JPH07130014A - Magneto-optical recording medium and magneto-optical recording method - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording medium capable of optical) modulated overwriting and having a large margin for recording power by forming a dielectric layer and a protective layer with a prescribed compsn. CONSTITUTION:A dielectric layer 2, a 1st magnetic layer 3, a 2nd magnetic layer 4 and a protective layer 5 are successively formed on a transparent substrate 1. The 1st magnetic layer 3 is made of a rare earth metal-transition metal alloy and has such characteristics that perpendicular magnetic anisotropy is predominant in the temp. range from room temp. to the Curie point. The 2nd magnetic layer 4 has a higher Curie point and lower coercive force at room temp. than the 1st magnetic layer 3. The dielectric layer 2 and the protective layer 5 are formed with AlN or AlSiN having <=15at.% Si content. The objective magneto-optical recording medium capable of optically modulated overwriting is obtd. The extent of intensity of laser light permitted to this recording medium is large even when a reflecting layer is not disposed on the protective layer 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the optical recording of information,
The present invention relates to a magneto-optical recording medium used for an optical disk, an optical card, and the like for performing at least one of reproduction and erasing, and a magneto-optical recording method for the same.

[0002]

2. Description of the Related Art The magneto-optical recording system is a system in which a perpendicularly magnetized film made of a magnetic material is formed on a substrate as a recording medium and recording and reproducing are carried out by the following method.

At the time of recording, the recording medium is first initialized by a strong external magnetic field or the like, and the direction of magnetization is aligned in one direction (upward or downward). After that, the area to be recorded is irradiated with a laser beam to heat the temperature of the area to a temperature near the Curie point or a temperature near the compensation point, thereby reducing the coercive force (Hc) to zero or almost zero. Then, an external magnetic field (bias magnetic field) opposite to the direction of magnetization at the time of initialization is applied to reverse the magnetization. When the irradiation of the laser beam is stopped, the recording medium returns to room temperature, and the reversed magnetization is fixed. That is, information is thermomagnetically recorded.

When reproducing, a linearly polarized laser beam is applied to the recording medium, and the phenomenon that the planes of polarization of the reflected light and the transmitted light rotate depending on the direction of magnetization (magnetic Kerr effect, magnetic Fade effect) The information is optically read out by utilizing it.

The magneto-optical recording method has been attracting attention as a rewritable large-capacity storage element, but in order to reuse (rewrite) the recording medium, one of the following methods must be adopted.

(A) Initialize by some method.

(B) The external magnetic field generator is devised to enable overwriting (rewriting that does not require erasing).

(C) Overwriting is made possible by devising the recording medium.

However, in the method (a), the initialization device,
Alternatively, two heads are required, resulting in high cost. Also, when trying to rewrite with one head,
It takes time because it is recorded after it is erased. In the method (b), head crash is a problem as in the case of magnetic recording.

Therefore, the method (c) is most effective. For example, Jpn. J. Appl. Phys. , Vo
l. 28 (1989) Suppl. 28-3, pp. Three
67-370, if the recording layer is an exchange coupling two-layer film,
It is described that an overwritable recording medium can be realized.

The overwrite procedure will be briefly described below. In the initialization, as shown in FIG. 14, by applying an initialization magnetic field (H _init ), the second
Only the magnetization of the magnetic layer 10 is aligned in one direction (downward in the figure). The initialization is always performed or only during recording. The coercive force H ₁ of the first magnetic layer 9 is H as shown in FIG.
Since it is larger than _init , the reversal of the magnetization of the first magnetic layer 9 does not occur.

Recording is performed by irradiating a high-level I and low-level II intensity-modulated laser beam while applying a recording magnetic field (H _w ).

When a high level I laser beam is irradiated,
The first magnetic layer 9 and the second magnetic layer 10 both have Curie points T ₁ ,
When the temperature is raised to a temperature T _H around T ₂ or higher and irradiated with a low level II laser beam, only the magnetic layer 9 is heated up to a temperature T _L around the Curie point T ₁ or higher. As such, the high level I and the low level II are set.

Therefore, when the high-level I laser beam is irradiated, the magnetization of the second magnetic layer 10 is inverted upward by H _w as shown in FIG. 14, and the magnetization of the first magnetic layer 9 is changed. The direction of the second magnetic layer 10 is matched with the exchange force acting on the interface during the cooling process. Therefore, the direction of the first magnetic layer 9 is upward.

On the other hand, when the laser light of low level II is irradiated, the magnetization of the second magnetic layer 10 is not reversed by H _w . The magnetization of the first magnetic layer 9 matches the direction of the second magnetic layer 10 due to the exchange force acting on the interface during the cooling process, as described above. Therefore, the orientation of the first magnetic layer 9 is
As shown in FIG. 14, it faces downward.

The above H _w is set to be considerably smaller than H _init . Also, the intensity of the laser light during playback is
It is set to a level much lower than the low level II used for recording. Furthermore, by providing an intermediate layer between the first magnetic layer 9 and the second magnetic layer 10 to form a three-layer structure,
・ Reducing the interfacial coupling force between the second magnetic layers 9 and 10
Improvements have been made to reduce _init .

Further, J. Mag. Soc. Jpn. , V
ol. 15, Supl. No. S1 (1991), 4
In 47, a SiN layer is provided on both sides of the recording layer for the purpose of protecting the recording layer (corresponding to the magnetic layers 9 and 10).

[0018]

However, when the SiN layers are provided on both sides of the recording layer, the recording power margin,
That is, the allowable range of the intensity of the laser light becomes small.
Therefore, there is a problem in that it is necessary to newly provide a reflective layer or the like made of Al or the like for expanding the recording power margin on the SiN layer on the side where the laser light does not enter.

[0019]

In order to solve the above-mentioned problems, the magneto-optical recording medium according to the invention of claim 1 has a dielectric layer and a rare earth metal-transition metal on a light-transmitting substrate. The first magnetic layer, which is made of an alloy and has a characteristic that perpendicular magnetic anisotropy is dominant from room temperature to the Curie point, and the rare earth metal-transition metal alloy, which has a higher Curie point than the first magnetic layer and has a room temperature. A second magnetic layer having a coercive force lower than that of the first magnetic layer and a protective layer are sequentially formed, and the dielectric layer and the protective layer each have an AlN or Si content of 15 at% or less. It is characterized by being made of any of AlSiN.

The magneto-optical recording medium according to the invention of claim 2 is
In order to solve the above problems, the magneto-optical recording medium according to claim 1, wherein an intermediate magnetic layer made of a rare earth metal-transition metal alloy is formed between the first magnetic layer and the second magnetic layer. In the above intermediate magnetic layer, the coercive force at room temperature is almost zero, the in-plane magnetic anisotropy and the perpendicular magnetic anisotropy are almost equal at room temperature, and the perpendicular magnetic anisotropy is superior at a predetermined temperature or higher. It is characterized by the following characteristics.

A magneto-optical recording medium according to the invention of claim 3 is
In order to solve the above problems, in the magneto-optical recording medium according to claim 2, a 0th magnetic layer made of a rare earth metal-transition metal alloy is formed between the dielectric layer and the first magnetic layer. The 0th magnetic layer has a higher Curie point than the first magnetic layer, has a coercive force of almost zero at room temperature, and exhibits in-plane magnetic anisotropy at room temperature. It is characterized in that it exhibits a characteristic in which the perpendicular magnetic anisotropy is dominant at a predetermined temperature or higher.

The magneto-optical recording medium according to the invention of claim 4 is
In order to solve the above problems, in the magneto-optical recording medium according to claim 2 or 3, the first magnetic layer has a Curie point of 10 or less.
Coercive force at room temperature of 0 to 250 ° C. is 5 kOe or more,
The intermediate magnetic layer has a temperature exhibiting perpendicular magnetic anisotropy of 80 ° C. or higher, the Curie point is the Curie point of the first magnetic layer or higher, and the second magnetic layer has a Curie point of 150 to 400 ° C. The coercive force at room temperature is 3 kOe or less.

A magneto-optical recording medium according to the invention of claim 5 is
In order to solve the above problems, in the magneto-optical recording medium according to claim 2 or 3, the composition of the first magnetic layer is set to be a transition metal rich or compensating composition at room temperature. The composition of the layer is rich in rare earth metal at room temperature and the compensation point is set to 100 to 250 ° C. The composition of the second magnetic layer is rich in rare earth metal at room temperature and the compensation point is intermediate magnetic. Higher than the compensation point of the layer, and 3
It is characterized in that it is set to be lower than 00 ° C.

A magneto-optical recording medium according to the invention of claim 6 is
In order to solve the above problems, the magneto-optical recording medium according to claim 2, wherein the first magnetic layer is DyFeC.
and the intermediate magnetic layer is made of GdFeCo.
The magnetic layer is characterized by being made of GdDyFeCo or DyFeCo.

The magneto-optical recording medium according to the invention of claim 7 is
In order to solve the above problems, a magneto-optical recording medium according to claim 2, 3, 4 or 5, the first magnetic layer Dy _a (F
e _b Co _1-b ) _1-a , and the intermediate magnetic layer is Gd _c (F
_ed Co _1-d ) _1-c , and the second magnetic layer is (Gd _e D
y _1-e ) _g (Fe _f Co _1-f ) _1-g , or Dy _h
(Fe _i Co _1-i ) _1-h , a, b, c, d,
e, f, g, h, and i are 0.18 ≦ a ≦ 0.25, 0.70 ≦ b ≦ 0.90, 0.26 ≦ c ≦ 0.3, respectively.
2, 0.50 ≦ d ≦ 0.90, 0.10 ≦ e ≦ 0.95, 0.30 ≦ f ≦
0.90, 0.28 ≤ g ≤ 0.33, 0.28 ≤ h ≤ 0.33, 0.30 ≤ i
The feature is that it is set to satisfy ≦ 0.80.

The magneto-optical recording medium according to the invention of claim 8 is
In order to solve the above-mentioned problems, claims 2, 3, 4, 5,
6 or 7, wherein the first magnetic layer has a thickness of 20 to 100 nm and the intermediate magnetic layer has a thickness of 5 to 50 n.
m, and the film thickness of the second magnetic layer is set to 20 to 200 nm.

