JPH08213236A - Magnetic multilayered film, manufacture thereof and photomagnetic recording medium - Google Patents

Abstract

PURPOSE: To enable a magnetic multilayered film which is large in Kerr turning angle in a short wavelength range of light and vertical magnetic anisotropy and less reduced in vertical magnetic anisotropy due to a thermal effect to be formed on a board of comparatively low temperature and to provide a photomagnetic recording medium which is excellent repetitiously rewritable properties. CONSTITUTION: Co-Pt alloy layers are laminated through the intermediary of a Pt layer for the formation of a magnetic multilayered film, wherein the Co content of the Co-Pt alloy layer is 25 to 75atom%, and the magnetic multilayered film is formed on a board kept at temperatures of 80 to 150 deg.C through an evaporation method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic multilayer film, a method for producing the same, and a magneto-optical recording medium having the magnetic multilayer film as a recording film.

[0002]

2. Description of the Related Art Conventionally, TbFe has been used as a magneto-optical recording material.
Rare earth-transition metal amorphous alloy thin films such as Co have been used. As a means for realizing high density of magneto-optical recording, shortening of the wavelength of a laser used as a light source is being studied, and recording / reproducing by a semiconductor laser having a wavelength of 700 nm or less is being realized. Further, room temperature oscillation of a semiconductor laser in the 400 to 500 nm band has also been confirmed. However, conventionally used TbFeCo and the like have a small Kerr rotation angle of 0.2 ° or less in the short wavelength region, and thus a material exhibiting a large Kerr rotation in the short wavelength region is desired.

As a material exhibiting a large Kerr rotation in a short wavelength region, a multi-layered film in which Pt and / or Pd layers and Co layers are alternately laminated has been noted, and a large Kerr rotation of 0.2 to 0.4 ° is noted. Corners have been reported (Japanese Patent Laid-Open No. 2-56572).
Japanese Patent Laid-Open No. 2-263344, J. App
l. Phys. 67, 2136, 1990,
J. Magn. Magn. Mater. Volume 93, 194
Page, 1991).

However, in these multilayer films, Pt
And / or Pd layer thickness is about 1 nm, Co layer thickness is 0.2
It is very thin, about 0.5 nm, and it is difficult to produce a multilayer film having the same film structure with good reproducibility. Further, one of the problems for practical application of a magneto-optical disk having such a multilayer film as a recording film is a rewritable property.
The magneto-optical disk using the rare earth-transition metal alloy film which has been put into practical use has achieved the number of times of rewriting of 10 ⁶ or more. However, when the Pt / Co multilayer film is rewritten many times, the perpendicular magnetic anisotropy is deteriorated due to thermal influence of the laser light to be irradiated and diffusion at the interface between the Pt layer and the Co layer. Therefore, it has been reported that the number of times of rewriting is 10 ⁴ at most.

For such a Pt / Co multilayer film, Co
Pt alloy films have been studied and reported (Appl. P.
hys. Lett. 61, 1600, 1992
Year). The CoPt alloy film has a Kerr rotation angle equal to or greater than that of the Pt / Co multilayer film, and is not a multilayer film, and therefore, the repetitive rewriting frequency characteristic is superior to that of the Pt / Co multilayer film.
However, when forming a film by the ultra-high vacuum evaporation method, a perpendicular magnetization film cannot be obtained unless the substrate temperature during film formation is 200 ° C. or higher. Therefore, there is a drawback that a polymer resin substrate such as polycarbonate cannot be used.

[0006]

The object of the present invention is to exhibit a large Kerr rotation angle in the short wavelength region, a large perpendicular magnetic anisotropy, and a decrease in the perpendicular magnetic anisotropy due to thermal influence. A small magnetic multilayer film can be formed on a substrate at a relatively low temperature, and a magneto-optical recording medium having excellent rewritable characteristics can be provided.

