JPH10334529A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium capable of satisfactorily performing both of an overwriting operation and a magnetically super-high resolution reproducing operation without lowering a recording sensitivity and a CN(carrier-to-noise intensity) ratio. SOLUTION: At least, a recording layer 15 on which information are recorded by inversions of magnetization directions of subgratings due to an external magnetic field, a memory layer 13 to which magnetization of the subgratings of the recording layer 15 are transcribed and in which information are held, a reproduction layer 11 to which magnetization direction of subgratings of one part of the memory layer 13 are transcribed, a non-magnetic layer 12 formed in between the reproduction layer 11 and the memory layer 13, an initializing layer 17 lingering up the magnetization directions of the subgratings of the recording layer 15 forcibly to one direction and a switching layer 16 blocking the transmitting of an exchange coupling force to the recording layer 15 by the initializing layer 17 at the inverting time of the magnetization directions of the subgratings of the recording layer 15 due to the external magnetic field are laminated on a substrate 21.

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 whose information can be appropriately rewritten by modulating the recording light to be irradiated.

[0002]

2. Description of the Related Art Conventionally, in a magneto-optical disk (magneto-optical recording medium), in order to rewrite already recorded information with new information, the recorded information is temporarily erased (erasing operation). It was necessary to write new information. However, in recent years, a magneto-optical disk of an optical modulation overwrite type which does not require the above erasing operation has been proposed.

In this magneto-optical disk of the light modulation overwrite method, the intensity of the light (recording light) irradiated at the time of recording is simply modulated in accordance with the information to be recorded, so that the already recorded information can be erased and a new one can be obtained. Information can be written almost simultaneously. Therefore, according to the optical modulation overwriting method, the operation time for rewriting with new information can be shortened by the time required for the erasing operation, and the speed can be increased.

On the other hand, magneto-optical disks are required to have a higher information rewriting speed as described above.
It is required to increase the capacity. In order to respond to the demand for increasing the capacity of the magneto-optical disk, both a technique for recording information at high density and a technique for accurately reproducing information recorded at high density are required. When recording information, it is general to irradiate a recording portion with recording light to raise its temperature and change its magnetization direction. Therefore, information can be recorded using only the central portion of the spot area of the recording light applied to the magneto-optical disk, where the temperature rises in particular, and the density can be increased.

On the other hand, recorded information is reproduced by an optical method such as irradiating linearly polarized light (reproducing light) to a portion to be reproduced and detecting the rotation angle of the plane of polarization of the reflected light. Therefore, when a plurality of pieces of information exist in the spot area of the reproduction light, crosstalk occurs and accurate reproduction cannot be performed. In particular, when information is recorded at a high density as described above, crosstalk during reproduction becomes a problem.

As a countermeasure, attempts have been made to reduce the spot area of the reproducing light itself by improving the recording / reproducing apparatus, such as shortening the wavelength of the reproducing light. However, it is difficult to greatly reduce the spot area. Met. Therefore,
When irradiating the reproduction light, a mask area is formed in the spot area, and by preventing the rotation of the polarization plane of the reflected light in the mask area from being reflected in the reproduction signal,
Magnetic super-resolution (Magnet) that substantially reduces the spot area
(Superiorly induced Super Resolution) technology has been proposed.

In this magnetic super-resolution technique, a mask region is formed by utilizing the fact that a temperature distribution is generated in a spot region by the energy of reproduction light applied to a magneto-optical disk during reproduction. This magnetic super-resolution technique includes, for example, a method in which a low-temperature portion of a spot area is used as a mask area (for example, a CAD method (Center Aperture Ditection),
(Magnetostatic coupling type MSR method), a method in which a high temperature portion of a spot region becomes a mask region, and a method in which a portion other than an intermediate temperature portion of a spot region becomes a mask region.

As described above, in recent magneto-optical disks, on the one hand, the speed of rewriting information has been increased by the introduction of the optical modulation overwrite method, and on the other hand, by the introduction of the magnetic super-resolution technology, the high density has been achieved. Recording and reproduction of important information. Attempts have been made to apply the magneto-optical overwrite method and the magnetic super-resolution technology to one magneto-optical disk in order to simultaneously incorporate the advantages of the two technologies. For example, a technology that combines the above-described CAD method and the light modulation overwrite method, or a technology that combines the above-described magnetostatic coupling type MSR method and the light modulation overwrite method (for example, the 20th Annual Meeting of the Japan Society of Applied Magnetics) 1996, p. 312).

[0009]

However, the above-mentioned CAD
A magneto-optical disk that simply combines the method and the light modulation overwrite method still has the following problems.
In the CAD method, the reproducing layer must be a film that is in-plane magnetized at room temperature. In the case where the CAD method is applied to the light modulation overwriting method, the above-mentioned reproducing layer is formed by the exchange coupling force with the memory layer of the recording layer and the memory layer for enabling the light modulation overwriting. They will work together.

[0010] Therefore, in order to magnetize the reproducing layer of the CAD system at least on the irradiation surface side of the reproduction light at room temperature at room temperature, the thickness of the reproduction layer is increased and the irradiation surface is exposed from the memory layer. It is necessary to prevent the influence of the exchange coupling force from occurring. However, when the film thickness is increased, there is a problem that the recording sensitivity is reduced. In particular, in the light modulation overwrite method in which the number of layers is increased, the thickness of the film originally poses a problem, and it is not preferable to increase the thickness of the reproducing layer.

Further, when the thickness of the reproducing layer is increased, the exchange coupling force from the reproducing layer which is in-plane magnetized at room temperature acts on the memory layer. This function prevents the operation of transferring the information of the recording layer to the memory layer at the time of overwriting recording of information, and thus causes a problem that a sufficient CN ratio cannot be obtained. Compared to the combination of the CAD method and the light modulation overwrite method, the 20th Annual Meeting of the Japan Society of Applied Magnetics, 1996, P.3
Magneto-optical disk (hereafter, referred to as the magneto-optical disk) combining the magnetostatic coupling type MSR method and the light modulation overwrite method reported in
"Magnetostatically coupled MSR / DOW magneto-optical disk")
Discloses that the thickness of the reproducing layer can be reduced by forming a dielectric layer between the reproducing layer and the memory layer.

However, this magnetostatically coupled MSR / DOW magneto-optical disk still has the following problems when considered for practical use. First, the magnetostatic coupling MSR / DO
In the W magneto-optical disk, in order to initialize the recording layer at the time of overwrite recording, it is necessary to incorporate an initialization magnet in the recording / reproducing apparatus side for forcibly aligning the magnetization direction of the recording layer in one direction. The initialization magnet must have a magnetic field larger than the reversal magnetic field of the recording layer, and has a large outer shape.