A magneto-optical recording method according to the invention of claim 9
In order to solve the above-mentioned problems, a dielectric layer and a rare earth metal-transition metal alloy are formed on a substrate having translucency,
It is composed of a first magnetic layer showing a characteristic that perpendicular magnetic anisotropy is dominant from room temperature to the Curie point and a rare earth metal-transition metal alloy, which has a higher Curie point than the first magnetic layer and has a coercive force at room temperature. A second magnetic layer lower than the first magnetic layer and a protective layer are sequentially formed, and the dielectric layer and the protective layer each have an AlN or Si content of 15 at%.
After the magnetization of the second magnetic layer is initialized in the direction of the initializing magnetic field by applying a constant initializing magnetic field perpendicular to the layer surface to the magneto-optical recording medium made of any of the following AlSiN, and Is a magneto-optical recording method for recording information on a first magnetic layer by irradiating a high-level and low-level intensity-modulated laser beam. By raising the temperature to a temperature near the Curie point of the layer or higher and irradiating with a low level laser beam, the temperature of the first magnetic layer near the Curie point or higher and the second magnetic layer The feature is that the temperature is raised to a temperature lower than the Curie point of the layer.

[0028]

According to the structure of the first aspect, the optical modulation overwrite is possible, and the recording power margin is large without providing the reflection layer on the protective layer, that is, the allowable range of the intensity of the laser beam. A large magneto-optical recording medium can be realized.

According to the structure of claim 2, the coercive force at room temperature is substantially zero, the in-plane magnetic anisotropy and the perpendicular magnetic anisotropy are substantially equal at room temperature, and the perpendicular magnetic anisotropy is higher than a predetermined temperature. Since the intermediate magnetic layer exhibiting the property of superiority is provided between the first magnetic layer and the second magnetic layer, in addition to the function of claim 1, light modulation overwrite is possible and initialization is performed. The magnetic field can be reduced.

According to the structure of claim 3, the Curie point is higher than that of the first magnetic layer, the coercive force at room temperature is almost zero, and the in-plane magnetic anisotropy is dominant at room temperature. Shows,
Since the 0th magnetic layer exhibiting the characteristic that the perpendicular magnetic anisotropy is dominant at a predetermined temperature or higher is provided between the dielectric layer and the first magnetic layer, in addition to the function of claim 2, a smaller recording bit can be obtained. Can be reproduced.

That is, when the 0th magnetic layer is irradiated with the light beam during reproduction, the temperature distribution of the irradiated portion has a Gaussian distribution, so that the temperature of only the area near the center smaller than the diameter of the light beam. Rises.

As the temperature rises, the magnetization of the temperature rising portion changes from in-plane magnetization to perpendicular magnetization. At this time, the magnetization direction of the 0th magnetic layer follows the magnetization direction of the 1st magnetic layer due to the exchange coupling force between the two layers of the 0th magnetic layer and the 1st magnetic layer. When the temperature rising portion shifts from the in-plane magnetization to the perpendicular magnetization, only the temperature rising portion exhibits the polar Kerr effect, and the information is reproduced based on the reflected light from the portion.

Then, when the light beam moves to reproduce the next recorded bit, the temperature of the previous reproducing portion decreases and the perpendicular magnetization shifts to the in-plane magnetization, so that the polar Kerr effect is not exhibited. This means that the magnetization recorded in the first magnetic layer is masked by the in-plane magnetization of the 0th magnetic layer and cannot be read out. This eliminates signal mixing from adjacent bits, which causes noise and reduces reproduction resolution. As described above, since only the area having the temperature equal to or higher than the predetermined temperature is involved in the reproduction, it is possible to reproduce the recording bit smaller than the conventional one. This significantly improves the recording density.

According to the structure of claim 4, in addition to the function of claim 2 or 3, since the temperature at which the perpendicular magnetic anisotropy of the intermediate magnetic layer is 80 ° C. or more, the temperature at the time of recording is 80 ° C. or more. In that case, magnetic coupling between the first magnetic layer and the second magnetic layer occurs. Since the Curie point of the intermediate magnetic layer is equal to or higher than the Curie point of the first magnetic layer, the information recorded in the second magnetic layer is always transferred to the first magnetic layer. Further, since the coercive force of the second magnetic layer at room temperature is 3 kOe or less, the initializing magnetic field is 3 kOe.
e or less. Furthermore, the Curie point of the first magnetic layer is set to 10
0 to 250 ° C., Curie point of the second magnetic layer is 150 to 40
By setting the temperature to 0 ° C., recording can be performed with a laser power having no practical problem, and sufficient reproduction signal characteristics can be obtained.

According to the structure of claim 5, in addition to the effect of claim 2 or 3, since the second magnetic layer has a compensation point, the direction of magnetization dominated by the rare earth metal is exhibited from room temperature to the compensation point.
From the compensation point to the Curie point, the direction of magnetization dominated by the transition metal is shown. That is, since the direction of the magnetization recorded at a high temperature during recording is reversed at room temperature, it is possible to make the direction of the initialization magnetic field and the direction of the recording magnetic field the same. Furthermore, since the compensation point of the intermediate magnetic layer is lower than the compensation point of the second magnetic layer,
It is possible to use the leakage magnetic field of the intermediate magnetic layer during recording,
Light modulation overwrite becomes easy to perform. The compensation point of the second magnetic layer is 100 to 300 ° C., and the compensation point of the intermediate magnetic layer is 100.
By setting the temperature to ˜250 ° C., recording can be performed with a laser power having no practical problem.

According to the structure of claim 6, claims 2, 3,
In addition to the effect of 4 or 5, it becomes possible to determine the coercive force at room temperature and the direction of magnetization by the composition ratio of the rare earth metal.
The Curie point and the compensation point can be determined by the ratio of / Co.

According to the configuration of claim 7, claims 2, 3,
In addition to the effects of 4 or 5, by limiting the composition,
It becomes possible to perform recording with a proper laser power, an initializing magnetic field, and a recording magnetic field, and it is possible to secure the reproduction signal quality required for digital recording.

According to the structure of claim 8, 2, 3, 4,
In addition to the effect of 5, 6 or 7, by limiting the film thickness, it becomes possible to record with an appropriate laser power, initializing magnetic field and recording magnetic field, and the reproduction signal quality required for digital recording. Can be secured.

According to a ninth aspect of the invention, for the above magneto-optical recording medium, the operation of optical modulation overwrite, that is, the initialization operation of the second magnetic layer and the recording operation on the second magnetic layer at room temperature are performed. The transfer operation from the second magnetic layer to the first magnetic layer can be smoothly performed.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A first embodiment of the present invention will be described with reference to FIGS.
The explanation is based on the following.

As shown in FIG. 1, the magneto-optical recording medium of this embodiment has a transparent substrate 1 (base) and a transparent dielectric layer 2 and a magnetic layer 3 (first magnetic layer). ), The magnetic layer 4 (second magnetic layer), the protective layer 5, and the overcoat layer 6 are sequentially formed.

The magnetic layers 3 and 4 are made of a rare earth metal-transition metal alloy.

The magnetic layer 3 is, as shown in FIG.
Compared with the above, it has a low Curie point (T _C1 ) and a high coercive force (H _C1 ) at room temperature, and exhibits the characteristics that the perpendicular magnetic anisotropy is dominant from room temperature to T _C1 .

The magnetic layer 4 has a Curie point (T _C2 ) higher than T _C1 of the magnetic layer 3 and a coercive force (H _C2 ) lower than H _C1 of the magnetic layer 3 at room temperature. The characteristic that perpendicular magnetic anisotropy becomes dominant up to T _C2 , and the compensation point (T _comp2 )
Have.

When recording is performed in the above configuration, initialization is first performed. That is, as shown in FIG.
By applying an upward initialization magnetic field (H _init ),
Only the magnetization of the magnetic layer 4 is aligned in one direction. In FIG. 3, the sublattice magnetization of the transition metal in the so-called rare earth metal-rich magnetic layer 4, in which the sublattice magnetization of the rare earth metal is larger than that of the transition metal, is indicated by an arrow.

The above initialization is performed all the time or only during recording. Since H _{C1 of the} magnetic layer 3 is larger than H _{in it} ,
The reversal of the magnetization of the magnetic layer 3 does not occur.

[0047] recording, while applying substantially smaller H _init the same direction of the recording magnetic field (H _w) than H _init, as shown in FIG. 4, the intensity modulated laser beam to a high level I and low level II This is done by irradiating.

When irradiated with a high level I laser beam,
When both the magnetic layers 3 and 5 are heated to a temperature (T _H ) near or above T _C1 , T _C2 and irradiated with a low level II laser beam, only the magnetic layer 3 is at or near T _C1. The high level I and the low level II are set so as to raise the temperature to the above temperature ( _TL ).

Therefore, when the high-level I laser beam is irradiated, the magnetization of the magnetic layer 5 is reversed upward by H _w , and in the cooling process, the magnetization of the magnetic layer 4 is changed by the exchange force acting on the interface. By transferring the direction to the magnetic layer 3, the magnetization direction of the magnetic layer 3 and the magnetization direction of the magnetic layer 4 match. Therefore, the magnetic layer 3 faces upward.

On the other hand, when the low level II laser beam is irradiated, the magnetization of the magnetic layer 4 is not reversed by H _w . In the cooling process, the direction of magnetization of the magnetic layer 3 and the direction of magnetization of the magnetic layer 4 are transferred to each other by transferring the direction of the magnetic layer 4 to the magnetic layer 3 by the exchange force acting on the interface, as described above. Match. Therefore, the direction of the magnetic layer 3 is downward.

That is, overwriting is possible with the high-level I and low-level II laser beams.

When reproducing information, laser light of level III, which is much lower than that at the time of recording, is irradiated, and the rotation of the plane of polarization of the reflected light is detected.

A sample magneto-optical disk is shown below as an example of the magneto-optical recording medium.

In Sample # 1, the transparent substrate 1 is made of a disk-shaped glass having an outer diameter of 86 mm, an inner diameter of 15 mm and a thickness of 1.2 mm. An uneven guide track for guiding a light beam is directly formed on one surface of the substrate 1 by a reactive ion etching method. Track pitch is 1.
The width of the groove (recess) is 0.8 μm, and the width of the land (projection) is 0.8 μm.

