JPH07334878A - Magneto-optical recording medium and reproducing methof for information using that medium - Google Patents

Abstract

PURPOSE:To reproduce recording marks under the limit of diffraction of light with high signal quality by forming a simple structure which does not require an initializing magnetic field or reproducing magnetic field for reproducing. CONSTITUTION:On a substrate 20, an interference layer 14, first magnetic layer (as reproducing layer) 11, third magnetic layer (intermediate layer) 12, second magnetic layer (memory layer) 13, and protective film 15 are successively formed. The first magnetic layer 11 is an intraplane magnetization film at room temp. and becomes a perpendicularly magnetized film at temp. between room temp. and the Curie temp. This film is formed to have 20 to 100nm thickness. The second magnetic layer 13 is a perpendicularly magnetized film having larger coercive force and lower Curie temp. than the first magnetic layer 11 and recorded information is accumulated in this layer. The third magnetic layer 12 is formed to have Curie temp. lower than the Cure temp. of the first and second magnetic layers 11, 13, and to have a thickness between 3nm and 30nm. When the first magnetic layer 11 changes into a perpendicularly magnetized film at temp. between room temp. and Curie temp. of the third magnetic layer 12, exchange coupling occurs between the first magnetic layer 11 and the second magnetic layer 13 and the information stored in the second magnetic layer 13 is transferred. At temp. near the Curie temp. of the third magnetic layer 12, the first magnetic layer 11 is magnetized in one direction without affected by the information stored in the second magnetic layer 13.

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 and reproducing information by laser light, and more particularly to a magneto-optical recording medium capable of achieving high density and an information reproducing method for the medium. is there.

[0002]

2. Description of the Related Art As a rewritable high density recording system,
Using the thermal energy of a semiconductor laser to write magnetic domains in a magnetic thin film to record information, using the magneto-optical effect,
Attention has been paid to a magneto-optical recording medium for reading this information.
Further, in recent years, there is an increasing demand for increasing the recording density of this magneto-optical recording medium to make it a recording medium having a larger capacity.

The linear recording density of an optical disk such as this magneto-optical recording medium largely depends on the laser wavelength λ 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 reproduction light wavelength and the numerical aperture of the objective lens are determined, the minimum mark length of about λ / 2NA is the limit of reproduction. On the other hand, the track density is limited mainly by crosstalk between adjacent tracks and depends on the spot diameter of the reproducing beam as well as the shortest mark length.

Therefore, in order to realize high density in the conventional optical disk, it is necessary to shorten the laser wavelength of the reproducing optical system or increase the numerical aperture NA of the objective lens. However, it is not easy to shorten the laser wavelength due to problems such as element efficiency and heat generation. Also, increasing the numerical aperture of the objective lens not only makes it difficult to process the lens, but also increases the distance between the lens and the disc. Mechanical problems such as collision with the disk due to being too close to each other occur. For this reason,
Techniques have been developed for improving the recording density by devising the configuration of the recording medium and the reading method.

For example, in the magneto-optical recording medium disclosed in Japanese Patent Laid-Open No. 6-124500, a medium structure as shown in FIG. 17 is used as a super-resolution technique for realizing a recording density higher than the optical resolution of reproduction light. Is proposed. FIG. 17 (a) shows a cross-sectional view of an optical disc, which is an example of super-resolution technology. Board 20
Is usually a transparent material such as glass or polycarbonate, and has an interference layer 43, a reproduction layer 41, a memory layer 4 on the substrate 20.
2. The protective layer 44 is laminated in this order. The interference layer 43 enhances the Kerr effect, and the protective layer 44 is used for protecting the magnetic layer. The arrow in the magnetic layer indicates the direction of iron group element sublattice magnetization in the film.

The memory layer 42 is a film having a large perpendicular magnetic anisotropy, such as TbFeCo or DyFeCo, and recorded information is retained by forming magnetic domains depending on whether the magnetization of this layer is upward or downward with respect to the film surface. The reproducing layer 41 is made of a material having a large saturation magnetization Ms and a small perpendicular magnetic anisotropy, and has a composition in which the rare earth element sublattice magnetization is dominant. FIG. 18 shows an example of static characteristics of the reproduction layer 41. Although it is an in-plane magnetized film at room temperature, it has saturated magnetization as the temperature rises.
Ms gradually decreases, and when it reaches a predetermined temperature, the magnitude relationship between the perpendicular magnetic anisotropy Ku and 2πMs ² is reversed, so that the film becomes a perpendicular magnetization film. FIG. 18 shows the static characteristics of the reproducing layer alone. However, when laminated with the memory layer 42, an exchange coupling force with the memory layer 42 acts to form a perpendicular magnetic film at a lower temperature Tth, and a perpendicular magnetic film. At that time, the magnetization direction of the reproduction layer 41 is the direction exchange-coupled with the memory layer 42.

When information reproducing light is irradiated from the substrate 20 side to the disk having such a medium structure, the temperature gradient at the center of the data track becomes as shown in FIG. 17 (c).
When viewed from the 20 side, the Tth isotherm exists within the spot as shown in Fig. 17 (b). Then, as mentioned above, Tth
In the following portion, since the reproducing layer 41 becomes an in-plane magnetized film, it does not contribute to the polar Kerr effect (forming the front mask 4) and the information of the recording magnetic domain held in the memory layer 42 is masked and becomes invisible. On the other hand, in the portion above Tth, the reproducing layer 41 is a perpendicularly magnetized film, and the magnetization direction is the same as the recorded information due to exchange coupling from the memory layer 42. As a result, the information of the memory layer 42 is transferred only to the portion of the aperture 3 which is smaller than the size of the spot 2, so that super-resolution is realized.

Further, JP-A-3-93058 and JP-A-4-255.
The super-resolution reproducing method disclosed in Japanese Patent No. 946 uses a medium composed of a reproducing layer 31, an intermediate layer 32 and a memory layer 33 as shown in FIG. Prior to information reproduction, the magnetization direction of the reproduction layer 31 is aligned in one direction by the initialization magnetic field 21 to mask the magnetic domain information of the memory layer 33, and then the light spot 2 is irradiated. , Keep the reproducing layer 31 in the initialized state in the low temperature region (form the front mask 4),
Regeneration layer in the high temperature region above the Curie temperature Tc2 of the intermediate layer 32
31 is forcibly oriented in the direction of the reproducing magnetic field 22 (rear mask
5)), and the magnetic domain information of the memory layer 33 is transferred only in the medium temperature region to reduce the effective size of the reproduction spot, thereby making it possible to reproduce the recording mark 1 below the diffraction limit of light. , To improve the linear density.

