JPH0660448A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve coercive force and Kerr rotation angle by forming an artificial lattice film in a manner that the substrate side of the film has shorter laminating period than other part and specifying the thickness in the substrate side of the aritficial lattice film. CONSTITUTION:In the artificial lattice film, the laminating period in the area 2 near the substrate 1 differs from that in other part 3. The area 2 has a shorter laminating preriod than in the part 3 and is formed to have thickness between >=10% and <=80% of the whole artificial film. In the part 2, the laminating period changes and has the film thickness in the above range to obtain a large Kerr angle and total contribution of the area having large magneto-optical effect and coercive force does not decrease. Thereby, metal can be deposited by sputtering, and by controlling the sputtering conditions, an artificial lattice film of different laminated period can be formed. For example, by sputtering Co and Pt targets at one time while a substrate holder is rotated to alternately pass above the targets, and by changing the rotation number, an artificial lattice film of different period can be formed.

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, and more particularly to a short wavelength compatible magneto-optical recording medium.

[0002]

2. Description of the Related Art As a high-density magneto-optical recording medium, a magneto-optical recording medium having an artificial lattice film in which Co layers and Pt layers and / or Pd layers are alternately laminated on a substrate has been proposed ( JP-A-2-56752). Such a magneto-optical recording medium exhibits a large magneto-optical effect particularly for light having a wavelength of 500 nm or less, and since the recording layer does not contain a metal such as a rare earth metal that is easily oxidized, it is said to have excellent corrosion resistance. There is.

Such Co and Pt and / or Pd
The magnitude of the magneto-optical effect (Kerr rotation angle) that governs the reproducing performance in a magneto-optical recording medium in which
Although there is a positive correlation with the composition ratio, when the Co composition ratio is increased, the Curie temperature rises, high recording power is required, and the recording sensitivity decreases. That is, the Co composition ratio in the medium is adjusted to the configuration of the recording system and the light source used for recording and reproduction,
A Co composition ratio that gives desired recording characteristics is selected.

[0004]

Generally, in magneto-optical recording, a material having both a Kerr rotation angle and a coercive force, which are characteristics of a magnetic layer, are sufficiently large for stable recording and reproduction. .

However, in a recording medium in which Pt and Co are alternately laminated at a composition ratio that can obtain desired recording characteristics, a medium having a uniform lamination period should have a large coercive force and a large Kerr rotation angle. Was difficult.

An object of the present invention is to provide a magneto-optical recording medium having high values of both coercive force and Kerr rotation angle.

[0007]

As a result of various studies to achieve the above object, the present inventors have found that Pt, Co and / or Pt and Co and / or The present invention has been completed by finding that a magneto-optical recording medium having a large coercive force and Kerr rotation angle and excellent recording characteristics can be obtained by changing the stacking period with Pd.

That is, according to the present invention, a Co layer and a Pt layer are formed on a substrate.
In a magneto-optical recording medium having a recording layer of an artificial lattice film in which layers and / or Pd layers are alternately laminated, a portion of the artificial lattice film on the substrate side (1) has a lamination cycle longer than that of the other portion (2). It is a short artificial lattice film, and the part (1) is 10 of the total film thickness.
The present invention relates to a magneto-optical recording medium having a thickness of 80% to 80%. Next, the present invention will be described in more detail.

FIG. 1 is a diagram showing an embodiment of a magneto-optical recording medium of the present invention laminated using Co and Pt. In the figure, 1 is a substrate, and a glass or polymer substrate is usually used. In the figure, 2 is a portion of the artificial lattice film having a short stacking period (1), and 3 is a portion of the artificial lattice film having a long stacking period (2).

In the present invention, the portion having a different stacking period is the portion (1) on the substrate side of the artificial lattice film,
In the other portion (2), which is close to the substrate and has a thickness of 10% or more and 80% or less of the total film thickness (portion (1) in FIG. 1), Co / Pt (and / or Pd) stacking period is shortened, and other parts (Same as (2)
Part) is characterized by making it longer than this.

Even if the thickness of the portion (1) in which the stacking period is changed is changed outside the above range, if the thickness is less than 10%, the contribution of the portion having a large magneto-optical effect to the whole is small, and If it is more than 80%, the contribution of the part having a large coercive force to the whole becomes small, and the effect of the present invention cannot be obtained.

A preferred specific example of the above-mentioned stacking period in the present invention is that Co is less than 0.
5 to 1.5 atomic layer, Pt (and / or Pd) 1 to 6
It is to be an artificial lattice of atomic layers, and in the part (2), the value is larger than the value in the part (1) and C
o is 1 to 2.5 atomic layer and Pt (and / or Pd) is 2
It is to be an artificial lattice of 8 atomic layers. Outside of the above range, the effect of the present invention cannot be sufficiently obtained.

In the manufacture of the magneto-optical recording medium of the present invention, a method of laminating these metals on the surface of the substrate by, for example, a sputtering method can be used. By appropriately setting the sputtering conditions, artificial lattices having different laminating periods can be used. A film can be formed.

That is, as an example of the manufacturing method, while simultaneously sputtering a target of a metal, such as Co and Pt (and / or Pd), which is partitioned by a partition plate so that the sputtered atoms do not mix with each other, the substrate is By rotating the substrate holder that alternately passes over these targets, and changing the number of rotations of the substrate holder at this time during the formation of the artificial lattice film, a method of forming artificial lattices with different periods is used. is there.

Co / P formed by sputtering
In the t (and / or Pd) artificial lattice, the coercive force has the maximum value at a constant Co layer thickness, but when the composition ratio of Co and Pt is the same, the shorter the stacking period, the larger the magnetic Kerr rotation angle. In this case, in order to obtain a larger magnetic Kerr rotation angle, the property of the artificial lattice having a shorter period is to contribute to this.

The present invention has both advantages by having a structure having both an artificial lattice structure having a large coercive force and an artificial lattice structure having a large magnetic Kerr rotation angle. Is a feature. According to the finding of the present inventor, the portion close to the substrate, that is, the initial formation layer of the artificial lattice film has little influence on the coercive force of the film. That is, an artificial lattice (layer (1) in FIG. 1) having a short period showing a large magnetic Kerr rotation angle is formed on the portion of the artificial lattice film, which is the recording layer, on the side of the substrate that is the recording read side, and the remaining portion is formed. A large magnetic Kerr rotation angle and a large coercive force can be obtained as a whole by forming an artificial lattice (layer (2) in FIG. 1) having a large coercive force. The ratio of the (1) layer to the (2) layer in the artificial lattice film is (1) when the (1) layer is less than 10%.
The ratio of the (1) layer occupying in the artificial lattice film does not show the characteristic of the large Kerr rotation angle of the layer, and when the (2) layer is smaller than 20%, the film does not show the large coercive force of the (2) layer. Should be in the range of 10% to 80%.

[0017]

Example 1 Xe was used as a sputtering gas, and an artificial lattice film was formed on a water-cooled glass substrate by a high frequency magnetron sputtering method. The gas pressure during sputtering was about 5 mmTorr, and the film formation rate was about 1 to 5 A / sec.

First, Pt is used as a portion (1) having a short stacking period.
The layers were alternately repeated 16 times (about 100 angstroms) so that the layers were 4.5 A and the Co layers were 1.5 A, and then 12 Pt layers were formed as a portion (2) having a long stacking period.
The A and Co layers were alternately laminated 7 times (about 100 Å) so as to have a thickness of 4 A. Similarly,
As shown in Table 1, artificial lattice films having different periods were formed as a portion (1) having a short stacking period, and the magneto-optical effect and the coercive force of each of the artificial lattice films were measured from the substrate side. The measurement results are shown in Table 1. In addition, these measurements are 400 nm
Was carried out by a Kerr loop tracer using light of the wavelength.

Table 1 (1) layer (2) layer Sample Co thickness Pt thickness Co thickness Pt thickness Kerr rotation angle Coercive force (A) (A) (A) (A) (degree) (Oe) a 1.5 4.5 4 12 0.53 650 b 2 6 4 12 0.53 700 c c 2.5 7.5 4 12 0.51 720 d 3 9 4 12 0.49 750

[0020]

Example 2 A film was formed on a glass substrate under the same conditions as in Example. First, Pt 7.5A /
After forming a film in the range of about 50 angstroms to 150 angstroms at a stacking cycle of Co 2.5 A, the portion (2) having a long stacking cycle was continuously stacked at a cycle of Pt12A / Co4A, and the total film thickness was about 200 A. . The measurement results of the magneto-optical effect and the coercive force performed in the same manner as in Example 1 are
Shown in the table.

Table 2 Sample (1) Layer thickness (A) (2) Layer thickness (A) Kerr rotation angle (degree) Coercive force (Oe) e 50 150 0.48 740 f 100 100 0.51 720 g 150 50 0.54 620

[0022]

[Comparative Example] About 200 A of a film having a uniform stacking period was formed on a glass substrate under the same conditions as in the example, and the magneto-optical effect and coercive force were measured under the same conditions. The measurement results are shown in Table 3.

Table 3 Sample Co layer thickness Pt layer thickness (A) Kerr rotation angle (degree) Coercive force (Oe) h 2.0 6.0 0.56 450 i 3.0 9.0 9.0 0.51 640 j 4.0 12.0 0.44 760 k 5.0 15.0 0.39 650 From the results of Example 1, the present invention comprises two parts (1) and (2) having different stacking periods. The composite type artificial lattice film has excellent characteristics that both the magnetic Kerr rotation angle of 0.5 degree or more and the coercive force of 700 Oe or more, which cannot be obtained by the simple type artificial lattice film having the uniform lamination period shown in the comparative example. You can see that it has been obtained.

Further, as is clear from the results of Example 2, the characteristics of the medium can be continuously changed by changing the ratio of the portion (1) having a short lamination period and the portion (2) having a long lamination period. Possible and adopted media structure,
According to the wavelength of the light source used for recording / reproduction, etc., the proportion of the portion (1) having a short stacking period in the artificial lattice film may be selected within the above range.

When these artificial lattice films are used as a magneto-optical recording medium, a magnetic material layer and a dielectric layer are used as in a magneto-optical recording medium using a rare earth-transition metal amorphous alloy which has already been put into practical use. It is effective to combine and stack body layers to improve recording / reproducing characteristics.

For example, a 4-layer film type in which a dielectric layer, a magnetic layer, a dielectric layer, and a reflection layer are laminated in this order on a substrate is adopted, and the artificial lattice is used in the case of recording and reproducing from the substrate side. A suitable thickness of the magnetic layer is 50 to 300A.

Further, when changing the stacking period during film formation, the same effect can be obtained by changing the sputter rate instead of the method of changing the rotation speed of the substrate as in this embodiment. In that case, Even if the composition ratio of Pt and Co is slightly different between the part (1) having a short stacking period and the part (2) having a long stacking period, it is not excluded from the scope of the present invention.

Further, Pt and C are used in Examples and Comparative Examples.
Although the case where the composition ratio of o is 3: 1 (volume ratio) is shown, the present invention is not limited to this, and Pt and Co may be selected so as to obtain a desired recording sensitivity depending on the recording / reproducing system used. The composition ratio may be changed.

Further, due to the convenience of the film forming apparatus, it is possible to obtain substantially the same effect as the embodiment even when the lamination period cannot be changed sharply as in the embodiment and the lamination period is continuously changed.

[0030]

As is apparent from the above description, according to the present invention, a recording medium having a large magneto-optical effect and coercive force can be obtained without raising the Curie temperature, and therefore, it is preferably combined with a short wavelength light source and a peripheral optical system. This enables magneto-optical recording with high recording density and high CN ratio.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a magneto-optical recording medium of the present invention.

[Explanation of symbols]

 1: Substrate 2: Part of artificial lattice film with short stacking period (1) 3: Part of artificial lattice film with long stacking period (2)

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[Procedure amendment]

[Submission date] October 7, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

That is, according to the present invention, a Co layer and a P layer are formed on a substrate.
In a magneto-optical recording medium having an artificial lattice film in which t layers and / or Pd layers are alternately laminated as a recording layer, a portion (1) on the substrate side of the artificial lattice film has a lamination cycle longer than that of the other portion (2). Is a short artificial lattice film, and the portion (1) has a thickness of 10% or more and 80% or less of the total film thickness of the artificial lattice film . Next, the present invention will be described in more detail.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

In the present invention, the portion having a different stacking period is the portion (1) on the substrate side of the artificial lattice film.
When a remaining portion (2), close to the substrate, artificial
In the portion having a thickness of 10% to 80% of the total thickness of the lattice film (portion (1) in FIG. 1), Co / Pt
The stacking period of (and / or Pd) is shortened, and the other portion (portion (2)) is longer than this.

Claims (3)

[Claims] 1. A Co layer, a Pt layer and / or a P layer on a substrate.
In a magneto-optical recording medium having an artificial lattice film in which d layers are alternately laminated as a recording layer, a portion (1) of the artificial lattice film on the substrate side has a shorter lamination period than other portions (2). And a portion (1) has a thickness of 10% or more and 80% or less of the total film thickness. 2. The portion (1) comprises an artificial lattice of Co: 0.5 to 1.5 atomic layers and Pt: 1 to 6 atomic layers.
The magneto-optical recording medium described. 3. The artificial lattice film, part (2) is Co: 1.
3. The magneto-optical recording medium according to claim 1, comprising an artificial lattice of .about.2.5 atomic layer, Pt: 2 to 8 atomic layer, and having a value larger than that of the portion (1).