However, recent recording / reproducing apparatuses must be miniaturized, and it is not practical to incorporate such a large initialization magnet. Even if an initialization magnet having a size that can be built into a small recording / reproducing apparatus is installed, the reversal magnetic field of the recording layer that can be initialized by the initialization magnet needs to be 2 k (Oe) or less. However, the switching magnetic field of the recording layer is 2 k
(Oe) If a magneto-optical disk having a thickness of not more than (Oe) is to be manufactured, its film thickness needs to be about 80 nm in consideration of manufacturing variations of the magneto-optical disk. That is, to put the magnetostatically coupled MSR / DOW magneto-optical disk to practical use,
It is necessary to increase the thickness of the recording layer (80 nm or more).

However, when the film thickness is increased as described above, there is a problem that the recording sensitivity is lowered. A decrease in recording sensitivity leads to a reduction in the number of revolutions of the recording / reproducing apparatus, and the effect of speeding up due to overwriting is diminished. Further, if a magnetostatically coupled MSR / DOW magneto-optical disk is put to practical use, the magnetic field leaking from the recording layer increases as the recording layer becomes thicker.
At the time of information reproduction, the transfer operation of the information held in the memory layer to the reproduction layer is disturbed, and there is also an essential problem that the effect of the magnetic super-resolution reproduction is reduced.

An object of the present invention is to provide both an overwriting operation and a magnetic super-resolution reproducing operation without reducing the recording sensitivity and the CN ratio even when the magneto-optical overwriting method and the magnetic super-resolution technology are combined. It is an object of the present invention to provide a magneto-optical recording medium that can perform well.

[0016]

According to a first aspect of the present invention, there is provided a recording layer on which information is recorded at least on a substrate of a magneto-optical recording medium by inversion of a sublattice magnetization direction by an external magnetic field; A memory layer formed between the memory layer and the substrate, wherein the sub-lattice magnetization direction of the recording layer is transferred and information is retained; A reproducing layer to which the lattice magnetization direction is transferred,
A nonmagnetic layer formed between the reproducing layer and the memory layer, an initialization layer formed on the opposite side of the recording layer from the substrate and forcibly aligning the sublattice magnetization direction of the recording layer in one direction, and a recording layer. A switching layer formed between the initialization layer and the switching layer for preventing transmission of the exchange coupling force to the recording layer by the initialization layer when the sub-lattice magnetization direction of the recording layer is reversed by an external magnetic field. .

According to a second aspect of the present invention, in the magneto-optical recording medium according to the first aspect, the information held in the memory layer is opposite to each other depending on whether the irradiating recording light is strong or weak. This is represented by the following sublattice magnetization direction.
According to a third aspect of the present invention, in the magneto-optical recording medium according to the first aspect, the reproducing layer is provided with a memory layer having a partial area corresponding to a temperature distribution generated in the reproducing layer by the irradiated reproducing light. The sub-lattice magnetization direction is transferred.

According to a fourth aspect of the present invention, in the magneto-optical recording medium according to the third aspect, a partial area of the reproducing layer is an area whose temperature has become equal to or higher than a predetermined temperature by irradiation of the reproducing light. According to a fifth aspect of the present invention, in the magneto-optical recording medium according to the first aspect, the reproducing layer, the memory layer, the recording layer, the switching layer, and the initialization layer are made of a magnetic material mainly composed of a rare earth metal and a transition metal. It is.

According to a sixth aspect of the present invention, in the magneto-optical recording medium according to the fifth aspect, the Curie temperature of the recording layer is:
It is higher than the Curie temperature of the memory layer and the switching layer and lower than the Curie temperature of the initialization layer. According to a seventh aspect of the present invention, in the magneto-optical recording medium according to the fifth aspect, the reproducing layer is a magnetic material having a compensation temperature higher than room temperature.

According to an eighth aspect of the present invention, in the magneto-optical recording medium according to the fifth aspect, the memory layer is a magnetic material whose compensation temperature is lower than room temperature. According to a ninth aspect of the present invention, in the magneto-optical recording medium according to the fifth aspect, the thickness of the memory layer is larger than 25 nm and smaller than 45 nm. According to a tenth aspect, in the magneto-optical recording medium according to the fifth aspect, the thickness of the recording layer is 15n.
It is thicker than m and thinner than 40 nm.

According to an eleventh aspect of the present invention, in the magneto-optical recording medium of the tenth aspect, the absolute value of the difference between the thickness of the recording layer and the thickness of the initialization layer is smaller than 30 nm. The thickness of the oxide layer is greater than 15 nm.

(Function) In the magneto-optical recording medium according to the first aspect of the present invention, after the information has already been recorded, the information is retained in the memory layer, and the recording layer has an initial sublattice magnetization direction. It is in a state (initial state) aligned in one direction by the oxide layer.

When information is rewritten, new information is temporarily recorded on the recording layer. The information temporarily recorded in the recording layer is expressed in an initial state of the recording layer or in a state in which the sublattice magnetization direction in the initial state is reversed by an external magnetic field. In this magneto-optical recording medium, when the switching layer prevents the initialization layer from transmitting the exchange coupling force to the recording layer, the sub-lattice magnetization direction of the recording layer is reversed by the external magnetic field. The new information temporarily recorded on the recording layer in this manner is transferred to the memory layer. afterwards,
The recording layer is initialized by the initialization layer, and returns to the initial state. In this magneto-optical recording medium, when transmission of exchange coupling force to the recording layer by the initialization layer is restored by the switching layer, the direction of the sublattice magnetization of the recording layer is forcibly aligned in one direction and the initial state. Be transformed into The memory layer to which information has been transferred from the recording layer retains the information as it is. Thus, the new information is finally stored in the memory layer. Overwrite recording is performed by repeating such a recording process.

On the other hand, at the time of reproducing information, the information held in the memory layer is transferred to the reproducing layer through the non-magnetic layer with the sublattice magnetization direction of a part of the region. Therefore, in this magneto-optical recording medium, information can be reproduced by magnetic super-resolution. In the magneto-optical recording medium according to the second aspect of the present invention, the sub-lattice magnetization direction of the recording layer is reversed by an external magnetic field when the irradiated recording light is strong, and the recording layer is reversed when the recording light is weak. Are kept in the initial state. Therefore,
The memory layer holds information represented by sub-lattice magnetization directions that are opposite to each other depending on whether the recording light is strong or weak.

