JPH09106586A - Magneto-optical recording medium and information recording and reproducing method for the medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to embody information reproduction stable to external magnetic films with a good signal grade. SOLUTION: At least a reproducing layer 3 and a memory layer 5 are laminated on a substrate formed with grooves 9 and lands 8 for guiding information tracks. At least either of the lands 8 and the grooves 9 of this magneto-optical recording medium are initialized at a prescribed frequency prior the information recording.

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 optically recording and reproducing information using a light beam, and an information recording / reproducing method using the medium.

[0002]

2. Description of the Related Art Conventionally, various proposals have been made as a technique for optically recording and reproducing information. ROMs (playback only) are roughly classified according to the information recording and playback methods.
Type, WORM (additional write) type, and R / W (rewritable) type. Each of these three types of media uses a transparent material such as glass or a resin such as polycarbonate as a substrate, and is classified by the difference in the material to be coated and formed on the substrate. That is, a ROM type using a substance having a high reflectance and a high thermal stability such as Al on a substrate, and a WORM using a material that causes an irreversible reaction by heat such as an organic dye.
It is an R / W type that uses a material that causes a reversible reaction thermally and magnetically, such as a mold, a magnetic material, or a phase change material (which can be in a crystalline or amorphous state).

On the other hand, optical information recording media can be roughly classified into disc type, card type and tape type according to their shapes. Each has its own characteristics and can be used depending on the application. Among them, the disk type is the most popular because it excels in high-speed information transfer.

FIG. 13 is a schematic sectional view showing an example of a magneto-optical recording medium which is a conventional R / W type optical disc. The main part of the medium is composed of three layers of a first magnetic layer 3 (hereinafter referred to as a reproducing layer), an intermediate layer 2, and a second magnetic layer 5 (hereinafter referred to as a memory layer). The memory layer 5 is, for example, TbFeCo
In a film having a large perpendicular magnetic anisotropy such as or DyFeCo, recorded information forms and holds a magnetic domain depending on whether the magnetization of this layer is upward or downward with respect to the film surface. The reproducing layer 3 is a film having a small coercive force such as GdFeCo and a high Curie temperature. The intermediate layer is a layer made of a dielectric material such as SiN. Information reproduction is performed by a read laser beam in which the memory layer 5 and the reproducing layer 3 are coupled by a static magnetic field generated from magnetic domains recorded in the memory layer 5. Information recording / reproduction is possible even if the reproduction layer and the intermediate layer are omitted, that is, even if the memory layer is a single layer, but in that case, it is difficult to achieve both recording sensitivity and signal quality. Therefore, it is generally adopted to combine a memory layer that can normally record information with low power and a reproducing layer that can reproduce information with high CNR.

Further, in order to record information on a magneto-optical recording medium as shown in FIG. 13, a laser beam having a relatively high power is irradiated to a recording position to raise the temperature of the memory layer to near the Curie temperature. And at the same time apply an external magnetic field,
In the process of cooling the memory layer, the magnetization is made to follow the direction of the external magnetic field. Specifically, two types of methods, optical modulation recording and magnetic field modulation recording, are generally used. The optical modulation recording is a method of modulating the laser intensity according to the recording information while keeping the direction of the external magnetic field constant, and recording is performed by reversing the magnetization in the direction of the external magnetic field only in the portion irradiated with the high power laser. This method is advantageous in terms of high speed of laser modulation, but requires an erasing operation to reverse all magnetizations prior to recording. On the other hand, in the case of magnetic field modulation recording, the laser is continuously set to high power, and the direction of the magnetic field is changed depending on the recorded information. This method enables recording irrespective of the history of magnetization of the memory layer, that is, overwriting is possible and is also advantageous for increasing the recording density.

[0006]

However, in the case where the magnetic domain recorded in the memory layer and the reproducing layer are magnetostatically coupled as described above, the magnetostatic coupling force varies depending on the size of the recording mark. There was a point. This will be described with reference to FIG.

