JPH07141709A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To increase the reproducing signals and to obtain large reproducing signals even when a short wavelength semiconductor laser is used for reproducing by using a perpendicular magnetization film as a read-only magnetic layer. CONSTITUTION:The intensity distribution of the focused light beam 4 is a Gaussian distribution so that the temp. distribution in the magneto-optical recording medium becomes a Gaussian distribution. The intermediate magnetic layer 2 is in a intraplane magnetization state at room temp. and only when the center area of the beam 4 is enough increased, the layer 2 becomes in a perpendicular magnetization state. Thus, the magnetization information of the recording magnetic layer 3 only in this area is transferred to the read-only magnetic layer 1 by strong exchange coupling force. On the other hand, the area except for the center area of the beam 4 where temp. is not enough increased is in a intraplane magnetization state. The magnetization information in this area of the layer 3 is not transferred to the layer 1 but the magnetization direction of the layer 1 is alined to the direction of a magnetic field H externally applied. Further, by controlling the intensity of the light beam, the temp. distribution in the layer 2 can be controlled.

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 such as a magneto-optical disk, a magneto-optical tape, a magneto-optical card and a magneto-optical recording element applied to a magneto-optical recording device.

[0002]

2. Description of the Related Art Magneto-optical discs are being researched and developed as rewritable optical discs, some of which have already been
It has been put to practical use as an external memory for computers. Since a magneto-optical disk uses a perpendicular magnetization film as a recording medium and performs recording and reproduction using light, it is characterized by a larger recording capacity than a floppy disk or a hard disk using an in-plane magnetization film.

However, in recent years, a memory having a larger capacity is required, and researches for further improving the recording density of hard disk as well as magneto-optical disk have been vigorously conducted.

[0004]

However, in the magneto-optical disk, the recording density depends on the size of the light beam used for recording and reproduction on the recording medium, and reproduction is possible depending on the diameter of the light beam. There is a problem that the size of the recording bit is restricted. That is, when the recording bit diameter and the recording bit interval become smaller than the light beam diameter, noise is generated because a plurality of bits including adjacent bits enter the focused light beam. The problem is that the number of bits increases and it becomes impossible to reproduce each bit separately.

In view of this point, in Japanese Unexamined Patent Publication (Kokai) No. 5-81717, there is shown a recording layer for magneto-optical recording of information and an in-plane magnetization in which in-plane magnetic anisotropy is dominant at room temperature, while a perpendicular magnetic field increases with an increase in temperature. A magneto-optical recording medium provided with a read-out layer that shifts to perpendicular magnetization having a dominant anisotropy has been proposed, and it has become possible to reproduce a recording bit smaller than before and to significantly improve the recording density.

However, according to this method, there is a problem that the reproduction signal level is lowered due to the reduction of the recording bit. Further, there is a problem that the reproduction signal level is lowered with the shortening of the wavelength of the semiconductor laser in recent years.

[0007]

The above problems can be solved by the present invention described below. That is, the present invention has a read magnetic layer which has a high Curie temperature and a low coercive force and is in a perpendicular magnetization state, and a Curie temperature and a high coercive force which are relatively lower than those of the read magnetic layer and which has a perpendicular magnetization state. A magneto-optical recording medium comprising a recording magnetic layer and an intermediate magnetic layer which is provided between the read magnetic layer and the recording magnetic layer and has an in-plane magnetization state at room temperature and a perpendicular magnetization state when the temperature rises. The present invention provides a magneto-optical recording / reproducing device characterized by reproducing while applying a magnetic field.

The present invention also has a read magnetic layer having a high Curie temperature and being essentially in-plane magnetized, and a Curie temperature relatively lower than that of the read magnetic layer, and having a perpendicular magnetized state. A magneto-optical recording medium comprising a recording magnetic layer and an intermediate magnetic layer which is provided between the read magnetic layer and the recording magnetic layer and has an in-plane magnetization state at room temperature and a perpendicular magnetization state when the temperature rises. It is provided.

[0009]

According to the first configuration of the present invention, the information of the recording magnetic layer only in the portion where the intermediate magnetic layer is in the perpendicular magnetization state is transferred to the read magnetic layer, and the magnetization of the read magnetic layer in other portions is magnetized. By orienting the direction to the direction of the magnetic field applied from the outside, it is possible to reproduce the recording bit smaller than before, and the recording density is remarkably improved, and as the read magnetic layer, the transition metal of the transition metal is used rather than the sublattice magnetization of the rare earth metal. By using a perpendicular magnetization film made of GdFeCo having a relatively large sublattice magnetization, it is possible to increase the reproduction signal.

