JPH1186367A - Magnet-optical recording medium and its reproduction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium capable of enabling magnetic domain expansion reproduction by without alternating the direction of magnetic fields and is capable of suppressing electric power consumption accordingly and increasing a reproduction rate (data transfer rate) and its reproduction method. SOLUTION: This medium has a reproducing layer which indicates perpendicular magnetization, a memory layer which exhibits the perpendicular magnetization and a magnetic field auxiliary layer which exhibits the perpendicular magnetization at least at room temp. on a substrate. Further, the medium has a first shielding layer for shielding the exchange bond of the reproducing layer with the memory layer between the reproducing layer and the memory layer and a second shielding layer for shielding the exchange bond of the memory layer with the magnetic field auxiliary between the memory layer and the magnetic field auxiliary layer.

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, and more particularly to a magneto-optical recording medium of the type for reproducing information recorded at high density with magnetic super-resolution.

[0002]

2. Description of the Related Art Information can be recorded at high density.
An optical recording medium capable of high-speed reproduction has attracted attention as a recording medium for audio and images, and further for a computer. In particular, a magneto-optical recording medium, which is a type of rewritable type, is capable of rewriting information more than one million times, and is becoming popular mainly as a recording medium for computers. Recording on a magneto-optical recording medium is performed by forming a perpendicular magnetization region in the opposite direction called a mark in a magnetic layer perpendicularly magnetized in a predetermined direction.
Reproduction is performed by irradiating a portion to be reproduced with linearly polarized light and detecting a difference in rotation of the polarization plane between the mark region and the other region.

Further, recently, opportunities for recording or reproducing a large amount of information such as image information have been increasing. Under such circumstances, there is an increasing demand for recording more information on an optical recording medium or for accurately reproducing the information. Various approaches have been taken to meet that demand. First, it is conceivable to reduce the track pitch of an optical disc in order to increase the radial recording density. Conventional track pitch is
1.6μm was standard, but recently 1.4μm and 1.2μm
m, and there is a move to 1.0 μm. In order to reduce the track pitch, it is necessary to reduce the recording mark width. To increase the recording density in the circumferential direction, it is necessary to reduce the length of the recording mark.

To reduce the width and length of a recording mark,
The sensitivity of the recording medium may be set so that a recording mark is formed only in a high energy region near the center of the recording beam. In this way, relatively small marks can be formed in principle. That is, when recording, if the composition of the magnetic layer is set so that a recording mark is formed only in a high-temperature portion near the center of the recording beam, high-density recording can be performed.

However, the problem lies in reproduction. Reproduction is performed by optically detecting a mark in the beam spot. Therefore, it is necessary to basically read only one mark from the reproduction beam spot. If a plurality of marks are read from the beam spot, a plurality of information are mixed, and it is not possible to correctly recognize what is necessary information. Such a mixture of a plurality of pieces of information in the beam spot is called optical crosstalk.

For example, in the case of an infrared laser, the beam spot diameter can be reduced to only about 1.0 μm by an ideal optical system. Therefore, in the radial direction, the track pitch is 1.4
If it is smaller than about μm, marks recorded on adjacent tracks will be reproduced simultaneously. If the mark length or mark interval is significantly smaller than 1.0 μm, the preceding and succeeding marks will be reproduced simultaneously.

Therefore, it is conceivable to shorten the wavelength of the reproduction beam. This is because how small the beam can be narrowed is proportional to the wavelength of the beam. That is, by shortening the wavelength of the beam, the reproduction beam spot size is reduced, thereby enabling reproduction of information recorded at high density. If this is realized, the problem of optical crosstalk can be avoided. However, the wavelength of a semiconductor laser that can be used as a light source of an optical pickup has a limit in terms of its output and stability. For example, semiconductor lasers with a wavelength of 830 nm have been generally used in the past, but despite the fact that long wavelengths were required and wavelengths were shortened, the wavelength of 680 nm has only recently become mainstream. It is. That is, the reduction rate of the beam size due to the reduction of the wavelength from 830 nm to 680 nm is only about 20%. Therefore, it is considered difficult at present to reduce the beam spot size dramatically to 1/3 or 1/4 of the current size by shortening the wavelength of the light source.

In response to this problem, an epoch-making reproduction method capable of accurately reproducing information recorded at a high density and a recording medium used for the method have been invented. This is called Magnetically-induced Super Resolution: M
SR) Playback and media. The basic idea of this method is as follows. Although the temperature of the recording medium rises due to the irradiation of the reproduction beam, since the medium is moving, the temperature on the rear side in the reproduction beam spot becomes relatively high due to the heat storage effect. If a part of the beam spot is magnetically masked using this temperature distribution characteristic and only the unmasked part (opening) is reproduced, only the information of a small part in the spot can be reproduced. That is,
This has substantially the same effect as reducing the reproduction beam spot size.

