JP2000187897A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magneto-optical recording medium capable of individually reproducing high density recorded information with high resolving power. SOLUTION: The magneto-optical recording medium 100 has a dielectric layer 2, a reproduction layer 3, a reproduction assisting layer 4, a nonmagnetic layer 5, a recording layer 6 and a protective layer 7 in this order on a substrate 1. The reproduction assisting layer 4 comprises a perpendicularly magnetized film whose Curie temperature is lower than the maximum temperature in a region irradiated with reproduction light. In reproduction, the magnetization of the reproduction assisting layer 4 in a high temperature region in a spot of reproduction light vanishes and only the desired recording magnetic domain is transferred to the reproduction layer 3 by magnetostatic coupling. Since the reproduction assisting layer 4 having perpendicular magnetization is present on the reproduction layer 3, a boundary region between a mask region formed by exchange coupling with the reproduction assisting layer 4 and a region to which the recording magnetic domain is transferred in the reproduction layer 3 becomes very narrow, accordingly resolving power in reproduction is remarkably enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for reproducing information by transferring magnetization information of a recording layer to a reproducing layer, and more particularly, to reliably record information recorded at high density on the reproducing layer. The present invention relates to a magneto-optical recording medium that can be transferred and reproduced at high resolution with high resolution.

[0002]

2. Description of the Related Art Optical recording media such as magneto-optical recording media are known as external memories of computers and the like. Magneto-optical recording media can handle large volumes of data such as moving images and audio, and are therefore frequently used as recording media in the multimedia age. In such a magneto-optical recording medium, it is desired to further increase its storage capacity. As a method for realizing this, it is conceivable to record information at a high density by making the recording magnetic domain smaller. . It is possible to perform recording by miniaturizing the recording magnetic domain by using an optical magnetic field modulation method of applying a magnetic field having a polarity corresponding to a recording signal while irradiating pulsed light in synchronization with a recording clock. However, when trying to reproduce a minute recording magnetic domain, the spot diameter of the reproducing light cannot be reduced further due to the limit of the NA of the optical head, and a plurality of minute recording magnetic domains existing in the reproducing light spot are individually separated. Can not be played. That is, since the resolution of the reproduction light is insufficient, it is not possible to reproduce each minute recording magnetic domain. Therefore, it is necessary to reproduce a minute recording magnetic domain with a reproduction spot diameter of the current size.

As one method for solving this problem, for example, the Journal of Magnetic Society of Japan, V
ol.17 Supplement No.S1, pp.201 (1993) proposes a magnetic super-resolution (MSR) technique. With this technology, even if two recording magnetic domains exist in the reproduction light spot, it is possible to reproduce the other recording magnetic domain by masking one of the magnetic domains so as not to be visible and narrowing the effective field of view. I have to. If this technique is used, the reproduction resolution can be improved without reducing the actual reproduction light spot diameter.

In the MSR technique, FAD (Front Aperture Detachment) is performed according to the position of a reproduction area in a reproduction light spot.
Section: Front Aperture Detection, RAD (Rear Aperture)
Detection: Back Aperture Detection, CAD (Center Aper
ture detection). In the FAD system, as shown in FIG. 2, when the reproduction light is irradiated to the medium moving rightward, the elliptical region 22 behind the light spot LS is heated to a high temperature due to the heat conduction of the medium. The high temperature region 22 becomes a mask region. On the other hand, the front crescent-shaped area 21 in the light spot LS is a low-temperature area, and this low-temperature area 21 is a reproduction area. In a medium according to this method, an exchange-coupled three-layer film composed of a reproducing layer, a switch layer, and a recording layer is usually used as a magnetic layer. In the FAD system, the recording density in the tangential direction of the medium (hereinafter referred to as linear density) can be increased. However, due to the crescent-shaped reproduction area, the recording domain existing in the adjacent track can be reduced by decreasing the track pitch. A reproduction signal from the disc is detected, and it is difficult to improve the recording density in the track width direction (hereinafter, referred to as track density).

