is irradiated so that the relative linear velocity of the laser beam 8 to the magneto-optical disk becomes 10 m / s. The disk was rotated. When a 10 mW laser beam 8 for recording was continuously irradiated, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk. As a result, a reversal magnetic domain having a length of 0.25 μm could be formed.

Thereafter, the power of the laser beam 8 is increased by 2 mW.
The recorded information was reproduced under the condition that a constant magnetic field (external magnetic field _Hex ) of +5 kA / m was applied to the magneto-optical disk, and the reproduction at a frequency of 20 MHz was performed according to the inverted magnetic domain formed in the recording layer 2. A signal could be obtained from the readout layer 1.

[Embodiment 4] Another embodiment of the present invention is described below with reference to FIGS.

The magneto-optical disk as the magneto-optical recording medium of this embodiment is different from that of the third embodiment except that the read layer 401 is used instead of the read layer 1 of the third embodiment.
Each layer other than the readout 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 configuration as the magneto-optical disk of Since these layers are the same as in the third embodiment, these layers are denoted by the same reference numerals as those in the third embodiment, and detailed description thereof is omitted here (see FIG. 7). The readout layer 401 of the present embodiment is the same as the readout layer 20 of the second embodiment.
1 shows the same configuration and various characteristics as those of Example 1, and a detailed description thereof is omitted here.

The temperature T _{1 at which} the readout layer 401 shifts 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.. Each of the temperatures T ₁ , T ₂ , T ₃ is T ₁ <
T ₃ <it has a relationship of T _2.

In the above configuration, when recording is performed on the magneto-optical disk, a recording magnetic field is applied to the magneto-optical disk, and a high-power laser beam 8 is condensed by the objective lens 9 and irradiated onto the magneto-optical disk. It carried out by raising the temperature of the layer 2 to the vicinity of the Curie temperature T _2. Thereby, a recording bit is formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
FIG. 2A is a view of the magneto-optical disk as viewed from the side irradiated with the laser beam 8, and FIG. 2B is a sectional view taken along line AA of the magneto-optical disk of FIG. Magnetic layer 401
It indicates the magnetization state of 2.303.

First, a laser beam 8 having a lower power than during recording is applied to the magneto-optical disk. At this time, the laser beam 8 is the magneto-optical disc has moved in the direction indicated by the relative arrows Q with respect to the region 33 (region where the temperature of the readout layer 1 is increased to a temperature above T ₁ by irradiation of the laser beam 8 Of the laser beam 8 is located at a position shifted backward with respect to the irradiation area 22 of the laser beam 8 (the center of the area). The region 44 where the temperature of the intermediate layer 303 is increased to the temperature T ₃ or more (the center of the area) will be present at a position offset rearwardly relative to the irradiation region 22 of the laser beam 8 (the center of the area) .

In this case, as in the first embodiment, the intermediate layer 3
In 03, the magnetization direction of the recording layer 2 is transferred to the intermediate layer 303 by an exchange coupling force acting between the two layers of the recording layer 2 and the intermediate layer 303 in a portion showing a perpendicular magnetization state other than the region 44. .

Further, also in the readout layer 401,
As in the third embodiment, in a 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, so that
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 region 44 in which the exchange coupling force from the intermediate layer 3 is extremely weak is in an in-plane magnetization state, and exhibits a magneto-optical effect with respect to perpendicular incident light. Disappears. Therefore, the information 13 ′ and 14 ′ recorded on the recording layer 2 corresponding to the area 44 are not read out by being masked by the in-plane magnetization of the readout layer 401. Therefore, in this embodiment, during playback,
The external magnetic field _Hex for maintaining the magnetization direction of the readout layer corresponding to the region 44 in the same direction, which is required in the third embodiment, is not required.

As described above, at the time of reproduction, the portion having the highest temperature on the magneto-optical disk exists at a position shifted backward from the center of the laser beam 8. For this reason,
In the irradiation area 22 of the laser beam 8, a readout layer 40 is provided.
Temperature T _{1 at which} the temperature of ₁ shifts from in-plane magnetization to perpendicular magnetization
Part of the region 33 to be higher, and, and only part of the region 44 where the intermediate layer 3 is the Curie temperature T ₃ or more are present. Therefore, the information 14 that does not exist in the irradiation area 22 of the laser beam 8 even though it exists in the area 33.
14 'is not reproduced.

