JPH11191244A - Magneto-optical recording medium and reproducing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sufficient reproduced signal at the time of recording/reproducing at a small recording bit diameter and a smaller recording bit space by placing such a magnetic mask layer between a recording layer and a reproducing layer as enabling to suppress a magnetic coupling between a recording layer and a reproducing layer at a normal temperature but magnetically couple them at a high temperature. SOLUTION: A magnetic mask layer 3 arranged adjacently to a recording layer 4 prevents a reproducing layer 1 from being magnetized from a part 11 of which the temperature does not exceed a critical temperature within the recording layer 4. In such a manner, it becomes possible to remove a mask only on the part at the critical temperature or higher, with a magnetic mask state being maintained, and reproduce information in a desired recording magnetic domain by enlarging it in a reproducing layer 1. Moreover, if the reproducing layer 1 has a larger stable magnetic domain at the time of reproducing with a laser beam, signal quantity is increased and cause of a noise is decreased. A small coercive force is more advantageous to move a magnetic domain wall according to a magnetic field from the recording layer 4. Therefore, garnet, of which the coercive force is small and the magnetic domain wall is easily movable, is used for the reproducing layer 1, and enlarged reproduction is smoothly performed by easily moving recording bits by an external magnetic field.

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, and a magneto-optical card applied to a magneto-optical recording / reproducing apparatus, and a reproducing method therefor.

[0002]

2. Description of the Related Art Conventionally, magneto-optical recording media have been put to practical use as rewritable optical recording media. In such a magneto-optical recording medium, the recording bit diameter and the recording bit interval, which are the magnetic domains for recording, are smaller than the beam diameter of the light beam emitted from the semiconductor laser focused on the magneto-optical recording medium. When this happens, there is a disadvantage that the reproduction characteristics deteriorate.

[0003] Such a drawback is that, since adjacent recording bits fall within the beam diameter of the light beam condensed on the target recording bits, individual recording bits cannot be separated and reproduced. That is the cause.

In order to solve the above-mentioned disadvantage, Japanese Patent Laid-Open No.
No. 150418, a structure in which a non-magnetic intermediate layer is provided between a reproducing layer and a recording layer which are in an in-plane magnetization state at room temperature and become perpendicular magnetization with a rise in temperature, and the reproduction layer and the recording layer are magnetostatically coupled. Has been proposed.

[0005] Thereby, the recording magnetic domain information of the portion in the in-plane magnetization state is masked, and even when adjacent recording bits fall within the beam diameter of the focused light beam, the individual recording bits are separated. It is shown that reproduction becomes possible (first conventional example).

The 20th Annual Meeting of the Japan Society of Applied Magnetics (1996), 22pE-4, "Ultra-high-density magneto-optical disk by magnetic domain expansion reproduction" includes a non-magnetic intermediate layer between a recording layer and a reproduction layer. A magnetic domain enlarging method has been disclosed in which a magnetic field generated from a recording layer is used to transfer and reproduce data while forming a magnetic domain larger than the magnetic domain of the recording layer in a reproducing layer in a similar configuration with a layer interposed therebetween (second conventional example). Example).

[0007]

However, in the first conventional example, when recording / reproducing is performed with a smaller recording bit diameter and a smaller recording bit interval, the reproduction signal intensity decreases, and a sufficient reproduction signal can be obtained. It was confirmed that there was a problem of disappearing.

Also, in the second conventional example, when the recording density is increased and a large number of bits exist below the reproducing magnetic domain, the reproducing layer receives a magnetic field from a plurality of bits of the recording layer. However, there has been a problem that the reproducing layer cannot correctly receive the magnetic field from the bit to be truly reproduced.

When the magnetic layers are magnetostatically coupled to each other,
A magnetic field generated in the opposite direction by the magnetic field generated from the recording layer is generated around the reproducing magnetic domain, and there is a problem that the reproducing magnetic domain is difficult to expand under the influence of the magnetic field in the opposite direction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a recording / reproducing apparatus which can perform a sufficient reproduction even when recording / reproducing with a small recording bit diameter and a smaller recording bit interval. To get the signal.

[0011]

According to a first aspect of the present invention, there is provided a magneto-optical recording medium comprising: a reproducing layer made of garnet; and a recording layer which is magnetostatically coupled to the reproducing layer and has a perpendicular magnetization state from room temperature to the Curie temperature. A magneto-optical recording medium comprising: a recording layer and a reproducing layer disposed between the recording layer and the reproducing layer; the magnetic coupling between the recording layer and the reproducing layer being suppressed at room temperature; A magnetic mask layer that enables magnetic coupling with the reproduction layer.

The magneto-optical recording medium according to claim 2 is the magneto-optical recording medium according to claim 1, wherein the reproducing layer is
_{Bi x R 3-x M y} Fe 5-y O 12 ( metal R is selected at least one of yttrium or rare earth metal, M is Fe
Bi-substituted garnet represented by (trivalent metal that can be substituted with) and satisfies 0.2 ≦ x ≦ 3.0 and 0 ≦ y ≦ 2.0.

A magneto-optical recording medium according to a third aspect is the magneto-optical recording medium according to the first or second aspect,
The thickness of the reproducing layer is 40 to 300 nm.

A magneto-optical recording medium according to a fourth aspect is a reproducing method for reproducing information from the magneto-optical recording medium according to any one of the first to third aspects, wherein the information is recorded on the recording layer. The recording magnetic domain is enlarged and reproduced by the reproducing layer.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of a magneto-optical recording medium for explaining the principle of reproduction of a magneto-optical disk according to the present invention, and FIG. 2 is a sectional view for explaining the principle of reproduction of a conventional magneto-optical disk.