Specifically, (1) a FAD type in which a low-temperature portion in a reproducing beam spot, that is, an opening is provided in front of a traveling direction in a beam spot (a high-temperature portion becomes a mask) (Japanese Patent Laid-Open No. 93056), (2) There are RAD type and CAD type in which the high-temperature portion, that is, the back of the beam spot becomes an opening (the low-temperature portion becomes a mask). A double mask type has been proposed in which a portion having the largest light quantity at the center of the laser spot is reproduced.

Here, the principle of the CAD type magnetic super-resolution reproduction utilizing the change in the magnetization direction due to the change in the magnetic coupling force will be described. FIG. 10B shows a cross section of a main part of a CAD type magneto-optical recording medium and a temperature distribution of a part irradiated with a reproducing beam. The magneto-optical recording medium has two magnetic layers, and information is recorded in the form of the perpendicular magnetization direction of the memory layer. A reproduction layer is provided in contact with the memory layer. The magnetization of the reproducing layer is an in-plane magnetization at a temperature lower than a predetermined temperature, but becomes a perpendicular magnetization in the same direction as the magnetization of the memory layer due to an exchange coupling force with the magnetization of the memory layer at a temperature higher than the predetermined temperature. The predetermined temperature is set so that a region which is perpendicularly magnetized by the irradiation of the reproduction beam becomes a small region near the center of the temperature distribution. As a result, as shown in FIG. 10A, a mark is formed on the reproducing layer only in a high-temperature region of a part of the reproducing beam spot. In other low temperature regions, no mark is formed on the reproducing layer. Therefore, only the information in the high temperature region of the reproduction beam spot is read. Then, even if the mark is within the reproduction beam spot, the mark that is out of the high temperature region is not read.

However, in the magnetic super-resolution reproduction, the size of the recording mark is considerably smaller than the reproduction beam spot size, so that there is a problem that the reproduction signal intensity is small.
On the other hand, a method has been proposed which enables reproduction of information recorded at high density by a principle different from magnetic super-resolution reproduction. This is called magnetic domain expansion reproduction. In the magnetic domain expansion reproduction, the light source wavelength and the size of the reproduction beam spot are the same as in the prior art, as in the magnetic super-resolution reproduction.

As shown in FIG. 9, the magneto-optical recording medium used for the magnetic domain expansion reproduction is composed of a multilayer film including a reproduction layer, a blocking layer, and a memory layer. When reproducing from this recording medium, the direction of an external magnetic field (reproducing magnetic field) is modulated (alternating) at twice the maximum recording frequency. That is, upward and downward are repeated. At that time, at the moment when the position of the high-temperature portion in the reproducing beam spot coincides with the center of the mark to be reproduced, the reproduction magnetic field is synchronized so as to have an upward or downward maximum value. Then, the reproducing layer is heated by the irradiation of the reproducing beam, and magnetization is generated in the reproducing layer under the influence of the magnetic field due to the magnetization of the memory layer. Here, when the reproducing magnetic field is applied in the same direction as the magnetization of the memory layer, the magnetization region generated in the reproducing layer expands. That is, the mark is enlarged, and expands to the same size as the reproduction beam spot. When the reproducing magnetic field is applied in a direction opposite to the magnetization of the memory layer, the magnetization region generated in the reproducing layer is reduced or disappears. That is, the mark shrinks or disappears. Therefore, after the mark is enlarged and reproduced on the reproduction layer, the mark is immediately reduced or eliminated. Thus, when reproducing a predetermined mark, the mark reproduced immediately before does not become an obstacle.

In the magnetic domain expansion reproduction, since a small recording mark is reproduced while being enlarged to a size close to a reproduction beam spot, the reproduction signal level is large. This is more advantageous than magnetic super-resolution reproduction.

[0014]

However, as described above, in magnetic domain expansion reproduction, it is necessary to alternate the direction of the magnetic field by the external magnetic field (reproduction magnetic field) at a high speed.
Therefore, there is a problem that power consumption is large. In addition, since there is a limit to the speed (frequency) at which the direction of the magnetic field is alternated, there is a problem that the reproduction speed (data transfer rate) cannot be made too high.

The present invention solves the above-mentioned problems, and enables magnetic domain expansion reproduction without changing the direction of the magnetic field, thereby reducing power consumption and increasing the reproduction speed (data transfer rate). It is an object to provide a magneto-optical recording medium and a reproducing method therefor.

