JPH02101657A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To allow high-speed density recording while using a low recording laser power by respectively specifying the concn.of rare earth elements of the amorphous magnetic alloy film which consists of the rare earth metals and transition metals and has the axis of easy magnetization in the direction perpendicular to the film plane, the compensation temp. of this magnetic alloy film and the gradient value of the coercive force of the film. CONSTITUTION:The amorphous magnetic alloy film to be used for the recording layer of the magnetic recording medium is constituted of at least >=1 kinds of the rare earth metals and at least >=1 kinds of the transition metals and the compsn. thereof is so regulated that the concn. of the rear earth metals is near the compensation compsn. and rich with respect to the compensation compsn. The compensation temp. of the magnetic alloy film is specified to room temp. or above and the Curie temp. to <=200 deg.C. Further, the gradient value Hc50/50[Oe/ deg.C] is regulated to >=20 when the coercive force of the alloy film at the temp. lower by 50 deg.C than the Curie temp. is designated as Hc50. The recording bit length of the rewritable medium is then short and the shape thereof is sharp and the recording at 22.6m/sec line speed and 10 to 20NHz frequency is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a rewritable magneto-optical recording medium, and particularly to a magneto-optical recording medium capable of high-speed, high-density recording.

[Conventional technology]

Magneto-optical recording media utilize perpendicular magnetic recording and magneto-optical effects (Kerr effect, etc.), and like conventional optical recording media, they use laser light to record and reproduce information, so they have a large recording capacity. Can be overwritten. Furthermore, recording and reproduction can be performed without contact between the head and the medium, and it is not affected by dust, so it has excellent stability. For this reason, magneto-optical recording media are currently being actively researched, and are expected to be used for document information files, video/still image files, computer memory, etc., or to replace floppy disks and hard disks, and are expected to be commercialized in the near future. We have reached the point of welcoming

A transition metal (
Fe, Co) and rare earth metals (Tb, Dy, Gd,
Amorphous (Ha, Er, etc.)
Magnetic alloy films have been proposed. A magnetic alloy film made by combining one or more transition metals and one or more rare earth metals and fabricated on a substrate by sputtering or vapor deposition is an amorphous perpendicularly magnetized film (easily magnetized in the direction perpendicular to the film surface) near the compensation composition. It becomes a magnetized film with an axis) and can be applied to magneto-optical recording media.

It is known that when applying the above magnetic alloy film to a magneto-optical recording medium, at least the following conditions must be satisfied.

■Reproduction C is large.

■Good recording sensitivity (low laser power during recording) @ ■The recorded memory is stable.

■The recorded magnetic domains (bits) are small, allowing for high density recording.

■It is a perpendicular magnetization film.

It is generally said that there is the following relationship between the above characteristics and the physical properties of the magnetic alloy film.

The reproduction C/N of (2) is related to the magneto-optical characteristics, and the Kerr rotation angle θ
The larger k is, the better it is. The recording sensitivity (2) is related to the Curie temperature Tc, and becomes better as the Curie temperature Tc is lower.

The memory stability (2) and the high density (2) are related to the coercive force He, and the larger the coercive force He, the better. In order to obtain the perpendicular magnetization film of (2), it is necessary that the coercive force He>4πMs (Ms: saturation magnetization).

The film that satisfies the above conditions and is considered the most promising as a recording layer of a magneto-optical recording medium is a TbFaCoa-based amorphous magnetic alloy film, which is disclosed in JP-A-58-73746 and JP-A-58.
This method has been proposed in, for example, Japanese Patent No.-159252.

In addition, IEEJ study group materials MR84-37, MR84-
38, MR-39 (1982) has the above TbFeC
Evaluation data of a magneto-optical disk manufactured by forming an O film on a polycarbonate substrate is described. To give an example of the specifications of this magneto-optical disk, the disk rotation speed is 90.
Orpm, linear velocity 7/sec, recording laser power 5.7aV
, the erasing laser power is 7 mW.