In the magneto-optical recording medium according to the third aspect of the present invention, a temperature distribution is generated in the reproducing layer by the irradiated reproducing light, and the sub lattice of the memory layer is formed only in a part of the area corresponding to the temperature distribution. The magnetization direction is transferred. Therefore,
Information recorded at a high density on the memory layer can be accurately reproduced. In the magneto-optical recording medium according to the fourth aspect of the present invention, the sub-lattice magnetization direction of the memory layer is transferred only to a part of the region where the temperature has reached a predetermined temperature or higher by the irradiation of the reproduction light. As described above, since the sublattice magnetization direction of the memory layer is transferred only to the reproduction area smaller than the spot area of the reproduction light, information recorded at high density on the memory layer can be accurately reproduced.

In the magneto-optical recording medium according to the fifth aspect of the present invention, the reproducing layer, the memory layer, the recording layer, the switching layer, and the initialization layer are made of a material mainly composed of a rare earth metal and a transition metal. The Curie temperature of each layer can be set within a practical temperature range. Further, the thermal stability of each layer is good and the thermal conductivity is high, so that information can be efficiently recorded. Furthermore, excellent mass productivity,
Manufacturing costs can also be kept low.

In the magneto-optical recording medium according to the present invention, the recording medium is irradiated with such a strong recording light that the temperature thereof is heated between the Curie temperature of the recording layer and the Curie temperature of the initialization layer. Sometimes, the sublattice magnetization direction of the recording layer is reversed by an external magnetic field. When the recording layer is irradiated with a weak recording light which is heated only between the Curie temperature of the recording layer and the Curie temperatures of the memory layer and the switching layer, the recording layer is kept in the initial state. Therefore, the memory layer holds information represented by the sublattice magnetization directions that are opposite to each other when the recording light to be irradiated is strong and weak.

In the magneto-optical recording medium according to the present invention, the reproducing layer is a film which is in-plane magnetized over the entire surface at room temperature. Then, in the temperature distribution generated by the irradiation of the reproduction light, the magnetization is perpendicularly magnetized only in a region where the temperature rises to near the compensation temperature. Therefore, in this reproducing layer, the sub-lattice magnetization direction of the memory layer is transferred only to a part of the region perpendicularly magnetized by heating with the reproducing light.

In the magneto-optical recording medium according to the present invention, since the compensation temperature of the memory layer is lower than room temperature, the sub-lattice magnetization direction of the memory layer is satisfactorily transferred to the reproduction layer during reproduction. In the magneto-optical recording medium according to the ninth aspect, since the thickness of the memory layer is greater than 25 nm and less than 45 nm, the sub-lattice magnetization direction of the memory layer is satisfactorily transferred to the reproducing layer during reproduction. . In addition, during recording, the sublattice magnetization direction of the recording layer is satisfactorily transferred to the memory layer.

In the magneto-optical recording medium according to the tenth aspect of the present invention, the thickness of the recording layer is greater than 15 nm and is greater than 40 nm.
Since it is thinner than nm, during recording, the sublattice magnetization direction of the recording layer is favorably reversed by an external magnetic field. Further, when the recording layer is initialized, the sublattice magnetization direction of the initialization layer is satisfactorily transferred to the recording layer. In the magneto-optical recording medium according to the eleventh aspect, the absolute value of the difference between the thickness of the recording layer and the thickness of the initialization layer is smaller than 30 nm, and the thickness of the initialization layer is smaller than 15 nm. Since it is thick, the sublattice magnetization direction of the initialization layer is always kept in one direction without being reversed by exchange coupling force from another magnetic layer. In addition, since the leakage magnetic field from the initialization layer is reduced, the sub-lattice magnetization direction of the memory layer is transferred to the reproducing layer during reproduction.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a configuration of the magneto-optical disk 10 of the present embodiment. This embodiment corresponds to claims 1 to 11.

As shown in FIG. 1, the magneto-optical disk 10 has a substrate 21, an undercoat 22, a reproducing layer 11, a non-magnetic layer 12, Memory layer 13, intermediate layer 14, recording layer 1
5, a switching layer 16, an initialization layer 17, an overcoat 23, a metal layer 24, and a resin protection layer 25 are laminated.

In the magneto-optical disk 10, the reproducing layer 11, the non-magnetic layer 12, the memory layer 13, the intermediate layer 14, the recording layer 15, the switching layer 16, the initialization layer With the layer 17, overwrite recording of information and magnetic super-resolution reproduction are performed. The reproducing layer 11, the nonmagnetic layer 12, the memory layer 13, the intermediate layer 14, the recording layer 15, the switching layer 16, and the initialization layer 17 are collectively referred to as a rare earth-transition metal (RE-TM) alloy layer 10a. .

Next, the composition and function of each of the layers 11 to 17 constituting the RE-TM alloy layer 10a will be described. Each layer 11 to 17 constituting this RE-TM alloy layer 10a
Are exchange-coupled or magnetostatically coupled to each other. Of these, the recording layer 15 is composed of dysprosium (Dy) which is a rare earth metal and iron (Fe) and cobalt (C) which are transition metals.
o) is a perpendicular magnetization film. When the composition of the recording layer 15 is represented by atomic percentage, Dy is 26% and Fe is 48%.
% And Co is 26% (hereinafter, the atomic percentage of the composition is
Dy26Fe48Co26). The thickness of the recording layer 15 is 20 nm. The recording layer 15 is a layer on which information is recorded by reversing the magnetization direction of the sublattice by an external recording magnetic field during overwrite recording.

The memory layer 13 is a perpendicular magnetization film made of terbium (Tb) as a rare earth metal and Fe and Co as transition metals. The composition of the memory layer 13 is T
b18Fe74Co8, whose compensation temperature is lower than room temperature (corresponding to the temperature of the magneto-optical disk 10 when no recording light or reproduction light is irradiated). The thickness of the memory layer 13 is 35 nm. Note that this memory layer 13
Compared to the recording layer 15, the Curie temperature is lower and the coercive force at room temperature is higher. Also, this memory layer 13
Is a layer in which the sub-lattice magnetization direction of the recording layer 15 is transferred and information is retained during overwrite recording.

The intermediate layer 14 is a magnetized film composed of gadolinium (Gd), which is a rare earth metal, and Fe, Co, which are transition metals. The composition of the intermediate layer 14 is Gd32Fe64C
o4. The thickness of the intermediate layer 14 is 10 nm. The intermediate layer 14 is a layer for adjusting the exchange coupling force between the recording layer 15 and the memory layer 13 during magnetic super-resolution reproduction.

The reproducing layer 11 is composed of Gd which is a rare earth metal,
It consists of transition metals Fe and Co. This reproduction layer 11
Is Gd29Fe46Co25, and its compensation temperature is higher than room temperature. The thickness of the reproducing layer 11 is 25 nm.
It is. The reproducing layer 11 is in-plane magnetized over the entire surface at room temperature, and is perpendicularly magnetized only in a region of the temperature distribution generated by the irradiation of the reproducing light at which the temperature has risen to near the compensation temperature during magnetic super-resolution reproduction. Layer. Therefore, in the reproducing layer 11, the sub-lattice magnetization direction of the memory layer 13 is transferred to only a part of the region (corresponding to a reproducing region described later) which is vertically magnetized by heating with the reproducing light.

