JPH09293284A - Magneto-optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical improved in jitter property. SOLUTION: A dielectric layer 5, a recording layer 6 provided with successively a 1st layer 6a composed of an amorphous GdFeCo alloy and a 2nd layer 6b composed of an amorphous TbDyFeCo alloy, a dielectric layer 7 and a reflection layer 8 are successively laminated on a substrate 1. And both of the 1st layer 6a and the 2nd layer 6b are enriched in transition metal and the coercive force of the recording layer 6 is controlled to 7-16kOe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in magneto-optical disks.

[0002]

2. Description of the Related Art According to Japanese Patent Laid-Open No. 61-117747,
A magneto-optical disk having a laminated structure in which a low coercive force layer of GdFeCo having a high Curie point and a high coercive force layer of TbFe having a low Curie point are exchange-coupled has been proposed, and in Japanese Patent Publication No. 3-9545, TbFe and A stack of a DyFe recording layer and a reproducing layer of GdFe or GdFeBi has been proposed, and both stack structures achieve high C / N.

[0003]

However, according to the magneto-optical disk of the above-mentioned laminated structure, the read output is increased, so that the carrier level can be increased. On the other hand, on the other hand, the reproducing layer and the recording layer. Since the change in the coercive force Hc at the interface with the and the coercive force Hc is apparently the same due to the exchange coupling, the pit shape is sharp at the interface between the low coercive force layer and the high coercive force layer due to the difference in the Curie points of the two layers. However, there is a problem that the jitter increases due to the change. Therefore, an object of the present invention is to provide a high-performance magneto-optical disk with improved jitter characteristics.

[0004]

In the magneto-optical disk of the present invention, a first dielectric layer, a first layer made of an amorphous GdFeCo alloy and a second layer made of an amorphous TbDyFeCo alloy are sequentially provided on a transparent disk substrate. The recording layer, the second dielectric layer, and the reflective layer, which are sequentially laminated,
Further, both the first layer and the second layer are rich in transition metal, and the coercive force of the recording layer is set to 7 to 16 kOe.

[0005]

FIG. 1 shows a magneto-optical disk M according to the present invention.
FIG. 2 is a cross-sectional view taken along the line XX of FIG. 1. Further, FIG. 3 shows a layer structure of a thin film forming the magneto-optical disk M.

A substrate 1 made of a polycarbonate resin is used as the transparent disk substrate, and a large number of tracking grooves 2 are formed concentrically on one side of the substrate 1, and a hub mounting hole 3 is formed in the center thereof. It is provided. The surface on which the tracking groove 2 is formed is covered with the thin film 4.

The thin film 4 has a dielectric layer 5 made of sialon having a thickness of, for example, 500 to 900 Å as a first dielectric layer, a recording layer 6, and a sialon having a thickness of, for example, 50 to 200 Å as a second dielectric layer. Dielectric layer 7 consisting of
And a reflective layer 8 made of titanium-containing aluminum having a thickness of 600 to 1000 Å and a protective resin layer 9 made of an ultraviolet curable resin. The dielectric layer 5, the recording layer 6, the dielectric layer 7, and the reflective layer 8 are formed into a film by sputtering, and then the protective resin layer 9 is formed by coating.

The dielectric layers 5 and 7 may be formed of silicon oxide, aluminum nitride, titanium oxide, tantalum oxide, etc. other than sialon.
Regarding titanium, aluminum, titanium,
It may be formed of at least one metal or alloy of Au, Ag, Cu, Pt, Cr and Ni.

The recording layer 6 is made of amorphous GdFeCo.
First layer 6a made of alloy and amorphous TbDyF
It has a laminated structure in which a second layer 6b made of an eCo alloy is sequentially laminated, and both layers 6a and 6b are exchange-coupled. Then, both the first layer 6a and the second layer 6b may be rich in transition metal, whereby the directions of the magnetic moment and the magnetization are the same in both layers, and the coupling is stabilized.

Further, the coercive force of the recording layer 6 is set to 7 to 16 kOe.
When set to, jitter is further improved. In order to set the coercive force in this way, it can be obtained by controlling the ratio of the rare earth element and the transition metal element in both layers, but in reality, the coercive force of the first layer 6a is set to 1 to 2 kOe. 2 layers 6
This can be achieved by setting the coercive force of b to 8 to 17 kOe.

Then, in the magneto-optical disk M having the above structure, while the substrate 1 is rotated, a laser beam having a wavelength of 680 nm or the like is irradiated through the substrate 1 and tracking is performed along the tracking groove 2, the laser beam is a dielectric. The recording layer 6 reaches the recording layer 6 through the layer 5, a part of the recording layer 6 passes through the recording layer 6, and the reflecting layer 8 passes through the dielectric layer 7.
And the reflected light reaches the recording layer 6.

Thus, according to the magneto-optical disk M of the present invention, by providing the thin film 4 having the above-mentioned layer structure, the coercive force Hc at the boundary between the first layer 6a which is the reproducing layer and the second layer 6b which is the reading layer. Gradually changes (because Co is a constituent atom common to both layers, the coupling of the magnetic moment at the interface becomes stronger), and the rare earth element of TbDy is added to the second layer 6b. By using, the rare earth element of only conventional Tb or GdD
Bonding at the interface is stronger than in the case where the rare earth element of y is used, which stabilizes the readout layer, resulting in a smaller jitter value.