However, although the magneto-optical recording medium using the TbFeCo film has a relatively large Kerr rotation angle θk of approximately 0.35 degrees and a significantly superior coercive force Hc of approximately 2 to 10 kOe,
The above value was the limit for recording sensitivity.

In response, the present inventors proposed a magneto-optical recording medium with improved recording sensitivity in Japanese Patent Laid-Open No. 59-61011. In the examples of the same publication, glass, which has thermal conductivity one order of magnitude lower than that of plastic, is used for the substrate, and TbFeCo or GdFeCo is used as the composition constituting the recording layer.
An example of a magneto-optical recording medium is disclosed in which the recording sensitivity is improved by lowering the Curie temperature Tc by adding Dy to the above. This recording medium is (Tbo, tDyo,
3) O-22 (Fe0e5cOg, J., 7. (ratio is atomic weight ratio) is used for magnetic R1! (film thickness 200),
A recording power of 2.5 mW is obtained. This recording condition is a recording frequency of 2MH2.

[Problem to be solved by the invention]

However, from the standpoint of increasing the speed of information processing and replacing hard disks, it is expected that the recording speed of magneto-optical recording media will be equal to or higher than that of hard disks. That is, disk rotation speed 3600 rpm, linear speed 22.6 m
It is desirable to perform recording at a recording laser power (medium surface) of 10 Il+W or less. To achieve this, it is necessary to achieve even higher speed and higher density.

In view of the above points, it is an object of the present invention to provide a magneto-optical recording medium that satisfies the above requirements and is capable of high-speed and high-density recording.

[Means and effects for solving the problem] In order to achieve the above object, according to the present invention, the film is made of at least one kind of rare earth metal and at least one kind of transition metal, and In a magneto-optical recording medium whose recording layer is an amorphous magnetic alloy film having an easy axis of magnetization, the concentration of rare earth metal in the magnetic alloy film is near a compensation composition and on the high concentration (rich) side with respect to the compensation composition. Yes, the compensation temperature of the magnetic alloy film is room temperature or higher and the Curie temperature is 200.
The coercive force of the magnetic alloy film at a temperature of 50° C. or below and 50° C. lower than the Curie temperature is HCi. Then, the gradient value) leg o / 50 (Oe / 5
A magneto-optical recording medium characterized in that 0 [Oe/°C] is 20 or more is provided.

In order to sufficiently respond to the above-mentioned speeding up of information processing and replacement of hard disks, etc., it is required to be able to record at higher speeds and higher density. In other words, the number of disk rotations is 3
60Orpm, 4! Speed 22.6m/sec, recording frequency 5
It is required that the recording laser power (medium surface) is 10 mW or less, the recording bit size is one tone or less, and the shape of the recording bit is sharp.

Therefore, as a result of intensive research, the inventors of the present invention have found that (i) the concentration of rare earth metal is compensated for in the composition (rare earth metal in the magnetic alloy film at room temperature). When the magnetic moment of the metal is 'RE--the magnetic moment of the transition metal is MTM.

The composition must be close to MRE-MTMI (composition that gives 0) and be rich in rare earth metals.

(…) The compensation temperature (temperature at which the apparent upper magnetization becomes zero at room temperature before reaching the Curie temperature in a ferrimagnetic material) is above room temperature, and the Curie temperature is below 200°C, preferably below 180°C. Something.

(iii) When the coercive force at a temperature 50°C lower than the Curie temperature is HQso, the slope value He, 150
is 20 (Oe/℃) or more.

It has been found that the above target values and characteristics can be achieved when the above conditions are satisfied.

Next, a magneto-optical recording medium of the present invention will be described in detail with reference to the drawings.

FIG. 1(A) shows the temperature characteristics of the coercive force He and 4πMs (Ms is saturation magnetization) in the amorphous magnetic alloy film A of the magneto-optical recording medium of the present invention in comparison with that of the prior art.
The solid line in the figure is the data for the magnetic alloy film A, and the broken line is the data for the magnetic alloy film B in the conventional magneto-optical recording medium.

