JPH09115196A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium of a high density with which a high C/N is obtd. and reproduction of short recording marks is possible as well when a laser beam of 400 to 550nm is used as reproducing light. SOLUTION: A dielectric layer 2, a reproducing magnetic layer 3 consisting of multilayered films of Pt/Co which are perpendicularly magnetized films, a nonmagnetic layer 4 and a recording magnetic layer 5 which is a perpendicularly magnetized film having a Curie temp. lower than the Curie temp. of the reproducing magnetic layer 3 and high coercive force are laminated in this order on a transparent substrate 1. The layer thickness of the reproducing magnetic layer 3 is in the range of 15 to 30nm, the layer thickness of the nonmagnetic layer in the range of 2 to 10nm and the layer thickness of the recording magnetic layer 5 in the range of 50 to 250nm. In addition, the reproducing magnetic layer 3 and the recording magnetic layer 5 are magnetostatically coupled.

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,
In particular, the present invention relates to a magneto-optical recording medium having a high density by magnetic super-resolution (hereinafter referred to as MSR).

[0002]

2. Description of the Related Art Conventionally, as a large-capacity information recording medium, a read-only optical recording medium (reproduction-only optical disk) for recording information in concave and convex pits, a magneto-optical recording medium (magneto-optical disk) for recording in the magnetization direction, etc. Are known. recent years,
With the increase in the density of these recording media, the wavelength of laser light used when reproducing recorded information is becoming shorter.

For example, in the case of the above read-only optical recording medium,
The reproduction output is the wavelength λ of the laser light source and the numerical aperture N of the objective lens.
Since a high-density recording signal exceeding λ / (2NA) cannot be reproduced depending on A, attempts have been made to shorten the wavelength of the laser light source and increase the NA.

On the other hand, in a magneto-optical recording medium, a magnetic super-resolution magneto-optical recording medium (hereinafter referred to as an MSR magneto-optical recording medium) is used in order to improve the resolution at the time of reproducing the recording medium having a high density. It has been known. This method uses a magneto-optical recording medium having a multilayer magnetic film structure formed by stacking a recording magnetic layer and a reproducing magnetic layer, and at the time of reproducing information recorded on the medium, the temperature generated in the light spot of the laser beam irradiated on the recording medium. The distribution is used to detect the presence or absence of a recording mark at a specific portion within the spot.

One of the above MSR magneto-optical recording media is, for example, Japanese Patent Laid-Open No. 3-88156 or Proceeding.
s of the First Magneto-Electronics Internatio
na Symposium, p139 (1994), J.Magn.Soc.jpn., Vol.19, Su
A magnetostatic coupling type MSR magneto-optical recording medium shown in pplement No. S1, p421 (1995) is known.

In this method, the magnetization state of the reproducing magnetic layer is first magnetized (initialized) in one direction by an initializing external magnetic field, and the recording magnetization of the recording magnetic layer is recorded on the reproducing magnetic layer heated by the laser beam during reproduction. Information is transferred by a magnetostatic magnetic field from the recording magnetic layer, and the recording magnetization information transferred to the reproducing magnetic layer is read out by the Kerr effect. The first proposed exchange-coupling type MSR magneto-optical recording medium. (For example, MSR of front opening detection (FAD), rear opening detection (RAD)
The initializing external magnetic field can be made smaller than that of a magneto-optical recording medium, and the recording density can be improved because the crosstalk is small.

In the magnetostatic coupling type MSR magneto-optical recording medium disclosed in Japanese Patent Laid-Open No. 3-88156, the stray magnetic field based on the magnetization of the recording magnetic layer is used to write the recording magnetization information of the recording magnetic layer to the reproducing magnetic layer. It is to be transcribed. Here, since the stray magnetic field from the recording magnetic layer is weak, the coercive force H of the reproducing magnetic layer is
The smaller c is better. Further, in order to obtain a good C / N, the material of the reproducing magnetic layer is preferably a material having a high Curie point Tc and a large curl rotation angle. The material of the reproducing magnetic layer satisfying the above conditions has Tc of 250 ° C.
Above, GdFeCo having Hc of 500 [Oe] or less is mentioned.

Further, as a condition for the recording magnetization information of the recording magnetic layer to be transferred to the reproducing magnetic layer, a stray magnetic field Hl and a demagnetizing field Hd of the reproducing magnetic layer based on the magnetization from the recording magnetic layer given to the reproducing magnetic layer. , It is reported that the transfer assisting magnetic field Hr during reproduction and the coercive force Hc of the reproducing magnetic layer must satisfy the relationship of Hl + Hr + Hd = Hc (1) at the temperature during irradiation of reproducing light. There is. However, even if the above equation (1) is satisfied, the saturation magnetic field H
When s is larger than the coercive force Hc of the reproducing magnetic layer, the recording magnetization information of the recording magnetic layer is not completely transferred to the reproducing magnetic layer.

Also, the literature Proceedings of the First M
agneto-Electronics InternationaSymposium, p139 (199
4) and J. Magn. Soc. Jpn., Vol. 19, Supplement No. S1, p421 (1
995) also uses GdFeC as a material for the reproducing magnetic layer.
It is reported that a high C / N of about 45 dB can be obtained with a recording pit of 0.5 μm using a laser light source having a wavelength of 780 nm. However, if the recording pit is 0.3 μm or less, the C / N becomes lower than 40 dB and a sufficient C / N cannot be obtained.

That is, the shorter the wavelength of GdFeCo is, the smaller the wavelength of 550 nm, especially the smaller the rotation angle of the car. Therefore, when reproduction is performed using a short wavelength laser light source having a wavelength of 550 nm or less, the reproduction signal output decreases. , Sufficient C / N
Can not be obtained. Therefore, the wavelength of 400 ~ 550nm band blue ~
When performing MSR reproduction using a green laser light source, in order to obtain a sufficient C / N with a signal having a short recording mark length, for example, a recording mark length of 0.45 μm or less, wavelengths of 400 to 550 are required.
It is necessary to use a material having a large rotation angle in the nm band for the reproducing magnetic layer.

By the way, a Pt / Co multilayer film is known as a material capable of obtaining a high curve rotation angle at a wavelength of 400 to 550 nm. In this Pt / Co multilayer film, Hc can be set to 500 [Oe] or less by the film forming method, and the required characteristics as a reproducing magnetic layer described in JP-A-3-88156 and (1) It is possible to satisfy the relation of the formula. However, in a magnetostatic coupling type MSR magneto-optical recording medium using a Pt / Co multilayer film having conventionally known film characteristics as a reproducing magnetic layer, a high C / N can be obtained even if the above expression 1 is satisfied. There wasn't. Where high C /
The reason why N is not obtained is that the Pt / Co multilayer film has a large anisotropic dispersion, and thus the recording magnetization information of the recording magnetic layer is not completely transferred to the reproducing magnetic layer.