[0016]

According to a first aspect of the present invention, there is provided a semiconductor device comprising: a reproducing layer exhibiting perpendicular magnetization; a memory layer exhibiting perpendicular magnetization; and a magnetic field auxiliary layer exhibiting perpendicular magnetization at least at room temperature. A magneto-optical recording medium having a first blocking layer between the reproducing layer and the memory layer for blocking exchange coupling between the reproducing layer and the memory layer, and a first blocking layer between the memory layer and the magnetic field auxiliary layer. And a second blocking layer for blocking exchange coupling between the memory layer and the magnetic field auxiliary layer. With such a configuration, the exchange coupling force between the memory layer, the reproducing layer, and the magnetic field auxiliary layer is cut off, so that it is possible to provide a magneto-optical recording medium that can reproduce the magnetic domain without changing the direction of the magnetic field. Become.

According to a second aspect of the present invention, in the magneto-optical recording medium according to the first aspect, the magnetic field auxiliary layer has a compensation temperature between room temperature and Curie temperature. With such a configuration, it is possible to provide a magneto-optical recording medium that can more reliably reproduce magnetic domain expansion without an alternating magnetic field. According to a third aspect of the present invention, in the magneto-optical recording medium according to the second aspect, the compensation temperature of the magnetic field auxiliary layer is 80 ° C. or more and 150 ° C.
It is characterized by the following.

According to a fourth aspect of the present invention, in the magneto-optical recording medium of the first aspect, the reproducing layer has a compensation temperature between room temperature and Curie temperature. With such a configuration, it is possible to provide a magneto-optical recording medium that can more reliably reproduce magnetic domain expansion without an alternating magnetic field. Claim 5
The invention described in Item 4 is characterized in that, in the magneto-optical recording medium described in Item 4, the compensation temperature of the reproducing layer is 80 ° C. or more and 150 ° C. or less.

According to a sixth aspect of the present invention, in the magneto-optical recording medium of the first aspect, the reproducing layer has a compensation temperature near room temperature. According to a seventh aspect of the present invention, in the magneto-optical recording medium according to the first aspect, one or both of the first blocking layer and the second blocking layer are made of a dielectric material or a nonmagnetic metal. .

According to an eighth aspect of the present invention, in the magneto-optical recording medium according to the first aspect, the memory layer is formed of a magnetic layer in which transition metal sublattice magnetization is dominant. With this configuration, the magnetization direction of the memory layer does not change even when the temperature rises due to the irradiation of the reproduction beam.
A magneto-optical recording medium that can reliably reproduce magnetic domains without an alternating magnetic field can be obtained.

According to a ninth aspect of the present invention, in the magneto-optical recording medium according to the first aspect, the Curie temperature of the magnetic field auxiliary layer is higher than the Curie temperature of the memory layer, and the mark of the reproducing layer is reduced or eliminated. Required magnetic field Hsc (Tl)
Is a temperature T higher than room temperature and lower than the compensation temperature of the magnetic field auxiliary layer.
1, the magnetic field −Hnc (Th) required to satisfy −Hsc (Tl)> Hw (T1) + Hz (T1) and generate a new mark in the reproducing layer is higher than the compensation temperature of the magnetic field auxiliary layer. Temperature Th lower than the Curie temperature of the memory layer
In the equation, -Hw (Th) <Hnc (Th) -Hz (Th) <Hw
(Th), and the magnetic field −Hexp (Th) required to enlarge the mark of the reproduction layer is Hexp (Th) at a temperature Th higher than the compensation temperature of the magnetic field auxiliary layer and lower than the Curie temperature of the memory layer. −Hz (Th) <Hw (Th).

Here, Hw represents the magnitude of the magnetization given to the reproducing layer by the magnetization of the memory layer, and Hz represents the magnitude of the magnetization given to the reproducing layer by the magnetization of the magnetic field auxiliary layer. The invention according to claim 10, further comprising a reproducing layer exhibiting perpendicular magnetization, a memory layer exhibiting perpendicular magnetization, and a magnetic field auxiliary layer exhibiting perpendicular magnetization at least at room temperature, on the substrate, wherein the reproducing layer and the memory A first blocking layer that blocks exchange coupling between the reproduction layer and the memory layer, between the memory layer and the magnetic field auxiliary layer; Irradiating a magneto-optical recording medium having a second blocking layer that blocks exchange coupling between the two while modulating the beam intensity into binary of high intensity and low intensity, and reflecting light reflected by the magneto-optical recording medium. The recorded information is reproduced by detecting and demodulating. With such a configuration, it is possible to provide a reproducing method capable of reliably reproducing the magnetic domain on the magneto-optical recording medium without an alternating magnetic field.