In these known super-resolution systems, since the front mask 4 extends in the direction of the adjacent track in the low temperature region, an attempt is made to improve the track density as well as the linear recording density.

[0010]

However, in the super-resolution reproducing method disclosed in Japanese Patent Laid-Open No. 6-124500, only the front mask 4 is used. Therefore, when the area of the mask is widened to increase the resolution, the aperture 3 There was a problem that the signal quality was sacrificed due to the position of the point deviating from the center of the spot. In addition, JP-A-3-93058 and JP-A-4
In the method disclosed in the -255946 publication, the resolution can be increased without degrading the signal quality, but on the other hand, the magnetization of the reproduction layer 31 must be aligned in one direction prior to information reproduction, and the initialization magnet 21 for that purpose must be provided. It is necessary to add to the conventional device.

As described above, the conventional super-resolution reproduction method is
There are problems that the resolution cannot be sufficiently increased, the magneto-optical recording / reproducing apparatus becomes complicated, the cost becomes high, and the size reduction is difficult.

Further, Japanese Patent Application Laid-Open No. 4-255938 discloses Japanese Patent Application Laid-Open No. 3-93
In the super-resolution reproducing method disclosed in JP-A-058 and JP-A-4-255946, the film thickness of the reproducing layer of the magneto-optical recording medium so that the mask effect is optically good in a low temperature region or a high temperature region. Is disclosed.

However, when a magnetic layer exhibiting in-plane magnetic anisotropy at room temperature is used as the reproducing layer, in order to obtain a good mask effect, not only the optical effect but also the magnetic effect at room temperature and reproducing temperature is obtained. The design of the magneto-optical recording medium must be done taking the behavior into consideration.

In order to solve such a problem, the present invention has a simple structure which does not require an initializing magnetic field and a reproducing magnetic field at the time of reproducing, and makes a recording mark having a light diffraction limit or less with a high signal quality. An object of the present invention is to provide a reproducible magneto-optical recording medium and a magneto-optical reproducing method.

[0015]

[Means and Actions for Solving the Problems]
First in-plane magnetized film having a thickness of 20 nm or more and 100 nm or less that is an in-plane magnetized film at room temperature and becomes a perpendicular magnetized film between room temperature and Curie temperature.
A magnetic layer, a second magnetic layer formed of a perpendicular magnetization film having a coercive force higher than that of the first magnetic layer and a Curie temperature lower than that of the first magnetic layer, and the Curie temperature of the first magnetic layer and the second magnetic layer. Film thickness 3 with lower Curie temperature
a third magnetic layer having a thickness of 30 nm or more and 30 nm or less is laminated on a substrate in the order of the first magnetic layer, the third magnetic layer, and the second magnetic layer. When it becomes a perpendicularly magnetized film between the Curie temperatures of the magnetic layer, it exchange-couples with the second magnetic layer, the information stored in the second magnetic layer is transferred, and the Curie temperature of the third magnetic layer is near, This is achieved by a magneto-optical recording medium that is magnetized in one direction regardless of the information stored in the second magnetic layer.

Further, it is an in-plane magnetized film at room temperature and becomes a perpendicular magnetized film between room temperature and Curie temperature, and the film thickness is 20 nm or more and 10 or more.
A first magnetic layer having a thickness of 0 nm or less; a second magnetic layer having a coercive force larger than that of the first magnetic layer and a Curie temperature lower than that of the perpendicular magnetic layer for accumulating recording information; and the first magnetic layer and the second magnetic layer. A third magnetic layer having a Curie temperature lower than the Curie temperature of the magnetic layer and having a film thickness of 3 nm or more and 30 nm or less is laminated on a substrate at least the first magnetic layer, the third magnetic layer, and the second magnetic layer in this order. The first magnetic layer exchange-couples with the second magnetic layer when it becomes a perpendicularly magnetized film between room temperature and the Curie temperature of the third magnetic layer, and the information stored in the second magnetic layer is transferred. In the vicinity of the Curie temperature of the third magnetic layer, the magneto-optical recording medium magnetized in one direction regardless of the information stored in the second magnetic layer is irradiated with a light spot from the substrate side, Information stored in the second magnetic layer The information reproducing method of performing live, said at a high temperature portion of the irradiated light spot 3
By raising the temperature of the magnetic layer to near the Curie temperature, the magnetization of the first magnetic layer in the high temperature portion is magnetized in one direction, and the first magnetic layer is a perpendicular magnetization film in the intermediate temperature portion in the light spot, The first magnetic layer and the second
Information stored in the second magnetic layer is transferred to the first magnetic layer by exchange coupling with the magnetic layer, and the first magnetic layer is an in-plane magnetized film in a low temperature portion in the light spot. The information is reproduced by detecting the magneto-optical effect of the reflected light of the light spot.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The magneto-optical recording medium of the present invention and the information reproducing method using the medium will be described below in detail with reference to the drawings.

The magneto-optical recording medium of the present invention comprises a first magnetic layer which is a perpendicular magnetic film, a third magnetic layer having a Curie temperature lower than that of the first and second magnetic layers, and a second magnetic layer which is a perpendicular magnetic film. Of 3
At least a magnetic layer of the layer (FIG. 1). Hereinafter, the first magnetic layer is referred to as a reproducing layer, the second magnetic layer is referred to as a memory layer, and the third magnetic layer is referred to as an intermediate layer.

The memory layer 13 is a layer for storing recorded information,
It is necessary to be able to stably hold the magnetic domains. As a recording material, one having a large perpendicular magnetic anisotropy and capable of stably holding a magnetized state, for example, a rare earth-iron group amorphous alloy such as TbFeCo, DyFeCo, TbDyFeCo, garnet, or a platinum group-iron group periodic structure The film may be, for example, Pt / Co, Pd / Co platinum group-iron group alloy, such as PtCo or PdCo.

The memory layer 13 needs to have a thickness of 10 nm or more in order to keep the magnetic domains stable.
The total thickness of the three magnetic layers of the reproducing layer 11 and the intermediate layer 12 is preferably thin in order to reduce the recording power, and the thickness of the memory layer is preferably 50 nm or less.