Further, as a read magnetic layer, NdGdF is used.
By using the perpendicularly magnetized film of eCo or Pt / Co artificial lattice film, it becomes possible to increase the reproduction signal when reproduction is performed using a semiconductor laser having a short wavelength (400 nm to 600 nm). .

The contents of the prior application, Japanese Patent Application No. 5-14168, relating to the first structure of the present invention will be compared with the first structure of the present invention. Japanese Patent Application No. 5-14168 discloses a read layer that exhibits perpendicular magnetization from room temperature to the Curie temperature on a substrate, and a transfer layer that exhibits almost in-plane magnetization at room temperature and shifts from in-plane magnetization to perpendicular magnetization at room temperature or higher. Using a magneto-optical recording medium characterized in that a recording layer exhibiting perpendicular magnetization from room temperature to the Curie temperature is sequentially laminated,
By transferring the information of the recording magnetic layer only in the part where the transfer layer is in the perpendicular magnetization state to the read layer and directing the magnetization direction of the read layer in the other part to the direction of the externally applied magnetic field, This makes it possible to reproduce small recording bits and significantly improve the recording density.

The read magnetic layer, intermediate magnetic layer and recording layer of the first structure of the present invention correspond to the read layer, transfer layer and recording layer of Japanese Patent Application No. 5-14168, respectively. The first configuration of the present invention is intended to further improve the reproduction characteristics of Japanese Patent Application No. 5-14168. That is, in Japanese Patent Application No. 5-14168, DyFeCo, GdTbFe, NdDyFeC are used as the read layer.
Although O, GdDyFeCo, and GdTbFeCo are listed, the first configuration of the present invention is, as the read magnetic layer, a perpendicular magnetization film made of GdFeCo in which the sublattice magnetization of the transition metal is relatively larger than the sublattice magnetization of the rare earth metal. , It is possible to increase the reproduction signal, and Nd
By using a perpendicularly magnetized film of GdFeCo or Pt / Co artificial lattice film, a short wavelength (400 nm to 600 n
When the semiconductor laser of m) is used for reproduction, the reproduction signal can be increased.

In the first structure of the present invention, Tb is used as the rare earth element of the rare earth-transition metal alloy which is the read magnetic layer.
Alternatively, by not adopting Dy, the coercive force of the read magnetic layer can be reduced, the external magnetic field applied during reproduction can be reduced, and a larger Kerr rotation angle, that is, reproduction output can be obtained.

Next, according to the second aspect of the present invention, the information of the recording magnetic layer only in the portion where the intermediate magnetic layer is in the perpendicular magnetization state is transferred to the reading magnetic layer by the exchange coupling force, and the other information is transferred. By making the part of the read magnetic layer in-plane magnetized, it is possible to reproduce a smaller recording bit than in the past, and the recording density is significantly improved. The reproduction signal can be increased by using the magnetic film of GdFeCo having a relatively large sublattice magnetization and having an essentially in-plane magnetization state.

As the read magnetic layer, NdGdF is used.
By using a magnetic film having an essentially in-plane magnetization state such as eCo or a Pt / Co artificial lattice film, a short wavelength (400 n
(m to 600 nm), it is possible to increase the reproduction signal when reproduction is performed using a semiconductor laser.

[0016]

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a first embodiment of the magneto-optical recording medium of the present invention, which has a high Curie temperature and a low coercive force.
The read magnetic layer 1 in the perpendicular magnetization state, the recording magnetic layer 3 having a Curie temperature and a high coercivity relatively lower than those of the read magnetic layer, and in the perpendicular magnetization state, the read magnetic layer and the recording magnetic layer. The intermediate magnetic layer 2 is provided between the layers and has an in-plane magnetization state at room temperature and a perpendicular magnetization state when the temperature rises.

