JP3172066B2 - Magneto-optical recording medium and its recording / reproducing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magneto-optical recording / reproducing apparatus, for example, a magneto-optical disk, a magneto-optical tape,
The present invention relates to a magneto-optical recording medium such as a magneto-optical card and a method for recording and reproducing the same.

[0002]

2. Description of the Related Art Conventionally, a magneto-optical disk has been put to practical use as a rewritable magneto-optical recording medium. In such a magneto-optical disk, as the diameter of the recording bit and the interval (pitch) between the recording bits are reduced with respect to the beam diameter of the light beam of the semiconductor laser focused on the magneto-optical disk, the reproduction characteristics deteriorate. It has the problem of coming up. This is because adjacent recording bits enter the converged light beam, and it becomes impossible to separate and reproduce each recording bit.

In order to solve the above-mentioned drawbacks and increase the recording density, the recording bit of the magneto-optical recording medium, that is, the recording bit, is utilized by utilizing the temperature distribution due to the relative movement between the magneto-optical recording medium and the reproducing beam spot. When reproducing magnetic domains,
There has been proposed a configuration in which reproduction is performed only in a predetermined temperature region to increase the resolution of reproduction. In particular, Japanese Patent Application Laid-Open No. 4-255941 discloses a reproducing layer, a reproducing auxiliary layer, and a magneto-optical recording medium including a recording layer, and in reproducing, at a predetermined temperature region where both sides are masked under a reproducing beam spot. A configuration for reading a recording magnetic domain is disclosed. In this case, it is possible to perform ultra-high resolution reproduction without being limited by the diameter of the reproduction beam spot.

Further, in MORIS '94, several presentations on super-resolution magneto-optical reproducing technology have been made. No.29-K-05 "Magnetically-Induce"
d Super Resolution Using Magneto-Static Coupling "
In (p.126), the non-magnetic intermediate layer is provided between the reproducing layer and the recording layer, which is in an in-plane magnetization state at room temperature and becomes a perpendicular magnetization state as the temperature rises, thereby being in an in-plane magnetization state. It shows that a Front mask and a Rear mask are formed, and that the signal change by the rear mask is sharp.

[0005] Also, in the above-mentioned proceedings No. 29-K-06 "New Rea
dout Technique Using Domain Collapse on Magnetic M
ultilayer "(p.127) shows that good jitter characteristics can be obtained in a sudden signal change due to the rear mask,
Further, it is shown that the position of the recording magnetic domain can be detected with high accuracy by differentiating the reproduction signal.

[0006]

By the way, recently,
There is a demand for recording not only sound information but also image information and the like on a magneto-optical recording medium. That is, it is necessary to record image information and the like, and therefore, a magneto-optical recording medium having a larger capacity is required.

However, in the above-described conventional technique, a reproduction signal waveform having a sharp fall can be obtained by utilizing the instantaneous disappearance of magnetic domains in the reproduction layer. Only a gradual signal change with movement is obtained. For this reason, accurate position information cannot be detected in the rising portion of the reproduction signal waveform, and the recording density is prevented from being increased by compensating for the incorrect position information.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to enable reproduction of an ultra-high resolution which is not restricted by the spot diameter of a light beam, and to perform rising and standing operations. It is an object of the present invention to provide a large-capacity magneto-optical recording medium capable of obtaining a reproduced signal having a steep drop, for example, a rectangular shape and capable of sufficiently recording image information and the like. Another object is to provide an effective recording / reproducing method for this magneto-optical recording medium.

[0009]

According to another aspect of the present invention, there is provided a magneto-optical recording medium comprising: a recording layer having a recording magnetic domain in which information is recorded in a perpendicular magnetization direction; A reproducing layer having a reproducing magnetic domain in which information recorded in the recording layer is transferred by a perpendicular magnetization direction, and a Curie temperature laminated between the recording layer and the reproducing layer, the Curie temperature being lower than the Curie temperatures of the recording layer and the reproducing layer. In a first temperature range lower than the Curie temperature of the intermediate layer, the magnetization state of the recording layer is transferred by magnetic exchange coupling, and the reproducing layer has a temperature equal to or higher than the Curie temperature of the intermediate layer. In a second temperature range in which minute magnetic domains of a predetermined size in the reproducing layer become unstable, the magnetization direction matches the magnetization direction of the unrecorded portion of the recording layer, and is equal to or higher than the Curie temperature of the intermediate layer. Small magnetic domains In a third temperature range which results in a stable, is characterized by magnetization state of the recording layer by magnetostatic coupling is formed so as to be transferred.

According to the above configuration, the intermediate layer having a Curie temperature lower than the Curie temperatures of the recording layer and the reproducing layer is laminated between the recording layer and the reproducing layer. In the temperature range, the magnetization state of the recording layer is transferred by magnetic exchange coupling, and in the second temperature range, the magnetization direction matches the magnetization direction of the unrecorded portion of the recording layer,
In the temperature range described above, the magnetic state of the recording layer is transferred by magnetostatic coupling. For this reason, in the first temperature range and the third temperature range, the information recorded on the recording layer is transferred to the reproducing layer, while in the second temperature range, the information transferred to the reproducing layer disappears. I do.

Therefore, after erasing the information transferred to the reproducing layer whose temperature has been raised by the light beam irradiation, information on a part of the recording layer whose temperature has been further raised by the light beam irradiation, that is, the light beam It is possible to transfer only information of a part of the recording layer located in the spot to the reproducing magnetic domain of the reproducing layer and reproduce the information. This enables a super-resolution operation for reproducing information recorded in an area (recorded magnetic domain) smaller than the spot diameter of the light beam. As a result,
It is possible to provide a magneto-optical recording medium capable of sufficiently increasing the recording density required for a large capacity and sufficiently coping with recording of, for example, image information or the like which requires large capacity recording and reproduction.

According to a second aspect of the present invention, there is provided a recording / reproducing method for a magneto-optical recording medium. Steeply falls in the readout signal due to the instantaneous disappearance of the readout magnetic domain that occurs when the temperature of the readout signal shifts from the first temperature range to the second temperature range, and the temperature of the readout layer changes from the second temperature range. The method is characterized in that a steep rise of a reproduction signal caused by instantaneous generation of a reproduction magnetic domain, which is generated when the temperature shifts to the third temperature range, is detected by the light beam.

According to the above method, the steep fall of the reproduction signal generated when the temperature of the reproduction layer shifts from the first temperature range to the second temperature range by the light beam, and the temperature of the reproduction layer decreases. A steep rise of the reproduction signal that occurs when shifting from the second temperature range to the third temperature range is detected.

Therefore, it is possible to accurately detect the edge position of the recording magnetic domain of the recording layer by utilizing the sharp fall and the sharp rise of the reproduction signal. This enables a super-resolution operation for reproducing information recorded in an area smaller than the spot diameter of the light beam. As a result, it is possible to provide a recording / reproducing method for a magneto-optical recording medium which can sufficiently cope with recording of, for example, image information or the like which requires large-capacity recording / reproduction.

According to a third aspect of the present invention, there is provided a recording / reproducing method for a magneto-optical recording medium according to the second aspect of the present invention.
In the temperature range, the magnetization state of the recording layer is transferred to the reproduction layer by magnetic exchange coupling, and in the second temperature range, the magnetization direction of the reproduction layer is changed to the magnetization direction of the stray magnetic field generated from the unrecorded portion of the recording layer. In the third temperature range, the magnetization direction of the reproducing layer is matched with the magnetization direction of the stray magnetic field generated from the recording layer.

According to the above method, in the second temperature range, the magnetization direction of the reproducing layer matches the magnetization direction of the stray magnetic field generated from the unrecorded portion of the recording layer. Accordingly, it is possible to stably realize the disappearance and generation of the reproduction magnetic domain of the reproduction layer. Thereby, more stable recording and reproduction can be performed.

According to a fourth aspect of the present invention, there is provided a method for recording / reproducing a magneto-optical recording medium, comprising the steps of: On the other hand, an external magnetic field is further applied to transfer the magnetization state of the recording layer to the reproducing layer by magnetic exchange coupling in the first temperature range, and to change the magnetization direction of the reproducing layer to the external magnetic field in the second temperature range. In the third temperature range, the magnetization direction of the reproducing layer is matched with the magnetization direction of the stray magnetic field generated from the recording layer.

According to the above method, in the second temperature range, the magnetization direction of the reproducing layer is made to coincide with the direction of the external magnetic field, so that the reproduction magnetic domain of the reproducing layer disappears and is generated with the temperature rise due to the light beam irradiation. Can be stably realized. Thereby, more stable recording and reproduction can be performed.

According to a fifth aspect of the present invention, there is provided a recording / reproducing method for a magneto-optical recording medium according to the second, third, or fourth aspect of the present invention. The size of the recording magnetic domain of the recording layer,
The recording is performed at the position of the recording magnetic domain.

According to the above method, it is possible to independently record and reproduce information corresponding to the size of the recording magnetic domain and information corresponding to the position of the recording magnetic domain. Thereby, a plurality of information is recorded by one recording magnetic domain, that is,
Multiple recording is possible. As a result, recording / reproduction on a magneto-optical recording medium that can sufficiently cope with recording of image information or the like, for example, in which recording / reproduction of a much larger capacity is required, that is,
Recording and reproduction can be performed on a much larger capacity magneto-optical recording medium.

According to a sixth aspect of the present invention, there is provided a recording / reproducing method for a magneto-optical recording medium, the method comprising: Is obtained by the time difference between the falling part and the rising part of the reproduction signal, and the position of the recording magnetic domain is obtained by the time average of the falling part and the rising part of the reproduction signal.

According to the above method, the size of the recording magnetic domain is determined by the time difference between the falling portion and the rising portion of the reproduction signal, and the time average of the falling portion and the rising portion of the reproduction signal is obtained. The position of the recording magnetic domain is determined. As a result, the size and position of the recording magnetic domain can be detected more accurately, so that more stable recording and reproduction can be performed.

According to a seventh aspect of the present invention, there is provided a recording / reproducing method for a magneto-optical recording medium according to the fifth or sixth aspect of the present invention. A plurality of recording magnetic domains having a size and / or a position to be a reference at the time of reproduction are formed.

According to the above method, a plurality of recording magnetic domains having a size and / or a position to be a reference at the time of reproduction are formed in the recording layer. Therefore, at the time of reproduction, while referring to the output of the reproduction signal obtained from the recording magnetic domain,
Information can be reproduced. Accordingly, even when the characteristics of the entire recording layer have a certain degree of variation or when the power of the light beam fluctuates to a certain degree, the characteristics are further improved without being affected by these variations and fluctuations. Recording and reproduction can be performed.

According to a eighth aspect of the present invention, there is provided a recording / reproducing method for a magneto-optical recording medium according to the second, third, fourth, fifth, sixth or seventh aspect of the present invention. In the recording / reproducing method, the reproduction signal is differentiated.

According to the above method, since the reproduced signal is differentiated, a portion where the fluctuation in the reproduced signal is steep, that is,
The sharp fall and the sharp rise of the reproduction signal can be detected more easily. Therefore, it is possible to more accurately detect the position of the recording magnetic domain or the edge position of the recording magnetic domain. Thus, even if the recording magnetic domain is further reduced and the recording density is increased, the information recorded in the recording magnetic domain can be reproduced. That is, higher-density recording and reproduction can be realized.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS. still,
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 this embodiment is
As shown in FIG. 2, a disk body 10 in which a substrate 1, a transparent dielectric layer 2, a reproducing layer 3, an intermediate layer 9, a recording layer 4, a protective layer 5, and an overcoat layer 6 are laminated in this order. have. The substrate 1 is made of, for example, a transparent base material such as polycarbonate and is formed in a disk shape. The transparent dielectric layer 2 is made of a transparent dielectric. Reproduction layer 3
Consists of a rare earth transition metal alloy. The reproducing layer 3 has a reproducing magnetic domain in which the magnetization direction of the recording magnetic domain 4a is transferred by the stray magnetic field 9a generated from the recording layer 4. The middle layer 9
It is a perpendicular magnetization film (magnetic film) made of a rare earth transition metal alloy.

In such a magneto-optical disk, a Curie temperature recording method is used as a recording method, and a light beam 8 emitted from a semiconductor laser is focused on a reproducing layer 3 by an objective lens (condensing lens) 7. Information is recorded and reproduced by a magneto-optical effect known as a polar Kerr effect. The polar Kerr effect is a phenomenon in which magnetization is perpendicular to the incident surface, and the direction of rotation of the polarization plane of reflected light is reversed depending on the direction of magnetization.