According to an eleventh aspect of the present invention, in the reproducing method of the magneto-optical recording medium according to the tenth aspect, the frequency at which the beam intensity is modulated into two levels of high intensity and low intensity is equal to the frequency of the magneto-optical recording medium. Of the minimum recording frequency of the information recorded on the medium,
It is characterized by being at least twice or more.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the basic structure of a magneto-optical recording medium capable of reproducing a magnetic domain in an enlarged manner according to the present invention. FIG. 2 is a sectional view showing the structure of the magneto-optical recording medium which can be reproduced in the magnetic domain manufactured this time. In FIG.
The disc substrate 1 has a diameter of 86 mm, an inner diameter of 15 mm, and a thickness of 1.2 mm
Is a disc-shaped polycarbonate substrate. On its surface,
A guide groove forming a land portion and a groove portion is formed in a spiral shape. On the surface of the disk substrate 1, a silicon nitride layer 2, a reproducing layer 3, a first blocking layer 4, a memory layer 5, a second blocking layer 6, a magnetic field auxiliary layer 7, a silicon nitride layer 8,
And a resin protective layer 9.

The magnetic field auxiliary layer preferably has a compensation temperature between the temperature reached by the irradiation of the reproduction beam and room temperature, and more preferably the compensation temperature is 80 ° C. or more and 150 ° C. or less. In this case, the reproducing layer desirably has a compensation temperature near room temperature. If the magnetic field auxiliary layer does not have a compensation temperature between room temperature and its Curie temperature, the reproduction layer must have a compensation temperature between the temperature reached by the irradiation of the reproduction beam and room temperature. Is desirable. In this case, the compensation temperature of the reproducing layer is more desirably 80 ° C. or lower.

The first blocking layer may be any material as long as it cuts the magnetization between the reproducing layer and the memory layer (prevents the state from being exchange-coupled). preferable. Further, it may be composed of two or more layers of a dielectric layer and a non-magnetic metal layer. Also, the second blocking layer may be made of any material that cuts the magnetization between the memory layer and the magnetic field auxiliary layer, but is more preferably a dielectric or non-magnetic metal. Further, it may be constituted by two layers of a dielectric layer and a non-magnetic metal layer.

It is desirable that the memory layer be formed of a magnetic layer in which transition metal sublattice magnetization is dominant. The Curie temperature of the magnetic field auxiliary layer is higher than the Curie temperature of the memory layer, and the magnetic field Hsc (Tl) required to reduce or eliminate the magnetization region of the reproducing layer is higher than room temperature and lower than the compensation temperature of the magnetic field auxiliary layer. At the temperature Tl, the magnetic field −Hnc (Th) that satisfies the relationship of −Hsc (Tl)> Hw (Tl) + Hz (Tl) and generates a new magnetized region in the reproducing layer is represented by T below the compensation temperature of the memory layer and below the Curie temperature of the memory layer
h, the following equation is given: -Hw (Th) <Hnc (Th) -Hz (Th) <Hw
(Th), the magnetic field -Hexp (Th) required to expand the magnetization region of the reproducing layer is expressed by the following equation at a temperature Th higher than the compensation temperature of the magnetic field auxiliary layer and lower than the Curie temperature of the memory layer. It is desirable to satisfy the relationship of Hexp (Th) -Hz (Th) <Hw (Th).

Here, Hw represents the magnetic field applied to the reproducing layer by the magnetization of the memory layer, and Hz represents the magnetic field applied to the reproducing layer by the magnetization of the auxiliary magnetic layer. Next, the principle of the reproducing method of the present invention will be described by taking the invention described in claim 2 of the present application as an example. First, the state without beam irradiation,
That is, at room temperature, the magnetizations of the reproducing layer and the magnetic field auxiliary layer are aligned in one direction. In the memory layer, information is recorded in the form of upward and downward magnetized regions (marks). For example, FIG. 3 shows a state in which the magnetizations of the reproducing layer and the magnetic field auxiliary layer are aligned downward, and information is recorded in the memory layer in the form of upward and downward magnetized regions (marks).

A reproduction beam is irradiated to reproduce the recording medium in this state. The intensity of the reproduction beam is continuously modulated into two levels of high intensity and low intensity. The high intensity in this case is different from the intensity when the magnetization of the memory layer is reversed during recording. Also,
The low intensity may be the same intensity as the intensity when reversing the magnetization of the memory layer during recording, or may be a different intensity.