On the surface of the substrate 1 on the guide track side, a dielectric layer 2 made of AlN having a film thickness of 70 nm by reactive sputtering and a magnetic layer made of DyFeCo having a film thickness of 50 nm by simultaneous sputtering of Dy, Fe and Co targets. 3 and a Gd, Dy, Fe, and Co target are simultaneously sputtered to form a 50 nm-thick GdDyFeCo film.
And a protective layer 5 made of AlN having a film thickness of 70 nm were laminated.

The sputtering conditions during the formation of the magnetic layers 3 and 4 were such that the ultimate vacuum was 2.0 × 10 ^-4 Pa or less, the Ar gas pressure was 6.5 × 10 ^-1 Pa, and the discharge power was 300 W. The sputtering conditions for forming the layer 2 and the protective layer 5 are as follows:
Ultimate vacuum 2.0 × 10 ^-4 Pa or less, N ₂ gas pressure 3.0
The discharge power is × 10 ⁻¹ Pa and the discharge power is 800 W.

Further, an acrylate-based UV curable resin was coated on the protective layer 5 and cured by UV irradiation to form an overcoat layer 6.

The magnetic layer 3 is composed of Dy _0.19 (Fe _0.86 C
o _0.14 ) _0.81 , transition metal rich, T _C1 = 170 ° C., H _C1 = 12 kOe at room temperature, and the magnetic layer 4 is (Gd _0.50).
Dy _0.50 ) _0.30 (Fe _0.72 Co _0.28 ) _0.70 , rare earth metal rich, T _C2 = 250 ° C., T _COMP2 = 210 ° C., and H _C2 = 1.5 kOe at room temperature.

For the magneto-optical disk of sample # 1,
Under the conditions of H _init = 2.5 kOe and H _w = 500 Oe, a recording bit having a length of 0.65 μm was recorded, and an unerased optical modulation overwrite was possible. These recording bits, under the conditions of reproduction laser power (P _R) = 1mW level III, was reproduced, good signal to noise ratio (C / N) was obtained.

FIG. 5 shows a combination of the high level I laser power and the low level II laser power when the C / N exceeds 45 dB. As is clear from the figure,
In the magneto-optical disk of the present embodiment using AlN for the dielectric layer 2 and the protective layer 5, the allowable range of laser power that can obtain C / N exceeding 45 dB is wide. That is, the recording power margin is large.

As a comparative example, S is used for the dielectric layer 2 and the protective layer 5.
FIG. 6 shows a combination of a high level I laser power and a low level II laser power when the C / N exceeds 45 dB in the conventional magneto-optical disk using iN.
Shown in. As is clear from the figure, in the conventional magneto-optical disk, the allowable range of the laser power at which C / N exceeding 45 dB is obtained is very narrow as compared with the magneto-optical disk of this embodiment. That is, the recording power margin is very narrow.

The next magneto-optical disk sample # 2 is the same as sample # 1 except for the dielectric layer 2 and the protective layer 5.

The dielectric layer 2 and the protective layer 5 of sample # 2 are
AlSi containing 15 at% Si with a film thickness of 70 nm
It was made of N and was formed by reactive sputtering.

When recording and reproducing were also performed on this sample # 2 under the above conditions, the same result as that of the sample # 1 was obtained. That is, a large recording power margin was obtained.

The second embodiment of the present invention will be described below with reference to FIGS. 7 and 8. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 7, the magneto-optical recording medium of this example is different from the above examples in that the magnetic layer 4 does not have a compensation point (T _{comp 2} ).

In the above structure, when recording information, as shown in FIG. 8, a recording magnetic field (H _w ) opposite to the initialization magnetic field (H _init ) is applied. Except for this point,
The initialization, recording, and reproduction methods are the same as those in the above embodiment.

A sample magneto-optical disk is shown below as an example of the magneto-optical recording medium.

The sample # 3 is the same as the sample # 1 of the above embodiment except for the magnetic layer 4.

The magnetic layer 4 of the sample # 3 has (Gd _0.50 D
y _0.50 ) _0.32 (Fe _0.68 Co _0.32 ) _0.68 , rare earth metal rich, T _C2 = 250 ° C., no T _COMP2 , H _C2 at room temperature
= 1.5 kOe.

When recording and reproducing were also performed on this sample # 3 under the same conditions as those of the above-mentioned embodiment, the same result as that of the sample # 1 was obtained. That is, the allowable range of the laser power that can obtain a C / N exceeding 45 dB is wide. In other words, the recording power margin is large.

The third embodiment of the present invention will be described below with reference to FIGS. 9 to 11. In addition,
For convenience of explanation, members having the same functions as the members shown in the drawings of the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The magneto-optical recording medium of this embodiment is different from that of the first embodiment in that a magnetic layer 7 (intermediate magnetic layer) is provided between the magnetic layers 3 and 4, as shown in FIG. Are different.

As shown in FIG. 10, the magnetic layer 7 has a characteristic that the Curie point (T _C3 ) higher than T _{C1 of the} magnetic layer 3 and the in-plane magnetic anisotropy and the perpendicular magnetic anisotropy are substantially equal at room temperature. Indicates
It has a coercive force (H _C3 ) of almost zero, and shows a characteristic that perpendicular magnetic anisotropy is dominant at a predetermined temperature or higher.
have _comp3 ).

In the above construction, the initialization, recording and reproduction methods are the same as in the first embodiment. However, since the magnetic layer 7 is provided, the initialization process and the recording process are different as described below.

When recording is performed, first, initialization is performed. That is, as shown in FIG. 11, by applying an upward initialization magnetic field (H _init ), only the magnetization of the magnetic layer 4 is aligned in one direction. In FIG. 11, the sublattice magnetization of the transition metal in the so-called rare earth metal-rich magnetic layer 4 in which the sublattice magnetization of the rare earth metal is larger than the sublattice magnetization of the transition metal is indicated by an arrow.

The above initialization is performed all the time or only during recording. Since H _{C1 of the} magnetic layer 3 is larger than H _{in it} and the magnetic layer 7 exhibits in-plane magnetic anisotropy, the magnetization direction of the magnetic layer 4 is not transferred to the magnetic layer 3 through the magnetic layer 7. The reversal of the magnetization of the magnetic layer 3 does not occur.

[0078] recording, while applying substantially smaller H _init the same direction of the recording magnetic field (H _w) than H _init, carried out by irradiating an intensity modulated laser beam to a high level I and low level II.

When a high level I laser beam is irradiated,
When both the magnetic layers 3 and 4 are heated to a temperature (T _H ) near or above T _C1 , T _C3 and irradiated with a low level II laser beam, only the magnetic layer 3 is at or near T _C1. The high level I and the low level II are set so as to raise the temperature to the above temperature ( _TL ).

Therefore, when the high-level I laser beam is irradiated, the magnetization of the magnetic layer 4 is reversed upward by H _w , and the magnetic layer 7 also exhibits perpendicular magnetic anisotropy during the cooling process. The direction of the magnetic layer 4 is transferred to the magnetic layer 7 by the exchange force acting on the interface, and the direction of magnetization of the magnetic layer 7 is further transferred to the magnetic layer 3, whereby the direction of the magnetic layer 3 and the direction of the magnetic layer 4 are transferred. Match. Therefore, the magnetic layer 3 faces upward.

On the other hand, when the low level II laser light is irradiated, the magnetization of the magnetic layer 4 is not reversed by H _w . In the cooling process, since the magnetic layer 7 exhibits perpendicular magnetic anisotropy, the direction of the magnetic layer 4 is transferred to the magnetic layer 7 by the exchange force acting on the interface, and the magnetization of the magnetic layer 7 is changed. By transferring the orientation to the magnetic layer 3,
And the direction of the magnetic layer 4 match. Therefore, the direction of the magnetic layer 3 is downward.

That is, overwriting is possible with the high-level I and low-level II laser beams.

When reproducing information, laser light of level III, which is much lower than that at the time of recording, is irradiated, and the rotation of the plane of polarization of the reflected light is detected.

A sample magneto-optical disk is shown below as an example of the magneto-optical recording medium.

The sample # 4 is the same as the sample # 1 of the first embodiment except for the magnetic layer 7.

The magnetic layer 7 is composed of Gd _0.28 (Fe _0.61 C
o _0.39 ) _0.72 , rare earth metal rich, T _C3 ≧ 300 ° C, T
_comp3 = 150 ° C, H _C3 at room temperature _~ 0 kOe, about 80 ° C
Indicates that the perpendicular magnetic anisotropy is dominant. Film thickness is 50
nm, and was formed on the magnetic layer 3 by co-sputtering of Gd, Fe, and Co targets.

Recording and reproduction were performed on this sample # 4 under the same conditions as in the above-mentioned embodiment.
Results similar to 1 were obtained. That is, the allowable range of the laser power that can obtain a C / N exceeding 45 dB is wide.
In other words, the recording power margin is large.

Next magneto-optical disk samples # 5 to # 1
1 is the same as sample # 4 except for the magnetic layer 7.

The magnetic layer 7 of Sample # 5 has a Gd _0.26 (F
e _0.80 Co _0.20 ) _0.74 , rare earth metal rich, T _C3 ≧ 30
0 ° C., T _COMP3 = 130 ° C., H _C3 ˜0 kOe at room temperature,
It exhibits perpendicular magnetic anisotropy at about 60 ° C.

The magnetic layer 4 of sample # 6 has a Gd _0.27 (F
e _0.80 Co _0.20 ) _0.73 , rare earth metal rich, T _C3 = 29
0 ° C, T _COMP3 = 140 ° C, H _C3 ~ 0 kOe at room temperature,
It exhibits perpendicular magnetic anisotropy at about 75 ° C.

The magnetic layer 4 of Sample # 7 has a Gd _0.27 (F
e _0.60 Co _0.40 ) _0.73 , rare earth metal rich, T _C3 ≧ 30
0 ° C, T _COMP3 = 140 ° C, H _C3 ~ 0 kOe at room temperature,
It exhibits perpendicular magnetic anisotropy at about 80 ° C.