In the first configuration, since the light intensity distribution of the condensed light beam 4 is a Gaussian distribution, the temperature distribution of the magneto-optical recording medium is also a Gaussian distribution. The intermediate magnetic layer 2 is in-plane magnetized at room temperature, and becomes perpendicularly magnetized due to the temperature rise. Therefore, only the part where the temperature of the central portion of the light beam 4 has sufficiently risen becomes perpendicularly magnetized. The magnetization information of the recording magnetic layer 3 only in the portion of the intermediate magnetic layer 2 which has become the perpendicular magnetization state is transferred to the reading magnetic layer 1 by the strong exchange coupling force. On the other hand, a portion of the intermediate magnetic layer 2 other than the central portion of the light beam 4 where the temperature has not risen sufficiently has an in-plane magnetization state. The magnetization information of the portion of the recording magnetic layer 3 in the in-plane magnetization state of the intermediate magnetic layer 2 is not transferred to the read magnetic layer 1 because the exchange coupling force is weak, and the read magnetic layer 1 is magnetized in the external direction. Magnetic field H applied from
It will face the direction of _read .

By adjusting the intensity of the light beam, it is possible to adjust the temperature distribution of the intermediate magnetic layer 2, that is, the range of the portion in the perpendicular magnetization state, which is smaller than the beam diameter of the light beam 4, The magnetization information recorded in the recording magnetic layer 3 at a pitch can be read and reproduced from the magnetic layer 1.

Next, FIG. 2 shows a second embodiment of the magneto-optical recording medium of the present invention, which has a high Curie temperature.
The read magnetic layer 1 which is essentially in the in-plane magnetization state, the recording magnetic layer 3 which has a Curie temperature relatively lower than that of the read magnetic layer and which is in the perpendicular magnetization state, and these read magnetic layer and recording magnetic layer. The intermediate magnetic layer 2 is provided between the layers and has an in-plane magnetization state at room temperature and a perpendicular magnetization state when the temperature rises.

In the second configuration, as in the first configuration, the light intensity distribution of the condensed light beam 4 is a Gaussian distribution, so the temperature distribution of the magneto-optical recording medium is also a Gaussian distribution. The intermediate magnetic layer 2 is in-plane magnetized at room temperature, and becomes perpendicularly magnetized due to the temperature rise. Therefore, only the part where the temperature of the central portion of the light beam 4 has sufficiently risen becomes perpendicularly magnetized. The magnetization information of the recording magnetic layer 3 only in the portion of the intermediate magnetic layer 2 which has been in the perpendicular magnetization state is transferred to the read magnetic layer 1 by a strong exchange coupling force, and the read magnetic layer 1 is perpendicular to the in-plane magnetization state. It becomes a magnetized state. On the other hand, a portion of the intermediate magnetic layer 2 other than the central portion of the light beam 4 where the temperature has not risen sufficiently has an in-plane magnetization state. The magnetization information of the portion of the recording magnetic layer 3 in the in-plane magnetization state of the intermediate magnetic layer 2 is not transferred to the read magnetic layer 1 because the exchange coupling force is weak, and the magnetization direction of the read magnetic layer 1 is
It remains in the in-plane magnetization state. Read-out magnetic layer 1 during reproduction
Since the Kerr effect is used to reproduce the magnetization direction of, the magnetization information of only the portion where the read magnetic layer 1 is in the perpendicular magnetization state is reproduced.

By adjusting the intensity of the light beam, it is possible to adjust the temperature distribution of the intermediate magnetic layer 2, that is, the range of the portion in the perpendicular magnetization state, which is smaller than the beam diameter of the light beam 4, The magnetization information recorded in the recording magnetic layer 3 at a pitch can be read and reproduced from the magnetic layer 1.

Next, Japanese Patent Application Laid-Open No. 5-8171
In order to compare No. 7 with the present invention, FIG.
The structure of the magneto-optical recording medium proposed in No. 717 is shown. This magneto-optical recording medium is composed of a recording magnetic layer 3 which is in a perpendicular magnetization state, and a reading magnetic layer 5 which is in a plane magnetization state at room temperature and becomes a perpendicular magnetization state when the temperature rises. In the magneto-optical recording medium having this structure, reproduction is performed by the following method. Since the light intensity distribution of the condensed light beam 4 has a Gaussian distribution, the temperature distribution of the magneto-optical recording medium also has a Gaussian distribution. The read magnetic layer 5 is in the in-plane magnetization state at room temperature, and becomes the perpendicular magnetization state when the temperature rises. Therefore, only the portion where the temperature of the central portion of the light beam 4 sufficiently rises becomes the perpendicular magnetization state. The magnetization direction of the read magnetic layer 5 in this perpendicularly magnetized state becomes the same as the magnetization direction of the recording magnetic layer 3 due to exchange coupling with the recording magnetic layer 3. At the time of reproduction, since the magnetization direction of the read magnetic layer 1 is reproduced by using the Kerr effect, the magnetization information of only the portion of the read magnetic layer 1 in the perpendicular magnetization state is reproduced.