The recording layer 4 is made of a rare-earth transition metal alloy perpendicular magnetization film having a compensation temperature at about room temperature. The recording layer 4
It has recording magnetic domains 4a in which digital information is recorded in each of the perpendicular magnetization directions that are antiparallel.

Here, the temperature dependence of the stable magnetic domain width in the reproducing layer 3 will be described. The above-mentioned stable magnetic domain width indicates a stripe-shaped magnetic domain width that can be stably present at each temperature when the reproducing layer 3 is a single layer. The change in the stable magnetic domain width of the reproducing layer 3 with respect to the change in temperature was measured.
The results are shown in a graph in FIG. As can be seen from the figure, in the reproducing layer 3 according to the present embodiment, the stable magnetic domain width becomes smaller as the temperature rises, and the magnetic domain having a width of 0.4 μm becomes unstable at a temperature lower than 120 ° C. It is understood that the magnetic domain having a width of 0.4 μm becomes stable at a temperature of not less than ° C.

In the present embodiment, the Curie point (temperature) of the intermediate layer 9 is set to a temperature lower than the Curie point of the reproducing layer 3 and the Curie point of the recording layer 4.
The temperature range below the Curie point of the intermediate layer 9 is referred to as a _first temperature range T1, and the temperature range above the Curie point of the intermediate layer 9 and in which the magnetic domain having a width of 0.4 μm is unstable is defined as a second temperature range T1. called T _2, the magnetic domain of the 0.4μm wide referred stable temperature range and the third temperature range T _3. For example, FIG. 3 shows the first case where the Curie point of the intermediate layer 9 is 90 ° C.
Temperature range T ₁ of the, shows the second temperature range T _2, and the third temperature range T _3.

In the first temperature range T ₁ , the reproducing layer 3
The recording layer 4 and the recording layer 4 are strongly coupled via the intermediate layer 9 by magnetic exchange coupling. Therefore, for example, even if the reproducing layer 3 is a single layer, even if it is a minute magnetic domain having a predetermined size (for example, a magnetic domain having a width of 0.4 μm) which cannot be stably present,
The magnetization information of the recording layer 4 is transferred to the reproducing layer 3 by the above magnetic exchange coupling.

In the second temperature range T ₂ , there is no magnetic exchange coupling, and the reproducing layer 3 and the recording layer 4 have a weaker magnetostatic coupling than the magnetic exchange coupling via the intermediate layer 9. Combine only by combining. Therefore, it can be considered that the stability of the minute magnetic domains in the reproducing layer 3 is almost equal to the stability when the reproducing layer 3 is a single layer. Therefore, a minute magnetic domain (for example, a magnetic domain having a width of 0.4 μm) in the reproducing layer 3 cannot exist stably.

In the third temperature range T ₃ , similarly to the _second temperature range T ₂ , the reproducing layer 3 and the recording layer 4 are connected to the intermediate layer 9.
Through the magnetostrictive coupling, which is a coupling weaker than the magnetic exchange coupling. However, as described above, minute magnetic domains (for example, magnetic domains having a width of 0.4 μm) in the reproducing layer 3.
Can be stably present. For this reason, the magnetization information of the recording layer 4 is transferred to the reproducing layer 3 by the above-described magnetostatic coupling that attempts to match the direction of the stray magnetic field generated from the recording layer 4 with the magnetization direction of the reproducing layer 3.

That is, the magneto-optical disk according to the present embodiment has the first temperature range T ₁ and the third temperature range T ₃
While the magnetization information of the recording layer 4 is transferred to the reproducing layer 3 in, it is possible in the second temperature range T ₂ to achieve the phenomenon magnetization information of the recording layer 4 is not transferred to the reproducing layer 3 ing.

(1) Method of Reproducing Magneto-Optical Disk The operation of reproducing the magneto-optical disk will be described with reference to FIG. On the magneto-optical disk, recording magnetic domains 4a... Are formed in the recording layer 4 along the plurality of tracks 1a formed on the substrate 1 in accordance with recording information. FIG. 1A is a plan view (explanatory view) showing a main part of the magneto-optical disk, and FIGS. 2B to 2D show changes over time in the magnetization state in the cross section of the magneto-optical disk in order. FIG. FIG. 13B corresponds to FIG. Arrows in FIGS. 6B to 6D indicate the magnetization state and the stray magnetic field state of each of the layers 3, 4 and 9.

As shown in FIG. 2A, the spot 8a of the light beam 8 also moves relatively (left in the figure) due to the movement (rightward in the figure) of the track 1a accompanying the rotation of the magneto-optical disk. Direction), a temperature distribution corresponding to the moving speed is generated in the track 1a. The portion of the track 1a where the temperature is highest is the spot 8a
Will be located at the rear of the interior. That is, the area inside the isotherm 21 is the third temperature range T ₃ where the temperature is the highest, and the area between the isotherm 21 and the isotherm 22 is the second temperature range T 3.
_{2 and the} area outside the isotherm 22 is the first temperature range T ₁
Becomes

The spot 8a is located at the position shown in FIG.
Is present, the isotherm 2 in the _first temperature range T ₁
Focusing on the recording magnetic domain 4a ₁ located second outer region illustrating the reproduction operation. In the following description, for convenience,
The outer region of the isotherm 22 is a first temperature range T _1, simply referred first temperature range T _1, the region between the isotherms 21 and isotherm 22 is a second temperature range T ₂ , simply referred to as the second temperature range T _2, the inner region of the third temperature range T ₃ in which isotherm 21, simply referred to as a third temperature range T _3.

[0040] When the spot 8a to the position of FIG. (A) is present, the intermediate layer 9 corresponding to the recording magnetic domain 4a ₁ is at a temperature below the Curie point, the intermediate layer and the recording layer 4 and the reproducing layer 3 9 strongly coupled by magnetic exchange coupling. Therefore, the magnetization state of the recording layer 4 is transferred to the reproducing layer 3 by the above magnetic exchange coupling. That is, as shown in FIG. 3B, the magnetization directions of the recording layer 4 and the intermediate layer 9 are different from the magnetization direction of the recording layer 3 so that the directions of the sublattice moments of the layers 3, 4, and 9 match. Is uniquely determined.

Next, the spot 8a relatively moves,
When moving from the position of FIG. (A), the recording magnetic domain 4a ₁ is,
Region between the isotherms 21 and isotherms 22, i.e., as shown in FIG. (C), the position in the second temperature range T _2. In this case, since the intermediate layer 9 corresponding to the recording magnetic domain 4a ₁ is to a temperature above the Curie point, the reproducing layer 3 and the recording layer 4 through the intermediate layer 9, bound only by magnetostatic coupling. Therefore, the magnetization state of the recording layer 4 is not transferred to the reproducing layer 3. That is, the recording information recorded on the recording layer 4 is masked by the reproduction layer 3.

[0042] Next, the spot 8a further moves relatively, the recording magnetic domain 4a ₁ is, as shown in FIG. 2 (d), will be located in the third temperature range T _3. In this case, the intermediate layer 9 corresponding to the recording magnetic domain 4a ₁ is a temperature above the Curie point, and, since fine magnetic domains in the reproducing layer 3 can exist stably, the direction of the stray magnetic field generated from the recording layer 4 The magnetic state of the recording layer 4 is changed by the magnetostatic coupling to make the magnetization direction of the reproducing layer 3 coincide with the magnetization direction of the reproducing layer 3.
Is transferred to That is, the magnetization state of the recording layer 4 is transferred to the reproduction layer 3 such that the magnetization directions of the reproduction layer 3 and the recording layer 4 match.

As described above, the magneto-optical disk according to the present embodiment is located in the first temperature range T ₁ and the third temperature range T ₃ due to the temperature change of the track 1 a caused by the irradiation of the light beam 8. It is possible to perform super-resolution reproduction in which only the magnetization information of the recording magnetic domains 4a is transferred to the reproduction layer 3 and reproduced.

Further, in the present embodiment, when the state shown in FIG. 1B is changed to the state shown in FIG.
That is, when moving the recording magnetic domain 4a is from the first temperature range T ₁ to a second temperature range T ₂ (migration), becomes very small magnetic domains corresponding to the recording magnetic domain 4a in the reproducing layer 3 is unstable At this moment, instantaneous disappearance of magnetic domains (hereinafter referred to as collapse) in the reproducing layer 3 occurs, and a steep fall of the reproduced signal is obtained. Meanwhile, during the transition from the state shown in FIG. 3 (c) to the state shown in FIG. 2 (d), i.e., moving the recording magnetic domain 4a is a second temperature range T ₂ to the third temperature range T ₃ ( At the moment when the minute magnetic domain corresponding to the recording magnetic domain 4a in the reproducing layer 3 becomes stable, the instantaneous generation of the magnetic domain in the reproducing layer 3 (hereinafter, referred to as “transition”).
Nucleation), and a steep rising of the reproduced signal is obtained.

Incidentally, as shown in FIG.
A first temperature range T ₁ and a third temperature range T ₃ also exist behind a. Therefore, the recording magnetic domain 4a becomes the third
Collapse occurs in the reproducing layer 3 when moving from the temperature range T ₃ to the second temperature range T ₂ of the mobile recording magnetic domain 4a is a second temperature range T ₂ to the first temperature range T ₁ When this occurs, nucleation in the reproduction layer 3 occurs. However, the above-mentioned collapse and nucleation occur at positions off the spot 8a. Therefore, there is no influence on the reproduced signal.

(2) Method for Forming a Magneto-Optical Disk A method for forming a magneto-optical disk having the above configuration will be described. For convenience of explanation, a prototype of a magneto-optical disk formed by this method is referred to as a disk A. Further, the configuration of the sputtering apparatus (not shown) is not particularly limited.

First, an Al target, a GdFeCo alloy target, a first DyFeCo alloy target, and a second DyFeCo
A substrate 1 made of polycarbonate and having a pre-groove and pre-pits was disposed on a substrate holder in a sputtering device provided with an alloy target. Then, the inside of the sputtering apparatus is evacuated to a pressure of 1 × 10 ⁻⁶ Torr, a mixed gas of argon and nitrogen is introduced, power is supplied to an Al target, and a gas pressure of 4 × 10 ⁻⁶ Torr is applied.
Under a condition of 10 ⁻³ Torr, a transparent dielectric layer 2 made of AlN was formed on the substrate 1.

Here, the thickness of the transparent dielectric layer 2 is set to a value obtained by dividing 1/4 of the wavelength of the reproduction light by the refractive index of the transparent dielectric layer 2 in order to improve the reproduction characteristics. I just need. For example, when the wavelength of the reproduction light is 680 nm, the thickness of the transparent dielectric layer 2 may be about 10 nm to 80 nm. In the present embodiment, the thickness of the transparent dielectric layer 2 is set to 50 nm.

Next, the inside of the sputtering apparatus is again evacuated to a pressure of 1 × 10 ⁻⁶ Torr, and then argon gas is introduced, power is supplied to the GdFeCo alloy target, and the gas pressure is reduced to 4 × 10 ⁻⁶ Torr.
Under the condition of × 10 ⁻³ Torr, Gd is formed on the transparent dielectric layer 2.
_A reproducing layer 3 made of _0.20 (Fe _0.60 Co _0.40 ) _0.80 was formed.
The reproducing layer 3 had a compensation temperature at about room temperature, and its Curie point was 460 ° C.

The thickness of the reproducing layer 3 is 10 nm or more because it is necessary to prevent the magnetization information recorded on the recording layer 4 from passing through the reproducing layer 3 and appearing as a signal output to some extent. It is desirable. On the other hand, if the thickness of the reproducing layer 3 is too large, the power of the light beam 8 necessary for increasing the temperature increases, which causes a decrease in recording sensitivity. For this reason, the thickness of the reproducing layer 3 is desirably 100 nm or less. In the present embodiment, the thickness of the reproducing layer 3 is set to 40 nm.

Next, power is supplied to the first DyFeCo alloy target, and Dy _0.20 (Fe _0.90 Co _0.10 ) _{0.80 is formed} on the reproducing layer 3 under the conditions of a gas pressure of 4 × 10 ⁻³ Torr. Middle layer 9
Was formed. The intermediate layer 9 had a compensation temperature at about room temperature, and its Curie point was 70 ° C.