FIG. 14 is a result of calculating the magnitude Hst of the static magnetic field generated by the cylindrical magnetic domain and the rectangular parallelepiped magnetic domain. The curve (i) shows the upper 3 of the cylindrical magnetic domain (b) having a diameter of 0.4 μm, a thickness of 30 nm and a saturation magnetization of 200 emu / cc.
It represents the strength of the static magnetic field at 0 nm. Thus, it can be seen that a static magnetic field of about 300 Oe exists even near the center of the magnetic domain, although it has a peak near the domain wall.
On the other hand, in the case of the rectangular parallelepiped magnetic domain (c) shown in the curve (ii) having 1.6 × 0.8 μm, thickness of 30 nm, and saturation magnetization of 200 emu / cc, the static magnetic field becomes weak as a whole and the magnetic field near the center of the magnetic domain. Since the static magnetic field works only about 100 Oe, the transferability of the magnetic domain from the memory layer to the reproducing layer is deteriorated,
Further, it can be seen that there is a problem in stability with respect to an external magnetic field.

[0008]

In view of the above problems, the present invention provides a magneto-optical recording in which at least a reproducing layer and a memory layer are laminated on a substrate on which grooves and lands for guiding information tracks are formed. In the medium, the reproducing layer has a Curie temperature higher than the Curie temperature of the memory layer, the reproducing layer and the memory layer are magnetostatically coupled to each other in at least a part of an information reproducing spot, and on the land and the above. At least one of the grooves is initialized at a predetermined frequency, and a magneto-optical recording medium is used.

Further, according to the present invention, at least a reproducing layer and a memory layer are laminated on a substrate on which grooves and lands for guiding information tracks are formed, and the reproducing layer has a Curie temperature higher than the Curie temperature of the memory layer. A method for recording / reproducing information on / from a magneto-optical recording medium having a temperature, wherein the reproducing layer and the memory layer are magnetostatically coupled to each other in at least a part of an information reproducing spot, and prior to recording the information. The information recording / reproducing method is characterized in that at least one of the land and the groove of the memory layer is initialized at a predetermined frequency.

[0010]

The present invention will be described in detail below with reference to the drawings, but the present invention is not limited to these embodiments.

Example 1 FIG. 1 is a schematic sectional view of an optical disk according to the first example. As shown in FIG. 1, the optical disc has an interference layer 2 and a first magnetic layer (hereinafter referred to as a reproducing layer) on a substrate 1.
3, a dielectric layer (hereinafter referred to as an intermediate layer) 4, a second magnetic layer (hereinafter referred to as a memory layer) 5, a protective layer 6, and a protective coat layer 7 are laminated in this order. The substrate 1 is usually made of a transparent material such as glass or resin such as polycarbonate, and is provided with irregularities which serve as guide grooves for information tracks. Each layer laminated on the substrate 1 can be deposited by continuous sputtering using a magnetron sputtering device, continuous vapor deposition, or the like. The interference layer 2 is provided to enhance the magneto-optical effect, and includes, for example, Si ₃ N ₄ , AlN,
A transparent dielectric material such as SiO ₂ , SiO, ZnS, MgF ₂ is used. The protective layer 6 is used to protect the magnetic layer, and the same material as the interference layer 2 is used.
Since the interference layer 2 and the protective layer 6 are irrelevant to the essence of the present invention, they may be omitted in the configuration, and detailed description thereof will be omitted here. The protective coat 7 is provided to float a magnetic field head for performing magnetic field modulation recording on the surface of the medium, and an ultraviolet curable resin or the like is used.

The memory layer 5 is a layer for holding recorded information,
It is necessary to be able to stably hold minute magnetic domains of 1 μm or less. As a material of the memory layer 5, a material having a large perpendicular magnetic anisotropy and capable of maintaining a stable magnetization state, for example, Tb
Rare earth-iron group amorphous alloy such as FeCo, DyFeCo, TbDyFeCo, garnet, or platinum group-iron group periodic structure film, for example, Pt / Co, Pd / Co, or platinum group-iron group alloy, for example, PtCo, PdCo, etc. May be The Curie temperature of the memory layer 5 is a characteristic directly related to the laser power required for recording information, and if it is too high, the recording sensitivity deteriorates.
The temperature is more preferably 240 ° C. or lower.