Therefore, also in Japanese Unexamined Patent Publication No. 5-81717, the temperature distribution of the intermediate magnetic layer 2, that is, the range of the portion in the perpendicular magnetization state is adjusted by adjusting the intensity of the light beam as in the present invention. The magnetization information recorded in the recording magnetic layer 3 can be read and reproduced from the magnetic layer 1 with a diameter and pitch smaller than the beam diameter of the light beam 4.

However, in JP-A-5-81717, the readout layer 5 has an in-plane magnetization state at room temperature,
The material must be specified because the material must be in the perpendicular magnetization state as the temperature rises. For example, when GdFeCo is used as the readout layer 5, the composition of GdFeCo is set to a rare earth metal (R) in order to have an in-plane magnetization state at room temperature and a perpendicular magnetization state as the temperature rises.
E) Gd and transition metal (TM) FeCo sublattice magnetic moment balance compensating composition, Gd
It is necessary to prepare a film containing a large amount of, that is, a film in a RErich state.

On the other hand, in the present invention, since the operation of limiting the read region is performed by the intermediate magnetic layer 2, the read layer 1 is in-plane magnetized at room temperature, and is set to be perpendicularly magnetized as the temperature rises. There is no need. Therefore, the degree of freedom in selecting the material of the readout layer 1 is increased, and the reproduction signal level can be increased.

From the above, it is understood that the same material as the readout layer 5 of JP-A-5-81717 can be used as the intermediate magnetic layer 2 in the present invention.

For example, it is possible to use GdFeCo (RErich) having a composition of Gd _0.26 Fe _0.61 Co _0.13 .

Next, the same GdFeCo can be used as the material of the read magnetic layer 1. However, this read magnetic layer 1 has an in-plane magnetization state at room temperature,
It is not necessary to establish a perpendicular magnetization state as the temperature rises.

FIG. 3 shows the composition dependence of the Curie temperature T _C and the compensation temperature T _COMP of Gd _X (Fe _0.82 Co _0.18 ) _1-X , and the Gd content is the boundary of the compensation temperature. The portion where the Fe content is high becomes RErich, and the portion where the FeCo content is high becomes TMrich. From this figure, TMrich
It can be seen that the Curie temperature of GdFeCo on the side is higher. Further, FIG. 4 shows the relationship between the Curie temperature and the Kerr rotation angle of the rare earth-transition metal alloy thin film. From this figure, it is understood that in the rare earth-transition metal alloy thin film, the higher the Curie temperature, the larger the Kerr rotation angle. From FIGS. 3 and 4, it can be seen that in GdFeCo, the material on the TMrich side has a larger Kerr rotation angle, that is, the reproduction output.

In JP-A-5-81717, only GdFeCo on the RErich side can be used as the read layer 5, but in the present invention, GdFeCo on the TMrich side can be used as the read magnetic layer 1. Yes, compared to JP-A-5-81717,
It is possible to increase the car rotation angle, that is, the reproduction output.

Here, the characteristics of GdFeCo on the TMrich side will be described in more detail.

As an example, Gd _X (Fe _0.82 Co in FIG. 3 is used.
_{In the case of 0.18} ) _1-X , in the range of 0.15 <X <0.20, it is in a perpendicular magnetization state, and can be applied to the magneto-optical recording medium of the first constitution of the present invention. On the other hand, X
Since the in-plane magnetization state occurs at <0.15, it can be applied to the magneto-optical recording medium having the second structure of the present invention. However, when X <0.05, the in-plane magnetic anisotropy of GdFeCo becomes too strong, and the magnetization direction of the read magnetic layer 1 can be made perpendicular to the film surface by the exchange coupling force from the intermediate magnetic layer 2. Since it disappears, it is necessary that X ≧ 0.05.

Next, as other materials for the read magnetic layer 1 of the present invention, NdFeCo, NdGdFeCo and Pt are used.
The / Co artificial lattice film will be described.

FIG. 5 shows the Kerr rotation angle (θ) of those materials.
_This shows the wavelength dependence of _K ). JP-A-5-817
No. 17, Gd usable as the readout layer 5
The characteristics of _0.26 Fe _0.61 Co _0.13 are also shown in the figure for comparison. From this figure, it is understood that the GdFeCo usable in JP-A-5-81717 has a smaller Kerr rotation angle as the wavelength of light becomes shorter. On the other hand, GdF
It can be seen that by adding Nd to eCo to obtain NdGdFeCo, the Kerr rotation angle increases at a short wavelength. This tendency depends on the amount of Nd added, and pure NdF
It becomes even more noticeable in eCo. Also, Pt / C
A similar tendency exists for artificial lattice films.