In the RAD system, as shown in FIG.
Contrary to the AD system, the rear high-temperature region 3 in the light spot LS
Reference numeral 2 denotes a reproduction region, and a crescent-shaped low-temperature region 31 in front of the reproduction region.
Is a mask area. Therefore, even if the track pitch is narrowed, the recording marks on the adjacent track are also masked, and the FAD
The track density can be improved as compared with the method. In principle, the layer structure of the magnetic layer of the medium according to the RAD system is sufficient to have two layers, the reproducing layer and the recording layer. However, since the RAD method requires an initialization magnetic field for initializing the reproduction layer in addition to the reproduction magnetic field, the recording layer and the reproduction layer must be configured in consideration of the influence of the reproduction magnetic field and the initialization magnetic field. Must. Therefore, actually, four magnetic layers (for example, a reproducing layer, a reproducing auxiliary layer, an intermediate layer, and a recording layer) are required for controlling the exchange coupling force between the reproducing layer and the recording layer.

[0006]

In the CAD system, as shown in FIG. 4, a high-temperature region 28 near the center of a light spot is used as a reproduction region, and a low-temperature region 29 around the high-temperature region 28 is used as a mask region. The CAD method does not require an initialization magnetic field unlike the RAD method, and masks both the front and rear of the light spot of the reproducing layer, so that the line density and the track density can be improved. The magnetic layer of the medium according to the CAD system is a two-layer exchange-coupled film of a reproducing layer and a recording layer. As the reproducing layer, an in-plane magnetic film which shows in-plane magnetization at room temperature and shows perpendicular magnetization at a predetermined temperature is used, and the in-plane magnetization of the reproducing layer is used as a mask region. However,
In this type of reproducing layer, there is a problem that a boundary region that changes vertically from the in-plane, that is, a region where in-plane magnetization and perpendicular magnetization coexist is relatively large, so that the reproducing resolution is not sufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a magneto-optical device capable of individually detecting high-density minute magnetic domains with high resolution. It is to provide a recording medium.

[0008]

According to a first aspect of the present invention, a magneto-optical recording medium includes a recording layer, a non-magnetic layer, and a reproducing layer in this order, and is irradiated with reproducing light to reproduce information. Comprises a reproduction auxiliary layer having perpendicular magnetization between the nonmagnetic layer and the reproduction layer and in contact with the reproduction layer, wherein the Curie temperature of the reproduction auxiliary layer is higher than the highest temperature in the region irradiated with the reproduction light. A magneto-optical recording medium characterized in that the recording medium is also low.

As shown in FIG. 1, the magneto-optical recording medium according to the first embodiment of the present invention has a structure including a recording layer, a non-magnetic layer, a reproduction auxiliary layer, and a reproduction layer in this order. The reproduction auxiliary layer is a perpendicular magnetization film, and is configured so that its Curie temperature is lower than the maximum temperature of the medium when the reproduction light is irradiated, that is, lower than the reproduction temperature. Preferably the Curie temperature is 15
The temperature is set to be around 0 ° C. Thus, when the medium is heated by the irradiation of the reproduction light, the magnetization of the reproduction auxiliary layer near the center of the reproduction light spot disappears. At this time, it is preferable to configure the magnetic material of the auxiliary reproduction layer such that the region of the auxiliary reproduction layer where the Curie temperature is higher than or equal to the size of the recording magnetic domain of the recording layer. As a material constituting the reproduction auxiliary layer, for example, TbFe, TbFeCo, GdFe, G
dFeCo, TbCo, DyFeCo, DyFe, Dy
A rare earth-transition metal alloy such as Co, or an alloy obtained by adding an additive such as Cr or Zr to these alloys can be used.