The reproducing layer 3 is a layer responsible for reproducing the magnetization information held in the memory layer 5, and is located closer to the incidence of light than the memory layer 5, so that the Kerr rotation angle does not deteriorate during reproduction. The Curie temperature is at least higher than that of the memory layer 5, preferably 270 ° C. or higher, more preferably 300 ° C.
Above is good. The reproducing layer 3 is a rare earth-iron group element amorphous alloy having a small perpendicular magnetic anisotropy, specifically, GdFeCo.
Is desirable. Further, a light rare earth metal such as Nd, Pr or Sm may be added to this to increase the Kerr rotation angle at a short wavelength.

Further, the reproducing layer 3 and the memory layer 5 may be added with elements such as Al, Ti, Pt, Nb and Cr in order to improve the corrosion resistance, and Al and Ti in order to improve the thermal conductivity.
A layer having good thermal conductivity such as AlTa, AlTi, AlCr, or Cu may be provided so as to be in contact with the reproducing layer 3 or the memory layer 5.

The intermediate layer 4 is a dielectric layer provided for the purpose of blocking exchange coupling between the memory layer 5 and the reproducing layer 3, and the same material as the interference layer 2 and the protective layer 6 is used to simplify the manufacturing apparatus. Is desirable. As a result, the memory layer and the reproducing layer are coupled only by magnetostatic coupling.

FIG. 2 shows the magnetization direction of each magnetic layer in this embodiment. In the figure, the white portion is the downward magnetization and the hatched portion is the upward portion. The recording information is recorded on the land by magnetic field modulation recording, and the high frequency repetitive signal is uniformly recorded on the groove by initialization.

The reason why the transferability of the magnetic domain from the memory layer 5 to the reproducing layer 3 is improved by orienting the magnetization as shown in FIG. 2 will be described with reference to FIGS. 3 and 4. In the following description, recording is performed on the land and the initialization operation is performed on the groove, but conversely, if the initialization operation is performed on the land and information is recorded on the groove, no problem will occur. It is clear that there is nothing.

FIG. 3A is a schematic view of a medium which is not subjected to the initialization process in the present invention, and here shows a case where the magnetization on the groove 9 is uniformly followed in the same direction, for example, downward. There is. A relatively small upward magnetization (hereinafter referred to as a recording mark 10) on the land 8 of such a medium.
Is recorded with a relatively large interval (downward magnetization, hereinafter referred to as blank). In FIG. 3B, the magnetization direction of the memory layer 5 along the line AA ′ in the track direction of FIG. 3A and the magnitude of the static magnetic field generated by the memory layer 5 (H
st), which is large on the recording marks 10 as shown in the figure and is small between the marks, particularly near the intermediate point C.
This is a sectional view taken along the line BB 'in the radial direction.
As is clear from comparison with FIG. 14C, when considering the static magnetic field generated from the blank portion between the recording marks, the groove portions on both sides are also in the same direction as the blank, so that FIG.
Since it is equivalent to the case of the large mark described in 1), the static magnetic field becomes smaller as the blank becomes larger and closer to the center of the blank. Therefore, in the case of FIG. 3, the recording mark recorded in the memory layer 5 is transferred to the reproducing layer 3, but the magnetostatic coupling force is weak in the blank portion other than the mark, and the transferability deteriorates. Maze is likely to occur, and the transferability tends to decrease particularly when an external magnetic field is applied.