The reproducing layer 11 is a layer responsible for reproducing the magnetization information held in the memory layer 13, is an in-plane magnetized film at room temperature, and has a magnetic characteristic that becomes a perpendicular magnetized film at a predetermined temperature or higher between room temperature and the Curie temperature. Prepare The reproducing layer 11 is located closer to the incidence of light than the intermediate layer 12 and the memory layer 13, and has a Curie temperature higher than that of at least the intermediate layer 12 and the memory layer 13 so that the Kerr rotation angle does not deteriorate during reproduction. To do. The material of the reproducing layer 11 is preferably a rare earth-iron group amorphous alloy, for example, one mainly containing GdFeCo. Tb, Dy, etc. may be added.
Also, in order to prevent deterioration of the Kerr rotation angle at short wavelength, N
Light metal rare earths such as d, Pr and Sm may be added. It is preferable that the magnetic anisotropy is small and the compensation temperature is between room temperature and the Curie temperature. The compensation temperature is in the vicinity of the Curie temperature of the intermediate layer 12 described later, that is, from −50 ° C. to + 100 ° C. based on the Curie temperature of the intermediate layer 12,
Desirably, it is set in the range of -20 ° C to + 80 ° C.

As described above, in the magneto-optical recording medium of the present invention, the thickness of the reproducing layer 11 is selected to be 20 nm or more and 100 nm or less. In the magneto-optical recording medium of the present invention, the memory layer 13 exhibits perpendicular magnetic anisotropy at room temperature, and the reproducing layer 11 and the intermediate layer 12 exhibit in-plane magnetic anisotropy at room temperature. An interface domain wall is formed between the layers 12. Memory layer
Since a material having a large perpendicular magnetic anisotropy is used for 13, most of the interface domain wall is formed on the side of the intermediate layer 12 and the reproducing layer 11. Therefore, even if materials having the same composition are used, the reproducing layer 11
9A, the domain wall penetrates the intermediate layer 12 at room temperature and extends to the light incident side surface of the reproducing layer 11 as shown in FIG. 9A. Therefore, the masking effect becomes insufficient and C / N
This leads to a decrease in the ratio.

On the contrary, if the reproducing layer 11 is too thick, FIG.
As shown in, since the exchange coupling force of the memory layer 13 does not work up to the light incident side surface of the reproduction layer 11, the temperature is not as high as the reproduction power and the reproduction signal is lowered. Therefore, the reproduction layer 11
It is necessary that the film thickness is 100 nm or less.

Further, the film thickness of the reproducing layer 11 affects the temperature distribution of the medium and the mask effect in the low temperature region, and the crosstalk with the adjacent track also changes depending on the film thickness. By selecting the film thickness of the reproducing layer 11 to be 25 nm or more and 50 nm or less, it becomes an effective medium for narrowing the track pitch.

The intermediate layer 12 is provided mainly for the purpose of partially mediating or partially cutting the exchange coupling force from the memory layer 13 to the reproducing layer 11, and at room temperature, the in-plane magnetized film is formed. In addition, it has a magnetization characteristic of forming a perpendicular magnetization film at a predetermined temperature or higher between room temperature and Curie temperature. The intermediate layer 12 is located between the reproducing layer 11 and the memory layer 13, and has a Curie temperature higher than room temperature,
It is set lower than the Curie temperatures of the reproducing layer 11 and the memory layer 13. The Curie temperature of the intermediate layer 12 is large enough to mediate the exchange coupling force from the memory layer 13 to the reproducing layer 11 in the low temperature portion and the intermediate temperature portion in the light spot, and low enough to cut the exchange coupling force in the maximum temperature portion. Specifically, it is preferably 100 ° C or higher and 220 ° C or lower, more preferably 120 ° C or higher and 1
80 ° C or lower is preferable. The material of the intermediate layer 12, for example, rare earth-iron group amorphous alloy, for example, GdFeCo, GdCo, GdTbFeC.
o, GdDyFeCo, TbFeCo, DyFeCo, TbDyFeCo, etc. are good. Further, in order to reduce the Curie temperature, a non-magnetic element such as Cr, Al, Si, Cu may be added.

In the magneto-optical recording medium of the present invention, the intermediate layer 12
Has a thickness of 3 nm or more and 30 nm or less. If the thickness of the intermediate layer 12 is thinner than 3 nm, the stability of the magnetic characteristics of the magnetic film is deteriorated, and the original magnetic characteristics cannot be obtained due to variations in manufacturing. Even if the intermediate layer reaches the Curie temperature when a pinhole occurs, the reproducing layer 11 and the memory layer are
There are many problems such as not breaking the exchange coupling of 13.

If the thickness of the intermediate layer 12 is small, as shown in FIG.
As shown in (a), at room temperature, the ratio of the domain walls formed in the intermediate layer 12 and the reproducing layer 11 that penetrate into the reproducing layer 11 becomes large, so that the masking effect in the reproducing layer 11 becomes incomplete. Therefore, the thickness of the intermediate layer 12 should be selected to be 3 nm or more.

Further, since the saturation magnetization Ms of the intermediate layer 12 is larger than that of the reproducing layer 11, when the intermediate layer 12 is thick, the reproducing layer 11 is formed in the middle temperature portion as shown in FIG. 10 (b). The exchange coupling force from the memory layer 13 cannot be transmitted, and the transfer of the magnetization to the reproduction layer 11 becomes incomplete at about the reproduction temperature, so that the reproduction signal decreases. Therefore, the thickness of the intermediate layer 12 is 30
It must be nm or less.

Further, the film thickness of the intermediate layer 12 affects the state of the mask in the low temperature region, that is, in the temperature region in which the reproducing layer 11 has in-plane anisotropy, and therefore affects the crosstalk with the adjacent tracks. give. By selecting the film thickness of the intermediate layer 12 to be preferably 5 nm or more and 20 nm or less, it becomes an effective medium for narrowing the track pitch.

The reproducing layer 11, the intermediate layer 12, and the memory layer 13 have A
Elements such as l, Ti, Pt, Nb and Cr may be added to improve the corrosion resistance. In addition to the reproducing layer 11, the intermediate layer 12, and the memory layer 13, in order to enhance the interference effect and the protection performance, SiN _x , AlO _x , Ta
O _x, it may be provided such as a dielectric, such as SiO _x. Further, a layer having good thermal conductivity such as Al, AlTa, AlTi, AlCr, or Cu may be provided for improving thermal conductivity. In addition, an initialization layer in which magnetization is aligned in one direction for performing light modulation overwrite, and an auxiliary layer for assisting recording and reproducing for adjusting exchange coupling force or magnetostatic coupling force may be provided. Further, a protective coat made of the dielectric layer or polymer resin may be provided as a protective film.