[0007]

The above objects are achieved by the present invention described in (1) to (9) below. (1) A magnetic multilayer film in which a CoPt alloy layer is laminated via a Pt layer, and the CoPt alloy layer has a Co content of 25 to 75 atomic%. (2) Co content of the CoPt alloy layer is 35 to 60 atom%.
The magnetic multilayer film according to (1) above. (3) The thickness of the CoPt alloy layer is 0.5 to 2 nm, and P
The magnetic multilayer film according to (1) or (2) above, wherein the thickness of the t layer is 0.5 to 2 nm. (4) The above-mentioned (1) to (3), wherein the thickness from the lowermost CoPt alloy layer to the uppermost CoPt alloy layer is 5 to 50 nm.
Any of the magnetic multilayer film. (5) The above (1) to (1) including a metal underlayer containing at least one of Pt, Pd, Au, Ag, W, Ir and Cr.
The magnetic multilayer film according to any one of (4). (6) The thickness of the metal underlayer is 2 to 20 nm (5)
Magnetic multilayer film. (7) A method for producing a magnetic multilayer film according to any one of (1) to (6), which comprises a step of forming a magnetic multilayer film on a substrate at 80 to 150 ° C. by a vapor deposition method. Manufacturing method. (8) The method for producing a magnetic multilayer film according to (7), wherein the atmospheric pressure during vapor deposition is 1 × 10 ⁻⁷ Torr or less. (9) A magneto-optical recording medium having the magnetic multilayer film according to any one of (1) to (6) as a recording film.

[0008]

In the present invention, the Pt intermediate layer is introduced into the CoPt alloy to form the CoPt alloy / Pt multilayer film structure.
As a result, a large Kerr rotation angle can be obtained in the short wavelength region even when the substrate temperature during film formation is as low as 150 ° C. or lower.
Moreover, since it exhibits a large perpendicular magnetic anisotropy, that is, a high squareness ratio and a high coercive force, a high C / N is obtained when applied to a magneto-optical recording medium, and the stability of recorded information is also improved. Further, the magnetic multilayer film of the present invention has a small decrease in perpendicular magnetic anisotropy due to thermal influence.

Therefore, the magnetic multilayer film of the present invention can be used as a recording film of a magneto-optical recording medium using a polymer resin substrate such as a polycarbonate substrate, and in that case, a high C
/ N is obtained, and repetitive rewriting characteristics of 10 ⁶ times or more are obtained.

Since the conventional Co / Pt multilayer film has a very thin Pt layer thickness of about 1 nm and a Co layer thickness of about 0.2 to 0.5 nm, a multilayer film of the same film structure can be produced with good reproducibility. However, the CoPt alloy / Pt multilayer film of the present invention does not require so strict control of layer thickness and composition control, and thus is relatively easy to manufacture.

The CoPt alloy / Pt multilayer film structure is
This is reported in JP-A-3-252940. However, in the multilayer film described in the publication, since the ratio of Pt in the CoPt alloy film is as small as 1 to 20 atomic%, the effect of the present invention cannot be realized. Particularly, when the substrate temperature is low, the squareness ratio of the Kerr loop is low. Becomes smaller. The Kerr rotation angle is generally large when the proportion of Co is high, but even if the Kerr rotation angle is large, unless the squareness ratio is 0.9 or more, particularly 0.95 or more, a high C / C ratio is obtained when applied to a magneto-optical recording medium. N cannot be obtained. The preferred method of forming the magnetic multilayer film of the present invention is the ultra-high vacuum vapor deposition method, but in this publication, the sputtering method is used to form the multilayer film, which is also different.

[0012]

Specific Structure The specific structure of the present invention will be described in detail below.

FIG. 1 shows a schematic view of the cross-sectional structure of the magnetic multilayer film of the present invention. The magnetic multilayer film of the present invention is one in which the CoPt alloy layer 4 is laminated via the Pt layer 3. In the illustrated example, the metal underlayer 2 is provided between the lowermost CoPt alloy layer 4 and the substrate 1.