On the other hand, in the example of the present invention, as shown in FIG. 4, the groove 9 is preliminarily initialized at a high frequency. In this case, the track direction is almost the same as the conventional example of FIG. However, considering the radial direction in the portion where the adjacent groove is magnetized upward, that is, considering the cross section taken along line BB ′ shown in FIG. 4C, the minute marks described in FIG. 14 are arranged. Can be considered equivalent. That is, a sufficient magnetic field necessary for transfer can be obtained. In addition, FIG. 4 showing the radial direction in the portion where the magnetization of the adjacent groove is downward.
Considering the cross section taken along the line DD ′ shown in (d), a magnetic field having a sufficient magnitude is obtained in the adjacent groove, and therefore the magnetic field becomes larger than the conventional one even near the center of the blank.

In the above description, the upward magnetization is referred to as a mark and the downward magnetization is referred to as a blank. However, in the case of magnetic field modulation recording, there is no distinction between the mark and the blank depending on the magnetization direction. Therefore, since the magnetization of the adjacent groove is modulated at a high frequency with a duty cycle of about 50%, even if the mark or blank on the land becomes long, a static magnetic field having a sufficient size for transferring the magnetic domain in the vicinity of the center of the mark or blank. A magnetic field can be generated without any difference due to polarity. As a result, the magnetostatic coupling force between the memory layer and the reproducing layer is increased, so that the signal quality is improved and the signal is not disturbed by the external magnetic field. The higher the frequency of groove initialization, that is, the smaller the recording mark, the greater the effect.Therefore, it is desirable to record at the frequency corresponding to the shortest mark when actually recording a mark as information, and there is a margin for speeding up the modulation frequency. If so, recording may be performed at a higher frequency.

Actually, in order to realize the magnetized state as in this example, the same operation as the normal recording operation may be performed on the land or groove. That is, a tracking servo is applied to the groove on the land recording disk, and the external magnetic field is modulated at a high frequency while increasing the laser power to such an extent that the memory layer reaches the Curie temperature.
The groove initialization operation is completed by tracing the entire circumference of the disk as it is. Then, the polarity of the tracking servo is reversed to perform tracking, and the normal recording / reproducing operation is performed.

This operation may be performed only once from the time the disc is created to the time the first information is recorded. If this operation is performed at the time of shipping inspection of the product or prior to the normal initialization process of the disc, the present invention is performed. It is possible to achieve the magnetization state that is the main point of.

FIG. 5 shows the present invention in which a mark having a length of 0.8 μm is recorded on a magneto-optical recording medium by magnetic field modulation recording.
It is the result of measuring the external magnetic field stability of the conventional example which is not processed. Even when the conventional groove is erased in the same direction, when the external magnetic field is 0, about 50 dB, which is sufficient C
Although NR is obtained, it can be seen that when an external magnetic field is applied, the magnetic field is particularly weak against the magnetic field on the side opposite to the groove erasing, and stable magnetic domain transfer is not performed in the blank portion of the recording mark. On the other hand, when the initialization process of modulating the magnetized state of the groove with a high frequency as in the present invention is performed, the stability is increased against an external magnetic field in either direction, and the high CN
R is obtained.

In the present embodiment, the recording method on the magneto-optical recording medium has been described as the magnetic field modulation recording, but in the case of the optical modulation recording as well, although the shape of the recorded magnetic domain is different (magnetization in the erasing direction). A circular or elliptical magnetic domain in the recording direction is formed in the inside), and stabilization of information reproduction can be realized for the same reason. In other words, this means that in the magneto-optical recording medium of the present invention, regardless of the recording method or recording magnetic domain shape,
This indicates that stable information reproduction is possible at all times.

As described above, in the magneto-optical recording medium of the present invention, the magnetostatic coupling force between the memory layer and the reproducing layer can be easily increased, and the transferability independent of the recording pattern can be obtained. The quality is improved and stable information reproduction can be realized even with respect to an external magnetic field.