As described above, 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 401 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 this embodiment can reproduce even smaller recording bits than the magneto-optical recording medium proposed by the inventors of the present application (see Japanese Patent Application No. 4-74605). And the recording density can be significantly improved.

Then, when the laser beam 8 moves to reproduce the next recording bit, the temperature of the previously reproduced portion decreases, and the readout layer 401 shifts from perpendicular magnetization to in-plane magnetization. Along with this, the portion where the temperature has decreased no longer exhibits the magneto-optical Kerr effect. Therefore, information is not reproduced from the portion where the temperature is lowered, and a signal from an adjacent bit which causes noise is not mixed.

Here, the present embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
A disk substrate 4 made of paricarbonate having pre-grooves and pre-pits was placed in the sputtering apparatus used in Example 1 provided with o, Fe, and Co, facing the target. With this sputtering apparatus, as in the first embodiment, the transparent dielectric film 5 has a film thickness of 60 n
m AlN, and 50 nm thick G 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 thickness of 50 nm was sequentially formed as the transparent dielectric film 6.

The readout layer 401 made of Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 is in an in-plane magnetization state at room temperature and shifts to a perpendicular magnetization state at a temperature of 60 ° C. or more (T ₁ = 6).
0 ° C.) and its Curie temperature was 350 ° C. The intermediate layer 303 made of Dy _0.13 (Fe _0.5 Co _0.5 ) _0.87 exhibits a perpendicular magnetization state at room temperature, and shifts to an in-plane magnetization state at a temperature of 90 ° C. or more (T ₃ = 90 ° C.). The Curie temperature was 380 ° C. In addition, 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.

Thereafter, an ultraviolet curable resin was applied on the transparent dielectric film 6 by spin coating, and then irradiated with ultraviolet light to form an overcoat film 7 on the transparent dielectric film 6. Note that a thermosetting resin may be used as the overcoat film 7.

A laser beam 8 is condensed and illuminated on the magneto-optical disk manufactured as described above by the objective lens 9 so that the relative linear velocity of the laser beam 8 to the magneto-optical disk becomes 10 m / s. The disk was rotated. When a 10 mW laser beam 8 for recording was continuously irradiated, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk. As a result, a reversal magnetic domain having a length of 0.25 μm could be formed.

Thereafter, the power of the laser beam 8 is increased by 2 mW.
When the recorded information was reproduced in this manner, a reproduced signal having a frequency of 20 MHz could be obtained from the readout layer 401 in accordance with the inverted magnetic domains formed in the recording layer 2. In the present embodiment, the constant magnetic field (external magnetic field H _ex ) that was required at the time of reproduction in the third embodiment was unnecessary.

Embodiment 5 An embodiment of the present invention will be described.
The following is a description based on FIG. 5, FIG. 7, and FIG.

The magneto-optical disk as the magneto-optical recording medium of this embodiment is the same as the magneto-optical disk of the first embodiment except that the intermediate layer 503 is used instead of the intermediate layer 3 of the first embodiment. Each of the layers other than the intermediate layer 503, namely, the substrate, the transparent dielectric film, the readout layer, the recording layer, the transparent dielectric film, and the overcoat film have the same configuration and various characteristics as those in the first embodiment. Therefore, these layers are denoted by the same reference numerals as in the first embodiment, and detailed description thereof is omitted here (see FIG. 7).

[0121] The intermediate layer 503 shows an in-plane magnetization state at room temperature, the in-plane magnetization film which holds the plane magnetization from room temperature to the Curie temperature T ₃ (see FIG. 8), for example, film thickness 50NmDy _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 preferred.

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

In the above configuration, when recording is performed on the magneto-optical disk, a recording magnetic field is applied to the magneto-optical disk, and a high-power laser beam 8 is condensed by the objective lens 9 and irradiated onto the magneto-optical disk. It carried out by raising the temperature of the layer 2 to the vicinity of the Curie temperature T _2. Thereby, a recording bit is formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
FIG. 2A is a view of the magneto-optical disk as viewed from the side irradiated with the laser beam 8, and FIG. 2B is a sectional view taken along line AA of the magneto-optical disk of FIG. Magnetic layers 1 and 2
503 indicates the magnetization state.