The intermediate layer 9 magnetically couples the reproducing layer 3 and the recording layer 4 at a temperature lower than the Curie point, while the magnetic layer between the reproducing layer 3 and the recording layer 4 at a temperature higher than the Curie point. It is necessary to cut off the exchange coupling. Therefore, the thickness of the intermediate layer 9 needs to be larger than 1 nm. Furthermore, the floating magnetic field 9a generated from the recording layer 4 needs to be magnetostatically coupled to the magnetization of the reproducing layer 3 at a temperature equal to or higher than the Curie point of the intermediate layer 9. For this reason, the thickness of the intermediate layer 9 is desirably 50 nm or less. In the present embodiment, the thickness of the intermediate layer 9 is set to 10 nm.

Next, power is supplied to the second DyFeCo alloy target, and Dy _0.23 (Fe _0.70 Co _0.30 ) _{0.77 is formed} on the intermediate layer 9 under the conditions of a gas pressure of 4 × 10 ⁻³ Torr. Recording layer 4
Was formed. The recording layer 4 was a perpendicular magnetization film having a compensation temperature at about room temperature, and its Curie point was 275 ° C.

In the third temperature range, the thickness of the recording layer 4 is determined by the stray magnetic field 9 necessary for reversing the magnetization of the reproducing magnetic domain of the reproducing layer 3.
Since it is necessary to generate a, it is desirable that the thickness be 20 nm or more. If the thickness of the recording layer 4 is too large,
The power of the light beam 8 necessary for increasing the temperature is increased, which causes a reduction in recording sensitivity. Therefore, the recording layer 4
Is desirably 200 nm or less. In the present embodiment, the thickness of the recording layer 4 is set to 40 nm.

Next, a mixed gas of argon and nitrogen was introduced into the sputtering apparatus, and power was supplied to the Al target.
Under the same conditions as when the transparent dielectric layer 2 was formed, a protective layer 5 made of AlN was formed on the recording layer 4.

Here, the film thickness of the protective layer 5 is only required to be able to protect the magnetic layer such as the recording layer 4 from corrosion such as oxidation, and is desirably 5 nm or more. In the present embodiment, the thickness of the protective layer 5 is set to 20 nm.

Next, an ultraviolet curable resin is applied on the protective layer 5 by spin coating and irradiated with ultraviolet rays, or a thermosetting resin is applied by spin coating and heated to form an overcoat layer 6. Was formed. Thus, a magneto-optical disk, that is, a disk A was formed.

(3) Recording / reproduction characteristics of disk A Recording / reproduction was performed on the disk A, and the characteristics were examined. That is, the mark length dependence of the signal-to-noise ratio (hereinafter, referred to as CNR) on the disk A was measured.

That is, first, after initializing the magnetization direction of the recording layer 4, the linear velocity is set to 5 m / s, the recording magnetic field is set to 10 kA / m, and 6 mW
By irradiating a pulse of the light beam 8 having a power of, a group of recording bits having different mark lengths (diameters) can be set to the mark length of 2 mm.
The recording layer 4 was formed at a double mark pitch. Then, 2mW
CNR was measured at the reproduction laser power of The results are shown in the graph of FIG. As can be seen from the figure, in the recording bit group of the disc A formed with a mark length of 0.3 μm and a mark pitch of 0.6 μm, a CNR of 35 dB or more is obtained.

In the measurement of CNR according to the present invention, the wavelength 8
An optical system using a 30 nm semiconductor laser is used. Therefore, for comparison, a CNR mark on a magneto-optical disk (hereinafter, referred to as a comparative disk), which is a general magneto-optical recording medium using no magnetic super-resolution phenomenon, using the above-described optical system. Length dependence was measured under the same conditions.
The results are graphically shown in the figure. As can be seen from the figure, in the recording bit group of the comparative disk formed with a mark length of 0.3 μm and a mark pitch of 0.6 μm, the CNR
Is zero. That is, in the recording bit group, it is understood that the recording bit to be reproduced and the recording bit adjacent thereto cannot be separated at all.

On the other hand, in the configuration of the present embodiment, a large CNR is obtained when reproduction is performed using a semiconductor laser having a wavelength of 830 nm. From this, it can be seen that in the disk A, the magnetic super-resolution phenomenon occurs during the reproduction.

For the disk A and the comparative disk, the dependence of the CNR on the reproducing power in the recording bit group formed with a mark length of 0.55 μm and a mark pitch of 1.1 μm, that is, the magnetic domain, was measured. The results are shown in the graph of FIG. As can be seen from the figure, in the magnetic domain of the disk A, when the reproducing power of the light beam 8 is about 1.5 mW,
That is, it can be seen that the CNR sharply increases at about 1.5 mW. This is shown in FIG.
This is because a temperature distribution of the reproducing layer 3 as shown in FIG. 3A occurs, and nucleation and collapse of the reproducing magnetic domain occur in the reproducing layer 3.

When the reproducing power is further increased, about 2.5
It can be seen that the CNR sharply decreases starting from mW.
This is because the temperature rise occurs in a wider range in the reproducing layer 3 as the reproducing power increases, and the temperature distribution of the reproducing layer 3 as shown in FIG. On the other hand, in the magnetic domain of the comparative disk, almost no change in the CNR with respect to the reproducing power was observed.

Therefore, the reproduction power of the light beam 8 for the magneto-optical disk of the present embodiment is set to be higher than the power capable of nucleation and collapse of the reproduction magnetic domain (reversal magnetic domain). By setting the reproduction power in this way, a good signal can be reproduced.

(4) Reproduction Waveform of Disk A Reproduction was performed on the disk A, and the reproduction waveform was measured. That is, as shown in FIG. 6, a recording magnetic domain 4 having a mark length (diameter) of 0.6 μm is formed on a track 1 a having a width of 0.9 μm.
are formed at various mark pitches, and the reproduced waveforms obtained by reproducing the tracks 1a are measured. The mark pitch of the recording magnetic domains 4a shown in FIG.
The mark pitch of the recording magnetic domains 4a shown in FIG. 6B is 1.9 μm, and the recording magnetic domains 4a shown in FIG.
Is 1.6 .mu.m, the mark pitch of the recording magnetic domains 4a shown in FIG. 4D is 1.3 .mu.m, and the mark pitch of the recording magnetic domains 4a shown in FIG.
It is. The obtained reproduced waveform is shown in FIG. 9 in the above order (the order of FIG. 6).

When the mark pitch is 1.6 μm or more,
That is, when the adjacent recording magnetic domains 4a are sufficiently separated from each other, first, as shown in FIGS.
When incoming recording magnetic domain 4a in spots 8a, while being located in the first temperature range T _1, the intensity of the reproduced signal gradually increases (in the drawing).

Next, the recording magnetic domain 4a is set in the second temperature range T ₂
, A collapse occurs in the reproduction layer 3, and a sharp fall in the intensity of the reproduction signal occurs (see FIG. 3). Next, the recording magnetic domain 4a is shifted to the second temperature range T
_While located at ₂ , no playback signal is generated and a constant level (intensity) is maintained (as shown). In this state, for example, when the thickness of the reproducing layer 3 is as thin as about 20 nm,
The light beam 8 transmits through the reproducing layer 3 and detects the recorded information on the recording layer 4. Therefore, the level of the reproduced signal in the portion where the collapse occurs may be slightly higher than the level of the reproduced signal in the portion where the recording magnetic domain 4a does not exist.

Next, the recording magnetic domain 4a is set in the third temperature range T ₃
, Nucleation occurs in the reproducing layer 3, and a sharp rise in the intensity of the reproduced signal occurs in the nucleation (in the figure). Next, when the recording magnetic domain 4a comes out of the spot 8a, the intensity of the reproduction signal gradually decreases (in the figure) and becomes the level of the reproduction signal in the portion where the recording magnetic domain 4a does not exist (in the figure). When the next recording magnetic domain 4a enters the spot 8a, the intensity of the reproduction signal is repeatedly increased and decreased to form a reproduction waveform.

If the mark pitch is less than 1.6 μm (1.3 μm or less in the example of FIG. 6), that is, if the adjacent recording magnetic domains 4a are not sufficiently separated, a plurality of recording magnetic domains are included in the spot 8a. 4a ... enters. Therefore, as shown in FIGS. 7D and 7E, a certain recording magnetic domain 4
a changes from the spot 8a (that is, decreases) due to the intensity of the reproduced signal, and changes in the intensity of the next recorded magnetic domain 4a.
And a change (that is, an increase) in the intensity of the reproduction signal caused by entering the spot 8a. Therefore, the level of the reproduced signal in a portion where the recording magnetic domain 4a does not exist becomes higher than the level when the adjacent recording magnetic domains 4a are sufficiently separated (FIGS. 7A to 7C). Finally, a rectangular reproduction waveform (FIG. 7E) is formed.

As described above, the magneto-optical disk according to the present embodiment has a characteristic that the obtained reproduction waveform differs depending on the length of the mark pitch. However, the collapse and nucleation in the reproduction layer 3 are as follows.
It always occurs in the same positional relationship relative to the spot 8a. That is, the sharp fall and rise of the intensity of the reproduction signal are not affected by the length of the mark pitch,
It always occurs at the same position in the spot 8a. Therefore, the edge position of the recording magnetic domains 4a can be accurately detected by detecting the steep falling and rising of the intensity of the reproduction signal, so that the magnetization information recorded on the recording layer 4 can be reproduced with high accuracy. can do.

As shown in FIGS. 8A to 8E,
Recording magnetic domains 4a of various mark lengths were formed at a mark pitch of 2.2 μm on a track 1a having a width of 0.9 μm, and a reproduction waveform obtained by reproducing these tracks 1a was measured.
The mark length of the recording magnetic domains 4a shown in FIG.
The mark length of the recording magnetic domains 4a shown in FIG.
The mark length of the recording magnetic domains 4a shown in FIG. 6C is 0.5 .mu.m, and the recording magnetic domains 4a shown in FIG.
The mark length of a ... is 0.4 .mu.m, and the mark length of the recording magnetic domains 4a shown in FIG. Further, as shown in FIG. 6F, a track 1a having a width of 0.9 μm is
Recorded magnetic domains 4a having different mark lengths were formed at a mark pitch of 1.0 μm, and a reproduced waveform obtained by reproducing the track 1a was measured. The obtained reproduced waveform is shown in FIG. 9 in the above order (the order of FIG. 8).

The tracks 1a shown in FIGS.
Since the pattern of the reproduced waveform (FIGS. 9A to 9E) obtained by reproducing the pattern has a mark pitch of 2.2 μm, the pattern of the reproduced waveform shown in FIGS. It is almost equal. In this case, the stability of the recording magnetic domain 4a differs depending on the size (mark length) of the recording magnetic domain 4a. That is, in order to completely block magnetic exchange coupling between the reproducing layer 3 and the recording layer 4, it is necessary to increase the temperature of the track 1a over a wider range as the diameter of the recording magnetic domain 4a is larger. Therefore, the occurrence of the collapse in the reproduction layer 3 moves to the rear part in the spot 8a, and as apparent from FIGS. 9A to 9E, the sharp fall of the intensity of the reproduction signal does not occur. Will occur later. Conversely, as the diameter of the recording magnetic domain 4a is smaller, the collapse of the reproducing layer 3 occurs only by increasing the temperature of the track 1a in a narrower range. Therefore, since the occurrence of the collapse moves to the front in the spot 8a, the sharp fall of the intensity of the reproduction signal occurs earlier.

Further, as the diameter of the recording magnetic domain 4a is larger,
The magnetic domain corresponding to the recording magnetic domain 4a in the reproducing layer 3 becomes more stable, and the floating magnetic field generated from the recording magnetic domain 4a increases. Therefore, the occurrence of nucleation in the reproduction layer 3 moves to the front part in the spot 8a, and as shown in FIGS. 9A to 9E, the intensity of the reproduction signal sharply rises. Will occur earlier. Conversely, the smaller the diameter of the recording magnetic domain 4a, the more unstable the magnetic domain corresponding to the recording magnetic domain 4a in the reproducing layer 3 and the weaker the stray magnetic field generated from the recording magnetic domain 4a. Therefore, since the occurrence of the nucleation moves to the rear portion in the spot 8a, the steep rise of the intensity of the reproduced signal occurs later.

In this embodiment, the sharp fall of the intensity of the reproduced signal due to the collapse and the sharp rise of the intensity of the reproduced signal due to the nucleation are detected with high accuracy. Then, as shown in FIG. 9 (a) ~ (e), the mark length is 0.7μm recording magnetic domain 4a ... With time (length) reproduction signal a ₁ is detected, the mark length is 0.
For the 6 μm recording magnetic domains 4 a, a reproduced signal of time b ₁ is detected, for the recording magnetic domains 4 a, having a mark length of 0.5 μm, a reproduced signal of time c ₁ is detected, and for the mark length of 0.4 μm.
μm recording magnetic domain 4a ... For the detected reproduction signal time d _1, so that the reproduced signal in the time e ₁ is detected mark length is the recording magnetic domain 4a of 0.3 [mu] m .... Therefore, a reproduced signal for a shorter time is detected for the larger recording magnetic domains 4a.