The nonmagnetic layer 12 is a thin film of silicon nitride, and its thickness is 20 nm. The non-magnetic layer 1
Reference numeral 2 denotes a layer that substantially blocks the exchange coupling force between the reproduction layer 11 and the memory layer 13 during overwrite recording or super-resolution reproduction operation. The initialization layer 17 is a perpendicular magnetization film made of Tb, which is a rare earth metal, and Fe, Co, which are transition metals. The composition of the initialization layer 17 is Tb18Fe16C
o66. The thickness of the initialization layer 17 is 20 nm as in the case of the recording layer 15 described above. The initialization layer 17 has a higher Curie temperature and a higher coercive force than the recording layer 15 described above. This initialization layer 17
Even when the recording light is irradiated during overwrite recording and the temperature rises the most, the sublattice magnetization direction is always kept in one direction. Therefore, by this initialization layer 17,
The sub-lattice magnetization direction of the recording layer 15 is forcibly aligned in one direction each time overwrite recording is performed (initial state).

The switching layer 16 is a perpendicular magnetization film composed of Tb, which is a rare earth metal, and Fe, Co, which are transition metals. The composition of the switching layer 16 is Tb17F
e77Co6. The switching layer 16 has a thickness of 12 nm. The switching layer 16
Has a lower Curie temperature and a lower coercive force than the recording layer 15 and the initialization layer 17 described above. Therefore, during the overwrite recording, when the sublattice magnetization direction of the recording layer 15 is reversed by the recording magnetic field during the overwrite recording, the switching layer 16
Blocking the transfer of exchange coupling force to

The RE-TM alloy layer 10a composed of the layers 11 to 17 described above is protected by the undercoat 22 and the overcoat 23. The undercoat 22 and the overcoat 23 are made of silicon nitride. The thickness of the undercoat 22 is 70 nm, and the thickness of the overcoat 23 is 30 nm. The metal layer 24 formed on the opposite side of the overcoat 23 from the substrate is made of aluminum and has a thickness of 30 nm. This metal layer 24 is a layer for adjusting the recording sensitivity of the entire magneto-optical disk 10 shown in FIG. The resin protective layer 25 further formed on the opposite side of the metal layer 24 from the substrate is
The undercoat 22, R
E-TM alloy layer 10a, overcoat 23, metal layer 2
4 is a film that protects the entirety.

The substrate 21 itself is made of a polycarbonate substrate having a diameter of 90 mm, and a guide groove having a pitch of 1.1 μm is spirally formed on one surface thereof.
Next, the undercoat 22, R
Method of forming E-TM alloy layer 10a (reproducing layer 11, nonmagnetic layer 12, memory layer 13, intermediate layer 14, recording layer 15, switching layer 16, initialization layer 17), overcoat 23, and metal layer 24 The outline will be described. Each of these layers is formed using a well-known sputtering method.

The nonmagnetic layer 12, the undercoat 22, and the overcoat 23 are made of silicon nitride as described above, and are formed in a chamber in which a silicon target is disposed. Specifically, the silicon nitride layer temporarily increases the gas pressure in the chamber to 5 × exp (−5) Pa
The chamber is evacuated until the temperature becomes as follows. Thereafter, an argon gas and a nitrogen gas are introduced into the chamber, and a film is formed by reactive sputtering.

The reproducing layer 11, the intermediate layer 14, the switching layer 16, and the metal layer 24 are formed by introducing an argon gas into a chamber in which a target made of a material having the same composition as each layer is placed. You. Incidentally, the target for forming the reproducing layer 11 is a Gd29Fe46Co25 alloy. The target for forming the intermediate layer 14 is Gd32
Fe64Co4 alloy. The target for forming the switching layer 16 is a Tb17Fe77Co6 alloy.
The target for forming the metal layer 24 is aluminum.

The formation of the memory layer 13, the recording layer 15, and the initialization layer 17 is performed in a chamber in which a rare earth metal target and a transition metal target are separately arranged.
It is performed by binary simultaneous sputtering. in this case,
A desired composition can be obtained by adjusting the ratio of the power supplied to each of the rare earth metal target and the transition metal target. Incidentally, for forming the memory layer 13, a Tb target and an Fe90Co10 alloy target are used. For forming the recording layer 15, a Dy target and an Fe65Co35 alloy target are used. For forming the initialization layer 17, a Tb target and an Fe80Co20 alloy target are used.

The thickness of each layer described above can be set to a desired value by adjusting the sputtering time. By the way, a recording / reproducing apparatus for recording / reproducing information on / from the magneto-optical disk 10 having the above configuration includes a semiconductor laser having a wavelength of 680 nm and a numerical aperture NA of 0.55.
Objective lens, a recording magnet for generating a magnetic field of 250 (Oe), and a motor for rotating the magneto-optical disk (linear velocity 9 m
/ Sec).

Among these, the setting of the output power of the semiconductor laser differs between the case where it is used for recording information and the case where it is used for reproduction. When used for recording information, the power of light (recording light) from a semiconductor laser is modulated according to the information to be recorded (duty ratio 35%). In addition,
The high-level power of the recording light has a mark length of 0.45μ.
m, the distance between marks is set to 0.45 μm.

On the other hand, when used for information reproduction, the power of the light (reproduction light) from the semiconductor laser is set to a lower level (reproduction level) than the low level power of the recording light. Light (recording light or reproduction light) from such a semiconductor laser is condensed by an optical system such as an objective lens, and is applied to the magneto-optical disk 10 inserted into the recording / reproduction device from the substrate 21 side. (FIG. 1). Note that the reproduction light becomes linearly polarized when the magneto-optical disk 10 is irradiated by the optical system.

The recording magnet is continuously turned on during information recording, and is turned off during reproduction. The magnetic field generated by the recording magnet that is turned on is continuously applied to the position of the magneto-optical disk 10 where the recording light is irradiated. The direction of the magnetic field of the recording magnet depends on the initialization layer 1 of the magneto-optical disk 10.
7 is opposite to the sublattice magnetization direction.

Next, the magneto-optical disk 10 of the present embodiment
Next, a process in which information is overwritten and recorded will be described. Here, the direction of the magnetic field of the recording magnet is “downward”,
The description will be made assuming that the sublattice magnetization direction of the initialization layer 17 is “upward”.

At the time of information overwrite recording, the magneto-optical disk 10 is irradiated with recording light whose intensity is modulated according to the information to be recorded from the substrate 21 side, and a downward magnetic field of the recording magnet is continuously applied. . The initialization layer 17
Is always upward regardless of the magnetic field of the recording magnet. First, a recording process (high temperature process) when the power of the recording light to be irradiated is set to a high level will be described.

