JPH01162257A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To lower Curie point and to improve information transfer speed by adding a 3rd element to the Co layers of a magneto-optical recording medium the recording layers consisting of thin superlattic metallic films or thin modulation structure metallic films alternately laminated with the Co layers and Pt layers. CONSTITUTION:This magneto-optical recording medium is formed, as the recording layers, with the thin superlattice metallic films or thin modulation structure metallic films alternately laminated with Co100-xMx (where M denotes at least one kind among B, C, Al, Si, P, Ti, V, Fe, Ni, Cu, Ga, Ge, Zr, Nb, Mo, In, Sn, Sb, Gd, Tb, Dy, and Ta) 0.5-2.5atom. layers and Pt 1-7atom. layers and the total thickness of the recording layers is 50-500Angstrom . The lower limit of the substitution ratio (x) of the respective elements is 0.1atom.%, whereas the lowering of the Curie point is not effectual when said ratio is lower than the above-mentioned ratios. While the substitution ratio (x) of the above-mentioned respective elements varies to 7-40atom.% according to the elements to be added, there is the possibility that the magneto-optical characteristics are deteriorated on the contrary when the ratio is higher than the above-mentioned values.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magneto-optical recording medium that uses magneto-optic effects to record and reproduce information using laser beams, etc. Regarding recording media.

[Summary of the invention]

The present invention provides a recording layer obtained by adding a third element to the 00 layer in a magneto-optical recording medium whose recording layer is a superlattice metal thin film or a modulation structure metal thin film in which a Co layer and a Pt layer are laminated. This makes it possible to lower the Curie point of the layer and improve the information transfer speed.

[Conventional technology]

2. Description of the Related Art In recent years, a magneto-optical recording method in which recording and reproduction is performed using semiconductor laser light or the like has been attracting attention as a rewritable high-density recording method.

The recording material used in this magneto-optical recording method is G
Rare earth elements such as d, Tb, and Dy, and Fe.

A typical conventional example is an amorphous alloy in combination with a transition metal element such as CO. However, the rare earth elements and Fe that make up these amorphous alloy thin films are highly oxidized.
It has the property of easily combining with oxygen in the air to form oxides. As such oxidation progresses and leads to corrosion and pitting, it induces signal dropout, and especially when rare earth elements are oxidized, C/N decreases as coercive force and residual magnetic Kerr rotation angle decrease.
The ratio deteriorates. Such problems are unavoidable as long as rare earth elements are used as the material for the recording layer of an optical recording medium.

The above-mentioned corrosion and pitting cause Tj to occur in the amorphous alloy thin film.
, Cr, AI, etc., which can form a passive film, and Pt.
This can be prevented by adding inert elements such as , Pd, and Co, and its effect has been confirmed in cases where the film is relatively thick.

However, the use of the above-mentioned additive elements often leads to a decrease in the magnetic Kerr rotation angle, and the desired effect cannot be obtained with a film thickness of less than 500 Å, so there is a problem that a protective film or the like must be used in combination. There is.

On the other hand, the present applicant previously reported in Japanese Patent Application No. 62-211569 that a Co=Pt-based superlattice metal thin film, in which Co layers and Pt layers are alternately laminated without using rare earth elements, has excellent corrosion resistance. It is disclosed that the material exhibits excellent magneto-optical properties in a region with a thin overall thickness.

[Problem that the invention seeks to solve]

By the way, in a magneto-optical recording medium, in order to cause a magnetic change, it is necessary to locally heat the recording layer to a temperature higher than the Curie temperature. Therefore, when using a magneto-optical recording medium having a superlattice metal thin film or a modulation structure metal thin film as a recording layer, the lower the Curie point of the recording layer, the higher the information transfer speed. As a means of lowering the Curie point, it has been conventionally considered to add a third element to the recording layer. However, depending on the type of element, these methods reduce the thermal stability of the recording layer, resulting in disturbance of the interface between the dissimilar metal layers due to diffusion, resulting in a deterioration of the initially good coercive force and squareness ratio. .

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a magneto-optical recording medium with a high information transfer rate.