In NdGdFeCo, the magnetization state changes depending on the content of Nd, and Nd shown in FIG.
_0.05 Gd _0.20 Fe _0.63 Co _0.12 is in the perpendicular magnetization state,
Nd _0.20 Fe _0.61 Co _0.42 has an in-plane magnetization state. That is, by applying the former to the first configuration of the present invention and applying the latter to the second configuration of the present invention, a magneto-optical device having a large Kerr rotation angle even at a short wavelength and a large reproduction output can be obtained. It becomes possible to provide a recording medium.

Regarding the Pt / Co artificial lattice film, the Pt _{0.8 nm} / Co _{0.45 nm} film shown in FIG. 5 is in the perpendicular magnetization state, and the film thickness composition should be changed to Pt _{0.5 nm} / Co _{0.65 nm.} By this, it is possible to form a Pt / Co film having a similar in-plane magnetization state with wavelength dependence of the Kerr rotation angle. The first configuration of the present invention is applied to the former, and the Pt / Co film of the present invention is applied to the latter. By applying the configuration of No. 2, it is possible to provide a magneto-optical recording medium which has a large Kerr rotation angle even at a short wavelength and can obtain a large reproduction output.

FIG. 6 shows the structure of a magneto-optical disk using the magneto-optical recording medium 8 according to the present invention. Substrate 6,
It is composed of a transparent dielectric layer 7, a magneto-optical recording medium 8, a protective layer 9, and a back coat layer 10. The laser beam 4 is focused on the magneto-optical recording medium 8 to perform recording / reproduction.

The substrate 6 has a diameter of 86 mm, an inner diameter of 15 mm,
Although not shown, a disc-shaped glass substrate having a thickness of 1.2 mm, on one surface thereof, an uneven guide track for guiding a light beam has a pitch of 1.6 μm and a groove (concave) width of 0. The width of the land (convex portion) is 8 μm and the width is 0.8 μm.

On the side of the substrate 1 where the guide track is located, AlN is formed as the transparent dielectric layer 7 with a thickness of 60 nm.

A magneto-optical recording medium 8 comprising a read magnetic layer 1, an intermediate magnetic layer 2 and a recording magnetic layer 3 is formed on the transparent dielectric layer 7.

A magneto-optical disk having six types of magneto-optical recording media 8 was prepared corresponding to the first and second configurations of the present invention. At the same time, as a comparative example, the conventional magneto-optical disk shown in FIG. 7 was similarly prepared.

Example 1 As the read magnetic layer 1, a GdF having a TMrich composition, which is a rare earth-transition metal alloy thin film, was used.
eCo was formed to a thickness of 50 nm. This GdFeCo film is in a perpendicular magnetization state, and its composition is Gd _0.18 (Fe
_0.82 Co _0.18 ) _0.82 , the Curie temperature is about 340 ℃
Met.

Next, as the intermediate magnetic layer 2, a rare earth-transition metal alloy thin film of GdFeCo of RErich composition was formed with a thickness of 50 nm. The composition of GdFeCo is Gd
The Curie temperature was _0.26 (Fe _0.78 Co _0.22 ) _0.74 , and the Curie temperature was about 300 ° C. At the temperature of about 100 ° C., the in-plane magnetization state transitioned to the perpendicular magnetization state.

Next, as the recording magnetic layer 3, DyFeCo having a TMrich composition, which is a rare earth-transition metal alloy thin film, was formed with a thickness of 50 nm. The composition of DyFeCo is Dy
_0.23 (Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature was about 200 ° C.

Example 2 As the read magnetic layer 1, a GdF having a TMrich composition, which is a rare earth-transition metal alloy thin film, is used.
eCo was formed to a thickness of 50 nm. This GdFeCo film is essentially in-plane magnetized, and its composition is Gd.
_{It was 0.13} (Fe _0.82 Co _0.18 ) _0.87 and its Curie temperature was about 360 ° C.