The pattern of the reproduced waveform (FIG. 9 (f)) obtained by reproducing the tracks 1a shown in FIG. 8 (f) has a small mark pitch of 1.0 μm. It becomes almost equal to the waveform pattern, and thus a rectangular reproduced waveform is formed. In this case, the position of the sharp fall (in FIG. 9) of the intensity of the reproduced signal and the position of the sharp rise (in FIG. 9) of the intensity of the reproduced signal depend on the size of the recording magnetic domains 4a. Therefore, the recording domain 4
It is possible to detect the reproduced signal at time a ₁ to time e ₁ corresponding to the magnitude of a.

As described above, in the recording / reproducing method according to the present embodiment, a reproduction signal of a shorter time is detected for a larger recording magnetic domain 4a, while a reproducing signal for a smaller recording magnetic domain 4a is detected. , A reproduced signal for a longer time is detected. Therefore, the size of the recording magnetic domains 4a can be accurately determined by measuring the length of the reproduction signal.

Next, the width of the track 1a is increased from 0.9 μm.
Recording magnetic domains 4a of various mark lengths were formed at a mark pitch of 2.2 μm in the same manner as described above, except that the track pitch was changed to 0.7 μm, and the reproduced waveform obtained by reproducing these tracks 1a was measured. The obtained reproduced waveforms are shown in FIGS.
(E) shows the above order (the order of FIG. 8). Note that FIG.
(F) will be described later.

The mark length is 0.6 μm, 0.5 μm, 0.4 μm
Track 1 on which recording magnetic domains 4a of m, 0.3 μm are formed.
a... are reproduced (FIG. 10B)
The pattern of (e)) is the same as the reproduced waveform pattern shown in FIGS. 9B to 9E, and thus a good reproduced signal was obtained. However, a reproduction waveform obtained by reproducing the track 1a on which the recording magnetic domains 4a having the mark length (0.7 μm) equal to the width of the track 1a are formed (FIG. 10A).
In the pattern (1), there is a portion (in the figure) in which a sharp fall of the intensity of the reproduced signal due to the collapse and a sharp rise of the intensity of the reproduced signal due to the nucleation are not recognized. This is because the state of the peripheral portion of the recording magnetic domain 4a that is in contact with the edge of the track 1a slightly differs depending on each recording magnetic domain 4a. This is because the stability is different. Thus, when the mark length of the recording magnetic domains 4a is equal to the width of the track 1a,
Since a good reproduction signal may not be obtained, in the magneto-optical disk according to the present embodiment, the mark length of the recording magnetic domains 4a is set so that the peripheral edge of the recording magnetic domains 4a does not contact the edge of the track 1a. Is preferably smaller than the width of the track 1a.

That is, it is desirable that the width of the recording magnetic domain 4a, which is a recorded portion, is smaller than the width of the track 1a, which is an unrecorded portion. As a result, the intensity of the floating magnetic field generated from the unrecorded portion becomes stronger than the intensity of the floating magnetic field generated from the recorded portion.
It can be stably directed to the magnetization direction of the stray magnetic field generated from the unrecorded portion in the recording layer 4. Therefore, an even better stable reproduction signal can be obtained.

However, even when the mark length of the recording magnetic domains 4a is equal to the width of the track 1a, a good reproduction signal can be obtained by irradiating a reproducing light beam and applying a reproducing magnetic field (external magnetic field). Obtainable. That is,
As shown in FIG. 11, by irradiating the disk body 10 with the light beam 8 and applying the reproducing magnetic field 11 as an external magnetic field by the magnetic field generating mechanism 12, the recording magnetic domain 4
A good reproduction signal can be obtained even when the mark length of a ... is equal to the width of the track 1a. Here, a case where no collapse and no nucleation occur in the reproduction layer 3 will be considered. As shown in the figure, in the case where the collapse and New Creation is not generated, the reproducing layer 3 at a position corresponding to the recording magnetic domain 4a ₂ located in the second temperature range T _2, there is reversed magnetic domain 3a ₂ . That is, the magnetization direction of the readout layer 3 located in the second temperature range T ₂ is, so that does not match the magnetization direction of the stray magnetic field generated from the unrecorded portion of the recording layer 4. Therefore,
By applying the reproducing magnetic field 11 in a direction corresponding to the magnetization direction of the stray magnetic field generated from the unrecorded portion of the recording layer 4, the magnetization direction of the reproducing layer 3 located in the _second temperature range T2 is stabilized. Thereby, the magnetization direction of the reproducing layer 3 is changed to
The magnetization direction of the stray magnetic field generated from the unrecorded portion of the recording layer 4 can be matched.

While applying the reproducing magnetic field 11, the track 1
The reproduced waveform obtained by reproducing the track 1a on which the recording magnetic domains 4a... having the mark length equal to the width of a are formed is shown in FIG.
(F). That is, the track 1a has the reproducing magnetic field 11
When the reproduction is performed without applying the reproduction magnetic field 11, the reproduction waveform pattern shown in FIG. 5A is shown. When the reproduction is performed while the reproduction magnetic field 11 is applied, the reproduction waveform pattern shown in FIG. . As is apparent from FIG. 11F, collapse and nucleation are stably generated in the reproducing layer 3, and a good reproduced signal can be obtained. still,
When the reproducing magnetic field 11 is applied, the reproducing layer 3 is in a state where the collapse is more likely to occur. Therefore, the length of the reproduced signal for the recording magnetic domains 4a, that is, the time a ₁ ′ from the sharp fall of the intensity of the reproduced signal due to the collapse to the sharp rise of the intensity of the reproduced signal due to the nucleation.
Is longer than the time a ₁ when not applied reproducing magnetic field 11. However, by applying the reproducing magnetic field 11, the length of the reproducing signal becomes longer in all the recording magnetic domains 4a..., So that a good reproducing signal can be obtained with the reproducing magnetic field 11 applied.

When the magnetic field generating mechanism 12 is used, by sharing the magnetic field generating mechanism 12 and the means for generating a recording magnetic field, it is not necessary to newly provide the magnetic field generating mechanism 12, so that the light It is possible to reduce the size of the magnetic recording / reproducing device and reduce the manufacturing cost.

(5) Relationship between Film Thickness of Disk A and Reproduction Characteristics Next, in the disk A, the film thicknesses of the reproduction layer 3, the intermediate layer 9, and the recording layer 4 were variously changed to obtain a mark length of 0.3 μm,
The CNR in each of the recording magnetic domains (recording bits) 4a... Set at a mark pitch of 0.6 μm was measured, and the reproduction characteristics were examined. That is, the relationship between the thickness of each of the layers 3, 4, and 9 of the disk A and the reproduction characteristics was examined. Table 1 shows the results. Incidentally, for the magneto-optical disk from which a reproduced waveform having the same shape as the reproduced waveform shown in FIG. 7 was obtained, the column of the reproduction characteristic in Table 1 was indicated by a circle.

[0084]

[Table 1]

In the above CNR measurement, the wavelength of 830 nm
An optical system using a semiconductor laser is used. Therefore, a certain CNR is obtained for the recording magnetic domains 4a formed with the mark length of 0.3 μm and the mark pitch of 0.6 μm, as described above, in the configuration of the present embodiment, It means that the phenomenon is manifested. As is clear from Table 1, the thickness of the intermediate layer 9 is 1 nm.
In other words, the magnetic super-resolution phenomenon was not observed when the film thickness was extremely small, but the magnetic super-resolution phenomenon was observed when the film thickness was investigated. In the configuration of the present embodiment, it is necessary to cut off magnetic exchange coupling between the reproducing layer 3 and the recording layer 4 in the second temperature range T ₂ and the third temperature range T ₃ . When the thickness of the intermediate layer 9 is extremely small, the magnetic exchange coupling cannot be sufficiently blocked. Therefore, when the thickness of the intermediate layer 9 is extremely small, the magnetization state of the recording layer 4 is transferred to the reproducing layer 3 by magnetic exchange coupling, and the magnetic super-resolution phenomenon does not appear.

Next, in the disk A, the composition of the reproducing layer 3 was variously changed so that the mark length was 0.3 μm, the mark pitch was
The CNR in each of the recording magnetic domains 4a... Set at 0.6 μm was measured in the same manner as described above, and the reproduction characteristics were investigated. Table 2 shows the results. In Table 2, X ₁ and Y ₁
Means the molar ratio of the reproducing layer 3 in the composition formula Gd _X1 (Fe _Y1 Co _1-Y1 ) _1-X1 . Further, in the magneto-optical disk from which a reproduced waveform having the same shape as the reproduced waveform shown in FIG. 7 was obtained, the column of the reproduction characteristic in Table 2 was indicated by a circle.

[0087]

[Table 2]

As is apparent from Table 2, in the structure of the present embodiment, of the molar ratio in the composition formula Gd _X1 (Fe _Y1 Co ₁ -Y ₁ ) _{1 -X 1} of the reproducing layer 3, Y ₁ is 0.60. case, X ₁ is, it can be seen that it is necessary to satisfy the relationship of at least 0.16 ≦ X ₁ ≦ 0.22. When X ₁ is smaller than 0.16, since small magnetic domains of the reproducing layer 3 in the second temperature range T ₂ is present in a stable, it does not occur and a new creation and collapse of the reproduction magnetic domains described above. Further, when X ₁ is greater than 0.22, since small magnetic domains of the reproducing layer 3 becomes unstable in the third temperature range T _3, the temperature range T ₃ of the third
In this case, the magnetic domain transfer to the reproducing layer 3 does not occur, and the nucleation of the reproducing magnetic domain described above does not occur.

In the structure of the present embodiment, the reproducing layer 3
Of the molar ratio in the composition formula Gd _X1 (Fe _Y1 Co _1-Y1 ) _1-X1 ,
_{When 1} is 0.20, Y ₁ is at least 0.48 ≦ Y ₁ ≦
It is understood that the relationship of 0.75 needs to be satisfied. Y ₁
If it is smaller than 0.48, the content of Co increases and the change in the magnetization state of the reproduction layer 3 increases, so that it becomes difficult to develop a perpendicular magnetization state in the reproduction layer 3. Also,
When Y ₁ is greater than 0.75, it reduces the content of Co,
Since the Curie point of the reproducing layer 3 becomes lower, the magnetic domain transfer to the reproducing layer 3 in the third temperature range T ₃ does not occur,
The nucleation of the reproduction magnetic domain described above does not occur.

Next, in the disk A, the composition of the recording layer 4 was variously changed so that the mark length was 0.3 μm, the mark pitch was
The CNR in each of the recording magnetic domains 4a... Set at 0.6 μm was measured in the same manner as described above, and the reproduction characteristics were investigated. Table 3 shows the results. In Table 3, X ₂ and Y ₂
Indicates the molar ratio of the recording layer 4 in the composition formula Dy _X2 (Fe _Y2 Co _{1 -Y2} ) _{1 -X2} . Further, for the magneto-optical disk from which a reproduced waveform having the same shape as the reproduced waveform shown in FIG. 7 was obtained, the column of the reproduction characteristic in Table 3 was indicated by a circle.

[0091]

[Table 3]

As is clear from Table 3, in the structure of the present embodiment, of the molar ratio in the composition formula Dy _X2 (Fe _Y2 Co ₁ -Y ₂ ) ₁ -X ₂ of the recording layer 4, Y ₂ is 0.70. in this case, X ₂ is, it can be seen that it is necessary to satisfy the relationship of at least 0.15 ≦ X ₂ ≦ 0.25. When X ₂ is smaller than 0.15, the coercive force of the recording layer 4 is significantly reduced in the third temperature range T ₃ , so that it is difficult to maintain recorded information. Also, X
If ₂ is greater than 0.25, the compensation temperature with Curie point of the recording layer 4 is lowered is increased, and, since the stray magnetic field generated from the recording layer 4 in the third temperature range T ₃ becomes smaller, third of no longer occur domain transfer to the reproducing layer 3 in the temperature range T _3, it does not occur and New creation of reproducing the magnetic domain as described above.

In the structure of the present embodiment, the recording layer 4
Of the molar ratio in the composition formula Dy _X2 (Fe _Y2 Co _1-Y2 ) _1-X2 , X
_{When 2} is 0.23, Y ₂ is at least 0.66 ≦ Y ₂ ≦
It is understood that the relationship of 0.80 needs to be satisfied.