First, the magneto-optical disk is irradiated with the laser beam 8 having a lower power than during 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 where the temperature is highest on the magneto-optical disk is shifted backward from the center of the laser beam 8. Will be in place. Therefore, the temperature of the readout layer 1 is reduced by the irradiation of the laser beam 8 to the temperature T.
_The region 33 (the center of the region) that rises to ₁ or more is located at a position shifted backward with respect to the irradiation region 22 (the center of the region) of the laser beam 8. Moreover, (the central area) area 44 in which the temperature of the intermediate layer 503 is increased to the Curie temperature T ₃ or more, and be located at a position deviated backward with respect to the irradiation region 22 of the laser beam 8 (the center of the area) Become.

Here, in the intermediate layer 503, the magnetization disappears in the region 44 whose temperature is equal to or higher than the Curie temperature T ₃ , while in the region other than the region 44, the magnetization disappears.
The in-plane magnetization state is maintained. In the above readout layer 1, an area 33 where its temperature rises to a temperature above T _1, while the perpendicular magnetization state, so that the plane magnetization is maintained in the portion other than the region 33. Therefore, in the region 33 where the temperature is equal to or higher than the temperature T ₁ and in the region outside the region 44 where the temperature is equal to or higher than the temperature T ₃ , the readout layer 1 exchanges with the recording layer 2 via the in-plane magnetization of the intermediate layer 503. Receiving the coupling force, the recording layer 2 faces in the same direction as the magnetization direction.

As described above, since 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, the magnetization does not exist in the intermediate layer 503. In the region 44, the magnetization information of the recording layer 2 is not transferred to the readout layer 1. That is, in the region 44 where the magnetization is no longer present in the intermediate layer 503, the magnetization information of the recording layer 2 becomes
The exchange coupling force cannot be applied to the readout layer 1. Therefore, the area 44 in the readout layer 1
Is in a free state that does not receive the exchange coupling force from the intermediate layer 503, and its magnetization state depends on the characteristics of the readout layer 1, that is, the magnitude of the perpendicular magnetic anisotropy.

Since the readout layer 1 of this embodiment has a relatively large perpendicular magnetic anisotropy, the perpendicular magnetization state is maintained even in the region 44 where the exchange coupling force from the intermediate layer 503 does not exist. Therefore, in the present embodiment, at the time of reproduction, an external magnetic field _Hex is applied to the magneto-optical disk so that the magnetization direction of the readout layer 1 corresponding to the region 44 is always aligned in the same direction. 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 having the highest temperature on the magneto-optical disk during reproduction is located at a position shifted backward from the center of the laser beam 8. For this reason,
The exposure area 22 of the laser beam 8, a portion of the temperature above T ₁ to a region 33 of transition from temperature in-plane magnetization of the readout layer 1 to perpendicular magnetization, and the intermediate layer 503 is the Curie temperature T ₃ or more Is a part of the region 44 which becomes. Therefore, even if it exists in the region 33 where the temperature is equal to or higher than the temperature T ₁ , the information 14 and 14 ′ that does not exist in the irradiation region 22 of the laser beam 8 is not reproduced.

The above-mentioned area 33 in the readout layer 1
In other parts, the in-plane magnetization state is maintained and does not show the magneto-optical effect with respect to the vertically incident light. Therefore, even if present in the irradiated region 22 of the laser beam 8, the information 12 ... outside region 33 to a temperature above T ₁ is not reproduced.

As described 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 in-plane magnetization to 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, the magneto-optical disk of the present embodiment separates each recording bit from the magneto-optical recording medium proposed by the present inventors (see Japanese Patent Application No. 4-74605). And reproduction can be performed, and the recording density can be significantly improved.

When the laser beam 8 moves and reproduces the next recording bit, the temperature of the preceding reproducing portion decreases, and the readout layer 1 shifts from perpendicular magnetization to in-plane magnetization.
Along with this, the portion where the temperature has decreased no longer exhibits the magneto-optical Kerr effect. Therefore, information is not reproduced from the portion where the temperature is lowered, and a signal from an adjacent bit which causes noise is not mixed.