Next, as the intermediate magnetic layer 2, a rare earth-transition metal alloy thin film of GdFeCo of RErich composition was formed with a thickness of 50 nm. The composition of GdFeCo is Gd
The Curie temperature was _0.26 (Fe _0.78 Co _0.22 ) _0.74 , and the Curie temperature was about 300 ° C. At the temperature of about 100 ° C., the in-plane magnetization state transitioned to the perpendicular magnetization state.

Next, as the recording magnetic layer 3, DyFeCo having a TMrich composition, which is a rare earth transition metal alloy thin film, was formed to a thickness of 50 nm. The composition of DyFeCo is Dy
_0.23 (Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature was about 200 ° C.

Example 3 As the read magnetic layer 1, a rare earth-transition metal alloy thin film of NdGdFeCo having a thickness of 5 was used.
It was formed at 0 nm. This NdGdFeCo film is in a perpendicular magnetization state, and its composition is Nd _0.05 Gd _0.20 Fe _0.63.
It was Co _0.12 .

Next, as the intermediate magnetic layer 2, a rare earth-transition metal alloy thin film of GdFeCo of RErich composition was formed with a thickness of 50 nm. The composition of GdFeCo is Gd
The Curie temperature was _0.26 (Fe _0.78 Co _0.22 ) _0.74 , and the Curie temperature was about 300 ° C. At the temperature of about 100 ° C., the in-plane magnetization state transitioned to the perpendicular magnetization state.

Next, as the recording magnetic layer 3, DyFeCo having a TMrich composition, which is a rare earth transition metal alloy thin film, was formed to a thickness of 50 nm. The composition of DyFeCo is Dy
_0.23 (Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature was about 200 ° C.

Example 4 As the read magnetic layer 1, a rare earth-transition metal alloy thin film of NdFeCo having a thickness of 50 n was used.
m. This NdFeCo film is essentially in-plane magnetized, and its composition is Nd _0.20 Fe _0.61 Co _0.42.
Met.

Next, as the intermediate magnetic layer 2, a rare earth-transition metal alloy thin film of GdFeCo of RErich composition was formed with a thickness of 50 nm. The composition of GdFeCo is Gd
The Curie temperature was _0.26 (Fe _0.78 Co _0.22 ) _0.74 , and the Curie temperature was about 300 ° C. At the temperature of about 100 ° C., the in-plane magnetization state transitioned to the perpendicular magnetization state.

Next, as the recording magnetic layer 3, DyFeCo having a TMrich composition, which is a rare earth-transition metal alloy thin film, was formed with a thickness of 50 nm. The composition of DyFeCo is Dy
_0.23 (Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature was about 200 ° C.

(Example 5) As the read magnetic layer 1, P
A t / Co artificial lattice film was formed with a thickness of 25 nm. This P
The t / Co artificial lattice film was in the perpendicular magnetization state, and the film thickness ratio thereof was Pt _{0.8 nm} / Co _{0.45 nm} .

Next, as an intermediate magnetic layer 2, a rare earth-transition metal alloy thin film of GdFeCo of RErich composition was formed with a thickness of 50 nm. The composition of GdFeCo is Gd
The Curie temperature was _0.26 (Fe _0.78 Co _0.22 ) _0.74 , and the Curie temperature was about 300 ° C. At the temperature of about 100 ° C., the in-plane magnetization state transitioned to the perpendicular magnetization state.

Next, as the recording magnetic layer 3, DyFeCo having a TMrich composition, which is a rare earth-transition metal alloy thin film, was formed with a thickness of 50 nm. The composition of DyFeCo is Dy
_0.23 (Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature was about 200 ° C.

Example 6 As the read magnetic layer 1, P
A t / Co artificial lattice film was formed with a thickness of 25 nm. This P
The t / Co artificial lattice film is essentially in-plane magnetized state,
The respective film thickness ratios were Pt _{0.5 nm} / Co _{0.65 nm} .

Next, as an intermediate magnetic layer 2, a rare earth-transition metal alloy thin film of GdFeCo of RErich composition was formed with a thickness of 50 nm. The composition of GdFeCo is Gd
The Curie temperature was _0.26 (Fe _0.78 Co _0.22 ) _0.74 , and the Curie temperature was about 300 ° C. At the temperature of about 100 ° C., the in-plane magnetization state transitioned to the perpendicular magnetization state.

Next, as the recording magnetic layer 3, DyFeCo having a TMrich composition, which is a rare earth-transition metal alloy thin film, was formed with a thickness of 50 nm. The composition of DyFeCo is Dy
_0.23 (Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature was about 200 ° C.

