JP2981474B2 - Magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium such as a magneto-optical disk, a magneto-optical tape, a magneto-optical card, etc., which is 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.

In a reference example to be described later, the magneto-optical recording medium has characteristics (such as avoiding signal mixing from previous recording bits) of the magneto-optical recording medium previously proposed by the inventor of the present invention, and is higher than that of the magneto-optical recording medium. A description will be given of a magneto-optical recording medium capable of separating and reproducing individual recording bits even when the recording density is further increased, and improving the recording density.

By the way, when the recording density is improved by increasing the reproduction resolution as described above, the following problem occurs. That is, in the case of a magneto-optical disk, as the track pitch is reduced, the bit period is reduced, and the linear recording density is increased, the effect of thermal interference on adjacent tracks during recording and the influence of thermal interaction between recording bits are increased. Can no longer be ignored. This is because the principle of magneto-optical recording itself utilizes a decrease in coercive force accompanying a rise in temperature of a magnetic material due to light beam irradiation.

That is, when the track pitch becomes narrower and the tracks come closer to each other, the effect of the temperature rise during recording in the recording track is already recorded in the adjacent track by the heat diffusion in the lateral direction. The information bit string, and the magnetic state there is disturbed.
Also, in the track direction, if the bit period is narrowed, the influence of thermal interference between the preceding and succeeding recording bits is inevitable, and the magnetic state of the already recorded information bits is disturbed as described above. For this reason, a technique of recording compensation such as devising the shape of the recording pulse is required, and the load on the apparatus system is increased.

The present invention has been made in view of the above, and has as its object the adverse effect of thermal interference on adjacent recording bits during recording, which is a problem in increasing the density in magneto-optical recording. It is an object of the present invention to provide a magneto-optical recording medium capable of avoiding the problem and improving the recording density.

[0018]

In order to solve the above-mentioned problems, a magneto-optical recording medium according to the present invention exhibits a perpendicular magnetization state at room temperature and maintains a perpendicular magnetization state from room temperature to the Curie temperature. A second magnetic layer having a Curie temperature relatively lower than that of the first magnetic layer, exhibiting a perpendicular magnetization state at room temperature, and maintaining the perpendicular magnetization state from room temperature to the Curie temperature; A temperature which is provided between the first magnetic layer and the second magnetic layer and shows an in-plane magnetization state at room temperature, while the direction of magnetization of the second magnetic layer is reversed by irradiation with a light beam in the presence of an external magnetic field. A third magnetic layer that transitions to a perpendicular magnetization state at a higher temperature.

The operation of the present invention will be described below.

According to the structure of the present invention, the recording of information, that is, the formation of the magnetic domain serving as the information bit is performed by first irradiating the light beam in the presence of an external magnetic field with the first magnetic layer having a lower Curie temperature than the first magnetic layer. This is performed by reversing the direction of magnetization in the two magnetic layers. The magnetization reversal of the second magnetic layer occurs due to the balance between the magnitude of the coercive force and the magnetic moment of the second magnetic layer, which has been reduced due to the temperature rise of the irradiated portion by the light beam irradiation, and the strength of the applied external magnetic field. The magnetization reversal region of the two magnetic layers is a region heated above a certain threshold temperature (reversal temperature).

Then, the second formed by the magnetization reversal
The recording bits on the magnetic layer are exchange-coupled through a third magnetic layer provided between the second magnetic layer and the first magnetic layer,
Eventually, magnetic transfer storage is performed on the first magnetic layer. In this case, the actual magnetic transfer between the second magnetic layer and the first magnetic layer is limited to only the region where the third magnetic layer exhibits perpendicular magnetization. That is, when the third magnetic layer is in the in-plane magnetization state, the exchange coupling force acting between the first magnetic layer and the second magnetic layer is very weak, and the magnetization state of the second magnetic layer is the first magnetic layer. Is not transcribed.

Here, since the temperature at which the third magnetic layer shifts from in-plane magnetization to perpendicular magnetization is set higher than the reversal temperature of the second magnetic layer, the region where the third magnetic layer exhibits perpendicular magnetization is , Smaller than the magnetization reversal region of the second magnetic layer. Therefore, as a result, a smaller recording bit is formed on the first magnetic layer than the recording bit formed on the second magnetic layer.

In the first recording process of reversing the magnetization of the second magnetic layer, thermal interference on adjacent tracks or adjacent bits in the same track occurs on the second magnetic layer due to thermal diffusion in the lateral and track directions. Occurs, and the magnetization state of the bit already recorded in the second magnetic layer is disturbed.

However, the portion of the second magnetic layer in which the magnetization state is disordered is masked by the in-plane magnetization of the third magnetic layer, and is not magnetically transferred to the first magnetic layer. The influence of the thermal interference generated in the layer does not reach the first magnetic layer for finally recording information.

Therefore, even if the track pitch is narrowed or the recording bit period is shortened, the above-mentioned magneto-optical recording medium can avoid adverse effects due to thermal interference on adjacent recording bits at the time of recording, and can reduce the recording density. Can be improved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference Example 1 Reference Example 1 will be described below with reference to FIGS. 1, 7, and 8. FIG.

As shown in FIG. 7, the magneto-optical disk as the magneto-optical recording medium of Reference Example 1 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.

[0028] 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. At a high temperature, the magnetic moment of the transition metal becomes larger than that of the rare earth metal. 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 exhibited at room temperature without exhibiting perpendicular magnetization. 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.
_0.35 (Fe _0.5 Co _0.5 ) _0.65 can be used.
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 is a perpendicular magnetization film which exhibits a perpendicular magnetization state at room temperature and maintains the perpendicular magnetization state from room temperature to the Curie temperature T ₃ (see FIG. 8). The Curie temperature T ₃ of the intermediate layer 3, the readout layer 1 mentioned above is set higher than temperature T ₁ of the shift to perpendicular magnetization from in-plane magnetization (T ₁ <T _3). As the intermediate layer 3, for example, Ho _0.28 (Fe _0.85 Co _0.15 ) _{0.72 having} a thickness of 50 nm, Dy _0.21 Fe _0.79 having a thickness of 50 nm, or the like can be used. The Curie temperature T ₃ of the intermediate layer 3 is 60 ° C. to 90 °.
C is preferred.

The recording layer 2 is a perpendicular magnetization film which exhibits a perpendicular magnetization state at room temperature and maintains the perpendicular magnetization state from room temperature to the Curie temperature T ₂ (see FIG. 8). Curie temperature T ₂ of the recording layer 2 is set higher than the Curie temperature T ₃ of the intermediate layer 3 described above (T ₃ <T _2). That is, the temperatures T ₁ , T ₂ , and T ₃ have a relationship of T ₁ <T ₃ <T ₂ . As the recording layer 2, for example, D having a thickness of 50 nm
y _0.23 (Fe _0.82 Co _0.18 ) _0.77 can be used. The Curie temperature T ₂ of the recording layer 2 is 120 ° C. to 1
80 ° C. is preferred.

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 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 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, 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 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.

Here, in the intermediate layer 3, the magnetization disappears in the region 44 whose temperature is equal to or higher than the Curie temperature T ₃ . 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.

[0039] As described above, the magnetization information of the recording layer 2, so via the magnetization of the intermediate layer 3 is adapted to be transferred to the readout layer 1, a middle layer 3 Curie temperature T ₃ or more 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. For this reason, in this reference example, 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 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 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, the present embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
In a sputtering apparatus provided with o, Fe, and Co, a polycarbonate disk substrate 4 having pre-grooves and pre-pits was placed facing a 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 ⁻³ Torr. Sputter rate 12nm / min
Is deposited on the disk substrate 4 by AlN.
The transparent dielectric film 5 was formed. The transparent dielectric film 5 improves the reproduction characteristics as described above,
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 the present reference example, the thickness of the transparent dielectric film 5 was set to 60 nm because reproduction light having a wavelength of 800 nm was used.

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
_An intermediate layer 3 made of _0.28 (Fe _0.85 Co _0.15 ) _0.72 was formed. 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
The 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 reference example, 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 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 under the condition that a constant magnetic field (external magnetic field Hex) of +5 kA / m was applied to the magneto-optical disk, a reproduced signal having a frequency of 10 MHz was obtained in accordance with the inverted magnetic domain formed in the recording layer 2. Was 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. 0.25μ at 0.5μm cycle
Inverted magnetic domains having a length of m could be formed.

Thereafter, the power of the laser beam 8 is increased by 2 mW.
Then, when the recorded information was reproduced in a state where a constant magnetic field (external magnetic field Hex) of +5 kA / m was applied to the magneto-optical disk, a reproduced signal having a frequency of 20 MHz was obtained according to the inverted magnetic domain formed in the recording layer 2. Was obtained from the readout layer 1.

[Comparative Example] As a comparative example of Reference Example 1,
The same recording and reproduction as in Reference Example 1 were performed using the magneto-optical disk of Reference Example 1 having no intermediate layer 3 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.

Reference Example 2 FIGS. 2 and 7 show Reference Example 2.
The following is a description based on FIG. 8 and FIG.

The magneto-optical disk as the magneto-optical recording medium of the present embodiment is the same as the magneto-optical disk of the above-described first embodiment except that the read layer 201 is used instead of the read layer 1 of the above-described embodiment. The readout layer 2
01, that is, the substrate, the transparent dielectric film, the intermediate layer,
The respective configurations and characteristics of the recording layer, the transparent dielectric film, and the overcoat film are the same as those in Reference Example 1. Therefore, these layers are denoted by the same reference numerals as in Reference Example 1, and will be described in detail. Here, it is omitted (see FIG. 7).

The readout layer 201 exhibits an in-plane magnetization state at room temperature, similarly to the readout layer 1 of Reference Example 1, and has a temperature T _1.
(See FIG. 8) At the above read temperature, the magnetic layer becomes perpendicularly magnetized. The readout layer 1 of Reference Example 1 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. 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 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 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 201
It indicates the magnetization state of 2.3.

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 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 Reference Example 1, 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.

Also, 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 during reproduction to keep the magnetization direction of the readout layer corresponding to the region 44 in the same direction used in the first embodiment.

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 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 of the readout layer 201 other than the region 33, 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 reference example can reproduce even smaller recording bits than the magneto-optical recording medium (refer to Japanese Patent Application No. 4-74605) proposed by the inventors of the present invention by separating each recording bit. And the recording density can be significantly improved.

When the next recording bit is reproduced by moving the laser beam 8, the temperature of the preceding reproducing portion is lowered, 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 Reference Example 1 provided with o, Fe, and Co, a polycarbonate disk substrate 4 having pre-grooves and pre-pits was placed facing the target. With this sputtering apparatus, in the same manner as in Reference Example 1, the transparent dielectric film 5 was
m AlN, 50 nm thick G as the readout layer 201
d _0.28 (Fe _0.8 Co _0.2 ) _0.72 , and a film thickness of 50 for the intermediate layer 3
Dy _0.21 Fe _0.79 nm, film thickness 50 nm as recording layer 2
Dy _0.23 (Fe _0.82 Co _0.18 ) _0.77 , transparent dielectric film 6
AlN having a thickness of 50 nm was 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.
Transition to the perpendicular magnetization state at a temperature of 60 ° C. or higher (T ₁ = 60
° C) and its Curie temperature was 350 ° C. Also,
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 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 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 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 reference example, the constant magnetic field (external magnetic field Hex) that was necessary at the time of reproduction in the above-described reference example 1 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. 0.25μ at 0.5μm cycle
Inverted magnetic domains having a length of m 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 20 MHz could be obtained from the readout layer 201 according to the inverted magnetic domains formed in the recording layer 2.

Reference Example 3 FIGS. 3 and 7 show Reference Example 3.
The following is a description based on FIG. 8 and FIG.

The magneto-optical disk as the magneto-optical recording medium of the present 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. Each of the layers other than the intermediate layer 303, that is, the substrate, the transparent dielectric film, the readout layer, the recording layer, the transparent dielectric film, and the overcoat film have the same configuration and various characteristics as those in Reference Example 1. Therefore, these layers are denoted by the same reference numerals as in Reference Example 1, and detailed description is omitted here (see FIG. 7).

The intermediate layer 303 has a perpendicular magnetization state at room temperature and has an in-plane magnetization state at a temperature T ₃ (see FIG. 8). For example, Dy _0.13 (Fe _0.5 C) having a thickness of 50 nm is used.
o _0.5 ) _0.87 etc. can be used. The intermediate layer 30
The temperature T _{3 at} which 3 changes from perpendicular magnetization to in-plane magnetization 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
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) .

[0086] Here, in the above-mentioned intermediate layer 303 is at a temperature T ₃ or more areas 44, the transition from perpendicular magnetization to in-plane magnetization state. 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.

[0087] 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 causes an exchange coupling force to act 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 located within the region 33 and outside the region 44. While the magnetization information transferred from the recording layer 2 to the readout layer 1 is kept, the magnetization direction of the portion corresponding to the region 44 in the readout layer 1 can always be aligned in the same direction. Thus, by applying appropriate external magnetic field Hex in 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.

[0091] In the region other than the region 33 to a temperature above T ₁ in the readout layer 1, the in-plane magnetization state is maintained, it does not exhibit magneto-optical effect with respect to the vertical incident light. Therefore, even if 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, 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. _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.

When the laser beam 8 moves to reproduce 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, the present embodiment will be described more specifically.

As targets, Al, Gd, Dy, H
In the sputtering apparatus used in Reference Example 1 provided with o, Fe, and Co, a polycarbonate disk substrate 4 having pre-grooves and pre-pits was placed facing the target. With this sputtering apparatus, in the same manner as in Reference Example 1, the transparent dielectric film 5 was
m AlN, Dy having a thickness of 50 nm as the readout layer 1
_0.35 (Fe _0.5 Co _0.5 ) _0.65 and a film thickness of 5 for the intermediate layer 303.
Dy _0.13 (Fe _0.5 Co _0.5 ) _{0.87 having} a thickness of 0 nm, Dy _0.23 (Fe _0.82 Co _0.18 ) _{0.77 having} a thickness of 50 nm as the recording layer 2, and AlN having a thickness of 50 nm as the transparent dielectric film 6 were sequentially 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 the perpendicular magnetization state at a temperature higher than ℃ (T ₁ = 60 ℃)
The Curie temperature was 320 ° C. The intermediate layer 303 made of Dy _0.13 (Fe _0.5 Co _0.5 ) _{0.87 is used} .
Showed a perpendicular magnetization state at room temperature, shifted to an in-plane magnetization state at a temperature of 90 ° C. or higher (T ₃ = 90 ° C.), and its Curie temperature was 380 ° C. In addition, the above Dy _0.23 (Fe
_The recording layer 2 made of _0.82 Co _0.18 ) _0.77 is a perpendicular magnetization film having a compensation point substantially at room temperature, and has a 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.

The laser beam 8 is condensed and irradiated 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 is 10 m / s. The disk was rotated. Then, when a modulating magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk in a state where the laser beam 8 of 10 mW for recording was continuously irradiated, a 0.5 μm period was applied to the recording layer 2. 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.
Then, when the recorded information was reproduced in a state where a constant magnetic field (external magnetic field Hex) of +5 kA / m was applied to the magneto-optical disk, a reproduced signal having a frequency of 20 MHz was obtained according to the inverted magnetic domain formed in the recording layer 2. Was obtained from the readout layer 1.

Reference Example 4 Reference Example 4 will be described below with reference to FIGS. 4 and 7.

The magneto-optical disk as the magneto-optical recording medium of the present embodiment has the same structure as 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 Reference Example 3, these layers are denoted by the same reference numerals as in Reference Example 3, and detailed description thereof is omitted here (see FIG. 7). Further, the readout layer 401 of the present embodiment is the same as the readout layer 20 shown in Reference Example 2.
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 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 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 of the magneto-optical disk shown in FIG. Magnetic layer 401
It indicates the magnetization state of 2.303.

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 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 Reference Example 1, 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. .

In the readout layer 401,
As in Reference Example 3, 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.
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 reference example, 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 reference example 3, is not required.

As described above, the part 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, 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, 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 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 reference example can reproduce even smaller recording bits than the magneto-optical recording medium (refer to Japanese Patent Application No. 4-74605) proposed by the inventors of the present invention by separating each recording bit. And the recording density can be significantly improved.

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 Reference Example 1 provided with o, Fe, and Co so as to face the target. With this sputtering apparatus, in the same manner as in Reference Example 1, the transparent dielectric film 5 was
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 ) _{0.87 having} a thickness of 50 nm as the intermediate layer 303, the recording layer 2
Dy _0.23 (Fe _0.82 C
o _0.18 ) _0.77 , 50 nm thick A as transparent dielectric film 6.
1N was formed sequentially.

The readout layer 401 made of Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72 has an in-plane magnetization state at room temperature.
Transition to the perpendicular magnetization state at a temperature of 60 ° C. or higher (T ₁ = 60
° C) and its Curie temperature was 350 ° C. Also,
Intermediate layer 3 composed of Dy _0.13 (Fe _0.5 Co _0.5 ) _0.87
No. 03 showed a perpendicular magnetization state at room temperature, shifted to an in-plane magnetization state at a temperature of 90 ° C. or higher (T ₃ = 90 ° C.), and its Curie temperature was 380 ° C. In addition, the above Dy _0.23 (F
The recording layer 2 made of e _0.82 Co _0.18 ) _0.77 is a perpendicular magnetization film having a compensation point substantially at 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 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. Then, in a state where the laser beam 8 of 10 mW 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 reference example, the constant magnetic field (external magnetic field Hex) that was required at the time of reproduction in the above-described reference example 3 was unnecessary.

Reference Example 5 Reference Example 5 will be described below with reference to FIGS. 5, 7, and 8.

The magneto-optical disk as the magneto-optical recording medium of the present 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, that is, 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 in Reference Example 1. Therefore, these layers are denoted by the same reference numerals as in Reference Example 1, and detailed description is omitted here (see FIG. 7).

[0120] 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 from 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 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 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 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 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 where the temperature is equal to or higher than the Curie temperature T ₃ , while in the region other than the region 44,
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 the present 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. For this reason, in this reference example, 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 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 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.

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 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
A disk substrate 4 made of paricarbonate having pre-grooves and pre-pits was placed in the sputtering apparatus used in Reference Example 1 provided with o, Fe, and Co so as to face the target. With this sputtering apparatus, in the same manner as in Reference Example 1, the transparent dielectric film 5 was
m AlN, Dy having a thickness of 50 nm as the readout layer 1
_0.35 (Fe _0.5 Co _0.5 ) _0.65 and a film thickness of 5 for the intermediate layer 503
Dy _0.09 Fe _{0.91 of} 0 nm, and a film thickness of 50 n as the recording layer 2
m Dy _0.23 (Fe _0.82 Co _0.18 ) _0.77 , transparent dielectric film 6
AlN having a thickness of 50 nm was sequentially 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, and
Transition to the perpendicular magnetization state at a temperature higher than ℃ (T ₁ = 60 ℃)
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 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 irradiated by the objective lens 9 on 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. Then, when a modulating magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk in a state where the laser beam 8 of 10 mW for recording was continuously irradiated, a 0.5 μm period was applied to the recording layer 2. 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.
Then, when the recorded information was reproduced in a state where a constant magnetic field (external magnetic field Hex) of +5 kA / m was applied to the magneto-optical disk, a reproduced signal having a frequency of 20 MHz was obtained according to the inverted magnetic domain formed in the recording layer 2. Was obtained from the readout layer 1.

Reference Example 6 Reference Example 6 will be described below with reference to FIGS. 6 and 7.

The magneto-optical disk as the magneto-optical recording medium of the present embodiment is the same as that of the above-mentioned embodiment except that the read-out layer 601 is used instead of the read-out layer 1 of the above-mentioned embodiment 5.
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 Reference Example 5, these layers are denoted by the same reference numerals as in Reference Example 5, and detailed description thereof is omitted here (see FIG. 7). Further, the readout layer 601 of this embodiment is the same as the readout layer 20 shown in Embodiment 2.
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 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 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 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.

In this case, as in Reference Example 5, in the intermediate layer 503, the magnetization disappears in the region 44 where the temperature is equal to or higher than the Curie temperature T ₃ , whereas in the region other than the region 44, the magnetization disappears. 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 reproducing the readout layer corresponding to the region 44 in the same direction at the time of reproduction, which is necessary in the fifth embodiment, is not required.

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 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 of the readout layer 601 other than the region 33, 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, 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 reference example can reproduce even smaller recording bits than the magneto-optical recording medium (refer to Japanese Patent Application No. 4-74605) proposed by the inventors of the present invention by separating each recording bit. And the recording density can be significantly improved.

Then, when the laser beam 8 moves and reproduces the next recording bit, the temperature of the preceding 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 Reference Example 1 provided with o, Fe, and Co so as to face the target. With this sputtering apparatus, in the same manner as in Reference Example 1, the transparent dielectric film 5 was
m AlN, 50 nm thick G as the readout layer 601
d _0.28 (Fe _0.8 Co _0.2 ) _0.72 , Dy _0.09 Fe _{0.91 having} a thickness of 50 nm as the intermediate layer 503, and a film thickness of 50 as the recording layer 2
Dy _0.23 (Fe _0.82 Co _0.18 ) _0.77 nm and AlN having a thickness of 50 nm as the transparent dielectric film 6 were 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 Dy _0.09 Fe _0.91 exhibits an in-plane magnetization state at room temperature, and its Curie temperature T ₃ is 90 ° C.
Met. The above Dy _0.23 (Fe _0.82 Co _0.18 )
_The recording layer 2 made of _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 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 with respect to the magneto-optical disk becomes 10 m / s. The disk was rotated. Then, when a modulating magnetic field of ± 15 kA / m was modulated at a frequency of 20 MHz and applied to the magneto-optical disk in a state where the laser beam 8 of 10 mW for recording was continuously irradiated, a 0.5 μm period was applied to the recording layer 2. 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 reference example, the constant magnetic field (external magnetic field Hex) that was required at the time of reproduction in the above-described reference example 5 was unnecessary.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS.

A magneto-optical disk as a magneto-optical recording medium according to the present embodiment includes a substrate 701, a transparent dielectric film 702, a first magnetic layer 703, a third magnetic layer 704, and a second magnetic layer 70.
5, a transparent dielectric film 706 and an overcoat film 707 are laminated in this order.
An exchange coupling force acts between 705.

The above substrate 701, transparent dielectric film 702,
The transparent dielectric film 706 and the overcoat film 707 are
Since the configurations and various characteristics of the substrate 4, the transparent dielectric film 5, the transparent dielectric film 6, and the overcoat film 7 in Reference Example 1 are the same, detailed description is omitted here.

[0161] 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 Θk is large like that is desired. In this embodiment mode, the first magnetic layer 703 is made of Gd _0.10 Dy _0.13 Fe _0.54 Co _0.23 having a thickness of 50 nm.
Is used. This Gd _0.10 Dy _0.13 Fe _0.54 Co _0.23
Curie temperature T ₇₁ is as high as 300 ° C.
The Kerr rotation angle Θk when _0.10 Dy _0.13 Fe _0.54 Co _0.23 is irradiated with a laser beam having a wavelength of about 800 nm,
It is relatively large, 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 made 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 magnetization film that 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 embodiment, as the second magnetic layer 705, Tb _0.20 Fe _0.75 Co _0.05 having a thickness of 100 nm is used.
The Curie temperature of Tb _0.20 Fe _0.75 Co _0.05 is 150
° C, which is relatively low, and is excellent as a recording layer.

Incidentally, 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 during recording, but as shown in FIG.
Since the magnitude of the external magnetic field is set to 2000e, the temperature at which the second magnetic layer 705 causes magnetization reversal (hereinafter, referred to as the temperature).
T ₇₂ , that is, the coercive force of the second magnetic layer 705 is equal to the magnitude of the external magnetic field (2000e).
The lower temperature corresponds to about 145 ° C.

The third magnetic layer 704 serves as an intermediate layer for mediating exchange coupling between the first magnetic layer 703 and the second magnetic layer 705, and shows 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 the present embodiment,
As the third magnetic layer 704, a 40 nm-thick Gd _0.23 Fe
_0.46 Co _0.31 is used. This Gd _0.23 Fe _0.46 Co
_0.31 indicates an in-plane magnetization state at room temperature, the temperature T _{73 at} which the 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 the present embodiment, the transparent dielectric film 5
80 nm thick AlN, the transparent dielectric film 6 is 50 nm thick AlN, and the overcoat film 7 is an ultraviolet curable resin film.

In the above arrangement, information is recorded on the magneto-optical disk by applying an external magnetic field of 2000e to the magneto-optical disk and condensing the 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 cause the magnetization reversal temperature T ₇₂ or higher of the second magnetic layer, and the second magnetic layer 705 undergoes magnetization reversal. A region (hereinafter, referred to as a second magnetic layer magnetization reversal region) 722 and a temperature T _{73 at which} the third magnetic layer 704 shifts from in-plane magnetization to perpendicular magnetization become higher than the temperature T ₇₃ .
The relative relationship with a region 723 where the magnetic layer 704 exhibits perpendicular magnetization (hereinafter, referred to as a third magnetic layer perpendicular magnetization region) 723 is shown.
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, which is the recording layer, is caused by the influence of 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, in the magneto-optical disk of the present embodiment, the influence of the thermal interference generated in the second magnetic layer 705 causes the first magnetic layer 70 for finally recording information.
3, and the information already recorded in the first magnetic layer 703 is hardly disturbed. Therefore, the first magnetic layer 70 of the magneto-optical disk
In No. 3, highly reliable high-density bit information is recorded.

Next, the magneto-optical disk of the present embodiment,
Information was recorded on the magneto-optical disk of the present embodiment on the magneto-optical disk from which the third magnetic layer 704 was omitted, under the conditions shown in Table 1 below. FIG. 12 shows the change in the C / N of the reproduced 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.
Shown in Note that, in the same figure, the case where the magneto-optical disk of the present embodiment is used is indicated by a solid line, and the third magnetic layer 704 is shown.
The case where a conventional magneto-optical disk without the above is used is indicated by a dotted line.

[0177]

[Table 1]

As is clear from the figure, as the track pitch is reduced and the density is increased, the third magnetic layer 704 is increased.
In the case of a conventional type (exchange-coupled two-layer film structure) magneto-optical disk having no recording, the C / N of the reproduced signal is remarkably deteriorated due to the influence of crosstalk between adjacent tracks during recording. On the other hand, in the case of the magneto-optical disk having the exchange-coupling three-layer film structure according to the present embodiment, crosstalk between adjacent tracks during recording is suppressed, and the C / N of the reproduced signal is not deteriorated even when the density is increased. It is slight.

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 7 of the present embodiment
As shown in FIG. 13, the intermediate layer and the readout layer used in Reference Examples 1 to 6 were laminated in this order on the first magnetic layer 703 to form an exchange coupling
It can have a layered film structure. That is, since the first magnetic layer 703 actually stores high-density information in the exchange-coupling three-layer film of the present embodiment, the first magnetic layer 703 is not used as a readout layer but as a recording layer. Only the first magnetic layer 703 is used as the recording layer 2 shown in the first to sixth embodiments. 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 shown in the first to sixth examples, and also has the effect of thermal interference with adjacent recording bits at the time of recording. In addition, it is possible to achieve the effect of avoiding the adverse effects caused by the above, and to realize the high-density recording of information.

In the above embodiments and reference examples, a magneto-optical disk is described as a magneto-optical recording medium. However, the present invention is not limited to this.
It can be applied to 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 magneto-optical recording medium of the present invention, the recording bits formed in the second magnetic layer by the light beam irradiation in the presence of an external magnetic field are exchanged via the perpendicular magnetization of the third magnetic layer. The coupling will eventually result in magnetic transfer storage in the first magnetic layer. In this case, due to the effect of thermal diffusion, thermal interference occurs on adjacent tracks or adjacent bits in the same track, and the magnetization state of bits already recorded in the second magnetic layer is disturbed. The portion where the magnetization state is disordered is masked by the in-plane magnetization of the third magnetic layer, and is not magnetically transferred to the first magnetic layer. Therefore, in the magneto-optical recording medium, even if the track pitch is narrowed or the recording bit period is shortened, adverse effects due to thermal interference on adjacent recording bits during recording can be avoided, and the recording density is significantly improved. It has the effect of being able to do so.

[Brief description of the drawings]

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

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

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

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

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

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

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 one embodiment of the present invention, and is an explanatory diagram illustrating a configuration of a magneto-optical disk.

10 is a diagram showing a relative relationship between an information bit pattern formed on the magneto-optical disk shown in FIG. 9, a region where the second magnetic layer undergoes magnetization reversal by laser beam irradiation, and a region where the third magnetic layer exhibits perpendicular magnetization. FIG.

FIG. 11 is an explanatory diagram showing the temperature dependence of the coercive force of the first magnetic layer and the second magnetic layer of the magneto-optical disk of 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 of FIG. 9 and a magneto-optical disk in which only the third magnetic layer is omitted from the magneto-optical disk.

13 is an explanatory diagram 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 of FIG. 9;

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-63-316343 (JP, A) JP-A-3-86950 (JP, A) JP-A-4-188449 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) G11B 11/10 506

Claims (1)

(57) [Claims] 1. A first magnetic layer which exhibits a perpendicular magnetization state at room temperature and maintains the perpendicular magnetization state from room temperature to the Curie temperature, and has a relatively lower Curie temperature than the first magnetic layer, A second magnetic layer, which exhibits a perpendicular magnetization state at room temperature and maintains the perpendicular magnetization state from room temperature to the Curie temperature, in this order on the substrate, and further comprises a first magnetic layer and a second magnetic layer. In addition, while showing the in-plane magnetization state at room temperature, the second magnetic layer transitions to the perpendicular magnetization state at a temperature higher than the temperature at which the direction of magnetization of the second magnetic layer is reversed by the light beam irradiation in the presence of the external magnetic field. 3
A magneto-optical recording medium having a magnetic layer.