When the recording light having a high level of power is applied to the magneto-optical disk 10, the RE-TM alloy layer 10a in the central portion (heating region) of the spot region of the recording light becomes
The recording layer 15 is heated to a temperature higher than the Curie temperature (high-level temperature). At this time, at least the memory layer 13, the recording layer 15, and the switching layer 16 of the RE-TM alloy layer 10a heated to the high level temperature lose magnetization. That is, in the above-described heating region, the information (sublattice magnetization direction) held in the memory layer 13 has been erased.

Thereafter, when the spot area of the recording light and the magneto-optical disk 10 relatively move due to the rotation of the magneto-optical disk 10, the heating area by the high-level power of the recording light moves over the surface of the magneto-optical disk 10. Moving. Therefore, RE-T which has been heated to the high level temperature described above
After the M alloy layer 10a deviates from the spot area of the recording light, the temperature gradually decreases toward room temperature.

When the temperature of the magneto-optical disk 10 starts to decrease from the high level temperature, first, the magnetization of the recording layer 15 having the highest Curie temperature among the memory layer 13, the recording layer 15, and the switching layer 16 whose magnetization has been lost. Recovers. At this time, since the magnetization of the switching layer 16 is still lost, the exchange coupling force by the initialization layer 17 is not transmitted to the recording layer 15. Therefore, the recording layer 1 whose magnetization has been recovered
The sub-lattice magnetization direction of No. 5 becomes downward following the downward magnetic field of the recording magnet without being affected by the upward sub-lattice magnetization direction of the initialization layer 17.

When the temperature of the magneto-optical disk 10 further decreases, the coercive force of the recording layer 15 increases, while the magnetization of the memory layer 13 recovers. At this time, the memory layer 13
Is transferred to the recording layer 15 in the downward sublattice magnetization direction. Then, the sublattice magnetization direction of the memory layer 13 is downward. Thereafter, when the temperature of the magneto-optical disk 10 further decreases, the coercive force of the recording layer 15 further increases, and the coercive force of the memory layer 13 also increases.
Is restored. At this time, the switching layer 16
Is transferred to the upward sublattice magnetization direction of the initialization layer 17 having a strong coercive force. Then, the sublattice magnetization direction of the switching layer 16 is directed upward.

As described above, since the sublattice magnetization direction of the switching layer 16 is directed upward, the exchange coupling force of the initialization layer 17 having a strong coercive force is applied to the recording layer 15 via the switching layer 16. Will be transmitted. At this time, the recording layer 15 has its sublattice magnetization direction directed downward, but only holds the downward sublattice magnetization direction against the exchange coupling force of the initialization layer 17 having a strong coercive force. Has no coercive force yet. Therefore, the recording layer 15 includes the initialization layer 1 having a strong coercive force.
7 is transferred via the switching layer 16. Then, the sublattice magnetization direction of the recording layer 15 is forcibly inverted from downward to upward by the initialization layer 17 (initial state).

Further, since the sublattice magnetization direction of the recording layer 15 is inverted and initialized as described above,
The exchange coupling force by the recording layer 15 is also transmitted to the memory layer 13. At this time, the memory layer 13 has its sublattice magnetization direction downward, but has a coercive force enough to maintain the downward sublattice magnetization direction against the exchange coupling force of the recording layer 15. Therefore, the memory layer 13 can maintain the downward sub-lattice magnetization direction without being affected by the upward sub-lattice magnetization direction of the recording layer 15.

As described above, when the magneto-optical disk 10 is irradiated with the recording light having a high level of power, the magnetization direction of the sub-lattice of the recording layer 15 is temporarily lowered by the magnetic field of the recording magnet. After the downward sublattice magnetization direction is transferred to the memory layer 13, the sublattice magnetization direction of the recording layer 15 returns to the upward direction again (initial state). Then, through the high temperature process, the sublattice magnetization direction of the memory layer 13 in the heating region is kept downward, like the downward magnetic field of the recording magnet.

Next, a recording process (low-temperature process) when the power of the recording light to be irradiated is set to a low level will be described. When the recording light having a low level of power is applied to the magneto-optical disk 10, the RE-TM alloy layer 10a in the central portion (heating region) of the spot region of the recording light becomes the recording layer 1
5 and the memory layer 13,
The switching layer 16 is heated to a higher temperature (lower temperature) than the Curie temperature.

At this time, the magnetization of the memory layer 13 in the RE-TM alloy layer 10a in the heating region disappears,
The information (sublattice magnetization direction) held in the memory layer 13 is erased. Further, the magnetization of the switching layer 16 also disappears. On the other hand, the recording layer 15 retains the initial state (upward sublattice magnetization direction) by the initialization layer 17 although the coercive force decreases.

Thereafter, when the spot area of the recording light and the magneto-optical disk 10 relatively move due to the rotation of the magneto-optical disk 10, the heating area by the low-level recording light moves on the disk surface. Therefore, the RE-TM alloy layer 10 heated to the low level temperature
In the case of a, the temperature gradually decreases toward room temperature after deviating from the spot area of the recording light.

When the temperature of the magneto-optical disk 10 starts to decrease, the magnetization of the memory layer 13 is first recovered from the memory layer 13 and the switching layer 16 whose magnetization has been lost. At this time, the upward sublattice magnetization direction of the recording layer 15 is transferred to the memory layer 13. Then, the sublattice magnetization direction of the memory layer 13 is directed upward. When the temperature of the magneto-optical disk 10 further decreases, the switching layer 16
Also recovers the magnetization. At this time, the upward sublattice magnetization direction of the initialization layer 17 having a strong coercive force is transferred to the switching layer 16. Then, the sub-lattice magnetization direction of the switching layer 16 is also directed upward.

At this time, the exchange coupling force of the initialization layer 17 is transmitted to the recording layer 15 via the switching layer 16 in which the sublattice magnetization direction is directed upward. At this time, the sub-lattice magnetization direction of the recording layer 15 faces upward in the initial state (that is, the same direction as the sub-lattice magnetization direction of the initialization layer 17). Therefore, in the recording layer 15, the upward sublattice magnetization direction is maintained as it is.

As described above, the magneto-optical disk 10
When the low-level recording light is irradiated to the memory layer 13, the sub-lattice magnetization direction of the memory layer 13 in the heating region becomes upward similarly to the upward sub-lattice magnetization direction of the initialization layer 17 through the low-temperature process described above. Is held. Thus, FIG.
The sub-lattice magnetization direction of the memory layer 13 of the magneto-optical disk 10 is aligned with the direction of the magnetic field of the recording magnet when the power of the recording light to be irradiated is at a high level. It is kept aligned in the lattice magnetization direction (the direction opposite to the high level).

