JP2001229585A - Magneto-optical recording medium, and magneto-optical disk device for reproduction of the same or method for reproduction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium in which magnetic domains in a recording layer can be transferred to a reproducing layer with high resolution and each domain in the recording layer can be accurately detected, and to provide a magneto-optical disk device or a method for reproduction to reproduce the signal from the magneto-optical recording medium. SOLUTION: The magneto-optical recording medium 10 has a first reproducing layer 3, a second reproducing layer 4, an intermediate layer 5, and a recording layer 6. The intermediate layer 5 has the Curie temperature Tc higher than room temperature. The second reproducing layer 4 is an in-plane magnetization film at room temperature and becomes a perpendicular magnetization film at T1 which is lower than Tc or higher. The first reproducing layer 3 is an in-plane magnetization film at room temperature and becomes a perpendicular magnetization film at T2 which is lower than T1 or higher. When a DC magnetic field Hex is externally applied, a magnetic domain 60 in the recording layer 6 present in the temperature range from T2 to T1 is transferred and enlarged through the intermediate layer 5 and the second reproducing layer 4 to the first reproducing layer 3 as a magnetic domain 30 which is detected with a laser beam LB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording a signal by forming a magnetic domain, and a magneto-optical disk apparatus or a reproducing method for reproducing a signal from the magneto-optical recording medium.

[0002]

2. Description of the Related Art Magneto-optical recording media have attracted attention as rewritable, large-capacity, and highly reliable recording media, and have begun to be put to practical use as computer memories and the like. Recently, the recording capacity is 6.0 Gby.
tes's magneto-optical recording medium is AS-MO (Advanced)
d Storage Magneto Optica
l disk) standard and is about to be put to practical use.

[0003] Further, a 14 Gbyte by magnetic domain expansion reproduction method for reproducing signals by enlarging and transferring magnetic domains of a recording layer to a reproduction layer.
A magneto-optical recording medium having a recording capacity of es has also been proposed. In recording a signal on a magneto-optical recording medium by the magnetic domain expansion reproduction method, the shortest domain length is reduced to about 0.1 μm. When reproducing signals from such a magneto-optical recording medium, recording is performed by irradiating a minute spot on the magneto-optical recording medium by condensing a laser beam having a wavelength of 650 nm with an objective lens having a numerical aperture of 0.6. The magnetic domains of the layer are transferred to the reproducing layer, and the transferred magnetic domains are detected by a laser beam.

[0004]

However, as the recording density further increases in the future, the magnetic domains formed in the recording layer will become smaller. As a result, it is expected that a plurality of magnetic domains are present in the spot of the laser beam irradiated on the magneto-optical recording medium, and there is a problem that the magnetic domains cannot be detected accurately.

Therefore, the present invention solves such a problem, and a magneto-optical recording medium capable of transferring magnetic domains of a recording layer to a reproducing layer with high resolution and accurately detecting each magnetic domain of the recording layer, and the magneto-optical recording medium. It is an object of the present invention to provide a magneto-optical disk apparatus or a reproducing method for reproducing a signal from a disc.

[0006]

According to the first aspect of the present invention, there is provided a first magnetic layer for recording a signal, and a Curie temperature Tc which is formed in contact with the first magnetic layer and is higher than room temperature.
A second magnetic layer having: and a second magnetic layer formed in contact with the second magnetic layer;
First transition temperature T1 at which in-plane magnetic film changes to perpendicular magnetic film
A third magnetic layer having: and a third magnetic layer formed in contact with the third magnetic layer;
The second transition temperature T2 at which the in-plane magnetic film changes to a perpendicular magnetic film
And a fourth magnetic layer having the following formula, and satisfying the relationship of Tc>T1> T2.

In the magneto-optical recording medium according to the first aspect, when the laser beam is irradiated and the temperature rises, the first
In the region of the second magnetic layer in contact with the magnetic layer, the magnetization disappears in the region of the temperature Tc or higher, and in the region of the third magnetic layer at the temperature T1 or lower, the in-plane magnetized film is held. In the above region, the film changes to a perpendicular magnetization film. In the region of the fourth magnetic layer below the temperature T2, the in-plane magnetic film is retained, and in the region above the temperature T2, the film changes to a perpendicular magnetic film. Then, the magnetic domains existing in the region of the temperature Tc or higher in the first magnetic layer are prevented from being transferred to the second magnetic layer by exchange coupling, and the magnetic domains existing in the region of the first magnetic layer lower than the temperature T1 are exchanged. The transfer prevents transfer to the third magnetic layer. As a result, of the first magnetic layer, from the temperature Tc to the temperature Tc
Only the magnetic domains existing up to 1 are transferred to the second, third and fourth magnetic layers by exchange coupling. Temperature T2 at which the fourth magnetic layer changes from an in-plane magnetization film to a perpendicular magnetization film
Is lower than the temperature T1 at which the third magnetic layer changes from an in-plane magnetic film to a perpendicular magnetic film, so that the area of the fourth magnetic layer where the magnetic domains of the first magnetic layer are transferred is larger than the area of the third magnetic layer. .

