JP2003006952A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic domain wall transfer type magneto-optical recording medium capable of compensating an edge shift in recording caused by a demagnetizing field of magnetic domains most recently used for recording in reproduction. SOLUTION: The magneto-optical recording medium has a magnetic domain wall transfer layer/an interrupting layer/a memory layer as a basic composition and a floating magnetic field generated from the memory layer at least at the Curie temperature of the interrupting layer acts in such a way that the transfer of magnetic domain walls in the magnetic domain wall transfer layer is hindered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording / reproducing information with a laser beam by utilizing a magneto-optical effect. In particular, the present invention relates to a domain wall motion type magneto-optical recording medium that enlarges and reproduces magnetic domains by utilizing the movement of domain walls.

[0002]

2. Description of the Related Art In recent years, as a rewritable high-density recording method, magneto-optical recording is used in which magnetic domains are written in a magnetic thin film by using thermal energy of a semiconductor laser to record information and the recorded information is read out by using a magneto-optical effect. A medium and a recording / reproducing apparatus are receiving attention. Recently, the data to be handled is voice,
Since various information such as images and moving images has been diversified and the data size required for them has been increasing, there is an increasing demand for increasing the recording density of this magneto-optical recording medium to obtain a recording medium having a larger capacity.

Generally, the recording density of a magneto-optical recording medium such as a magneto-optical disk greatly depends on the laser wavelength of the reproducing optical system and the numerical aperture NA of the objective lens. That is, since the diameter of the beam waist is determined when the laser wavelength λ of the reproducing optical system and the numerical aperture NA of the objective lens are determined, the spatial frequency of the signal-reproducible recording pit is limited to about 2NA / λ.

Therefore, in order to realize high density in the conventional optical disc, it is necessary to shorten the laser wavelength of the reproducing optical system or increase the numerical aperture of the objective lens. However, it is not easy to shorten the laser wavelength due to problems such as element efficiency and heat generation, and when the numerical aperture of the objective lens is increased, the distance between the lens and the disk becomes too close, causing mechanical problems such as collision. .

On the other hand, a so-called magnetic super-resolution technique has been developed in which the structure of the recording medium and the reproducing method are devised to improve the recording density. For example, in JP-A-7-334877, a memory layer for holding recorded information, a reproducing layer for masking a part of the reproducing spot, and a blocking layer for controlling their exchange coupling force are laminated to form a reproducing spot. A super-resolution method has been proposed in which the recorded information is transferred to the reproducing layer substantially only in a part of the spot by utilizing the temperature distribution on the medium generated by irradiating the magnetic field to reproduce the minute magnetic domain.

However, in the conventional super-resolution method, a part of the reproduction light spot is masked by utilizing the temperature distribution, that is, the resolution is substantially increased by limiting the aperture for reading the pit to a small area. Since the method is adopted, there is a problem that the light of the masked portion is wasted and the reproduction signal amplitude becomes small. That is, since the light in the masked portion does not contribute to the reproduction signal, the light used effectively decreases as the aperture is narrowed in order to increase the resolution, and the signal level decreases.

According to Japanese Patent Laid-Open No. 6-290496, a domain wall moving layer having a small domain wall coercive force is provided on the reproducing light incident side, and the magnetic wall of the domain wall moving layer is placed on the high temperature side by utilizing the temperature gradient in the reproducing spot. Is disclosed, in which the magnetic domain is enlarged and reproduced in the spot. According to this, even if the recording mark size becomes small, the signal is reproduced while enlarging the magnetic domain, so that the reproduction light can be effectively used, and the resolution can be improved without reducing the signal amplitude.

[0008]

By the way, in a general magneto-optical recording medium, at the time of recording information, due to the influence of the demagnetizing field generated from the recording film itself, the information is recorded at a position different from the original recording position. There was a problem that a domain wall was formed. This will be described with reference to FIG.