Data signals are recorded on the optical disk of the present invention by moving the medium and simultaneously modulating the laser power while applying a magnetic field in a fixed direction (optical modulation recording).
Alternatively, the external magnetic field is modulated while irradiating the laser light having a constant power such that the memory layer 13 has a Curie temperature around Tc3 (magnetic field modulation recording). In the former case, a recording magnetic domain smaller than the light spot diameter can be formed by adjusting the laser light intensity so that only a predetermined area within the light spot becomes Tc3, and as a result, a signal with a period less than the light diffraction limit is recorded. You can do it. In the latter case, a small recording magnetic domain can be formed by setting the modulation frequency of the magnetic field to a high frequency as compared with the relative velocity (linear velocity) between the light spot and the medium.

Further, as is clear from the mechanism described later, in order for the super-resolution of the present invention to function stably, the magnetization around the recording mark must be oriented in the opposite direction to the mark. In the most general optical modulation recording, first, the laser power is kept constant at a high power while a constant magnetic field is applied, the magnetization of the track to be recorded is initialized (erasing operation), and then the direction of the magnetic field is reversed. In this state, the laser power is intensity-modulated to form a desired recording mark. At that time, if there is a random magnetized portion around the recording mark, noise may occur during reproduction.In order to improve the quality of the reproduced signal, it is generally necessary to erase in a wider width than the recording mark. Has been done. Therefore, since the magnetization around the recorded magnetic domain always faces the opposite direction to the magnetic domain, the super-resolution of the present invention operates stably under the conventional optical modulation recording.

Another method of optical modulation recording is optical modulation overwrite. This is JP-A-62-1
It uses a medium having the structure as described in 75948 and does not require an erasing operation prior to recording.
This medium has, in addition to a memory layer for holding recorded information, a writing layer in which magnetization is oriented in one direction prior to recording. When recording is performed on this medium, the laser intensity is modulated between Ph and Pl (Ph> Pl) according to the recorded information while applying a constant magnetic field in the direction opposite to the writing layer. When the temperature of the medium is raised to a temperature Th corresponding to Ph, Th is set to be substantially equal to Tc of the writing layer, so that the magnetizations of the memory layer and the writing layer form magnetic domains in the direction of the external magnetic field, and the medium is If the temperature is raised only to the temperature Tl corresponding to Pl, the magnetization direction becomes the same as that of the writing layer. This process occurs independently of prerecorded magnetic domains. Here, considering the time when the medium is irradiated with the laser of Ph, the portion forming the recording magnetic domain is heated to Th, but since the temperature distribution at this time is two-dimensionally widened. Even if the laser is raised to Ph, there is always a portion around the magnetic domain where the temperature rises only to Tl. Therefore, there is a portion having the opposite magnetization around the recording magnetic domain. That is, the super-resolution of the present invention is a conventional optical modulation over
Stable operation even under light recording.

Still another recording method is the above-mentioned magnetic field modulation recording. This is to change the direction of the external magnetic field in an alternating manner while irradiating the laser with high power DC, but in order to record new information without leaving the history of the previously recorded magnetic domains, The width forming the magnetic domains must always be constant. Therefore, in this case, unless some measures are taken, there is a region where the magnetization direction is random around the recording magnetic domain, and the super-resolution of the present invention does not operate stably. Therefore, when performing magnetic field modulation recording, the recording area should be initialized with a power larger than the normal recording power before shipment of the medium or prior to the first recording, or the land or groove should be recorded. It is necessary to completely initialize the magnetization of both of them.

FIG. 2 shows the state of the spots and the magnetized state of each magnetic layer when the disk moves to the right while irradiating the optical disk of the present invention with a laser beam. At this time, the disk is moving at about 9 m / s, and since heat is accumulated by laser irradiation, the position where the film temperature is maximum is behind the center of the laser spot.

First, the temperature of the medium at the front edge side with respect to the traveling direction of the spot 2 has not risen so much from room temperature. The temperature dependence of the saturation magnetization Ms of the reproducing layer 11 and the intermediate layer 12 is as shown in, for example, FIGS. 7 and 8, and both layers have a large saturation magnetization Ms in the low temperature region of the spot and the perpendicular magnetic anisotropy is high. Ku is small. At this time, the perpendicular magnetic anisotropy of the reproducing layer 11
If the energy for directing the magnetization of the reproducing layer 11 in the vertical direction by the exchange coupling force from the memory layer 13 through Ku1, the saturation magnetization Ms1, and the intermediate layer 12 is Ew13, (Equation 1) 2πMs ² > Ku + Ew13 The magnetization of the reproducing layer 11 is oriented in the film plane. In particular, since the saturation magnetization of the intermediate layer 12 is larger than that of the reproducing layer 11 and the in-plane anisotropy is strong, the interface domain wall energy between the memory layer 13 which is a perpendicular magnetic film and the reproducing layer 11 which is an in-plane magnetic film is The intermediate layer 12 has an absorbing effect. Therefore, by inserting the intermediate layer 12, the direction of magnetization is in the film plane even when the film thickness of the reproducing layer 11 is reduced as compared with the case where the intermediate layer 12 is not provided, and the magnetization of the memory layer 13 is not transferred. Form the front mask 4.

Next, when the medium temperature rises due to the irradiation of the spot 2, the saturation magnetization Ms of the reproducing layer 11 and the intermediate layer 12 gradually decreases. In particular, in the case of the present invention, both the compensation temperature of the reproducing layer 11 and the Curie temperature of the intermediate layer 12 are close to about 200 ° C., so that the saturation magnetization sharply decreases with increasing temperature of the medium. Therefore, the medium has a predetermined temperature Tth.
And (2) 2πMs ² <Ku + Ew13, the reproducing layer 11 becomes a perpendicularly magnetized film and at the same time exchange-couples with the memory layer 13, so that the magnetic domains held in the memory layer 13 are transferred to the reproducing layer 11. Form aperture 3 When the temperature further rises and becomes higher than the Curie temperature Tc2 of the intermediate layer 12, the exchange coupling force between the reproducing layer 11 and the memory layer 13 disappears. At this temperature, the reproducing layer 11 has the rare earth element sublattice magnetization predominant, and the composition is adjusted in advance so that the memory layer 13 has the iron group element sublattice magnetization predominant (that is, antiparallel). Then, the magnetic domain transferred to the reproducing layer 11 at a temperature of Tc2 or less loses the exchange coupling force from the memory layer 13 which holds the magnetic domain, and at the same time, the magnetostatic coupling force from the memory layer 13 is in the opposite direction. Will join. Also reproduction layer
Since 11 is also close to the compensation temperature, the influence of the demagnetizing field of the reproducing layer 11 itself is small, so that the reproducing layer 11 transferred from the memory layer 13
Domain cannot contract the Bloch domain wall energy and contracts and inverts. That is, in the spot 2 where the temperature is raised to the Curie temperature Tc2 or higher of the intermediate layer 12, there is a region in which the magnetic domains cannot exist in the reproducing layer and are aligned in the same direction. This part is the rear mask 5. The process of forming this rear mask results from the change in the balance of energy related to the interaction between the magnetic layers.
In particular, the mask is formed without applying an external magnetic field for reproduction.