The principle of reproduction of a magneto-optical recording medium having such a structure will be described below with reference to FIG. FIG.
In this case, it is assumed that minute recording magnetic domains are previously formed on the recording layer 6 by a magnetic field modulation recording method or a light modulation recording method. Before reproduction, the magnetization of the reproduction layer 3 is
Are aligned in the same direction as the magnetization of the auxiliary reproduction layer 4 by the exchange coupling force (initialized state). When the medium is irradiated with the reproduction light 41 at a predetermined light intensity, the vicinity of the center of the reproduction light spot LS is heated to a high temperature. The reproduction auxiliary layer 4 has a Curie temperature of the maximum temperature Tma of the medium when the reproduction light 41 is irradiated.
Since it is adjusted to be lower than x, as shown in FIG. 5, the magnetization of the magnetic domain 42 of the reproduction auxiliary layer 4 near the center of the reproduction light spot LS disappears. Then, the reproducing layer 3 located immediately above the magnetic domain 42 where the magnetization of the reproducing auxiliary layer has disappeared.
In the magnetic domain 43, the exchange coupling force with the magnetic domain 42 of the auxiliary reproduction layer 4 is lost, and the recording magnetic domain 44 of the recording layer is transferred to the reproducing layer 3 by magnetostatic coupling through the region where the magnetization of the auxiliary reproduction layer 4 has disappeared. . On the other hand, in the region other than the vicinity of the center of the light spot LS, that is, the magnetic domain 4 of the reproducing layer in the low temperature region 46.
7 remains oriented in the direction of magnetization of the magnetic domains 48 of the auxiliary reproduction layer by exchange coupling with the magnetic domains 48 of the auxiliary reproduction layer, and thus the low-temperature area 46 functions as a mask area. Therefore, the recording magnetic domains 44 and 4 existing in the reproduction light spot LS
Of the recording layers 9a and 49b, the recording magnetic domains 49a and 49b are masked by the reproducing layer 3, and only the recording magnetic domains 44 can be individually extracted and reproduced in the reproducing layer 3.

The magneto-optical recording medium of the present invention has the following advantages as compared with a conventional magneto-optical recording medium using an in-plane magnetized film as a reproducing layer. FIG. 6 conceptually shows the temperature change of the Kerr rotation angle from the material constituting the reproducing layer. In the conventional magneto-optical recording medium, the reproducing layer is formed of an in-plane magnetic film. There is a region where the magnetization gradually transitions perpendicularly from the plane, and the Kerr rotation angle changes gently. This was also the cause of the low reproduction resolution described in the section of the prior art. On the other hand, in the magneto-optical recording medium of the present invention, since the reproduction auxiliary layer having perpendicular magnetization is attached to the reproduction layer, as shown in FIG.
The magnetizations 47 and 47 ′ belonging to the low-temperature region are aligned with the directions (initialization directions) of the magnetizations 48 and 48 ′ of the auxiliary reproduction layer 4 by exchange coupling with the magnetic domains 48 and 48 ′ of the auxiliary auxiliary layer 4 immediately below. I have. Therefore, the magnetization directions of the magnetic domain 43 of the reproducing layer 3 and the magnetic domains 47 and 47 ′ on both sides thereof are exactly opposite, and the boundary region between the region where the recording magnetic domain is transferred and the mask region in the reproducing layer 3 becomes narrow. In other words, as shown in FIG. 6, the Kerr rotation angle detected from the reproduction layer 3 is equal to the boundary between the high temperature region 45 and the low temperature region 46 in the reproduction layer 3, that is, the Curie temperature Tc of the reproduction auxiliary layer 4. As a result. Therefore, the reproduction resolution is higher than before.

In the present invention, since the direction of magnetization of the auxiliary reproduction layer must be kept in one direction (the direction of initialization), the reproducing magnetic field in the medium has the same direction as the direction of magnetization of the auxiliary reproduction layer. Is preferably applied. Thus, the magnetization direction of the auxiliary reproduction layer can be always oriented in the initialization direction during the cooling process after the magnetization is lost by heating to the Curie temperature or higher by the reproduction light irradiation.

In the magneto-optical recording medium of the present invention, the reproducing layer can be constituted by using a perpendicular magnetization film, and the compensation temperature of the reproducing layer is preferably 100 ° C. or less. As a result, the saturation magnetization of the reproducing layer is increased, so that the magnetostatic coupling with the recording layer is favorably performed, and the magnetization of the recording layer is transferred. As a material constituting such a perpendicular magnetization film, for example, GdFeC
o, GdFe, GdTbFeCo, GdDyFeCo,
A rare earth-transition metal alloy such as GdDyTbFeCo, an alternate stack of a Pt layer and a Co layer, or a PtCo alloy can be used.

Further, the reproducing layer of the magneto-optical recording medium of the present invention can be constituted by using a magnetic material which exhibits in-plane magnetization from room temperature to a critical temperature and exhibits perpendicular magnetization at the critical temperature or higher. . Here, the critical temperature means the temperature at which the magnetization changes from the in-plane direction to the vertical direction. In the present invention, it is preferable that this critical temperature is lower than the Curie temperature of the reproduction auxiliary layer, and shows perpendicular magnetization in a heated region in the reproduction light spot during reproduction, and in-plane magnetization in a region outside the reproduction light spot. It is even more preferred to make it as shown. A material suitable for such a reproducing layer is, for example, an alloy in which the magnetic moment of Gd is superior to the magnetic moments of Fe and Co.

The non-magnetic layer of the magneto-optical recording medium of the present invention is a layer provided for cutting the exchange coupling between the recording layer and the auxiliary reproduction layer. Body or Al, AlTi, Au, Cu, A
It can be configured using a non-magnetic metal such as g, or a semiconductor such as Si or Ge.

According to a second aspect of the present invention, in a magneto-optical recording medium provided with a recording layer, a non-magnetic layer, and a reproducing layer in this order, and reproducing light to reproduce information, the reproducing layer is A perpendicular magnetic film, comprising a leakage magnetic field control layer between the nonmagnetic layer and the recording layer and in contact with the recording layer, wherein the leakage magnetic field control layer exhibits in-plane magnetization at room temperature, and its Curie temperature is: A magneto-optical recording medium is provided which is in the range of 100 ° C. or higher and Curie temperature of the recording layer or lower.

As shown in FIG. 8, the magneto-optical recording medium according to the second embodiment of the present invention has a structure including a recording layer, a leakage magnetic field control layer, a non-magnetic layer, and a reproducing layer in this order. The reproducing layer is formed using a perpendicular magnetization film, the leakage magnetic field control layer shows in-plane magnetization at room temperature, and its Curie temperature is set to 100 ° C. or higher and equal to or lower than the Curie temperature of the recording layer. Preferably, the area of the stray magnetic field control layer where the temperature is equal to or higher than the Curie temperature when the reproducing light is irradiated is set to be substantially equal to the size of the recording magnetic domain of the recording layer. The leakage magnetic field control layer is a layer for controlling a leakage magnetic field from a recording magnetic domain of the recording layer, and can apply only a leakage magnetic field of a desired recording magnetic domain of the recording layer to the reproducing layer. Such a leakage magnetic field control layer includes, for example, GdFe, GdCo, TbFe, DyFe
Alternatively, it can be configured using GdTbFeCoCr.

The principle of reproduction of the magneto-optical recording medium according to the second aspect of the present invention will be described below with reference to FIG. In FIG. 9, it is assumed that minute recording magnetic domains are formed in the recording layer 6 in advance by a magnetic field modulation recording method or a light modulation recording method. Before reproduction, the magnetization of the reproduction layer 3 is aligned in one direction by an initialization magnetic field (not shown) (initialized state). The Curie temperature of the leakage magnetic field control layer is 100 ° C. to Tc when the Curie temperature of the recording layer is Tc1.
It is adjusted to be within the range of 1. When the medium is irradiated with the reproduction light 91 at a predetermined light intensity, as shown in FIG. 9, the leakage magnetic field control layer 9 near the center of the reproduction light spot LS is formed.
Is heated above the Curie temperature Tcr, and the magnetization of the magnetic domains 92 of the leakage magnetic field control layer 9 disappears. The magnetic domain 93 of the reproducing layer 3 located immediately above the magnetic domain 92 where the magnetization of the leakage magnetic field control layer 9 has disappeared is separated from the recording magnetic domain 94 of the recording layer 6 through the area where the magnetization of the leakage magnetic field control layer 9 has disappeared. Upon receiving the leakage magnetic field, the magnetization is oriented in the same direction as the magnetization of the recording magnetic domain 94 by the magnetostatic coupling. That is, the recording magnetic domains 94 of the recording layer 6 are transferred to the reproducing layer 3. On the other hand, regions other than the vicinity of the center of the light spot LS, that is, the magnetic domains 97 of the reproducing layer in the low-temperature region 46 are not affected by the leakage magnetic field from the recording layer due to the in-plane magnetization of the leakage magnetic field control layer, and thus face the initialization direction. The low temperature region 96 functions as a mask region. Therefore, among the recording magnetic domains 94, 99a, and 99b existing in the reproduction light spot LS, the recording magnetic domains 99a and 99b are in-plane magnetizations 98 and 9 of the leakage magnetic field control layer 9.
Since it is masked by 8 ', only the recording magnetic domains 94 can be extracted to the reproducing layer 3 and transferred to reproduce. The above is the description of the principle of reproduction of the magneto-optical recording medium according to the second aspect of the present invention.