[Second Embodiment] The following will describe another embodiment of the present invention with reference to FIGS. For convenience of explanation, the first embodiment is described.
Components having the same functions as those shown in the drawings of the drawings are denoted by the same reference numerals, and description thereof will be omitted.

The magneto-optical disk of this embodiment is similar to that of FIG.
As shown in FIG. 7, a disk main body 20 having an intermediate layer 19 made of an in-plane magnetized film is provided in place of the intermediate layer 9 of the first embodiment. The other configuration of the magneto-optical disk is the same as that of the magneto-optical disk of the first embodiment.

The intermediate layer 19 made of the in-plane magnetic film weakens the magnetic exchange coupling acting between the reproducing layer 3 and the recording layer 4 as compared with the intermediate layer 9 made of the perpendicular magnetic film. However, by setting the thickness of the intermediate layer 19 to an appropriate value, a very strong magnetic exchange coupling can be made to act between the reproducing layer 3 and the recording layer 4 as compared with the magnetostatic coupling. Therefore, by setting the Curie point of the intermediate layer 19 to a temperature lower than the Curie point of the reproducing layer 3 and the Curie point of the recording layer 4, super-resolution reproduction is possible.

(1) Method of Reproducing Magneto-Optical Disk The operation of reproducing the magneto-optical disk will be described with reference to FIG. However, the description of the same reproducing operation as that of the magneto-optical disk of the first embodiment will be simplified. FIG. 1A is a plan view (explanatory view) showing a main part of the magneto-optical disk, and FIGS. 2B to 2D show changes over time in the magnetization state in the cross section of the magneto-optical disk in order. FIG. FIG. 13B corresponds to FIG. Arrows in FIGS. 3B to 3D show the state of magnetization and the state of a stray magnetic field of each of the layers 3, 4, and 19.

As shown in FIG. 9A, a temperature distribution corresponding to the moving speed occurs in the track 1a. Here, when the spot 8a exists at the position shown in FIG.
Focusing on the recording magnetic domain 4a ₁ illustrating the playback operation located in the temperature range T _1.

[0099] When the spot 8a is present at the position of FIG. (A) Since the intermediate layer 19 corresponding to the recording magnetic domain 4a ₁ is at a temperature below the Curie point, as shown in FIG. (B), reproduction The layer 3 and the recording layer 4 are strongly coupled via the intermediate layer 19 by magnetic exchange coupling. Therefore, the recording layer 4
Of the reproducing layer 3 by the magnetic exchange coupling described above.
Is transferred to

Next, when the spot 8a moves from the position shown in FIG. 7A, the recording magnetic domain 4a ₁ is located in the _second temperature range T2 as shown in FIG. . In this case, since the intermediate layer 19 corresponding to the recording magnetic domain 4a ₁ is to a temperature above the Curie point, the reproducing layer 3 and the recording layer 4 through the intermediate layer 19, bound only by magnetostatic coupling.
Therefore, the magnetization state of the recording layer 4 is not transferred to the reproducing layer 3.

[0102] Next, spots 8a is the relatively moves further, the recording magnetic domain 4a ₁ is, as shown in FIG. 2 (d), will be located in the third temperature range T _3. In this case, the intermediate layer 19 corresponding to the recording magnetic domain 4a ₁ is a temperature above the Curie point, and, since fine magnetic domains in the reproducing layer 3 can exist stably, the direction of the stray magnetic field generated from the recording layer 4 Then, the magnetization state of the recording layer 4 is transferred to the reproducing layer 3 by magnetostatic coupling that attempts to match the magnetization direction of the reproducing layer 3 with the reproducing layer 3.

As described above, the magneto-optical disk according to the present embodiment is located in the first temperature range T ₁ and the third temperature range T ₃ due to the temperature change of the track 1 a caused by the irradiation of the light beam 8. It is possible to perform super-resolution reproduction in which only the magnetization information of the recording magnetic domains 4a is transferred to the reproduction layer 3 and reproduced. Further, in the present embodiment, a reproduced signal having a sharp falling edge associated with the collapse and a sharp rising edge associated with the nucleation is obtained.

(2) Method for Forming a Magneto-Optical Disk A method for forming a magneto-optical disk having the above configuration will be described. However, description of the same parts (same method and procedure) as the method of forming the magneto-optical disk of the first embodiment will be omitted. For convenience of explanation, a prototype of a magneto-optical disk formed by this method is referred to as a disk B. Further, the configuration of the sputtering apparatus (not shown) is not particularly limited.

First, the substrate 1 was placed on a substrate holder in a sputtering apparatus provided with an Al target, a GdFeCo alloy target, a GdFe alloy target, and a second DyFeCo alloy target. Then, a transparent dielectric layer 2 made of AlN and having a thickness of 50 nm is formed on the substrate 1, and the transparent dielectric layer 2 made of Gd _0.20 (Fe _0.80 Co _0.20 ) _0.80 is formed on the transparent dielectric layer 2.
A reproducing layer 3 of nm was formed.

Next, electric power was supplied to the GdFe alloy target, and an intermediate layer 19 made of Gd _0.09 Fe _0.91 was formed on the reproducing layer 3 under the conditions of a gas pressure of 4 × 10 ⁻³ Torr. The intermediate layer 19 was an in-plane magnetized film having a Curie point of 70 ° C. and having magnetization in an in-plane (film plane) direction within a temperature range from room temperature to the Curie point.

The intermediate layer 19 magnetically couples the reproducing layer 3 and the recording layer 4 at a temperature lower than the Curie point, while at a temperature higher than the Curie point, the reproducing layer 3
It is necessary to interrupt magnetic exchange coupling between the magnetic recording medium and the recording layer 4.
Therefore, the thickness of the intermediate layer 19 needs to be larger than 1 nm. If the thickness of the intermediate layer 19 is 1 nm or less, the magnetic exchange coupling cannot be completely cut off at a temperature higher than the Curie point. Furthermore, the floating magnetic field 19a generated from the recording layer 4 needs to be magnetostatically coupled to the magnetization of the reproducing layer 3 at a temperature not lower than the Curie point of the intermediate layer 19. Therefore, the thickness of the intermediate layer 19 is desirably 50 nm or less. When the thickness of the intermediate layer 19 exceeds 50 nm, the magnetic exchange coupling is weakened at a temperature lower than the Curie point, and the magnetization state of the recording layer 4 is not transferred to the reproducing layer 3. In the present embodiment, the thickness of the intermediate layer 19 is
It was set to 10 nm.

Next, on the intermediate layer 19, Dy _0.23 (Fe
A recording layer 4 made of _0.70 Co _0.30 ) _0.77 and having a thickness of 40 nm is formed, and a protective layer 5 made of AlN and having a thickness of 20 nm is formed on the recording layer 4.
Was formed, and an overcoat layer 6 was formed on the protective layer 5. Thus, a magneto-optical disk, that is, a disk B was formed.

(3) Recording / Reproduction Characteristics of Disk B Recording / reproduction was performed on the disk B, and the characteristics were examined. That is, the mark length dependence of the CNR in the disk B was measured under the same conditions as in the first embodiment.

As a result, the mark length dependency of the CNR on the disc B showed almost the same tendency as the mark length dependency of the CNR on the disc A of the first embodiment.
This is presumably because both the disc A and the disc B use the reproducing layer 3 and the recording layer 4 having the same characteristics. When reproduction was performed on the disk B and the reproduction waveform was measured, a pattern similar to the reproduction waveform of the disk A was obtained.

(4) Relationship between Film Thickness of Disc B and Reproducing Characteristics Next, in the disc B, the film thicknesses of the reproducing layer 3, the intermediate layer 19, and the recording layer 4 were variously changed to obtain a mark length of 0.3 μm.
m, recording magnetic domain 4a set at a mark pitch of 0.6 μm ...
Were measured, and the regeneration characteristics were investigated. That is, the film thickness of each layer 3, 4, 19 of the disc B,
The relationship with the reproduction characteristics was investigated in the same manner as in the first embodiment. Table 4 shows the results.

[0111]

[Table 4]

In the above CNR measurement, the wavelength of 830 nm
An optical system using a semiconductor laser is used. Therefore, a certain CNR is obtained for the recording magnetic domains 4a formed with the mark length of 0.3 μm and the mark pitch of 0.6 μm, as described above, in the configuration of the present embodiment, It means that the phenomenon is manifested. As is apparent from Table 4, the thickness of the intermediate layer 19 is 1
In the case of nm, that is, when the film was extremely thin, the magnetic super-resolution phenomenon was not recognized, but in the case of the other film thickness examined, the magnetic super-resolution phenomenon was recognized.

Next, in the disk B, an intermediate layer 19 was formed using a GdFeCo alloy target for the intermediate layer instead of the GdFe alloy target, and the composition of the intermediate layer 19 was variously changed to obtain a mark length of 0.3 μm. The CNR in the recording magnetic domains 4a... Set at a mark pitch of 0.6 μm was measured in the same manner as described above, and the reproduction characteristics were examined. Table 5 shows the results. In Table 5, X ₃ and Y ₃ indicate the molar ratio of the intermediate layer 19 in the composition formula Gd _X3 (Fe _Y3 Co _{1 -Y3} ) _{1 -X3} .

[0114]

[Table 5]

As is clear from Table 5, in the configuration of the present embodiment, the composition formula Gd _X3 (Fe _Y3 Co _1-Y3 ) _1-X3 of the intermediate layer 19 is used.
Of the molar ratio in the case Y ₃ is 0.95, X ₃ is seen that it is necessary to satisfy the relationship of at least 0 ≦ X ₃ ≦ 0.12. When X ₃ is greater than 0.12, the intermediate layer 1
Since the Curie point of No. 9 becomes higher, it is difficult to set the Curie point to a temperature lower than the Curie point of the reproducing layer 3 or the Curie point of the recording layer 4. Therefore, it is difficult to exhibit the second temperature range T ₂ , so that the nucleation and collapse of the reproduction magnetic domain described above do not occur.

In the structure of the present embodiment, the intermediate layer 1
Among the molar ratios in the composition formula Gd _X3 (Fe _Y3 Co _1-Y3 ) _1-X3 of 9,
When X ₃ is 0.09, Y ₃ is at least 0.83 ≦ Y ₃
It is understood that it is necessary to satisfy the relationship of ≦ 1. Y ₃
If it is smaller than 0.83, the content of Co increases and the intermediate layer 1
The Curie point of 9 increases. Therefore, the second temperature range T
_Since it becomes difficult to express ₂ , the nucleation and collapse of the reproduction magnetic domain described above do not occur.

In the first and second embodiments,
Although the case where AlN is used as the transparent dielectric layer 2 has been exemplified,
As the transparent dielectric layer 2, for example, a transparent dielectric such as SiN, MgO, SiO, or TaO can be used. However, since the thin film of the rare-earth transition metal alloy constituting the reproducing layer 3 and the recording layer 4 is easily oxidized, it is desirable to use AlN or SiN that does not contain oxygen for the transparent dielectric layer 2.

In the first and second embodiments, the case where a GdFeCo alloy is used as the reproducing layer 3 is exemplified. Can also be used. In short, the reproducing layer 3 is oriented in a direction whose magnetization is determined by magnetic exchange coupling from the recording layer 4 in the first temperature range T ₁ , and the collapse of the transferred magnetic domain in the _second temperature range T ₂ . Is generated, and in a third temperature range T ₃ , the magnetization may be made of a rare-earth transition metal alloy oriented in the direction of the stray magnetic field generated from the recording layer 4.

Further, in the first and second embodiments, the case where the DyFeCo alloy, the GdFe alloy, and the GdFeCo alloy are used as the intermediate layers 9 and 19 has been exemplified.
9, for example, GdDyFe alloy, GdDyFeCo alloy, TbDyFe
It is also possible to use a thin film of a rare earth transition metal alloy such as an alloy or a TbDyFeCo alloy, that is, a magnetic film. In short, the intermediate layers 9 and 19 have magnetization in the first temperature range T ₁ to magnetically exchange-couple the reproducing layer 3 and the recording layer 4 to each other, and the second temperature range T ₂ and the third temperature range T ₂ in the range T _3,
What is necessary is just to be made of a rare earth transition metal alloy that can interrupt magnetic exchange coupling between the reproducing layer 3 and the recording layer 4.