[Means for solving problems]

In order to solve the above-mentioned problems, the present inventors investigated the type and amount of the third element to be added, and found that a superlattice metal thin film or a modulation structure metal thin film in which Co layers and Pt layers are alternately laminated. In a magneto-optical recording medium having a recording layer of
The inventors have discovered that by adding a certain metal element within a predetermined range to the Co layer, a recording layer having good thermal stability while lowering the Curie point can be obtained, leading to the present invention. That is, the magneto-optical recording medium according to the present invention has CO+oo-*Mx (where M is B or C).

Aj! , Si, P, Ti, V, Fe,
Nl, Cu.

Ga, Ge, Zr, Nb, Mo, I
n, Sn.

Represents at least one of Sb, Gd, Tb, Dy, and Ta, X represents the amount of substitution in atomic %, and when M=A1, 0.1≦
x≦7. When M=Zr, 0.1≦x≦14゜M=Si,
For MO, Ta, 0.1≦x≦20. When M=Fe, 0.1≦x≦25. M=B, C, Ti, V.

0.1≦x for Cu, Ga, Ge, Nb, In, Sn
≦30. When M=P, 0.1≦x≦35. M=C;d
.

For Tb and Dy, 0.1≦χ・≦40. When M=Sb, 0.1≦x≦45. When M=Ni, 0.1≦x≦70. ) The recording layer is a superlattice metal thin film or a modulation structure metal thin film in which 0.5 to 2.5 atomic layers and Ptl to 7 atomic layers are alternately laminated, and the total thickness of the recording layer is 50 to 500 atomic layers. This is especially true for clothing.

Ideally, the interface between the metal layers constituting the metal thin film serving as the recording layer in the present invention should be flat and have a so-called superlattice structure, with atoms of different metals not mixing with each other. It may have a so-called modulation structure (composition modulation structure) in which the composition changes while maintaining a constant period as a whole while causing some disturbance.

The superlattice metal thin film or modulation structure metal thin film described above can be formed by sputtering, vacuum deposition, or the like.

Here, the above Co. . -, M, the metal layer is C
It can be considered that a part of the o layer is replaced with the third element M. Possible methods for adding the third element M to the Co layer include placing an M chip on a Co evaporation source, or using a Co-M alloy as an evaporation source.

The lower limit of the substitution amount X of each of the above elements is set at 0.1 atomic %, but if it is lower than this, the effect of reducing the Curie point will not appear. Further, the upper limit of the substitution amount X of each of the above elements varies from 7 to 40 atomic % depending on the added element, but if it is higher than these values, there is a risk that the magneto-optical properties may be deteriorated.

The above Co. . The range of -11M K or PL metal layer thickness - (number of atomic layers) was set from the perspective of optimizing magneto-optical properties, and outside the above range, in-plane magnetization components occur and magnetic Optical properties deteriorate.

Further, the third element described above is added to the PT layer, and the composition of the Pt layer is changed to that of the Pt layer. . -, M, (where X represents the amount of substitution in atomic %, and 0≦x≦15), but in this case, the purpose is to improve magneto-optical properties and thermal stability. Rather, the main purpose should be to adjust the Killy point.

This is because, with some exceptions, when the third element is added to the PT layer, the Curie point increases and the magnetic Kerr rotation angle decreases. However, from the perspective of protecting recorded information, the Curie point does not necessarily have to be as low as possible, so if the Curie point of the recording layer is extremely low, this method can be used to reduce the Curie point to a practical level. It is possible to increase Elements that can be added to the Pt layer include Cr and Mn in addition to the third element mentioned above.

Co, Zn, Y, Rh, Ag, La, Nd, Sm.

Examples include Eu, Ho, Hf, W, Ir, Au, Pb, Bi, and the like.

Further, the PT layer may be replaced with a Pd layer in any proportion.

Writing methods for the recording layer of a magneto-optical recording medium having the above-mentioned composition include a light beam, a nail-shaped magnetic head, a thermal pen, an electron beam, etc., which can supply the energy necessary to generate a reversed magnetic domain. Needless to say, anything is fine as long as it is something.

[Effect]

In the magneto-optical recording medium according to the present invention, instead of using an amorphous alloy consisting of a rare earth element and a transition metal element, which has been widely used in the past, as the recording layer, 000 is partially substituted with a third element. By using a superlattice metal thin film or a modulation structure metal thin film in which a layer and a PT layer are laminated, it becomes possible to lower the Curie point of the recording layer and increase the information transfer rate.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on experimental examples.