The behavior of the magnetic domains transferred to the reproducing layer 11 in the process of moving from the aperture portion to the rear mask will be described in more detail.

FIG. 3 is a plan view showing a process in which a recording magnetic domain (hereinafter simply referred to as a recording magnetic domain) of the reproducing layer 11 transferred from the memory layer 13 contracts in a high temperature region when the light spot moves. And FIG. For the sake of simplicity, FIG. 3 shows the contraction process of one recording magnetic domain. Further, in FIG. 3, it is assumed that the magnetic material is a rare earth iron group ferrimagnetic material, the white arrow 30 indicates the entire magnetization, the black arrow 31 indicates the iron group sublattice magnetization, and the reproducing layer 11 is the RE-rich magnetic material. As the layers and the memory layer 13, the TM-rich magnetic layer is described as an example. FIG. 2 shows the entire image at the time of reproduction with the temperature distribution added. Since the temperature distribution of the medium has a limited thermal conductivity, it shifts from the center of the light spot in the direction opposite to the movement of the light spot.

FIG. 3A shows a state in which the recording magnetic domain 1 is in the aperture area. In the recording magnetic domain 1, in addition to the effective magnetic field Hwi due to the exchange coupling force from the memory layer 13,
An effective magnetic field Hwb due to Bloch domain wall energy and a static magnetic field Hd from the inside of the medium are applied. Hwi works to stably hold the recording magnetic domain 1 of the reproducing layer, but Hw
A force acts on b and Hd in the direction of expanding or contracting the recording magnetic domain. Therefore, in order for the reproducing layer 11 to stably transfer the magnetization of the memory layer 13, the condition of (Equation 3) is required before the recording magnetic domain 1 reaches the high temperature region 5.

(Equation 3) | Hwb−Hd | <Hc1 + Hwi (T <Th-mask) The coercive force Hc1 of the reproducing layer 11 apparently becomes large due to the exchange coupling force from the memory layer 13, so that 3)
Holds, and it becomes possible to stably transfer the magnetization information of the memory layer 13 and accurately reproduce the recorded information.

Hwi is represented by (Equation 4), where σwi is the interfacial domain wall energy between the reproducing layer 11 and the memory layer 13, Ms1 is the saturation magnetization of the recording magnetic domain 1 of the reproducing layer 11, and h1 is the film thickness of the reproducing layer. However, when the light spot (Equation 4) Hwi = σwi / 2Ms1h1 moves and enters the high temperature region 5, Hwi reaches the vicinity of the Curie temperature of the intermediate layer 12 and σwi sharply decreases.
i decreases. Therefore, the reproducing layer 11 returns to the original state of small coercive force (Equation 5), and the Bloch domain wall 8 of the recording magnetic domain 1 easily moves.

(Equation 5) | Hwb-Hd |> Hc1 + Hwi (T> Th-mask) Hwb is the Bloch domain wall energy of the reproducing layer 11 σwb, and the radius of the recording magnetic domain 1 of the reproducing layer 11 is r (Equation 6) , And acts in the direction to shrink the recording magnetic domain 1 (Fig. 4).

(Equation 6) Hwb = σwb / 2Ms1r Therefore, if Hwb−Hd becomes positive (sign is +) and becomes (Equation 7), the recording magnetic domain 1 contracts.

(Equation 7) Hwb-Hd> Hc1 + Hwi (T> Th-mask) Thus, as shown in FIG. 3B, the recording magnetic domain 1 is in the high temperature region.
When it goes into 5, it contracts and reverses, and finally all the magnetizations are oriented in the erasing direction, as shown in Fig. 3 (c).

That is, as shown in FIG. 2, in the high temperature region 5 in the light spot 2, since the reproducing layer 11 is always a perpendicular magnetization film oriented in the erasing direction, it functions as an optical mask (rear mask 5). To do. Therefore, as shown in FIG. 2, the light spot 2 is apparently narrowed down to a narrow region excluding the high temperature region 5 and the low temperature in-plane magnetized film region (front mask), and the apertures in other regions. Area 3 is reached, and recording magnetic domains (recording marks) with a period below the detection limit can be detected.

A conventional super-resolution method is disclosed in Japanese Patent Laid-Open No. 4-2559.
As described in 47, the external magnetic field Hr is used to form the mask according to the relationship of (Equation 8).

(Equation 8) Hr> Hc1 + Hwi In the present invention, since the mask is formed by changing the magnitude of the effective magnetic field Hw−Hd inside the medium instead of the external magnetic field Hr, the external magnetic field is unnecessary.

Next, a method of making the effective magnetic field Hw-Hd positively dominant at high temperature, that is, contracting the recording magnetic domain 1 will be described more specifically. Hd of (Equation 7) is composed of a leakage magnetic field Hleak from the surrounding erase magnetization, a static magnetic field Hst from the magnetization of the memory layer 13, and the like, and is represented by (Equation 9).

(Equation 9) Hd = Hleak ± Hst Among these, Hleak works in the direction of expanding the recording magnetic domain 1 as shown in FIG.

The first method of shrinking the recording magnetic domain 1 more easily in the high temperature region is to reduce the Hleak to reduce the recording magnetic domain 1.
This is a method of reducing the magnetic field that prevents the reversal of. Hlea
k is the saturation magnetization of the reproducing layer 11 around the recording magnetic domain to be eliminated
If s1 ″ and the radius of the recording magnetic domain 1 are r, they are roughly expressed by (Equation 10).

(Formula 10) Hleak = 4πMs1 ″ h1 / (h1 + 3 / 2r) In (Formula 10), the recording domain radius r and the reproducing layer film thickness h1 are
Since it cannot be easily changed, it is necessary to reduce Ms1 ″. In such a case, a material having a compensation temperature between room temperature and the Curie temperature may be selected for the reproducing layer. At the compensation temperature, the magnetization becomes small. Therefore, Hleak can be reduced.