The magnetic layer 4 of Sample # 8 has a Gd _0.28 (F
e _0.80 Co _0.20 ) _0.72 , rare earth metal rich, T _C3 = 28
0 ° C., T _COMP3 = 150 ° C., H _C3 ˜0 kOe at room temperature,
It exhibits perpendicular magnetic anisotropy at about 80 ° C.

The magnetic layer 4 of sample # 9 has a Gd _0.28 (F
e _0.90 Co _0.10 ) _0.72 , rare earth metal rich, T _C3 = 26
0 ° C., T _COMP3 = 150 ° C., H _C3 ˜0 kOe at room temperature,
It exhibits perpendicular magnetic anisotropy at about 80 ° C.

The magnetic layer 4 of sample # 10 is made of Gd
_0.28 (Fe _0.65 Co _0.35 ) _0.72 , rare earth metal rich, T
_C3 ≧ 300 ° C., T _COMP3 = 150 ° C., H _C3 ˜0 at room temperature
It exhibits perpendicular magnetic anisotropy at kOe and about 80 ° C.

The magnetic layer 4 of sample # 11 is made of Gd.
_0.29 (Fe _0.80 Co _0.20 ) _0.71 , Rare earth metal rich, T
_C3 = 280 ° C, T _COMP3 = 170 ° C, H _C3 ~ 0 at room temperature
It exhibits perpendicular magnetic anisotropy at kOe and about 120 ° C.

With respect to any of the above-mentioned samples # 5 to # 11, the light modulation overwrite without the unerased residue was possible.

Next magneto-optical disk samples # 12 to #
15 is the same as Sample # 4 except for the magnetic layer 3.

The magnetic layer 3 of the sample # 9 has Dy _0.21 (F
e _0.84 Co _0.16 ) _0.79 , transition metal rich, T _C1 = 170
H _C1 = 15 kOe at ℃ and room temperature.

The magnetic layer 3 of Sample # 10 was made of Dy.
_0.23 (Fe _0.84 Co _0.16 ) _0.77 , compensation composition, T _C1 = 15
H _C1 ≧ 20 kOe at 0 ° C. and room temperature.

The magnetic layer 3 of Sample # 11 was made of Dy.
_0.23 (Fe _0.80 Co _0.20 ) _0.77 , compensation composition, T _C1 = 16
H _C1 ≧ 20 kOe at 5 ° C. and room temperature.

The magnetic layer 3 of sample # 12 was made of Dy.
_0.19 (Fe _0.84 Co _0.16 ) _0.81 , transition metal rich, T _C1
= 200 ° C., H _C1 = 8 kOe at room temperature.

With respect to any of the above-mentioned samples # 12 to # 15, the light modulation overwrite without the unerased residue was possible.

Next magneto-optical disk samples # 16 to #
29 is the same as sample # 4 except for the magnetic layer 4.

The magnetic layer 4 of the sample # 16 has (Gd _0.50
Dy _0.50 ) _0.32 (Fe _0.70 Co _0.30 ) _0.69 , rare earth metal rich, T _C2 = 230 ° C., T _COMP2 = 220 ° C., and H _C2 = 1.2 kOe at room temperature.

The magnetic layer 4 of the sample # 17 has (Gd _0.50
Dy _0.50 ) _0.30 (Fe _0.70 Co _0.30 ) _0.70 , rare earth metal rich, T _C2 = 260 ° C., T _COMP2 = 210 ° C., and H _C2 = 1.4 kOe at room temperature.

The magnetic layer 4 of the sample # 18 has (Gd _0.50
Dy _0.50 ) _0.30 (Fe _0.80 Co _0.20 ) _0.70 , rare earth metal rich, T _C2 = 250 ° C., T _COMP2 = 210 ° C., and H _C2 = 1.2 kOe at room temperature.

The magnetic layer 4 of the sample # 19 has (Gd _0.50
Dy _0.50 ) _0.30 (Fe _0.60 Co _0.40 ) _0.70 , rare earth metal rich, T _C2 = 290 ° C., T _COMP2 = 210 ° C., and H _C2 = 1.2 kOe at room temperature.

The magnetic layer 4 of the sample # 20 has (Gd _0.50
Dy _0.50 ) _0.30 (Fe _0.55 Co _0.45 ) _0.70 , rare earth metal rich, T _C2 = 310 ° C., T _COMP2 = 210 ° C., and H _C2 = 1.0 kOe at room temperature.

The magnetic layer 4 of the sample # 21 has (Gd _0.60
Dy _0.40 ) _0.30 (Fe _0.80 Co _0.20 ) _0.70 , rare earth metal rich, T _C2 = 260 ° C., T _COMP2 = 210 ° C., and H _C2 = 1.2 kOe at room temperature.

The magnetic layer 4 of the sample # 22 has (Gd _0.70
Dy _0.30 ) _0.30 (Fe _0.80 Co _0.20 ) _0.70 , rare earth metal rich, T _C2 = 280 ° C., T _COMP2 = 210 ° C., and H _C2 = 1.0 kOe at room temperature.

The magnetic layer 4 of the sample # 23 has (Gd _0.80
Dy _0.20 ) _0.30 (Fe _0.80 Co _0.20 ) _0.70 , rare earth metal rich, T _C2 = 300 ° C., T _COMP2 = 210 ° C., and H _C2 = 0.8 kOe at room temperature.

The magnetic layer 4 of the sample # 24 has (Gd _0.85
Dy _0.15 ) _0.30 (Fe _0.80 Co _0.20 ) _0.70 , rare earth metal rich, T _C2 = 310 ° C., T _COMP2 = 220 ° C., and H _C2 = 0.5 kOe at room temperature.

The magnetic layer 4 of the sample # 25 has (Gd _0.60
Dy _0.40 ) _0.31 (Fe _0.70 Co _0.30 ) _0.69 , rare earth metal rich, T _C2 = 290 ° C., T _COMP2 = 230 ° C., and H _C2 = 1.2 kOe at room temperature.

The magnetic layer 4 of Sample # 26 was made of Dy.
_0.28 (Fe _0.70 Co _0.30 ) _0.72 , rare earth metal rich, T
_C2 = 200 ° C, T _COMP2 = 180 ° C, H _C2 at room temperature =
It is 2.2 kOe.

The magnetic layer 4 of sample # 27 was made of Dy.
_0.28 (Fe _0.60 Co _0.40 ) _0.72 , rare earth metal rich, T
_C2 = 230 ° C, T _COMP2 = 185 ° C, H _C2 at room temperature =
It is 2.3 kOe.

The magnetic layer 4 of the sample # 28 is Dy.
_0.29 (Fe _0.50 Co _0.50 ) _0.69 , rare earth metal rich, T
_C2 = 250 ° C, T _COMP2 = 190 ° C, H _C2 at room temperature =
It is 2.0 kOe.

The magnetic layer 4 of Sample # 29 was made of Dy.
_0.30 (Fe _0.50 Co _0.50 ) _0.70 , rare earth metal rich, T
_C2 = 250 ° C, T _COMP2 = 190 ° C, H _C2 at room temperature =
It is 1.8 kOe.

With respect to any of the above samples # 16 to # 29, the light modulation overwrite without the unerased residue was possible.

The next sample # 30 of the magneto-optical disk is
It is the same as Sample # 4 except that the thickness of the magnetic layer 5 is 30 nm.

With respect to the sample # 30 as well, the light modulation overwrite without erasure remained was possible. In addition, the magnetic layer 5
Since the film thickness of was less than 50 nm of the magnetic layer 5 of the sample # 1, sufficient recording was possible even when the duty of the recording pulse was 40%. Considering that the duty of the recording pulse of sample # 4 was 60%, sample # 4
The recording sensitivity was improved as compared with 4.

For samples # 4 to # 30, the first
When recording / reproducing was performed under the same conditions as in the example, the same result as that of sample # 1 was obtained. That is, 45d
The allowable range of laser power that can obtain C / N exceeding B is wide. In other words, the recording power margin is large.

The fourth embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

The magneto-optical recording medium of this example is different from that of the previous example in that a magnetic layer 8 (0th magnetic layer) was provided between the dielectric layer 2 and the magnetic layer 3 as shown in FIG. Is different.

The above-mentioned magnetic layer 8 has a higher Curie point (T _C0 ) than the magnetic layer 3, has a coercive force (H _C0 ) at room temperature of almost zero, and exhibits in-plane magnetic anisotropy at room temperature. And shows perpendicular magnetic anisotropy at a predetermined temperature or higher.

With the above structure, at the time of recording, the light modulation overwrite can be performed as in the above-described embodiment. Moreover, it is possible to reproduce a recording bit smaller than before.

That is, when the magnetic layer 8 is irradiated with the light beam during reproduction, the temperature distribution of the irradiated portion is almost Gaussian, so that the temperature of only the central region smaller than the diameter of the light beam is reduced. To rise.

As the temperature rises, the magnetization of the temperature rise portion shifts from in-plane magnetization to perpendicular magnetization. At this time, the magnetization direction of the magnetic layer 8 follows the magnetization direction of the magnetic layer 3 due to the exchange coupling force between the two layers of the magnetic layer 8 and the magnetic layer 3. When the temperature rising portion shifts from the in-plane magnetization to the perpendicular magnetization, only the temperature rising portion exhibits the polar Kerr effect, and the information is reproduced based on the reflected light from the portion.

Then, when the light beam moves to reproduce the next recording bit, the temperature of the previous reproducing portion is lowered and the perpendicular magnetization is changed to the in-plane magnetization, so that the polar Kerr effect is not exhibited. This means that the magnetization recorded in the magnetic layer 3 is masked by the in-plane magnetization of the magnetic layer 8 and cannot be read out. This eliminates signal mixing from adjacent bits, which causes noise and reduces reproduction resolution. As described above, since only the area having a temperature equal to or higher than the predetermined temperature is involved in the reproduction, it is possible to reproduce the recording bit smaller than the conventional one, and the recording density is remarkably improved.

A sample magneto-optical disk is shown below as an example of the magneto-optical recording medium.

The sample # 31 of the magneto-optical disk has the magnetic layer 8 having a film thickness of 50 nm between the dielectric layer 2 and the magnetic layer 3 of the sample # 4. It was manufactured by the same manufacturing method as the manufacturing method of 4.