This experimental example is an example of a magneto-optical recording medium whose recording layer is a modulated metal thin film in which a Co layer partially substituted with a third element and a PT layer are alternately laminated by dual simultaneous magnetron sputtering. be. Here, the third element used (
Hereinafter, this will be referred to as an additive element. ) was divided into a group with an atomic number of less than 40 and a group with an atomic number of 40 or more, and a modulated structure metal thin film was created for each group under slightly different creation conditions.

First, B is used as an additive element M having an atomic number of less than 40.

C, A1. Si, P, Ti, V, Fe, Ni.

An experimental example using Cu, Ga, and Ge will be described.

First, a 100 am diameter CO11111-
11MX and PT targets were installed, a water-cooled glass substrate was placed on a rotating base facing these targets, and binary simultaneous magnetron sputtering was performed in an argon atmosphere with a gas pressure of 5 Xl0-'' Torr. At this time, direct current sputtering was performed with an input current of 0.4 OA for the Co+o.-X Mg target, and high frequency sputtering was performed with an input power of 400 W for the PT target.

According to this device, the period of lamination can be arbitrarily determined by changing the current or power applied to each target, or the rotation speed of the rotating base on which the substrate is placed. The rotation speed of the rotating base is 16 r
Co, with a thickness of 4.25 pm. . -xM, 1 layer and 6.44-thick PT layers are laminated alternately, total thickness 150
A thin metal film with a modulation structure based on human CO1116-XMII P was created.

Here, the thickness of one atomic layer of CO+o6-1MX layer is 2.5
Since the thickness of one atomic layer of the Pt layer is 2.8 mm, the above Co. . - The number of atomic layers per 11 of the 11M11 layer is approximately 1.7, and the number of atomic layers per 11 of the above Pt layer is 2.3
It is. Also, the reason why the number of atomic layers is not an integer is because the created metal thin film does not have an ideal interface between each metal layer and has a modulation structure, but the total number of atomic layers is approximately 10.7. period is maintained. The period of the produced superlattice metal thin film was determined from the peak angle in small-angle X-ray scattering.

Each modulated structure metal thin film was created by varying the amount of each of the above-mentioned additive elements. For each modulated metal thin film created in this way, the magnetic Kerr rotation angle θ at a wavelength of 780 nm was first measured, and the temperature of the modulated metal thin film was increased while applying a magnetic field of 500 (Oe) to create a magnetic field. The temperature at which the Kerr rotation angle θ becomes O was determined as the Curie point T.

First, Figure 1 shows the relationship between the amount of added elements (atomic %) and the Curie point Tc ("C) of each of the modulated metal thin films created. The Curie point T, is 255°C.On the other hand,
When each of the above-mentioned additive elements is used, the Curie point Tc is lowered, and it can be seen that /l, TI, and P in particular have a large effect of reducing the Curie point Tc even in small amounts.

Next, the additive elements (atomic%
) and the magnetic Kerr rotation angle θK (minutes) is shown in FIG. 2. Here, the magnetic Kerr rotation angle θ of the modulated metal thin film when no additive element is used is 25.5 minutes. This value is based on B and P as additive elements.

This is maintained even when Fe, Ni, and Cu are used.

In particular, since P and Cu have a large effect of reducing the Curie point T, they can be said to be useful additive elements. For other additive elements, a slight decrease in the magnetic Kerr rotation angle θ was observed.

Here, the temperature dependence of the magnetic Kerr curve and the magnetic Kerr rotation angle θ observed for some of the above-described modulated metal thin films is shown in the following figure. That is, FIG. 3(A) and FIG. 3(B) show Co9. P,
Pt-based modulated structure metal thin films, FIGS. 4(A) and 4(B) are Co doped with 10 atom % of Ti. TI+o
A Pt-based modulation structure and a full modulation structure metal thin film are shown. For comparison, Co does not contain any additional elements.

. =Characteristics of Pt-based modulation structure metal \il film are also shown in Figure 5 (A).
and shown in FIG. 5(B). In each of these figures (A
) shows the magnetic Kerr curve immediately after sputtering, the vertical axis is the magnetic Kerr rotation angle θ (minutes), and the horizontal axis is the magnetic field strength H (
The diagram in (B) shows the temperature dependence of the magnetic Kerr rotation angle θ8, and the vertical axis represents the magnetic Kerr rotation angle '
θ (minutes) and the horizontal axis represent temperature (°C), respectively.