As an example, a case where GdFeCo is used for the reproducing layer 11 will be described. 6 (a) to 6 (c) show the temperature dependence of Ms of GdFeCo having different compensation temperatures. The maximum temperature on the medium at the time of reproduction differs depending on the reproduction power, but the maximum temperature generally shown in the figure. The temperature is about 160 ~
Since it reaches 220 ° C. and the middle temperature region is lower by 20 to 60 ° C., Ms1 ″ is large in the cases shown in FIGS. 6 (b) and 6 (c). Therefore, Hleak becomes large. When a composition having a compensation temperature between room temperature and the Curie temperature is used for the reproducing layer 11 as shown in Fig. 6 (a), Ms in the middle temperature region and the high temperature region can be reduced to reduce Hd. When used in the reproducing layer 11, the compensation temperature strongly depends on the composition of the rare earth element (Gd) as shown in FIG. 6, so that the magnetic layer containing mainly GdFeCo is mainly used as the reproducing layer 11.
When used in, it is desirable to set the Gd amount to 25 to 35 at%.

The second method is the static magnetic field H from the memory layer 13.
This is a method of increasing st to a negative value to promote the reversal of the recording magnetic domain 1. Hst in (Equation 7) is maintained as it is when the recording magnetic domain 1 contracts depending on whether the reproducing layer 11 and the memory layer 13 are of the parallel type or the anti-parallel type when the high temperature region is entered from the exchange coupling region. Decides how to work. This is for the following reason.

As shown in FIG. 5, the exchange coupling force follows the direction of the TM sublattice magnetization having a strong exchange force, and the magnetostatic coupling force follows the direction of the entire magnetization. FIG. 5A shows an anti-parallel type in which the reproducing layer 11 is RE-rich and the memory layer 13 is TM-rich. In this case, when the intermediate layer 12 reaches the Curie temperature and the exchange coupling is broken, the memory layer is The magnetic domain 1 tries to reverse the magnetization due to the magnetostatic coupling force with 13 (Hs
t is negative). On the contrary, as shown in FIG. 5 (b), in the case of the parallel type (in the figure, both layers are TM rich), the magnetostatic coupling force acts in the direction to maintain the exchange coupling state (Hst is Be positive). Therefore, in order to invert the recording magnetic domain 1, it is desirable to adopt an anti-parallel type configuration.

Specifically, for example, the reproducing layer 11 and the memory layer 13
Is assumed to be ferrimagnetic, and the types of dominant sublattice magnetization may be reversed. For example, the reproducing layer 11 and the memory layer 13 are composed of a rare earth (RE) iron group (TM) element alloy,
11 is a magnetic layer having a rare earth element sublattice magnetization predominant (RE-rich), and memory layer 13 is an iron group element sublattice magnetization predominant (TM) at room temperature.
Rich). The anti-parallel structure needs to be achieved at least at the temperature at which the recording magnetic domain 1 contracts (in the above-mentioned middle temperature to high temperature region 5).

The value of Hst can be roughly calculated by using the radius of the recording magnetic domain 1, the distance from the magnetic domain of the memory layer 13, and the magnetization Ms2 of the memory layer assuming a cylindrical magnetic domain (Nagoya University). Doctoral dissertation, March 1993. "Research on the magnetism and magneto-optical effect of rare earth-iron group amorphous alloy thin films and their composite films", see Kobayashi Tadashi, P40-41). Hst is
It is proportional to the saturation magnetization Ms2 of the memory layer (Equation 11).

(Equation 11) Hst∝Ms2 Therefore, it is desirable to increase Ms2 so that the stability of recorded information does not deteriorate and the erase magnetization does not reverse.

Further, the static magnetic field Hst from the above-mentioned memory layer 13
Also acts on the magnetization in the erasing direction. However, when the magnetization in the erasing direction is reversed by Hst, the domain wall is formed over a wide range of the high temperature region 5, so that the domain wall energy greatly increases. Therefore, the magnetization in the same erasing direction is maintained without reversing the magnetization. Therefore, in the high temperature region 5, a region that is magnetically oriented in the erasing direction is always generated, and this becomes the rear mask 5. The effective magnetic field Hwb ′ of the Bloch domain wall energy when the erase magnetization is reversed is represented by (Equation 12) where R is the reversal domain radius.

(Equation 12) Hwb ′ = σwb / 2Ms1R Therefore, the condition that the erase magnetization is not inverted by Hst is (Equation 13).

(Equation 13) Hwb '> Hst The recording magnetic domain 1 above is easily inverted to the erased state 2
One of the two methods-a method of reducing Hleak and a method of negatively increasing Hst-may use only one of the methods, but the super-resolution effect is best exhibited when the two methods are used in combination. As described above, when the magneto-optical recording medium of the present invention is used, the magnetization of the memory layer 13 can be optically aligned in a uniform direction in the high temperature region 5 of the light spot without applying an external magnetic field during reproduction. Can be masked to.

Due to the mechanism described above, in the magneto-optical recording medium of the present invention, the most efficient super-resolution, that is, only the vicinity of the center of the information reproducing spot contributes to information reproduction, and thus high reproduction signal quality is expected. Moreover, the front mask can be formed by further optimizing the film characteristics, and the super-resolution method that is strong against crosstalk from adjacent tracks is realized without adding new parts such as an external magnetic field to the conventional reproducing device. It is possible.

Hereinafter, the present invention will be described in more detail with reference to experimental examples, but the present invention is not limited to the following experimental examples as long as the gist thereof is not exceeded.

(Experimental example 1) Each target of Si, Gd, Tb, Fe and Co was attached to a DC magnetron sputtering apparatus, and a glass substrate having a diameter of 130 mm and a polycarbonate substrate with a pre-groove were placed at a distance from the target. Is 15
After fixing to a substrate holder installed at a position of 0 mm, the chamber was kept until a high vacuum of 1 × 10 ⁻⁵ Pa or less was obtained.
The inside was evacuated with a cryopump. After evacuating and introducing Ar gas into the chamber to 0.4 Pa, SiN interference layer 90 nm, GdFeCo reproduction layer 20 n
m, GdFe intermediate layer 10 nm, TbFeCo memory layer 30 nm, Si
N protective layers having a thickness of 70 nm were sequentially deposited to obtain a medium having the structure shown in FIG. The film thickness of the GdFeCo reproducing layer is formed by reactive sputtering such that N ₂ gas is introduced in addition to Ar gas at the time of forming each SiN dielectric layer, and the refractive index is 2.1 while adjusting the mixing ratio. Filmed

The composition of the GdFeCo reproducing layer was Gd ₂₈ (Fe ₆₀ Co ₄₀ ) ₇₂
And RE rich at room temperature with saturation magnetization Ms of 222 emu.
/ Cc, compensation temperature 215 ° C, Curie temperature 300 ° C
That is all.