(Comparative Example) As the readout layer 5, a rare earth-transition metal alloy thin film of GdFeCo of RErich composition was used.
Was formed with a thickness of 50 nm. The composition of GdFeCo is G
d _0.26 (Fe _0.78 Co _0.22 ) _0.74 , the Curie temperature was about 300 ° C., and at the temperature of about 100 ° C., the in-plane magnetization state transitioned to the perpendicular magnetization state.

Next, as the recording magnetic layer 3, DyFeCo having a TMrich composition, which is a rare earth-transition metal alloy thin film, was formed to a thickness of 50 nm. The composition of DyFeCo is Dy
_0.23 (Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature was about 200 ° C.

On the magneto-optical recording medium 8 in the above six types of examples and comparative examples, AlN is formed as the protective layer 9 with a thickness of 20 nm.

On the protective layer 9, a polyurethane acrylate-based UV-curable resin is formed as the overcoat layer 10 with a thickness of 5 μm.

The guide track on the surface of the substrate 6 was directly formed on the glass surface by the reactive ion etching method.

The transparent dielectric layer 7, the magneto-optical recording medium 8 and the protective layer 9 were all formed by the sputtering method in the same sputtering apparatus without breaking the vacuum.

AlN of the transparent dielectric layer 7 and the protective layer 9 is
It was formed by a reactive sputtering method in which an Al target was sputtered in an N ₂ gas atmosphere.

For the rare earth-transition metal alloy thin film in the magneto-optical recording medium 8, G was deposited on the FeCo alloy target.
So-called composite target in which d, Nd or Dy chips are arranged, or GdFeCo, GdNdFeC
It was formed by sputtering with Ar gas using a ternary alloy target of o, NdFeCo and DyFeCo. For the Pt / Co artificial lattice film, Pt and C
The target of o was sputtered at the same time and the shutter was operated to form it.

The overcoat layer 10 was formed by applying a resin with a spin coater and then applying ultraviolet rays with an ultraviolet irradiation device to cure the resin.

Using the magneto-optical disc formed as described above, the following recording / reproducing experiment was conducted.

First, for the magneto-optical disks of Examples 1 and 2 and the magneto-optical disk of the comparative example, a wavelength of 780n
Laser power at a frequency of 10 MHz was applied to a magneto-optical recording medium at a laser beam irradiation position by rotating the magneto-optical recording medium at a linear velocity of 10 m / s and applying a recording magnetic field of 25 kA / m. Recording is performed on the recording magnetic layer 3 with a period of 1 μm by 0.5 μm.
An inverted magnetic domain having a length of m was formed. Next, information was reproduced with a laser power of 2 mW. Example 1 during reproduction
In Example 2, reproduction was performed while applying a magnetic field of 15 kA / m from the outside, and in Example 2, reproduction was performed without applying a magnetic field.

A reproduction signal of 10 MHz could be obtained in both the embodiment and the comparative example. In this experiment, since the beam diameter of the laser beam focused on the magneto-optical recording medium 8 is about 1.4 μm, the diameter smaller than the beam diameter,
It was confirmed that the magnetization information recorded at the pitch can be reproduced.

Further, when comparing the output levels of the respective reproduction signals, the magneto-optical disk of the first embodiment increased the output level by 1.5 dB with the output level of the reproduction signal of the comparative example as a reference, and the optical level of the second embodiment. It was confirmed that the output level of the magnetic disk increased by 2.2 dB.

Next, with respect to the magneto-optical disks of Examples 1 to 6 and the magneto-optical disk of the comparative example, the wavelength is 488 nm.
In the state where a linear magnetic velocity of the magneto-optical recording medium is 10 m / s and the recording magnetic field of 25 kA / m is applied at the laser beam irradiation position using the Ar laser of
Recording was performed by pulse-modulating the laser power at a frequency of 16.67 MHz, and recorded on the recording magnetic layer 3 at a period of 0.6 μm.
An inverted magnetic domain having a length of 0.3 μm was formed. Next, information was reproduced with a laser power of 2 mW. During playback,
In Example 1, Example 3, and Example 5, 1 from the outside
Reproduction was performed while applying a magnetic field of 5 kA / m. In Examples 2, 4 and 6, reproduction was performed without applying a magnetic field.

16.67 MHz in both Examples and Comparative Examples
It was possible to obtain the reproduction signal of. In this experiment, since the beam diameter of the laser beam focused on the magneto-optical recording medium 8 was about 0.8 μm, it was confirmed that the magnetization information recorded with a diameter and pitch smaller than the beam diameter could be reproduced. .