The magnetic layer 8 of the sample # 31 is Gd
_0.25 (Fe _0.80 Co _0.20 ) _0.75 , rare earth metal rich, T
_C0 = 300 ° C, no compensation point, H _{C0 to 0} kOe at room temperature,
It exhibits perpendicular magnetic anisotropy at about 100 ° C.

Also for the sample # 31, the first
When recording / reproducing was performed under the same conditions as in the example, good results were obtained even with sample # 1. That is, the permissible range of the laser power for obtaining C / N exceeding 47 dB in the sample # 31 is almost the same as the permissible range of laser power for obtaining the C / N exceeding 45 dB in the sample # 1. In other words, the recording power margin of sample # 31 is larger than that of sample # 1.

Considering that the C / N of sample # 4 exceeds 45 dB, the signal quality of sample # 31 is improved over that of sample # 4. It is considered that this is because the Kerr rotation angle increased because T _C0 > T _C1 was set.

Further, when the recording bit length became shorter, the C / N sharply decreased in sample # 4.
C / N did not decrease so much. This is the magnetic layer 8
Shows in-plane magnetic anisotropy at room temperature, and shows perpendicular magnetic anisotropy when irradiated with laser light of level III reproducing laser power. It is thought that it can be played back without receiving.

In the above first to fourth examples, glass was used as the substrate 1 of Samples # 1 to # 31, but other than this, chemically strengthened glass, and ultraviolet curing on these glass substrates. The so-called 2P-layered glass substrate on which the mold resin layer is formed, polycarbonate (PC), polymethylmethacrylate (PMMA), amorphous polyolefin (APO), polystyrene (PS), polychlorinated biphenyl (PVC), epoxy, etc. It is possible to use.

AlN and AlSiN of the transparent dielectric layer 2
The film thickness of is not limited to 80 nm.

The film thickness of the transparent dielectric layer 2 increases the polar Kerr rotation angle from the magnetic layer 3 or the magnetic layer 8 by utilizing the light interference effect when reproducing the magneto-optical disk, so-called Kerr effect enhancement. It is decided in consideration of. In order to maximize the C / N during reproduction, it is necessary to increase the polar Kerr rotation angle. Therefore, the film thickness of the transparent dielectric layer 2 is set so that the polar Kerr rotation angle is the largest. To be done.

This film thickness changes depending on the wavelength of reproducing light and the refractive index of the transparent dielectric layer 2. In the case of this embodiment, AlN
Has a refractive index of 2.0, the reproduction light wavelength is 780 nm.
In this case, if the film thickness of AlN and AlSiN of the transparent dielectric layer 2 is set to about 30 to 120 nm, the Kerr effect enhancement effect becomes large. In addition, preferably, the film thickness of AlN and AlSiN of the transparent dielectric layer 2 is 70 to 100 nm.
In this range, the polar Kerr rotation angle becomes almost maximum.

When the wavelength of the reproduction light is 400 nm,
Half the film thickness of the transparent dielectric layer 2 (= 400/780)
You can do this. Further, when the refractive index of the transparent dielectric layer 2 is different from the above due to the difference in material or the manufacturing method, the value obtained by multiplying the refractive index and the film thickness (optical path length) becomes the same,
The film thickness of the transparent dielectric layer 2 may be set.

As can be seen from the above description, the larger the refractive index of the transparent dielectric layer 2, the smaller the film thickness.
Also, the greater the refractive index, the greater the enhancement effect of the polar Kerr rotation angle.

AlN and AlSiN have different refractive indexes by changing the ratio of Ar to N ₂ which is a sputtering gas during sputtering, the gas pressure, etc.
It is a material having a relatively large refractive index of about 8 to 2.1 and is suitable as a material for the transparent dielectric layer 2.

In addition to the Kerr effect enhancement described above, the transparent dielectric layer 2 together with the protective layer 6 has magnetic layers 3, 4 or magnetic layers 3, 7, 4 or magnetic layer 8,
It has a role of preventing oxidation of the rare earth-transition metal alloy magnetic layers 3, 7, and 4.

The magnetic film made of a rare earth transition metal is very likely to be oxidized, and the rare earth is particularly likely to be oxidized. For this reason, if the invasion of oxygen and moisture from the outside is not prevented as much as possible, the characteristics will be significantly deteriorated by oxidation.

Therefore, in Samples # 1 to # 31, the magnetic layers 3, 4 or the magnetic layers 3, 7, 4 or
Both sides of the magnetic layers 8, 3, 7, 4 are sandwiched by AlN and AlSiN. AlN and AlSiN are
It is a nitride film that does not contain oxygen as its component, and is a material with excellent moisture resistance.

Further, AlN and AlSiN are respectively A
reactive DC by introducing an N ₂ gas or a mixed gas of Ar and N ₂ using an Al target or an AlSi target.
(DC current) Sputtering is possible,
It is also advantageous in that the film formation rate is higher than that of RF (radio frequency) sputtering.

Composition of DyFeCo of magnetic layer 3, magnetic layer 7
The GdFeCo composition and the GdDyFeCo composition of the magnetic layer 4 are not limited to the above compositions. As materials for the magnetic layers 3, 7, and 4, Gd, Tb, Dy, Ho,
At least one rare earth metal selected from Nd, and F
The same effect can be obtained by using an alloy composed of at least one transition metal selected from e and Co.

Cr, V, Nb, Mn and B are added to the above materials.
at least one of e, Ni, Ti, Pt, Rh, and Cu
Addition of different kinds of elements improves the environmental resistance of the magnetic layers 3, 7, 4 themselves. That is, the magnetic layer 3 due to oxygen intrusion,
It is possible to provide a magneto-optical disk having excellent long-term reliability with less deterioration of characteristics due to oxidation of Nos. 7 and 4.

The film thickness of the magnetic layers 3, 7 and 4 is
It is determined in consideration of the materials, compositions, and film thicknesses of Nos. 7 and 4. The thickness of the magnetic layer 3 is 20 nm or more, more preferably 30 nm or more, and if it is too thick, information of the magnetic layer 7 will not be transferred, so 100 nm or less is preferable. The film thickness of the magnetic layer 7 is 20 nm or more, more preferably 10 to 50 nm, and if it is too thick, the recording sensitivity decreases, so 200 nm or less is preferable. The thickness of the magnetic layer 4 is 5 nm or more, more preferably 10 to 50 nm, and if it is too thick, information of the magnetic layer 7 will not be transferred, so 100 nm or less is preferable.

When T _{C1 of the} magnetic layer 3 is lower than 100 ° C., C / N is lower than 45 dB which is the minimum required for digital recording / reproducing. Further, when T _C1 exceeds 250 ° C., the recording sensitivity becomes poor. Therefore, T of the magnetic layer 3
_C1 is suitably 100 to 250 ° C. Furthermore, the magnetic layer 3
If H _C1 at room temperature is less than 5 kOe, H _init may partially initialize. Therefore, H _C1 of the magnetic layer 3 at room temperature is preferably 5 kOe or more.

The temperature showing the perpendicular magnetic anisotropy of the magnetic layer 7 is 8
When the temperature is lower than 0 ° C., the magnetic layer 4 has a temperature between room temperature and a temperature when the laser beam of P _R (reproduction power) is irradiated.
From the magnetic layer 7 to the magnetic layer 7 and from the magnetic layer 7 to the magnetic layer 3. Therefore, not only the magnetic layer 4 but also the magnetic layer 3 is initialized by H _init , and recording cannot be performed. Therefore, the temperature at which the magnetic layer 7 exhibits perpendicular magnetic anisotropy is appropriately 80 ° C. or higher.

Further, T _{C3 of the} magnetic layer 7 is T _{C1 of the} magnetic layer 3.
If it is less than 1, the transfer of magnetization is not performed well during light modulation overwriting. Therefore, T _{C3 of the} magnetic layer 7 is suitably T _C1 or more.

When T _{C2 of the} magnetic layer 4 is less than 150 ° C., P
_{Since the difference between L} (low level II laser power) and P _R (reproduction power, that is, level III laser power) becomes small, optical modulation overwrite cannot be performed well. Further, when T _C2 exceeds 400 ° C., the recording sensitivity becomes poor. Therefore, T _{C2 of the} magnetic layer 4 is 150 to 400.
℃ is suitable. Furthermore, the H _C3 of the magnetic layer 7 at room temperature is 3
If it exceeds kOe, the H _init generator becomes large,
Not preferable. Therefore, H _C2 of the magnetic layer 4 at room temperature is 3
A value of kOe or less is suitable.

Further, when T _{COMP3 of the} magnetic layer 7 is lower than T _{COMP2 of the} magnetic layer 4, the margin of the intensity of the high-level I laser beam and the margin of the intensity of the low-level II laser beam become large, and further cooling is performed. Information in the magnetic layer 4 is transferred to the magnetic layer 7 in the process, and the static magnetic force of the magnetic layer 4 can be utilized when transferred to the magnetic layer 3, which is preferable.

The film thickness of AlN of the protective layer 5 is set to 80 nm in this embodiment, but it is not limited to this. The thickness of the protective layer 5 is preferably 1 to 200 nm.

In this embodiment, the magnetic layers 3, 4 or the magnetic layers 3, 7, 4 or the magnetic layers 8, 3, 7, 4 are used.
The total thickness is 100 nm or more. At this thickness, the light incident from the optical pickup hardly passes through the magnetic layer. Therefore, the film thickness of the protective layer 5 is not particularly limited as long as it is necessary to prevent oxidation of the magnetic layer for a long period of time. If the material has a low antioxidation ability, the film thickness may be increased, and if it is high, the film thickness may be decreased.

The thermal conductivity of the protective layer 5 together with the transparent dielectric layer 2 affects the recording sensitivity characteristics of the magneto-optical disk. The recording sensitivity characteristic means how much laser power is required for recording or erasing. Most of the light incident on the magneto-optical disk is the transparent dielectric layer 2
And is absorbed by the magnetic layers 3, 4 or the magnetic layers 3, 7, 4 or the magnetic layers 8, 3, 7, 4 which are absorption films, and is converted into heat. At this time, the heat of the magnetic layers 3, 4 or the magnetic layers 3, 7, 4 or the magnetic layers 8, 3, 7, 4 is transferred to the transparent dielectric layer 2 and the protective layer 5 by heat conduction. Therefore, the thermal conductivity and heat capacity (specific heat) of the transparent dielectric layer 2 and the protective layer 5 affect the recording sensitivity.