Next, with respect to the MSR magneto-optical recording medium satisfying the above expression 1, the case where a high C / N is obtained and the case where it is not obtained will be described with reference to FIG. FIG. 5 shows a Kerr loop of a typical perpendicular magnetization film, and the magnitude of the applied magnetic field at each point on the Kerr loop shown in FIG. 5 is a nucleation magnetic field Hn, a coercive force Hc, and a saturation magnetic field Hs, respectively. At this time, when GdFeCo is used for the reproducing magnetic layer, a curve having a very good squareness is obtained, so that Hn≈Hc
≈Hs <200 [Oe], and a high C / N can be obtained by satisfying the expression (1). However, Pt / Co
Since the multilayer film has a larger anisotropic dispersion than the GdFeCo film, Hs is 1 [kO] even when Hc is 500 [Oe] or less.
e] or higher, and even if the expression (1) is satisfied, the recording magnetization information of the recording magnetic layer is not completely transferred to the reproducing magnetic layer, and as a result, C / N is lowered.

Therefore, when Hc.apprxeq.Hs is not satisfied as in the case where the Pt / Co multilayer film is used as the reproducing magnetic layer, the relationship of Hl + Hr + Hd = Hs (2) is satisfied at the reproducing light irradiation temperature. Need to meet. If Hs is extremely large, it is difficult to satisfy the formula (2). Therefore, when a Pt / Co multilayer film is used as the reproducing magnetic layer, the H of the reproducing magnetic layer is increased.
It is necessary to reduce s and improve the squareness of the curl.

[0014]

As described above,
In the MSR magneto-optical recording medium using GdFeCo in the reproducing magnetic layer, the Kerr rotation angle decreases when a laser light source of 400 to 550 nm is used as reproducing light, and Pt /
In the MSR magneto-optical recording medium having the Co multilayer film, the recording magnetization information of the recording magnetic layer cannot be completely transferred to the reproducing magnetic layer, and in any case, high C / N cannot be obtained.

Therefore, in the present invention, Pt is used as the reproducing magnetic layer.
In an MSR magneto-optical recording medium using a Co / Co multilayer film,
By reducing the Hs of the reproducing magnetic layer and improving the squareness of the curl, a high C / N can be obtained when laser light of 400 to 550 nm is used as the reproducing light. It is an object of the present invention to provide a magneto-optical recording medium, and as a result, it is possible to provide a high-density magneto-optical recording medium capable of reproducing short recording marks of 0.45 μm or less.

Incidentally, Pt / C is disclosed in Japanese Patent Laid-Open No. 7-141709.
o A magneto-optical recording medium characterized by using a multilayer film as a reproducing magnetic layer is disclosed. However, the present invention has an in-plane magnetization state at room temperature between the reproducing magnetic layer and the recording magnetic layer,
It has a structure in which an intermediate magnetic layer that becomes perpendicularly magnetized when the temperature rises is provided, and the magnetization information of the recording magnetic layer is transferred to the reproducing magnetic layer by the exchange coupling force via the intermediate magnetic layer during reproduction light irradiation. It is transcribed. Therefore, the magneto-optical recording medium according to the present invention is completely different from the magnetostatic coupling type MSR magneto-optical recording medium in which a non-magnetic layer is provided between the reproducing magnetic layer and the recording magnetic layer.

In addition, reference J. Magn. Soc. Jp
n. , Vol. 17, Supplement S1 (19
93), pp. 171-174, a Pt / Co multilayer film is used, and an optical modulation direct over write using magnetostatic coupling has been reported. The magneto-optical recording medium reported in this document is a Pt / Co multilayer. The film is used as a recording layer, which is completely different from the magneto-optical recording medium using the Pt / Co multilayer film according to the present invention as a reproducing magnetic layer.

[0018]

A magneto-optical recording medium according to claim 1 is a magneto-optical recording medium having a dielectric layer, a reproducing magnetic layer comprising a Pt / Co multilayer film as a perpendicular magnetization film, and a non-magnetic layer on a transparent substrate. In a magneto-optical recording medium in which a recording magnetic layer which is a perpendicular magnetic film having a Curie temperature and a high coercive force lower than that of the reproducing magnetic layer is laminated in this order, the reproducing magnetic layer has a layer thickness of 1
In the range of 5 to 30 nm, the thickness of the non-magnetic layer is 2 to 10 nm
The layer thickness of the recording magnetic layer is in the range of 50 to 250 nm, and the reproducing magnetic layer and the recording magnetic layer are magnetostatically coupled.

A magneto-optical recording medium according to a second aspect of the present invention is the magneto-optical recording medium according to the first aspect, wherein the saturation magnetic field Hs of the reproducing magnetic layer satisfies Hs ≦ 500 [Oe] at room temperature. It is characterized by that.

The magneto-optical recording medium according to the present invention has a large Kerr rotation angle when a reproducing light having a short wavelength of 550 nm or less is used with the above structure. Further, by making the saturation magnetic field Hs smaller than that of the conventional reproducing magnetic layer made of a Pt / Co multilayer film, the magnetization of the recording magnetic layer can be satisfactorily transferred to the reproducing magnetic layer during reproduction. Therefore, a high C / N is obtained when a laser beam having a short wavelength is used as the reproduction light.

[0021]

【Example】

[Structure of Magneto-Optical Recording Medium According to the Present Invention and Reproducing Method] Hereinafter, the structure of the magneto-optical recording medium according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows the structure of a magneto-optical recording medium according to the present invention. In FIG. 1, a reproducing magnetic layer 3, a non-magnetic layer 4 and a recording layer are formed on a substrate 1 via a first dielectric layer 2. The magnetic layer 5 is laminated, and the reproducing magnetic layer 3 and the recording magnetic layer 5 are provided so as to be magnetostatically coupled via the nonmagnetic layer 4. Further, a dielectric layer 6 may be provided as a protective layer on the recording magnetic layer 5.

Information is recorded on this magneto-optical recording medium by a usual method. That is, the semiconductor laser light is irradiated in a state where a predetermined external magnetic field is applied to locally form a recording mark and information is recorded. In the following description, the case of the light modulation type will be described, but the same effect can be obtained also in the case of the magnetic field modulation type.

Next, a reproducing method of the magneto-optical recording medium in which the information is recorded as described above, that is, a recording mark detecting method will be described with reference to FIG. In the figure,
(A) is a plan view of a portion irradiated with reproduction light, and (b) is a sectional view thereof.

In FIG. 2A, 11 is a light spot which is a portion irradiated with reproducing light, 12 is a high temperature portion where transfer is performed, and 21 to 26 are recordings formed on the recording magnetic layer. Indicates the mark. Here, since the light spot 11 moves in the D1 direction, the high temperature portion 12 shifts to the rear of the light spot 11 (back side in the traveling direction). Further, (b) shows the magnetization directions of the reproducing magnetic layer 34 and the recording magnetic layer 5. Here, when the direction from the reproducing magnetic layer 3 to the recording magnetic layer 5 is called downward, and the direction from the recording magnetic layer 5 to the reproducing magnetic layer 3 is upward, a recording mark is formed in the recording magnetic layer 5. The open part is magnetized upward.

When reproducing information recorded on the magneto-optical recording medium according to the present invention, an initializing magnetic field 7 is applied to the reproducing magnetic layer 3 to align the magnetization of the reproducing magnetic layer 3 in one direction. . For example, in FIG. 2B, the magnetization of the reproducing magnetic layer 3 is aligned downward during initialization.

When the reproducing light is irradiated to the portion where the magnetization of the reproducing magnetic layer 3 is initialized downward as described above, the temperature of the portion is increased and the temperature is kept at a constant temperature (hereinafter, this temperature is It becomes to T ₁ hereinafter) or more, the magnetization of the recording magnetic layer 5 is transferred to the reproducing magnetic layer 3. Here, T ₁ is 100 to
The temperature is 130 ° C. and the temperature is T ₁ when irradiated with the reproducing light.
The higher portion corresponds to the high temperature portion 12.
At this time, the transfer auxiliary magnetic field 8 (Hr) is applied to the portion irradiated with the reproduction light in the upward direction of the recording mark.

Then, when the magnetization of the recording magnetic layer 5 is transferred to the reproducing magnetic layer 3, depending on the direction of the transferred magnetization,
The polarization plane of the reflected light of the irradiated reproduction light rotates. Therefore, the presence or absence of the recording mark recorded on the recording magnetic layer 5 can be detected by detecting the curve rotation angle which is the rotation amount of the polarization plane.

Here, even within the light spot 11, the magnetization of the recording magnetic layer 5 is not transferred to the reproducing magnetic layer 3 in the portion where the temperature is lower than T ₁ , and that portion acts as a mask, so that the light spot It is possible to detect only the presence or absence of the recording mark in the overlapping portion of 11 and the high temperature portion 12 whose temperature is higher than T ₁ . That is, even if the recording mark 24 and the recording mark 25 are present in the light spot 11, only the recording mark 25 is detected.

In order to prevent the information recorded in the recording magnetic layer 5 from being destroyed by the initializing magnetic field for initializing the magnetization of the reproducing magnetic layer, the coercive force of the reproducing magnetic layer 3 is set to H.
c ₁ , the coercive force of the recording magnetic layer 5 is Hc ₂ , and the initializing magnetic field Hi is
ni needs to satisfy the condition of Hc ₁ <Hini <Hc ₂ ... (3) at room temperature.

In order to transfer the magnetization of the recording magnetic layer 5 to the reproducing magnetic layer 3 at the portion where the temperature becomes T ₁ or more during irradiation of the reproducing light, the recording magnetic layer 5 provided to the reproducing magnetic layer 3 is required.
Magnetic field Hl based on the magnetization of the magnetic field, demagnetizing field H of the reproducing magnetic layer 3
d, transfer assisting magnetic field Hr, saturation magnetic field Hs of the reproducing magnetic layer 3
Must satisfy the condition of Hr + Hl + Hd = Hs ... (4) at the temperature T _1, and the condition of Hr + Hl + Hd> Hs (5) at T> T ₁ .

Here, the leakage magnetic field Hl from the recording magnetic layer 5
Is about 400 [Oe], and the demagnetizing field Hd of the reproducing magnetic layer 3 is about 50 to 150 [Oe]. Also, the transfer assisting magnetic field Hr
Is preferable from the aspect of drive miniaturization,
Usually, it is set to about 100 [Oe]. Therefore, the saturation magnetic field Hs of the reproducing magnetic layer 3 is 500 Oe at the temperature T _1.
It is desirable to make the following.

Next, each layer constituting the magneto-optical recording medium according to the present invention will be described.

In the magneto-optical recording medium according to the present invention,
A polymer resin substrate such as polycarbonate or a glass substrate is usually used as the substrate 1, and a first dielectric layer 2, a reproducing magnetic layer 3, a non-magnetic layer 4, and a recording magnetic layer are formed on the substrate 1. 5
Is provided.

The first dielectric layer 2 functions as an enhancement layer for the car effect, and is made of SiN, LaSiON, Al.
Materials such as N and ZnO can be used. Further, the surface property of the first dielectric layer 2 is not particularly limited, but if the surface property is poor, the anisotropic dispersion of the Pt / Co multilayer film provided on the dielectric layer becomes large and the saturation magnetic field Hs is increased. It becomes as large as 1 [kOe] or more, and as a result, the magnetization information of the recording magnetic layer 5 cannot be satisfactorily transferred to the reproducing magnetic layer 3. Therefore, the surface roughness Ra of the first dielectric layer 2 is preferably 5 nm or less, more preferably 2 nm or less.

The dielectric layer 2 having a small surface roughness Ra is
If the substrate 1 is flat, it can be easily produced, but even if the surface property of the substrate 1 is poor, the surface of the produced dielectric layer is reverse-sputtered, or a nitrogen ion beam is formed by an ion beam sputtering method or a helicon sputtering method. It can be obtained by forming a film by sputtering Si or silicon nitride while assisting the sputtering.

The reproducing magnetic layer 3 is composed of a Pt / Co multilayer film, and its thickness is preferably set in the range of 15 to 30 nm. Here, when the film thickness of the Pt / Co multilayer film becomes thinner than 15 nm, the nucleation magnetic field Hn, the coercive force Hc, the saturation magnetic field H
s becomes Hn≈Hc≈Hs <500 [Oe], and the squareness of the curl is improved, but the recording magnetic layer 5 influences the curling effect of the reproducing magnetic layer during reproduction, and The noise becomes loud. Also, when the film thickness of the Pt / Co multilayer film becomes thicker than 30 nm, the Hs of the Pt / Co multilayer film itself becomes 500.
Since it is larger than [Oe], the magnetic field cannot be transferred to the reproducing magnetic layer 3 by the leakage magnetic field from the recording magnetic layer 5.

Further, regarding the Pt film and the Co film forming the Pt / Co multilayer film, the film thickness of the Pt film is 0.5 to 2.5 nm,
The film thickness of the Co film is preferably set in the range of 0.3 to 0.6 nm. If the thickness of the Pt film is less than 0.5 nm, a perpendicular magnetization film having good curl squareness cannot be obtained.
If the thickness is more than 2.5 nm, the car rotation angle decreases. Also, C
If the film thickness of the o film is smaller than 0.3 nm, the curl rotation angle is reduced, and if it is larger than 0.6 nm, a perpendicular magnetized film having good curl squareness cannot be obtained.

Therefore, in order to obtain a high C / N, the film thickness of the Pt / Co multilayer film which becomes the reproducing magnetic layer 3 is 15 to 30.
The thickness of the Pt film forming the Pt / Co multilayer film is 0.5 to 2.5 nm, and the film thickness of the Co film is 0.3 to 0.6 nm. Must be set.

The non-magnetic layer 4 provided on the reproducing magnetic layer 3 includes
Materials such as SiN and AlN can be used, and the layer thickness thereof is preferably set in the range of 2 to 10 nm. Here, if the thickness of the non-magnetic layer 4 is less than 2 nm, the exchange coupling force between the recording magnetic layer 5 and the reproducing magnetic layer 3 cannot be completely cut off, so that the Hc of the reproducing magnetic layer 3 becomes large, and With the leakage magnetic field Hl, the recording magnetization information of the recording magnetic layer 5 cannot be transferred to the reproducing magnetic layer 3. When the thickness of the non-magnetic layer 4 is thicker than 10 nm, the leakage magnetic field Hl from the recording magnetic layer 5 becomes small, so that the magnetization information of the recording magnetic layer 5 cannot be completely transferred to the reproducing magnetic layer 3. Therefore, in order to properly transfer the magnetization information of the recording magnetic layer 5 to the reproducing magnetic layer 3, it is necessary to set the layer thickness of the nonmagnetic layer 4 in the range of 2 to 10 nm.

The recording magnetic layer 5 provided on the non-magnetic layer 4 has a high coercive force at room temperature and a temperature of irradiation with reproducing light so that the recorded magnetization does not change due to an external magnetic field. A material having a relatively high Curie temperature so that the magnetization does not change when the temperature rises, for example, a Curie temperature of 25
It is preferable to use TbFeCo at 0 ° C. or higher.
Further, the recording magnetic layer 5 is required to generate a leakage magnetic field Hl of a sufficient magnitude to transfer the magnetization information to the reproducing magnetic layer 3, and therefore, it is desirable that the recording magnetic layer 5 has a large magnetization at the temperature when the reproducing light is irradiated.

Therefore, the recording magnetic layer 5 is made of a material having a transition metal sublattice magnetization dominant at room temperature and has a layer thickness of 50 to 25.
It is preferable to set in the range of 0 nm. Here, if the layer thickness of the recording magnetic layer 5 is thinner than 50 nm, the leakage magnetic field Hl becomes small, so that good transfer cannot be performed, and if it is thicker than 250 nm,
It is not preferable because it is necessary to increase the power of the laser beam applied during recording.

Next, a method of manufacturing the photomagnetization recording medium according to the present invention will be described.

Pt / used in the reproducing magnetic layer 3 according to the present invention
The Co multi-layer film has a small anisotropic dispersion, and Hs ≦ 500 [O
e] It is necessary for the film to satisfy 1 ≦ (Hs / Hc) ≦ 2. If Hs is larger than 500 [Oe], good transfer cannot be performed, and if Hs / Hc is larger than 2, noise increases. However, good C / N cannot be obtained.

In order to satisfy this condition, a Pt film and a C
When the Pt / Co multilayer film is formed by alternately stacking the o films, it is necessary to make the interface between the Pt film and the Co film flat and reduce the anisotropic dispersion.

For example, when a Pt / Co multilayer film is produced by a sputtering method or a vapor deposition method, a film having a flat interface can be obtained if the flying particles deposited on the substrate have relatively high energy. That is, when the energy of particles is high, a flat interface is formed by the migration effect when the particles are deposited on the substrate.

Therefore, it is desirable that the Pt / Co multilayer film is formed by a sputtering method having a high particle energy, and it is more desirable that the sputtering pressure is on the order of 10 ⁻⁴ Torr or less.
Here, if the sputtering pressure during film formation is higher than 10 ⁻³ Torr, the sputtered particles collide with sputtered gas particles to lower the particle energy, resulting in energy of several eV on the substrate surface. , Sputter pressure 10 ⁻⁴
Below the Torr level, particles having sufficient energy to cause the migration effect adhere to the substrate, so that a multilayer film having a flat interface can be formed. Incidentally, as a method capable of sputtering at a level of 10 ⁻⁴ Torr or less, there are an ion beam sputtering method, a helicon sputtering method and the like, but other methods can be used as long as the film can be formed at a sputtering pressure of 10 ⁻⁴ Torr or less. It may be.

By using the Pt / Co multilayer film thus obtained as the reproducing magnetic layer 3, a wavelength of 550 nm is obtained.
When reproduced using the following short wavelength laser, a large reproduction output is obtained.

Example 1 A case where a magneto-optical disk having a sectional structure as shown in FIG. 3 is manufactured as a magneto-optical recording medium according to the present invention will be described. The magneto-optical disk of this example was manufactured using a multi-source ion beam sputtering device and a DC / RF sputtering device.

First, the polycarbonate substrate 9 is set in the ion beam sputtering apparatus, and the first dielectric layer 2, the reproducing magnetic layer 3 and the nonmagnetic layer 4 are continuously formed while rotating the substrate. The steps will be described.

Here, on the surface of the polycarbonate substrate 9, optical head guide grooves, pits indicating addresses, etc. are provided in advance. In this embodiment, a polycarbonate substrate 9 having a track pitch of 0.8 μm, a groove width of 0.26 μm and a groove depth of 48 nm was used. First dielectric layer: Ar ion beam Depending on the film, a Si target is sputtered under the following film forming conditions, and at the same time, the polycarbonate substrate 9
A nitrogen ion beam was assisted by an assist ion gun to form a first dielectric layer 2 of silicon nitride having a layer thickness of 60 nm on the surface of.

Main ion gun: Beam voltage 1200V Beam current 135mA Ar gas flow rate 10SCCM Assist ion gun: Beam voltage 350V Beam current 10mA Nitrogen gas flow rate 20SCCM Sputtering pressure: 3.6 × 10 ⁻⁴ Torr Deposition rate: 0.25 nm / sec reproducing magnetic layer: Kr ion beam was used under the following film forming conditions.
A Pt film with a thickness of 2 nm and a Co film with a thickness of 0.5 nm are alternately laminated by alternately sputtering a Pt target and a Co target to reproduce a Pt / Co multilayer film with a layer thickness of 20 nm. The magnetic layer 3 was formed.

Sputtering gas: Kr 10 SCCM Sputtering gas pressure: 1.4 × 10 ⁻⁴ Torr Beam voltage: 300 V Beam current: 30 mA Film forming rate: Pt 0.02 nm / sec Co 0.02 nm / sec Nonmagnetic layer: The non-magnetic layer 4 made of silicon nitride and having a layer thickness of 10 nm was formed under the same conditions as in the case of the first dielectric layer 2 (the same film forming conditions as the silicon nitride film of the first dielectric layer 2).

Then, as described above, the first dielectric layer 2,
A process of setting the polycarbonate substrate 9 on which the reproducing magnetic layer 3 and the non-magnetic layer 4 are formed in another sputtering apparatus and continuously forming the recording magnetic layer 5 and the third dielectric layer 6 will be described.

Recording magnetic layer: Before forming the recording magnetic layer 5, reverse sputtering was performed so that the nonmagnetic layer 4 had a thickness of 5 nm.
After that, TbFe was formed by DC sputtering under the following film forming conditions.
A recording magnetic layer 5 made of CoCr and having a layer thickness of 100 nm was formed. In this example, a TbFeCoCr film added with Cr is used to improve the corrosion resistance of the recording magnetic layer 5.

Target: Tb ₁₉ Fe ₆₁ Co _17.5 Cr _2.5 Sputtering gas: Ar 100 SCCM Sputtering gas pressure: 1.5 × 10 ⁻³ Torr Input power: 1000 W Deposition rate: 20 nm / min Second dielectric Body layer: A second dielectric layer 6 made of silicon nitride and having a layer thickness of 40 nm was formed by the RF sputtering method under the following film forming conditions.

Target: Si Sputtering gas: Ar 30SCCM + Nitrogen 20SCCM Sputtering gas pressure: 1 × 10 ⁻³ Torr Input power: 1000 W Deposition rate: 8 nm / min Polycarbonate substrate 9 deposited as above,
It was taken out from the chamber, and an ultraviolet curable resin film as a protective film 9 was formed to a thickness of about 10 μm to obtain a magneto-optical disk.

In order to examine the film characteristics of the manufactured magneto-optical disk, the curves (coercive force Hc, saturation magnetic field Hs, Hs / Hc of the reproducing magnetic layer 3) of the reproducing magnetic layer 3 and the recording magnetic layer 5 at a wavelength of 680 nm were used. The Kerr rotation angle and the coercive force Hc) of the recording magnetic layer were examined, and the results are shown in Table 1. In this measurement, a disk having a film formed under the same conditions except that the protective film 9 was not formed was used. When measuring the curve of the reproducing magnetic layer 3, laser light was irradiated from the substrate side. When measuring the curl of the recording magnetic layer 5,
The film was irradiated with laser light from the film surface side.

As shown in Table 1, for the reproducing magnetic layer 3, Hs = 160 [Oe], Hc = 150 [Oe], θk.
= 0.4 [deg] and Hs / Hc = 1.07, and a curl with good squareness as shown in FIG. 4 was obtained. For the recording magnetic layer 5, Hc = 11 [kOe]
A curl with a squareness ratio of 1 was obtained. Note that, here, Hs and Hc were measured at room temperature (about 20 ° C.), but if Hs ≦ 500 [Oe] at room temperature, the temperature during reproduction light irradiation, that is, Hs at T ₁ ≦ 500 [Oe], and good transfer can be performed.

The recording / reproducing characteristics of the manufactured magneto-optical disk were examined as follows.

First, using a semiconductor laser having a wavelength of 680 nm, a linear velocity of 7.4 m / sec, a recording magnetic field of 24 kA / m, a recording light power of 9 mW, recording frequencies of 8.22 MHz and 12.33 MHz and a length of 0. Recording marks of 45 μm and 0.3 μm were formed.

Next, before reproducing, the magnetization of the reproducing magnetic layer 3 was initialized in a fixed direction with an initializing magnetic field of 40 kA / m, and then a reproducing light power of -4 m was used by using a semiconductor laser having a wavelength of 680 nm.
Playback with W and transfer assist magnetic field 8 kA / m, C / at that time
N was measured. As shown in Table 1, C / N = 41 dB when the mark length was 0.45 μm, and C / N = 35 dB when the mark length was 0.3 μm.

Similarly, the recorded signal was reproduced using an Ar laser having a wavelength of 524 nm with a reproducing light power of -3 mW and a transfer assisting magnetic field of 8 kA / m, and the C / N at that time was measured. As a result, as shown in Table 1, C / N = 45 dB when the mark length was 0.45 μm, and C / N = 42 dB when the mark length was 0.3 μm.

As can be seen from the above C / N measurement result, the mark length of 0.45 μm is +4 dB, and the mark length is +4 dB when the reproducing light having the wavelength of 524 nm is reproduced as compared with the reproducing light having the wavelength of 680 nm. +7 dB at 0.3 μm, C
/ N becomes high.

(Embodiment 2) A case where a magneto-optical disk according to the present invention is manufactured by using a multi-source helicon sputtering apparatus and a DC and RF sputtering apparatus will be described.

First, in the helicon beam sputtering device,
Similar to the first embodiment, a process of setting the polycarbonate substrate 9 and successively forming the first dielectric layer 2, the reproducing magnetic layer 3 and the non-magnetic layer 4 while rotating the substrate will be described.

First dielectric layer: Si layer under the following film forming conditions.
The first dielectric layer 2 made of silicon nitride and having a layer thickness of 60 nm was formed by sputtering the get using Ar-30% nitrogen mixed gas.
Was formed.

Target: Si sputter gas: Ar-30% nitrogen mixed gas Sputter pressure: 1 × 10 ⁻² Torr RF input power: 100 W DC voltage: 500 V Film formation rate: 0.3 nm / sec Reproduced magnetic layer: Pt target and Co target under film conditions
By alternately sputtering the get, the film thickness is 0.9n
m Pt and a 0.4 nm-thickness Co film were alternately laminated to form a reproducing magnetic layer 3 which was a 20 nm-thickness Pt / Co multilayer film.

[0068] Non-magnetic layer: A non-magnetic layer 4 made of silicon nitride and having a thickness of 10 nm was formed under the same conditions as the case of the first dielectric layer 2 (the same film forming conditions as the silicon nitride film of the first dielectric layer 2). .

Then, as described above, the first dielectric layer 2,
A process of setting the polycarbonate substrate 9 on which the reproducing magnetic layer 3 and the non-magnetic layer 4 are formed in another sputtering apparatus and continuously forming the recording magnetic layer 5 and the third dielectric layer 6 will be described.

Recording magnetic layer: Under the same conditions as in Example 1, the nonmagnetic layer 4 was reverse-sputtered and then DC-sputtered to give a layer thickness of TbFeCoCr of 200.
A recording magnetic layer 5 having a thickness of nm was formed.

Second dielectric layer: The second dielectric layer 6 made of silicon nitride and having a layer thickness of 40 nm was formed by RF sputtering under the same conditions as in Example 1.

The polycarbonate substrate 9 formed as described above is taken out of the chamber, and finally, the protective film 7 is formed.
As a result, an ultraviolet curable resin film was formed to a thickness of about 10 μm to obtain a magneto-optical disk.

The film characteristics and the recording / reproducing characteristics of the manufactured magneto-optical disk were examined in the same manner as in Example 1, and the results are shown in Table 1.

As shown in Table 1, for the reproducing magnetic layer 3, Hs = 500 [Oe], Hc = 250 [Oe], θk.
= 0.45 [deg], Hs / Hn = 2, and a curl with good squareness was obtained. Further, for the recording magnetic layer 5, Hc = 15 [kOe].

Regarding the recording / reproducing characteristics, the wavelength 680
When reproducing using a semiconductor laser of nm, C / N = 42 dB at a mark length of 0.45 μm and a mark length of 0.3
C / N = 36 dB at μm. Similarly, when the recorded signal is reproduced using an Ar laser having a wavelength of 524 nm,
When the mark length was 0.45 μm, C / N = 46 dB, and when the mark length was 0.3 μm, C / N = 43 dB.

As can be seen from the above C / N measurement results, the mark length of 0.45 μm is +4 dB, and the mark length is +4 dB, when the reproduction light of the wavelength 524 nm is reproduced, as compared with the reproduction light of the wavelength 680 nm. +7 dB at 0.3 μm, C
/ N becomes high.

(Example 3) The reproducing magnetic layer 3 has a layer thickness 3 in which a Pt film having a film thickness of 1 nm and a Co film having a film thickness of 0.4 nm are alternately laminated.
The Pt / Co multilayer film of 0 nm is used to form the recording magnetic layer 5 with a layer thickness of 10
A magneto-optical disk made of a 0 nm TbFeCoCr film and having the same structure as that of Example 2 other than the above was manufactured by the same process as that of Example 2 (the multi-source helicon sputtering device and the DC and RF sputtering device were used. Made using).

The film characteristics and recording / reproducing characteristics of the manufactured magneto-optical disk were examined in the same manner as in Example 1, and the results are shown in Table 1.

As shown in Table 1, for the reproducing magnetic layer 3, Hs = 200 [Oe], Hc = 150 [Oe], θk.
= 0.44 [deg], Hs / Hn = 1.33, and a curl with good squareness was obtained. For the recording magnetic layer 5, Hc = 11 [kOe].

Regarding the recording / reproducing characteristics, the wavelength 680
When reproducing using a semiconductor laser of nm, C / N = 43 dB at a mark length of 0.45 μm and a mark length of 0.3
C / N = 38 dB at μm. Similarly, when the recorded signal is reproduced using an Ar laser having a wavelength of 524 nm,
When the mark length was 0.45 μm, C / N = 48 dB, and when the mark length was 0.3 μm, C / N = 45 dB.

As can be seen from the above C / N measurement results, the mark length of 0.45 μm is +5 dB, and the mark length is +5 dB when the reproduction is performed with the reproduction light of the wavelength of 524 nm as compared with the reproduction light of the wavelength of 680 nm. +7 dB at 0.3 μm, C
/ N becomes high.

Example 4 The non-magnetic layer 4 was a nitrogen silicon film having a layer thickness of 2 nm, and the recording magnetic layer 5 was TbF having a layer thickness of 50 nm.
A magneto-optical disk composed of an eCoCr film and having the same structure as that of Example 1 except for the above was manufactured in the same process as that of Example 1 (multi-source ion beam sputtering device and DC).
And an RF sputtering device).

The film characteristics and recording / reproducing characteristics of the manufactured magneto-optical disk were examined by the same method as in Example 1, and the results are shown in Table 1.

As shown in Table 1, for the reproducing magnetic layer 3, Hs = 160 [Oe], Hc = 150 [Oe], θk.
= 0.4 [deg], Hs / Hn = 1.07, and a curl with good squareness was obtained. Further, for the recording magnetic layer 5, Hc = 10 [kOe].

Regarding the recording / reproducing characteristics, the wavelength 680
When reproducing using a semiconductor laser of nm, C / N = 41 dB at a mark length of 0.45 μm and a mark length of 0.3
C / N = 35 dB at μm. Similarly, when the recorded signal is reproduced using an Ar laser having a wavelength of 524 nm,
When the mark length was 0.45 μm, C / N = 45 dB, and when the mark length was 0.3 μm, C / N = 42 dB.

As can be seen from the above C / N measurement results, the mark length of 0.45 μm is +4 dB, and the mark length is +4 dB when the reproduction is performed with the reproduction light with the wavelength of 524 nm, compared with the reproduction light with the wavelength of 680 nm. +7 dB at 0.3 μm, C
/ N becomes high.

(Embodiment 5) The nonmagnetic layer 4 is a nitrogen silicon film having a layer thickness of 10 nm, and the recording magnetic layer 5 is a T film having a layer thickness of 250 nm.
A magneto-optical disk made of a bFeCoCr film and having the same structure as that of Example 1 except for the above was manufactured in the same process as that of Example 1 (using a multi-source ion beam sputtering device and a DC and RF sputtering device). Made).

The film characteristics and recording / reproducing characteristics of the manufactured magneto-optical disk were examined by the same method as in Example 1, and the results are shown in Table 1.

As shown in Table 1, for the reproducing magnetic layer 3, Hs = 160 [Oe], Hc = 150 [Oe], θk.
= 0.4 [deg], Hs / Hn = 1.07, and a curl with good squareness was obtained. Further, for the recording magnetic layer 5, Hc = 15 [kOe].

Regarding the recording / reproducing characteristics, the wavelength 680
When reproducing using a semiconductor laser of nm, C / N = 41 dB at a mark length of 0.45 μm and a mark length of 0.3
C / N = 35 dB at μm. Similarly, when the recorded signal is reproduced using an Ar laser having a wavelength of 524 nm,
When the mark length was 0.45 μm, C / N = 45 dB, and when the mark length was 0.3 μm, C / N = 42 dB.

As can be seen from the above C / N measurement result, the mark length of 0.45 μm is +4 dB, and the mark length is +4 dB when the reproducing light having the wavelength of 524 nm is reproduced, as compared with the reproducing light having the wavelength of 680 nm. +7 dB at 0.3 μm, C
/ N becomes high.

Comparative Example 1 The reproducing magnetic layer 3 has a layer thickness 2 in which a Pt film having a film thickness of 1 nm and a Co film having a film thickness of 0.5 nm are alternately laminated.
The Pt / Co multilayer film of 0 nm is used to form the recording magnetic layer 5 with a layer thickness of 10
A magneto-optical disk made of a 0 nm TbFeCoCr film and having the same structure as that of Example 2 other than the above was manufactured by the same process as that of Example 2 (the multi-source helicon sputtering device and the DC and RF sputtering device were used. Made using).

The film characteristics and recording / reproducing characteristics of the manufactured magneto-optical disk were examined in the same manner as in Example 1, and the results are shown in Table 1.

As shown in Table 1, for the reproducing magnetic layer 3, Hs = 600 [Oe], Hc = 400 [Oe], θk.
= 0.46 [deg], Hs / Hn = 1.5, and H
s was a large film characteristic. For the recording magnetic layer 5, Hc = 11 [kOe].

Regarding the recording / reproducing characteristics, the wavelength 680
When reproducing using a semiconductor laser of nm, C / N = 34 dB at a mark length of 0.45 μm and a mark length of 0.3
C / N = 28 dB at μm. Similarly, when the recorded signal is reproduced using an Ar laser having a wavelength of 524 nm,
When the mark length was 0.45 μm, C / N = 36 dB, and when the mark length was 0.3 μm, C / N = 28 dB.

As can be seen from the above C / N measurement results, the wavelength 52
High C / N could not be obtained even when reproduced with reproduction light of 4 nm. It is considered that this is because good transfer was not performed because Hs was as large as 600 Oe.

(Comparative Example 2) The reproducing magnetic layer 3 has a layer thickness 2 in which a Pt film having a film thickness of 1 nm and a Co film having a film thickness of 0.4 nm are alternately laminated.
The recording magnetic layer 5 is a 0 nm Pt / Co multilayer film with a layer thickness of 40 nm.
A magneto-optical disk made of a TbFeCoCr film having a thickness of nm and having the same configuration as that of Example 2 other than the above was manufactured in the same process as in Example 2 (a multi-source helicon sputtering device and a DC and RF sputtering device were used. Made using).

The film characteristics and recording / reproducing characteristics of the manufactured magneto-optical disk were examined in the same manner as in Example 1, and the results are shown in Table 1.

As shown in Table 1, for the reproducing magnetic layer 3, Hs = 200 [Oe], Hc = 150 [Oe], θk.
= 0.44 [deg], Hs / Hn = 1.33, and a curl with good squareness was obtained. For the recording magnetic layer 5, Hc = 8 [kOe].

Regarding the recording / reproducing characteristics, the wavelength 680
When reproducing using a semiconductor laser of nm, C / N = 40 dB at a mark length of 0.45 μm and a mark length of 0.3
C / N = 35 dB at μm. Similarly, when the recorded signal is reproduced using an Ar laser having a wavelength of 524 nm,
When the mark length was 0.45 μm, C / N = 41 dB, and when the mark length was 0.3 μm, C / N = 37 dB.

As can be seen from the above C / N measurement results, the wavelength 52
High C / N could not be obtained even when reproduced with reproduction light of 4 nm. It is considered that this is because the recording magnetic layer 5 had a thin layer thickness of 40 nm, so that the leakage magnetic field was small and good transfer was not performed.

(Comparative Example 3) A magneto-optical disk was produced using only a DC and RF sputtering device.

Here, the reproducing magnetic layer 3 was formed by a DC sputtering method using a Pt target and a Co target under the following film forming conditions. In addition, Pt / C to be the reproducing magnetic layer 3
o The layer thickness of the multilayer film is 20 nm (Pt film with a film thickness of 1 nm and film thickness of 0.
The layer thickness was obtained by alternately stacking 4 nm Co films.

Sputtering gas: Ar 100SCCM Sputtering gas pressure: 1.5 × 10 ⁻³ Torr Input power: 200 W Film formation rate: Pt 0.15 nm / sec Co 0.05 nm / sec Further, the recording magnetic layer 5 was formed by the DC sputtering method. According to Example 1
The film was formed under the same film forming conditions as described above. It should be noted that Tb to be the recording magnetic layer
The layer thickness of the FeCoCr film was 100 nm.

In addition, the first dielectric layer 2, the non-magnetic layer 4 and the second
The dielectric layer 6 is formed on the second layer of the first embodiment by RF sputtering.
It was formed under the same film forming conditions as the dielectric layer 6. The film thicknesses of the silicon nitride films serving as the first dielectric layer 2, the nonmagnetic layer 4 and the second dielectric layer 6 were 60 nm, 5 nm and 40 nm, respectively.

The film characteristics and recording / reproducing characteristics of the manufactured magneto-optical disk were examined in the same manner as in Example 1, and the results are shown in Table 1.

As shown in Table 1, in the reproducing magnetic layer 3, since the anisotropic dispersion is large, Hs = 1100 [Oe],
Hc = 4000 [Oe], θk = 0.44 [deg], H
Since s / Hn = 2.75, the film characteristics were high in Hs. For the recording magnetic layer 5, Hc = 11 [kOe]
Met.

Regarding the recording / reproducing characteristics, the wavelength 680
When reproducing using a semiconductor laser of nm, C / N = 32 dB at a mark length of 0.45 μm and a mark length of 0.3
C / N = 25 dB at μm. Similarly, when the recorded signal is reproduced using an Ar laser having a wavelength of 524 nm,
When the mark length was 0.45 μm, C / N = 34 dB, and when the mark length was 0.3 μm, C / N = 25 dB.

As can be seen from the above C / N measurement results, the wavelength 52
High C / N could not be obtained even when reproduced with reproduction light of 4 nm. It is considered that this is because good transfer was not performed because Hs and Hs / Hc of the reproducing magnetic layer 3 were large.

(Comparative Example 4) The reproducing magnetic layer 3 was formed with a layer thickness of 20 nm.
A magneto-optical disk having the same structure as that of Comparative Example 3 except that the GdFeCo film was formed by the same method (RF and DC sputtering method) as in Comparative Example 3.
The reproducing magnetic layer 3 was formed by the DC sputtering method.
It was formed under the following film forming conditions.

Target: Gd ₁₉ Fe ₆₁ Co _17.5 Sputtering gas: Ar 100 SCCM Sputtering gas pressure: 1.5 × 10 ⁻³ Torr Input power: 1000 W Deposition rate: 20 nm / min Film of fabricated magneto-optical disk The characteristics and the recording / reproducing characteristics were examined in the same manner as in Example 1, and the results are shown in Table 1.

As shown in Table 1, for the reproducing magnetic layer 3, Hs = 110 [Oe], Hc = 105 [Oe], θk.
= 0.48 [deg], Hs / Hn = 1.07, and a curl with good squareness was obtained. For the recording magnetic layer 5, Hc = 11 [kOe].

Regarding the recording / reproducing characteristics, the wavelength 680
When reproducing using a semiconductor laser of nm, C / N = 45 dB at a mark length of 0.45 μm and a mark length of 0.3
C / N = 40 dB at μm. Similarly, when the recorded signal is reproduced using an Ar laser having a wavelength of 524 nm,
When the mark length was 0.45 μm, C / N = 42 dB, and when the mark length was 0.3 μm, C / N = 37 dB.

As can be seen from the above C / N measurement result, the mark length 0.45 μm and the mark length 0. -3dB at 3μm, C / N
Becomes lower.

When the C / N levels of Example 1 and Comparative Example 4 are compared, with reproduction light having a wavelength of 680 nm, Example 1 has a mark length of 0.45 μm, 4 dB, and a mark length of 0.3 μm.
However, in the reproducing light of wavelength 524 nm, in Example 1, the pit length 0.45 μm gives 3 dB, and the pit length 0.3 μm gives 5 dB, the C / N becomes higher.

In Table 1, as reference data, Pt was formed on the glass substrate by the same method as the magneto-optical disk of each example.
The results of measuring the interface state of the Pt / Co multilayer film by producing only the / Co multilayer film are shown. Here, the interface state of the multilayer film can be examined by the low-angle X-ray diffraction method (the state of the periodic total reflection diffraction peak appearing on the low-angle side and the first-order superlattice peak shown in Table 1). -It is sufficient to check the intensity Ip of the black).
As can be seen from this reference data, when the reproducing magnetic layer is formed by a sputtering method having a low particle energy such as the DC sputtering method (Comparative Example 3), the intensity Ip of the primary superlattice peak is It is low, and it can be seen that the flatness of the interface of the Pt / Co multilayer film is deteriorated. Therefore, anisotropic dispersion becomes large and Hs becomes large.

Therefore, it is understood that a high C / N can be obtained at a short wavelength by using the Pt / Co multilayer film having a small anisotropic dispersion as the reproducing magnetic layer. In addition, substantially the same effects can be obtained in Examples 2 to 5.

[0118]

[Table 1]

[0119]

As described above, according to the present invention, the wavelength of 5
A large Kerr rotation angle can be obtained when reproducing light with a short wavelength of 50 nm or less is used. Further, by making the saturation magnetic field Hs smaller than that of the conventional reproducing magnetic layer made of a Pt / Co multilayer film, the magnetization of the recording magnetic layer can be satisfactorily transferred to the reproducing magnetic layer during reproduction. Therefore, a high C / N is obtained when a laser beam having a short wavelength is used as the reproduction light.

Further, as described above, when a reproducing light of a short wavelength of 550 nm or less is used, a large Kerr rotation angle can be obtained. Therefore, by using the reproducing light of a short wavelength, a short recording mark of 0.45 μm or less can be formed. It is possible to provide a magneto-optical recording medium that can be reproduced and can obtain high density and high C / N.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a magneto-optical recording medium having a constitution of the present invention.

FIG. 2 is a schematic diagram illustrating a reproducing method of the magneto-optical recording medium of the present invention.

FIG. 3 is a cross-sectional view showing a magneto-optical disk having the configuration of Example 1.

FIG. 4 shows the curl (λ = 6) of the reproducing magnetic layer 3 of Example 1.
It is a figure which shows 80 nm).

[Figure 5]
It is a figure which shows the Kerr loop of a perpendicular magnetization film.

[Explanation of symbols]

 1 ... Substrate 2 ... First Dielectric Layer 3 ... Reproducing Magnetic Layer 4 ... Non-Magnetic Layer 5 ... Recording Magnetic Layer 6 ... Second Dielectric Layer 7 ... Initialization Magnetic field 8 ... Transfer assisting magnetic field 9 ... Polycarbonate substrate 10 ... Protective film

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Osamu Shinoura 13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation

Claims (2)

[Claims] 1. A dielectric layer, a reproducing magnetic layer composed of a Pt / Co multilayer film which is a perpendicular magnetization film, and a non-magnetic layer on a transparent substrate,
In a magneto-optical recording medium in which recording magnetic layers, which are perpendicularly magnetized films having Curie temperature and coercive force lower than those of the reproducing magnetic layer, are stacked in this order, the reproducing magnetic layer has a layer thickness of 15 to
In the range of 30 nm, the thickness of the non-magnetic layer is 2 to 10 nm,
The layer thickness of the recording magnetic layer is in the range of 50 to 250 nm,
A magneto-optical recording medium characterized in that the reproducing magnetic layer and the recording magnetic layer are magnetostatically coupled. 2. The magneto-optical recording medium according to claim 1, wherein the saturation magnetic field Hs of the reproducing magnetic layer satisfies Hs ≦ 500 [Oe] at room temperature. .