Further, in the magneto-optical recording medium according to the second aspect of the present invention, since the reproducing layer is constituted by using a perpendicular magnetization film, the magnetic domain 93 of the reproducing layer 3 and the magnetic domains 97 and 97 'on both sides thereof are provided.
Are opposite to each other, and the boundary region between the region where the recording magnetic domain is transferred and the mask region in the reproducing layer 3 is narrowed. In other words, the Kerr rotation angle detected from the reproduction layer is
The steep change occurs at the boundary between the high-temperature region 95 and the low-temperature region 96 in the reproducing layer 3, that is, the Curie temperature of the stray magnetic field control layer 9. Therefore, the reproduction resolution is higher than before.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the magneto-optical recording medium according to the present invention will be specifically described below.

Embodiment 1 FIG. 1 shows a cross-sectional structure of a specific example of a magneto-optical recording medium according to a first embodiment of the present invention. The magneto-optical recording medium 100 has a structure in which a dielectric layer 2, a reproducing layer 3, a reproducing auxiliary layer 4, a non-magnetic layer 5, a recording layer 6, and a protective layer 7 are sequentially laminated on a transparent substrate 1.

In the structure shown in FIG. 1, the transparent substrate 1 may be formed by molding a transparent resin material such as polycarbonate or amorphous polyolefin into a desired shape, or may be provided on one side of a glass plate formed into a desired shape. Any substrate having optical transparency, such as a substrate in which a transparent resin film to which the preformat pattern has been transferred can be used. The dielectric layer 2 is provided for causing a reproduction light beam to cause multiple interference in the film to substantially increase the detected Kerr rotation angle, and is made of a material having a higher refractive index than the transparent substrate 1. For example, it can be formed using an inorganic dielectric made of SiN. The protective layer 7 is made of the transparent substrate 1
It protects the film bodies 3 to 6 laminated between the metal layer and the protective layer 7 from chemical adverse effects such as corrosion, and is made of, for example, a SiN film or a carbon film. The recording layer 6 is a perpendicular magnetization film exhibiting perpendicular magnetic anisotropy at a temperature equal to or higher than room temperature. For example, TbFeCo, DyFeCo, TbDyFeCo
An amorphous alloy of a rare earth and a transition metal, such as, for example, is most preferable. However, other known magneto-optical recording materials such as an alternately laminated body of a Pt film and a Co film or a garnet-based oxide magnetic material can also be used. The non-magnetic layer 5 is a layer for cutting the exchange coupling force between the recording layer 6 and the auxiliary reproduction layer 4, for example, Si
Dielectric such as O ₂ , AlN, SiN, Al, AlT
Metals such as i, Au, Cu, AuAl, and AgAl, or a laminate of these metals and a dielectric can be used.

The reproducing layer 3 is a perpendicular magnetization film which exhibits perpendicular magnetization at room temperature or higher.
It can be configured using a magnetic material such as GdFeCo that increases the Kerr rotation angle at the maximum temperature of the medium when the reproduction light is irradiated. The reproduction assistance layer 4 is, for example,
TbFe, a perpendicular magnetization film with a Curie temperature of about 150 ° C
Can be used.