First, the amorphous magnetic alloy film used in the recording layer of the magnetic recording medium of the present invention contains at least one rare earth metal (
It consists of Tb, Dy, Gd, t (o, Er, etc.) and at least one kind of transition metal, and its composition is defined so that the concentration of rare earth metal is near the compensation composition and rich with respect to the compensation composition. . With respect to the compensation composition, the rare earth metal-rich magnetic alloy film A generally has a larger coercive force He at room temperature than the transition metal-rich magnetic alloy film B, and the coercive force H
The slope of the temperature characteristic curve of e is large, the coercive force tlc decreases linearly near the Curie temperature Tc, and the value of the saturation magnetization Ms is small. This trend and the above (iii)
Combined with these conditions, it is possible to record with a low recording laser power, further shorten the recording bit length to 1- or less, and sharpen the bit shape. The conditions for starting recording are Hc<4πMs+Hex (Hex is the bias magnetic field, and in Figure 1 (A), at 5000s, He' = 4πMs+
5000e), FIG. 1A shows the case where an external magnetic field of 5000 seconds is applied, and the recording start temperature Ta' of the magnetic alloy film A is about 130°C, while the recording start temperature Tb of the magnetic alloy film B ' is approximately 70°C. When the stray magnetic field from the periphery of the recording magnetic domain is 4πMs valve 0, the recording start temperature of each magnetic alloy film is Tb''<T al/.Here, the magnetic alloy film was irradiated with the same laser power with a spot diameter of 1.2 μl. If the recording start temperature is high (the range of recordable temperatures is narrow), the recording bits will become larger. Small recording bits close to the size of a spot can be recorded.In the case of magnetic alloy film A, the recordable temperature range will be explained below, point a' is Hc=4π and s+
Therefore, the recording condition is 4.
x Ms + 5000s)He, so the straight line a'
The area Ta' -TcA to the right of -Ta' becomes the recordable range. In the case of magnetic alloy film B, the temperature range of Tb'-TcB becomes the recording layer. To make recording bits small and sharp, a rare earth metal-rich magnetic alloy film A having magnetic properties has a small saturation magnetization Ms, a large coercive force He at room temperature, and a sharp decrease in the coercive force He near the Curie temperature Tc. Must. FIGS. 2(a) and 2(b) show recording bit shapes in magnetic alloy film A (present invention) and magnetic alloy film B (prior art), respectively, when recording is performed by the optical modulation method.

Further, FIGS. 3(a) and 3(b) show recording bit shapes in magnetic alloy film A and magnetic alloy film B, respectively, when recording is performed by the magnetic field modulation method. The magnetic field modulation method involves irradiating a magneto-optical recording medium with a laser beam continuously or in a pulsed manner and manually applying a recording or erasing signal to a magnetic head, and is attracting attention as a method that can be overridden. As shown in FIGS. 2 and 3, it can be seen that the magnetic alloy film A according to the present invention has a shorter recording bit length and a sharper shape in all recording methods.

The rare earth metal concentration z (at
om%) is the concentration of rare earth metal in the compensation composition.

(atom%), it is more preferable that zo(z(zo÷4). If the value of 2 becomes too large, the coercivity 1/10 at room temperature and the Kerr rotation angle Ok will decrease rapidly,
It becomes unsuitable for the recording layer of magneto-optical recording media.

Further, the magnetic alloy film of the present invention has a compensation temperature Tcomp of room temperature or higher and a Curie temperature Tc of 200°C or lower, preferably 180°C or lower. When the compensation temperature Tcomp is lower than room temperature, the saturation magnetization Ms becomes large and the coercive force becomes 11
c becomes small, which is not preferable. Furthermore, if the Curie temperature Tc is higher than 200° C., recording sensitivity deteriorates, which is not preferable for increasing speed.

Moreover, the magnetic alloy film of the present invention has a Curie humidity Tc of 5
When the coercive force at a temperature lower than 0°C is reduced by lIC6°,
The gradient value H65°150 is defined as 20 (Oe/°C) or more.