First, the conventional super-resolution reproduction operation will be described. In the conventional reproducing method, as shown in FIG. 2, a magnetic field generated from the recording layer 4 is received by the reproducing layer 1 and transferred to a magnetic domain of the reproducing layer 1. This magneto-optical recording medium comprises a reproducing layer 1 made of an alloy of a rare earth metal and a transition metal in a perpendicular magnetization state, and a recording layer 4 made of an alloy of a rare earth metal and a transition metal having a compensation temperature at room temperature. A non-magnetic intermediate layer 2 is formed. At least when the temperature is raised, the reproducing layer 1 and the recording layer 4 are configured to be magnetostatically coupled.

Here, when the light beam 5 is condensed and irradiated from the reproduction layer 1 side, a Gaussian distribution temperature distribution corresponding to the intensity distribution of the light beam 5 is formed on the medium. With the formation of this temperature distribution, the magnetization of the recording layer 4 increases and the recording layer 4
The magnetic field generated from the read layer 1 increases due to the magnetic field.
Is determined. That is, the magnetization of the recording layer 4 is transferred to the reproducing layer 1. By reproducing the information of the transferred portion, a super-resolution reproducing operation is realized.

In this reproducing method, as shown in FIG. 3A, the size of the magnetic domain transiently existing in the reproducing layer 1 is set to a size of about 1 μm, which is the spot size of the reproducing beam. If the size is larger than the size of the magnetic domain of the recording layer 4, the signal generated from the reproducing layer 1 at the time of reproduction increases.

However, the direction of magnetization in the reproducing layer 1 is determined by the magnetic field generated from the recording layer 4, and when information is recorded on the recording layer 4 at high density,
As described below, the magnetization transfer from the recording layer 4 cannot be performed well. That is, in the state where the isolated bit 100 is formed in the erased state as shown in FIG. 3A, the direction of the perpendicular magnetization in the reproducing layer 1 is effectively affected by only the magnetic field from the isolated bit 100, and thus functions effectively. In the case of high-density recording, the influence of adjacent recording bits 101 appears as shown in FIG. Since the magnetization direction of the adjacent bit 101 is opposite to that of the recording bit 100, the magnetization to be originally reproduced is weakened, and magnetic transfer becomes extremely difficult.
As a result, the information in the target range cannot be reproduced correctly,
It is more susceptible to external stray magnetic fields.

On the other hand, in the magneto-optical recording medium of the present invention shown in FIG. 1, a magnetic mask layer 3 is formed adjacent to the recording layer 4, and the magnetic mask layer 3 allows a predetermined temperature (in the recording layer 4). The magnetization from the portion 11 that is not heated above the critical temperature is masked. That is, the magnetic mask layer 3 prevents the magnetization from the portion 11 of the recording layer 4 from being transmitted to the reproducing layer 1.

As described above, by maintaining the state of the magnetic mask, it is possible to remove the mask only in the portion above the critical temperature, and to store information on only the desired recording magnetic domain heated in the recording layer 4 above the critical temperature. It is possible to reproduce (enlarge reproduction) by enlarging the reproduction layer 1 (forming a large magnetic domain in the reproduction layer 1).

Here, the magnetic mask layer 3 has no magnetization at a temperature higher than the critical temperature in order to effectively work the magnetostatic coupling between the recording layer 4 and the reproducing layer 1 in the range above the critical temperature. It is desirable that the magnitude of the magnetization is smaller than the magnitude of the magnetization at a temperature equal to or lower than the critical temperature, and that the Curie temperature of the magnetic mask layer 3 is lower than the Curie temperature of the recording layer 4. further,
In order to suppress the influence of the magnetic field generated from the recording layer 4 at room temperature on the reproducing layer 1, it is desirable that the magnitude of the magnetization of the magnetic mask layer 3 be larger than the magnitude of the magnetization of the recording layer 4 at room temperature.

When the reproducing layer 1 is reproduced with a laser beam, it is preferable that the size of the stable magnetic domain is large because the signal amount increases and the cause of noise is reduced. In addition, the domain wall needs to move in accordance with the magnetic field from the recording layer 4, and a characteristic having a small coercive force is advantageous.

When information is reproduced from the magneto-optical recording medium, erasing the magnetic domains formed in the reproducing layer 1 once leads to a smooth reproducing operation. When light is emitted, the magnetic domains are extinguished while the laser is extinguished, and the medium temperature is raised while the laser is emitting, and the recording magnetic domains of the recording layer are transferred to the reproducing layer for signal reproduction. And the quality of the reproduced signal can be made higher.

In the present invention, garnet is used as the reproducing layer in the above-described configuration of the magneto-optical recording medium. Garnet has the property that the coercive force is small and the domain wall moves easily. Therefore, the recorded bits can be easily moved by the external magnetic field. Until now, such characteristics have not led to practical use as a magneto-optical material. However, in the present invention, on the contrary, the above-mentioned enlarged reproduction is smoothly executed by utilizing this property.

When garnet is used as the reproducing layer in this manner, the information can be transferred to the reproducing layer by a small leakage magnetic field from the recording layer when performing enlarged reproduction because the coercive force is small. Since the domain wall moves easily, a large magnetic domain is easily formed in the reproducing layer, and the quality of the reproduced signal can be improved. The remarkable effect can be obtained.

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, a case where a magneto-optical disk is applied as a magneto-optical recording medium will be described.

The magneto-optical disk according to the present embodiment uses an in-plane magnetization layer as described later as a magnetic mask layer.
As shown in FIG. 5, a substrate 6, a reproducing layer 1 made of a Bi-substituted garnet, a nonmagnetic intermediate layer 2, an in-plane magnetic layer 10, a recording layer 4, a protective layer 7, and an overcoat layer 8 are laminated in this order. Disc body.

The substrate 6 is made of a transparent base material such as heat-resistant glass and is formed in a disk shape.

The reproducing layer 1 is made of, for example, Bi _2.1 Dy _0.9 Ga
A magnetic layer made of Bi substituted garnet consisting _0.9 Fe _4.1 O _12.

The non-magnetic intermediate layer 2 is made of AlN, SiN, Al
One layer of a dielectric such as SiN, SiO ₂ or Al, T
Nonmagnetic metals such as i and Ta, AlNi, AlTi, and AlT
a layer of a non-magnetic metal alloy composed of two or more kinds of metals including Al such as a, or a combination of the above dielectric and two or more layers of the above metal, and the reproducing layer 1 and the recording layer 4 are magnetostatically coupled. It is set as follows.