This means that the recording sensitivity of the magneto-optical disk can be controlled to some extent by the film thickness of the protective layer 5. For example, for the purpose of increasing the recording sensitivity (recording and erasing can be performed with low laser power). The protective layer 5 may be thinned. Usually, in order to extend the life of the laser, it is advantageous that the recording sensitivity is high to some extent, and the thickness of the protective layer 5 is preferably thin.

AlN and AlSiN are suitable also in this sense, and since they are excellent in moisture resistance, when they are used as the protective layer 5,
It is possible to provide a magneto-optical disk having a high recording sensitivity because the film thickness can be reduced.

In this embodiment, the protective layer 5 is replaced by the transparent derivative layer 2
By using the same AlN and AlSiN as described above, a magneto-optical disk having excellent moisture resistance can be provided, and by forming the protective layer 5 and the transparent dielectric layer 2 with the same material, productivity can be improved.

The magneto-optical disks of Samples # 1 to # 31 are generally called single-sided type. Transparent dielectric layer 2,
When the thin film portions of the magnetic layers 3, 4 or the magnetic layers 3, 7, 4 or the magnetic layers 8, 3, 7, 4 and the protective layer 5 are collectively referred to as a recording medium layer, a single-sided type magneto-optical disk is The substrate 1, the recording medium layer, and the overcoat layer 6 are formed.

On the other hand, a magneto-optical disk in which two recording medium layers are formed on the substrate 1 and adhered by an adhesive layer so that the recording medium layers face each other is called a double-sided type.

The material of the adhesive layer is particularly preferably a polyurethane acrylate adhesive. This adhesive is a combination of UV, heat and anaerobic curing functions.
It has the advantage that the curing of the shadow of the recording medium layer that does not transmit ultraviolet rays is cured by heat and anaerobic curing function, and it has extremely high moisture resistance and is extremely superior in long-term stability. A magneto-optical disk can be provided.

Since the single-sided type requires only half the thickness of the magneto-optical disk as compared with the double-sided type, it is advantageous for a recording / reproducing apparatus which requires miniaturization.

Since the double-sided type is capable of double-sided reproduction, it is advantageous for a recording / reproducing apparatus which requires a large capacity, for example.

In the above embodiments, the magneto-optical disk was used as an example of the magneto-optical recording medium, but the present invention can be applied to a magneto-optical tape and a magneto-optical card.

The magneto-optical disk according to the invention of claim 1 comprises a dielectric layer 2 and a rare earth metal-transition metal alloy on a transparent substrate 1, and has a perpendicular magnetic anisotropy from room temperature to the Curie point. And a magnetic layer 4 composed of a rare earth metal-transition metal alloy, having a Curie point higher than that of the magnetic layer 3, and having a coercive force at room temperature lower than that of the magnetic layer 3. The protective layer 5 is sequentially formed, and the dielectric layer 2 and the protective layer 5 are each made of AlN or AlSiN having a Si content of 15 at% or less.

According to this, light modulation overwriting is possible, and even if the reflection layer is not provided on the protective layer 5,
It is possible to realize a magneto-optical disk having a large recording power margin, that is, a large allowable range of laser light intensity.

A magneto-optical disk according to a second aspect of the present invention is the magneto-optical disk according to the first aspect, in which a magnetic layer 7 made of a rare earth metal-transition metal alloy is provided between the magnetic layers 3 and 4. The magnetic layer 7 has a coercive force of almost zero at room temperature, has substantially the same in-plane magnetic anisotropy and perpendicular magnetic anisotropy at room temperature, and has a perpendicular magnetic anisotropy at a predetermined temperature or higher. This is a configuration showing a characteristic in which the property is superior.

According to this, the coercive force at room temperature is almost zero, the in-plane magnetic anisotropy and the perpendicular magnetic anisotropy are substantially equal at room temperature, and the perpendicular magnetic anisotropy becomes dominant at a predetermined temperature or higher. Since the magnetic layer 7 exhibiting the characteristics is provided between the magnetic layer 3 and the magnetic layer 4, in addition to the effect of the first aspect, optical modulation overwrite is possible and the initializing magnetic field can be reduced.

The magneto-optical disk according to the invention of claim 3 is the magneto-optical disk of claim 2, wherein a magnetic layer made of a rare earth metal-transition metal alloy is provided between the dielectric layer 2 and the magnetic layer 3. 8 is formed, the above-mentioned magnetic layer 8 has a higher Curie point than the magnetic layer 3, has a coercive force of almost zero at room temperature, and has in-plane magnetic anisotropy dominant at room temperature. That is, the configuration is such that the perpendicular magnetic anisotropy becomes dominant at a predetermined temperature or higher.

According to this, the Curie point is higher than that of the magnetic layer 3, the coercive force at room temperature is almost zero, and the in-plane magnetic anisotropy is dominant at room temperature, which is higher than the predetermined temperature. And the magnetic layer 8 showing the characteristics in which the perpendicular magnetic anisotropy is dominant,
Since it is provided between the dielectric layer 2 and the magnetic layer 3, in addition to the effect of the second aspect, it is possible to reproduce a smaller recording bit.

That is, when the magnetic layer 8 is irradiated with the light beam during reproduction, the temperature distribution of the irradiated portion is almost a Gaussian distribution, so that the temperature of only the central region smaller than the diameter of the light beam is reduced. To rise.

Along with this temperature rise, the magnetization of the temperature rise portion shifts from in-plane magnetization to perpendicular magnetization. At this time, the magnetization direction of the magnetic layer 8 follows the magnetization direction of the magnetic layer 3 due to the exchange coupling force between the two layers of the magnetic layer 8 and the magnetic layer 3. When the temperature rising portion shifts from the in-plane magnetization to the perpendicular magnetization, only the temperature rising portion exhibits the polar Kerr effect, and the information is reproduced based on the reflected light from the portion.

Then, when the light beam moves to reproduce the next recording bit, the temperature of the previous reproducing portion decreases and the perpendicular magnetization shifts to the in-plane magnetization, so that the polar Kerr effect is not exhibited. This means that the magnetization recorded in the magnetic layer 3 is masked by the in-plane magnetization of the magnetic layer 8 and cannot be read out. This eliminates signal mixing from adjacent bits, which causes noise and reduces reproduction resolution. As described above, since only the area having the temperature equal to or higher than the predetermined temperature is involved in the reproduction, it is possible to reproduce the recording bit smaller than the conventional one. This significantly improves the recording density.

The magneto-optical disk according to the invention of claim 4 is the magneto-optical disk of claim 2 or 3, wherein the magnetic layer 3 has a Curie point of 100 to 250 ° C. and a coercive force of 5 kOe or more at room temperature. The magnetic layer 7 has a temperature at which the perpendicular magnetic anisotropy is 80 ° C. or higher and the Curie point is the magnetic layer 3.
And the Curie point of the magnetic layer 4 is 1 or more.
The temperature is 50 to 400 ° C., and the coercive force at room temperature is 3 kOe or less.

According to this, in addition to the effect of the second or third aspect, the temperature at which the perpendicular magnetic anisotropy of the magnetic layer 7 is 80 is obtained.
Since the temperature is not lower than 0 ° C, if the recording temperature is not lower than 80 ° C, magnetic coupling between the magnetic layers 3 and 4 occurs. Since the Curie point of the magnetic layer 7 is equal to or higher than the Curie point of the magnetic layer 3, the information recorded in the magnetic layer 4 is surely transferred to the magnetic layer 3.
Furthermore, since the coercive force of the magnetic layer 4 at room temperature is 3 kOe or less, the initializing magnetic field is 3 kOe or less. Further, by setting the Curie point of the magnetic layer 3 to 100 to 250 ° C. and the Curie point of the magnetic layer 4 to 150 to 400 ° C., it becomes possible to record with a laser power that is practically no problem, and sufficient reproduction signal characteristics can be obtained. can get.

The magneto-optical disk according to the invention of claim 5 is the magneto-optical disk of claim 2 or 3, wherein the composition of the magnetic layer 3 is set to be a transition metal rich or compensating composition at room temperature. The composition of the magnetic layer 7 is rich in rare earth metals at room temperature and the compensation point is 100 to 250 ° C.
The composition of the magnetic layer 4 is such that it is rich in rare earth metals at room temperature and the compensation point is higher than the compensation point of the magnetic layer 7 and lower than 300 ° C. Is.

According to this, in addition to the effect of claim 2 or 3, since the magnetic layer 4 has a compensation point, the direction of magnetization dominated by the rare earth metal is shown from room temperature to the compensation point, and the Curie point is obtained from the compensation point. Indicates the direction of magnetization dominated by the transition metal.
That is, since the direction of the magnetization recorded at a high temperature during recording is reversed at room temperature, it is possible to make the direction of the initialization magnetic field and the direction of the recording magnetic field the same. Furthermore, since the compensation point of the magnetic layer 7 is lower than the compensation point of the magnetic layer 4, the leakage magnetic field of the magnetic layer 7 can be utilized during recording, and the light modulation overwrite becomes easy. Set the compensation point of the magnetic layer 4 to 100 to 3
By setting the temperature of 00 ° C. and the compensation point of the magnetic layer 7 to 100 to 250 ° C., recording can be performed with a laser power that is practically no problem.

The magneto-optical disk according to the invention of claim 6 is the magneto-optical disk according to claim 2, 3, 4 or 5, wherein the magnetic layer 3 is made of DyFeCo and the magnetic layer 7 is made of Gd.
The magnetic layer 4 is made of FeCo and is made of GdDyFeCo or DyFeCo.

According to this, claim 2, 3, 4 or 5
In addition to the effect of the above, it becomes possible to determine the coercive force at room temperature and the direction of magnetization by the composition ratio of the rare earth metal.
It is possible to determine the Curie point and the compensation point by the ratio of o.