Embodiment 2 Another example of the present invention will be described with reference to FIG. In the optical recording medium shown in FIG. 6, the reproducing layer 3 is changed from the in-plane magnetized film to the perpendicular magnetized film in accordance with the temperature change, and at this time, the transfer of the magnetic domain by the magnetostatic coupling with the memory layer 5 is used to make the aperture 16. By performing super-resolution reproduction in which the information is reproduced only in a part of the information reproduction spot 11, it is possible to reproduce the minute mark 10 below the diffraction limit of the reproduction light.

FIG. 6 shows the state of spots and the magnetized state of each magnetic layer when the disc moves rightward while irradiating the optical disc of this embodiment with laser light.
In FIG. 6A, the black arrows in the magnetic layers 3 and 5 indicate the direction of the iron group element sublattice magnetization, and the outlined arrows indicate the net direction of the magnetization. At this time, the disk is moving at about 5 to 15 m / s, and the position where the film temperature is maximum is behind the center of the laser spot (on the right side in FIG. 6B) due to the heat accumulation effect of laser irradiation. )become. Also,
The temperature distribution at the track center is shown in FIG.

FIG. 7 is a diagram showing the temperature dependence of the anisotropic energy of the reproducing layer 3. In this embodiment, since the saturation magnetization Ms ₁ is relatively large due to the rare earth element sublattice magnetization predominant at room temperature, the saturation magnetization sharply decreases toward the compensation temperature between the Curie temperature, and thus the magnetization is filmed. The energy 2πMs ₁ ^{2 to} be directed in the plane also sharply decreases from room temperature toward the compensation temperature. On the other hand, the perpendicular magnetic anisotropy Ku ₁ of the reproducing layer 3 gradually decreases from room temperature to the Curie temperature. At this time, when the energy and the magnetization direction of the reproducing layer are 2πMs ₁ ² > Ku ₁ (1), the magnetization of the reproducing layer 3 is in the film plane. That is, as the temperature of the magnetic layer is increased, the in-plane magnetized film changes to the perpendicular magnetized film with the temperature of Tth ₁ as the boundary, as shown in FIG. FIG. 8 shows the temperature dependence of the Kerr rotation angle due to the polar Kerr effect of the reproducing layer 3. Since the film is an in-plane magnetized film near room temperature, the Kerr rotation angle θk hardly appears, and when the temperature rises to Tth ₁ , the magnetization of the reproducing layer 3 makes a vertical transition and the Kerr rotation angle suddenly appears. Therefore, in the temperature region below Tth ₁ , the Kerr rotation angle is almost 0, so that it does not contribute to information reproduction (front mask 15 in FIG. 6B), and the portion above Tth ₁ (aperture 16 in FIG. 6B). Since the information can be reproduced only by the Kerr effect, it is substantially equivalent to the case where the information is reproduced only in a small area of Tth ₁ or more.

As described above, also in the magneto-optical recording medium of this embodiment, magnetostatic coupling is used to transfer the magnetic domain from the memory layer to the reproducing layer although it is a part of the spot. Therefore, as described in the first embodiment, it is important to generate a stable static magnetic field from the memory layer. Therefore, when information is recorded on the land 8, the groove 9
By modulating the magnetizations on a and 9b with a high frequency, a large effect can be obtained as in the first embodiment.

Third Embodiment A third embodiment of the present invention will be described with reference to FIG.

The structure of the medium of this embodiment is almost the same as that of the second embodiment. The difference from the second embodiment is that the magnetic domain transferred to the reproducing layer 3 disappears when the temperature rises above a predetermined temperature Tth ₂ to form a rear mask 17, resulting in a double mask type super-resolution. A phenomenon in which the magnetic domains disappear in the rear mask will be described with reference to FIG.