If this gradient value is smaller than 20 (Oe/° C.), the recording bit length becomes long and the sharpness of the recording bit shape is lost, which is not preferable for achieving high density.

In particular, when the magnetic alloy film B in FIG. 1(A) has a gradual tail near the Curie temperature Tc, when recording bits are formed by the optical modulation method, the recording bits are as shown in FIG. 2(b). When a recording bit is formed by the magnetic field modulation method, it becomes a chevron shape with a tail as shown in FIG. 3(b), and these disturbances cause noise.

Furthermore, from the viewpoint of the stability of the memory of recorded bits, it is preferable that the magnetic alloy film of the present invention has a coercive force He at room temperature of greater than 2 kOe, i.e., )lc)2X4πMs. Also, from the point of view of shortening the recording bit length, 4πMg≦1
300 (Gauss) is preferable.

As an amorphous magnetic alloy film that can be applied to the recording layer of the magneto-optical recording medium of the present invention, (Tb1゜o-ZD)'χ)z(Fe
Engineering. . -yCoy)log-2(0<x<10013<
y〈20. Desirably 50<x<100°3(y<10
, and when Z is the compensation composition, Zo<z<ZO
+4 m)-(Gd1110-zDyz)z(F
etoo-ycOy) zoo-z(0<x<100,
Qry<20. Preferably 50<x<100.0<y<
10, and Zo<Z<Zo+4. ], but is not limited thereto and can be applied as long as it satisfies the above conditions.

Next, a specific example of the layer structure of the magneto-optical recording medium of the present invention will be described with reference to FIGS. 4 and 5.

FIG. 4 is a cross-sectional view showing an example of the layer structure when plastic is used as the material for the substrate 1, in which 2 is a dielectric layer, 3 is a recording layer (
(amorphous magnetic alloy film), 4 is a protective layer, and 5 is a cover layer or bonding layer.

As specific materials for the plastic substrate 1, resins such as polycarbonate, epoxy resin, methyl methacrylate, and polyolefin can be used. Guide tracks and preformats may be formed on the substrate 1 in advance. Further, the laser beam incident surface of the substrate 1 may be coated with a dielectric layer, a hydrophobic, gas-resistant layer (for example, a fluororesin layer), etc. to prevent the intrusion of H and O10□.

The dielectric layer 2 prevents H,0,02 from entering from outside the substrate and deteriorating the magnetic properties of the recording layer 3, and also plays the role of enhancing the magneto-optic effect (Kerr rotation angle Ok) through multiple reflections of light. conduct. For this reason, a material with a refractive index n as large as possible is used, and its film thickness is set so that the apparent magneto-optic effect is as large as possible due to multiple reflections. Therefore, the refractive index n of the dielectric N2 is preferably larger than 1.7, and the film thickness is 600 to 1500.
The person is appropriate. Further, specific materials used for the dielectric layer 2 include 5izNy, 5izOy, AQ, O,
, Ta2O, , Tie, , ZnS , ZnO, Mg
O,AQN.

AQON, ZrAQSi, ZrAQON, AQS
iN, AfiSiNO,Y,O,,In,0.
, Zro, , Cr2O, etc. are used.

Among these, AflON, ZrA[Si,
5izNy.

At least 1 of 5izOy, AQzO, Ta, Os, etc.
It is more preferable to use more than one species. The dielectric layer 2 is formed by sputtering, vapor deposition, ion blating, or the like.

The recording layer 3 is composed of an amorphous magnetic alloy film that satisfies the above conditions. Here, let us consider the thickness of the recording layer 3. Figure 6 shows the film thickness t of the magnetic layer of a typical magneto-optical disk.
The relationship between P and recording laser power Pw is shown in a graph. As can be seen from the figure, the recording laser power Pw is
Minimum near humans.