The in-plane magnetic layer 10 is made of a rare earth transition metal alloy,
Alternatively, it is a magnetic film containing a rare earth metal or a transition metal as a main component, and has a magnetization in a direction parallel to the film surface. As shown in FIG. 4, the in-plane magnetic layer 10, which is a kind of magnetic mask layer, masks the magnetic field generated from the perpendicular magnetization of the recording layer 4 at a temperature lower than the critical temperature by the in-plane magnetization, and
Prevents magnetic field leakage to Above the critical temperature, the composition is adjusted so that the mask effect is lost and the magnetic field generated from the recording layer 4 is easily transmitted to the reproducing layer.

The recording layer 4 is composed of a perpendicular magnetization film made of a rare earth transition metal alloy.

The protection layer 7 is made of AlN, SiN, AlSi
Dielectric such as N, SiO ₂ , or non-magnetic metal such as Al, Ti, Ta or Al such as AlNi, AlTi, AlTa
And is formed for the purpose of preventing oxidation of the rare earth transition metal alloy used for the recording layer 4 and has a thickness of 5 nm or more.
It is set in the range of 60 nm.

The overcoat layer 8 is formed by applying an ultraviolet curable resin or a thermosetting resin by spin coating and irradiating with ultraviolet light or heating.

Hereinafter, specific examples of the magneto-optical disk having the above-described configuration will be described by dividing into (1) a forming method and (2) recording / reproducing characteristics.

(1) Forming Method First, the reproducing layer 1 is formed on a glass substrate 6 with a composition of Bi _2.1
After evacuation to 1 × 10 ⁻⁶ Torr using a ceramic target adjusted to Dy _0.9 Ga _0.9 Fe _4.1 O ₁₂ , the glass substrate 6 was kept at a high temperature of 400 to 800 ° C., and argon gas and oxygen gas were discharged. It was prepared by a sputtering method in a mixed atmosphere (oxygen partial pressure 10%) at a gas pressure of 4 × 10 ⁻³ Torr. The film thickness was 100 nm. The Curie temperature was 210 ° C. and the coercive force was very small, 100 Oe.

Next, a mixed gas of argon and nitrogen is introduced, power is supplied to the Al target, and a gas pressure of 4 × 10
^Under the condition of ^-3 Torr, a nonmagnetic intermediate layer 2 of AlN was formed on the reproducing layer 1 to a thickness of 20 nm.

Next, power is supplied to the GdFeAl alloy target, the gas pressure is set to 4 × 10 ⁻³ Torr, and the in-plane magnetization layer made of (Gd _0.11 Fe _0.89 ) _0.75 Al _{0.25 is formed} on the nonmagnetic intermediate layer 2. 10 was formed with a film thickness of 40 nm. The in-plane magnetic layer 10 has a Curie temperature of 120 ° C., and has magnetization in a direction parallel to the film surface from room temperature to the Curie temperature.

Next, the inside of the sputtering apparatus is again set to 1 × 10 ^−6.
After evacuating to Torr, introducing argon gas,
A power is supplied to the TbDyFeCo alloy target, the gas pressure is set to 4 × 10 ⁻³ Torr, and a recording layer 4 made of Tb _0.11 Dy _0.11 (Fe _0.90 Co _0.10 ) _{0.78 is formed} on the in-plane magnetic layer 10 with a thickness of 150 nm. Formed. The recording layer 4
Has a compensation temperature of 25 ° C and a Curie temperature of 180 ° C
Met.

Next, a mixed gas of argon and nitrogen was introduced, power was supplied to the Al target, and a gas pressure of 4 × 10
^Under the condition of ^-3 Torr, a protective layer 8 of AlN was formed on the recording layer 4 to a thickness of 20 nm.

Next, an ultraviolet curable resin was applied on the protective layer 7 by spin coating, and the overcoat layer 8 was formed by irradiating ultraviolet rays.

For comparison, a magneto-optical disk having a structure without the in-plane magnetic layer 10 was manufactured as a conventional magneto-optical disk.

(2) Recording / reproduction characteristics The reproduction signal of the magneto-optical recording medium produced as described above was measured. The linear velocity is 3.
6m / s, bit length 0.20μm, reproduction wavelength 680nm
The C / N was measured under the following measurement conditions. As a result, C /
N showed 35.3 dB.

For comparison, a conventional disc was
The CNR was also measured for a magneto-optical disk having a configuration in which the in-plane magnetic layer 10 did not exist. As a result, in the conventional medium,
About 15.2 dB, and the magneto-optical recording medium of the present invention
It has been found that compared to the conventional example, it is improved by 20.1 dB. In the figure of merit, an improvement of about 10 times was observed.

This is considered to be due to the following reasons. The provision of the in-plane magnetization layer 10 ensures that the reproducing layer does not receive a magnetic field from a bit adjacent to the bit to be reproduced of the recording layer 4 but the magnetic field from the bit to be truly reproduced is correctly received by the reproducing layer. Can be. Since a Bi-substituted garnet was used as the reproducing layer 1,
The magnetic layer exhibits a large Faraday effect, and can obtain good signal quality. Note that the Bi-substituted garnet is a transparent magnetic film, and there is a possibility that the reproduction beam light is incident on the recording layer and the reflected light shows the Kerr effect to become a miscellaneous signal. The magneto-optical effect is much less than the magneto-optical effect of the recording layer made of a rare earth transition metal, and therefore does not cause much problem. Since a Bi-substituted garnet with a small coercive force was used,
Information is transferred more efficiently by a magnetic field generated from the recording layer. Since the recording layer 4 itself functions as a reflection layer, a good signal can be obtained.