First, the operation in the region where the magnetization of the memory layer is upward (the region where the mark is formed) will be described. The recording medium is heated by the irradiation of the reproducing beam of high intensity, and the temperature rises. In the magnetic field auxiliary layer, the magnetization is reversed from downward to upward in a region exceeding the compensation temperature, that is, in a high-temperature region. That is, an upward magnetization region is generated. The reproducing layer is affected by a magnetic field (static magnetic field) from the memory layer as the temperature rises, thereby generating an upward magnetization region in the same direction as the magnetization direction of the memory layer. The upward magnetization region of the reproducing layer expands under the influence of the static magnetic field from the upward magnetization region of the magnetic field auxiliary layer, and has a size close to the reproducing beam spot.
This state is shown in FIG. If the reproducing beam is changed to a low intensity immediately thereafter, the temperature of the magnetic field auxiliary layer becomes equal to or lower than the compensation temperature, so that the magnetization of the magnetic field auxiliary layer becomes downward. As a result, the enlarged upward magnetization region of the reproducing layer is reduced or eliminated. This state is shown in FIG. That is, reproduction is performed only while the reproducing layer is at a high temperature by irradiating the reproducing beam with high intensity.

Next, the operation in the region where the magnetization of the memory layer is directed downward (region where no mark is formed) will be described. The recording medium is heated by the irradiation of the reproducing beam of high intensity, and the temperature rises. In the magnetic field auxiliary layer, the magnetization is reversed from downward to upward in a region exceeding the compensation temperature, that is, in a high-temperature region. That is, an upward magnetization region is generated. The reproducing layer is affected by a magnetic field (static magnetic field) generated from the magnetization of the memory layer as the temperature rises, whereby a force acts to generate the same downward magnetization region as the magnetization of the memory layer. At the same time, the static magnetic field from the upward magnetization region of the magnetic field auxiliary layer applies a force to generate an upward magnetization region in the reproducing layer. However, since the static magnetic field from the memory layer is strong,
No upward magnetization region is generated in the reproducing layer. If the reproducing beam is changed to a low intensity immediately thereafter, the temperature of the magnetic field auxiliary layer becomes equal to or lower than the compensation temperature, so that the magnetization of the magnetic field auxiliary layer becomes downward. Needless to say, the magnetization of the reproducing layer does not change and remains downward.

Next, another embodiment of the present invention will be described using the invention described in claim 4 as an example. First,
In a state where no beam is irradiated, that is, at room temperature, the magnetizations of the reproducing layer and the magnetic field auxiliary layer are aligned in one direction. In the memory layer, information is recorded in the form of upward and downward magnetized regions (marks). For example, in FIG. 6, the magnetization of the reproducing layer is aligned downward, and the magnetization of the magnetic field auxiliary layer is aligned upward. Then, a state is shown in which information is recorded in the memory layer in the form of upward and downward magnetized regions (marks).

A reproducing beam is irradiated to reproduce the recording medium in this state. The intensity of the reproduction beam is continuously modulated into two levels of high intensity and low intensity. The high intensity in this case is different from the intensity when the magnetization of the memory layer is reversed during recording. Also,
The low intensity may be the same intensity as the intensity when reversing the magnetization of the memory layer during recording, or may be a different intensity.

First, the operation in the region where the magnetization of the memory layer is upward (the region where the mark is formed) will be described. The recording medium is heated by the irradiation of the reproducing beam of high intensity, and the temperature rises. In the reproducing layer, the magnetization is inverted from downward to upward in a region exceeding the compensation temperature, that is, in a high-temperature region. That is, an upward magnetization region is generated. Then, the upward magnetized region is affected by the upward magnetic field (static magnetic field) from the memory layer, and further expands by the influence of the static magnetic field from the upward magnetized region of the magnetic field auxiliary layer. become. This state is shown in FIG. When the reproducing beam is immediately changed to a low intensity, the upward magnetization region of the reproducing layer which has been expanded overcomes the influence of the upward magnetic field from the memory layer and the magnetic field auxiliary layer because the temperature of the reproducing layer becomes equal to or lower than the compensation temperature. And shrink or disappear. This state is shown in FIG. That is, reproduction is performed only while the reproducing layer is at a high temperature by irradiating the reproducing beam with high intensity.

Next, the operation in a region where the magnetization of the memory layer is directed downward (region where no mark is formed) will be described. The recording medium is heated by the irradiation of the reproducing beam of high intensity, and the temperature rises. In the reproducing layer, the magnetization tends to reverse from downward to upward in a region exceeding the compensation temperature, that is, in a high-temperature region. However, since the downward static magnetic field from the memory layer is strong, no upward magnetization region is generated in the reproducing layer. If the reproducing beam is changed to a low intensity immediately thereafter, the temperature of the reproducing layer becomes equal to or lower than the compensation temperature, and it goes without saying that the magnetization of the reproducing layer does not change and remains downward.