In the first and second embodiments, the case where a DyFeCo alloy is used as the recording layer 4 is exemplified. However, as the recording layer 4, for example, a rare-earth transition metal It is also possible to use a thin film of an alloy. In short, the recording layer 4 maintains its magnetization information in the first to third temperature ranges T _{1 to} T ₃ , and in the third temperature range T ₃ ,
What is necessary is just to be made of a rare earth transition metal alloy capable of generating a floating magnetic field required for the magnetization reversal with respect to the reproducing layer 3.

[Embodiment 3] The following will describe still another embodiment of the present invention with reference to FIGS. 14 to 16. The present embodiment describes a magneto-optical recording medium according to the present invention and a method of modulating a recording magnetic domain using a magneto-optical recording / reproducing method.
For convenience of explanation, the same reference numerals are given to the components having the same functions as those shown in the drawings of the first embodiment, and the description thereof will be omitted.

(1) First Modulation Method First, the first modulation method will be described with reference to FIG. FIG. 1A is a plan view of a main part showing a state where five types of recording magnetic domains 30... (A1 to a5) having different sizes are formed on a track 1a of a magneto-optical disk as a magneto-optical recording medium. (B) is an explanatory diagram showing a synchronization signal 40 corresponding to the recording magnetic domains 30... (C) is a reproducing signal 50 reproduced from the recording magnetic domains 30. It is explanatory drawing which shows the intensity | strength (output). In the figure, the width of the track 1a is 0.9 μm, the diameter of the recording magnetic domain a1 is 0.7 μm, and the diameter of the recording magnetic domain a2 is 0.6 μm as the size of the recording magnetic domains 30 (a1 to a5). And the diameter of the recording magnetic domain a3 is 0.5 μm,
The case where the diameter of the recording magnetic domain a4 is 0.4 μm and the diameter of the recording magnetic domain a5 is 0.3 μm is illustrated.

In a magneto-optical disk, the track 1a
Are formed along the recording domain 3. The first modulation method is based on the recording domain 3 existing at a position corresponding to the synchronization signal 40.
By detecting the size of the recording magnetic domains 30.
The reproduction of the information recorded in the. In the conventional modulation method, it is difficult to accurately separate and detect a recording magnetic domain having a diameter of 0.6 μm or less. Therefore, digital information is reproduced by detecting the length of the digitally modulated recording magnetic domain. Is generally practiced. For example, when recording and reproduction are performed using a semiconductor laser having a wavelength of 680 nm, the length (diameter) of the shortest (minimum) recording magnetic domain needs to be 0.64 μm or more. That is, when a conventional magneto-optical disk is used, recording magnetic domains having a diameter of 0.64 μm or less cannot be accurately separated and detected.
Recording and reproduction must be performed using recording magnetic domains having a length (diameter) of 0.64 μm or more.

However, in the magneto-optical disk according to the present invention, as shown in FIG. 14C, it is possible to obtain a rectangular reproduction waveform having a sharp fall and a sharp rise, that is, a reproduced signal. It is. Therefore,
Even if the recording magnetic domains 30 have a diameter of 0.64 μm or less, it is possible to obtain a different reproduction waveform corresponding to the size of the digitally modulated recording magnetic domains 30 and reproduce digital information. Becomes That is, a reproduced signal having a short reproduction time width b1 is obtained corresponding to the large recording magnetic domain a1, and a reproduction signal having a long reproduction time width b5 is obtained corresponding to the small recording magnetic domain a5. In this manner, by detecting the time from the sharp fall to the sharp rise in the reproduced waveform, that is, the width b1 to b5 of the reproduction time of the reproduction signal, in accordance with the size of the recording magnetic domains 30,. Information can be detected with high accuracy. In the above description, the sizes of the recording magnetic domains 30 are 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, and
Although the case of five types of 0.3 μm is illustrated, the recording magnetic domain 3
Further increase the types of sizes of 0 ..., for example, 0.7 μm,
0.65μm, 0.6μm, 0.55μm, 0.5μm, 0.45μm,
Nine types of 0.4 μm, 0.35 μm, and 0.3 μm can be used.

(2) Second Modulation Method Next, a second modulation method will be described with reference to FIG. However, the description of portions overlapping with the first modulation method will be simplified. FIG. 3A shows the track 1
(a) is a plan view (explanatory view) of a main part showing a state in which five types of recording magnetic domains 30... (a1 to a5) are formed in FIG. 4
FIG. 3 (c) shows the recording magnetic domains 30.
FIG. 4D is an explanatory diagram showing the intensity of the reproduced signal 50 reproduced from the recording device, and FIG. 4D is an explanatory diagram showing a position signal 60 indicating the position of the recording magnetic domains 30 obtained from a change in the intensity of the reproduced signal 50. is there.

In the second modulation method, in addition to the first modulation method, digital information indicating the positions of the recording magnetic domains 30 is recorded as a position signal 60. As a result, higher density digital recording and reproduction can be performed. That is, as shown in FIG. 3C, the digital information corresponding to the size of the recording magnetic domains 30 is reproduced, and the change in the intensity of the reproduced signal 50 causes the recording magnetic domains 30 to change as shown in FIG. By reproducing the position signal 60 indicating the position of each of the recording magnetic domains 30... As digital information (-1, ± 0, +1), the digital information corresponding to the size and position of the recording magnetic domains 30. It is possible to do. In FIG. 3D, the case where the position signal 60 exists earlier than the signal position 40a (described later) of the synchronization signal 40 on the time axis is defined as (-1), and the same position is assumed. (± 0) when it exists at a position, and (+
1). As a result, it is possible to reproduce three types of digital information of (-1, ± 0, +1).

In the second modulation method, it is possible to perform recording and reproduction by making the size of the recording magnetic domains 30 constant and digitally modulating only the positions of the recording magnetic domains 30. In addition, since the widths b1 to b5 of the reproduction time of the reproduction signal are different depending on the size of the recording magnetic domains 30,... In order to accurately detect the position signal 60 of the recording magnetic domains 30,. By time-averaging the fall time and the rise time, the recording magnetic domains 30.
It is desirable to use the position signal 60 of FIG.

The position signal 60 of the recording magnetic domains 30 obtained in this manner is compared with the signal position 40a of the synchronization signal 40 shown in FIG. Thereby, the recording magnetic domains 30.
Digital information (-1, ±) corresponding to the position signal 60 of FIG.
0, +1) can be reproduced. In the above description, the case where the positional relationship between the position signal 60 and the signal position 40a is classified into three types has been exemplified. However, the positional relationship between the two is further subdivided so that more digital information can be stored in the recording domain 30. .. Can be recorded and reproduced as the position signal 60.

Even when the recording magnetic domains 30 are small, the reason why the position signal 60 can be detected with high accuracy is the same as the reason why the size of the recording magnetic domains 30 can be detected with high accuracy. The magneto-optical recording / reproducing method according to the present invention is capable of obtaining a rectangular reproduced waveform having a sharp fall and a sharp rise. In the above description, the case where the size of the recording magnetic domains 30... Is set to five types is exemplified. However, by further increasing the types of the sizes of the recording magnetic domains 30.
It is also possible to record and reproduce more digital information as the size of...

(3) Third Modulation Method Next, a third modulation method will be described with reference to FIG. However, the description of portions overlapping with the first and second modulation methods will be simplified. FIG.
Five kinds of recording magnetic domains 30 in the track 1a (a1 to a5)
Is a plan view (explanatory view) of a main part showing a state in which is formed. FIG. (B) is an explanatory view showing a synchronization signal 40 corresponding to these recording magnetic domains 30,. FIG. 4D is an explanatory diagram showing the intensity of the reproduced signal 50 reproduced from the recording magnetic domains 30. FIG. 4D shows a position signal 61 indicating the position of the recording magnetic domains 30 obtained from a change in the intensity of the reproduced signal 50.
FIG.

In the third modulation method, in addition to the first modulation method, digital information indicating an interval between adjacent recording magnetic domains 30 is recorded as a position signal 61. . As a result, higher density digital recording and reproduction can be performed. That is, after the position signal 61 indicating the position of the recording magnetic domain 30 is obtained from the change in the intensity of the reproduction signal 50 as shown in FIG. 3D, the distance between the position signals 61 (2x, 4x) is obtained. By reproducing the corresponding digital information, the digital information corresponding to the size of the recording magnetic domains 30 and the digital information corresponding to the interval between the position signals 61 can be recorded and reproduced independently. . That is, recording of a plurality of digital information, that is, multiplex recording can be performed by one recording magnetic domain 30.

By the way, when the distance between the adjacent recording magnetic domains 30 is apart by a certain distance or more, the reproduced signal is
(See FIG. 7). However, by detecting only the steep fall and the steep rise in the reproduced waveform, it is possible to reproduce digital information corresponding to the size of the recording magnetic domains 30 and the interval between the position signals 61. . In addition, the recording magnetic domains 30 ...
Of the reproduction time of the reproduction signal, b1 to b
5 are different from each other, in order to accurately detect the position signal 61 of the recording magnetic domains 30..., The fall time and the rise time in the reproduction waveform are time-averaged to obtain the position signals 61 of the recording magnetic domains 30. It is desirable.

In the second modulation method, the position signal 60 of the recording magnetic domains 30.
Although the digital information was recorded / reproduced based on the relative positional relationship with the position information a, the third modulation method uses the position signal 6
1 is digitally modulated, and the interval (2x,
4x) is recorded and reproduced. In the above description, the position signal 61
Although the case where the interval between the two is (2x, 4x) is exemplified, the type of the interval between the position signals 61 may be further increased, and more digital information may be recorded / reproduced corresponding to these intervals. It is possible. In the above description, the case where the sizes of the recording magnetic domains 30 are five types is exemplified. However, by further increasing the types of the sizes of the recording magnetic domains 30, the sizes of the recording magnetic domains 30 are increased. It is also possible to record and reproduce more digital information.

[Embodiment 4] Still another embodiment of the present invention will be described below with reference to FIGS. For convenience of explanation, the same reference numerals are given to the components having the same functions as those shown in the drawings of the first embodiment, and the description thereof will be omitted.

For example, a recording magnetic domain 4a having a mark length of 0.3 μm and a mark pitch of 0.6 μm is formed on the magneto-optical disk according to the present invention.
Are formed, and the recorded magnetic domains 4a are reproduced, the reproduced waveform of the obtained reproduced signal has a rectangular shape having an extremely steep falling edge and an extremely steep rising edge as shown in FIG. Becomes On the other hand, a recording magnetic domain is formed on a magneto-optical disk generally used conventionally, that is, a magneto-optical disk having a single magnetic layer with a mark length of 0.8 μm and a mark pitch of 1.6 μm, for example. Is reproduced, the reproduction waveform of the obtained reproduction signal has a shape similar to a sine curve because the spot of the light beam relatively moves as shown in FIG.

Generally, in a magneto-optical disk, since a differential detection method is used, fluctuations in signal amplitude due to a change in reflectance of the obtained reproduction signal are suppressed to some extent. However, in the reproduced signal, a fluctuation in signal amplitude due to a birefringence fluctuation or the like that cannot be suppressed by the differential detection method remains. Therefore, the reproduced waveform of the reproduced signal repeats a gentle up and down movement as shown in FIG. In this case, if the constant voltage level is set to the slice level, the size of the recording magnetic domain and the mark position (edge position) cannot be accurately detected due to the gradual vertical movement of the reproduced waveform.

Therefore, in order to suppress a reproduction error caused by a vertical movement of a reproduction waveform, generally, envelope detection is performed to obtain a final reproduction signal. That is, FIG.
As shown in FIG. 7, after the envelope detection circuit 70 detects each envelope (FIG. 17A) of the reproduced waveform of the reproduced signal, the slice level forming circuit 71 performs the slice level generation based on the average level of each envelope. Set. As a result, it is possible to suppress a change in the detection position of the recording magnetic domain due to the gentle vertical movement, and thus the mark position detection circuit 72
As a result, a final reproduction signal can be obtained, and the size of the recording magnetic domain and the mark position can be accurately detected.

Also, in the magneto-optical disk according to the present invention, the reproduction waveform of the reproduction signal repeats a gentle up and down movement as shown in FIG. However, the reproduced waveform of the magneto-optical disk according to the present invention has a steep fall and a steep rise as compared with the reproduced waveform of the conventional magneto-optical disk. Therefore, even when the constant voltage level is set to the slice level, the size and mark position of the recording magnetic domains 4a can be detected more accurately as compared with the conventional reproduction waveform. However, in order to detect the size and the mark position more accurately, it is desirable to perform envelope detection to obtain a final reproduced signal.