Therefore, according to the first aspect of the present invention, only magnetic domains existing between the temperature T2 and the temperature T1 can be transferred from the first magnetic layer to the fourth magnetic layer by exchange coupling. As a result, the magnetic domain can be extracted from the first magnetic layer with high resolution by making the distribution of the temperature T2 and the temperature T1 steep. Further, the magnetic domains of the first magnetic layer are formed in the fourth magnetic field without using an external magnetic field.
Enlarged transfer to the magnetic layer is possible.

According to a second aspect of the present invention, there is provided a magneto-optical recording medium according to the first aspect, wherein
The magnetic layer is a magneto-optical recording medium made of GdFe or TbFe. According to a third aspect of the present invention, in the magneto-optical recording medium according to the first aspect, preferably, the second type is provided.
The magnetic layer is made of Al, Au, Cr, Cu, Si, T
This is a magneto-optical recording medium made of a material to which one of a and Ti is added.

According to a fourth aspect of the present invention, there is provided a magneto-optical recording medium according to the first aspect, wherein
The magnetic layer is made of TdFe with Al, Au, Cr, Cu, Si, T
This is a magneto-optical recording medium made of a material to which one of a and Ti is added. In the magneto-optical recording medium according to any one of claims 2 to 4, since the second magnetic layer is made of a magnetic material based on GdFe or TbFe, the Curie temperature Tc is 180 to 21.
The magnetic domain can be extracted from the first magnetic layer with high resolution by using a laser beam having a temperature of 0 ° C. and a relatively low power of 2.0 to 2.5 mW.

According to a fifth aspect of the present invention, in the magneto-optical recording medium according to any one of the first to fourth aspects, the third magnetic layer is formed of Gd _1-x (FeCo) _x ( x:
0.30 to 0.33), and the fourth magnetic layer has Gd
_This is a magneto-optical recording medium comprising _1-x (FeCo) _x (x: 0.28 to 0.31).

In the magneto-optical recording medium according to the fifth aspect, the third magnetic layer changes from an in-plane magnetic film to a perpendicular magnetic film at a temperature of 150 ° C., and the fourth magnetic layer changes at a temperature of 120 ° C. The film changes from a film to a perpendicular magnetization film. Therefore, according to the invention described in claim 5, magnetic domains can be enlarged and transferred from the first magnetic layer to the fourth magnetic layer using only the laser beam.

According to a sixth aspect of the present invention, there is provided a magneto-optical disk drive for reproducing a signal from the magneto-optical recording medium according to any one of the first to fifth aspects, wherein The magneto-optical disk device includes an optical head that irradiates a laser beam from the fourth magnetic layer side and detects the reflected light, and a magnetic head that applies a DC magnetic field to the magneto-optical recording medium.

In the magneto-optical disk device according to the present invention, the magnetization in the region of the third magnetic layer and the fourth magnetic layer of the magneto-optical recording medium which is higher than the temperature Tc is changed by the DC magnetic field applied from the magnetic head. Turn in the direction. As a result, transfer of magnetic domains by magnetostatic coupling from the first magnetic layer to the third magnetic layer and the fourth magnetic layer in the region above the temperature Tc in the magneto-optical recording medium is prevented, and the temperature from the temperature Tc to the temperature T1 is reduced. The intermediate magnetic domain is enlarged and transferred to the fourth magnetic layer by exchange coupling with high resolution.

Therefore, according to the present invention, a signal can be reproduced from a magneto-optical recording medium with high resolution only by applying a DC magnetic field. Further, the magnetic head can reproduce a signal by magnetic domain expansion without applying an alternating magnetic field other than the DC magnetic field. Further, the invention according to claim 7 is based on claim 1.
A reproducing method for reproducing a signal from the magneto-optical recording medium according to any one of claims 1 to 5, wherein a DC magnetic field is applied to the magneto-optical recording medium, and the fourth magnetic layer side is applied to a region where the DC magnetic field is applied. This is a reproducing method for reproducing a signal from a magneto-optical recording medium by irradiating a laser beam from the optical disk and detecting reflected light of the laser beam from the region.

In the reproducing method according to the present invention, the magnetization in the region of the third magnetic layer and the fourth magnetic layer of the magneto-optical recording medium which is higher than the temperature Tc is changed in the direction of the DC magnetic field applied from the magnetic head. Turn. As a result, in the magneto-optical recording medium, the transfer of the magnetic domain from the first magnetic layer to the third magnetic layer and the fourth magnetic layer in the region above the temperature Tc by the magnetostatic coupling is prevented, and the temperature from the temperature T2 to the temperature T1 is reduced. The intermediate magnetic domain is enlarged and transferred to the fourth magnetic layer by exchange coupling with high resolution.

Therefore, according to the present invention, a signal can be reproduced by expanding the magnetic domain by applying only a DC magnetic field to the magneto-optical recording medium.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. Referring to FIG. 1, a magneto-optical recording medium 10 according to the present invention includes a light-transmitting substrate 1, an underlayer 2, a first reproducing layer 3, a second reproducing layer 4, an intermediate layer 5, and a recording medium. Layer 6;
And a protective layer 7. The translucent substrate 1 is made of glass, polycarbonate resin or the like, the underlayer 2 is made of SiN, and the first reproduction layer 3 and the second reproduction layer 4 are rare earth-rich Gd.
The intermediate layer 5 is made of GdFe, the recording layer 6 is made of TbFeCo, and the protective layer 7 is made of SiN. SiN constituting the underlayer 2, GdFeCo constituting the first reproducing layer 3 and the second reproducing layer 4, and G constituting the intermediate layer 5
dFe, TbFeCo constituting the recording layer 6, and SiN constituting the protective layer 7 are formed by a magnetron sputtering method.