Here, the present embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
Sputtering used in Example 1 with o, Fe, and Co
Pre-groove and pre-pit in
Using a disc substrate 4 made of Paris carbonate as a target
They were placed facing each other. With this sputtering equipment,
As in the first embodiment, the transparent dielectric film 5 has a film thickness of 60n.
m AlN, Dy having a thickness of 50 nm as the readout layer 1
_0.35(Fe_0.5Co_0.5) _0.65, As the intermediate layer 503
50nm Dy_0.09Fe_0.91And a film thickness of 50 for the recording layer 2.
Dy in nm_0.23(Fe_0.82Co_0.18)_0.77, Transparent dielectric
AlN having a thickness of 50 nm was sequentially formed as the film 6.

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 a temperature of 0 ° C or higher (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 had 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 almost room temperature, and its Curie temperature T ₂ was 160 ° C.

Thereafter, an ultraviolet curable resin was applied on the transparent dielectric film 6 by spin coating, and then irradiated with ultraviolet light to form an overcoat film 7 on the transparent dielectric film 6. Note that a thermosetting resin may be used as the overcoat film 7.

A laser beam 8 is condensed and irradiated by the objective lens 9 onto the magneto-optical disk manufactured as described above, and the laser beam 8 is irradiated so that the relative linear velocity of the laser beam 8 to the magneto-optical disk becomes 10 m / s. The disk was rotated. When a 10 mW laser beam 8 for recording was continuously irradiated, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk. As a result, a reversal magnetic domain having a length of 0.25 μm could be formed.

After that, the power of the laser beam 8 is increased to 2 mW.
The recorded information was reproduced under the condition that a constant magnetic field (external magnetic field _Hex ) of +5 kA / m was applied to the magneto-optical disk, and the reproduction at a frequency of 20 MHz was performed according to the inverted magnetic domain formed in the recording layer 2. A signal could be obtained from the readout layer 1.

Embodiment 6 Another embodiment of the present invention will be described below with reference to FIGS.

The magneto-optical disk as the magneto-optical recording medium of this embodiment is different from that of the fifth embodiment except that the read layer 601 is used instead of the read layer 1 of the fifth embodiment.
Each layer other than the readout 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 configuration as the magneto-optical disk of Since these layers are the same as in the fifth embodiment, the same reference numerals as those in the fifth embodiment are added to these layers, and detailed description thereof is omitted here (see FIG. 7). The readout layer 601 of the present embodiment is the same as the readout layer 20 of the second embodiment.
1 shows the same configuration and various characteristics as those of Example 1, and a detailed description thereof is omitted here.

The temperature T _{1 at which} the readout layer 601 shifts 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 ° C is preferred. Also, the Curie temperature T of the recording layer 2
₂ is preferably from 120C to 180C. The temperatures T ₁ , T _2, and T ₃ have a relationship of T ₁ <T ₃ <T ₂ .

In the above configuration, when recording is performed on a magneto-optical disk, a recording magnetic field is applied to the magneto-optical disk, and a high-power laser beam 8 is condensed by an objective lens 9 and irradiated on the magneto-optical disk. It carried out by raising the temperature of the layer 2 to the vicinity of the Curie temperature T _2. Thereby, a recording bit is formed on the recording layer 2.

Next, reproduction of information recorded on the magneto-optical disk will be described below with reference to FIG.
FIG. 2A is a view of the magneto-optical disk as viewed from the side irradiated with the laser beam 8, and FIG. 2B is a sectional view taken along line AA of the magneto-optical disk of FIG. Magnetic layer 601
It shows the magnetization state of 503.2.

First, the laser beam 8 having a lower power than during recording is irradiated on the magneto-optical disk. 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 where the temperature is highest on the magneto-optical disk is shifted backward from the center of the laser beam 8. Will be in place. Therefore, the temperature of the readout layer 1 is reduced by the irradiation of the laser beam 8 to the temperature T.
_The region 33 (the center of the region) that rises to _one or more is located at a position shifted backward with respect to the irradiation region 22 (the center of the region) of the laser beam 8. Moreover, (the central area) area 44 in which the temperature of the intermediate layer 503 is increased to the Curie temperature T ₃ or more, and be located at a position deviated backward with respect to the irradiation region 22 of the laser beam 8 (the center of the area) Become.