The Co content of the CoPt alloy layer is preferably 25 to 75 atom%, more preferably 35 to 60 atom%.
Is. When Co is too large, good perpendicular magnetic anisotropy cannot be obtained, and when Pt is too large, a sufficient Kerr rotation angle cannot be obtained. The specific composition of the CoPt alloy layer is appropriately determined within the above range in consideration of the thickness of the Pt layer. Other elements such as Fe, Sc, Ti, V, Cr, Mn, Ni, Cu, Zn are contained in the CoPt alloy layer.
3d transition elements such as Pd, Y, Zr, Nb, Mo, R
4d transition elements such as u, Rh, and Ag; Au, Hf, Ta,
5d transition elements such as W, Re, Os, Ir; Gd, Tb,
Dy, Ho, Er, Yb, Lu, La, Ce, Pr, N
rare earth elements such as d, Sm, Eu; B, Al, Ga, In
3B group elements such as; 4B group elements such as C, Si, Ge; N,
Group 5B elements such as P and Bi can be included.
When such other element is added to the CoPt alloy layer, the content of the other element is preferably 30 atom% or less, more preferably 20 atom% or less.

Thickness of each Pt layer and each C in the magnetic multilayer film
Although the thickness of the oPt alloy layer is not particularly limited,
If the CoPt alloy layer is too thick, it is necessary to raise the substrate temperature to some extent in order to obtain good perpendicular magnetic anisotropy. If the CoPt alloy layer is too thin, the Kerr rotation angle becomes small. The layer thickness is preferably 0.5-2 nm, more preferably 0.5-1.5 nm. On the other hand, the thicker the Pt layer is, the better perpendicular magnetic anisotropy can be obtained.
Since the average density of o becomes low, the Kerr rotation angle becomes small. As described above, the thickness of the Pt layer is appropriately determined in accordance with the composition of the CoPt alloy layer and the thickness thereof, but is preferably 0.5 to 2 nm, more preferably 0.5.
~ 1.5 nm. The thickness of the CoPt alloy layer and Pt
The ratio CoPt / Pt to the layer thickness is preferably between 1/2 and
2, more preferably 2/3 to 3/2. If this ratio is too small, the Kerr rotation angle becomes small, and if this ratio is too large, it is necessary to raise the substrate temperature to some extent in order to obtain good perpendicular magnetic anisotropy.

The total thickness of the multilayer film is not particularly limited, but if it is too thick, the squareness ratio of the magnetic Kerr curve and the coercive force tend to decrease, so that the total thickness (from the CoP alloy layer of the bottom layer to the CoPt alloy of the top layer) The thickness up to the layer) is preferably 50 nm or less. Further, the thinner the total thickness, the shorter the film formation time can be. However, if the film becomes too thin, the film will not be a continuous film but will have an island structure, and the Kerr rotation angle will be small. Therefore, the total thickness is preferably 5 nm or more.

The number of CoPt alloy layers in the magnetic multilayer film may be two or more, but it is preferably three or more in order to ensure a sufficient total thickness. It may be appropriately determined depending on the situation.

The metal underlayer 2 provided between the lowermost CoPt alloy layer 4 and the substrate 1 is made of Pt, Pd, Au, A.
It is preferably composed of a metal containing at least one of g, W, Ir and Cr, and particularly preferably composed of Pt. By providing the underlayer, the perpendicular magnetic anisotropy can be improved and the coercive force and the squareness ratio can be increased. The thickness of the underlayer is preferably 2 to 20 nm, more preferably 3 to 6 nm. If the underlayer is too thin, the effect of providing the underlayer will be insufficient, and if it is too thick, it will be difficult to read information by applying a laser from the substrate side when applied to a magneto-optical recording medium.

A metal protective layer 5 may be provided on the uppermost CoPt alloy layer as shown in the figure. Pt or the like may be used for the metal protective layer 5. The metal protective layer preferably has a thickness of about 0.5 to 2 nm.

For forming the magnetic multilayer film of the present invention, it is preferable to use a vacuum vapor deposition method, particularly an ultrahigh vacuum vapor deposition method. Specifically, it is preferable to prepare two evaporation sources of Co and Pt, and to deposit Pt on the substrate at a constant rate while depositing Co at a constant cycle and rate. The atmospheric pressure during vapor deposition is preferably 1 × 10 ⁻⁷ Torr or less, more preferably 2 × 10 ⁻⁸ Torr or less, and further preferably 1 ×.
It should be 10 ^-8 Torr or less. Although there is no particular lower limit to the pressure, it is usually 5 × 10 ⁻⁹ Torr or more during vapor deposition. C
The vapor deposition rates of o and Pt are not particularly limited, but are preferably 0.1 in order to improve the periodicity and reproducibility.
nm / sec or less, more preferably 0.01 to 0.05 nm / sec. By performing vapor deposition under these conditions, a CoPt alloy / Pt multilayer film having good characteristics can be easily formed.