[0036]

Embodiment 1 (Production of Magneto-Optical Disk) First, a sputtering apparatus is prepared. A polycarbonate substrate having a diameter of 86 mm is set on a substrate carrier of a sputtering apparatus. Guide grooves having a pitch of 1.4 μm are spirally formed on the surface of the substrate.

Next, the substrate carrier on which the substrate is set is transported into the sputtering chamber of the sputtering apparatus. Next, the inside of the chamber is 5 × exp (−5) Pa
After evacuation to the following degree of vacuum, argon gas and nitrogen gas are introduced into the chamber, reactive sputtering is performed with a silicon target, and the silicon nitride layer is 70 nm thick.
Form a film.

Next, the substrate carrier is moved to another sputtering chamber, and sputtering is performed with a GdFeCo alloy target while introducing argon gas again, and Gd25Fe60Co15 (atomic%, Gd25%, Fe60%, Co15
%, The same applies hereinafter) on the silicon nitride layer in various thicknesses of thickness 20. Next, a first barrier layer is formed to a thickness of 15 nm on the reproducing layer by the same procedure as that for forming the first silicon nitride layer.

Next, the substrate and the substrate carrier are simultaneously rotated while simultaneously performing sputtering with a target of Tb which is a rare earth metal and an alloy target of Fe and Co which are transition metals, so that a region mainly composed of Tb and a region mainly composed of FeCo are formed. A memory layer of Tb21Fe63Co16 having a structure of being alternately stacked is formed to a thickness of 20 nm on the first blocking layer. Next, a second blocking layer is formed to a thickness of 15 nm on the memory layer by the same procedure as that for forming the first silicon nitride layer.

Next, the substrate and the substrate carrier are simultaneously rotated while performing binary simultaneous sputtering with a target of Tb which is a rare earth metal and a target of FeCo which is a transition metal, so that a region mainly composed of Tb and a region mainly composed of FeCo are formed. The second magnetic field auxiliary layer of Tb23Fe8Co69 having a structure of alternately laminating
A film having a thickness of 20 nm is formed on the blocking layer. Next, a silicon nitride layer having a thickness of 70 nm is formed on the initialization layer by the same procedure as that for forming the first silicon nitride layer.

After the film is formed by sputtering according to the above procedure, a resin protective film is further applied to form a magneto-optical disk having a magnetic layer configuration shown in FIG. 2, and the magnetization direction is set to a predetermined value by an external magnetic field. Initialize in the same direction. (Evaluation by recording / reproducing) Next, a magneto-optical recording / reproducing apparatus is prepared. This device has an optical pickup having a recording magnetic field whose intensity can be changed and a semiconductor laser having a wavelength of 680 nm as a light source.

The above-mentioned magneto-optical disk is set in the magneto-optical recording / reproducing apparatus and rotated at a linear velocity of 9.0 m / s. The laser beam condensed by the objective lens of the optical pickup is irradiated onto the disk surface while modulating the duty ratio to 50% between 8.0mW and 0.5mW at 30MHz at a mark length of 0.15μ.
Recording is performed so that m and the distance between marks are 0.15 μm. Next, the disc surface is irradiated with a laser beam while modulating the duty ratio of 50% between 4.0 mW and 0.5 mW at a frequency of 50% at 60 MHz to perform reproduction, and a C / N value is measured. As a result, it can be seen that a sufficiently high C / N value can be obtained even when reproducing a small mark.

[0043]

Embodiment 2 A magneto-optical disk is manufactured in the same procedure as in the embodiment, except that both the first blocking layer and the second blocking layer are formed of nonmagnetic metal Cr. Then, recording and reproduction are performed in the same manner as in Example 1, and the C / N value is measured. As a result, it can be seen that a sufficiently high C / N value can be obtained even when reproducing a small mark.

[0044]

Comparative Example 1 Next, the information recorded in Example 1 was
With the laser beam intensity kept constant at 3.0 mW, the disk surface is irradiated for reproduction to measure the C / N value. As a result, it is understood that a sufficiently high C / N value cannot be obtained even when a small recording mark is reproduced by the conventional reproducing method.

[0045]

As described above, according to the first aspect of the present invention, the first blocking layer for blocking exchange coupling between the reproducing layer and the memory layer is provided between the reproducing layer and the memory layer. And a second blocking layer that blocks exchange coupling between the memory layer and the magnetic field auxiliary layer between the memory layer and the magnetic field auxiliary layer.
As a result, the exchange coupling force between the memory layer, the reproducing layer, and the magnetic field auxiliary layer is cut off, whereby it is possible to provide a magneto-optical recording medium capable of reproducing the magnetic domain without changing the direction of the magnetic field.