[0145] In this case, in the same manner as in Example 5, above the intermediate layer 503, the temperature of the Curie temperature T ₃ or more areas 44, one that would magnetization disappears, the portion other than the region 44 Thus, the in-plane magnetization state is maintained. In the above readout layer 601 is an area 33 where its temperature rises to a temperature above T _1, while trying to show the perpendicular magnetization state, the portion other than the region 33 in the in-plane magnetization state is maintained Become. Therefore, the temperature T
In region 33 becomes ₁ or more, and, in the region outside the region 44 to a temperature T ₃ above, the readout layer 601 is subjected to exchange coupling force from the recording layer 2 through the in-plane magnetization of the intermediate layer 503, It will be in the same direction as the magnetization direction of the recording layer 2.

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

On the other hand, in the region 44 where the magnetization is no longer present in the intermediate layer 503, the magnetization information of the recording layer 2 cannot exert an exchange coupling force on the readout layer 1. Therefore, the portion of the readout layer 1 corresponding to the region 44 is in a free state that does not receive the exchange coupling force from the intermediate layer 503, and its magnetization state depends on the characteristics of the readout layer 601; It will depend on the size.

Here, the readout layer 601 of this embodiment is
Since the perpendicular magnetic anisotropy is relatively small, the region 44 where there is no exchange coupling force from the intermediate layer 503 is in an in-plane magnetization state, and does not exhibit a magneto-optical effect with respect to vertically incident light. For this reason, the information 13 ′ and 14 ′ recorded on the recording layer 2 corresponding to the area 44 are read from the readout layer 6.
It is no longer read out by being masked by the 01 in-plane magnetization. Therefore, in the present embodiment, the external magnetic field _Hex for always aligning the magnetization direction of the readout layer corresponding to the region 44 in the same direction, which is required in the fifth embodiment during reproduction, is not required.

As described above, the portion having the highest temperature on the magneto-optical disk during reproduction is located at a position shifted backward from the center of the laser beam 8. For this reason,
In the irradiation area 22 of the laser beam 8, the readout layer 60 is provided.
Temperature T _{1 at which} the temperature of ₁ shifts from in-plane magnetization to perpendicular magnetization
Part of the region 33 to be higher, and, and only part of the region 44 where the intermediate layer 3 is the Curie temperature T ₃ or more are present. Therefore, the information 14 that does not exist in the irradiation area 22 of the laser beam 8 even though it exists in the area 33.
14 'is not reproduced.

Further, in the portion other than the region 33 in the readout layer 601, the in-plane magnetization state is maintained, and the magneto-optical effect is not exhibited for the vertically 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 is not reproduced.

As described 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 601 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 this embodiment can reproduce even smaller recording bits than the magneto-optical recording medium proposed by the inventors of the present application (see Japanese Patent Application No. 4-74605). And the recording density can be significantly improved.

Then, when the laser beam 8 moves to reproduce the next recording bit, the temperature of the previous reproducing portion decreases, and the readout layer 601 shifts from perpendicular magnetization to in-plane magnetization. Along with this, the portion where the temperature has decreased no longer exhibits the magneto-optical Kerr effect. Therefore, information is not reproduced from the portion where the temperature is lowered, and a signal from an adjacent bit which causes noise is not mixed.

Here, the present embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
A disk substrate 4 made of paricarbonate having pre-grooves and pre-pits was placed in the sputtering apparatus used in Example 1 provided with o, Fe, and Co, facing the target. With this sputtering apparatus, as in the first embodiment, the transparent dielectric film 5 has a film thickness of 60 n
m AlN, 50 nm thick G 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 readout layer 601 made of Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 has an in-plane magnetization state at room temperature, and shifts to a perpendicular magnetization state at a temperature of 60 ° C. or more (T ₁ = 6).
0 ° C.) and its Curie temperature was 350 ° C. The intermediate layer 3 made of Dy0.09Fe0.91 is used.
Indicates an in-plane magnetization state at room temperature, and its Curie temperature T ₃
Was 90 ° C. The above Dy _0.23 (Fe _0.82 C
o _0.18 ) The recording layer 2 of _0.77 is a perpendicular magnetization film having a compensation point at about room temperature, and its Curie temperature T ₂ is 16
It was 0 ° C.