Therefore, information can be overwritten on the magneto-optical disk 10 only by modulating the power of the recording light between a high level and a low level in association with new information to be recorded. As described above, since the heated area during overwrite recording is smaller than the spot area of the recording light to be irradiated, information can be recorded at a high density in an area smaller than the spot area of the recording light.

Next, a description will be given of a process in which high-density information held in the memory layer 13 of the magneto-optical disk 10 of the present embodiment is reproduced by magnetic super-resolution. Here, as in the above description, the direction of the magnetic field of the recording magnet is “downward”, and the sublattice magnetization direction of the initialization layer 17 is “upward”. At the time of magnetic super-resolution reproduction of information, the magneto-optical disk 10
Then, the reproduction light set to the reproduction level (lower than the low level power of the recording light) is irradiated from the substrate 21 side.

When the reproducing light having the reproducing level power is applied to the magneto-optical disk 10, the RE-TM alloy layer 10a is formed at the center (reproducing area) of the spot area of the reproducing light.
Is heated to a temperature near the compensation temperature of the reproducing layer 11. In a region deviated from the center of the spot region of the reproduction light, the RE-TM alloy layer 10a is heated to a temperature lower than the compensation temperature of the reproduction layer 11.

At this time, the reproducing layer 11 changes from the state of in-plane magnetization to the state of perpendicular magnetization in the reproducing region heated to the vicinity of the compensation temperature. In the reproducing layer 11, in a region (mask region) within the spot region of the reproducing light but deviating from the center thereof, the state of the in-plane magnetization is maintained because the temperature is lower than the compensation temperature. In addition, since the temperature of the reproducing layer 11 outside the spot region of the reproducing light is almost the same as the room temperature, the entire surface is in-plane magnetized. Then, the reproducing layer 11 is coupled to the memory layer 13 only in the reproducing region changed to the state of perpendicular magnetization.

On the other hand, the RE-TM alloy layers 10a other than the reproducing layer 11 (for example, the memory layer 13, the recording layer 15, the switching layer 16, etc. in which information is stored) have a compensation temperature of the reproducing layer 11 by irradiation of reproducing light. Even if heated to the vicinity,
The coercive force of each layer (13, 15, 16) is only slightly reduced, and there is no change in the respective sublattice magnetization directions. Therefore, even when the reproduction light is irradiated, the high-density information recorded on the magneto-optical disk 10 is held in the memory layer 13.

As described above, since the reproducing layer 11 and the memory layer 13 are coupled only in the reproducing region where the reproducing layer 11 has changed to the state of perpendicular magnetization, only the reproducing region of the reproducing layer 11 has the memory. Part of the high-density information (sublattice magnetization direction) of the layer 13 is transferred. The reproduction of information by the reproduction light is performed by using the rotation of the polarization plane according to the sub-lattice magnetization direction when the linearly polarized reproduction light is reflected on the irradiation surface of the reproduction layer 11.

In the magneto-optical disk 10 shown in FIG. 1, an intermediate layer 14 was formed between the memory layer 13 and the recording layer 15. The exchange coupling force between the memory layer 13 and the recording layer 15 is adjusted by the intermediate layer 14. Therefore, at the time of magnetic super-resolution reproduction, even if the memory layer 13 is heated by the irradiation of the reproduction light and its coercive force decreases,
The sub-lattice magnetization direction of the memory layer 13 is reliably maintained.

As described above, the magneto-optical disk 10 on which both information overwrite recording and magnetic super-resolution reproduction are performed is performed.
Is excellent in the following points. First, in the process of overwrite recording, when the magnetization of the memory layer 13 recovers, it is necessary to transfer the sublattice magnetization direction of the recording layer 15 to the memory layer 13 in a good manner. Regarding this transfer, the following effects can be obtained in the magneto-optical disk 10.

That is, in the magneto-optical disk 10 shown in FIG. 1, the non-magnetic layer 12 was formed between the memory layer 13 and the reproducing layer 11. This nonmagnetic layer 12 is
Since it functions so as to substantially block the exchange coupling force between the recording layer 3 and the reproducing layer 11, the exchange coupling force from the recording layer 15 acts strongly on the memory layer 13. Therefore,
The memory layer 13 includes a reproducing layer 1 which is in-plane magnetized at room temperature.
1, the sub-lattice magnetization direction of the recording layer 15 is well transferred.

Second, a recording / reproducing apparatus for recording and reproducing information on and from the magneto-optical disk 10 needs to be downsized. With respect to this miniaturization, the magneto-optical disk 10 has the following operational effects. That is, in the magneto-optical disk 10 shown in FIG. 1, an initialization layer 17 for initializing the recording layer 15 and a switching layer 16 are laminated on the recording layer 15. Therefore, this magneto-optical disk 10
Therefore, there is no need to incorporate an initialization magnet for initializing the recording layer 15 in the recording / reproducing apparatus. Therefore, the recording / reproducing apparatus in this case is simply miniaturized without a built-in initialization magnet.

Third, in the magneto-optical disk 10 capable of performing both the overwrite recording of information and the magnetic super-resolution reproduction, it is necessary to reduce the film thickness. In this regard, the magneto-optical disk 10 has the following operational effects. That is, in the magneto-optical disk 10 shown in FIG. 1, the initialization operation for forcibly aligning the sub-lattice magnetization direction of the recording layer 15 in one direction is not the effect of the static magnetic field from the initialization magnet, but the initialization layer 17. , By the action of the exchange coupling force from the switching layer 16. Therefore, the thickness of the recording layer 15 can be reduced.

The magneto-optical disk 10 shown in FIG.
Then, the nonmagnetic layer 1 is disposed between the memory layer 13 and the reproducing layer 11.
2 was formed. Since the exchange coupling force between the memory layer 13 and the reproducing layer 11 becomes almost zero due to the nonmagnetic layer 12, the state of the in-plane magnetization at room temperature can be stabilized even if the thickness of the reproducing layer 11 is reduced. Can be held. Further, in the magneto-optical disk 10 shown in FIG. 1, the number of layers as a whole is smaller than that in the case where the initialization magnet is incorporated in the recording / reproducing apparatus (the above-described magnetostatic coupled MSR / DOW magneto-optical disk). Although the thickness increases by the amount of the layer 17 and the switching layer 16, the thickness of the recording layer 15 can be reduced, so that the total thickness is reduced.

Fourth, in the process of magnetic super-resolution reproduction, it is necessary to transfer the sublattice magnetization direction of the memory layer 13 to the reproducing layer 11 in a good manner. Regarding this transfer, the following effects can be obtained in the magneto-optical disk 10.