If the number of people is less than 200, the laser light will pass through and the heat storage of the laser light will be insufficient.If the number of people is more than 200, the recording laser power Pw will increase as the thickness of the magnetic layer increases according to the relational expression PwαF. In addition, in this example, the substrate 1
Since the substrate 1. is made of plastic, even if the dielectric layer 2 is provided, some 1120.02 will remain on the substrate 1. It invades the recording layer 3 through the dielectric layer 2, and some oxidation of the surface N (approximately 100 layers) is unavoidable. From the above, the film thickness of recording N3 is 400~1
000 people is preferable, and 400 to 800 people is more preferable. The recording layer 3 is formed by sputtering, vapor deposition, or the like.

The protective layer 4 is provided for the purpose of preventing H2O, 02 from entering the recording layer 3. In addition, in order to enhance the heat storage effect of the recording laser beam, the protective layer 4 should have a thermal conductivity as low as possible, and should have a thermal conductivity of 5 x 10"caQ/cm-s・"C (room temperature).
It is preferably less than or equal to 3 X 10””caQ/c
It is more preferable that the temperature is below m-s・"C (room temperature). This protective layer 4 is formed using the same material as the dielectric layer 2, and is formed to the same thickness by the same method, but it is different. It's okay.

A cover layer or bonding layer 5 is provided on the protective layer 4. The cover layer protects the protective layer 4, and the bonding layer performs bonding in a double-sided recording type medium.

These cover layers or bonding layers 5 are made of ultraviolet curing resin (U
V resin), thermoplastic resin, plasma polymerized resin, etc., to a film thickness of 1 μffi to 100 μl.

Further, when a double-sided recording type magneto-optical disk is prepared by bonding two disks together, it is preferable to join the ends of the disks with a dielectric material or plastic.

FIG. 5 is a cross-sectional view showing the layer structure when glass is used as the material for the substrate 11, in which 12 is a dielectric layer, 13 is a recording layer (amorphous magnetic alloy layer), 14 is a heat insulating layer, and 15 is a reflective layer. , 16
is the cover layer.

The glass substrate 11 has a thermal conductivity of 2 x 10-3-4 x
1O-3caQ/cIl-3・℃ and the thermal conductivity of the plastic substrate 1 3.5 x 10-' ~ 6 x 1O-4ca
One order of magnitude better than Q/cIIl-8・℃. Furthermore, in the case of the glass substrate 11, there is no intrusion of 820, 02 from outside the substrate.

The dielectric N12 is provided to enhance the magneto-optic effect (Kerr rotation angle θk) by multiple reflection of light.

Therefore, the refractive index n is as large as possible (n>1.7)
The material is used, and its film thickness is set so that the apparent magneto-optic effect is as large as possible due to multiple reflections.

For forming the dielectric M12, the dielectric M2 in the configuration example shown in FIG.
Similar materials and methods can be used. Similarly, the appropriate film thickness is 600 to 1,500 people.

An amorphous magnetic alloy film that satisfies the above-mentioned conditions is used for the recording M13, but in consideration of the above-mentioned properties of the glass substrate 11, it is desirable to make the film as thin as possible. That is, the film thickness is preferably 100 to 400, and 100 to 300.
People are more preferred.

The heat insulating layer 14 is provided for the purpose of being a heat absorbing layer that reduces heat diffusion to the recording layer 13 and the reflective layer 15 having good thermal conductivity and prevents heat diffusion in the film surface direction of the heat insulating layer. Therefore, the insulation layer 14
has a thermal conductivity of 5 x 10-"can/cm-s・'
Plastic resin of C or below (e.g. thermoplastic resin such as polystyrene-butadiene, methyl methacrylate-butadiene, polyurethane, hot null 1-resin, plasma polymerized resin, etc.), or Sun, 5in2 (amorphous)
, ZrO,, Nd, 03, Mn2o, l Gd203
+ DY2 o31Fe, 04. AQ, O, -
3in, , Tie□, HfO2, glass, etc. 50
Used in film thicknesses of 0-1500. The heat insulating layer 14 is formed by a sputtering method, a vapor deposition method, etc. in the case of an inorganic material, and by a spin coating method, a roller coating method, etc. in the case of an organic material.