As can be seen from the diagram (A), these modulation structure metal thin films all have magnetic Kerr rotation angles θ1. Coercive force H
e, and has a good squareness ratio. Here, the squareness ratio refers to the residual magnetic Kerr rotation angle θ1 and the saturated magnetic Kerr rotation angle θ1.
It can be said that the closer this value is to 1, the better the magneto-optical properties are. These properties did not change even when the magneto-optical properties were measured again after the temperature was raised to the Curie point Tc and then returned to room temperature.

Next, Zr is added as an additional element M having an atomic number of 40 or more.

Nb, Mo, In, Sn, Sb, Cd, Tb.

An experimental example using Dy and Ta will be described.

To create a modulated metal thin film, use a gas pressure of 4X10-'↑orr.
For the Co layer containing additive elements, direct current sputtering with an input current of 0.4 A, Pt
The layer was formed by high frequency sputtering with an input power of 450W. Here, G, which is a rare earth element, is added as an additive element.
When using d, Tb, and Dy, these fan-shaped chips are placed on a Co target and DC sputtering is performed, and when other additive elements are used, Co, Co, and Dy are used in the same manner as in the previous experiment. Direct current sputtering was performed using a 6-, M, target. The rotation speed of the rotating base is 16 rp
s and Co. . - HM X layer and Pt layer alternately stacked, total thickness 100 Co,. . -XMII=Pt-based modulated structure metal thin film was created.

Each modulated structure metal thin film was created by varying the amount of each of the above-mentioned additive elements. For each modulated metal thin film created in this way, the magnetic Kerr rotation angle θ and the Curie point T are the same as when using the additive element M with an atomic weight of less than 40.
c was measured.

First, Figure 6 shows the relationship between the amount of added elements (atomic %) and the Curie point 'rc ('c) of each modulated metal thin film created. The Curie point Tc of is 258°C. On the other hand, when each of the above-mentioned additive elements is used, the Curie point Tc is lowered, especially Zr, Ta, Mo, Sn,
It can be seen that even a small amount of Gd etc. has a large effect of reducing the Curie point Tc.

Next, the additive elements (atomic%
) and the magnetic Kerr rotation angle θ, (minutes) is shown in FIG. 7. Here, the magnetic Kerr rotation angle θ of the modulated metal thin film when no additive element is used is 20.7 minutes. This value was maintained when sb was used, indicating that this element is an excellent additive element. When other additive elements are used, the magnetic Kerr rotation angle θ is reduced, and the degree of this decrease is particularly remarkable when Mo, Ta, and Zr are used.

Here, the temperature dependence of the magnetic Kerr curve and the magnetic Kerr rotation angle θ observed for some of the above-mentioned modulated metal thin films is shown in the following figures, namely, FIG. 8(A) and FIG. 8( B) is CO9・N with 10 atomic% Nb added.
br·-pt-based modulated structure metal thin film, FIGS. 9(A) and 9(B) are COq with 10 atomic % Mo added.
aM O+a=P is a system modulation structured metal thin film, Figure 1θ (
A) and FIG. 10(B) respectively show the characteristics of a C05oD7tePt-based modulated structure metal thin film doped with 20 atom % of Dy. For comparison, Co does not contain any additive elements. =Characteristics of the Pt-based modulated metal thin film are also shown in Figures 11 (A) and 11 (B). In each of these figures, (A) represents the magnetic Kerr curve immediately after sputtering, and the vertical axis represents the magnetic Kerr curve. Kerr rotation angle θ.

(minutes), the horizontal axis represents the magnetic field strength H (koe), and the diagram in (B) represents the temperature dependence of the magnetic Kerr rotation angle θ, and the vertical axis represents the magnetic Kerr rotation angle θK (minutes). , the horizontal axis is the temperature (
°C) respectively.

These modulated structure metal thin films also have the same structure as shown in Fig. 3 (
Similar to the cases shown in A) and FIG. 4(A), good magneto-optical properties are obtained. In particular, as can be seen from the comparison between Figures 10(A) and 11(A), when Dy is added, the coercive force Hc is higher than when no additive element is contained.
is also increasing. A similar increase in coercivity H0 was also observed when Tb was added. Furthermore, no deterioration of the magneto-optical properties was observed in any of the modulated metal thin films after temperature cycling (heating to the Curie point and then cooling to room temperature).