According to the second aspect of the present invention, the magnetic field auxiliary layer has a compensation temperature between room temperature and Curie temperature. As a result, it is possible to provide a magneto-optical recording medium capable of reproducing a magnetic domain in an enlarged manner without an alternating magnetic field. According to the third aspect of the invention, the compensation temperature of the magnetic field auxiliary layer is set to 80 ° C. or more and 150 ° C. or less. As a result, it is possible to provide a magneto-optical recording medium that can more reliably reproduce magnetic domain expansion without an alternating magnetic field.

According to the fourth aspect of the present invention, the reproducing layer has a compensation temperature between room temperature and Curie temperature. as a result,
Even with this configuration, a magneto-optical recording medium capable of reproducing a magnetic domain without an alternating magnetic field can be obtained. In the invention according to claim 5, the compensation temperature of the reproducing layer is set to 80 ° C. or less. As a result, a magneto-optical recording medium capable of magnetic domain expansion reproduction without an alternating magnetic field can be more reliably provided by this configuration.

According to a sixth aspect of the present invention, the reproducing layer has a compensation temperature near room temperature. As a result, it is possible to provide a magneto-optical recording medium capable of reproducing a magnetic domain in an enlarged manner without an alternating magnetic field. The invention according to claim 7 is characterized in that the first barrier layer and the second
Either or both of the blocking layers are made of a dielectric or non-magnetic metal. As a result, the magnetization between the reproducing layer and the memory layer, or between the memory layer and the magnetic field auxiliary layer can be more reliably cut off, and a magneto-optical recording medium that can surely reproduce magnetic domain expansion can be obtained.

The invention according to claim 8 is characterized in that the memory layer is formed of a magnetic layer in which the transition metal sublattice magnetization is dominant. With such a configuration, the magnetization direction of the memory layer does not change in the process of increasing the temperature by the irradiation of the reproducing beam, so that a magneto-optical recording medium that can reliably and reliably reproduce the magnetic domain without an alternating magnetic field can be obtained. Claim 9
According to the invention described in (1), the Curie temperature of the magnetic field auxiliary layer is higher than the Curie temperature of the memory layer, and the magnetic field Hsc (Tl) required to reduce or eliminate the mark of the reproducing layer is higher than room temperature and the compensation temperature of the magnetic field auxiliary layer is higher. At the lower temperature Tl, -Hsc (Tl)> Hw (Tl) + Hz (Tl) and the magnetic field -Hnc (Th) required to generate a new mark in the reproducing layer is compensated for by the magnetic field auxiliary layer. Temperature Th higher than the temperature and lower than the Curie temperature of the memory layer
In the equation, -Hw (Th) <Hnc (Th) -Hz (Th) <Hw
(Th), and the magnetic field −Hexp (Th) required to enlarge the mark of the reproduction layer is Hexp (Th) at a temperature Th higher than the compensation temperature of the magnetic field auxiliary layer and lower than the Curie temperature of the memory layer. −Hz (Th) <Hw (Th). As a result, it is possible to provide a magneto-optical recording medium that can more reliably and reliably reproduce magnetic domain expansion without an alternating magnetic field.

According to a tenth aspect of the present invention, irradiation is performed while modulating the beam intensity into binary values of high intensity and low intensity, and the light reflected by the magneto-optical recording medium is detected and demodulated. Play the recorded information. As a result, it is possible to provide a reproducing method that can surely reproduce the magnetic domain in the magneto-optical recording medium without an alternating magnetic field. According to an eleventh aspect of the present invention, the frequency at which the beam intensity is modulated into a binary value of high intensity and low intensity is at least twice the minimum recording frequency of the information recorded on the magneto-optical recording medium. As a result, it is possible to reliably perform magnetic domain expansion reproduction while the recorded mark passes through the reproduction beam spot.

As described above, since it is not necessary to alternate the direction of the magnetic field, the power consumption can be reduced.
A magneto-optical recording medium having a high reproduction speed (data transfer rate) and a reproduction method thereof can be provided.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view showing a configuration of a basic layer of a magneto-optical recording medium according to the present invention.

FIG. 2 is a vertical sectional view showing a configuration of a magneto-optical recording medium according to Embodiment 1 of the present invention.

FIG. 3 is a vertical sectional view showing a magnetization state when recording is performed on the magneto-optical recording medium according to the first embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view illustrating a magnetization state when a magneto-optical recording medium according to Embodiment 1 of the present invention is irradiated with a high-intensity reproduction beam.

FIG. 5 is a vertical sectional view showing a magnetization state when the magneto-optical recording medium according to the first embodiment of the present invention is irradiated with a low-intensity reproducing beam.