FIG. 6A shows a case of a conventional recording medium having a single memory layer for simplifying the description. The memory layer 3, which is a perpendicularly magnetized film, is formed on a disk-shaped substrate (not shown) and rotates at high speed. When a high-power laser is irradiated while the magnetic field is applied to the medium in the direction to record information by the external magnetic field Hw to raise the temperature of the memory layer to the Curie temperature, the medium temperature falls below the Curie temperature behind the laser spot. At this time, the recording magnetic domain is formed in the direction according to the direction of the external magnetic field. However, there is a portion where the magnetic domain has already been formed and the temperature has dropped sufficiently, further behind the position where the magnetic domain is formed, and this portion generates a demagnetizing field according to the saturation magnetization. For example, FIG. 6 (a)
After forming the downward magnetic domain, an upward demagnetizing field is generated as shown in FIG. Such a demagnetizing field fluctuates the effective magnetic field strength applied to the memory layer by the external magnetic field Hw, which hinders accurate formation of magnetic domains. That is, FIG.
In the case of (a), since the demagnetizing field is upward and the external magnetic field when forming the next magnetic domain is also upward, they are in the same direction, and there is substantially the same effect as increasing the external magnetic field. B slightly behind the position of A where the magnetic domain should be originally formed
A magnetic domain will be formed at the position 1. Hereinafter, this is referred to as recording edge shift.

Further, when the magnetic domain recorded immediately before is long as shown in FIG. 6B, the demagnetizing field also becomes large, so that the amount of edge shift during recording also becomes large, and the magnetic domain forming position shifts to the position B2. I will end up.

That is, when a random pattern as shown in FIG. 6C is recorded, since the edge shift during recording differs depending on the immediately preceding pattern, the position where the magnetic domain is actually recorded is shown in FIG. It becomes like d).

This problem becomes a particularly serious problem in the case of minute magnetic domain recording described in Japanese Patent Laid-Open No. 6-290496, etc., and accurate information recording / reproducing cannot be performed in some cases. Further, a method of compensating for the edge shift at the time of recording by electrically correcting the modulation pattern at the time of recording has been devised, but there is a problem that the apparatus becomes complicated.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an optical system without complicating a reproducing apparatus or a recording medium structure. It is an object of the present invention to provide a magneto-optical recording medium capable of accurately reproducing a signal having a recording density exceeding the resolution of 1.

Then, one mode for achieving the above object is as follows. A domain wall moving layer that contributes to the reproduction of information and in which a domain wall moves, a memory layer that holds a recording magnetic domain according to information, and a cutoff that is arranged between the moving layer and the memory layer and has a Curie temperature lower than both layers. A magneto-optical recording medium having a layer and reproducing the information by moving a domain wall of a recording magnetic domain transferred from the memory layer to the moving layer in a region having a Curie temperature of the blocking layer or higher to expand the recording magnetic domain. In the above, at least at the Curie temperature of the blocking layer, the stray magnetic field generated from the memory layer acts in the direction of hindering the movement of the domain wall in the domain wall moving layer.

The details will be described in the following embodiments.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1A shows a sectional view of the optical disk in this embodiment. As shown in FIG. 1, in the optical disc used in this embodiment, an interference layer 102, a domain wall displacement layer 1, a blocking layer 2, a memory layer 3, and a protective layer 103 are laminated in this order on a substrate 101. Here, the arrow 11 in each magnetic material represents the direction of the transition metal sublattice magnetization of the recording magnetic domain held in the film,
Bloch domain wall 12
Exists. The substrate 101 is usually made of glass or a transparent material such as polycarbonate. Each of these layers can be deposited by continuous sputtering using a magnetron sputtering device, continuous vapor deposition, or the like. The interference layer 102 is provided to enhance the magneto-optical effect, and a transparent dielectric material such as Si ₃ N ₄ , AlN, SiO ₂ , SiO, ZnS, and MgF ₂ is used. The protective layer 103 is used for protecting the magnetic layer, and the same material as the interference layer 102 is used. In addition, in order to optimize the thermal structure of the entire medium, Al, AlTa, AlTi, AlCr, and
In some cases, a metal layer made of Cu or the like is provided. Interference layer 10
2, the protective layer 103 and the metal layer provided as necessary are not related to the essence of the present invention, and therefore detailed description thereof is omitted here.

The memory layer 3 is made of a rare earth-iron group element amorphous alloy, such as TbFeCo, DyFeCo, TbDyFeCo, which has a large perpendicular magnetic anisotropy so that minute recording pits can be stably stored. Information is retained whether the magnetic domains in this layer are facing up or down. Also, garnets, Pt / Co, Pd
A perpendicular magnetization film such as / Co may be used so that information can be magnetically transferred to another layer.