From the above results, it can be seen that the various additive elements described above all lower the Curie point Tc of the modulated structure metal thin film. However, additive elements that have a large effect of reducing the Curie point T, do not necessarily maintain the value of the magnetic Kerr rotation angle θ, well.Lowering the Curie point Tc improves the information transfer speed of magneto-optical recording media. However, each additive element must be appropriately selected depending on the desired characteristics of the modulated structure metal thin film to be obtained, taking into account that a decrease in the zero section of the magnetic Kerr rotation angle may occur at the same time.

For your reference, this experimental example introduces an experimental example when additive elements are used in the PT layer.
Cr, Ni, Cu, Zr, Nb.

A magneto-optical recording medium whose recording layer is a modulated metal thin film in which Pt1i substituted with one of Mo, Ag, Gd, Tb, Dy, Ta, and W is alternately laminated by simultaneous binary magnetron sputtering. This is an example. Sputtering was performed in an argon atmosphere with a gas pressure of 5 x 10-'' Torr, and an input current of 0.4 A for the CO target.
, DC sputtering with an input voltage of 300 V, and high frequency sputtering with an input power of 400 W for a PT target. The additive elements were added by placing a plurality of fan-shaped chips of each element with a central angle of 12 to 20 degrees and a radius of 50 mm on a Pt target. In this experimental example, the rotation speed of the rotating base was 16 rpm, and the 00 layer was 4.25 people thick and the Pt layer was 6.44 people thick. . -,
M, layers are laminated alternately, total thickness 150 people Co Pt
layer. . -8M8-based modulated metal thin film was created.

The relationship between the additive element it (atomic %) and the Curie point 're (''c) of each modulation structure metal thin film created in this way is shown in Figure 12. Here, the modulation structure when no additive element is used is shown. The Curie point Tc of a metal thin film is approximately 280°C.On the other hand, when each of the above-mentioned additive elements is used, the Curie point Tc
The Curie point Tc is increasing except for u.

Furthermore, the relationship between the amount of added elements (atomic %) and the magnetic Kerr rotation angle θK (minutes) of each of the produced modulated structured metal thin films is shown in Figure 13. The magnetic Kerr rotation angle of is about 26.4 minutes. This value was maintained when Nt or MO was used as an additive element, but a slight decrease was observed for other elements.

Therefore, when using additive elements for the Pt layer, the purpose should be to raise the Curie point to a practical range in cases where the Curie point of the recording layer is originally extremely low.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, Co
By adding a third element to the 00 layer of a magneto-optical recording medium whose recording layer is a superlattice metal thin film or a modulation structure metal thin film in which layers and PT layers are alternately laminated, the Curie point is lowered and information is It becomes possible to improve the transfer speed. Moreover, such superlattice metal thin films or modulation structure metal thin films exhibit excellent magneto-optical properties in the thin film thickness range of 50 to 500 mm, so they are meaningful from the viewpoint of resource saving and improvement of production efficiency. be.

Furthermore, the superlattice metal thin film or modulation structure metal thin film does not contain rare earth elements, whose supply is expected to become tight worldwide in the future, so a stable and economical supply of magneto-optical recording media can be expected. .