The thickness of the underlayer 2 is 40 to 80 nm.
The thickness of the first reproducing layer 3 is 50 to 200 nm, the thickness of the second reproducing layer 4 is 50 to 200 nm,
The thickness of the intermediate layer 5 is 3 to 50 nm, the thickness of the recording layer 6 is 30 to 100 nm, and the thickness of the protective layer 7 is 4 nm.
0 to 80 nm. With reference to FIG. 2, a mechanism for reproducing a signal from the magneto-optical recording medium 10 will be described. Recording layer 6
Has a magnetic domain having a different magnetization direction as a result of recording a signal. The intermediate layer 5 is a perpendicular magnetization film at room temperature.
It has a Curie temperature Tc of 80-210 ° C. And
Since it is in contact with the recording layer 6, there exists a magnetic domain having the same magnetization as that of the recording layer 6 at room temperature. The second reproducing layer 4 is an in-plane magnetized film at room temperature and has a temperature T1 (= 140 to 190 ° C.).
Thus, the film changes to a perpendicular magnetization film. Also, the first reproducing layer 3
It is an in-plane magnetized film at room temperature and has a temperature T2 (= 100 to 150).
℃) or more, it changes to a perpendicular magnetization film. The Curie temperature Tc of the intermediate layer 5, the temperature T1 at which the second reproducing layer 4 changes from an in-plane magnetic film to a perpendicular magnetic film, and the temperature T2 at which the first reproducing layer 3 changes from an in-plane magnetic film to a perpendicular magnetic film. In between, Tc>
There is a relationship T1> T2. Therefore, the intermediate layer 5, the second reproducing layer 4, and the third magnetic layer 3 are formed so as to satisfy this relational expression.

When the magneto-optical recording medium 10 is irradiated with laser light LB from the first reproducing layer 3 side, the optical axis LB of the laser light LB
The temperature distribution becomes steep on the front side with respect to the traveling direction DR1 from 0, and has a broad temperature distribution on the rear side with respect to the traveling direction DR1 from the optical axis LB0. Then, in the region 51 of the intermediate layer 5 whose temperature is equal to or higher than the temperature Tc, the magnetization disappears,
The exchange coupling with the recording layer 6 is broken. Further, in the second reproducing layer 4, a region having a temperature equal to or higher than T1 changes to a perpendicular magnetization film, and a region having a temperature equal to or lower than T1 holds the in-plane magnetization film. Further, in the first reproducing layer 3, a region having a temperature equal to or higher than T2 changes to a perpendicular magnetization film, and a region having a temperature equal to or lower than T2 holds the in-plane magnetization film. As a result, the magnetic domains 61 and 62 existing in the region of the recording layer 6 at a temperature equal to or higher than the temperature Tc become the intermediate layer 5 due to exchange coupling.
Transfer to the intermediate layer 5 is transferred to the intermediate layer 5 as a magnetic domain 52 by exchange coupling. However, the area of the second reproducing layer 4 in contact with the magnetic domain 52 has an in-plane magnetic film. The magnetic domains 52 are not transferred to the second reproducing layer 4 for holding. Therefore, of the recording layer 6, only the magnetic domains 60 existing between the temperatures T1 to Tc are the magnetic domains 50 of the intermediate layer 5,
The magnetic domain 40 of the reproducing layer 4 and the magnetic domain 30 of the first reproducing layer 3 are transferred by exchange coupling. In this case, the temperature T2 at which the first reproducing layer 3 changes from the in-plane magnetic film to the perpendicular magnetic film is the temperature T1 at which the first reproducing layer 4 changes from the in-plane magnetic film to the perpendicular magnetic film.
Because it is lower, domain 30 is larger than domain 40. That is, in the magneto-optical recording medium 10, the magnetic domains 60 of the recording layer 6 can be transferred to the first reproducing layer 3 by exchange coupling as the magnetic domains 30 larger than the magnetic domains 60 without externally applying a magnetic field.

The second reproducing layer 4 changes to a perpendicular magnetic film at a temperature T1 or higher, and the first reproducing layer 3 changes to a perpendicular magnetic film at a temperature T2 or higher. , 62 are intermediate layers 5 whose magnetization has disappeared due to magnetostatic coupling.
Can be transferred to the second reproducing layer 4 through the region 51 of the above. Then, the magnetic domains transferred to the second reproducing layer 4 are transferred to the first reproducing layer 3 by exchange coupling. Then, among the magnetic domains formed in the recording layer 6, not only the magnetic domain 60 but also the magnetic domains 61 and 6 are formed.
2 is also transferred to the first reproducing layer 3 and a plurality of magnetic domains exist in the spot of the laser beam LB, so that each magnetic domain of the recording layer 6 cannot be detected independently. Therefore, in the present application, when reproducing a signal from the magneto-optical recording medium 10, a DC magnetic field Hex is applied from the outside. This DC magnetic field Hex
Of the second reproducing layer 4, the temperature Tc
The above region 41 has the magnetization 40 in the same direction as the DC magnetic field Hex.
Region 3 of the first reproducing layer 3 having a temperature equal to or higher than the temperature Tc.
1 has a magnetization 303 in the same direction as the DC magnetic field Hex.
As a result, in the second reproducing layer 4, the boundary between the magnetic domain 40 and the region 41 becomes clear, and in the first reproducing layer 3, the magnetic domain 30 and the region 31
And the boundary becomes clear.