That is, in the magneto-optical disk 10 shown in FIG. 1, since the thickness of the recording layer 15 can be reduced as described above, the leakage magnetic field from the recording layer 15 is almost eliminated. Therefore, the sub-lattice magnetization direction of the memory layer 13 is satisfactorily transferred to the reproducing layer 11 without being affected by the recording layer 15. As described above, according to the magneto-optical disk 10 (FIG. 1) having the above configuration, both the overwrite recording of information and the magnetic super-resolution reproduction are performed well.

When the carrier-to-noise intensity ratio (CN ratio) of this magneto-optical disk 10 was actually measured, it was found that a good CN ratio of 46 dB was obtained as follows. The measurement of the CN ratio was performed with the power of the reproduction light at which the CN ratio became maximum. Further, the magneto-optical disk 10 is formed by simply combining the magnetostatic coupling type MSR system and the optical modulation overwriting system with the magnetostatic coupling MSR system.
Since the entire film thickness can be made smaller than that of the R / DOW magneto-optical disk, the recording sensitivity is good and the disk is practical.

In the magneto-optical disk 10 of the above-described embodiment, the composition of the memory layer 13 is Tb18Fe74Co8
However, a plurality of magneto-optical disks 10 having different compositions of the memory layer 13 were prepared, and their CN ratios were compared with each other. Table 1 shows the results of measuring the CN ratio for a plurality of magneto-optical disks 10 having different compositions of the memory layer 13. In this case, the thickness of the memory layer 13 is
The same as the magneto-optical disk 10 of the above-described embodiment,
5 nm. Of these results, the one in which the Tb composition of the memory layer 13 is 18% corresponds to the magneto-optical disk 10 of the above embodiment.

As shown in Table 1, a magneto-optical disk (compensation temperature lower than room temperature) in which the Tb composition of the memory layer 13 is 20% or less has a good CN ratio of 44 dB or more, but has a good Tb composition. It can be seen that when the temperature is 21% or more (the compensation temperature is higher than room temperature), the CN ratio decreases. The reason for the decrease in the CN ratio may be that if the composition of the memory layer 13 becomes rare earth metal sublattice dominant (RE rich), the sublattice magnetization direction of the memory layer 13 will not be transferred well to the reproducing layer 11.

From the above, the C of the magneto-optical disk 10
In order to improve the N ratio, it is preferable that the composition of the memory layer 13 be a composition having a compensation temperature lower than room temperature.

[Table 1] In the magneto-optical disk 10 of the above-described embodiment, the thickness of the memory layer 13 is set to 35 nm.
A plurality of magneto-optical disks 10 having different thicknesses were prepared, and their CN ratios were compared with each other.

Table 2 shows the results of measuring the CN ratio for a plurality of magneto-optical disks having different thicknesses of the memory layer 13. The composition of the memory layer 13 in this case is the same as that of the magneto-optical disk of the above-described embodiment.
It has a Tb composition of 18%. Of these results,
The memory layer 13 having a thickness of 35 nm corresponds to the magneto-optical disk 10 of the above embodiment.

As shown in Table 2, a magneto-optical disk having a memory layer 13 thicker than 25 nm and thinner than 45 nm has a good CN ratio of 45 dB or more, but has a CN ratio of 20 nm or less. , 50 nm or more, C
It can be seen that the N ratio decreases. The reason why the CN ratio decreases when the film thickness is 20 nm or less may be that the sublattice magnetization direction of the memory layer 13 is not transferred to the reproducing layer 11 satisfactorily during magnetic super-resolution reproduction. When the film thickness is 50
The reason why the CN ratio decreases when the thickness is not less than nm may be that the sub-lattice magnetization direction is not satisfactorily transferred from the recording layer 15 to the memory layer 13 during overwrite recording.

As described above, the C of the magneto-optical disk 10
In order to improve the N ratio, it is preferable that the thickness of the memory layer 13 be larger than 25 nm and smaller than 45 nm.

[Table 2] Further, in the magneto-optical disk 10 of the above-described embodiment,
Although the thickness of the recording layer 15 was set to 20 nm, a plurality of magneto-optical disks 10 having different thicknesses of the recording layer 15 were prepared, and their CN ratios were compared with each other. Table 3 shows the results of measuring the CN ratio for a plurality of magneto-optical disks having different recording layer 15 thicknesses. In this case, the initialization layer 17
Are all 30 nm.

As shown in Table 3, in a magneto-optical disk in which the recording layer 15 is thicker than 15 nm and thinner than 40 nm, the CN ratio is as good as 45 dB or more. It can be seen that the CN ratio is lowered, and overwrite recording cannot be performed for those having a diameter of 45 nm or more. The reason why the CN ratio decreases when the film thickness is 10 nm or less may be that the sublattice magnetization direction of the recording layer 15 is not accurately aligned with the recording magnetic field during overwrite recording. The reason why overwrite recording cannot be performed when the film thickness is 45 nm or more is considered that the sub-lattice magnetization direction is not satisfactorily transferred from the initialization layer 17 to the recording layer 15.

From the above, the C of the magneto-optical disk 10
In order to improve the N ratio, it is preferable that the thickness of the recording layer 15 be larger than 15 nm and smaller than 40 nm.

[Table 3] Further, in the magneto-optical disk 10 of the above-described embodiment, the thickness of the initialization layer 17 was set to 20 nm. However, a plurality of magneto-optical disks 10 having different thicknesses of the initialization layer 17 were prepared, and the CN ratio was adjusted. Compared to each other.

Table 4 shows the results of measuring the CN ratio for a plurality of magneto-optical disks having different thicknesses of the initialization layer 17. The thickness of the recording layer 15 in this case is 25 nm. As shown in Table 4, the initialization layer 1
It can be seen that the magneto-optical disk having a film thickness of 15 nm or more has a good CN ratio of 45 dB or more, but the disk having a film thickness of 10 nm or less cannot perform overwrite recording. The reason may be that the magnetization direction of the initialization layer 17 is reversed by the exchange coupling force from the recording layer 15.

From the above, the C of the magneto-optical disk 10
In order to improve the N ratio, it is preferable that the thickness of the initialization layer 17 be larger than 15 nm.

[Table 4] Further, in the magneto-optical disk 10 of the above-described embodiment,
Although the thickness of the recording layer 15 and the thickness of the initialization layer 17 were made equal, a plurality of magneto-optical disks 10 having a difference between the thickness of the recording layer 15 and the thickness of the initialization layer 17 were prepared. The CN ratio was compared to each other.