If such a magneto-optical recording medium is used as a storage medium for a magneto-optical memory such as a so-called beam-addressable file memory, which writes using a light beam and reads using the magnetic Kerr effect, it can achieve extremely high performance. It is possible to realize a memory device that has a high density and a high C/N ratio and maintains high reliability over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the amount of additive elements and the Curie point Tc in a typical modulated metal thin film when an additive element having an atomic number of less than 40 is used. FIG. 2 is a characteristic diagram showing the relationship between the amount of additive elements and the magnetic Kerr rotation angle θ in a typical modulated metal thin film when an additive element having an atomic number of less than 40 is used. FIG. 3(A) and FIG. 3(B) are characteristic diagrams showing the magneto-optical properties and their temperature dependence of the C0qsPs Pt-based modulation structure metal thin film,
FIG. 3(A) shows the magnetic Kerr curve immediately after sputtering, and FIG. 3(B) shows the temperature dependence of the magnetic Kerr rotation angle. FIG. 4(A) and FIG. 4(B) are Co layers. T l
+. = Pt, are characteristic diagrams showing the magneto-optical properties and their temperature dependence of a metal thin film with a system modulation structure, where FIG. 4(A) shows the magnetic Kerr curve immediately after sputtering, and FIG. 4(B) shows the magnetic Kerr rotation angle. The temperature dependence is shown respectively. Figure 5 (A
) and FIG. 5(B) are Co. . =Characteristic diagrams showing the magneto-optical properties of a Pt-based modulated metal thin film and its temperature dependence; FIG. 5(A) shows the magnetic Kerr curve immediately after sputtering, and FIG. 5(B) shows the temperature of the magnetic Kerr rotation angle. FIG. 6, which shows the dependence, is a characteristic diagram showing the relationship between the amount of added elements and the Curie point Tc in a typical modulation structure metal thin film when using added elements with an atomic number of 40 or more. FIG. 7 shows the amount of additive elements and the magnetic Kerr rotation angle θ in a typical modulated metal thin film when additive elements with atomic numbers of 40 or higher are used. FIG. Figures 8(A) and 8
Figure CB) is co. Nbt. FIG. 8(A) is a magnetic Kerr curve immediately after sputtering, and FIG. 8(B) is the temperature of the magnetic Kerr rotation angle. FIG. 9(A) and FIG. 9(B), which respectively show the dependence, are Co drops. Mo+. FIG. 9(A) is a characteristic diagram showing the magneto-optical properties and their temperature dependence of a -pt-based modulated metal thin film;
shows the magnetic Kerr curve immediately after sputtering, FIG. 9(B) shows the temperature dependence of the magnetic Kerr rotation angle, and FIGS. 10(A) and 10(B) show CO*aD1z*=P.
FIG. 10(A) shows the magnetic Kerr curve immediately after sputtering, and FIG. 10(B) shows the temperature dependence of the magnetic Kerr rotation angle. Each shows its gender. FIG. 11(A) and FIG. 11(B) are Co. ,=P
FIG. 11(A) is a characteristic diagram showing the magneto-optical properties of a metal thin film with a t-based modulation structure and its temperature dependence; FIG. 11(A) shows the magnetic Kerr curve immediately after sputtering, and FIG. 11(B) shows the temperature dependence of the magnetic Kerr rotation angle. Figure 12 is a characteristic diagram showing the relationship between the amount of added elements and the Curie point T in a modulated metal thin film using added elements in the PT layer as a reference experimental example, and Figure 13 shows the relationship between the Curie point T and the amount of added elements in the PT layer. FIG. 2 is a characteristic diagram showing the relationship between the amount of added elements in a structural metal thin film and the magnetic Kerr rotation angle θ. Patent Applicant Sony Corporation Representative Patent Attorney Koike Mima Sakae Tamura - Masaru Sato Figure 1 Figure 2 Figure 6 Figure 71! Figure 8 (A) Figure 8 (B) Figure 9 (A) Temperature ('CJ Figure 9 (B) Figure 10 (A) Temperature (@C) Figure 10 (B) Figure 11 (A ) Temperature f(”C) Figure 11(B)

Claims (1)

[Claims] Co_1_0_0_-_xM_x (where M is B,
C, Al, Si, P, Ti, V, Fe, Ni, Cu, G
a, Ge, Zr, Nb, Mo, In, Sn, Sb, Gd
, Tb, Dy, and Ta, x represents the amount of substitution in atomic %, and when M=Al, 0.1≦x≦7, M
=Zr 0.1≦x≦14, M=Si, Mo, Ta
In case of 0.1≦x≦20, in case of M=Fe 0.1≦x≦
25, M=B, C, Ti, V, Cu, Ga, Ge, Nb
, In, Sn, 0.1≦x≦30, M=P, 0
．． 1≦x≦35, M=Gd, Tb, Dy, 0.1≦
When x≦40, M=Sb, 0.1≦x≦45, M=Ni
In the case of 0.1≦x≦70. ) The recording layer is a superlattice metal thin film or a modulation structure metal thin film in which 0.5 to 2.5 atomic layers and 1 to 7 Pt atomic layers are alternately laminated, and the total thickness of the recording layer is 50 to 500 Å. A magneto-optical recording medium characterized by: