JPH07254176A - Magneto-optical recording medium and information reproducing method using the medium - Google Patents

Abstract

(57) [Summary] [Structure] At least a reproducing layer, an intermediate layer and a recording layer are laminated in this order on the substrate, and the reproducing layer is an in-plane magnetized film at room temperature and becomes a perpendicular magnetized film when heated. The recording layer is a perpendicular magnetization film, and the intermediate layer has a Curie temperature lower than that of the reproducing layer. A magneto-optical recording medium is used to irradiate the reproducing layer and the intermediate layer with a light spot so that a part of the light spot becomes perpendicular. As a magnetized film, it is oriented in a stable direction with respect to the magnetization direction according to the information of the recording layer, and information is reproduced by changing the magneto-optical effect of the reflected light of the light spot. [Effect] Simple device without the initialization magnet (conventional device)
By using, the magnetic domain smaller than the beam spot system can be reproduced, crosstalk can be eliminated, and high-density recording in which the linear recording density and the track density are significantly improved can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording / reproducing information with a laser beam by utilizing the magneto-optical effect, particularly a magneto-optical recording medium capable of achieving high density, and a magneto-optical reproducing method. Regarding

[0002]

2. Description of the Related Art As a rewritable high density recording system,
Using the thermal energy of a semiconductor laser to write magnetic domains in a magnetic thin film to record information, using the magneto-optical effect,
Attention has been paid to a magneto-optical recording medium for reading the information.
Further, in recent years, there is an increasing demand for increasing the recording speed of this magneto-optical recording medium to make it a recording medium having a larger capacity.

The linear recording density of an optical disk such as the magneto-optical recording medium largely depends on the laser wavelength of the reproducing optical system and the numerical aperture of the objective lens. That is, since the diameter of the beam waist is determined when the laser wavelength λ of the reproduction optical system and the numerical aperture NA of the objective lens are determined, the mark period that can be reproduced and detected is limited to about λ / 2NA.

On the other hand, track density is limited mainly by crosstalk. This crosstalk is mainly determined by the distribution (profile) of the laser beam on the medium surface, and is represented by a function of λ / 2NA, like the mark period.

Therefore, in order to realize high density in the conventional optical disk, it is necessary to shorten the wavelength of the laser of the reproducing optical system and increase the numerical aperture NA of the objective lens.
However, it is not easy to shorten the laser wavelength due to problems such as element efficiency and heat generation. Also, when the numerical aperture of the objective lens is increased, the distance between the lens and the disk becomes too close and mechanical problems such as collision occur. To do. For this reason,
Techniques have been developed for improving the recording density by devising the configuration of the recording medium and the reading method.

For example, JP-A-3-93058 and JP-A-3-255946 attempt to improve the recording density by magnetic super-resolution using a medium composed of a reproducing layer and a recording layer. This is basically provided with a reproducing layer and a recording layer, and a medium having a structure in which an auxiliary layer and an intermediate layer are provided for the purpose of improving the characteristics. After aligning the orientation in one direction, mask the magnetic domain information of the recording layer and irradiate a light spot, and in the temperature distribution of the medium generated at that time, only the reproducing layer in the high temperature area transfers the magnetic domain information of the recording layer. In this way, it is attempted to improve the recording density by reducing the intersymbol interference at the time of reproduction, enabling reproduction of a signal having a period less than the diffraction limit of light, and enabling reproduction.

[0007]

However, in the super-resolution method described in the above-mentioned Japanese Patent Laid-Open No. 3-93058,
Since a large initialization magnet and a reproducing magnetic field are required for reproduction, there are problems that the drive device becomes expensive and it is difficult to miniaturize it.

On the other hand, the present inventor first tried a magneto-optical recording medium capable of realizing magnetic super-resolution without applying a reproducing magnetic field and a reproducing method of a magneto-optical recording medium using the medium. As shown in FIG. 2, a magnetic film (reproducing layer) having a magnetization oriented in-plane at room temperature and a perpendicular orientation at high temperature, and a magnetic layer having perpendicular magnetic anisotropy (recording layer).
By using a two-layered medium in which a magnetic layer and a magnetic layer are stacked, only the high temperature portion of the light spot becomes a perpendicular magnetization film during reproduction, and the magnetization information of the recording layer is transferred. It realizes resolution. According to this method, it is possible to reproduce a signal having a period equal to or shorter than the diffraction limit of light without the need to perform an operation such as previously aligning the magnetization of the reproducing layer in one direction.

However, in a super-resolution magneto-optical recording medium having a two-layer structure using such an in-plane magnetized film, if the in-plane anisotropy is increased at room temperature, the magnetization information of the recording layer can be sufficiently masked, but the reproduction temperature However, it is difficult to obtain a perfect perpendicular magnetization film. For example, when a RE (rare earth) -rich heavy rare earth-iron group transition metal alloy is used for the regeneration layer, the amount of Co added is increased and the ratio of rare earth elements is increased to increase the Ms at room temperature so that the Curie temperature does not decrease. Then
If the in-plane anisotropy is increased, the compensation temperature will be increased accordingly, and Ms will not be sufficiently small at the reproduction temperature to form a perfect perpendicular magnetization film.

On the contrary, if the in-plane anisotropy at room temperature is made small, a perfect perpendicular magnetization film is obtained at the reproducing temperature, but at room temperature, the interface domain wall formed between the reproducing layer and the recording layer is as shown in FIG. Occurs mainly on the reproduction layer side. That is, in the portion of the reproducing layer near the recording layer, a magnetization component in the perpendicular direction is created according to the magnetization information of the recording layer. Therefore, it is difficult to completely mask the magnetization information of the recording layer in the reproducing layer.

Therefore, in the two-layer super-resolution magneto-optical recording medium using the in-plane magnetized film, it is not easy to obtain a good reproduction signal when the recording mark length or track width is shortened.

Therefore, in view of the above-mentioned problems, an object of the present invention is to further improve the above-mentioned in-plane magnetized film type super-resolution medium, so that the recording layer can be formed at a temperature from room temperature to a high temperature portion in the reproducing beam spot. By further completely masking the magnetization information and allowing the recorded information to be sufficiently reproduced in the high temperature portion of the spot, it is intended to further improve the characteristics such as the linear recording density and the track density.

[0013]

The present invention includes (1) at least a first magnetic layer, a third magnetic layer, and a second magnetic layer from the light incident side.
A magnetic layer formed by stacking magnetic layers in this order on the substrate, wherein the first magnetic layer is an in-plane magnetized film at room temperature and has a temperature that becomes a perpendicular magnetized film between room temperature and the Curie temperature of the third magnetic layer. The second magnetic layer is a perpendicular magnetization film, the Curie temperature of the third magnetic layer is lower than the Curie temperature of both the first magnetic layer and the second magnetic layer, and the in-plane variation of the third magnetic layer at room temperature is different. A magneto-optical recording medium, characterized in that the magnetic anisotropy is larger than the in-plane anisotropy of the first magnetic layer at room temperature, and in particular the saturation magnetization of the magnetic layer at room temperature is larger than the saturation magnetization of the first magnetic layer at room temperature, And (2) by using the magneto-optical recording medium, irradiating a light spot on the first magnetic layer and the third magnetic layer to form a part of the light spot as a perpendicularly magnetized film according to the information of the second magnetic layer. The magnetic field of the reflected light of the light spot by orienting it in a stable direction with respect to the magnetization direction. Providing information reproducing method reproducing information by Manabu effect change.

The magneto-optical recording medium of the present invention and the information recording / reproducing method using the medium will be described below in detail with reference to the drawings. Hereinafter, for the sake of simplicity, the first magnetic layer is referred to as a reproducing layer, the second magnetic layer is referred to as a recording layer, and the third magnetic layer is referred to as an intermediate layer. Therefore, as shown in FIG. 1, the basic structure of the magnetic layer of the magneto-optical recording medium of the present invention is a lamination of a reproducing layer, an intermediate layer and a recording layer.

As the material of the reproducing layer, for example, GdFeCo,
Rare earth-iron group amorphous alloys such as GdCo, GdTbFeCo and GdDyFeCo are desirable. Further, the Curie temperature of the reproducing layer is required to be high in order to obtain a sufficient magneto-optical effect during reproduction, and is preferably 250 ° C., more preferably 300 ° C. or higher. Further, a light rare earth element such as Nd, Sm or Pr may be added for the purpose of improving the reproduction output for short wavelength light.

Examples of the material for the intermediate layer include GdFeCo,
Rare earth-iron group amorphous alloys such as GdCo, GdTbFeCo and GdDyFeCo are desirable. The Curie temperature of the intermediate layer is room temperature or higher, preferably 100 ° C. or higher and 250 ° C. or lower, and more preferably 130 ° C. or higher and 210 ° C. or lower.

The recording layer has a large perpendicular magnetic anisotropy and can maintain a stable magnetization state, such as TbFeCo and DyFe.
Rare earth-iron group element amorphous alloy such as Co and TbDyFeCo; garnet; platinum group-iron group periodic structure film such as Pt / Co and Pd / Co;
Platinum group-iron group alloys such as PtCo and PdCo are preferable.

It is at least necessary that the recording layer can record with a laser power as low as possible and can stably hold the recording magnetic domain at room temperature and reproducing temperature. For this purpose, it is desirable that the perpendicular magnetic anisotropy is large and the Curie temperature is low, but the Curie temperature must be higher than the reproducing temperature.

The reproducing layer must be an in-plane magnetized film at room temperature and a perpendicular magnetized film at high temperature. For this purpose, for example, a ferrimagnetic heavy rare earth iron group transition metal alloy is used for the reproducing layer, the compensation temperature is between room temperature and the Curie temperature, and Ms is large at room temperature as shown in FIG. Then you can use a smaller one. When GdFeCo is used for the reproducing layer, the Gd content is preferably 22 to 38%, more preferably 25 to 35%.

That is, in general, the saturation magnetization of a magnetic thin film is M
It is known that the main direction of magnetization is determined by the effective perpendicular magnetic anisotropy constant K⊥ defined by the following formula I, where s and the perpendicular magnetic anisotropy energy are Ku.
When K⊥ is positive, it is a perpendicular magnetic film, and when it is negative, it is an in-plane magnetic film, and the absolute value shows the strength of anisotropy. That is, for example, a large in-plane anisotropy means that K⊥ is negative and its absolute value is large.

[0021]

[Expression 1] K⊥ = Ku−2πMs ² (I) As shown in FIG. 5, K⊥ is negative because Ms is large in the low temperature portion where the temperature is Tth or lower in the reproducing layer. It is an in-plane magnetized film. However, since the temperature rises during reproduction, Ms becomes smaller, and as a result, 2πMs ² becomes sharply smaller, and the magnitude relationship with the perpendicular magnetic anisotropy energy Ku is reversed (the reversing temperature is Tr). , K⊥ becomes positive and becomes a perpendicular magnetization film. The larger the difference between the compensation temperature and the Curie temperature, the larger the amount of change in K⊥ and the steeper the transition of the magnetization direction from in-plane to perpendicular.

Further, the above Ku changes apparently when laminated with another magnetic film. This is because magnetic coupling forces such as exchange coupling force and magnetostatic coupling force from other stacked magnetic layers act. For example, when it is laminated with the perpendicular magnetization film, Ku is apparently large, and when it is laminated with the in-plane magnetization film, it is apparently small.

In the magneto-optical recording medium of the present invention, an intermediate layer is provided between the reproducing layer and the recording layer. This intermediate layer is an in-plane magnetized film having a larger in-plane magnetic anisotropy than the reproducing layer at room temperature, and a magnetic film having perpendicular magnetic anisotropy or smaller in-plane magnetic anisotropy at the reproducing temperature.

Therefore, at room temperature, the apparent Ku of the reproduction layer is
Is small, and most of the interface domain wall generated between the reproducing layer and the recording layer is generated in the intermediate layer as shown in FIG. 6A, so that the in-plane magnetized film is stably formed. Therefore, the magnetization information of the recording layer can be masked more completely. Also,
At the reproducing temperature, as shown in FIG. 6B, the reproducing layer stably becomes a perpendicular magnetization film, and it becomes possible to sufficiently reproduce the magnetization information of the recording layer.

The in-plane anisotropy of the intermediate layer at room temperature is larger than the in-plane anisotropy of the reproducing layer at room temperature. To increase the in-plane anisotropy, for example, Ms at room temperature may be increased. Further, the perpendicular anisotropy energy Ku may be reduced or a negative value (having in-plane anisotropy) may be given by adding an element such as Co that improves in-plane anisotropy. When the intermediate layer contains GdFe as a main component, Gd is preferably 35 to 50%, more preferably 40 to 47%.

Since the intermediate layer does not have to contribute to the magneto-optical effect, the reproducing characteristic is not deteriorated even if the Curie temperature is set low. Therefore, in order to increase the perpendicular magnetic anisotropy at the reproducing temperature of the intermediate layer, for example, the Curie temperature of the intermediate layer is made lower than the Curie temperature of the reproducing layer,
It suffices that Ms be sufficiently small at the reproduction temperature. The Curie temperature can be lowered by adding a non-magnetic element such as Al, Si or Cu or by reducing the Co content.

Even if the intermediate layer itself does not have perpendicular magnetic anisotropy at the reproducing temperature, the magnetic coupling force from the recording layer and the reproducing layer which has become perpendicular magnetic anisotropy causes the intermediate layer to form an intermediate layer. Perpendicular magnetic anisotropy can be imparted, and the magnetization information of the recording layer can be transmitted to the reproducing layer.

The thickness of the intermediate layer is not less than the thickness of the domain wall between the reproducing layer which is the in-plane magnetized film and the recording layer which is the perpendicular magnetized film from room temperature to the reproducing temperature. Good. On the other hand, if the film thickness of the intermediate layer is too large, the total film thickness of the magnetic layer becomes large, and high recording power is required, which is not preferable. Therefore, the thickness of the intermediate layer is preferably 20 Å or more and 200 Å or less, and more preferably 50 Å or more and 150 Å or less.

Since the magneto-optical recording medium of the present invention is provided with the intermediate layer having the above characteristics, the magnetization of the reproducing layer is in-plane at room temperature as compared with the case where the reproducing layer and the recording layer are directly laminated. Easy to orient.

The Curie temperatures of the reproducing layer, the intermediate layer and the recording layer are
Each T₁, T₂, T₃And the compensation temperature of the reproducing layer is T
_complThe saturation magnetization of the reproducing layer, intermediate layer and recording layer.
M₁, M ₃And M₂And the effective perpendicular magnetic anisotropy constant
K⊥ for each₁, K⊥₃And K⊥ ₂, Perpendicular magnetic anisotropy
Ku the energy₁, Ku₃And Ku₂And here,
From the above formula I, K⊥_i(I = 1, 2 or 3) is represented by the following formula II
Represented by

[0031]

[Number 2] K⊥ _i = Ku _i -2πMs in _i ² · · · (II) a magneto-optical recording medium of the present invention, the following formula II at room temperature
I is established.

[0032]

[Formula 3] K⊥ ₃ <K⊥ ₁ << K⊥ ₂ (III) As a condition for satisfying such a relationship, for example, the following formulas IV and V are satisfied at room temperature.

[0033]

[Equation 4] Ms ₁ <Ms ₃ (IV)

[0034]

## EQU5 ## Ms ₂ <Ms ₃ (V) Further, it is necessary that the Curie temperature has a relationship represented by the following formula VI.

[0035]

## EQU6 ## RT (room temperature) <Tc ₃ << Tc ₁ ... (VI) The magneto-optical recording medium of the present invention basically has a three-layer magnetic layer structure, but the characteristics are further improved. Another magnetic layer may be provided for the purpose of improving productivity. Further, a dielectric layer, a metal layer, or the like may be provided in order to enhance the interference effect and the protection performance. Further, a metal heat conductor layer may be provided to enhance heat conduction.

Further, a small amount of elements such as Cr, Ti and Ta may be added to each layer of the magnetic layer to enhance the corrosion resistance.

The principle of the regeneration process of the present invention will be described below.

First, in the recording layer of the magneto-optical recording medium of the present invention,
The data signal is recorded as shown in FIG. Recording is performed by modulating an external magnetic field while irradiating a laser beam with a power such that the recording layer is near the Curie temperature, or
After the magnetization is aligned and erased in one direction using an initialization layer or an initialization magnetic field, laser power is modulated while applying a magnetic field in the recording direction to perform overwriting.

At this time, if the intensity of the laser beam is determined in consideration of the linear velocity of the recording medium so that only a predetermined region within the light spot is near the Curie temperature of the recording layer, the recording magnetic domain not larger than the diameter of the light spot. Can be formed, and as a result, a signal having a period equal to or shorter than the diffraction limit of light can be recorded.

At the time of data reproduction, the medium is continuously irradiated with a reproduction laser beam to detect light reflected from the medium. At this time, the temperature of the laser irradiation portion rises, the temperature distribution on the medium has a shape extending in the moving direction of the medium, and the temperature distribution is such that a part of the light spot has a high temperature.

That is, if the intensity of the laser beam during reproduction is set to be equal to or higher than the temperature Tth at which a part of the light spot shown in FIG. 8C is transferred from the in-plane magnetized film to the perpendicular magnetized film, As shown in 8 (b), in the reproducing layer and the intermediate layer, a part of the light spot becomes a perpendicular magnetization film (aperture region),
A state in which other portions remain as in-plane magnetized films (mask regions) is realized. At this time, most of the interface domain wall generated between the reproducing layer and the recording layer is generated in the intermediate layer, so that the reproducing layer stably becomes an in-plane magnetized film. The reproducing layer, which has become a perpendicularly magnetized film, is magnetically coupled to the recording layer through exchange coupling via the intermediate layer, so that the signal of the recording layer is transferred to the reproducing layer. The transferred magnetic signal is converted into an optical signal by the magneto-optical effect (Kerr rotation angle or Faraday rotation angle) of the reproducing layer and detected.

Thus, considering that the area of the high temperature portion of the light spot shown in FIG. 8A can be determined by the set intensity of the laser light, the period of the light recorded in the recording layer is equal to or less than the diffraction limit. It is possible to transfer the above signal to the reproducing layer in units of each recording mark, and as a result, it is possible to reproduce a signal having a period less than the diffraction limit of light without intersymbol interference.

Further, if the temperature distribution at the boundary between the reproduction track and the adjacent track is Tt <Tth during reproduction, the reproduction layer of the adjacent track does not become a perpendicular magnetic film. Crosstalk can be eliminated and the track density can be improved without the signal recorded in the recording layer of the adjacent track being transferred to the reproducing layer. The situation is shown in FIG.

In the above description, the case where the reproducing layer and the recording layer are magnetically coupled by the exchange interaction has been described. However, the recording layer and the reproducing layer may be magnetically coupled by magnetostatic coupling during reproduction. You may

Further, when the thermal conductivity of the medium is relatively high, the center of the temperature profile approaches the center of the light spot, and the portion near the center of the light spot becomes the aperture region as shown in FIG. Also in this case, the crosstalk with the adjacent track is similarly eliminated.

[0046]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 A target of Si, Gd, Tb, Fe, and Co was attached to a DC magnetron sputtering apparatus, and a glass substrate having a diameter of 130 mm and a polycarbonate substrate with a pre-groove were placed at a distance of 150 mm from the target. After fixing to the substrate holder installed at the position, the inside of the chamber was evacuated by a cryopump until a high vacuum of 1 × 10 ⁻⁵ Pa or less was obtained.

Ar gas was supplied to 0.4 Pa while evacuating.
After being introduced into the chamber, the SiN dielectric layer is 900Å, the GdFeCo reproducing layer is 400Å, and GdFe is
Intermediate layer is 100Å, TbFeCo recording layer is 300Å, S
An iN protective layer was deposited in the order of 700 Å to obtain a sample having the structure shown in FIG. At the time of forming each SiN layer, N ₂ gas was introduced in addition to Ar gas, and the film was formed by direct current reactive sputtering, and the mixing ratio of Ar gas and N ₂ gas was adjusted so that the refractive index was 2.1.

The composition of the GdFeCo reproducing layer is RE at room temperature.
The rich saturation magnetization Ms was set to 160 emu / cc, the compensation temperature was set to 205 ° C., and the Curie temperature was set to 300 ° C. or higher.

The composition of the GdFe intermediate layer is TM rich at room temperature, Ms is 450 emu / cc, and Curie temperature is 205.
The temperature was set to be ° C.

The composition of the TbFeCo recording layer is TM at room temperature.
The rich saturation magnetization Ms was set to 200 emu / cc and the Curie temperature was set to 220 ° C.

The sample thus formed on the glass substrate was irradiated with a semiconductor laser of 830 nm from the glass substrate side, and the external magnetic field dependence of the Kerr rotation angle (θ _K ) was measured. The measurement was performed by heating the sample from room temperature to about 200 ° C. The temperature dependence of the Kerr rotation angle (residual Kerr rotation angle; θ _K ^R ) when the external magnetic field is zero is shown by the curve (A) in the graph of FIG. From that figure, it can be seen
It can be seen that θ _K ^R is zero up to around 0 ° C., and θ _K ^R rapidly increases.

Next, the recording / reproducing characteristics were measured using this magneto-optical recording medium. N.V. of the objective lens of the evaluation device. A. Is 0.55, laser wavelength is 780 nm, recording power is 7
.About.13 mW and reproducing power within the range of 2.5 to 3.5 mW, and the C / N ratio was set to be the highest. The linear velocity was 9 m / s.

First, a carrier signal of 5 to 15 MHz was recorded on the recording layer, and the dependency of the C / N ratio on the recording mark length was examined. Next, the crosstalk was measured. The crosstalk is expressed as the difference between the reproduction signal of the land portion in which a signal having a mark length of 1.6 μm is recorded and the reproduction signal of the adjacent groove portion. The results are shown in Table 1.

Example 2 Using the same apparatus and method as in Example 1, a SiN dielectric layer was formed on a polycarbonate substrate by using
00Å, GdFeCo reproducing layer 400Å, GdFe intermediate layer 120Å, TbFeCo recording layer 300Å, SiN
A protective layer of 700 Å was formed in this order to obtain a sample having the structure of FIG. 11.

The composition of the GdFeCo reproducing layer is RE at room temperature.
The rich saturation magnetization Ms was set to 180 emu / cc, the compensation temperature was set to 220 ° C., and the Curie temperature was set to 300 ° C. or higher.

The composition of the GdFe intermediate layer was RE-rich at room temperature, Ms was 390 emu / cc, and Curie temperature was 210.
The temperature was set to be ° C.

The composition of the TbFeCo recording layer was TM at room temperature.
The rich saturation magnetization Ms was set to 200 emu / cc and the Curie temperature was set to 220 ° C.

Next, the recording / reproducing characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Embodiment 3) A SiN dielectric layer is formed on a polycarbonate substrate by the same apparatus and method as in Embodiment 1.
00Å, 400 Å GdFeCo reproducing layer, 80 Å GdFe intermediate layer, 300 Å TbFeCo recording layer, and 700 Å SiN protective layer were deposited in this order to obtain a sample having the structure shown in FIG. 11.

The composition of the GdFeCo reproducing layer is RE at room temperature.
The rich saturation magnetization Ms was set to 130 emu / cc, the compensation temperature was set to 188 ° C., and the Curie temperature was set to 300 ° C. or higher.

The composition of the GdFe intermediate layer is RE-rich at room temperature, Ms is 540 emu / cc, and Curie temperature is 200.
The temperature was set to be ° C.

The composition of the TbFeCo recording layer was TM at room temperature.
The rich saturation magnetization Ms was set to 200 emu / cc and the Curie temperature was set to 220 ° C.

Next, the recording / reproducing characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Embodiment 4) A SiN dielectric layer is formed on a polycarbonate substrate by the same apparatus and method as in Embodiment 1.
A sample having the structure shown in FIG. 11 was obtained by sequentially depositing 00Å, a GdFeCo reproducing layer of 400Å, a GdFe intermediate layer of 90Å, a TbFeCo recording layer of 300Å and a SiN protective layer of 700Å.

The composition of the reproduction layer of GdFeCo is RE at room temperature.
The rich saturation magnetization Ms was set to 130 emu / cc, the compensation temperature was set to 188 ° C., and the Curie temperature was set to 300 ° C. or higher.

The composition of the GdFe intermediate layer is RE-rich at room temperature, Ms is 480 emu / cc, and Curie temperature is 21.
The temperature was set to 5 ° C.

The composition of the TbFeCo recording layer was TM at room temperature.
The rich saturation magnetization Ms was set to 200 emu / cc and the Curie temperature was set to 220 ° C.

Next, the recording / reproducing characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1) Using the same apparatus and method as in Example 1, a SiN dielectric layer of 900 Å, G
400 Å dFeCo reproducing layer and 4 TbFeCo recording layer
00Å and a SiN protective layer of 700Å were deposited in this order to obtain a magneto-optical recording medium having the structure of FIG. The refractive index of each SiN layer was 2.1.

The composition of the reproducing layer of GdFeCo is RE at room temperature.
The rich saturation magnetization was set to 130 emu / cc, the compensation temperature was set to 188 ° C., and the Curie temperature was set to 300 ° C. or higher.

The composition of the TbFeCo recording layer was TM at room temperature.
The saturation magnetization was set to 200 emu / cc and the Curie temperature was set to 220 ° C.

For this magneto-optical recording medium sample, the temperature dependence of the residual Kerr rotation angle θ _K ^R was measured in the same manner as in Example 1. The results are shown by the curve (R1) in the graph of FIG.

Comparing the results with Example 1 (curve (A)), the magneto-optical recording medium of Example 1 was maintained at a low temperature near room temperature while maintaining a state of a perpendicular magnetization film at high temperature. It can be seen that the in-plane magnetic anisotropy is improved.

Next, using this magneto-optical recording medium, recording and reproducing characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 Using the same apparatus and method as in Example 1, 9 SiN dielectric layers were formed on a polycarbonate substrate.
00Å, GdFeCo reproduction layer 400Å, TbFeCo
A recording layer of 400 Å and a SiN protective layer of 700 Å were formed in this order to obtain a magneto-optical recording medium. The refractive index of each SiN layer was 2.1.

The composition of the GdFeCo reproducing layer is RE at room temperature.
The rich saturation magnetization was set to 180 emu / cc, the compensation temperature was set to 220 ° C., and the Curie temperature was set to 300 ° C. or higher.

The composition of the TbFeCo recording layer was TM at room temperature.
The saturation magnetization was set to 200 emu / cc and the Curie temperature was set to 220 ° C.

Next, using this magneto-optical recording medium, recording and reproducing characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 Using the same apparatus and method as in Example 1, 9 SiN dielectric layers were formed on a polycarbonate substrate.
00Å, GdFeCo reproduction layer 400Å, TbFeCo
A recording layer of 400 Å and a SiN protective layer of 700 Å were formed in this order to obtain a magneto-optical recording medium. The refractive index of each SiN layer was 2.1.

The composition of the GdFeCo reproducing layer was RE at room temperature.
The rich saturation magnetization was set to 270 emu / cc, the compensation temperature was set to 280 ° C., and the Curie temperature was set to 300 ° C. or higher.

The composition of the TbFeCo recording layer was TM at room temperature.
The saturation magnetization was set to 200 emu / cc and the Curie temperature was set to 220 ° C.

Next, using this magneto-optical recording medium, recording and reproducing characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.

[0084]

[Table 1] From Table 1, comparing the characteristics of the magneto-optical recording media of the present invention of Examples 1 to 4 with the characteristics of the conventional magneto-optical recording media of Comparative Examples 1 to 3, it can be seen that the ones of the present invention have a short mark length. C /
It can be seen that the N ratio and crosstalk are greatly improved.

[0085]

By using the magneto-optical recording medium and the reproducing method of the present invention, it is possible to reproduce a magnetic domain smaller than the beam spot system by using a simple device (conventional device) without an initializing magnet, and crosstalk. Therefore, it is possible to achieve high-density recording in which the linear recording density and the track density are significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic layer structure of a magnetic layer of a magneto-optical recording medium of the present invention.

FIG. 2 is a schematic diagram showing a magnetic super-resolution effect of a two-layered magneto-optical recording medium using an in-plane magnetized film.

FIG. 3 is a schematic diagram showing in detail the magnetization direction of the recording medium of FIG.

FIG. 4 is a graph showing the temperature characteristics of Ms of the reproducing layer of the magneto-optical recording medium of the present invention.

FIG. 5 is a graph showing an example of the relationship between the demagnetizing field energy 2πMs ² and the perpendicular magnetic anisotropy energy Ku of the reproducing layer of the magneto-optical recording medium of the present invention.

FIG. 6 is a schematic diagram showing a state of the magnetization direction of the magneto-optical recording medium of the present invention, (a) showing a state from room temperature to a reproducing temperature, and (b) showing a state at a reproducing temperature. FIG.

FIG. 7 is a cross-sectional view showing an example of the state of the magnetization direction at room temperature after recording on the recording layer of the optical recording magnetic medium of the present invention.

FIG. 8 is a diagram showing an example of a reproducing method of the magneto-optical recording medium of the present invention, FIG. 8A is a diagram showing a mask region and an aperture region in a light spot on the medium plate surface, and FIG. Is a diagram showing a magnetization direction state of each layer, and (c) is a graph showing a temperature distribution in a track direction.

FIG. 9 is a schematic diagram showing a mark detection state during reproduction of the magneto-optical recording medium of the present invention.

FIG. 10 is a diagram showing another example of the reproducing method of the magneto-optical recording medium of the present invention, FIG. 10 (a) is a diagram showing a mask region and an aperture region in a light spot on the medium plate surface, and FIG. )
Is a diagram showing a magnetization direction state of each layer, and (c) is a graph showing a temperature distribution in a track direction.

FIG. 11 is a cross-sectional view showing the layer structure of the magneto-optical recording medium of the present invention of Examples 1 to 4.

12 is a graph showing the temperature dependence of the residual Kerr rotation angle (θ _K ) in Example 1 and Comparative Example 1. FIG.

FIG. 13 is a cross-sectional view showing the layer structure of magneto-optical recording media of Comparative Examples 1 to 3.

Claims (3)

[Claims] 1. A first magnetic layer at least from the light incident side,
A third magnetic layer and a second magnetic layer are laminated on the substrate in this order, and the first magnetic layer is an in-plane magnetized film at room temperature and a perpendicular magnetized film between room temperature and the Curie temperature of the third magnetic layer. The second magnetic layer is a perpendicularly magnetized film, and the Curie temperature of the third magnetic layer is the first magnetic layer and the second magnetic layer.
A magneto-optical recording medium, which is lower than any Curie temperature of the magnetic layer and in which the in-plane anisotropy of the third magnetic layer at room temperature is larger than the in-plane anisotropy of the first magnetic layer at room temperature. 2. The saturation magnetization of the third magnetic layer at room temperature is the first
The magneto-optical recording medium according to claim 1, wherein the saturation magnetization of the magnetic layer is larger than that at room temperature. 3. The magneto-optical recording medium according to claim 1, wherein the first magnetic layer and the third magnetic layer are irradiated with a light spot to form a part of the light spot as a perpendicular magnetization film. (2) An information reproducing method in which information is reproduced by orienting in a stable direction with respect to the magnetization direction according to the information of the magnetic layer and changing the magneto-optical effect of the reflected light of the light spot.