However, when processing the reproduced signal by performing the envelope detection described above, since the envelope detection causes a delay, it is necessary to delay the reproduced signal accordingly. Therefore, a circuit for performing envelope detection becomes complicated, for example, a delay circuit must be provided, and the time required to synchronize the slice level and the reproduction signal in the envelope detection is generated.

Therefore, in the present embodiment, the final reproduction signal is obtained by differentiating the reproduction waveform of the reproduction signal obtained from the magneto-optical disk. Since the reproduced waveform of the magneto-optical disk according to the present invention has a steep falling edge and a steep rising edge, by performing the differentiation processing, as shown in FIG. Is removed, and only a portion where the fluctuation in the reproduction signal is sharp, that is, only a rising portion and a falling portion in the reproduction signal can be obtained as a differential output of the differential signal. Note that the phase of the reproduced waveform of the conventional magneto-optical disk only changes even if it is differentiated, and it is difficult to obtain a differentiated signal as shown in FIG.

As described above, in the present embodiment, the adverse effect of the gradual vertical movement of the signal amplitude can be eliminated by differentiating the obtained reproduced signal.
.. can be obtained. That is, as shown in FIG. 19, after differentiating the reproduced signal by the differentiating circuit 74, the mark position detecting circuit 7
2, the position where the differential output from the differentiating circuit 74 is equal to or higher than the constant voltage slice level is detected. This allows
Since the delay circuit can be omitted, the reproduction signal can be accurately processed with a simple circuit configuration using the constant voltage slice level. Since the differential output of the differential signal shows a steep change, the position of the rising portion and the position of the falling portion in the reproduction signal can be accurately and easily detected. For example, FIG.
As shown in (c), by setting two types of constant voltage slice levels, the differential signal, that is, the position of the rising portion and the position of the falling portion in the reproduced signal can be separately and accurately detected. it can. Further, by further differentiating the differentiated signal shown in FIG. 3C, only two types of constant voltage slice levels are set,
The position of the rising portion and the position of the falling portion in the reproduced signal can be simultaneously and accurately detected.

As described above, by differentiating the reproduced signal, it is possible to eliminate the adverse effect of the gradual vertical movement of the signal amplitude, and to obtain the final reproduced signal indicating the exact size and position of the recording magnetic domains 4a. As a result, the signal quality required for the reproduced signal can be reduced. That is, conventionally, if the signal quality of a reproduced signal before signal processing is 45 dB or less in CNR, it is impossible to obtain an error rate of about 1 × 10 ⁻⁵ required for a magneto-optical disk. It had been. However, by using the magneto-optical recording / reproducing method according to the present invention, an error rate of 1 × 10 ⁻⁵ or less can be realized even when the signal quality of the reproduced signal before signal processing is about 35 dB in CNR. it can. That is, the above error rate can be obtained even in the relatively small recording magnetic domains 4a of which the signal quality of the obtained reproduction signal is about 35 dB, so that higher-density recording and reproduction can be realized.

Next, in the magneto-optical disk, the diameter (mark length) is variously changed within the range of 0.25 μm to 0.8 μm, and recording magnetic domains 4 a are formed at a mark pitch twice as large as the diameter. The CNR and error rate (hereinafter, referred to as Er) of a reproduced signal obtained when the magnetic domains 4a are reproduced.
Was measured. That is, the recording magnetic domains 4a of the magneto-optical disk ...
The relationship between the diameter of CNR and Er was examined. Table 6 shows the results.

The embodiment shown in Table 6 corresponds to FIG.
(C) shows the result for the reproduced signal of the present embodiment, and the comparative example shows the result for the conventional reproduced signal shown in (a) of FIG. CNR2 indicates the CNR of the reproduced signal shown in FIG. 3B, and CNR1 indicates the CNR of the reproduced signal shown in FIG. Also, Er2 indicates Er of the reproduced signal shown in FIG. 3B, Er3 indicates Er of the differential signal shown in FIG. 3C, and Er1 indicates the reproduced signal shown in FIG. It shows the Er of the signal.

[0145]

[Table 6]

As is apparent from Table 6, the shape of the reproduced signal of the present embodiment shown in FIG. 7B does not resemble a sine curve, and the CNR2 is relatively low in the range of 32 dB to 42 dB. . However, as described above, in the present invention, the state (the size and the position) of the recording magnetic domains 4a can be accurately detected by utilizing the sharp fall and the sharp rise of the reproduced waveform. For this reason, even when the CNR2 is 35 dB, that is, even when the diameter of the recording magnetic domains 4a is 0.3 μm, Er2 is a value of 1 × 10 ⁻⁵ or less (0.9 × 10 ⁻⁵ ), and the magneto-optical disk It can be seen that the required Er can be realized. Further, Er3 of the differential signal is 1 × 10 even when CNR2 is 32 dB, that is, even when the diameter of the recording magnetic domains 4 a is 0.25 μm.
^-5 or less (0.9 × 10 ^-5 ) has been achieved. Therefore, it can be seen that higher-density recording and reproduction can be realized by differentiating the reproduction signal.

On the other hand, in the conventional reproduction signal shown in FIG. 11A, when the diameter of the recording magnetic domain is smaller than 0.6 μm, the CNR1 becomes extremely low and the Er1 becomes 1 × 10 5.
It becomes a value of ^-5 or more (1.9 × 10 ^-5 ). Therefore, it is understood that Er required for the magneto-optical disk cannot be realized when the diameter of the recording magnetic domain is smaller than 0.6 μm in the conventional reproduction signal.

[Fifth Embodiment] The following will describe still another embodiment of the present invention with reference to FIG. The present embodiment describes a magneto-optical recording medium and a magneto-optical recording / reproducing method according to the present invention. For convenience of explanation, the same reference numerals are given to the components having the same functions as those shown in the drawings of the first embodiment, and the description thereof will be omitted.

A magneto-optical disk as a magneto-optical recording medium according to the present invention has a recording magnetic domain 4 having a submicron diameter.
a ... are recorded and reproduced. By the way, generally, in a magneto-optical disk, it is necessary to make the characteristics of the recording layer almost uniform over the whole so that accurate recording / reproduction with respect to a relatively small recording magnetic domain is performed. For this reason, it is necessary to use a high-precision film-forming apparatus capable of suppressing variations in characteristics (hereinafter, referred to as characteristic distribution) of the entire recording layer. Further, in order to record / reproduce information on / from the recording magnetic domain on the magneto-optical disk, a magneto-optical disk device (magneto-optical recording / reproducing device) capable of controlling the power of the light beam emitted from the semiconductor laser with high accuracy is used. Must be used. Therefore, the conventional magneto-optical disk and the magneto-optical disk device have a problem that the manufacturing cost is relatively high. Therefore, a magneto-optical disk having a relatively low manufacturing cost and a magneto-optical recording / reproducing method capable of performing recording / reproducing on the magneto-optical disk without controlling the power of the light beam with high precision are desired. I have.

The magneto-optical disk according to this embodiment is
As shown in FIG. 20A, a data recording section 80 and a reference magnetic domain recording section 81 are alternately and continuously provided on a track 1a. In the data recording sections 80, recording magnetic domains 4a are formed, and data (information) is recorded.
A recording magnetic domain serving as a reference (hereinafter, referred to as a reference magnetic domain) is formed in the above-described reference magnetic domain recording sections 81, and the size of the reference magnetic domain and / or the position of the reference magnetic domain is recorded. The formation of the reference magnetic domain recording sections 81 allows the magneto-optical disk to perform good recording / reproduction even when the data recording sections 80 have a certain degree of characteristic distribution. I have. Further, even when the power of the light beam is not controlled with high precision, that is, even when the power of the light beam fluctuates to some extent, it is possible to perform good recording and reproduction on the magneto-optical disk. It has become. That is, by forming the data recording units 80 and the reference magnetic domain recording units 81 alternately and continuously, it is possible to reproduce the data at the time of reproduction while referring to the output of the reproduction signal obtained from the reference magnetic domain. it can. Therefore, good recording and reproduction can be performed without being affected by the above-described characteristic distribution, fluctuations in the power of the light beam, and the like.

FIGS. 20 (b) to 20 (d) are plan views (explanatory diagrams) of main parts showing a state where the reference magnetic domains 90 are formed in the reference magnetic domain recording section 81 of the track 1a. FIG.
This shows a state in which reference magnetic domains 90 having the same size are formed at equal intervals. In this case, the reference magnetic domain 90 ...
By generating the synchronization signal 41 by detecting the position of
Variations in the moving speed of the track 1a, that is, apparent fluctuations in the distance between the recording magnetic domains 4a due to fluctuations in the rotational speed of the magneto-optical disk and the like can be suppressed. Therefore, recording and reproduction can be performed on the magneto-optical disk without using a high-precision rotating mechanism, that is, without controlling the rotation speed of the magneto-optical disk with high accuracy.

FIG. 17C shows a state in which reference magnetic domains 90 having different sizes are formed at equal intervals. Also in this case, it is possible to suppress the apparent fluctuation of the interval between the recording magnetic domains 4a due to the fluctuation of the rotation speed of the magneto-optical disk and the like, as described above, so that the rotation speed of the magneto-optical disk can be controlled with high accuracy. Recording and reproduction can be performed on the magneto-optical disk without performing this operation. Further, the magneto-optical disk according to the third embodiment (see FIGS. 14 to 16)
By applying the present embodiment to the present embodiment (ie, FIG. 10C), the output of a reproduction signal obtained from the reference magnetic domains 90..., That is, the size of the reference magnetic domains 90. , The size of the recording magnetic domains 4a can be detected. Therefore, good recording and reproduction can be performed without being affected by the above-described characteristic distribution, fluctuations in the power of the light beam, and the like.

FIG. 17D shows a state in which reference magnetic domains 90 having the same size are formed at a specific interval, that is, a state where they are formed at positions shifted by a predetermined amount from the position corresponding to the synchronization signal 40. Is shown. In this case, by applying the present embodiment (that is, FIG. 15D) to the magneto-optical disk according to the third embodiment (see FIG. 15),
At the time of recording / reproduction, the position of the recording magnetic domains 4a can be detected with reference to the position signal 62 indicating the position of the reference magnetic domains 90. As a result, it is possible to suppress an apparent change in the interval between the recording magnetic domains 4a, which is caused by a change in the rotation speed of the magneto-optical disk and the like, as described above, so that the rotation speed of the magneto-optical disk is not controlled with high accuracy. However, recording and reproduction can be performed on the magneto-optical disk.

Then, in each of the reference magnetic domain recording sections 81, the reference magnetic domains 9 of the three types of patterns shown in FIGS.
. 0 are continuously formed, recording and reproduction can be performed without being influenced by the above-mentioned characteristic distribution, fluctuations in the power of the light beam, and the like. In addition, apparent fluctuations in the spacing between the recording magnetic domains 4a. Recording and reproduction can be performed independently of each other. That is, good recording and reproduction can be performed without being influenced by the characteristic distribution, various fluctuations, and the like. The order in which the three types of patterns are formed in the reference magnetic domain recording unit 81 is not particularly limited.

[0155]

As described above, the magneto-optical recording medium according to the first aspect of the present invention has a recording layer having a recording magnetic domain in which information is recorded by a perpendicular magnetization direction, and the information recorded in the recording layer. A reproducing layer having a reproducing magnetic domain transferred by a perpendicular magnetization direction, and an intermediate layer laminated between the recording layer and the reproducing layer and having a Curie temperature lower than the Curie temperatures of the recording layer and the reproducing layer. In a case where the reproducing layer has a first temperature range lower than the Curie temperature of the intermediate layer, the magnetization state of the recording layer is transferred by magnetic exchange coupling, and is equal to or higher than the Curie temperature of the intermediate layer and has a predetermined size in the reproducing layer. In the second temperature range in which the minute magnetic domains become unstable, the magnetization direction coincides with the magnetization direction of the unrecorded portion of the recording layer, and is equal to or higher than the Curie temperature of the intermediate layer and the minute magnetic domains become stable. In the temperature range of 3 A configuration in which the magnetization state of the recording layer is formed so as to be transferred by the magnetostatic coupling.

Therefore, after the information transferred to the reproducing layer whose temperature has been increased by the irradiation of the light beam is erased, information of a part of the recording layer whose temperature has been further increased by the irradiation of the light beam, ie, the light beam It is possible to transfer only information of a part of the recording layer located in the spot to the reproducing magnetic domain of the reproducing layer and reproduce the information. This enables a super-resolution operation for reproducing information recorded in an area (recorded magnetic domain) smaller than the spot diameter of the light beam. As a result,
The effect that the recording density required for large-capacity recording can be sufficiently attained and a magneto-optical recording medium which can sufficiently cope with recording of image information or the like which requires large-capacity recording / reproduction can be provided. To play.

According to the method of recording / reproducing a magneto-optical recording medium according to the second aspect of the present invention, as described above, the magneto-optical recording medium according to the first aspect is irradiated with a light beam, and the temperature of the reproducing layer is reduced to the second level. The steep fall of the read signal accompanying the instantaneous disappearance of the read magnetic domain occurring when the temperature shifts from the first temperature range to the second temperature range, and the temperature of the read layer changes from the second temperature range to the third temperature. In this method, a steep rise of a reproduction signal caused by instantaneous generation of a reproduction magnetic domain which occurs when shifting to the range is detected by the light beam.

Therefore, it is possible to accurately detect the edge position of the recording magnetic domain of the recording layer by utilizing the sharp fall and the sharp rise of the reproduction signal. This enables a super-resolution operation for reproducing information recorded in an area smaller than the spot diameter of the light beam. As a result, there is an effect that it is possible to provide a recording / reproducing method for a magneto-optical recording medium that can sufficiently cope with recording of, for example, image information or the like which requires large-capacity recording / reproduction.

According to the method of recording / reproducing a magneto-optical recording medium according to claim 3 of the present invention, as described above, in the first temperature range,
The magnetization state of the recording layer is transferred to the reproduction layer by magnetic exchange coupling, and in the second temperature range, the magnetization direction of the reproduction layer matches the magnetization direction of the stray magnetic field generated from the unrecorded portion of the recording layer. In the temperature range of 3, the magnetization direction of the reproducing layer is made to coincide with the magnetization direction of the stray magnetic field generated from the recording layer.

As a result, it is possible to stably realize the disappearance and generation of the reproducing magnetic domains of the reproducing layer due to the temperature rise due to the irradiation of the light beam, so that more stable recording and reproducing can be performed. It works.

According to the recording / reproducing method for a magneto-optical recording medium according to the fourth aspect of the present invention, as described above, an external magnetic field is further applied to the magneto-optical recording medium, and in the first temperature range, the magnetic field is applied to the reproducing layer. The magnetization state of the recording layer is transferred by magnetic exchange coupling. In a second temperature range, the magnetization direction of the reproduction layer matches the direction of the external magnetic field, and in a third temperature range, the magnetization direction of the reproduction layer is recorded. This is a method of matching the magnetization direction of the stray magnetic field generated from the layer.

As a result, it is possible to stably realize the disappearance and generation of the reproducing magnetic domain of the reproducing layer due to the temperature rise due to the light beam irradiation, so that more stable recording and reproducing can be performed. It works.

The recording / reproducing method for a magneto-optical recording medium according to the fifth aspect of the present invention is a method for recording information with the size of the recording magnetic domain of the recording layer and the position of the recording magnetic domain as described above. is there.

Therefore, it is possible to independently record and reproduce information corresponding to the size of the recording magnetic domain and information corresponding to the position of the recording magnetic domain. Thereby, recording of a plurality of information, that is, multiplex recording can be performed by one recording magnetic domain. As a result, recording / reproducing is required for a magneto-optical recording medium which can sufficiently cope with recording of image information or the like, for example, where recording / reproducing of a larger capacity is required, that is, for a magneto-optical recording medium having a larger capacity. There is an effect that recording and reproduction can be performed.

According to the recording / reproducing method for a magneto-optical recording medium according to the sixth aspect of the present invention, as described above,
In this method, the position of the recording magnetic domain is obtained by the time average of the falling portion and the rising portion of the reproduction signal, while the difference is obtained from the time difference between the falling portion and the rising portion of the reproduction signal.

As a result, the size and position of the recording magnetic domain can be detected more accurately, so that there is an effect that more stable recording and reproduction can be performed.

According to the method of recording / reproducing a magneto-optical recording medium according to claim 7 of the present invention, as described above, a plurality of recordings having a size and / or a position to be a reference at the time of reproduction on a recording layer. This is a method of forming magnetic domains.

Therefore, at the time of reproduction, information can be reproduced with reference to the output of the reproduction signal obtained from the recording magnetic domain. Accordingly, even when the characteristics of the entire recording layer have a certain degree of variation or when the power of the light beam fluctuates to a certain degree, the characteristics are further improved without being affected by these variations and fluctuations. It is possible to perform an effective recording and reproduction.

The recording / reproducing method for a magneto-optical recording medium according to claim 8 of the present invention is a method for differentiating the reproduced signal as described above.

Therefore, a portion where the fluctuation in the reproduction signal is steep, that is, a steep falling and a steep rising of the reproduction signal can be more easily detected. Therefore, it is possible to more accurately detect the position of the recording magnetic domain or the edge position of the recording magnetic domain. As a result, even if the recording density is increased by further reducing the recording magnetic domain,
Information recorded in the recording magnetic domain can be reproduced. That is, there is an effect that recording and reproduction with higher density can be realized.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory diagrams illustrating the principle of reproduction of a magneto-optical disk as a magneto-optical recording medium according to an embodiment of the present invention; FIG. 1A is an explanatory diagram illustrating a temperature distribution on a track;
(B) is an explanatory diagram showing a case where a recording magnetic domain exists in a first temperature range, (c) is an explanatory diagram showing a case where a recording magnetic domain exists in a second temperature range, and (d) is a third temperature. FIG. 4 is an explanatory diagram showing a case where a recording magnetic domain exists in a range.

FIG. 2 is an explanatory diagram illustrating a configuration of the magneto-optical disk.

FIG. 3 is a graph showing temperature dependence of a stable magnetic domain width in a reproducing layer of the magneto-optical disk.

FIG. 4 is a graph showing mark length dependence (recording / reproduction characteristics) of a signal-to-noise ratio in the magneto-optical disk.

FIG. 5 is a graph showing the reproduction power dependency (recording / reproduction characteristics) of the signal-to-noise ratio in the magneto-optical disk.

FIGS. 6A to 6E are plan views each showing a main part of the magneto-optical disk.

FIGS. 7A to 7E are waveform diagrams showing waveforms of a reproduction signal of the magneto-optical disk.

FIGS. 8A to 8F are plan views each showing a main part of the magneto-optical disk.

FIGS. 9A to 9F are waveform diagrams showing waveforms of a reproduction signal of the magneto-optical disk.

FIGS. 10A to 10F are waveform diagrams showing waveforms of a reproduction signal of the magneto-optical disk.

FIG. 11 is an explanatory diagram illustrating a reproducing method of the magneto-optical disk.

12A and 12B are explanatory diagrams illustrating the principle of reproduction of a magneto-optical disk according to another embodiment of the present invention. FIG. 12A is an explanatory diagram illustrating a temperature distribution on a track, and FIG. 12B is a diagram illustrating a first temperature. Explanatory diagram showing a case where a recording magnetic domain exists in a range, (c) is an explanatory diagram showing a case where a recording magnetic domain exists in a second temperature range,
(D) is an explanatory diagram showing a case where a recording magnetic domain exists in the third temperature range.

13 is an explanatory diagram illustrating the configuration of the magneto-optical disk of FIG.

FIG. 14 is an explanatory diagram for explaining a recording / reproducing method (first modulation method) for a magneto-optical disk according to still another embodiment of the present invention, and FIG. FIG. 3B is a waveform diagram showing the waveform of the synchronization signal, and FIG.
FIG. 4 is a waveform diagram showing a waveform of a reproduction signal of the magneto-optical disk.

15A and 15B are explanatory diagrams illustrating a recording / reproducing method (second modulation method) of the magneto-optical disk in FIG. 14, wherein FIG. 15A is an explanatory diagram illustrating a main part of the magneto-optical disk, and FIG. (C) is a waveform diagram showing a waveform of a reproduction signal of the magneto-optical disk, and (d) is a waveform diagram showing a waveform of a position signal.

16A and 16B are explanatory diagrams illustrating a recording / reproducing method (third modulation method) of the magneto-optical disk in FIG. 14, wherein FIG. 16A is an explanatory diagram illustrating a main part of the magneto-optical disk, and FIG. (C) is a waveform diagram showing a waveform of a reproduction signal of the magneto-optical disk, and (d) is a waveform diagram showing a waveform of a position signal.

FIG. 17A is a waveform diagram showing a waveform of a reproduction signal of a conventional magneto-optical disk, and FIG. 17B is a waveform diagram showing a waveform of a reproduction signal of a magneto-optical disk according to still another embodiment of the present invention. (C) is a waveform diagram showing a waveform of a differentiated signal obtained by differentiating the reproduced signal of (b).

FIG. 18 is a block diagram showing a processing circuit provided for waveform correction (envelope detection) in a conventional magneto-optical disk reproducing method.

FIG. 19 is a block diagram showing a processing circuit provided for waveform correction (differential processing) in the magneto-optical disk reproducing method of FIG. 17 (b).

FIG. 20A is an explanatory view showing a main part of a magneto-optical disk according to still another embodiment of the present invention, and FIGS.
(D) is an explanatory view showing a main part of a reference magnetic domain recording unit of the magneto-optical disk.

[Explanation of symbols]

Reference Signs List 1 substrate 1a track 3 reproducing layer 4 recording layer 4a recording magnetic domain 8 light beam 8a spot 9 intermediate layer 19 intermediate layer T ₁ first temperature range T ₂ second temperature range T ₃ third temperature range

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akira Takahashi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 11/105

Claims (8)

(57) [Claims] 1. A recording layer having a recording magnetic domain in which information is recorded in a perpendicular magnetization direction, a reproducing layer having a reproducing magnetic domain in which information recorded in the recording layer is transferred in a perpendicular magnetization direction, and a recording layer. An intermediate layer having a lower Curie temperature than the recording layer and the reproducing layer, wherein the reproducing layer has a first temperature range lower than the Curie temperature of the intermediate layer. The magnetic state of the recording layer is transferred by magnetic exchange coupling, and the second magnetic domain in which a minute magnetic domain having a predetermined size in the reproducing layer is higher than the Curie temperature of the intermediate layer becomes unstable.
In the third temperature range, the magnetization direction coincides with the magnetization direction of the unrecorded portion of the recording layer in the temperature range of not less than the Curie temperature of the intermediate layer and the minute magnetic domains are stable. A magneto-optical recording medium formed so that the magnetization state of a layer is transferred. 2. An instant of a reproducing magnetic domain, which is generated when a temperature of a reproducing layer shifts from a first temperature range to a second temperature range by irradiating a light beam to the magneto-optical recording medium according to claim 1. Sharp fall of the reproduction signal due to the temporary disappearance, and the steepness of the reproduction signal accompanying the instantaneous generation of the reproduction magnetic domain generated when the temperature of the reproduction layer shifts from the second temperature range to the third temperature range. A recording and reproducing method for a magneto-optical recording medium, wherein a rising edge is detected by the light beam. 3. In a first temperature range, the magnetization state of the recording layer is transferred to the reproducing layer by magnetic exchange coupling. In a second temperature range, the magnetization direction of the reproducing layer is generated from an unrecorded portion of the recording layer. The magnetization direction of the reproducing layer is made to coincide with the magnetization direction of the floating magnetic field generated from the recording layer in the third temperature range.
Recording / reproducing method for the magneto-optical recording medium according to the above. 4. An external magnetic field is further applied to the magneto-optical recording medium. In a first temperature range, the magnetization state of the recording layer is transferred to the reproducing layer by magnetic exchange coupling. In a second temperature range, 3. The magnetization direction of the reproducing layer is made to coincide with the direction of the external magnetic field, and in a third temperature range, the magnetization direction of the reproducing layer is made to coincide with the magnetization direction of a floating magnetic field generated from the recording layer. Recording / reproducing method for the magneto-optical recording medium according to the above. 5. The method for recording / reproducing a magneto-optical recording medium according to claim 2, wherein information is recorded by a size of a recording magnetic domain of the recording layer and a position of the recording magnetic domain. 6. The size of a recording magnetic domain is determined by a time difference between a falling part and a rising part of a reproduction signal, and the position of the recording magnetic domain is determined by the time average of the falling part and the rising part of the reproduction signal. 6. The method for recording / reproducing information on a magneto-optical recording medium according to claim 5, wherein 7. A magneto-optical recording medium according to claim 5, wherein a plurality of recording magnetic domains having a size and / or a position to be a reference at the time of reproduction are formed in the recording layer. Recording and playback method. 8. A recording / reproducing method for a magneto-optical recording medium according to claim 2, wherein said reproducing signal is subjected to a differentiation process.