That is, referring to FIG. 3, the second reproducing layer 4,
Since the first reproducing layer 3 is made of GdFeCo, the magnetic domain 40 and the magnetic domain 30 originally have the magnetization components 401 and 301 of the transition metal and the magnetization component 40 of the rare earth metal.
2, 302 exist. Then, the first reproducing layer 3, the second
The reproducing layer 4 is made of rare earth-rich GdF as described above.
Since the magnetic domains 30 and 40 are composed of eCo, the components 302 and 402 of the magnetization of the rare earth metal are dominant. Therefore, a DC magnetic field Hex is applied to the magneto-optical recording medium 10 to generate a magnetization 403 in a region of the second reproducing layer 4 adjacent to the magnetic domain 40, and a magnetization 303 in a region of the first reproducing layer 3 adjacent to the magnetic domain 30. The magnetic domains 40,
30 dominant magnetizations 402, 302 and 403, 30
3, the boundary between the magnetic domain 40 and the region 41,
And the boundary between the magnetic domain 30 and the region 31 becomes clear. As a result, only the magnetic domains 60 of the recording layer 6 are transferred to the first reproducing layer 3.

In FIG. 2, when the magnetic domains 60 of the recording layer 6 are originally transferred to the intermediate layer 5, the second reproducing layer 4, and the first reproducing layer 3, the intermediate layer 5, the The second reproducing layer 4 and the first reproducing layer 3 should display the magnetization in the direction opposite to the magnetization of the magnetic domain 60 (the intermediate layer 5 also has a rare earth element like the first reproducing layer 3 and the second reproducing layer 4). It is a metal-rich magnetic material.) However, since the recording layer 6 is made of a transition metal-rich magnetic material, in the magnetic domain 60, the component of the magnetization due to the transition metal becomes dominant, and this clearly indicates that the dominant magnetization is transferred by exchange coupling. And magnetic domain 5
Also in 0, 40, and 30, the same components as those of the magnetization of the magnetic domain 60 by the transition metal are used.

Referring again to FIG. 2, the direction of the DC magnetic field Hex is the same as the direction of the magnetization of the magnetic domain 60 of the recording layer 6, and the magnetic domain 61 having the magnetization in the opposite direction to the magnetic domain 60 is transferred to the first reproducing layer 3. When transferring and reproducing, the DC magnetic field Hex
Is applied to the magneto-optical recording medium 10. In this case, in the second reproduction layer 4 and the first reproduction layer 3, the region 4 having a temperature equal to or higher than the temperature Tc.
The magnetizations 1 and 31 are the same as the magnetizations appearing in the area where the magnetic domain 61 is transferred, but the magnetizations appearing in the areas of the second reproducing layer 4 and the first reproducing layer 3 irradiated with the laser beam LB are all Since the direction is the same as the magnetization of the magnetic domain 61, there is no problem in detecting the magnetic domain 61.

Referring to FIG. 4, a process of reproducing a signal from the magneto-optical recording medium 10 will be described. Referring to FIG. 4A, before the laser beam LB is applied to the magneto-optical recording medium 10, the intermediate layer 5 and the recording layer 6 have magnetic domains having the same direction of magnetization. Reproduction layer 3 and second reproduction layer 4
Has in-plane magnetization. In this state, when the laser beam is applied to the magneto-optical recording medium 10 and a DC magnetic field Hex is applied,
The magnetization of the region 51 in the intermediate layer 5 that is higher than the temperature Tc disappears. Then, in the second reproducing layer 4, a region at a temperature T1 or higher becomes a perpendicular magnetization film, a region at a temperature T1 or lower retains in-plane magnetization, and a region at a temperature Tc or higher has the same direction as the direction of the DC magnetic field Hex. It has a magnetization 403. Also, the first reproducing layer 3
Of these, the region above the temperature T2 becomes the perpendicular magnetization film, the region below the temperature T2 retains the in-plane magnetization, and the region above the temperature Tc has the magnetization 303 in the same direction as the direction of the DC magnetic field Hex. As a result, only the magnetic domains 60 of the recording layer 6 are magnetic domains 50,
The magnetic domain 40 and the magnetic domain 30 are enlargedly transferred to the intermediate layer 5, the second reproducing layer 4, and the first reproducing layer 3 by exchange coupling, and the magnetic domain 30 is detected by the laser beam LB (see FIG. 4B).

Then, the laser beam LB moves, and the magnetic domain 60
When the temperature of the area becomes low, the state returns to the initial state (FIG. 4C).
reference). Therefore, the signal is reproduced from the magneto-optical recording medium 10 by the magnetic domain expansion through the steps (A) to (C) of FIG. The characteristics of the magnetic material used for the intermediate layer 5 will be described with reference to FIG. The intermediate layer 5 is made of GdFe or Tb
Al, Au, Cr, Cu, S on Fe or GdFe
i, Ta, a material to which any one element of Ti is added or TbFe to Al, Au, Cr, Cu, Si, T
It is made of a material to which any one element of a and Ti is added.