Further, when comparing the output levels of the respective reproduction signals, the magneto-optical disk of the first embodiment shows an increase of 1.2 dB in the output level of the magneto-optical disk based on the output level of the reproduction signal of the comparative example. The output level of the magnetic disk increased by 2.0 dB, and that of the magneto-optical disk of Example 3 was 2.8 d.
The B output level increases, the magneto-optical disk of Example 4 increases the 2.3 dB output level, the magneto-optical disk of Example 5 increases the 3.0 dB output level, and the magneto-optical disk of Example 6 increases 3. It was confirmed that the output level of 0.0 dB increased.

[0076]

According to the first and second configurations of the present invention,
As a read magnetic layer, GdFeC of TMrich composition is used.
By using o, it becomes possible to reproduce a recording bit smaller than the conventional one, the recording density is remarkably improved, and the reproduction signal can be increased.

As the read magnetic layer, NdGdF is used.
By using eCo or Pt / Co artificial lattice film, the recording density is significantly improved and the reproduction signal is increased even when reproduction is performed using a laser having a short wavelength (400 nm to 600 nm). Is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a magneto-optical recording medium according to the present invention.

FIG. 2 is a diagram showing a configuration of another magneto-optical recording medium according to the present invention.

FIG. 3 is a diagram showing magnetic characteristics of a magneto-optical recording medium according to the present invention.

FIG. 4 is a diagram showing magnetic characteristics of a magneto-optical recording medium according to the present invention.

FIG. 5 is a diagram showing magnetic characteristics of a magneto-optical recording medium according to the present invention.

FIG. 6 is a diagram showing a configuration of a magneto-optical disk according to the present invention.

FIG. 7 is a diagram showing a structure of a magneto-optical recording medium described in Japanese Patent Laid-Open No. 5-81717.

[Explanation of symbols]

 1: read magnetic layer 2: intermediate magnetic layer 3: recording magnetic layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Ota 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Prefecture

Claims (6)

[Claims] 1. A read magnetic layer having a high Curie temperature and a low coercive force, which is in a perpendicular magnetization state, and a Curie temperature and a high coercivity which are relatively lower than those of the read magnetic layer, and a perpendicular magnetization state. In a magneto-optical recording medium comprising a recording magnetic layer and an intermediate magnetic layer which is provided between the read magnetic layer and the recording magnetic layer and has an in-plane magnetization state at room temperature and a perpendicular magnetization state when the temperature rises. The magneto-optical recording medium, wherein the read magnetic layer is a perpendicular magnetization film made of GdFeCo in which the sublattice magnetization of the transition metal is relatively larger than the sublattice magnetization of the rare earth metal. 2. A read magnetic layer having a high Curie temperature and a low coercive force, which is in a perpendicular magnetization state, and a Curie temperature and a high coercivity which are relatively lower than those of the read magnetic layer, and a perpendicular magnetization state. In a magneto-optical recording medium comprising a recording magnetic layer and an intermediate magnetic layer which is provided between the read magnetic layer and the recording magnetic layer and has an in-plane magnetization state at room temperature and a perpendicular magnetization state when the temperature rises. A magneto-optical recording medium, wherein the read magnetic layer is a perpendicular magnetization film of NdGdFeCo or a Pt / Co artificial lattice film. 3. A magneto-optical recording / reproducing apparatus which uses the magneto-optical recording medium according to claim 1 or 2, wherein the magneto-optical recording / reproducing apparatus reproduces while applying a magnetic field. 4. A read magnetic layer having a high Curie temperature and having an in-plane magnetization state, and a recording magnetic layer having a Curie temperature relatively lower than that of the read magnetic layer and having a perpendicular magnetization state. A magneto-optical recording medium comprising a layer and an intermediate magnetic layer which is provided between the read magnetic layer and the recording magnetic layer and which has an in-plane magnetization state at room temperature and a perpendicular magnetization state when the temperature rises. 5. The sublattice magnetization of the transition metal of the read magnetic layer is relatively larger than the sublattice magnetization of the rare earth metal.
The magneto-optical recording medium according to claim 4, which is an in-plane magnetized film made of FeCo. 6. The magneto-optical recording medium according to claim 4, wherein the read magnetic layer is an in-plane magnetized film of NdFeCo, NdGdFeCo, or a Pt / Co artificial lattice film.