In the present embodiment, the thickness of the reproducing layer 1 is 100 nm, but is preferably in the range of 40 to 300 nm. If it is too thin, a good Faraday effect cannot be obtained, and a sufficient reproduced signal cannot be obtained. On the other hand, if the thickness is too large, the sensitivity is lowered.

In the present embodiment, Bi _2.1 D
Although a reproducing layer of y _0.9 Ga _0.9 Fe _4.1 O ₁₂ was used, Bi _x
In _{R 3-x M y Fe 5} -y O 12, in order to obtain a sufficient Faraday effect, it is necessary to contain at least 0.2 or more Bi. In order to obtain a sufficient magneto-optical effect, it is necessary to set the Curie temperature to a certain high level. The temperature is 180 ° C. or higher, preferably 200 ° C. or higher, depending on the balance with the recording layer. For that purpose, y is preferably 0 ≦ y ≦ 2.0, and if 2.0 <y, the Curie temperature becomes too low.

The thickness of the nonmagnetic intermediate layer 2 is 20 nm.
However, the range of 1 to 80 nm is preferable. If the thickness of the non-magnetic intermediate layer is too small, a good magnetostatic coupling state cannot be obtained, and the quality of the reproduced signal is degraded. On the other hand, if the thickness is too large, the magnetostatic coupling force is reduced, and the quality of the reproduced signal is reduced.

The thickness of the in-plane magnetic layer 10 is set to 40 nm, but is preferably in the range of 2 to 60 nm. A mask effect can be obtained by forming even a small amount of the in-plane magnetic layer. On the other hand, if the thickness is too large, the transfer from the recording layer hardly occurs, so that the quality of the reproduced signal deteriorates.

In the present embodiment, the in-plane magnetic layer has GdFe
Although Al alloy was used, it is not limited to this,
What is necessary is just to show the similar characteristic. For example, GdF
e, GdFeCo, GdFe with Ti, Ta, Pt, A
An alloy containing one or more metals such as u and Cu may be used.

Although the thickness 4 of the recording layer was 150 nm,
The range of 40 to 250 nm is preferred. If the thickness is too small, the generated magnetic field is so small that the information on the recording layer cannot be transferred to the reproducing layer. If the thickness is too large, the sensitivity at the time of recording is reduced.

(Embodiment 2) In this embodiment, in the specific example of the magneto-optical disk shown in Embodiment 1 described above, a blocking layer 20 described later is used as a magnetic mask layer instead of the in-plane magnetization layer 10. It is an example (FIGS. 6 and 7) used,
Other configurations are the same as those of the first embodiment as shown in FIG.

In the first embodiment, the recording / reproducing characteristics in the case where the in-plane magnetic layer 3 having a Curie temperature of 120 ° C. is used, but in the present embodiment, as shown in FIG. At room temperature, the direction of the total magnetization is opposite to that of the recording layer, and a blocking layer 20 that suppresses the influence of a magnetic field generated from the recording layer on the reproducing layer is used.

In the low temperature region, the shielding layer 20 cancels out the magnetic field generated from the recording layer by the magnetic field in the opposite direction. Further, at a temperature higher than the critical temperature, it has a role of transferring the magnetization from the recording layer to the reproducing layer. For example, at room temperature, the barrier layer 20 has a rare earth metal sublattice moment larger than the transition metal sublattice moment (rare earth metal rich), and the recording layer 4 has a transition metal sublattice moment larger than the rare earth metal sublattice moment (transition metal rich). ), Exchange coupled with each other.

In such a configuration, since the transition metal sublattice moments of the blocking layer 20 and the recording layer 4 are aligned in the same direction, the directions of the total magnetization of the blocking layer 20 and the recording layer 4 are opposite. Therefore, in a low temperature state, the barrier layer 2
With 0, the magnetic field from the recording layer 4 can be canceled.
Further, if the total magnetization of the blocking layer 20 and the total magnetization of the recording layer 4 are adjusted to be substantially the same, the influence of the magnetic field on the reproducing layer 1 can be reduced to substantially zero.

In the portion where the temperature has risen,
Is that the total magnetization is reduced because the difference between the magnitude of the rare earth metal sublattice moment and the magnitude of the transition metal magnetic sublattice moment is reduced. However, in the recording layer 4, the magnitude of the rare earth metal sublattice moment and the transition metal magnetic sublattice moment is large. Since the difference in height increases, the total magnetization increases. For this reason,
When heated during reproduction, the balance between the magnetizations of the blocking layer 20 and the recording layer 4 is broken, and the magnetic field generated from the recording layer 4 affects the reproduction layer 1, and the magnetization of the recording layer 4 is transferred to the reproduction layer 1.

As described above, in the present embodiment, the barrier layer 20
Is provided, the magnetic field in the low temperature region of the recording layer 4 is masked in the low temperature region, and the magnetic field of the recording layer 4 is transferred to the reproducing layer 1 only in the high temperature region at the center of the beam spot.

Hereinafter, such a magneto-optical disk (1) will be described.
The formation method and (2) recording / reproducing characteristics will be described.

(1) Forming Method The forming method is the same as that of the first embodiment except for the blocking layer 20. As in the first embodiment, the reproduction layer 1 is formed on the glass substrate 6.
The non-magnetic intermediate layer 2 is formed, and then the blocking layer 20 is formed. The blocking layer 20 supplies electric power to the GdDyFeCo alloy target to make the gas pressure 4 × 10 ⁻³ Torr, and forms a composition (Gd _0.50 Dy _0.50 ) _0.28 F on the nonmagnetic intermediate layer 2.
e _0.72 and a film thickness of 40 nm. The Curie temperature is 120 ° C., and the film is a perpendicular magnetization film from room temperature to the Curie temperature.

Next, the recording layer 4 and the
A protective layer 7 is formed, and an overcoat layer 8 is formed on the protective layer 7.
Was formed.

(2) Recording / Reproduction Characteristics The reproduction signal of the magneto-optical recording medium manufactured as described above was measured. The linear velocity is 3.
6m / s, bit length 0.20μm, reproduction wavelength 680nm
The C / N was measured under the following measurement conditions. As a result, C /
N showed 35.0 dB.