FIG. 6 shows Gd which is a magnetic material used for the intermediate layer.
This shows the conditions for forming Fe or TbFe. The targets are Gd, Fe, and Tb, and Ar is used as a sputtering gas. FIG. 7 shows GdFeAl or TbFeAl which is a magnetic material used for the intermediate layer.
1 shows the formation conditions. The target is Gd,
Fe, Al or Tb, Fe, Al, and RF power is independently applied to the targets Gd, Fe, Tb, and Al. By controlling the RF power applied to the Al target, the content of Al contained in GdFeAl or TbFeAl is controlled.

Elements other than Al, such as Cr, Si, Ti,
The formation conditions of Ta, Au, and Cu are almost the same as those in the case of adding Al. In the above description, the intermediate layer 5
Has been described as a perpendicular magnetization film at room temperature.
May be an in-plane magnetized film at room temperature. GdFe is considered as a magnetic material which is an in-plane magnetized film at room temperature and has a Curie temperature Tc in the range of 180 to 210 ° C.
The composition in which dFe becomes an in-plane magnetized film at room temperature is Gd _x Fe _1-x
(X: 0.25 to 0.40). FIG. 8 shows Gd _x Fe
The forming conditions of _1-x (x: 0.25 to 0.40) are shown. G
Composition control of dFe or TbFe is mainly performed by RF power applied to the target.

In the magneto-optical recording medium 10, the temperature at which the reproducing layer changes from the in-plane magnetic film to the perpendicular magnetic film is different from the first temperature.
It is characterized by using the reproducing layer 3 and the second reproducing layer 4. FIG. 9 shows the forming conditions of the second reproducing layer 4 and FIG. 10 shows the forming conditions of the first reproducing layer 3. The temperature T2 at which the first reproducing layer 3 changes from the in-plane magnetic film to the perpendicular magnetic film is equal to the temperature T2 of the second reproducing layer 4.
Is lower than the temperature T1 at which the film changes from an in-plane magnetic film to a perpendicular magnetic film, which is achieved by reducing the content of Gd in GdFeCo. Therefore, when forming the second reproducing layer 4 and the first reproducing layer 3, when forming the first reproducing layer 3, an RF power smaller than the RF power applied to the Gd target at the time of forming the second reproducing layer 4 is used. Apply to Gd target. Thereby, the temperature at which the in-plane magnetization film changes to the perpendicular magnetization film can be lowered toward the laser beam LB irradiation side.

The magneto-optical recording medium according to the present invention is not limited to the magneto-optical recording medium 10 shown in FIG. 1, but may be a magneto-optical recording medium 20 shown in FIG. The magneto-optical recording medium 20
The magneto-optical recording medium 10 shown in FIG. 1 has a cross-sectional structure in which a third reproducing layer 33 is further inserted between the underlayer 2 and the first reproducing layer 3. It is the same as the recording medium 10. The third reproducing layer 33 is composed of rare earth metal rich Gd _x (FeCo) _1-x (x: 0.26 to 0.2).
9), is an in-plane magnetized film at room temperature, and has a temperature T3 (=
(80 to 130 ° C.). The thickness of the third reproducing layer 33 is 50 to 200 n.
m and is formed by a magnetron sputtering method.

Referring to FIG. 12, a mechanism for reproducing a signal from the magneto-optical recording medium 20 will be described. When reproducing a signal from the magneto-optical recording medium 20, a laser beam LB is irradiated from the third reproducing layer 33 side, and a DC magnetic field Hex is irradiated from the recording layer 6 side.
Is applied. The mechanism by which the magnetic domains 60 of the recording layer 6 are transferred to the intermediate layer 5, the second reproducing layer 4, and the first reproducing layer 3 by exchange coupling is the same as that described with reference to FIG. Third reproduction layer 3
3 changes to a perpendicular magnetization film at the temperature T3 or higher, and the region at the temperature Tc or higher has the magnetization 333 in the same direction as the direction of the externally applied DC magnetic field Hex. As a result, the magnetic domains 30 transferred to the first reproducing layer 3 are transferred to the third reproducing layer 33 as magnetic domains 330 by exchange coupling. In this case, the temperature T
3 is lower than the temperature T2, the magnetic domain 330 is larger than the magnetic domain 30. The other description is the same as that of FIG. Therefore, by using the third magnetic layer 33, it is possible to detect each magnetic domain of the recording layer 6 with a larger magnetic domain than the magneto-optical recording medium 10.

FIG. 13 shows the conditions for forming the magnetic material used for the third reproducing layer 33 of the magneto-optical recording medium 20. Gd _x (FeCo) _1-x (x: 0.26 or more) used for the third reproducing layer 33
0.29) is Gd _x (FeC) used for the first reproducing layer 3.
o) The Gd content is lower than _1-x (x: 0.28 to 0.31). Therefore, Gd _x used for the third reproducing layer 33
When forming (FeCo) _1-x (x: 0.26 to 0.29), the RF power applied to the Gd target is further reduced.