The composition of the GdFe intermediate layer is Gd ₄₀ Fe ₆₀ , TM rich at room temperature, Ms is 420 emu / cc, and Curie temperature is 190 ° C.

The composition of the TbFeCo memory layer is Tb ₂₀ (Fe ₈₀ Co ₂₀ )
₈₀ , TM rich at room temperature and saturation magnetization 200 emu /
The cc and Curie temperatures are 270 ° C.

Recording and reproducing characteristics were measured using these magneto-optical recording media. The measurement is based on the N.V. A. Was 0.55, the laser wavelength was 780 nm, the recording power was 7 to 15 mW, and the reproducing power was 2.5 to 4.0 mW so that the C / N ratio was the highest. The linear velocity was 9 m / s. First, after erasing the entire surface of the medium, a carrier signal of 11.3 MHz (corresponding to a mark length of 0.40 μm) was recorded in the memory layer to examine the C / N ratio.

Next, crosstalk with adjacent tracks (hereinafter referred to as crosstalk) was measured. The measurement is based on the N.V. A. Was 0.55, the laser wavelength was 780 nm, the recording power was 7 to 15 mW, and the linear velocity was 9 m / s. First, after erasing the entire surface of both the land and groove of the medium, after recording a carrier signal of 5.8 MHz (corresponding to a mark length of 0.78 μm) in the memory layer and measuring the carrier (CL), The carrier (which is called CG) when tracking was applied to the adjacent group was measured and expressed as CL-CG between them. That is, since the experiment is performed assuming that data is recorded on both the land and the groove, the effective track pitch is 0.8 μm. Table 1 shows the measurement results of C / N under optimum conditions and crosstalk under the same reproducing power.

(Experimental Examples 2 to 8) Magneto-optical recording media were prepared using the same structures and materials as those in Experimental Examples 1 to 8 except that the thickness of the reproducing layer which was the first magnetic layer was changed. Table 1 shows the thickness of the reproducing layer in each of Experimental Examples 2 to 8. By the same method as in Experimental Example 1, the C / N under the optimum conditions and the crosstalk under the same reproducing power were measured. The measurement results are shown in Table 1.

Comparative Examples 1 to 3 As shown in Table 2, the second
Experimental Examples 1 to 1 except that the thickness of the reproducing layer, which is a magnetic layer, was changed
A magneto-optical recording medium was prepared using the same structure and material as in No. 8. A signal corresponding to a mark length of 0.4 μm is recorded, and C /
The N ratio was examined. The measurement results are as shown in Table 2.

FIG. 13 is a graph showing the measurement results of Experimental Examples 1 to 8 and Comparative Examples 1 to 3 as a C / N ratio with respect to the thickness of the reproducing layer. FIG. 14 shows a graph as crosstalk with respect to the film thickness of the reproducing layer. The C / N ratio is 43d when the thickness of the reproducing layer is 20 nm or more and 100 nm or less.
B or more was obtained. Furthermore, the thickness of the reproducing layer is 25 nm or more 5
Crosstalk is suppressed to -30 dB or less in the range of 0 nm or less. Therefore, by using the present invention, a C / N ratio sufficient for good reproduction of information can be obtained, and more preferably, by selecting the thickness of the reproduction layer to be 25 nm or more and 50 nm or less, the linear density of the medium can be increased. As a result, the track density can be improved.

(Experimental Examples 9 to 16) Using the same apparatus and method as in Experimental Example 1, a SiN interference layer was 90 nm, a GdFeCo reproducing layer was 40 nm, a GdFe intermediate layer, a TbFeCo memory layer was 30 nm, and Si was used.
An N protective layer having a thickness of 70 nm was sequentially formed to obtain a medium having the structure shown in FIG. The thickness of the intermediate layer in Experimental Examples 9 to 16 is as shown in Table 3. With respect to these magneto-optical recording media of the present invention, a C / N ratio was investigated by recording a carrier signal of 11.3 MHz (corresponding to a mark length of 0.40 μm) in the same manner as in Experimental Example 1. The measurement results are shown in Table 3. When the film thickness of the intermediate layer is within the range of the present invention, that is, 3 nm or more and 30 nm or less, the C / N ratio is 40 dB or more, and good information reproduction can be expected.

The crosstalk is suppressed to -30 dB or less in the range of the thickness of the intermediate layer from 5 nm to 20 nm, and optimizing the thickness of the intermediate layer is effective for narrowing the track pitch. It is shown that.

(Comparative Examples 4 and 5) The same apparatus and method as in Experimental Examples 9 to 16 were used, except that the thickness of the intermediate layer was changed.
Magneto-optical recording media were prepared using the same configurations and materials as in Experimental Examples 9 to 16. The thickness of the intermediate layer is shown in Table 4. Experimental Example 9-
Table 4 shows the results of measuring C / N and crosstalk using the same method as in 16.

FIG. 15 is a graph showing the measurement results of Experimental Examples 9 to 16 and Comparative Examples 4 and 5 as a C / N ratio with respect to the thickness of the intermediate layer as a crosstalk with respect to the thickness of the intermediate layer. Is shown in FIG. The thickness of the intermediate layer is 3n
A C / N ratio of 40 dB or more was obtained in the range of m to 30 nm. 43d in the range of 5 nm to 30 nm
B has been reached. Considering not only the linear density of the medium but also the track density, the crosstalk is -30.
It is desirable that the thickness is 5 nm or more and 20 nm or less, which is suppressed to dB.

[0077]

[Table 1]

[0078]

[Table 2]

[0079]

[Table 3]

[0080]

[Table 4]

[0081]

In the magneto-optical recording medium of the present invention, by selecting the thickness of the reproducing layer to be 20 nm or more and 100 nm or less and the thickness of the intermediate layer to be 3 nm or more and 30 nm or less, a good masking effect can be obtained at low temperatures. A simple device (conventional device) is obtained, in which the magnetization of the memory layer is satisfactorily transferred to the reproducing layer in the middle temperature part, and the masking effect works again in the higher temperature part, and the reproducing magnetic field and / or the initialization magnet are not required. It is possible to reproduce magnetic domains smaller than the beam spot system, and to achieve high density recording by greatly improving the linear recording density or both the linear density and the track density.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining the mechanism of the super-resolution medium in the present invention.