FIG. 6 is a vertical sectional view showing a magnetization state when recording is performed on a magneto-optical recording medium according to Example 4 of the present invention.

FIG. 7 is a vertical sectional view showing a magnetization state when a magneto-optical recording medium according to Example 4 of the present invention is irradiated with a high-intensity reproducing beam.

FIG. 8 is a vertical sectional view showing a magnetization state when a low-intensity reproduction beam is irradiated on a magneto-optical recording medium according to Example 4 of the present invention.

FIG. 9 is a vertical sectional view showing a configuration of a magneto-optical recording medium used in a conventional magnetic domain enlarging and reproducing method.

FIG. 10 is a conceptual diagram illustrating the principle of CAD magnetic super-resolution reproduction.

Claims (11)

[Claims] 1. A magneto-optical recording medium having, on a substrate, a reproduction layer exhibiting perpendicular magnetization, a memory layer exhibiting perpendicular magnetization, and a magnetic field auxiliary layer exhibiting perpendicular magnetization at least at room temperature. A first blocking layer that blocks exchange coupling between the reproducing layer and the memory layer between the memory layers; and a memory layer and the magnetic field auxiliary layer between the memory layer and the magnetic field auxiliary layer A magneto-optical recording medium, comprising a second blocking layer for blocking exchange coupling between the layers. 2. The magneto-optical recording medium according to claim 1, wherein the magnetic field auxiliary layer has a compensation temperature between room temperature and Curie temperature. 3. The magneto-optical recording medium according to claim 2, wherein the compensation temperature of the magnetic field auxiliary layer is 80 ° C. or more and 150 ° C. or less. 4. The magneto-optical recording medium according to claim 1, wherein the reproducing layer has a compensation temperature between room temperature and Curie temperature. 5. The magneto-optical recording medium according to claim 4, wherein the compensation temperature of the reproducing layer is 80 ° C. or less. 6. The magneto-optical recording medium according to claim 1, wherein the reproducing layer has a compensation temperature near room temperature. 7. The magneto-optical recording medium according to claim 1, wherein one or both of the first blocking layer and the second blocking layer are made of a dielectric material or a non-magnetic metal. . 8. The magneto-optical recording medium according to claim 1, wherein the memory layer comprises a magnetic layer having a transition metal sublattice magnetization dominant. 9. The magneto-optical recording medium according to claim 1, wherein the Curie temperature of the magnetic field auxiliary layer is higher than the Curie temperature of the memory layer, and the magnetic field Hsc (Tl) required to reduce or eliminate the mark on the reproduction layer. At a temperature Tl higher than room temperature and lower than the compensation temperature of the magnetic field auxiliary layer, -Hsc (Tl)> Hw (Tl) + Hz (Tl), and a magnetic field required to generate a new mark in the reproducing layer- Hnc (Th) is: -Hw (Th) <Hnc (Th) -Hz (Th) <Hw at a temperature Th higher than the compensation temperature of the magnetic field auxiliary layer and lower than the Curie temperature of the memory layer.
(Th), and the magnetic field required to enlarge the mark of the reproducing layer
Hexp (Th) satisfies the relationship of Hexp (Th) -Hz (Th) <Hw (Th) at a temperature Th higher than the compensation temperature of the magnetic field auxiliary layer and lower than the Curie temperature of the memory layer. recoding media. Here, Hw represents the magnitude of the magnetization given to the reproducing layer by the magnetization of the memory layer, and Hz represents the magnitude of the magnetization given to the reproducing layer by the magnetization of the magnetic field auxiliary layer. 10. A reproducing layer showing perpendicular magnetization on a substrate,
A memory layer exhibiting perpendicular magnetization, and a magnetic field auxiliary layer exhibiting perpendicular magnetization at least at room temperature, wherein between the reproducing layer and the memory layer, exchange coupling between the reproducing layer and the memory layer is interrupted. A magneto-optical recording medium having a first blocking layer and a second blocking layer between the memory layer and the magnetic field auxiliary layer for blocking exchange coupling between the memory layer and the magnetic field auxiliary layer; Light is emitted while modulating the intensity into binary values of high intensity and low intensity, detecting reflected light reflected by the magneto-optical recording medium, and demodulating the light to reproduce recorded information. A method for reproducing a magnetic recording medium. 11. The reproducing method for a magneto-optical recording medium according to claim 10, wherein the frequency at which the beam intensity is modulated into a high intensity and a low intensity is determined by the frequency of the information recorded on the magneto-optical recording medium. A reproduction method for a magneto-optical recording medium, wherein the reproduction frequency is at least twice the minimum recording frequency.