The composition and film thickness of the first layer 6a and the second layer 6b are preferably limited as follows. First layer 6a Gda Feb Coc 0.15 <a ≦ 0.30, preferably 0.18 <a ≦ 0.
20 0.50 ≦ b ≦ 0.80, preferably 0.60 ≦ b ≦ 0.
80 0.05≤c≤0.20, preferably 0.08≤c≤0.
15 where a + b + c = 1 second layer 6b Tbd Dye Fef Cog 0.05 ≦ d ≦ 0.20, preferably 0.08 ≦ d ≦ 0.
12 0.05 <e ≦ 0.20, preferably 0.08 <e ≦ 0.
12 0.50 ≦ f ≦ 0.80, preferably 0.60 ≦ f ≦ 0.
75 0.05≤g≤0.20, preferably 0.08≤g≤0.
15 However, the reason why the range of each atomic composition is limited to d + e + f + g = 1 is as follows. a
Is in the above range, the transition metal rich composition,
It is desirable in that the direction of magnetization and the direction of moment of the transition metal are aligned. When b is in the above range, the coercive force is 1 to 2 kOe, which is desirable in that perpendicular magnetic anisotropy can be obtained. Further, if c is within the above range, it is desirable in that the Curie point temperature is in a good range for reading characteristics.

Next, if d is within the above range, it is desirable in that a transition metal-rich composition is obtained by combining with Dy. When e is within the above range, it is desirable in that a transition metal-rich composition is obtained in combination with Tb. If f is in the above range, the coercive force is 8 to 1
It is desirable in that it can be set to 7 kOe. Furthermore, if g is within the above range, it is desirable in that the Curie point temperature becomes an appropriate value for recording.

The thickness of the first layer 6a is 50 to 200.
Å, preferably 100 to 150 Å, and a thickness in this range is desirable in that the read performance is improved and the coupling is stable. The thickness of the second layer 6b is 1
The thickness is preferably 50 to 300 Å, preferably 200 to 250 Å, and a thickness in this range is desirable in that a sufficient coercive force for recording can be obtained and a stable recording bit can be obtained.

[0016]

EXAMPLES Next, examples will be described. (Example 1) As a thin film 4 on a substrate 1 made of a polycarbonate resin, a dielectric layer 5 made of sialon having a thickness of 600Å, various recording layers 6 (or a recording layer of a comparative example) as shown in Table 1, and a thickness. Various magneto-optical disks (Samples No. 1 to No. 12) were prepared by forming a dielectric layer 7 made of sialon having a thickness of 200 Å and a reflective layer 8 made of titanium-containing aluminum having a thickness of 1000 Å. In each case, the thickness of the first layer 6a was 100Å and the thickness of the second layer 6b was 200Å.

[0017]

[Table 1]

When the coercive force and jitter of the recording layer of each magneto-optical disk were measured, the results shown in Table 2 were obtained. These measurements were performed at a rotation speed of 3000 rpm,
The recording was performed at a recording portion with a radius of 24.1 mm under the conditions of a recording power of 10 mW, a reproducing power of 1 mW, a recording frequency of 5.84 MHz, and a recording pulse width of 20 nanoseconds.

[0019]

[Table 2]

As is clear from the results of both tables, the sample No. 1 to No. In No. 3, the coercive force Hc of the recording layer 6 was 9 KOe or more, and the excellent characteristics that the jitter value was 5.0% or less were obtained. In addition, the sample No. 4 and N
o. In No. 5, although the composition of the recording layer 6 was appropriate, the coercive force did not reach a satisfactory value because the strength of exchange coupling was not uniform, and the jitter did not show a good value. .

On the other hand, the sample No. 6-No. Thirteen
According to the above, the coercive force of the recording layer 6 is out of the range of 7 to 16 kOe, and the jitter is in the practical range of 7.5.
% Or less (5.0% or less as a preferable range). By the way, if the coercive force is less than 7 kOe, the bit length is likely to be non-uniform and the jitter is deteriorated. If the coercive force is more than 16 kOe, some recorded bits cannot be written and the jitter is deteriorated. To do.

[0022]

As described above, according to the present invention, the recording layer in which the first layer made of the amorphous GdFeCo alloy and the second layer made of the amorphous TbDyFeCo alloy are sequentially provided, and further the first layer and the second layer are provided. Since both layers are rich in transition metal and the coercive force of the recording layer is set to 7 to 16 kOe, a high-performance magneto-optical disk with improved jitter characteristics can be provided.

Further, the magneto-optical disk of the present invention is suitable for pit edge recording because the jitter can be achieved to a very small value of 7.5% or less.

[Brief description of drawings]

FIG. 1 is a plan view of a magneto-optical disk M according to the present invention.

FIG. 2 is a sectional view of a magneto-optical disk M of the present invention.

FIG. 3 is a cross-sectional view showing a layer structure of a thin film according to the present invention.

[Explanation of symbols]

 M Magneto-optical disk 1 Substrate 4 Thin film 5 and 7 Dielectric layer 6 Recording layer 6a First layer 6b Second layer 8 Reflective layer 9 Protective resin layer

Claims (1)

[Claims] 1. A first dielectric layer on a transparent disk substrate,
A recording layer in which a first layer made of an amorphous GdFeCo alloy and a second layer made of an amorphous TbDyFeCo alloy are sequentially provided, a second dielectric layer, and a reflective layer are sequentially laminated, and the first layer and the second layer are formed. Both of the layers are rich in transition metal, and the coercive force of the recording layer is 7 to 16
A magneto-optical disk characterized by having kOe.