The above-mentioned dielectric layer 2, reproducing layer 3, reproducing auxiliary layer 4, nonmagnetic layer 5, recording layer 6, and protective layer 7 can be formed by a dry process such as continuous sputtering using a magnetron sputtering apparatus. it can. The thicknesses of the reproducing layer 3, the auxiliary reproducing layer 4, and the nonmagnetic layer 5 are, for example, as follows.
5 nm to 100 nm, 5 nm to 30 nm, 1
nm to about 30 nm.

Next, a method for reproducing the magneto-optical recording medium 100 having such a structure will be described in detail with reference to the drawings.

First, the magneto-optical recording medium 100 shown in FIG.
Is loaded into a reproducing apparatus (not shown) such that reproducing light is incident from the substrate 1 side. Recording layer 6 of magneto-optical recording medium 100
It is assumed that minute recording magnetic domains are formed in advance by an optical magnetic field modulation recording method in which a recording magnetic field having a polarity corresponding to a recording signal is applied while irradiating a recording light pulsed in synchronization with a recording clock. . The magnetization of the reproduction auxiliary layer 4 is
It is assumed that all of the magnetizations are aligned in the initialization direction by an initialization magnetic field Hr described later, and the magnetization of the reproduction layer 3 is also initialized by exchange coupling with the auxiliary reproduction layer 4.

In order to reproduce the minute recording magnetic domains recorded in the recording layer 6, the magneto-optical recording medium 100 is irradiated with reproducing light 41 having a low laser power while rotating the magneto-optical recording medium 100 at a predetermined linear velocity. Heat. FIG. 5 shows a state in which a predetermined area of the magneto-optical recording medium 100 is irradiated with the reproduction light 41. By irradiating the magneto-optical recording medium 100 with the reproducing light 41, the surface of the magneto-optical recording medium 100 is heated with a temperature distribution as shown in the graph of FIG. The Curie temperature Tc of the reproduction auxiliary layer 4 is the maximum temperature Tmax of this temperature distribution.
, The auxiliary reproduction layer 4 located near the center 45 of the reproduction light spot LS is heated to the Curie temperature Tc or higher. The size of the reproduction auxiliary layer heated above the Curie temperature Tc is about the size of the recording magnetic domain of the recording layer,
The magnetization of the magnetic domain 42 in that portion disappears. At this time, the magnetic domain 43 of the reproducing layer located immediately above the magnetic domain 42 of the reproducing auxiliary layer 4 in which the magnetization has disappeared has its exchange coupling force with the reproducing auxiliary layer 4 cut off, and the magnetostatic from the recording magnetic domain 44 of the recording layer 6 has Receiving the coupling force, the recording magnetic domain 44 faces in the same direction. That is, the recording magnetic domain 44 of the recording layer is transferred to the reproducing layer by magnetostatic coupling.

On the other hand, the magnetic domain 47 of the reproduction auxiliary layer in a region (low temperature region) other than near the center of the reproduction light spot LS has a Curie temperature or lower, and thus is initialized (downward in FIG. 5).
And the magnetic domain 48 of the reproducing layer 3 in such a region.
Are exchange-coupled with the magnetic domains 47 of the auxiliary reproduction layer, and are in a state of being directed in the initialization direction. Therefore, even if other recording magnetic domains 49a and 49b are present in the reproducing light spot, these recording magnetic domains 49a and 49b are masked by the magnetizations 48 and 48 'of the reproducing layer oriented in the initialization direction, so that reading is not performed. It will not be. In addition, since the boundary region between the magnetization 43 of the reproduction layer where the recording magnetic domain is transferred and the magnetizations 47 and 47 'of the mask region is extremely narrow, the reproduction layer is not affected by the temperature change (temperature distribution) in the reproduction light spot. The change in rotation angle is
It becomes steep as shown in FIG. Therefore, it becomes possible to detect the minute recording magnetic domains individually and with high resolution.