FIG. 10 shows a state in which the magnetic domain of the memory layer 5 is transferred to the reproducing layer 3, and the three magnetic fields in the figure are applied to the transferred magnetic domain. First, Hleak is a leakage magnetic field generated from the magnetic domain in the erasing direction of the reproducing layer 3, and the magnetic circuit is closed when the magnetic domain is being transferred, so that it acts in the direction of promoting the transfer of the magnetic domain. Hwb is a magnetic field generated by Bloch domain wall energy, and is specifically expressed by Hwb = σwb / 2Ms ₁ r (2). Here, σwb is the Bloch domain wall energy, and r is the radius of the magnetic domain. Since the Bloch domain wall energy is energetically stable in the direction in which the volume of the Bloch domain wall decreases, Hwb is the direction in which the transferred magnetic domain contracts. These magnetic fields and the static magnetic field H from the memory layer 5
Considering the energy balance including st, when Hst + Hleak> Hwb (3) holds, the magnetic domain of the memory layer 5 is increased when the reproducing layer 3 makes a transition from the in-plane magnetization film to the perpendicular magnetization film while increasing the temperature. Are transferred to the reproduction layer 3. On the contrary, when the expression (3) is not satisfied, the recording magnetic domain is not transferred to the reproducing layer 3, and the magnetic domain of the reproducing layer 3 is uniformly oriented in the erasing direction regardless of the memory layer 5.

The temperature Tth ₂ shown in FIG. 9 is a boundary temperature at which the equation (3) is satisfied. Below Tth ₂ , the condition (3) is satisfied, and when it exceeds Tth ₂ , the temperature is not satisfied. That is, Tt
At temperatures between h ₁ and Tth ₂ , the magnetization of the reproducing layer is perpendicular and at the same time magnetic domains are transferred by magnetostatic coupling with the memory layer. When the temperature exceeds Tth ₂ , the Bloch domain wall energy becomes dominant. The recording magnetic domain transferred from the memory layer cannot be held in the reproducing layer, and the recording magnetic domain is uniformly oriented in the erasing direction. As a result, the super resolution becomes a double mask structure.

In the case of this embodiment, the magnetic domains that disappear in the rear mask 17 must be surrounded by the magnetization in the erasing direction. Therefore, in the case of normal optical modulation recording, the erasing operation is performed prior to recording to form the recording mark 10 within the range of the erasing width, but there is no problem. However, if recording is performed to the full track width by magnetic field modulation recording, Therefore, the groove must be initialized by high-frequency recording, the lands should be oriented uniformly in the erasing direction, and the subsequent recording operation should be performed with a width narrower than the erasing width.

Also in this embodiment, since magnetostatic coupling is used to transfer the magnetic domain from the memory layer to the reproducing layer,
Stable information reproduction can be performed by performing the initialization process in the present invention.

Fourth Embodiment A fourth embodiment of the present invention will be described with reference to FIG.

The structure of the medium of this embodiment is almost the same as that of the second embodiment, except that the intermediate layer 4 is made of a magnetic material. The action of the magnetic intermediate layer 4 is the following two. (1) In the temperature range from room temperature to the Curie temperature Tc ₃ of the intermediate layer 4, the interface domain wall energy between the reproducing layer 3 and the memory layer 5 is relaxed, and the reproducing layer 3 serves as an in-plane magnetized film. . As a result, this also contributes to the reduction in the thickness of the reproducing layer 3. (2) Above the Curie temperature Tc ₃ of the intermediate layer 4, the exchange coupling between the reproducing layer 3 and the memory layer 5 is broken.

In order to achieve these objects, the intermediate layer 4
Curie temperature Tc ₃ is higher than room temperature and lower than Curie temperatures Tc ₁ and Tc _{2 of} the reproducing layer 3 and the memory layer 5. The Curie temperature Tc ₃ of the intermediate layer 4 is low enough to break the exchange coupling force with a light spot having a power at the time of reproduction, specifically, 80 ° C. to 220 ° C. is preferable, and 100 ° C. to 180 ° C. is more preferable. The following is good. The material of the intermediate layer 4 is, for example, a rare earth-iron group amorphous alloy, specifically Gd.
Fe or GdFeCo is preferable. Further, in order to reduce the Curie temperature, a non-magnetic element such as Cr, Al, Si, Cu may be added.