The reflective layer 16 is provided for enhancement of the magneto-optic effect. This reflective layer 16 is made of AQ, Cr, Cu,
The film is formed using a material such as Nd, Rh, Pt, Au, Cr, Ni, etc. to a thickness of 200 to 1000 layers by a method such as a sputtering method or a vapor deposition method.

The cover layer 17 is provided to prevent oxidation corrosion and damage to the reflective layer 16. This cover layer 17 is made of the same material as that used for the heat insulating layer 14 and made by the same method.
The film is formed to a thickness of 00 μm.

〔Example〕

Examples of the present invention are listed below, but the present invention is not limited to these examples.

Example 1 A polycarbonate plate with a diameter of 130 nm and a thickness of 1.2 m was used as a substrate, and a dielectric layer of 5izNy (refractive index n = 2.1
) was formed to a thickness of 700 mm by sputtering. The sputtering conditions at this time were back pressure 1. OX 10-'
Torr or less, carrier gas: Ar+N2 mixed gas, gas pressure PAr/PN = 10 mm Torr, substrate rotation speed 15 rpm, preparation time 25 minutes, and before film formation, press sputtering was performed at RF power 300 V for 30 minutes. The board is also water cooled.

The substrate temperature was 100° C. or lower. Next, in an RF sputtering device, Fe, g-scOsTbto +5D
Using an alloy target with a composition of 14, an amorphous magnetic alloy film (perpendicular magnetization film) was formed as a recording layer on the dielectric layer.
Formed to the thickness of a human. The sputtering conditions at this time were back pressure 1. OX 10'''' Torr or less, Ar gas pressure 3.0+m+Torr.

The RF power was 200111, the substrate rotation speed was 15 rpm, and the manufacturing time was 20 minutes. Next, a protective layer is formed on the recording layer using the same material as the dielectric layer, using the same manufacturing method, and having the same thickness.
, -39(K)) to a film thickness of IO habit,
A cover layer is formed by irradiating ultraviolet rays, and a fourth layer is formed.
A magneto-optical disk having the layer structure shown in the figure was obtained.

Examples 2 to 6 and Comparative Examples 1 and 3 The materials shown in Table 1 were used as the plastic substrate, recording layer, dielectric layer, protective layer, and cover layer (bonding layer).
Each layer was fabricated with the thickness shown in Figure 4 to obtain a magneto-optical disk having the layer structure shown in Figure 4. The method for each substrate is the same as in Example 1. The recording layer, dielectric layer and protective layer are prepared by sputtering or vapor deposition, and in the case of a cover layer or bonding layer made of UV resin, spin coating is performed in the same manner as in Example 1, followed by ultraviolet irradiation, and thermoplastic hot melt resin is prepared. In the case of , it was made by applying with a heated roller.

Examples 7 to 10 and Comparative Examples 2 and 4 The materials shown in Table 1 were used as the glass substrate, recording layer, dielectric layer, heat insulating layer, reflective layer and cover layer, respectively.
Each layer was fabricated with the film thickness shown in Figure 5 to obtain a magneto-optical disk having the layer structure shown in Figure 5. The diameter of the glass substrate was 130 mm, and the thickness was 1.2+m. The recording layer, dielectric layer, and cover layer were manufactured in the same manner as described above, and the heat insulating layer was manufactured using the same method as the dielectric layer.

The reflective layer was produced by sputtering or vapor deposition.

Characteristics of each magneto-optical disk produced as described above (Curie temperature Tc (50 [Oe/℃], coercive force (koe))
, 4 πMs (Gauss) , He, , 150
(Oa/"C), recording speed (rpllll), recording laser power (msu), and C/" (dB)) are shown in Table 3 for comparison.

In Table 3, Hcs o / 50 (Os/”C
) is the coercive force He at a temperature 50°C lower than the Curie temperature Tc. is the value divided by the temperature 50''.The recording speed also indicates the number of disk rotations that can be recorded with the recording laser power (power at which C/to is saturated) in the right column.Recording is performed using a CAV disk (diameter 130a++). radius of 60
I went to the mm position.