Next, when the recording magnetic domain 44 of the recording layer is read and the reproduction light spot LS passes, the temperature of the magnetic domain 42 in which the magnetization of the reproduction auxiliary layer has disappeared decreases and the magnetization reappears. At this time, the magnetization of the magnetic domains 42 of the reproduction auxiliary layer is aligned in the initialization direction by the initialization magnetic field Hr from a magnetic field application device (not shown) provided separately, and
The magnetization of No. 3 is initialized in the initializing direction by exchange coupling with the magnetic domain 42 of the auxiliary reproduction layer.

Embodiment 2 FIG. 8 shows a cross-sectional structure of a specific example of a magneto-optical recording medium according to a second embodiment of the present invention. The magneto-optical recording medium 200 has a structure in which a dielectric layer 2, a reproducing layer 3, a nonmagnetic layer 5, a stray magnetic field control layer 9, a recording layer 6, and a protective layer 7 are sequentially laminated on a transparent substrate 1. The leakage magnetic field control layer 9 includes, for example, GdFe,
GdCo, TbFe, DyFe or GdTbFeCo
The layers other than the leakage magnetic field control layer 9 and the transparent substrate can be formed using the same material as in the first embodiment. Further, each layer laminated on the transparent substrate can be formed by a dry process such as continuous sputtering by a magnetron sputtering apparatus in the same manner as in the first embodiment. The magneto-optical recording medium 200 can reproduce information at a high resolution according to the reproducing principle of the magneto-optical recording medium according to the above-described second embodiment.

Although the embodiment of the magneto-optical recording medium according to the present invention has been described above, the present invention is not limited to the above embodiment. For example, MAMMOS (Magnetic Amplifying Magneto-Optical) devised by the present inventors.
By making the reproducing layer function as a magnetic domain expansion reproducing layer based on the principle of (System), the minute recording magnetic domain of the recording layer can be transferred to the magnetic domain expanding reproducing layer and enlarged while applying a reproducing magnetic field. In the MAMMOS, an alternating reproducing magnetic field is applied to confirm the presence or absence of a recording magnetic domain. Therefore, it is desirable that the magnetization of the reproducing layer is not reversed in a region other than the reproducing region (low temperature region) by the reproducing magnetic field.
For that purpose, it is necessary to increase the perpendicular anisotropy energy Ku of the reproducing layer. Here, the perpendicular magnetic anisotropy energy Ku can be represented by the product of the coercive force Hc and the saturation magnetization Ms. FIG. 7 shows the temperature change of the MsHc product of the composite film composed of the reproduction layer and the reproduction auxiliary layer of the magneto-optical recording medium of the present invention. (Perpendicular magnetic anisotropy energy) is effectively increased. This is because in a temperature range equal to or lower than the Curie temperature Tc of the auxiliary reproduction layer, the magnetization of the auxiliary reproduction layer is exchange-coupled with the magnetization of the auxiliary reproduction layer and is affected by the coercive force of the auxiliary reproduction layer. Therefore, by adding a reproduction auxiliary layer to the reproduction layer for MAMMOS, it is possible to effectively prevent the magnetic domains other than the reproduction region of the reproduction layer from being inverted by the reproduction magnetic field. The principle of MAMMOS is described in detail in International Publication No. WO98 / 02878, which can be referred to.

[0032]

In the magneto-optical recording medium according to the first aspect of the present invention, a reproducing auxiliary layer is added to the reproducing layer, and the mask area of the reproducing layer is controlled by utilizing the exchange coupling force with the magnetization of the reproducing auxiliary layer. Therefore, minute recording magnetic domains can be individually and reliably transferred to the reproducing layer. Further, the boundary between the mask region of the reproducing layer and the region where the magnetic domain is transferred is extremely narrow, so that the reproducing resolution is significantly improved. Further, since the reproduction signal can be amplified by making the reproduction layer function as a magnetic domain expansion reproduction layer, the C / N of the reproduction signal can be improved.

In the magneto-optical recording medium according to the second aspect of the present invention, the sensitivity of the recording magnetic field is increased by the leakage magnetic field control layer added to the recording layer, so that information can be recorded with a small recording magnetic field. Become. Further, the leakage magnetic field from the recording magnetic domain of the recording layer can be individually and reliably applied to the reproducing layer by the leakage magnetic field control layer. So MSR and MA
It is extremely suitable as a magneto-optical recording medium for MMOS.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a cross-sectional structure of a specific example of a magneto-optical recording medium according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the FAD method of the MSR technique, and shows a state in which a region in front of a reproduction light spot is masked.