According to this embodiment, as shown in FIG. 11, the temperature Tt at which the reproducing layer 3 transitions from the in-plane magnetized film to the perpendicular magnetized film.
The h ₁ is that you almost close temperature and the Curie temperature Tc ₃ of the intermediate layer, the front mask 15 is at Tc ₃ below, Tc ₃
With the above, the aperture 16 can be formed by magnetostatic coupling, and thus super-resolution reproduction of a minute magnetic domain becomes possible.
Also in this case, stable information reproduction can be performed by modulating the magnetization on the groove with a high frequency. Strictly speaking,
If the medium composition is determined so that Tc ₃ = Tth ₁ , super-resolution reproduction can be performed most efficiently, but −30 ≦ Tth ₁ −Tc ₃
Within the range of ≦ 50, information can be reproduced without significantly impairing the super-resolution effect.

In this embodiment, too, it is no wonder that the super-resolution can be made into a double mask structure by forming a rear mask according to the same principle as that of the third embodiment by using the higher temperature portion.

Fifth Embodiment A fifth embodiment of the present invention will be described with reference to FIG.

In this embodiment, information is recorded on both the land and the groove in order to increase the recording capacity of the optical disc. Also in this case, if the direction of magnetization in the erasing direction is made uniform over the entire surface of the disk, the blank pattern is weakly coupled due to the recording pattern. Therefore, prior to the first recording operation, recording processing is performed on both the land and the groove in advance at a high frequency. As a result,
Stable information reproduction is possible regardless of which groove is used for recording.

It is needless to say that this embodiment is applicable to the film structures described in all the above embodiments. In particular, when the film structure described in Examples 2 to 4 is adopted, not only is it possible to reproduce minute magnetic domains, but also the effect of suppressing crosstalk from adjacent tracks due to the masking effect of the in-plane magnetized film. Therefore, it is more suitable for this embodiment.

When a magnetic film having a double mask structure utilizing the disappearance of magnetic domains is adopted as in Example 3, both the land and the groove need to be provided with an erasing area slightly wider than the recording magnetic domain width. In this case, a region modulated with high frequency may be provided near the boundary between the land and the groove as in the present invention.

[0045]

By using the magneto-optical recording medium of the present invention, the magnetostatic coupling force between the magnetic layers is increased, and stable signal reproduction can be realized with good signal quality even against an external magnetic field. Also, by devising the film structure, it is possible to reproduce finer marks and increase the recording capacity of the information recording medium.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an information recording medium according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a magnetization state of a medium in the first embodiment of the present invention.

3A and 3B are diagrams for explaining a relationship between a conventional magnetized state and a static magnetic field generated, wherein FIG. 3A is a schematic diagram of a medium not subjected to an initialization process in the present invention, and FIGS. (A) Track direction AA 'line, radial direction B-
FIG. 6 is a diagram showing the magnetization direction of the memory layer 5 along line B ′ and the magnitude (Hst) of the static magnetic field generated by the memory layer 5.

FIG. 4 is a diagram for explaining a relationship between a magnetized state and a static magnetic field generated according to the present invention, in which (a) is a schematic diagram of a medium subjected to initialization processing according to the present invention, (b), (c), (D) shows the track direction AA 'line and the radial direction B of (a), respectively.
FIG. 6 is a diagram showing the magnetization directions of the memory layer 5 along the −B ′ line and the DD ′ line and the magnitude (Hst) of the static magnetic field generated by the memory layer 5.

FIG. 5 is a diagram showing external magnetic field stability of the information recording medium of the present invention.

6A and 6B are principle diagrams of a medium according to a second embodiment of the present invention, in which FIG. 6A is a schematic diagram showing the magnetization directions of the memory layer and the reproducing layer, and FIG. View from above, (c)
Indicates the temperature distribution at the track center of the reproducing layer 3.

7 is a graph showing the relationship between energy and temperature in the reproducing layer 3 of the medium of FIG.