Table 5 shows the thickness of the recording layer 15 and the initialization layer 1
7 shows the results of measuring the CN ratio of a plurality of magneto-optical disks having different thicknesses from the thickness of the magneto-optical disk. In this case, the thickness of the recording layer 15 is all 20 nm. As shown in Table 5, a magneto-optical disk having a difference in film thickness of 30 nm or less has a good CN ratio of 45 dB or more.
It can be seen that when the difference in film thickness is 40 nm or more, the CN ratio decreases. The reason for this is that as the difference in film thickness increases, the leakage magnetic field from the initialization layer 17 increases,
It is considered that magnetic super-resolution reproduction becomes difficult.

From the above, the C of the magneto-optical disk 10
In order to improve the N ratio, the difference between the thickness of the recording layer 15 and the thickness of the initialization layer 17 is preferably set to 30 nm or less.

[Table 5] Further, the thickness of the recording layer 15 is set to 40 n
m (Table 3), the thickness of the initialization layer 17 is greater than 15 nm (Table 4), and the difference between the thickness of the recording layer 15 and the thickness of the initialization layer 17 is 30 nm or less (Table 5). The magneto-optical disk 10 thus obtained has a good CN ratio and good recording sensitivity, and is practical.

[0091]

As described above, according to the first aspect of the present invention, the information to be recorded is temporarily recorded on the recording layer and then transferred to the memory layer. When information is transferred to the memory layer, the recording layer is initialized by the initialization layer. The memory layer retains the information transferred from the recording layer as it is. Thus, the information to be recorded is finally held in the memory layer and overwritten. Further, in the information held in the memory layer, the sublattice magnetization direction of a part of the information is transferred to the reproducing layer via the nonmagnetic layer, and the information is reproduced by magnetic super-resolution. Therefore, even when the magneto-optical overwrite method and the magnetic super-resolution technique are combined, a high-speed magneto-optical recording medium with high recording capacity can be achieved while increasing the information rewriting speed. .

According to the second and sixth aspects of the present invention, the information can be easily overwritten simply by modulating the intensity of the recording light in association with new information. Further, according to the third, fourth and seventh aspects of the present invention, the sub-lattice magnetization direction of the memory layer is transferred only to the reproduction area smaller than the spot area of the reproduction light. Can be accurately reproduced.

According to the fifth aspect of the invention, the Curie temperature of each layer can be set within a practical temperature range. Further, the thermal stability of each layer is good and the thermal conductivity is high, so that information can be efficiently recorded. Furthermore, it is excellent in mass productivity and the production cost can be kept low. Furthermore, in the invention according to claim 8, since the sublattice magnetization direction of the memory layer is satisfactorily transferred to the reproducing layer during reproduction, the CN ratio is improved.

According to the ninth aspect of the present invention, the sublattice magnetization direction of the memory layer is satisfactorily transferred to the reproducing layer during reproduction, and the sublattice magnetization direction of the recording layer is satisfactorily transferred to the memory layer during recording. Therefore, the CN ratio becomes good. Further, according to the tenth aspect of the present invention, at the time of recording, the sublattice magnetization direction of the recording layer is satisfactorily reversed by the external magnetic field, and at the time of initialization of the recording layer, the sublattice magnetization direction of the initialization layer is favorable to the recording layer. , The CN ratio becomes good.

According to the eleventh aspect of the present invention, the magnetization direction of the sublattice of the initialization layer is always maintained in one direction without being reversed by the exchange coupling force from another magnetic layer such as the recording layer. In addition, the leakage magnetic field from the initialization layer is reduced, and during reproduction, the sublattice magnetization direction of the memory layer is satisfactorily transferred to the reproduction layer, so that the CN ratio is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a magneto-optical disk 10 according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Magneto-optical disk 10a Rare earth-transition metal (RE-TM) alloy layer 11 Reproducing layer 12 Nonmagnetic layer 13 Memory layer 14 Intermediate layer 15 Recording layer 16 Switching layer 17 Initialization layer 21 Substrate 22 Undercoat 23 Overcoat 24 Metal layer 25 Resin protective layer

Claims (11)

[Claims] 1. A recording layer on which information is recorded by inversion of a sub-lattice magnetization direction by at least an external magnetic field, and a sub-lattice magnetization direction of the recording layer formed between the recording layer and the substrate. A memory layer on which information is transferred and the information is retained; a reproducing layer formed between the memory layer and the substrate, wherein a sub-lattice magnetization direction of a partial region of the memory layer is transferred; A nonmagnetic layer formed between the layer and the memory layer, an initialization layer formed on the opposite side of the recording layer from the substrate, and forcibly aligning the sublattice magnetization direction of the recording layer in one direction; A switching layer formed between a recording layer and the initialization layer, which prevents transmission of exchange coupling force to the recording layer by the initialization layer when the sublattice magnetization direction of the recording layer is reversed by the external magnetic field; And is laminated Magneto-optical recording medium. 2. The magneto-optical recording medium according to claim 1, wherein the information held in the memory layer is a sub-lattice magnetization direction that is opposite to each other when the recording light to be irradiated is strong and weak. A magneto-optical recording medium characterized by being represented. 3. The magneto-optical recording medium according to claim 1, wherein the reproducing layer has a sub-lattice of the memory layer in a part of a region corresponding to a temperature distribution generated in the reproducing layer by the irradiated reproducing light. A magneto-optical recording medium wherein the magnetization direction is transferred. 4. The magneto-optical recording medium according to claim 3, wherein the partial area of the reproducing layer is an area whose temperature has become equal to or higher than a predetermined temperature by irradiation of the reproducing light. Magneto-optical recording medium. 5. The magneto-optical recording medium according to claim 1, wherein the reproducing layer, the memory layer, the recording layer, the switching layer, and the initialization layer are mainly composed of a rare earth metal and a transition metal. A magneto-optical recording medium characterized by being a body. 6. The magneto-optical recording medium according to claim 5, wherein a Curie temperature of the recording layer is higher than a Curie temperature of the memory layer and the switching layer, and lower than a Curie temperature of the initialization layer. A magneto-optical recording medium characterized by the above-mentioned. 7. The magneto-optical recording medium according to claim 5, wherein the reproducing layer is a magnetic material whose compensation temperature is higher than room temperature. 8. The magneto-optical recording medium according to claim 5, wherein the memory layer is a magnetic material whose compensation temperature is lower than room temperature. 9. The magneto-optical recording medium according to claim 5, wherein the thickness of the memory layer is greater than 25 nm and 45 nm.
A magneto-optical recording medium characterized by being thinner. 10. The magneto-optical recording medium according to claim 5, wherein the thickness of the recording layer is larger than 15 nm and smaller than 40 nm. 11. The magneto-optical recording medium according to claim 10, wherein an absolute value of a difference between a thickness of the recording layer and a thickness of the initialization layer is smaller than 30 nm, and a thickness of the initialization layer. A magneto-optical recording medium having a thickness greater than 15 nm.