FIG. 3 is a diagram for explaining the RAD method of the MSR technique, and shows a state where a rear area of a reproduction light spot is masked.

FIG. 4 is a diagram for explaining a CAD system of the MSR technique, and shows a state where a central region of a reproduction light spot is masked.

FIG. 5 is a diagram for explaining the principle of reproduction of the magneto-optical recording medium according to the first embodiment of the present invention, and shows how recording magnetic domains are transferred to a reproduction layer by irradiating reproduction light.

FIG. 6 is a diagram showing the temperature dependence of the Kerr rotation angle of the material forming the reproducing layer.

FIG. 7 is a diagram illustrating a temperature change of a value of a product of a saturation magnetization Ms and a coercive force Hc of a composite film including a reproduction layer and a reproduction auxiliary layer.

FIG. 8 is a diagram schematically showing a cross-sectional structure of a specific example of a magneto-optical recording medium according to a second embodiment of the present invention.

FIG. 9 is a diagram for explaining the principle of reproduction of the magneto-optical recording medium according to the second embodiment of the present invention, and shows how recording magnetic domains are transferred to a reproduction layer by irradiating reproduction light.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2 Dielectric layer 3 Reproducing layer 4 Reproducing auxiliary layer 5 Nonmagnetic layer 6 Recording layer 7 Protective layer 9 Leakage magnetic field control layer 41, 91 Reproducing light 44, 49a, 49b, 94, 99a, 99b Recording magnetic domain 100, 200 light Magnetic recording media

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Manabu Tani 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell Co., Ltd. 5D075 CF03 EE03 FF04 FF13

Claims (8)

[Claims] 1. A magneto-optical recording medium comprising a recording layer, a non-magnetic layer, and a reproducing layer in this order, wherein information is reproduced by irradiating a reproducing light. A magneto-optical recording medium comprising: a read auxiliary layer having perpendicular magnetization in contact with the layer, wherein the Curie temperature of the auxiliary read layer is lower than the maximum temperature in a region irradiated with the read light. 2. The magneto-optical recording medium according to claim 1, wherein the reproducing layer is a perpendicular magnetization film. 3. The magneto-optical recording medium according to claim 1, wherein the reproducing layer exhibits in-plane magnetization from room temperature to a critical temperature, and exhibits perpendicular magnetization at or above the critical temperature. 4. The information reproducing apparatus according to claim 1, wherein a magnetic field for initializing the reproduction auxiliary layer is applied during information reproduction.
7. The magneto-optical recording medium according to claim 1. 5. The magneto-optical recording medium according to claim 1, wherein a compensation temperature of the reproducing layer is 100 ° C. or less. 6. The reproducing layer according to claim 1, wherein the reproducing layer is a magnetic domain enlarged reproducing layer capable of reproducing a magnetic domain transferred from the recording layer by applying a reproducing magnetic field in the same direction as the magnetic domain. 2. The magneto-optical recording medium according to claim 1, wherein: 7. A magneto-optical recording medium comprising a recording layer, a non-magnetic layer, and a reproducing layer in this order, wherein information is reproduced by irradiating reproducing light, wherein the reproducing layer comprises a perpendicular magnetization film, A leakage magnetic field control layer for controlling a leakage magnetic field from the layer, between the nonmagnetic layer and the recording layer and in contact with the recording layer, the leakage magnetic field control layer exhibits in-plane magnetization at room temperature, and its Curie temperature A magneto-optical recording medium having a temperature in the range of 100 ° C. or higher and the Curie temperature of the recording layer or lower. 8. The method according to claim 1, wherein the leakage magnetic field control layer comprises GdFe, Gd
The magneto-optical recording medium according to claim 7, wherein the magneto-optical recording medium is one selected from the group consisting of Co, TbFe, DyFe, and GdTbFeCoCr.