The magnetic multilayer film of the present invention thus formed has a (111) oriented fcc structure.

The magnetic multilayer film of the present invention can be formed by using an ordinary resin substrate, and a polycarbonate substrate which is inexpensive but has low heat resistance can also be used. When a substrate temperature exceeding 200 ° C. is required, it is necessary to use an expensive heat-resistant resin substrate, but in the present invention, the substrate temperature is 2
00 ° C or below, 150 ° C or below where normal resins can be used without problems, and even polycarbonate substrates can be used safely 11
Good perpendicular magnetic anisotropy and high coercive force can be obtained even at 0 ° C. or lower, and a large Kerr rotation angle can be obtained even with reproducing light having a short wavelength. For example, a squareness ratio of 0.9 or more can be easily obtained, and it can be 0.95 or more, particularly 1.0. Further, a coercive force of 0.4 kOe or more can be easily obtained, and it can be set to 0.5 kOe or more. Also, a Kerr rotation angle of 0.20 ° or more can be easily obtained,
The above can be applied. Moreover, the magnetic multilayer film of the present invention thus formed has a small decrease in perpendicular magnetic anisotropy due to thermal influence. Therefore, when the magnetic multilayer film of the present invention is used as a recording film of a magneto-optical recording medium, high C /
An excellent repetitive rewriting characteristic of N is obtained.

A magneto-optical recording medium having the magnetic multilayer film of the present invention as a recording film generally has a first dielectric film 12, a recording film 13, and a second dielectric film on a substrate 1, as shown in FIG. 1
4, the reflective film 15 and the protective coat 16 are arranged in this order.

Since the recording light and the reproducing light are normally irradiated through the substrate, the substrate is made of a transparent material such as resin or glass. In the present invention, the polycarbonate substrate can be used as described above. On the surface of the substrate,
Optical head guide grooves and pits indicating addresses are formed in advance.

The first dielectric film and the second dielectric film are C /
It is provided to improve N and reliability of the recording film. The thickness of the first dielectric film is about 40 to 200 nm, and the thickness of the second dielectric film is about 10 to 100 nm. Each dielectric film is preferably composed of a dielectric substance made of various oxides, carbides, nitrides, sulfides, or mixtures thereof (LaSiON, etc.). It is preferable that these dielectric films are formed by a vapor phase film forming method such as a sputtering method.

The reflective film is provided to improve C / N. The material forming the reflective film is Au, Ag, Pt, A
Metals such as 1, Ti, Cr, Ni, and Co, alloys containing these, or compounds containing these are preferable. The reflective film is preferably formed by a vapor phase film forming method such as a sputtering method. The thickness of the reflective film is 30 to 20.
It is preferably about 0 nm.

The protective coat is a resin film provided to protect the laminated film up to the reflective film. The resin constituting the protective coat is not particularly limited, but it is preferably a cured product of a radiation curable compound. The radiation-curable compound preferably has an acrylic group, and a coating film containing this and a photopolymerization sensitizer or an initiator is preferably cured by ultraviolet rays or electron beams to form a protective coat.
The thickness of the protective coat is usually 1 to 30 μm, preferably 2 to 20 μm.

[0028]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Example 1 A CoPt alloy / Pt multilayer film was formed on a rotating substrate by ultra-high vacuum deposition,
A sample for measurement was used. Corning 7059 glass was used for the substrate. The film forming conditions are as follows. As described above, two evaporation sources of Co and Pt were prepared, and Co was vapor-deposited at a constant cycle and rate while continuously depositing Pt on the substrate at a constant rate. Ultimate pressure is 1 × 1
0 ^-9 Torr, the pressure during film formation is 2 × 10 ^-8 to 8 × 10 ^-8 Torr
And The vapor deposition rate was 0.02 nm / sec for both Co and Pt. Select the substrate temperature from the range of 25-150 ℃,
The substrate temperature during film formation was constant. The film composition is fluorescent X
It was measured by line analysis.

Substrate Temperature Dependence of Magnetic Kerr Curve FIGS. 3A to 3E show Pt (5 nm) / [Pt (1 nm)
/ Co60Pt40 (1 nm)] 10 / Pt (1 nm) multilayer film shows the substrate temperature dependence of the magnetic Kerr curve at a wavelength of 680 nm. The above expression of the multilayer film is such that one unit of a Pt layer having a thickness of 1 nm and a CoPt alloy layer having a thickness of 1 nm are stacked as one unit, and 10 units are laminated on a Pt layer having a thickness of 5 nm. It represents a Pt layer having a thickness of 1 nm laminated as a metal protective layer. The atomic percentage composition of the CoPt alloy layer is C
o60Pt40. Therefore, CoPt of the bottom layer
The thickness from the alloy layer to the uppermost CoPt alloy layer is 19
The thickness of the metal underlayer is 6 nm.

From FIG. 3, good perpendicular magnetic anisotropy is obtained even at a substrate temperature of 150 ° C. or less, that is, a squareness ratio of 1 and 0.5.
It can be seen that a coercive force greater than kOe can be obtained. Substrate temperature 2
A squareness ratio of 0.5 was obtained even at 5 ° C, but the substrate temperature was 8
It can be seen that a squareness ratio of 1 is obtained at 0 ° C. or higher. When a film is formed at a substrate temperature of 100 ° C., a coercive force of 0.5 kOe and a squareness ratio of 1 are obtained.

Heat Treatment Temperature Dependence of Squareness Ratio The multilayer film formed at a substrate temperature of 100 ° C. was subjected to heat treatment, and the squareness ratio after the treatment was measured. FIG. 4 shows the heat treatment temperature dependence of the squareness ratio of this multilayer film as an example of the present invention. The curve shown in FIG. 4 as a comparative example is Pt (5 nm) /
[Pt (1 nm) / Co (0.3 nm)] 10 / Pt (1 n
m) Multilayer film, that is, Pt / Co multilayer film. As shown in FIG. 4, since the multilayer film of the present invention has a small decrease in perpendicular magnetic anisotropy due to the thermal effect, it can be seen that the repetitive rewriting characteristics are improved when applied to the magneto-optical recording film.

Wavelength Dependence of Kerr Rotation Angle FIG. 5 shows the wavelength dependence of the Kerr rotation angle of the above-mentioned multilayer film formed at a substrate temperature of 100 ° C. The applied magnetic field is 15 kOe
And It was confirmed that the Kerr rotation angle increased as the measurement wavelength became shorter, and a Kerr rotation angle of 0.32 ° was obtained at a wavelength of 400 nm. From FIG. 5, it can be confirmed that the multilayer film of the present invention can obtain a sufficiently large Kerr rotation angle in the short wavelength region.

The substrate temperature at the time of forming the film for changing the composition of the CoPt alloy layer is set to 100 ° C., the Pt layer thickness and the CoPt alloy layer thickness are fixed at 1 nm, respectively.
Table 1 shows the squareness ratio, the coercive force, and the Kerr rotation angle at a wavelength of 400 nm when the composition of the alloy layer was changed.

[0035]

[Table 1]

In Table 1, the Kerr rotation angle increases as the Co content of the CoPt alloy layer increases, but when the Co content is 80 atomic%, the squareness ratio decreases. When applied to a magneto-optical recording medium, high C / N cannot be obtained. The coercive force tends to increase as the Co content decreases.
When the content is 15 atomic%, the coercive force is drastically reduced, and therefore high reliability cannot be obtained when applied to a magneto-optical recording medium. It can be seen from Table 1 that all of the squareness ratio, the coercive force, and the Kerr rotation angle are good in the range where the Co content of the CoPt alloy layer is 25 to 75 atom%, particularly 35 to 60 atom%.

[0037] when changing the thickness of the CoPt alloy layer thickness changes CoPt alloy layer, squareness ratio, the Kerr rotation angle in the coercivity and the wavelength 400 nm, are shown in Table 2.

[0038]

[Table 2]

From Table 2, the thickness of the CoPt alloy layer is 0.5.
It can be seen that all of the squareness ratio, the coercive force, and the Kerr rotation angle are good in the range of up to 2 nm, particularly in the range of 0.5 to 1.5 nm.

Change in Pt Layer Thickness and Metal Underlayer Thickness When the thickness of the Pt layer between layers is changed and when the thickness of the metal underlayer is changed, squareness ratio, coercive force and wavelength 4
The Kerr rotation angle at 00 nm is shown in Table 3.

[0041]

[Table 3]

From Table 3, it can be seen that the coercive force can be improved by providing the metal underlayer having a predetermined thickness. Further, it is confirmed that the thicker the Pt layer between layers is, the better perpendicular magnetic anisotropy is obtained, but the Kerr rotation angle becomes smaller. The thickness of the Pt layer between the layers is 0.5 to 2 nm, especially 0.5 to
It can be seen that the squareness ratio, the coercive force, and the Kerr rotation angle are all favorable in the range of 1.5 nm.

Crystal orientation The X-ray diffraction chart of the multilayer film of the present invention shown in Table 4 is shown in FIG.
Shown in Further, FIG. 7 shows an X-ray diffraction chart of the multilayer film of the comparative example shown in Table 4. Table 4 shows the relationship between the crystal orientation and the squareness ratio of each multilayer film. The crystal orientation is Co
Peak intensity I (002) of Pt (002) and C of fcc
Ratio I of oPt (111) to peak intensity I (111)
It was evaluated by (002) / I (111).

[0044]

[Table 4]

From Table 4, it can be seen that the ratio of CoPt (002) is small, and that the CoPt (111) peak intensity of fcc is relatively strong, the multilayer film of the present invention has a high squareness ratio. In addition, this tendency is Appl. Phys. Let
t. C, 61, 2726, 1992
This is in agreement with the tendency for o ₂₈ Pt ₇₂ alloy. In the present invention, good perpendicular magnetic anisotropy can be obtained even when the substrate temperature is low, because the (111) orientation is easy even at low temperature by stacking the CoPt alloy layers through the Pt layer. Can be said.

Example 2 CoP under the same conditions as in Example 1
A magneto-optical disk was prepared by forming a t-alloy / Pt multilayer film as a recording film.

This magneto-optical disk was manufactured as follows using a multi-source ion beam sputtering device and an ultra-high vacuum multi-source deposition device.

Using an ion beam sputtering apparatus and an ultra-high vacuum multi-source deposition apparatus, a film was formed on the surface of a polycarbonate substrate having guide grooves and pits formed on the surface while rotating the substrate.

First, using an ion beam sputtering device,
The Si target was sputtered with an Ar ion beam, and at the same time, nitrogen ion beam assist was performed with another ion gun to form a first dielectric film of silicon nitride. Beam voltage of main ion gun is 1200V, beam current is 135mA, Ar gas flow rate is 10SCCM, beam voltage of assist ion gun is 350V, beam current is 10mA,
The nitrogen gas flow rate was 20 SCCM. The sputtering pressure at this time was 3.6 × 10 ⁻⁴ Torr. The thickness of the first dielectric film was 80 nm.

Next, the substrate having the first dielectric film formed thereon was taken out and set in an ultra-high vacuum multi-source vapor deposition apparatus to form a recording film. The recording film is Pt (5 nm) / [Pt (1 nm) / C
o60Pt40 (1 nm)] 10 / Pt (1 nm).

After forming the recording film, the substrate was set again in the ion beam sputtering apparatus to form a second dielectric film of silicon nitride. The sputtering conditions at this time were the same as those for forming the first dielectric film, but the thickness of the second dielectric film was 100 nm.
And

After forming the second dielectric film, an Al reflection film having a thickness of 50 nm was continuously formed in the ion beam sputtering apparatus. Ar gas was used as the sputtering gas and Al was used as the target, and sputtering was carried out at a sputtering gas pressure of 1.4 × 10 ⁻⁴ Torr, a beam voltage of 1200 V, and a beam current of 135 mA.

Finally, an ultraviolet curable resin film was formed to a thickness of about 1 μm to form a protective coat, and a magneto-optical disk was obtained.

The magneto-optical disk of the present invention thus produced was repeatedly recorded and erased to examine the rewriting characteristics. Recording was performed using a laser beam having a wavelength of 780 nm, a recording frequency of 2.5 MHz, a linear velocity of 5 m / s, and an optimum recording power of 7.2 mW. Next, the recorded signal is transferred to an external magnetic field of 400 Oe,
Erase Laser beam was completely erased with 7.4 mW. The change in carrier-to-noise ratio (CNR) when this was repeated many times was examined. The reproduction laser output was 1 mW.

As a comparative example, Pt / Co was applied to the recording film.
A magneto-optical disk using a multilayer film was also manufactured, and the characteristics were examined in the same manner as above. This Pt / Co multilayer film was formed using an ultra-high vacuum vapor deposition apparatus at a film forming pressure of 5 × 10 ⁻⁹ Torr and a film forming rate of 0.2 A / s. Pt thickness is 1.0 nm, Co
The layer thickness was 0.3 nm, and Pt, Co, and Pt were alternately laminated in this order. The top layer is a Pt layer with a total thickness of 14 nm. The films other than the recording film were formed in the same manner as the disc of the present invention.

FIG. 8 shows CN when rewriting is repeated.
The change in R (ΔCNR) is shown. In the disk of the comparative example, the CNR is remarkably lowered from around 10 ⁴ times, but in the disk of the present invention, the CNR is not lowered up to 10 ⁶ times.

The magneto-optical disk of the present invention described above is
The sample No. 105 in Table 1 has a multilayer film (square ratio of 1.0) as a recording film. The C / N of this magneto-optical disk was 52 dB. On the other hand, a magneto-optical disk having a multilayer film (square ratio 0.85) of Sample No. 107 in Table 1 as a recording film was prepared.
When N was measured, it was 35 dB.

From the results of the above examples, the effects of the present invention are clear.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a magnetic multilayer film of the present invention.

FIG. 2 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium.

FIG. 3 is a graph showing the substrate temperature dependence of a magnetic Kerr curve.

FIG. 4 is a graph showing the heat treatment temperature dependence of the squareness ratio.

FIG. 5 is a graph showing wavelength dependence of Kerr rotation angle.

FIG. 6 is an X-ray diffraction chart of the magnetic multilayer film of the present invention.

FIG. 7 is an X-ray diffraction chart of a multilayer film outside the scope of the present invention.

FIG. 8 shows the number of repeated rewritings and the change in CNR (ΔCN
It is a graph which shows the relationship with R).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Metal underlayer 3 Pt layer 4 CoPt alloy layer 5 Metal protective layer 12 First dielectric film 13 Recording film 14 Second dielectric film 15 Reflective film 16 Protective coat

Claims (9)

[Claims] 1. A magnetic multilayer film in which a CoPt alloy layer is laminated via a Pt layer, and the CoPt alloy layer has a Co content of 25 to 75 atomic%. 2. The Co content of the CoPt alloy layer is 35 to 6
The magnetic multilayer film according to claim 1, wherein the content is 0 atomic%. 3. The magnetic multilayer film according to claim 1, wherein the CoPt alloy layer has a thickness of 0.5 to 2 nm, and the Pt layer has a thickness of 0.5 to 2 nm. 4. The lowermost CoPt alloy layer to the uppermost C
The thickness up to the oPt alloy layer is 5 to 50 nm.
3. The magnetic multilayer film according to any one of 3 above. 5. The magnetic multilayer film according to claim 1, further comprising a metal underlayer containing at least one of Pt, Pd, Au, Ag, W, Ir and Cr. 6. The magnetic multilayer film according to claim 5, wherein the metal underlayer has a thickness of 2 to 20 nm. 7. A method for producing a magnetic multilayer film according to claim 1, which is 80 to 150 ° C. by a vapor deposition method.
A method for manufacturing a magnetic multilayer film, the method including the step of forming a magnetic multilayer film on a substrate. 8. The method for producing a magnetic multilayer film according to claim 7, wherein the atmospheric pressure during vapor deposition is 1 × 10 ⁻⁷ Torr or less. 9. A magneto-optical recording medium having the magnetic multilayer film according to claim 1 as a recording film.