3 (a), (b) and (c) are diagrams showing a state of reproducing the magneto-optical recording medium of the present invention.

FIG. 4 is a static magnetic field H applied to a recording magnetic domain transferred to a reproducing layer.
Diagram showing effective magnetic field Hwb due to leak, Hst and Bloch domain wall energy

5A is a diagram showing a stable magnetization direction when an exchange coupling force and a magnetostatic coupling force predominantly act on an antiparallel type layer structure, and FIG. 5B is a parallel type layer structure. Figure showing stable magnetization direction when exchange coupling force and magnetostatic coupling force predominantly act on

6 (a), (b), (c) are graphs showing temperature changes of magnetization for GdFeCo having different compensation temperatures.

FIG. 7 is a diagram showing a saturation magnetization curve of a reproducing layer.

FIG. 8 is a diagram showing a saturation magnetization curve of an intermediate layer.

9A is a schematic diagram showing a masking effect depending on the reproducing layer film thickness, and FIG. 9B is a schematic diagram showing an aperture effect depending on the reproducing layer film thickness.

FIG. 10A is a schematic diagram showing a mask effect depending on the thickness of the intermediate layer. FIG. 10B is a schematic diagram showing an aperture effect depending on the thickness of the intermediate layer.

FIG. 11 is a diagram showing reproduction power dependence of carrier and noise.

FIG. 12 is a diagram showing mark length dependency of C / N.

FIG. 13 is a diagram showing the dependence of C / N on the thickness of the reproducing layer.

FIG. 14 is a diagram showing the dependence of crosstalk on the thickness of the reproducing layer.

FIG. 15 is a diagram showing the dependency of C / N on the thickness of the intermediate layer.

FIG. 16 is a diagram showing the dependence of crosstalk on the thickness of an intermediate layer.

17 (a), (b) and (c) are principle diagrams of a two-layer constitution super-resolution using a conventional in-plane magnetized film.

FIG. 18 is a diagram showing static characteristics of a conventional two-layer super-resolution first magnetic layer using an in-plane magnetized film.

19A, 19B, and 19C are principle diagrams of a three-layer structure super-resolution using a conventional perpendicular magnetization film.

[Explanation of symbols]

 1 recording mark 2 reproducing spot 3 aperture 4 front mask 5 rear mask 6 groove 7 land 11 reproducing layer 12 intermediate layer 13 memory layer 14 interference layer 15 protective layer 16 heat dissipation layer 20 substrate

Claims (8)

[Claims] 1. A magneto-optical recording medium, which has an in-plane magnetization film at room temperature and a perpendicular magnetization film between room temperature and Curie temperature, and has a film thickness of 20 nm to 100 nm.
A magnetic layer, a second magnetic layer formed of a perpendicular magnetization film having a coercive force higher than that of the first magnetic layer and a Curie temperature lower than that of the first magnetic layer, and the Curie temperature of the first magnetic layer and the second magnetic layer. Film thickness 3 with lower Curie temperature
a third magnetic layer having a thickness of 30 nm or more and 30 nm or less is laminated on a substrate in the order of the first magnetic layer, the third magnetic layer, and the second magnetic layer. When it becomes a perpendicularly magnetized film between the Curie temperatures of the magnetic layer, it exchange-couples with the second magnetic layer, the information stored in the second magnetic layer is transferred, and at the Curie temperature of the third magnetic layer, A magneto-optical recording medium, which is magnetized in one direction regardless of the information stored in the second magnetic layer. 2. The first magnetic layer according to claim 1, comprising a magnetic layer containing GdFeCo as a main component. 3. The magnetic layer according to claim 1, wherein the third magnetic layer is a magnetic layer containing GdFe and GdFeCo as main components. 4. The in-plane anisotropy at room temperature according to claim 1, wherein the third magnetic layer has a larger in-plane anisotropy than the first magnetic layer. 5. The saturation magnetization of the third magnetic layer at room temperature according to claim 1, which is larger than that of the first magnetic layer. 6. The first magnetic layer according to claim 1, wherein the first magnetic layer has a compensation temperature between room temperature and Curie temperature. 7. The first and second magnetic layers of claim 1, wherein the first and second magnetic layers are ferrimagnetic rare earth-iron group element amorphous alloys, and the first magnetic layer has a rare earth element sublattice magnetization predominance. The two magnetic layers have the iron group element sublattice magnetization predominant, or vice versa. 8. An in-plane magnetized film at room temperature, which becomes a perpendicular magnetized film between room temperature and Curie temperature, and has a film thickness of 20 nm or more and 100 or more.
nm, a second magnetic layer composed of a perpendicular magnetization film having a coercive force larger than that of the first magnetic layer and a Curie temperature lower than that of the first magnetic layer, the recording information being accumulated, the first magnetic layer and the second magnetic layer. A third magnetic layer having a Curie temperature lower than the Curie temperature of the magnetic layer and having a film thickness of 3 nm or more and 30 nm or less is laminated on a substrate at least the first magnetic layer, the third magnetic layer, and the second magnetic layer in this order. The first magnetic layer exchange-couples with the second magnetic layer when it becomes a perpendicularly magnetized film between room temperature and the Curie temperature of the third magnetic layer, and the information stored in the second magnetic layer is transferred. In the vicinity of the Curie temperature of the third magnetic layer, the magneto-optical recording medium magnetized in one direction regardless of the information stored in the second magnetic layer is irradiated with a light spot from the substrate side, Reconstruction of information stored in the second magnetic layer In the information reproducing method, the magnetization of the first magnetic layer in the high temperature portion is unidirectionally magnetized by raising the temperature of the third magnetic layer near the Curie temperature in the high temperature portion in the irradiated light spot. The first magnetic layer is a perpendicular magnetization film in the middle temperature portion of the light spot, and the first magnetic layer and the second magnetic layer are
Information stored in the second magnetic layer is transferred to the first magnetic layer by exchange coupling with the magnetic layer, and the first magnetic layer is an in-plane magnetized film in a low temperature portion in the light spot. The information reproducing method is characterized in that the information is reproduced by detecting the magneto-optical effect of the reflected light of the light spot.