In the magneto-optical recording medium 10, the reproducing layer is composed of the first reproducing layer 3 and the second reproducing layer 4.
The reproducing layer 3 and the second reproducing layer 4 are different only in the content of Gd. In a certain magneto-optical recording medium, the content of Gd in the reproducing layer from the recording layer side toward the laser beam irradiation side is reduced.
In the case where the number of the reproduction layers is reduced as in the case of the second reproduction layer 4 and the first reproduction layer 3 of the magneto-optical recording medium 10, the reproduction layer of the magneto-optical recording medium is the second reproduction layer of the present invention. Layer 4 corresponds to the first reproducing layer 3.

In the magneto-optical recording medium 20, the reproducing layer is composed of the first reproducing layer 3, the second reproducing layer 4, and the third reproducing layer 33. Layer 4,
In the third reproducing layer 33, only the content of Gd is different. In a certain magneto-optical recording medium, the content of Gd in the reproducing layer is changed from the recording layer side toward the laser beam irradiation side. In the case where the number of the second reproduction layer 4, the first reproduction layer 3, and the third reproduction layer 33 of the magneto-optical recording medium 20 is reduced, the reproduction layer of the magneto-optical recording medium is the same as that of the magneto-optical recording medium 20 of the present invention. They correspond to the second reproducing layer 4, the first reproducing layer 3, and the third reproducing layer 33.

Referring to FIG. 14, a magneto-optical disk drive according to the present invention will be described. Magneto-optical disk drive 2
00 denotes an optical head 100 and a reproduction signal amplifier circuit 110
, An external synchronization signal generation circuit 120 and a servo circuit 130
, A servo mechanism 140, a spindle motor 150,
Comparator 160, demodulation circuit 170, control circuit 1
80, a drive signal generation circuit 190, a magnetic head drive circuit 210, a laser drive circuit 220, and a magnetic head 23.
0.

The optical head 100 includes the magneto-optical recording medium 10
Alternatively, a laser beam is irradiated on the laser beam 20 and its reflected light is detected. The reproduction signal amplification circuit 110 amplifies the focus error signal, the tracking error signal, the optical signal, and the magneto-optical signal detected by the optical head 100 to predetermined levels, and outputs the focus error signal and the tracking error signal to the servo circuit 130. The optical signal is output to the external synchronization signal generation circuit 120, and the magneto-optical signal is output to the comparator 16
Output to 0.

The external synchronizing signal generation circuit 120 generates an external synchronizing signal based on the input optical signal, and outputs the generated external synchronizing signal to the servo circuit 130 and the comparator 16.
0 and output to the demodulation circuit 170. Here, the optical signal is an optical signal obtained by detecting a shape formed at a constant period on the magneto-optical recording medium 10 or 20, and when the magneto-optical recording medium 10 or 20 is a land / groove type magneto-optical recording medium. Is an optical signal that detects a wobble formed on a groove wall, and in the case of a magneto-optical recording medium having a servo area, is an optical signal that detects a pit formed in the servo area at a constant period. The external synchronizing signal generation circuit 120 of the present application includes an external synchronizing signal based on not only the optical signal based on the wobbles and pits described above but also all the optical signals that detect the shape formed on the magneto-optical recording medium at a constant period. Is intended to be included.

The servo circuit 130 includes the reproduction signal amplifying circuit 1
The servo mechanism 140 is controlled to perform focus servo and tracking servo of an objective lens (not shown) in the optical head 100 based on the focus error signal and the tracking error signal input from the external synchronization signal generation circuit 120. The spindle motor 150 is rotated at a predetermined rotation speed based on the external synchronization signal thus generated. The servo mechanism 140 performs focus servo and tracking servo of an objective lens (not shown) in the optical head 100 based on control from the servo circuit 130. The spindle motor 150 rotates the magneto-optical recording medium 10 or 20 at a predetermined rotation speed under the control of the servo circuit 130.

The comparator 160 synchronizes the magneto-optical signal input from the reproduction signal amplifying circuit 110 at a predetermined level in synchronization with the external synchronizing signal input from the external synchronizing signal generating circuit 120. The demodulation circuit 170 demodulates the compared magneto-optical signal in synchronization with the external synchronization signal input from the external synchronization signal generation circuit 120, and outputs the demodulated magneto-optical signal to the external output device as reproduction data.

The control circuit 180 includes the drive signal generation circuit 19
Control 0. The drive signal generation circuit 190 detects that the magnetic head 230 applies a DC magnetic field He to the magneto-optical recording medium 10 or 20.
x and a drive signal for the optical head 100 to irradiate the magneto-optical recording medium 10 or 20 with laser light of a predetermined intensity, and generate a drive signal for applying the DC magnetic field Hex. The driving signal is output to the magnetic head driving circuit 210, and a driving signal for irradiating a laser beam having a predetermined intensity is output to the laser driving circuit 220.

The magnetic head drive circuit 210 controls the magnetic head 23 based on the drive signal from the drive signal generation circuit 190.
Drive 0. The laser drive circuit 220 is configured to control the optical head 100 based on the drive signal from the drive signal generation circuit 190.
The inside semiconductor laser (not shown) is driven. The magnetic head 230 applies a DC magnetic field Hex to the magneto-optical recording medium 10 or 20. The optical head 100 irradiates the magneto-optical recording medium 10 or 20 with laser light having a predetermined intensity.

When a signal is reproduced from the magneto-optical recording medium 10 or 20, the reproduced signal from the magnetic domain 60 of the recording layer 6 and from the magnetic domain 61 having the magnetization in the opposite direction to the magnetic domain 60 are inverted. That is, when a signal is reproduced from the magneto-optical recording medium 10 or 20 by magnetic domain expansion, a reproduced signal waveform as shown in FIG. 15A is obtained. Therefore, the comparator 160 of the magneto-optical disk device 200 compares the reproduction signal at the intermediate level between the reproduction signal of the magnetic domain 60 and the reproduction signal of the magnetic domain 61 having the magnetization in the opposite direction to the magnetic domain 60,
Binarize. In this case, the comparator 160 compares the reproduced signal in synchronization with the external synchronization signal ((b) in FIG. 15) from the external synchronization signal generation circuit 120. As a result, a binarized signal shown in FIG. 15C is obtained.

Referring again to FIG. 14, when the magneto-optical recording medium 10 or 20 is mounted on the magneto-optical disk device 200, the control circuit 180 causes the servo circuit to rotate the spindle motor 150 at a predetermined rotation speed. Control 130,
The servo circuit 130 rotates the spindle motor 150 at a predetermined rotation speed. Further, the control circuit 180 controls the drive signal generation circuit 190 so as to generate a drive signal for generating laser light having a predetermined intensity, and the drive signal generation circuit 19
0 generates a drive signal for generating laser light of a predetermined intensity, and outputs it to the laser drive circuit 220. The laser drive circuit 220 drives a semiconductor laser (not shown) in the optical head 100 based on a drive signal from the drive signal generation circuit 190, and the optical head 100 emits laser light of a predetermined intensity to the magneto-optical recording medium 10 or 20. And the reflected light is detected. The focus error signal and the tracking error signal detected by the optical head 100 are input to the servo circuit 130 via the reproduction signal amplifier circuit 110 as described above, and the focus of the objective lens (not shown) in the optical head 100 is adjusted. Servo and tracking servo are performed. The optical signal detected by the optical head 100 is input to the external synchronization signal generation circuit 120 via the reproduction signal amplification circuit 110 as described above, and the external synchronization signal generation circuit 120 outputs the external synchronization signal based on the optical signal. A signal is generated, and the generated external synchronization signal is output to the servo circuit 130, the comparator 160, and the demodulation circuit 170. Then, the servo circuit 130 synchronizes with the input external synchronization signal to
Is rotated at a predetermined rotation speed.

Thereafter, the control circuit 180 controls the DC magnetic field He.
The drive signal generation circuit 190 is controlled to generate a drive signal for generating x, and the drive signal generation circuit 190
A drive signal for generating the DC magnetic field Hex is generated and output to the magnetic head drive circuit 210. The magnetic head drive circuit 210 controls the magnetic head 2 based on the input drive signal.
30 and the magnetic head 230 moves the magneto-optical recording medium 1
A DC magnetic field Hex is applied to 0 or 20. And D
With the C magnetic field Hex applied, a magneto-optical signal is detected from the magneto-optical recording medium 10 or 20 by magnetic domain expansion as described above. The detected magneto-optical signal is input to the comparator 160 via the reproduction signal amplifier circuit 110, binarized by the comparator 160 as described with reference to FIG. In the demodulation circuit 170, the binarized magneto-optical signal is demodulated in synchronization with the external synchronization signal input from the external synchronization signal generation circuit 120, and is output to the external output device as reproduction data.

As described above, a signal is reproduced from the magneto-optical recording medium 10 or 20 by magnetic domain expansion by the operation described above.
The magnetic head 230 of the magneto-optical disk device 200 is a device capable of reproducing a signal by expanding a magnetic domain by applying only a DC magnetic field Hex to the magneto-optical recording medium 10 or 20. FIG.
With reference to FIG. 5, a flowchart illustrating a signal reproducing method according to the present invention will be described. When the reproducing operation starts (step S1), the magneto-optical recording medium 10 or 20 is irradiated with a laser beam having a predetermined intensity as described above (step S2), and a DC magnetic field Hex is applied to the magneto-optical recording medium 10 or 20. (Step S3). Thereafter, a magneto-optical signal is detected from the magneto-optical recording medium 10 or 20 by magnetic domain expansion, binarized by the comparator 160, demodulated by the demodulation circuit 170, and output as reproduction data (step S4). Then, the signal reproducing operation ends (step S5).

In reproducing the signal from the magneto-optical recording medium 10 or 20 by expanding the magnetic domain in the magneto-optical disk device 200 described above, the magneto-optical recording medium 10 or 2
By applying the DC magnetic field ex to 0, the magnetization of the regions of the first reproducing layer 3, the second reproducing layer 4, and the third reproducing layer 33 constituting the magneto-optical recording medium 10 or 20, which is higher than the temperature Tc, is changed to the DC magnetic field. Hex direction. This makes it possible to transfer each magnetic domain of the recording layer 6 to the first reproducing layer 3 or the third reproducing layer 33 with high resolution. Further, since no alternating magnetic field is applied to the magneto-optical recording medium 10 or 20, power consumption can be reduced. This is also true for the signal reproducing method described with reference to FIG.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a magneto-optical recording medium according to the present invention.

FIG. 2 is a diagram illustrating a signal reproducing mechanism of the magneto-optical recording medium shown in FIG.

FIG. 3 is a diagram for explaining in detail magnetization of each layer in the signal reproducing mechanism of FIG. 2;

FIG. 4 is a diagram for explaining a process of reproducing a signal from the magneto-optical recording medium shown in FIG.

5 is a diagram illustrating characteristics of a magnetic material used for an intermediate layer of the magneto-optical recording medium shown in FIG.

FIG. 6 shows G used for the intermediate layer of the magneto-optical recording medium shown in FIG.
These are the conditions for forming dFe and TbFe.

FIG. 7 shows G used for the intermediate layer of the magneto-optical recording medium shown in FIG.
These are the conditions for forming dFeAl and TbFeAl.

FIG. 8 shows conditions for forming GdFe and TbFe which are in-plane magnetized films at room temperature.

9 shows the conditions for forming Gd _x (FeCo) _1-x (x: 0.28 to 0.31) used for the second reproducing layer of the magneto-optical recording medium shown in FIG.

FIG. 10 shows Gd _x (FeCo) _1-x (x: 0.30 to 0.33) used for the first reproducing layer of the magneto-optical recording medium shown in FIG.
Are the forming conditions.

FIG. 11 is another sectional structural view of the magneto-optical recording medium according to the present invention.

12 is a diagram illustrating a signal reproducing mechanism of the magneto-optical recording medium shown in FIG.

FIG. 13 shows Gd _x (FeCo) _1-x (x: 0.26 to 0.2) used for the third reproducing layer of the magneto-optical recording medium shown in FIG.
This is the formation condition of 9).

FIG. 14 is a block diagram of a magneto-optical disk drive according to the present invention.

FIG. 15 is a diagram illustrating the operation of the comparator of the magneto-optical disk device shown in FIG.

FIG. 16 is a flowchart showing a signal reproducing method according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transparent substrate, 2 Underlayer, 3rd reproduction | regeneration layer, 4
Second reproducing layer, 5 intermediate layer, 6 recording layer, 7 protective layer, 1
0, 20 magneto-optical recording medium, 30, 40, 50, 52,
60, 61, 62, 63 magnetic domains, 31, 41, 51 regions, 301, 302, 303, 333, 401, 40
2, 403 magnetization, 33 third reproduction layer, 100 optical head, 110 reproduction signal amplification circuit, 120 external synchronization signal generation circuit, 130 servo circuit, 140 servo mechanism, 150 spindle motor, 160 comparator, 170 demodulation circuit, 180 control circuit , 190 drive signal generation circuit, 200 magneto-optical disk drive, 210
Magnetic head drive circuit, 220 laser drive circuit, 230
Magnetic head

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 11/105 563 G11B 11/105 563G 586 586M (72) Inventor Hiroki Ishida 2 Keihanhondori, Moriguchi-shi, Osaka 5-5-5 Sanyo Electric Co., Ltd. F-term (reference) 5D075 AA03 CC11 CF03 EE03 FF04 FF12

Claims (7)

[Claims] A first magnetic layer for recording a signal, a second magnetic layer formed in contact with the first magnetic layer and having a Curie temperature Tc higher than room temperature, and formed in contact with the second magnetic layer. A third magnetic layer having a first transition temperature T1 that changes from an in-plane magnetic film to a perpendicular magnetic film, and a second transition that is formed in contact with the third magnetic layer and changes from the in-plane magnetic film to a perpendicular magnetic film. And a fourth magnetic layer having a temperature T2, wherein the magneto-optical recording medium satisfies the relationship of Tc>T1> T2. 2. The method according to claim 1, wherein the second magnetic layer is made of GdFe or Td.
2. The magneto-optical recording medium according to claim 1, comprising bFe. 3. The method according to claim 1, wherein the second magnetic layer comprises Al, A, GdFe.
2. The magneto-optical recording medium according to claim 1, comprising a material to which one of u, Cr, Cu, Si, Ta, and Ti is added. 4. The method according to claim 1, wherein the second magnetic layer is made of Al, A or TdFe.
2. The magneto-optical recording medium according to claim 1, comprising a material to which one of u, Cr, Cu, Si, Ta, and Ti is added. 5. The method according to claim 1, wherein the third magnetic layer is formed of Gd _1-x (FeC
o) _x (x: 0.30 to 0.33), and the fourth magnetic layer is formed of Gd _1-x (FeCo) _x (x: 0.2
The magneto-optical recording medium according to any one of claims 1 to 4, wherein the medium comprises 8 to 0.31). 6. A magneto-optical disk device for reproducing a signal from the magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is a magneto-optical disk device that reproduces a signal from the magneto-optical recording medium. A magneto-optical disk device comprising: an optical head that irradiates a laser beam and detects a reflected light thereof; and a magnetic head that applies a DC magnetic field to the magneto-optical recording medium. 7. A reproducing method for reproducing a signal from a magneto-optical recording medium according to claim 1, wherein a DC magnetic field is applied to the magneto-optical recording medium, and the DC magnetic field is applied to the magneto-optical recording medium. A laser beam is irradiated from the fourth magnetic layer side to a region to which is applied, and a reflected light of the laser beam from the region is detected to reproduce a signal from the magneto-optical recording medium.