The blocking layer 2 is made of, for example, GdCo, GdFeCo, GdFe,
GdFeCoAl, DyFeCoAl, TbFe, TbFeCo, TbFeCoAl, TbDyFe
The rare earth-iron group amorphous alloy such as CoAl and TbFeAl is used, and the Curie temperature is set lower than that of the other layers.

The domain wall displacement layer 1 is, for example, GdCo, GdFeCo, GdF.
Materials for bubble memories such as rare earth-iron group amorphous alloys and garnets, which have smaller perpendicular magnetic anisotropy and domain wall coercive force than memory layers such as e and NdGdFeCo, are desirable.

The Curie temperatures of the respective layers satisfy the relationship of Tc1, Tc3> Tc2, and the memory layer 3 is exchange-coupled at room temperature.
The magnetic domain recorded in 1 is transferred to the domain wall motion layer 1.

The thickness of each layer is 20 to 10 for the interference layer 102.
0 nm, domain wall displacement layer 1 is 20 to 40 nm, blocking layer 2 is 7
˜20 nm, memory layer 3 is 40 to 100 nm, protective layer 1
03 is 40 to 80 nm.

A protective coat made of a polymer resin may be further added to this structure. Alternatively, the substrate 101 after the film formation may be attached. Also, the light incident direction at the time of recording / reproducing may be opposite to the substrate by reversing the stacking order.

The recording of the data signal on the optical disk of the present invention is performed by moving the medium and irradiating with a laser beam having a power such that the memory layer 3 is around the Curie temperature Tc3 while modulating the external magnetic field. In this case, if the modulation frequency of the external magnetic field is increased, a recording magnetic domain smaller than the light spot diameter can be formed, and as a result, a signal can be recorded in a cycle below the diffraction limit of light.

FIG. 1B shows the temperature distribution at the track center when the disc moves to the right while irradiating the disc with laser light. The position where the film temperature is maximum in this temperature profile is slightly behind the center of the laser spot, depending on the linear velocity of the disk. FIG. 1C is a diagram showing the distribution of the domain wall energy density σ ₁ in the domain wall displacement layer 1. In this way, the domain wall energy density σ ₁ decreases as the temperature rises, so if there is a temperature gradient in the moving direction of the optical disk, the domain wall energy density σ ₁ decreases toward the maximum temperature position. Then, the force F _{1 given} by the following formula acts on the domain wall of the domain wall displacement layer existing at the position x.

F ₁ = dσ ₁ / dx This force F ₁ acts to move the domain wall toward the lower domain wall energy, and the domain wall displacement layer 1 has a small domain wall coercive force and a large domain wall mobility. This force F ₁ easily moves the domain wall.

In FIG. 1A, each magnetic layer is a perpendicular magnetization film and the magnetic domain recorded in the memory layer 3 is the blocking layer 2 before the disc is irradiated with the reproducing laser beam, that is, at the room temperature. Exchange-coupled with the domain wall motion layer 1 via the magnetic domain, and the magnetic domain is transferred. At this time, the domain walls 12 are present between the magnetic domains 11 in directions opposite to each other in each layer. When the film temperature rises to the Curie temperature Tc2 of the blocking layer 2, the exchange coupling from the memory layer 3 to the blocking layer 2 is broken,
The domain wall moving layer 1 having a small domain wall coercive force cannot hold the magnetic domain,
The domain wall moves to the high temperature side according to the force F ₁ applied by the temperature gradient. At this time, the moving speed of the domain wall is sufficiently higher than the moving speed of the disk, so that a magnetic domain larger than the magnetic domain recorded in the memory layer 3 is obtained in the laser spot.

FIG. 2 is a diagram for explaining the domain wall moving operation described above in consideration of the net magnetization of each layer. The arrows in the films of each layer indicate the direction of the transition metal sublattice magnetization, as in FIG. 1, in which the net magnetization is downward in the shaded area and the net magnetization is upward in the white area. Is shown. It should be noted that in FIG. 2, dielectric layers and the like which are not related to the essence of the present invention are omitted.

In order to reduce the stray magnetic field from the layer itself and move the domain wall quickly, the domain wall displacement layer 1 has a rare earth element sublattice magnetization predominance at room temperature, and the compensation temperature from the Curie temperature of the blocking layer to that of the domain wall displacement layer. Set between Curie temperatures.

On the other hand, the memory layer is constituted so that the rare earth element sublattice magnetization is dominant in at least the temperature region near Tc2 including the Curie temperature Tc2 of the blocking layer. By doing so, as is apparent from FIG. 2, the net magnetizations of the domain wall displacement layer and the memory layer are opposite to each other in the region (aperture region) in which the domain wall displacement in the light spot moves, and the domain wall displacement of the domain wall displacement layer is moved. At the start position, the stray magnetic field from the memory layer acts in the direction that hinders the movement of the domain wall.

The force that the domain wall receives from the stray magnetic field of the memory layer becomes larger as the recording mark in the aperture area becomes longer. Therefore, the position of the domain wall actually recorded in the memory layer (FIG. 2B). On the other hand, the actual domain wall movement start timing can be shifted as shown in FIG. That is, it is possible to cause an edge shift during reproduction according to the recording mark length. Considering this together with the above-mentioned edge shift during recording, the edge shift during recording with respect to the desired recording signal shown in FIG.
The magnetic domain at the position as shown in (b) is canceled by the edge shift at the time of reproduction, and accurate information reproduction as shown in FIG. 3 (d) can be performed.

Since the situation in which the recording edge shift is generated and the situation in which the reproducing edge shift is generated are strictly different, the recording edge shift amount cannot be exactly canceled during the reproduction, but the recording edge shift is not possible. Since the adverse effect of is mitigated, more accurate information can be reproduced.

Although the magnitude of the stray magnetic field acting on the domain wall displacement layer from the memory layer at the Curie temperature Tc2 also depends on the length of the recording mark, the magnitude of the saturation magnetization Ms or the film thickness of the memory layer is adjusted. It can also be adjusted by doing. It can also be adjusted by changing the distance between the memory layer and the domain wall motion layer by adjusting the film thickness of the blocking layer. The magnitude of the stray magnetic field acting on the domain wall displacement layer,
The influence of stray magnetic fields from layers other than the memory layer should also be taken into consideration when designing the direction.

Further, at the Curie temperature Tc2, the same effect can be obtained even if the composition of the domain wall displacement layer and the memory layer is made to have a dominant transition metal element sublattice magnetization. However, it is difficult to find a practical composition range because the saturation magnetization of a composition in which the transition metal element sublattice magnetization is dominant tends to change rapidly with temperature. Therefore, from the practical point of view, it is preferable that the composition of the domain wall motion layer and the memory layer at the Curie temperature Tc2 is dominant in the rare earth element sublattice magnetization.

Further, the compensation temperature (Tcomp) of the memory layer is
When 3) is set to the Curie temperature (Tc2) of the blocking layer or more and the Curie temperature of the memory layer (Tc3) or less, the memory layer in the aperture region is dominated by the rare earth element sublattice magnetization in the region below Tcomp3. is there. If the length of this region in the domain wall movement direction is longer than the maximum recording mark length, the memory layer in the aperture region can generate a stray magnetic field whose magnitude varies depending on all the mark lengths. On the other hand, at the time of recording, the influence of the stray magnetic field on the recording mark increases as the previously recorded mark increases, but the longer the mark length, the greater the distance from the center of the recording magnetic domain. The change in size becomes slower. That is, the difference between 0.5 μm and 0.6 μm is not as great as the difference between 0.1 μm and 0.2 μm. Therefore, if a stray magnetic field corresponding to the mark length is generated near the shortest mark, it may be constant when the mark length is long. Therefore, the length of the region from Tc2 to Tcomp3 is required to be longer than the shortest mark length, but not necessarily longer than the maximum mark length.

Based on the above points, the compensation temperature Tcomp3
Is a temperature distribution formed on the medium from the linear velocity of the disc and the reproducing power intensity, and the required Tc2 or more and Tco
It may be set to a temperature region where the length of the region of mp3 or less can be secured.

When actually recording information using domain wall motion reproduction, there is a problem of retransfer of magnetic domains (ghost signal) behind the spot.
This can be solved by adding a magnetic layer for adjusting the domain wall energy density as shown in No. 187898.

As described above, when the optical disk of the present invention is used, when the magnetic domain near the temperature Tc2, which is located substantially at the front edge of the reproducing laser beam, is expanded into the laser spot and is reproduced, the edge generated at the time of recording The shift can be canceled, and even when the linear recording density is increased, the error due to the edge shift can be removed and the information recording / reproducing can be performed at a high error rate.

[0039]

EXAMPLES Specific examples of the present invention will be described in detail below. <Experimental Example 1> For a DC magnetron sputtering device,
B-doped Si, and Gd, Tb, Fe, Co, Al
Each target was attached and the polycarbonate substrate having the guide groove for tracking was fixed to the substrate holder, and then the chamber was evacuated by a cryopump until a high vacuum of 1 × 10 ⁻⁵ Pa or less was obtained. While evacuating, Ar gas was introduced into the chamber until the pressure reached 0.5 Pa, and while rotating the substrate, the target was sputtered to form each layer as follows. In addition, SiN
At the time of forming the layer, N ₂ gas was introduced in addition to Ar gas, and the film was formed by DC reactive sputtering.

First, a SiN layer having a thickness of 90 nm is formed as an underlayer.
A film was formed. Subsequently, GdFeCoA was used as the domain wall displacement layer.
The L layer has a thickness of 30 nm, and Tb is used as a domain wall energy adjustment layer.
Fe 5 nm, TbFeAl layer as a blocking layer 10
nm, and a TbFeCo layer as a memory layer was sequentially formed to have a film thickness of 60 nm. Finally, a SiN layer of 50n is used as a protective layer.
m was formed into a film.

Each magnetic layer is composed of Gd, Tb, Fe, Co, A
The composition ratio was controlled by the ratio of the power applied to each of the targets. The Curie temperature (Tc1) of the domain wall displacement layer is 3
Adjust so that the temperature is 00 ℃ and the compensation temperature is about 270 ℃.
The Curie temperature (Tc2) of the blocking layer is 155 ° C., the Curie temperature (Tc3) of the memory layer is 320 ° C., and the compensation temperature (Tc
It was adjusted so that omp3) was about 180 ° C.

At a temperature lower than the compensation temperature with the compensation temperature as a boundary, the rare earth element sublattice magnetization becomes dominant, and at a temperature higher than the compensation temperature, the transition metal element sublattice magnetization becomes dominant. Therefore, in the above composition, the domain wall displacement layer and the memory layer are predominant in the rare earth element sublattice magnetization at the Curie temperature of the blocking layer. While rotating this disk at a linear velocity of 3 m / s, a laser beam having a wavelength of 680 nm and 250 O
When information recording / reproduction was performed using the external magnetic field of e,
(1-7) bER5 with the shortest bit length of modulation of 0.09 μm
E-5 was obtained.

In this experimental example, in order to smoothly move the magnetic domain wall, the groove portion was annealed with a high-power laser prior to the information recording / reproducing, and a treatment was performed so that the magnetic domain wall did not occur on the track side portion.

<Experimental Example 2> On the same substrate as in Experimental Example 1, as shown in FIG. 4, a GdFeCoCr layer (Tc4 = 340) was formed as an assist layer for increasing the magnetic field sensitivity during recording.
C., compensation temperature 220.degree. C.) A laminated film was prepared in the same manner as in Experimental Example 1 except that a film thickness of 20 nm was added on the surface of the memory layer opposite to the surface adjacent to the blocking layer.

The characteristics of this assist layer are that the Curie temperature is higher and the coercive force at room temperature is smaller than that of the memory layer. Recording on this medium is performed by transferring a magnetic domain to the memory layer by means of exchange coupling by an assist layer oriented in the direction of the external magnetic field at a temperature higher than the Curie temperature of the memory layer.

When the assist layer is provided, the magnitude and direction of the stray magnetic field applied to the domain wall displacement layer is the magnitude and direction of the stray magnetic field of the assist layer and the memory layer. Become. Therefore, it is necessary to determine the saturation magnetization and the film thickness of the assist layer so that the stray magnetic field generated by the assist layer does not change the direction of the stray magnetic field generated by the memory layer or extremely weakens the magnetic field strength.

In this embodiment, the combined stray magnetic field of the assist layer and the memory layer is in the same direction as the stray magnetic field of the memory layer in Experimental Example 1 in the vicinity of Tc2.
With this medium, the same effect as in Experimental Example 1 was obtained. When information was recorded / reproduced using a laser beam having a wavelength of 680 nm and an external magnetic field of 150 Oe while rotating at a linear velocity of 3 m / s, (1-7 ) Minimum bit length of modulation 0.09
bER3E-5 was obtained at μm.

<Experimental Example 3> The same laminated film as in Experimental Example 2 was used.
It was formed on a substrate having a deep land / groove step. As a result, the side of the track is magnetically divided at the same time as the film formation,
The annealing treatment with the high-power laser performed in Experimental Example 1 was omitted.

FIG. 5 is a sectional view of the optical disk of this experimental example, in which a rectangular guide groove having a depth of 160 nm is formed on the substrate 101. A film was formed on this substrate with the same film formulation as in Experimental Example 2. To be precise, a film is slightly deposited on the taper portion, but the film thickness is much smaller than that on the land / groove portion, so magnetic coupling at the step portion can be ignored.

When information recording / reproducing was performed on this disk with the same optical head as in Experimental Example 2, a reproduction signal equivalent to that in Experimental Example 2 was obtained, and by performing land / groove recording, recording density in the track pitch direction was obtained. Could also be improved.

<Comparative Experimental Example> With substantially the same structure as in Experimental Example 1, only the memory layer has a Curie temperature (Tc3) of 320.
C., and the compensation temperature was adjusted to about 130.degree. While rotating this disc at a linear velocity of 3 m / s,
Information recording / reproduction was performed using a laser beam of 0 nm and an external magnetic field of 250 Oe. As the basic characteristics of the disc,
The jitter value when recording a single mark length of 0.15 μm was 3.0 ns, which was almost the same as in Experiment 1, but a random pattern was obtained by (1-7) modulation with the shortest bit length of 0.09 μm. In the case of recording, the jitter value was deteriorated due to intersymbol interference, and only bER3E-4 was obtained.

[0052]

As described above in detail, by using the magneto-optical recording medium according to the present invention, it is possible to greatly improve the information recording density on the medium, and further, the edge shift occurring during recording and the reproducing time during recording. Since the generated edge shifts cancel each other out, an accurate reproduction signal can be obtained even for minute recording magnetic domains, and the recording / reproducing device with the same configuration as the conventional one can be used without complicating the device and increasing the cost. In addition, it has become possible to increase the capacity of the medium.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the first embodiment of the present invention.

FIG. 3 is an operation waveform of the first embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of the second embodiment of the present invention.

FIG. 5 is a sectional view of a substrate used in a third embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between a demagnetizing field and an edge shift during recording.

[Explanation of symbols]

1 Domain wall moving layer 2 barrier layer 3 memory layers 4 Assist layer 101 substrate 102 interference layer 103 protective layer

Claims (5)

[Claims] 1. A magnetic domain wall moving layer that contributes to reproduction of information and in which a magnetic domain wall moves, a memory layer that holds a recording magnetic domain according to information, and a magnetic domain wall moving layer disposed between the moving layer and the memory layer. A cutoff layer having a low Curie temperature is provided, and by reproducing the information by moving the domain wall of the recording magnetic domain transferred from the memory layer to the moving layer in the region of the Curie temperature of the blocking layer or higher, the recording domain is expanded. The magneto-optical recording medium to be performed is characterized in that the stray magnetic field generated from the memory layer acts in a direction of impeding the movement of the domain wall in the domain wall moving layer at least at the Curie temperature of the blocking layer. 2. Each layer is made of a rare earth-iron group amorphous alloy, and the domain wall motion layer and the memory layer are configured to have a dominant rare earth element sublattice magnetization at the Curie temperature of the blocking layer. The magneto-optical recording medium according to claim 1. 3. The domain wall displacement layer has a rare-earth element sublattice magnetization dominant even at room temperature.
The magneto-optical recording medium described in. 4. An assist layer is provided adjacent to the side of the memory layer opposite to the side in contact with the blocking layer for increasing the magnetic field sensitivity at the time of recording, and the stray magnetic field is provided between the memory layer and the assist layer. The magneto-optical recording medium according to claim 1, which is a sum of stray magnetic fields. 5. The magnetic domain wall displacement layer is characterized in that magnetic coupling is separated between each information track.
The magneto-optical recording medium described in.