As can be seen from Table 3, all of the magneto-optical disks of Examples 1 to 10 had a Curie temperature Tc of 180° C. or lower, and a compensation temperature Hc of room temperature or higher. 150 (Os/℃) has characteristics of 20 or more, and 10mW or less (λ = 770-850
nm) recording laser power (medium surface), disk rotation speed 360 Orpm, linear velocity 22.6 m/s, duty 50
%, high-speed recording is possible at a recording frequency of 10 to 20 MH2,
As shown in FIG. 2(a), the recording bits had a sharp shape, a length of 1 μm or less, and a C of 53 or more, allowing high-density recording. Note that the recording layer of Example 2 corresponds to the magnetic alloy film shown in FIG.

On the other hand, the magneto-optical disks of Comparative Examples 1 and 2 have a Curie temperature of T
Although c is relatively low, Has. / 50 (Oe/
In the case of Comparative Example 2 in which the value of 50 [Oe/° C.] was small and a glass substrate was used, the recording speed was limited to 1800 rpm, and the shape of the recorded bits was also slightly disordered. Comparative Examples 3 and 4 have a high Curie temperature Tc, and Hca
. /50 (Oe/℃) is small, and even in the case of Comparative Example 3 using a plastic substrate, the recording speed was 1800
rpm was the limit, the shape of the recorded bits was greatly disordered, C was low, and high-density recording was difficult. Note that the recording layer of Comparative Example 3 corresponds to the magnetic alloy film shown in FIG.

〔Effect of the invention〕

As explained in detail above, according to the magneto-optical recording medium of the present invention, the composition of the magnetic alloy film is rich in rare earth metals relative to the compensation composition, and the compensation temperature is equal to or higher than room temperature and the Curie temperature is 2.
Gradient value Hc of coercive force at a temperature of 00°C or lower and 50°C lower than the Curie temperature.

Since 150 is defined as 20 or more, the recording sensitivity is improved, the recording bit length is short and the shape is sharp, and with a low recording laser power of 10 mW or less, the disc rotation speed is 360 Orpm, and the speed is 22.6 m/l. seconds,
High-speed, high-density recording at a recording frequency of 10 to 20 MHz becomes possible.

[Brief explanation of drawings]

FIG. 1(A) shows the coercive force 1 of the magneto-optical recording medium according to the present invention.
A graph showing the temperature characteristics of 1c and 4πMs in comparison with a conventional example. Figure 1 (B) is a diagram showing heat diffusion and crosstalk on a magnetic alloy film. Figure 2 shows the bit shape recorded by the optical modulation method. 3 is a diagram showing a bit shape recorded by the magnetic field modulation method, FIG. 4 is a cross-sectional view showing an example of the layer structure of a magneto-optical recording medium according to the present invention using a plastic substrate, and FIG. FIG. 6 is a sectional view showing an example of the layer structure of the magneto-optical recording medium according to the present invention used.
- It is a diagram showing the relationship between film thickness and recording laser power. 1.11...Substrate 2,12...Dielectric layer 3.13...Recording layer 4...
Protection 1 to 5...Cover layer or bonding 11 14...
Heat insulation layer 15...Reflection ffi 16.
...Cover layer patent applicant Rico Co., Ltd. Patent attorney Toshiaki Ikeura (one idiot) Figure 2 Figure 3 Figure 4 Notebook 1 CB) Figure 5 Figure 6

Claims (1)

[Claims] (1) At least one rare earth metal and at least one
In a magneto-optical recording medium having as a recording layer an amorphous magnetic alloy film comprising at least one transition metal and having an axis of easy magnetization in a direction perpendicular to the film surface, the concentration of the rare earth metal in the magnetic alloy film has a compensation composition. and is on the high concentration (rich) side with respect to the compensation composition, the compensation temperature of the magnetic alloy film is at least room temperature and the Curie temperature is 200 °C or less, and further at a temperature 50 °C lower than the Curie temperature. The coercive force of the magnetic alloy film is H
When _c_5_0, the gradient value H_c_5_0/50
A magneto-optical recording medium characterized in that [Oe/°C] is 20 or more.