Further, when compared with the conventional disk described in the first embodiment, it was found that the magneto-optical recording medium of the present invention was improved by 19.8 dB as compared with the conventional example. In this embodiment, the figure of merit is improved by about 10 times.

This is because the provision of the blocking layer 20 prevents the reproducing layer from receiving a magnetic field from a bit adjacent to a bit to be reproduced in the recording layer 4 and correctly reproduces only a magnetic field from a bit to be truly reproduced. This is because the layer was able to receive it. Also, this is because the Bi-substituted garnet is used as the reproducing layer 1 as in the first embodiment.

In the above, the case where the Curie temperature is 120 ° C. has been described as the barrier layer 20, but the same effect can be obtained even when the compensation temperature is 120 ° C. A specific example will be described below. The composition (Gd
_0.80 Dy _0.20 ) _0.24 Fe _0.76 , a film thickness of 40 nm was formed, and C / N was measured under the same measurement conditions. At this time, the barrier layer had a compensation temperature of 120 ° C. and a Curie temperature of 170 ° C. Also in this case, C / N of 35.0 dB was exhibited, and the mask effect as a blocking layer was confirmed.

In this embodiment, the thickness of the reproducing layer 1 is 1
Although it was set to 00 nm, a range of 40 to 300 nm is preferable. If it is too thin, a good Faraday effect cannot be obtained, and a sufficient reproduced signal cannot be obtained. On the other hand, if the thickness is too large, the sensitivity is lowered.

The thickness of the nonmagnetic intermediate layer 2 is set to 20 nm, but is preferably in the range of 1 to 80 nm. If the thickness of the nonmagnetic intermediate layer is too small, a good magnetostatic coupling state cannot be obtained,
The reproduction signal quality is degraded. On the other hand, if it is too thick, the magnetostatic coupling force will be small, and the quality of the reproduced signal will be degraded.

The thickness of the blocking layer 20 was set to 40 nm.
A range from 2 to 60 nm is preferred. The mask effect can be obtained by forming even a small amount of the blocking layer. on the other hand,
If the thickness is too large, the transfer from the recording layer hardly occurs, so that the quality of the reproduced signal deteriorates.

In this embodiment, GdDy is used as a barrier layer.
Although the Fe alloy was used, the present invention is not limited to this, and it is sufficient that the Curie temperature or the compensation temperature can be set to a predetermined temperature. For example, GdTbFe, TbFe, DyFe, Gd
An Fe alloy, a GdTbFe alloy, a DyFeCo alloy or the like may be used.

The thickness 4 of the recording layer was set to 150 nm,
The range of 40 to 250 nm is preferred. If the thickness is too small, the generated magnetic field is so small that the information on the recording layer cannot be transferred to the reproducing layer. If the thickness is too large, the sensitivity at the time of recording is reduced.

(Embodiment 3) In this embodiment, in the specific example of the magneto-optical disk shown in Embodiment 1 described above, a transfer layer 30 described later is used as a magnetic mask layer instead of the in-plane magnetization layer 10. It is an example (FIGS. 8 and 9) used,
Other configurations are the same as those of the first embodiment as shown in FIG.

In the first embodiment, the recording / reproducing characteristics when the in-plane magnetic layer 10 having a Curie temperature of 120 ° C. is used. In the present embodiment, as shown in FIG. A transfer layer 30 that exhibits in-plane magnetization at room temperature and perpendicular magnetization at a predetermined temperature or higher is used.

Since the transfer layer 30 exhibits in-plane magnetization in a portion not heated below the critical temperature, the magnetic field generated from the recording layer 4 is masked. That is, in the portion below the critical temperature, the transfer layer 30 prevents the magnetization of the recording layer 4 from being transferred to the reproducing layer 1. On the other hand, the portion showing perpendicular magnetization at or above the critical temperature exhibits perpendicular magnetization, so that the mask can be removed, and the magnetization of the recording layer 4 can be transferred to the reproducing layer 1.

As described above, in the present embodiment, the transfer layer 30
Is provided, the magnetization of the recording layer 4 is masked below the critical temperature, and the magnetization of the recording layer 4 is transferred to the reproducing layer 1 only in the region above the critical temperature at the center of the beam spot.

(1) Forming Method The forming method is the same as that of the first embodiment except for the transfer layer 30. As in the first embodiment, the reproduction layer 1 is formed on the glass substrate 6.
The non-magnetic intermediate layer 2 is formed, and then the transfer layer 30 is formed. The transfer layer 30 supplies electric power to the GdFeCo alloy target to make the gas pressure 4 × 10 ⁻³ Torr, and forms the composition Gd _0.30 (Fe _0.90 Co _0.10 ) on the nonmagnetic intermediate layer 2.
_It was formed with a thickness of _0.70 and a thickness of 40 nm. The predetermined temperature (critical temperature) at which the transition from in-plane magnetization to perpendicular magnetization was 120 ° C., and the Curie temperature was 150 ° C.

Next, on the transfer layer 30, the recording layer 4,
A protective layer 7 is formed, and an overcoat layer 8 is formed on the protective layer 7.
Was formed.

(2) Recording / Reproduction Characteristics The reproduction signal of the magneto-optical recording medium produced in this manner was measured. The measurement result will be described.
Here, using a magnetic field modulation method, a linear velocity of 3.6 m / s,
The C / N was measured under the measurement conditions of a bit length of 0.20 μm and a reproduction wavelength of 680 nm. As a result, C / N was 35.
1 dB was shown.

Further, when compared with the conventional disk described in the first embodiment, it was found that the magneto-optical recording medium of the present invention was improved by 19.9 dB as compared with the conventional example. In this embodiment, the figure of merit is improved by about 10 times.

This is because, by providing the transfer layer 30, the reproducing layer does not receive a magnetic field from a bit adjacent to the bit to be reproduced in the recording layer 4, and only the magnetic field from the bit to be reproduced is correctly reproduced. It depends on what the layer could receive. Also, as described in the first embodiment, a Bi-substituted garnet, which is a garnet, is used as the reproduction layer.