A magneto-optical disk according to the invention of claim 7 is the magneto-optical disk according to claim 2, 3, 4 or 5, wherein the magnetic layer 3 is Dy _a (Fe _b Co _1-b ) _1-a. The magnetic layer 7 is made of Gd _c (Fe _d Co _1-d ) _1-c , and the magnetic layer 4 is made of (Gd _e Dy _1-e ) _g (Fe _f C
o _1-f ) _1-g , or Dy _h (Fe _i Co _1-i )
_1-h , a, b, c, d, e, f, g, h, i
Are 0.18 ≦ a ≦ 0.25, 0.70 ≦ b ≦ 0.90, 0.26 ≦ c ≦ 0.3, respectively.
2, 0.50 ≦ d ≦ 0.90, 0.10 ≦ e ≦ 0.95, 0.30 ≦ f ≦
0.90, 0.28 ≤ g ≤ 0.33, 0.28 ≤ h ≤ 0.33, 0.30 ≤ i
The configuration is set so as to satisfy ≦ 0.80.

According to this, claim 2, 3, 4 or 5
In addition to the effects of the above, by limiting the composition, it becomes possible to record with an appropriate laser power, initializing magnetic field, and recording magnetic field, and it is possible to secure the reproduction signal quality required for digital recording. It will be possible.

The magneto-optical disk according to the invention of claim 8 is the magneto-optical disk according to claim 2, 3, 4, 5, 6 or 7, wherein the magnetic layer 3 has a film thickness of 20 to 100 nm. 7 has a film thickness of 5 to 50 nm, and the magnetic layer 4 has a film thickness of 20 to 2
The configuration is set to 00 nm.

According to this, claims 12, 3, 4, 5,
In addition to the action effect of 6 or 7, by limiting the film thickness, it becomes possible to record with an appropriate laser power, an initializing magnetic field, and a recording magnetic field, and the reproduction signal quality required for digital recording can be obtained. It becomes possible to secure.

The magneto-optical recording method according to the invention of claim 9 comprises a dielectric layer 2 and a rare earth metal-transition metal alloy on a substrate 1 having a light-transmitting property, and has a perpendicular magnetic field from room temperature to the Curie point. A magnetic layer 3 having a property of being dominant in directionality, and a magnetic layer 4 made of a rare earth metal-transition metal alloy, having a higher Curie point than the magnetic layer 3, and having a coercive force lower than that of the magnetic layer 3 at room temperature. , A protective layer 5 are sequentially formed, and the dielectric layer 2 and the protective layer 5 are formed on the surface of the magneto-optical disk made of either AlN or AlSiN having a Si content of 15 at% or less. After the magnetization of the magnetic layer 4 is initialized in the direction of the initializing magnetic field by applying a constant initializing magnetic field perpendicular to, the laser beam whose intensity is modulated to a high level and a low level according to information is irradiated. As a result, the magnetic layer 3 A method of recording a magnetic field, which comprises irradiating a high-level laser beam to raise the temperature to a temperature in the vicinity of the Curie point of the magnetic layer 4 or higher, and irradiate a low-level laser beam. Thus, the temperature is raised to a temperature near the Curie point of the magnetic layer 3 or higher, and to a temperature lower than the Curie point of the magnetic layer 4.

According to this, for the above-described magneto-optical disk, the operation of optical modulation overwrite, that is, the initialization operation of the second magnetic layer at room temperature, the recording operation to the second magnetic layer, the second magnetic layer is performed. The transfer operation from the first magnetic layer to the first magnetic layer can be smoothly performed.

[0187]

As described above, the magneto-optical recording medium according to the present invention comprises a dielectric layer and a rare earth metal-transition metal alloy on a light-transmitting substrate and has a Curie point from room temperature. First, showing the characteristic that perpendicular magnetic anisotropy is dominant
A magnetic layer, a second magnetic layer made of a rare earth metal-transition metal alloy, having a Curie point higher than that of the first magnetic layer, and having a coercive force at room temperature lower than that of the first magnetic layer, and a protective layer are sequentially formed. The above-mentioned dielectric layer and protective layer are respectively
AlN or AlSi with Si content of 15 at% or less
Since any one of N is used, optical modulation overwrite is possible, and even if a reflective layer is not provided on the protective layer, the recording power margin is large, that is, the allowable range of the intensity of laser light is large. This has the effect of realizing a recording medium.

The magneto-optical recording medium according to the invention of claim 2 is
As described above, in the magneto-optical recording medium according to claim 1, the intermediate magnetic layer made of a rare earth metal-transition metal alloy is formed between the first magnetic layer and the second magnetic layer. The intermediate magnetic layer has a property that the coercive force at room temperature is almost zero, the in-plane magnetic anisotropy and the perpendicular magnetic anisotropy are substantially equal at room temperature, and the perpendicular magnetic anisotropy becomes dominant at a predetermined temperature or higher. Therefore, in addition to the effect of the first aspect, there is an effect that the light modulation overwrite is possible and the initialization magnetic field can be made small.

The magneto-optical recording medium according to the invention of claim 3 is
As described above, in the magneto-optical recording medium according to claim 2, the 0th magnetic layer made of a rare earth metal-transition metal alloy is formed between the dielectric layer and the first magnetic layer. The 0th magnetic layer has a Curie point higher than that of the 1st magnetic layer, has a coercive force of almost zero at room temperature, exhibits in-plane magnetic anisotropy at room temperature, and has a temperature above a predetermined temperature. In addition to the effect of claim 2, since the perpendicular magnetic anisotropy is dominant,
It is possible to reproduce smaller recorded bits.

That is, when the 0th magnetic layer is irradiated with the light beam during reproduction, the temperature distribution of the irradiated portion is almost a Gaussian distribution. Therefore, the temperature of only the central region smaller than the diameter of the light beam is reduced. Rises.

With this temperature rise, the magnetization of the temperature rise portion shifts from in-plane magnetization to perpendicular magnetization. At this time, the magnetization direction of the 0th magnetic layer follows the magnetization direction of the 1st magnetic layer due to the exchange coupling force between the two layers of the 0th magnetic layer and the 1st magnetic layer. When the temperature rising portion shifts from the in-plane magnetization to the perpendicular magnetization, only the temperature rising portion exhibits the polar Kerr effect, and the information is reproduced based on the reflected light from the portion.

Then, when the light beam moves to reproduce the next recording bit, the temperature of the previous reproducing portion decreases and the perpendicular magnetization changes to the in-plane magnetization, so that the polar Kerr effect is not exhibited. This means that the magnetization recorded in the first magnetic layer is masked by the in-plane magnetization of the 0th magnetic layer and cannot be read out. This eliminates signal mixing from adjacent bits, which causes noise and reduces reproduction resolution. As described above, since only the area having the temperature equal to or higher than the predetermined temperature is involved in the reproduction, it is possible to reproduce the recording bit smaller than the conventional one. This significantly improves the recording density.

The magneto-optical recording medium according to the invention of claim 4 is
As described above, in the magneto-optical recording medium according to claim 2 or 3, the Curie point of the first magnetic layer is 100 to 250 ° C,
The coercive force at room temperature is 5 kOe or more, and the intermediate magnetic layer is
The temperature exhibiting perpendicular magnetic anisotropy is 80 ° C. or higher, the Curie point is the Curie point or higher of the first magnetic layer, the Curie point of the second magnetic layer is 150 to 400 ° C., and the coercive force at room temperature is Is 3 kOe or less, the magnetic coupling between the first magnetic layer and the second magnetic layer occurs when the recording temperature is 80 ° C. or higher, in addition to the effect of claim 2 or 3. Since the Curie point of the intermediate magnetic layer is equal to or higher than the Curie point of the first magnetic layer, the information recorded in the second magnetic layer is always transferred to the first magnetic layer. Furthermore, since the coercive force of the second magnetic layer at room temperature is 3 kOe or less, the initializing magnetic field is 3 kOe or less. Further, the Curie point of the first magnetic layer is 100 to 250 ° C.
By setting the Curie point of the magnetic layer to 150 to 400 ° C., recording can be performed with a laser power that is practically no problem, and sufficient reproduction signal characteristics can be obtained.

The magneto-optical recording medium according to the invention of claim 5 is
As described above, in the magneto-optical recording medium according to claim 2 or 3, the composition of the first magnetic layer is set to be a transition metal-rich or compensation composition at room temperature, and the composition of the intermediate magnetic layer is , Rare earth metal rich at room temperature, compensation point is 1
The composition of the second magnetic layer is such that it is rich in rare earth metals at room temperature, and the compensation point is higher than the compensation point of the intermediate magnetic layer and lower than 300 ° C. Since it is set, in addition to the effect of claim 2 or 3, the direction of magnetization of the rare earth metal is shown from room temperature to the compensation point, and the direction of magnetization of the transition metal is shown from the compensation point to the Curie point. That is, since the direction of the magnetization recorded at a high temperature during recording is reversed at room temperature, it is possible to make the direction of the initialization magnetic field and the direction of the recording magnetic field the same.
Furthermore, since the compensation point of the intermediate magnetic layer is lower than the compensation point of the second magnetic layer, the leakage magnetic field of the intermediate magnetic layer can be used during recording, and the light modulation overwrite becomes easy.
By setting the compensation point of the second magnetic layer to 100 to 300 ° C. and the compensation point of the intermediate magnetic layer to 100 to 250 ° C., there is an effect that recording can be performed with a laser power having no practical problem.

The magneto-optical recording medium according to the invention of claim 6 is
As described above, in the magneto-optical recording medium according to claim 2, the first magnetic layer is made of DyFeCo, the intermediate magnetic layer is made of GdFeCo, and the second magnetic layer is made of GdD.
Since it is composed of yFeCo or DyFeCo, in addition to the effect of claim 2, 3, 4 or 5, it becomes possible to determine the coercive force at room temperature and the direction of magnetization by the composition ratio of the rare earth metal, and the Curie ratio by the Fe / Co ratio. It is possible to determine the points and the compensation points.