Thereafter, an ultraviolet curable resin was applied on the transparent dielectric film 6 by spin coating, and then irradiated with ultraviolet light to form an overcoat film 7 on the transparent dielectric film 6. Note that 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 laser beam 8 is irradiated so that the relative linear velocity of the laser beam 8 to the magneto-optical disk becomes 10 m / s. The disk was rotated. When a 10 mW laser beam 8 for recording was continuously irradiated, a modulation magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk. As a result, a reversal magnetic domain having a length of 0.25 μm could be formed.

Thereafter, the power of the laser beam 8 is increased by 2 mW.
When the recorded information was reproduced in this manner, a reproduced signal having a frequency of 20 MHz could be obtained from the readout layer 601 according to the inverted magnetic domains formed in the recording layer 2. In the present embodiment, the constant magnetic field (external magnetic field H _ex ) that was required at the time of reproduction in the fifth embodiment was unnecessary.

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

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

The above substrate 701, 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 the first embodiment are the same, detailed description is omitted here.

[0162] The first magnetic layer 703 exhibits a perpendicular magnetization state at room temperature and perpendicular magnetization film that holds the perpendicular magnetization to the Curie temperature T _71. The first magnetic layer 703 has both functions of 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. The first magnetic layer 703, since the function of the reproduction layer is important, high Curie temperature T _71, also Kerr rotation angle theta _k increases as such is desirable. In this embodiment, as the first magnetic layer 703, Gd _0.10 Dy _0.13 Fe _0.54 Co _0.23 having a thickness of 50 nm is used. 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 the Gd _0.10 D
When _{K 0.13} Fe _0.54 Co _0.23 is irradiated with a laser beam having a wavelength of about 800 nm, the Kerr rotation angle Θ _k is relatively large at about 0.4. Therefore, Gd _0.10 Dy _0.13 Fe
_0.54 Co _0.23 is excellent as a reproducing layer.

The first magnetic layer 703 is formed of the above-described GdDyF
It is not limited to eCo, and other than that, for example, GdTbFeCo, TbFeCo, DyFeCo,
GdNbFe, NbTbFeCo, Pt / Co or Pd / Co may be used. In particular, the first magnetic layer 703
GdNbFe, NbTbFeCo, Pt / Co
Alternatively, in the case of using Pd / Co, a higher reproduction performance can be obtained with a reproduction light having a short wavelength, and therefore, an advantage that a higher recording density can be realized by using a short wavelength laser beam to reduce the beam diameter. There is.

The second magnetic layer 705 is a perpendicular magnetic film which exhibits a perpendicular magnetization state at room temperature and maintains the perpendicular magnetization state from room temperature to the Curie temperature. This second magnetic layer 705 is
Since a function as a recording layer is required, the Curie temperature is set to be 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 the present 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 formed of the above-described TbFeC
It is not limited to o, other than that, for example,
DyFeCo, GdTbFe, TbFe, DyFe or the like may be used.

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

In the case of this embodiment, an external magnetic field is applied to the magneto-optical disk at the time of recording. As shown in the figure, since the magnitude of this external magnetic field is set to 200 Oe, the second magnetic layer 705 is the temperature at which the magnetization reversal occurs (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 No. 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 to indicate the perpendicular magnetization at a temperature higher than the second magnetic layer magnetization reversing temperature T ₇₂ described above. For the third magnetic layer 704, for example, a rare earth transition metal such as GdFeCo can be used. In this reference example, the third
Gd _0.23 Fe _0.46 having a thickness of 40 nm as the magnetic layer 704
Co _0.31 is used. This Gd _0.23 Fe _0.46 Co _0.31
Shows an in-plane magnetization state at room temperature, the temperature T _{73 at} which the transition 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 embodiment, the transparent dielectric film 5 is made of AlN having a thickness of 80 nm, and the transparent dielectric film 6 is made of AlN having a thickness of 5 nm.
An ultraviolet curable resin film is used as the AlN of 0 nm and the overcoat film 7.