In this embodiment, the thickness of the reproducing layer 1 is 1
Although it was set to 00 nm, a range of 40 to 300 nm is preferable. If it is too thin, a good Faraday effect cannot be obtained, and a sufficient reproduced signal cannot be obtained. On the other hand, if the thickness is too large, the sensitivity is lowered.

The thickness of the nonmagnetic intermediate layer 2 is set to 20 nm, but is preferably in the range of 1 to 80 nm. If the thickness of the nonmagnetic intermediate layer is too small, a good magnetostatic coupling state cannot be obtained,
The reproduction signal quality is degraded. On the other hand, if it is too thick, the magnetostatic coupling force will be small, and the quality of the reproduced signal will be degraded.

Although the thickness of the transfer layer 30 was set to 40 nm,
A range from 2 to 60 nm is preferred. The mask effect can be obtained by forming a small amount of the transfer layer. on the other hand,
If the thickness is too large, the transfer from the recording layer hardly occurs, so that the quality of the reproduced signal deteriorates.

In this embodiment, GdFe is used as the transfer layer.
Although Co was used, the present invention is not limited to this, and any material having similar characteristics may be used. For example, GdFe, Gd
TbFe, GdNdFe, GdDyFe, GdDyFe
Co and the like.

Although the thickness 4 of the recording layer was set to 150 nm,
The range of 40 to 250 nm is preferred. If the thickness is too small, the generated magnetic field is so small that the information on the recording layer cannot be transferred to the reproducing layer. If the thickness is too large, the sensitivity at the time of recording is reduced.

(Embodiment 4) Embodiment 4 of the present invention is described below with reference to FIG.
In the present embodiment, a case where a magneto-optical disk is applied as a magneto-optical recording medium will be described. However, description of the same parts as in the first to third embodiments will be omitted.

The magneto-optical disk according to the fourth embodiment is the same as the magneto-optical disk according to the first embodiment except that a reflection layer 40 is formed between the nonmagnetic intermediate layer 2 and the in-plane magnetic layer 10. have.

As shown in FIG. 10, the magneto-optical disk according to the fourth embodiment has a substrate 6, a reproducing layer 1, a non-magnetic intermediate layer 2, a reflective layer 40, an in-plane magnetic layer 10, a recording layer 4, and a protective layer. The layer 8 and the overcoat layer 9 have a disk body laminated in this order.

In this way, the light beam 5 transmitted through the reproduction layer 1 is reflected by the reflection layer 40,
The reflected light can be used more efficiently. For this reason, it is possible to further prevent the unnecessary information of the recording layer 4 from being mixed into the reproduction signal, and to obtain more excellent reproduction signal quality.

Hereinafter, a specific example of the magneto-optical disk according to the present embodiment will be described with respect to (1) a forming method and (2) recording / reproducing characteristics.

(1) Forming Method The magneto-optical disk of the present embodiment is similar to the method of forming the magneto-optical disk of the first embodiment, except that an Al reflective layer is added to the configuration of the first embodiment. As in the first embodiment, the substrate 6
A reproducing layer 1 and a non-magnetic intermediate layer 2 were formed thereon. The thickness of the nonmagnetic intermediate layer 2 was 10 nm. Then, the Al reflection layer 4
0 on the non-magnetic intermediate layer 2 again,
After evacuating to 10 ^-6 Torr, argon gas was introduced, power was supplied to the Al target, and the gas pressure was 4 ×.
The film was formed to have a thickness of 30 nm with a pressure of 10 ⁻³ Torr.

Next, on the Al reflection layer 40, the in-plane magnetization layer 10, the recording layer 4, the protective layer 7, and the overcoat layer 8 are successively formed.
Was formed.

(2) Recording / reproduction characteristics The reproduction signal of the magneto-optical recording medium produced in this manner was measured.

Using a magnetic field modulation method, a linear velocity of 3.6 m /
The C / N was measured under the measurement conditions of s, bit length of 0.20 μm, and reproduction wavelength of 680 nm. As a result, C / N is 3
7.0 dB.

This is because the reflection layer 40 is provided.
Since the light beam 5 transmitted through the reproduction layer 1 is reflected by the reflection layer 40, it is possible to use the reflected light more efficiently and further prevent unnecessary information of the recording layer 4 from being mixed into the reproduction signal. This is because better reproduction signal quality can be obtained.

The reflection layer 40 is not limited to Al. For example, AlNi, AlTi, AlTa, Al
Pt, AlAu, AlCu, AiSi and the like can be mentioned.

In the present embodiment, the thickness of the reproducing layer 1 is 1
Although it was set to 00 nm, a range of 40 to 300 nm is preferable. If it is too thin, a good Faraday effect cannot be obtained, and a sufficient reproduced signal cannot be obtained. On the other hand, if the thickness is too large, the sensitivity is lowered.

The thickness of the non-magnetic intermediate layer 2 is 10 nm, but is preferably in the range of 1 to 80 nm. If the thickness of the nonmagnetic intermediate layer is too small, a good magnetostatic coupling state cannot be obtained,
The reproduction signal quality is degraded. On the other hand, if it is too thick, the magnetostatic coupling force will be small, and the quality of the reproduced signal will be degraded.

The thickness of the reflection layer 40 was set to 20 nm.
A range from 2 to 60 nm is preferred. The mask effect can be obtained by forming the reflective layer even a little. on the other hand,
If the thickness is too large, the transfer from the recording layer hardly occurs, so that the quality of the reproduced signal deteriorates.

The thickness of the in-plane magnetic layer 10 is set to 40 nm, but is preferably in the range of 2 to 60 nm. A mask effect can be obtained by forming even a small amount of the in-plane magnetic layer. On the other hand, if the thickness is too large, the transfer from the recording layer hardly occurs, so that the quality of the reproduced signal deteriorates.

Although the thickness 4 of the recording layer was set to 150 nm,
The range of 40 to 250 nm is preferred. If the thickness is too small, the generated magnetic field is so small that the information on the recording layer cannot be transferred to the reproducing layer. If the thickness is too large, the sensitivity at the time of recording is reduced.

In this embodiment, the reflection layer 40 is provided on the in-plane magnetization layer 10, but it is apparent that the reflection layer 40 may be provided on a magnetic mask layer such as a blocking layer or a transfer layer.

In the first to fourth embodiments, the BiDyGaFeO film is used for the reproducing layer. However, the present invention is not limited to this.
For example, Dy is replaced with one or more metals selected from y, Tb, Nd, Gd, Sm, etc., and Ga is replaced with Al, Cr,
It can be replaced by one or more metals selected from Mn, Cu, Ni, Si, Ti.

The recording layer is not limited to TdDyFeCO, but may be TbFeCo, DyFeCo, GdT
It is sufficient that bFeCo, GdDyFeCo, TbFe or the like satisfy the characteristics as the recording layer.

According to the magneto-optical recording medium and the reproducing method described in the first to fourth embodiments, the following effects can be obtained.

(1) Since the transfer of the magnetization information from the recording layer to the reproducing layer at least at room temperature can be suppressed,
At the time of reproduction, the influence of the magnetization from the adjacent recording magnetic domain can be eliminated, and only the information from the desired recording magnetic domain can be taken out, and the recording density can be increased. This enables recording and reproduction with a smaller bit diameter and a smaller recording bit interval. Further, by using garnet for the reproducing layer, the information can be transferred to the reproducing layer by a small leakage magnetic field from the recording layer due to its small coercive force.

(2) By expanding the recording magnetic domains of the recording layer in the reproducing layer and reproducing the data, the amount of reproduced signals can be increased and the signal quality can be improved. Here, since the domain wall of the garnet moves easily, it is easy to form a large magnetic domain in the reproduction layer, and the reproduction signal quality can be improved.

[0108] (3) Further, the reproduction layer _{Bi x R 3-x M y} Fe
_{5-yO 12} (R is a metal selected from at least one of yttrium and rare earth metals, M is a trivalent metal that can be substituted for Fe), and 0.2 ≦ x ≦ 3.0, 0 ≦ y ≦ 2 .
When the Bi-substituted garnet having a value of 0 is used, the Bi-substituted garnet has a small coercive force, so that the magnetic field generated from the recording layer can reliably transfer information and expand magnetic domains, and the Faraday effect is large. Is obtained.

(4) Further, in (1) to (3), when an in-plane magnetic layer is used as the magnetic mask layer, the magnetic field generated from the recording layer is masked by the in-plane magnetic layer. The magnetic field generated from does not reach the reproducing layer. On the other hand, when heated by the irradiation of the reproduction laser beam, the magnetization decreases,
The effect of blocking the magnetic field is eliminated, and the reproducing layer can be made to have perpendicular magnetization according to the recorded information by the magnetic field from the recording layer in the heated region. Here, since information only from the heated minute area is transmitted to the reproduction layer, a sufficient reproduction signal can be obtained even when recording and reproduction are performed with a small recording bit length and a small recording bit interval. .

(5) If the saturation magnetization of the magnetic mask layer at room temperature is made larger than the saturation magnetization of the recording layer in (4), the above-mentioned effect of blocking the magnetic field can be ensured.

(6) Further, in (4) and (5),
Due to heating during reproduction, the magnetic mask layer becomes higher than the Curie temperature and the magnetization disappears. However, the recording layer needs to hold information recorded at that time. Therefore,
It is desirable to set the Curie temperature of the recording layer higher than the Curie temperature of the in-plane magnetic layer.

(7) If a magnetic layer whose total magnetization of the blocking layer is opposite to the total magnetization of the recording layer in the low temperature region is used as the magnetic mask layer, the magnetic field generated from the recording layer affects the reproducing layer. Can be reduced. For this reason, the magnetization direction of the reproducing layer is determined by only the recording bit at the center of the beam spot of the reproducing laser beam. Therefore, even when recording and reproducing are performed with a small recording bit length and a small recording bit interval, a sufficient reproduction signal can be obtained.

(8) Further, in (7), if the magnetization of the magnetic mask layer is reduced by heating at the time of reproducing information, the magnetic field from the recording layer to the reproducing layer can be suppressed in a low temperature region.
In a high temperature region, a magnetic field can be leaked. Therefore, the magnetization direction of the reproducing layer can be reliably determined based on information from a single recording bit in the recording layer, so that the quality of the reproduced signal can be improved.

(9) In (7) and (8), the total magnetization of the magnetic mask layer at room temperature and the total magnetization of the recording layer at room temperature are made substantially the same to reproduce the magnetic field generated from the recording layer in the low temperature region. The influence on the layer can be further suppressed, and the quality of the reproduced signal can be further improved.

(10) In (7) to (9), by setting the Curie temperature of the magnetic mask layer lower than the Curie temperature of the recording layer, the temperature of the cut-off layer becomes higher than the Curie temperature due to heating during reproduction, and the magnetization disappears. Meanwhile, the recording layer can hold the information recorded at that time.

(11) In (7) to (10), by setting the compensation temperature of the magnetic mask layer lower than the Curie temperature of the recording layer, the interruption layer is heated to near the compensation temperature by heating during reproduction. While reducing its magnetization, the recording layer can retain the information recorded at that time.

(12) By forming the magnetic mask layer from a magnetic layer having an in-plane magnetization state at room temperature and a perpendicular magnetization state at a predetermined temperature, the influence of the magnetic field generated from the recording layer on the reproduction layer at room temperature is cut off. it can. Further, in the region heated by the irradiation of the reproducing laser beam, the transfer layer exhibits perpendicular magnetization, so that the above-described blocking effect is lost and the magnetic field leaks to the reproducing layer. For this reason, since the information of the recording layer is transferred to the reproducing layer only in the heated minute area, a sufficient reproducing signal can be obtained even when recording and reproducing are performed with a small recording bit length and a small recording bit interval. it can.

(13) In (12), by setting the Curie temperature of the magnetic mask layer lower than the Curie temperature of the recording layer, the influence of the transfer layer at the time of recording information on the recording layer is eliminated, and recording can be performed reliably.

(14) In (1) to (13), by setting the Curie temperature of the reproducing layer higher than the Curie temperature of the recording layer, good static characteristics can be obtained.

(15) In (1) to (14), the recording layer is formed by sequentially forming a transparent dielectric layer, a reproducing layer, a non-magnetic intermediate layer, a magnetic mask layer, a recording layer, and a protective layer on the substrate. A part of the small recording bits recorded in the recording layer is selected by the magnetic mask layer, transferred to the reproducing layer, and enlarged and reproduced in the magnetic domain of the reproducing layer, whereby a good reproduced signal can be obtained. Therefore, high-density recording becomes possible. Further, since the non-magnetic intermediate layer is provided, exchange coupling between the reproducing layer, the magnetic mask layer and the recording layer can be completely cut off, and good magnetostatic coupling can be realized.

(16) In (1) to (15), since the reflection layer is formed between the nonmagnetic intermediate layer and the magnetic mask layer, the light beam transmitted through the reproduction layer is reflected by the reflection layer. Further, since unnecessary signals can be prevented from being mixed in from the recording layer, a better reproduction signal quality can be obtained.

(17) In (1) to (16), the reflective layer is made of Al or Al and at least Ni, Ti, Ta, P
By being formed from an alloy with a metal selected from the group consisting of t, Au, Cu, and Si, and having a film thickness of 2 nm or more and 40 nm or less, characteristics as a reflective layer are optimized, and reproduction signal characteristics are improved. In addition, the magnetostatic coupling force between the reproducing layer, the magnetic mask layer, and the recording layer can be maintained in a good state.

(18) In (1) to (17), when information is reproduced from the magneto-optical recording medium of the present invention, it is possible to erase the magnetic domains formed in the reproducing layer once to smoothly perform the reproducing operation. When a laser beam for reproduction is emitted in pulses, the magnetic domains are extinguished while the laser is extinguished, and the medium temperature is raised while the laser is emitting light, so that the recording layer is formed on the reproduction layer. The recorded magnetic domain can be transferred to reproduce the signal, and the quality of the reproduced signal can be made higher.

[0124]

According to the present invention, by using garnet for the reproducing layer, the information can be transferred to the reproducing layer with a slight leakage magnetic field from the recording layer. In addition, large magnetic domains can be easily formed in the reproducing layer, and the quality of the reproduced signal can be improved.

[0125] _{Further, Bi x R 3-x M} y Fe 5-y O to the reproducing layer
₁₂ (R is a metal selected from at least one of yttrium and rare earth metals, M is a trivalent metal that can be substituted for Fe), and 0.2 ≦ x ≦ 3.0 and 0 ≦ y ≦ 2.0. When the Bi-substituted garnet is used, the Bi-substituted garnet has a small coercive force, so that the magnetic field generated from the recording layer can reliably transfer information and expand magnetic domains, and a large Faraday effect can provide a good reproduced signal. .

The thickness of the reproducing layer is set to 40 to 300 n.
By setting the value to m, the quality of the reproduced signal can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of reproduction in an example of a magneto-optical disk according to the present invention.

FIG. 2 is a diagram for explaining the principle of reproduction of a conventional magneto-optical disk.

FIG. 3 is a diagram illustrating a problem of magnetic domain expansion reproduction in a conventional magneto-optical disk.

FIG. 4 is a diagram for explaining the principle of reproduction of the magneto-optical disk according to the first embodiment.

FIG. 5 is a diagram showing a film configuration of a recording medium of the magneto-optical disk according to the first embodiment.

FIG. 6 is a diagram for explaining the principle of reproduction of the magneto-optical disk according to the second embodiment.

FIG. 7 is a diagram showing a film configuration of a recording medium of a magneto-optical disk according to a second embodiment.

FIG. 8 is a diagram for explaining a principle of reproducing a magneto-optical disk according to a third embodiment.

FIG. 9 is a diagram showing a film configuration of a recording medium of a magneto-optical disk according to a third embodiment.

FIG. 10 is a diagram showing a film configuration of a recording medium of a magneto-optical disk according to a fourth embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reproducing layer 2 non-magnetic intermediate layer 3 magnetic mask layer 4 recording layer 5 light beam 6 substrate 7 protective layer 8 overcoat layer 10 in-plane magnetized layer 20 blocking layer 30 transfer layer 40 reflective layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Zensho Murakami, 22-22 Nagaikecho, Abeno-ku, Osaka, Osaka Inside Sharp Corporation (72) Inventor Akira Takahashi 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka In the company

Claims (4)

[Claims] 1. A magneto-optical recording medium comprising: a reproducing layer made of garnet; and a recording layer which is magnetostatically coupled to the reproducing layer and has a perpendicular magnetization state from room temperature to a Curie temperature. A magnetic mask layer disposed between the reproducing layer and suppressing magnetic coupling between the recording layer and the reproducing layer at room temperature and enabling magnetic coupling between the recording layer and the reproducing layer at a high temperature; A magneto-optical recording medium comprising: 2. A magneto-optical recording medium of claim 1, the metal the reproducing _{layer, Bi x R 3-x M} y Fe 5-y O 12 (R is selected at least one of yttrium or a rare earth metal , M is a trivalent metal that can replace Fe)
i-substituted garnet, 0.2 ≦ x ≦ 3.0, 0 ≦
A magneto-optical recording medium characterized by satisfying y ≦ 2.0. 3. The magneto-optical recording medium according to claim 1, wherein said reproducing layer has a thickness of 40 to 300 nm. 4. A reproducing method for reproducing information from a magneto-optical recording medium according to claim 1, wherein a recording magnetic domain recorded on the recording layer is enlarged by the reproducing layer. A reproducing method characterized by reproducing.