The magneto-optical recording medium according to the invention of claim 7 is
As described above, a magneto-optical recording medium according to claim 2, 3, 4 or 5, the first magnetic layer _{Dy a (Fe b Co 1-} b)
_1-a , and the intermediate magnetic layer is Gd _c (Fe _d Co _1-d )
_1-c , and the second magnetic layer is (Gd _e Dy _1-e ) _g (F
e _f Co _1-f ) _1-g , or Dy _h (Fe _i Co
_1-i ) _1-h , a, b, c, d, e, f, g,
h and i are 0.18 ≦ a ≦ 0.25, 0.70 ≦ b ≦ 0.90, 0.26 ≦ c ≦ 0.3, respectively.
2, 0.50 ≦ d ≦ 0.90, 0.10 ≦ e ≦ 0.95, 0.30 ≦ f ≦
0.90, 0.28 ≤ g ≤ 0.33, 0.28 ≤ h ≤ 0.33, 0.30 ≤ i
Since it is set so as to satisfy ≦ 0.80, claims 2 and 3,
In addition to the effect of 4 or 5, by limiting the composition,
There is an effect that recording can be performed with appropriate laser power, initialization magnetic field, and recording magnetic field, and at the same time, reproduction signal quality required for digital recording can be secured.

The magneto-optical recording medium according to the invention of claim 8 is
As described above, in the magneto-optical recording medium according to claim 2, 3, 4, 5, 6, or 7, the first magnetic layer has a thickness of 20 to 10
0 nm, the thickness of the intermediate magnetic layer is set to 5 to 50 nm, and the thickness of the second magnetic layer is set to 20 to 200 nm. Therefore, in addition to the effect of claim 2, 3, 4, 5, 6 or 7, it is appropriate. It is possible to perform recording with various laser powers, initialization magnetic fields, and recording magnetic fields, and it is possible to ensure the reproduction signal quality required for digital recording.

The magneto-optical recording method according to the invention of claim 9
As described above, the dielectric layer and the dielectric layer are formed on the light-transmitting substrate.
A first magnetic layer made of a rare earth metal-transition metal alloy and having a characteristic that perpendicular magnetic anisotropy is dominant from room temperature to the Curie point, and a rare earth metal-transition metal alloy having a higher Curie point than the first magnetic layer. A second magnetic layer having a coercive force lower than that of the first magnetic layer at room temperature and a protective layer are sequentially formed. The dielectric layer and the protective layer are each made of Al.
The magnetization of the second magnetic layer is changed by applying a constant initialization magnetic field perpendicular to the layer surface to a magneto-optical recording medium made of N or AlSiN having an Si content of 15 at% or less. A high-level laser beam, which is a magneto-optical recording method for recording information on the first magnetic layer by irradiating a laser beam whose intensity is modulated to a high level and a low level according to the information after initialization. To raise the temperature to a temperature near the Curie point of the second magnetic layer or higher, and to irradiate a low level laser beam to a temperature near the Curie point of the first magnetic layer or higher. Since the temperature is raised to a temperature lower than the Curie point of the second magnetic layer,
Operation of light modulation overwrite, that is, second at room temperature
It is possible to smoothly perform the initialization operation of the magnetic layer, the recording operation to the second magnetic layer, and the transfer operation from the second magnetic layer to the first magnetic layer.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a magneto-optical disk according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the temperature dependence of the coercive force of each magnetic layer in the magneto-optical disk of FIG.

FIG. 3 is an explanatory diagram showing a recording process in the magneto-optical disc of FIG.

4 is an explanatory diagram showing the intensity of laser light with which the magneto-optical disk of FIG. 1 is irradiated.

5 shows a C / N of 45 in the magneto-optical disc of FIG.
It is a graph which shows the combination of the laser power of the high level I and the laser power of the low level II when it exceeds dB.

FIG. 6 is a graph showing a comparative example and showing a combination of a high level I laser power and a low level II laser power when the C / N exceeds 45 dB in the conventional magneto-optical disk. .

FIG. 7 is an explanatory diagram showing the temperature dependence of the coercive force of each magnetic layer in the magneto-optical disk of the second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a recording process in a magneto-optical disk having the magnetic layer of FIG.

FIG. 9 is a sectional view showing a schematic configuration of a magneto-optical disk according to a third embodiment of the present invention.

10 is an explanatory diagram showing the temperature dependence of the coercive force of each magnetic layer in the magneto-optical disc of FIG.

11 is an explanatory diagram showing a recording process in the magneto-optical disc of FIG. 9. FIG.

FIG. 12 is a sectional view showing a schematic configuration of a magneto-optical disk of a fourth embodiment of the present invention.

FIG. 13 is an explanatory diagram showing the temperature dependence of the coercive force of each magnetic layer in a conventional magneto-optical disk.

FIG. 14 is an explanatory diagram showing a recording process in a magneto-optical disk having the magnetic layer of FIG.

[Explanation of symbols]

 1 substrate 2 dielectric layer 3 magnetic layer (first magnetic layer) 4 magnetic layer (second magnetic layer) 5 protective layer 6 overcoat layer 7 magnetic layer (intermediate magnetic layer) 8 magnetic layer (0th magnetic layer)

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G11B 11/10 586 B 8935-5D (72) Inventor Akira Takahashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Kenji Ota 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture

Claims (9)

[Claims] 1. A first magnetic layer comprising a dielectric layer and a rare earth metal-transition metal alloy on a substrate having a light-transmitting property, and having a characteristic that perpendicular magnetic anisotropy is dominant from room temperature to the Curie point. A second magnetic layer made of a rare earth metal-transition metal alloy, having a Curie point higher than that of the first magnetic layer and having a coercive force at room temperature lower than that of the first magnetic layer, and a protective layer are sequentially formed. The magneto-optical recording medium, wherein the dielectric layer and the protective layer are each made of AlN or AlSiN having a Si content of 15 at% or less. 2. An intermediate magnetic layer made of a rare earth metal-transition metal alloy is formed between the first magnetic layer and the second magnetic layer, and the intermediate magnetic layer has a coercive force of approximately room temperature. 2. The magneto-optical property according to claim 1, wherein the magneto-optical property is zero, and the in-plane magnetic anisotropy and the perpendicular magnetic anisotropy are substantially equal at room temperature, and the perpendicular magnetic anisotropy is dominant at a predetermined temperature or higher. recoding media. 3. A zeroth magnetic layer made of a rare earth metal-transition metal alloy is formed between the dielectric layer and the first magnetic layer, and the zeroth magnetic layer is more than the first magnetic layer. It has a high Curie point, has a coercive force of almost zero at room temperature, exhibits in-plane magnetic anisotropy at room temperature, and perpendicular magnetic anisotropy at a certain temperature or higher. The magneto-optical recording medium according to claim 2, wherein 4. The Curie point of the first magnetic layer is 100 to 25.
The coercive force at 0 ° C. and room temperature is 5 kOe or more, the temperature at which the intermediate magnetic layer exhibits perpendicular magnetic anisotropy is 80 ° C. or more,
The Curie point is equal to or higher than the Curie point of the first magnetic layer,
The magneto-optical recording medium according to claim 2, wherein the magnetic layer has a Curie point of 150 to 400 ° C. and a coercive force at room temperature of 3 kOe or less. 5. The composition of the first magnetic layer is set to be a transition metal rich or compensation composition at room temperature, and the composition of the intermediate magnetic layer is a rare earth metal rich at room temperature, and the compensation point is 100 to 100. The temperature of the second magnetic layer is set to 250 ° C., the composition of the second magnetic layer is rich in rare earth metal at room temperature, and the compensation point is set higher than the compensation point of the intermediate magnetic layer and lower than 300 ° C. The magneto-optical recording medium according to claim 2 or 3, wherein 6. The first magnetic layer is made of DyFeCo, the intermediate magnetic layer is made of GdFeCo, and the second magnetic layer is made of GdDy.
6. The magneto-optical recording medium according to claim 2, which is made of FeCo or DyFeCo. 7. The first magnetic layer is Dy _a (Fe _b Co _1-b ).
_1-a , and the intermediate magnetic layer is Gd _c (Fe _d Co _1-d )
_1-c , and the second magnetic layer is (Gd _e Dy _1-e ) _g (F
e _f Co _1-f ) _1-g , or Dy _h (Fe _i Co
_1-i ) _1-h , a, b, c, d, e, f, g,
h and i are 0.18 ≦ a ≦ 0.25, 0.70 ≦ b ≦ 0.90, 0.26 ≦ c ≦ 0.3, respectively.
2, 0.50 ≦ d ≦ 0.90, 0.10 ≦ e ≦ 0.95, 0.30 ≦ f ≦ 0.90, 0.28 ≦ g ≦ 0.3
6. The magneto-optical recording medium according to claim 2, wherein it is set so as to satisfy 3, 0.28≤h≤0.33 and 0.30≤i≤0.80. 8. The first magnetic layer has a thickness of 20 to 100 nm, the intermediate magnetic layer has a thickness of 5 to 50 nm, and the second magnetic layer has a thickness of 2.
The magneto-optical recording medium according to claim 2, 3, 4, 5, 6 or 7, wherein the magneto-optical recording medium is set to 0 to 200 nm. 9. A first magnetic layer comprising a dielectric layer and a rare earth metal-transition metal alloy on a light-transmissive substrate, the first magnetic layer having a characteristic that perpendicular magnetic anisotropy is dominant from room temperature to the Curie point. A second magnetic layer made of a rare earth metal-transition metal alloy, having a Curie point higher than that of the first magnetic layer, and having a coercive force lower than that of the first magnetic layer at room temperature, and a protective layer are sequentially formed. , The dielectric layer and the protective layer are each made of AlN.
Alternatively, by applying a constant initialization magnetic field perpendicular to the layer surface to a magneto-optical recording medium made of AlSiN having a Si content of 15 at% or less, the magnetization of the second magnetic layer is changed in the direction of the initialization magnetic field. A magneto-optical recording method of recording information on the first magnetic layer by irradiating laser light whose intensity is modulated to a high level and a low level according to information after initialization, By irradiating, the temperature is raised to a temperature near the Curie point of the second magnetic layer or higher, and by irradiating a low-level laser beam, the temperature near the Curie point of the first magnetic layer or higher. A magneto-optical recording method characterized in that the temperature is raised to a temperature lower than the Curie point of the second magnetic layer.