8 is a graph showing the temperature dependence of the Kerr rotation angle of the reproducing layer 3 of the medium of FIG.

FIG. 9 is a principle diagram of a third embodiment of the present invention, (a)
Is a schematic diagram showing the magnetization directions of the memory layer and the reproducing layer, (b)
Shows a view of the reproducing layer 3 from above, and (c) shows a temperature distribution at the track center of the reproducing layer 3.

FIG. 10 is a diagram showing a magnetic field generated in a high temperature portion of a third embodiment of the present invention.

FIG. 11 is a principle diagram of a fourth embodiment of the present invention,
(A) is a schematic diagram showing the magnetization directions of the memory layer and the reproducing layer,
(B) is a view of the reproduction layer 3 seen from above, and (c) is a reproduction layer 3
The temperature distribution in the track center of is shown.

FIG. 12 is a principle view of the fifth embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view of a conventional information recording medium.

FIG. 14A is a graph showing the calculation result of the magnitude of the static magnetic field generated by the recording magnetic domain, and the curve (i) is the static magnetic field strength 30 nm above the cylindrical magnetic domain (b), and the curve (ii). ) Indicates the strength of the static magnetic field at 30 nm above the rectangular parallelepiped magnetic domain (c).

[Explanation of symbols]

 1 substrate 2 interference layer 3 reproducing layer 4 intermediate layer 5 memory layer 6 protective layer 7 protective coat 8 land 9 groove 10 recording mark 11 reproducing spot 15 front mask 16 aperture 17 rear mask

Claims (11)

[Claims] 1. A magneto-optical recording medium in which at least a reproducing layer and a memory layer are laminated on a substrate on which grooves and lands for guiding information tracks are formed, wherein the reproducing layer is a Curie temperature of the memory layer. Has a higher Curie temperature, the reproducing layer and the memory layer are magnetostatically coupled to each other in at least a part of the information reproducing spot, and at least one of the land and the groove is prior to recording information. , A magneto-optical recording medium which is initialized at a predetermined frequency. 2. The magneto-optical recording medium according to claim 1, wherein the frequency is the highest frequency used for information recording. 3. The magneto-optical recording medium according to claim 1, wherein the magnetic domain pattern of the portion initialized at the predetermined frequency has a duty cycle of about 50%. 4. The magneto-optical recording medium according to claim 1, further comprising an intermediate layer made of a dielectric material between the reproducing layer and the memory layer. 5. The magneto-optical recording medium according to claim 4, wherein the reproducing layer is an in-plane magnetized film at room temperature and transitions to a perpendicular magnetized film at a predetermined temperature or higher between room temperature and Curie temperature. . 6. The magneto-optical recording medium according to claim 1, further comprising an intermediate layer formed of a third magnetic layer between the reproducing layer and the memory layer. 7. The reproducing layer according to claim 6, which is an in-plane magnetized film at room temperature, is near a Curie temperature of the third magnetic layer, and has a predetermined value between room temperature and the Curie temperature of the reproducing layer. A magneto-optical recording medium characterized by transition to a perpendicular magnetization film at a temperature or higher. 8. The magneto-optical recording medium according to claim 1, wherein information is recorded and reproduced on both the land and the groove. 9. A substrate on which grooves and lands for guiding information tracks are formed, at least a reproducing layer and a memory layer are laminated, and the reproducing layer has a Curie temperature higher than the Curie temperature of the memory layer. A method for recording / reproducing information on / from a magneto-optical recording medium in which the reproducing layer and the memory layer are magnetostatically coupled to each other in at least a part of an information reproducing spot, wherein the memory is stored before recording the information. An information recording / reproducing method characterized in that at least one of the land and the groove of a layer is initialized at a predetermined frequency. 10. The information recording / reproducing method according to claim 9, wherein the frequency is the highest frequency used for information recording. 11. The information recording / reproducing method according to claim 9, wherein the initialization is performed at the predetermined frequency with a duty cycle of about 50%.