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

Here, FIG. 10 shows that the information bits 721 formed in the track and the irradiation of the laser beam 8 make the temperature of the second magnetic layer magnetization reversal temperature T72 or higher and the second magnetic layer 705 undergoes magnetization reversal. (Hereinafter referred to as a second magnetic layer magnetization reversal region) 722 and a region (hereinafter referred to as a region T3) in which the third magnetic layer 704 transitions from in-plane magnetization to perpendicular magnetization at a temperature T ₇₃ or more, and the third magnetic layer 704 exhibits perpendicular magnetization (hereinafter, referred to as a region). 723 of the third magnetic layer). Here, it is assumed that information is already recorded in both tracks adjacent to the track on which recording is actually performed, and the already recorded information is displayed as a bit pattern painted black. . Further, the magneto-optical disk is moving in the direction indicated by arrow R with respect to laser beam 8.

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

The recording bits formed on the second magnetic layer 705 are 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 is performed between the first magnetic layer 703 and the
This means that the third magnetic layer 704 is limited to only a region showing 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 becomes 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 723 is smaller than the magnetization reversal region 722 of the second magnetic layer, and consequently, the first magnetic layer 703 is formed with relatively small recording bits as compared with the recording bits formed on the second magnetic layer 705. Will be.

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

However, the portion of the second magnetic layer 705 where the magnetization state is disordered is the third magnetic layer 704
Is masked by the in-plane magnetization of the first magnetic layer 703.
Is not magnetically transferred. That is, the magneto-optical disk of the present reference example is configured such that 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
The disturbance of the information already recorded in No. 3 hardly 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 embodiment and the magneto-optical disk of the present embodiment in which the third magnetic layer 704 was omitted from the magneto-optical disk under the conditions shown in Table 1 below. FIG. 12 shows the change in the C / N of the reproduction signal with respect to the track pitch when information recorded on each magneto-optical disk is reproduced under the conditions shown in Table 1 below. Note that, in the same drawing, the case where the magneto-optical disk of the present reference example is used is indicated by a solid line, and the case where a conventional magneto-optical disk without the third magnetic layer 704 is used is indicated by a dotted line.

[0178]

[Table 1] As can be seen from the figure, as the track pitch is narrowed and the density is increased, in the case of the conventional (exchange-coupled two-layer film structure) magneto-optical disk without the third magnetic layer 704, the adjacent magnetic recording disk The C / N of the reproduction signal is significantly deteriorated due to the influence of the crosstalk between tracks. 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 the C / N of the reproduced signal is slightly deteriorated even at a high density. It is.

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

Further, the first to third magnetic layers 703 of the present reference example
13 are used only as recording layers, and as shown in FIG. 13, the intermediate layer and the readout layer used in Examples 1 to 6 are stacked in this order on a first magnetic layer 703 to form an exchange-coupled five-layer film structure. can do. That is, since the first magnetic layer 703 actually stores the high-density information in the exchange-coupling three-layer film of this embodiment, the first magnetic layer 703 is not used as the readout layer but only as the recording layer. This first magnetic layer 703 was made to function as the recording layer 2 shown in the first to sixth embodiments.
Is used as The magneto-optical recording medium using such a five-layer exchange-coupling film has the effect of improving the resolution at the time of reproduction as described in the first to sixth embodiments.
This also has the effect of avoiding the adverse effect of thermal interference on adjacent recording bits during recording, and can achieve high-density recording of information.

In each of the above embodiments, a magneto-optical disk is described as a magneto-optical recording medium. However, the present invention is not limited to this, and can be applied to a magneto-optical tape, a magneto-optical card, and the like.

The specific embodiments or examples described in the detailed description of the invention are only for clarifying the technical contents of the present invention, and are not limited to such specific examples. The present invention should not be construed in a narrow sense, but can be variously modified and implemented within the spirit of the present invention and the scope of the claims.

[0183]

According to the reproducing method of the magneto-optical recording medium of the present invention, of the bits recorded on the recording layer, the recording bits reproduced by irradiating the light beam exist within the light beam irradiation area. and present in the temperature above T ₁ in the region, and, since the only recording bits to be present outside the temperature T ₃ or more regions, an effect that it is possible to remarkably improve the recording density.

[Brief description of the drawings]

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

FIG. 2, showing Example 2, is an explanatory view showing a magnetization state of each magnetic layer of a magneto-optical disk irradiated with a laser beam.

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

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

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

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

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

FIG. 8 is an explanatory diagram showing the temperature dependency of the coercive force of each magnetic layer of the magneto-optical disk of FIGS. 1 to 6;

FIG. 9 illustrates a 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 where the second magnetic layer causes magnetization reversal by laser beam irradiation, and a region where the third magnetic layer exhibits perpendicular magnetization. FIG.

FIG. 11 shows a first magnetic layer and a second magnetic layer of the magneto-optical disk.
FIG. 4 is an explanatory diagram showing temperature dependency of a 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 view showing a configuration in which an intermediate layer and a readout layer of the magneto-optical disk of FIGS. 1 to 6 are further laminated on the first to third magnetic layers of the magneto-optical disk.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 201, 401, 601 Readout layer 2 Recording layer 3, 303, 503 Intermediate layer 4 Substrate 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

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Takahashi 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Kenji 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-5-205336 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 11/105

Claims (5)

(57) [Claims] 1. A recording layer which exhibits a perpendicular magnetization state at room temperature and maintains a perpendicular magnetization state from room temperature to a Curie temperature T ₂ , and is disposed on a light beam incident side with respect to the recording layer.
A readout layer which shows an in-plane magnetization state at room temperature and shifts to a perpendicular magnetization state at a temperature equal to or higher than T ₁ , and is provided between the readout layer and the recording layer; A reproducing method for a magneto-optical recording medium having an intermediate layer that shifts to an in-plane magnetization state at ₃ or more, and wherein the temperatures T ₁ , T ₂ , and T ₃ satisfy the relationship of T ₁ <T ₃ <T ₂ a is, the irradiation region of the reproducing light beam in the magneto-optical recording medium, to form a region comprising a T ₃ or T ₂ lower than temperature, the transfer from the recording layer of the magnetization in the the readout layer in that region A method for reproducing a magneto-optical recording medium, comprising shutting off. 2. A method of reproducing a magneto-optical recording medium according to claim 1, by applying an external magnetic field upon reproduction, the external magnetic field the magnetization direction of the area to be the T ₃ or more temperature in the readout layer A reproducing method for a magneto-optical recording medium , wherein the recording medium is aligned in the same direction according to 3. A method of reproducing a magneto-optical recording medium according to claim 1, without applying an external magnetic field upon reproduction, the in-plane direction in the direction of magnetization of the region serving as the T ₃ or more temperature in the readout layer A method for reproducing a magneto-optical recording medium , characterized by : 4. 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 disposed on the light beam incident side with respect to the recording layer.
While indicating plane magnetization at room temperature, the readout layer to transition to a perpendicular magnetization at a temperature above T _1, provided between the readout layer and the recording layer, shows a perpendicular magnetization state at room temperature, the Curie from room A reproducing method for a magneto-optical recording medium having an intermediate layer that maintains a perpendicular magnetization state up to a temperature T ₃ , wherein the temperatures T ₁ , T ₂ , and T ₃ satisfy the relationship of T ₁ <T ₃ <T ₂ there are, blocking the irradiation area of the reproducing light beam in the magneto-optical recording medium, to form a region comprising a T ₃ or T ₂ lower than temperature, the transfer from the recording layer of the magnetization in the the readout layer in that region Then , no external magnetic field is applied during reproduction, and
Plane direction the direction of magnetization of the region serving as the T ₃ or more temperature
A method for reproducing a magneto-optical recording medium, characterized by: 5. A recording layer which exhibits a perpendicular magnetization state at room temperature and maintains a perpendicular magnetization state from room temperature to the Curie temperature T ₂ , and is disposed on the light beam incident side with respect to the recording layer,
While indicating plane magnetization at room temperature, the readout layer to transition to a perpendicular magnetization at a temperature above T _1, provided between the upper Symbol readout layer and the recording layer, showed the plane magnetization at room temperature, room temperature from an intermediate layer that holds the plane magnetization to the Curie temperature T _3, the temperature T _1, T _2, T ₃ is, T ₁ <T ₃ <magneto-optical recording medium satisfy the relationship of T ₂ a reproducing method, the exposure area of the reproducing light beam in the magneto-optical recording medium, to form a region comprising a T ₃ or T ₂ lower than temperature, from the recording layer of the magnetization in the the readout layer in that region The transfer is cut off , and no external magnetic field is applied during reproduction.
Plane direction the direction of magnetization of the region serving as the T ₃ or more temperature
A method for reproducing a magneto-optical recording medium, characterized by: