JPH076419A - Magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a magneto-optical disk, and it is an object of the present invention to improve the C / N ratio in a magneto-optical disk having an overwritable structure. [Structure] A memory layer 21 and a recording layer 14 are formed on a substrate 11.
Have. In the memory layer 21, the T _b concentration changes in the layer thickness direction. Portion of the substrate 11 close of the memory layer 21 has a composition of _{T b19 (F e90 C 010)} 81, mosquito - large rotation angle. The portion of the memory layer 21 near the recording layer 14 has a composition of T _b22 (F _e90 C ₀₁₀ ) ₇₈ , and the exchange coupling force between the recording layer 14 and the memory layer 21 is large.

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, it relates to a magneto-optical recording medium applied to optical modulation overwrite.

In an information processing device using a magneto-optical disk device, it is desired to increase the data transfer speed.

For this reason, the magneto-optical disk device has moved from a type in which the first-generation overwrite is not possible, which has a single magnetic layer, to a type which has a plurality of magnetic layers and is capable of optical modulation overwrite. It's starting.

In this case, it is necessary to obtain the same high signal quality as the first generation (a high C / N ratio of about 55 dB).

[0005]

2. Description of the Related Art FIG. 13 shows the structure of a conventional magneto-optical disk 10 capable of optical modulation overwrite.

[0006] magneto-optical disc 10, on the substrate 11 of the groove with, T _b -SiO ₂ film base protective layer 12, the memory layer _{13, T b4 D y26 F e35} C o35 film of the recording layer 14, T
_This is a configuration having the upper protective layer 15 of the _b- SiO ₂ film.

The memory layer 13 and the recording layer 14 are exchange-coupled by the exchange coupling force.

The memory layer 13 is made of T _b20 (F _e90 C _o10 ).
_It consists of ₈₀ films.

The film forming the memory layer 13 has a uniform composition in the film thickness direction.

As shown by the line I in FIG. 14, the concentration of T _b is constant in the film thickness direction and is 19.5 at%.

[0011] The a T _b concentration of 19.5At%, in the first-generation magneto-optical disk, and T _b concentration of the magnetic layer, and the C / N ratio in FIG. 15, a relationship indicated by the line II Is based on that.

[0012]

The magneto-optical disk 10 described above has a C / N ratio of about 50 dB when it is subjected to optical modulation overwrite and then reproduced, and is obtained by the first-generation magneto-optical disk. It was considerably lower than the C / N ratio of about 55 dB, which was a problem in practical use.

Further, the present inventors, by forming a memory layer and increased T _b concentration, also though experiments were conducted by forming a memory layer with reduced T _b concentration, C / N ratio more than 50dB Did not improve.

Therefore, an object of the present invention is to provide a magneto-optical recording medium with an improved C / N ratio.

[0015]

According to a first aspect of the present invention, there is provided a magneto-optical recording medium having, on a substrate, a memory layer to which information written in a recording layer is transferred and a recording layer to which information is written. The concentration of a predetermined component of the composition changes in the layer thickness direction, and the substrate side is
The composition has the maximum rotation angle, and the recording layer side has the composition having the best exchange coupling force with the recording layer.

[0016]

According to the structure of the memory layer of the first aspect of the present invention, the portion of the memory layer on the substrate side has a composition having a maximum curve rotation angle, which serves to facilitate the generation of the carrier (C).

The configuration in which the portion of the memory layer on the recording layer side has the best exchange coupling force with the recording layer has a noise (N) when the information written in the recording layer is transferred to the memory layer. Acts to reduce.

[0018]

【Example】

[First Embodiment] (See FIGS. 1 to 6) FIG. 1 shows a magneto-optical disk 20 according to a first embodiment of the present invention.

The magneto-optical disk 20, except for the memory layer,
The structure is the same as that of the magneto-optical disk 10 shown in FIG.
The same reference numerals are given to the portions corresponding to the constituent portions shown in FIG. 13 and the description thereof will be omitted.

The memory layer 21 is made of T _bx (F _e90 C _o10 ).
The film is made of _100-x and has a composition distribution in which the concentration of T _b continuously changes from the substrate 11 side to the recording layer 14 side, as indicated by a line II in FIG.

The surface 21 of the memory layer 21 on the substrate 11 side
The composition of a is T_b19(F_e90C_o10) ₈₁Is.

Of the memory layer 21, the surface 2 on the recording layer 14 side
The composition of 1b is T_b22(F_e90C_o10) ₇₈Is.

In this magneto-optical disk 10, the C / N ratio when information was recorded by overwriting and reproduced was as high as 54 dB. The C / N ratio of 54 dB was substantially the same as the C / N ratio of the first-generation magneto-optical disk.

Next, the above-mentioned magneto-optical disk 20 has a high C
The reason for having the / N ratio will be described.

The overwrite on the magneto-optical disk 20 is
This is performed by recording information on the recording layer 14 and transferring the information recorded on the recording layer 14 to the memory layer 21. After that, the recording layer 14 is initialized.

Overwritten magneto-optical disk 20
Is reproduced by irradiating the memory layer 21 with the laser light 22 from the side of the substrate 11, rotating the polarization plane of the laser light 22 by a curve, and detecting a change in the curve rotation angle.

The above-mentioned magneto-optical disk 20 has a high C / N ratio for the following two reasons.

First, noise is small when information is transferred from the recording layer 14 to the memory layer 13.

Secondly, the car rotation angle is large.

Noise during transfer is small.

The inventors have, in the composition of _{T bx (F e90 C o10)} 100-x, with varying concentrations of T _b variously exchange coupling between the film and T _b D _y F _e C _o film at that time I investigated the power.

[0032] As a result, when the concentration of T _b is within the range of 22% ± 1% it was found that the exchange coupling force is strong.

The strong exchange coupling force means that there is little error, that is, noise, which occurs when the information recorded in the recording layer is transferred to the memory layer.

Whether or not the transferability of information is good or bad is determined by the composition of the recording layer of the memory layer.

[0035] In this embodiment, T _b the concentration of the surface 21b side of the recording layer 14 side of the memory layer 21 is 22%.

Therefore, the information written in the recording layer 14 is transferred to the memory layer 21 with almost no noise.

As a result, the level of N is lowered.

The car rotation angle is large.

T _bx (F _e90 C _o10 ) _100-x T _b concentration X
It is known that the curve rotation angle θ _k and the curve rotation angle θ _k have a relationship shown by a line I in FIG.

When the concentration of T _b is about 19 at%, the car
The rotation angle θ _k is approximately maximum.

It is the surface of the memory layer on the substrate side that determines the curve rotation angle of the polarization plane of the laser beam during reproduction.

In this embodiment, the substrate 1 of the memory layer 21 is used.
The concentration of T _b on the first side 21a side is 18%.

For this reason, the angle of rotation of the polarization plane of the laser beam during reproduction is large, and carriers are emitted.

As a result, the level of C is increased. Next, a method of forming the memory layer 21 of the magneto-optical disk 20 will be described. First, the data of the experiment conducted by the inventor will be described.

The inventor has found that T _b is placed in the chamber of the sputtering apparatus.
Place side by side target the target and F _e90 C _o10, defined constant sputtering power of F _e90 C _o10 to 1.5 kw, by changing the sputtering power of T _b as appropriate, T _b F _e C _o
Film is formed, the concentration of T _b of the formed film experiment was conducted to measure.

[0046] As a result, sputtering power of T _b and T _b F _e
It was found that there is a relationship shown by a line IV in FIG. 4 with the T _b concentration of the _Co film.

The formation of the memory layer 21 utilizes the above results.

The memory layer 21 and the recording layer 14 were formed by using the sputtering apparatus 30 shown in FIG.

The apparatus 30 has a chamber 31 in which a substrate 11 is held on the lower surface thereof and rotates about its axis while revolving, and three magnetron sputtering cathodes 3 are provided.
3 _-1 , 33 _-2 , 33 _-3 , three shutters 34 _-1 , 3
_4-2 , 34 _-3 , and three D's are provided outside the chamber 31.
This is a configuration having C power supplies 35 _-1 , 35 _-2 , 35 _-3 .

Target 3 of T _b on cathode 33 _-1
6, target 3 of _{Fe 90} C _o10 on cathode 33 _-2
7. A target 38 of T _b4 D _y26 F _{e35 Co} 35 is placed on the cathode 33 _-3 .

[0051] The A _r gas pressure in the chamber 31 0.5Pa
And keep it constant.

The shutters 34 _-1 and 34 _-2 are opened, and the power source 3
_5-2 of the output was controlled to a constant 1.5 kw, the voltage of the power source 35 _-1, in FIG. 6, about from about 0.2kw as indicated by line V 0.
Change linearly to 3 kW. This gives the line
The memory layer 21 having the composition distribution indicated by II is formed.
Then, the shutters 34 _-1 , 34 _-2 are closed and the shutter 34
_-3 is opened, and a sputtering power of 0.5 kw is applied by the power source 35 _-3 .

As a result, the recording layer 14 is formed on the memory layer 21.

Next, another embodiment of the present invention will be described.

[Second Embodiment] (See FIGS. 7 and 8) The magneto-optical disk 40 has the structure shown in FIG. 7 and has a memory layer 41.

The concentration distribution of T _b in the thickness direction of the memory layer 41 is as shown by the line VI in FIG. The _Tb concentration changes near the center of the film thickness. About half of 41a of the substrate 11 close of the memory layer 41, T _b concentration 19at
%, Which is constant and is about half of the recording layer 14 side 41b
Has a constant T _b concentration of 22 at%.

The C / N ratio of this magneto-optical disk 40 is 5
It was 4 dB.

The memory layer 41 is formed by controlling the T _b sputtering power as shown by the line VII in FIG.

[Third Embodiment] (See FIGS. 9 and 10) The magneto-optical disk 50 has a memory layer 51.

The concentration distribution of T _{b in} the memory layer 51 is shown in FIG.
Middle, as shown by line VIII. The T _b concentration changes in the portion of the film thickness closer to the substrate 11 side than the center.

About 1 of the memory layer 51 near the substrate 11
The portion 51a having a thickness of / 4 has a constant T _b concentration of 19 at%, and the portion 51a having a thickness of about 3/4 near the recording layer 14 is provided.
As for b, the T _b concentration is constant at 22 at%.

The C / N ratio of this magneto-optical disk 50 is 5
It was 2 dB.

[Fourth Embodiment] (see FIGS. 11 and 12) The magneto-optical disk 60 has a memory layer 61.

The concentration distribution of T _{b in} the memory layer 61 is shown in FIG.
Middle, as shown by line IX. The T _b concentration changes in the portion of the film thickness closer to the recording layer 14 side than the center.

About 3 of the memory layers 61 near the substrate 11
/ 4 of the thickness of the portion 61a is, T _b concentration is constant at 19 at%, the portion of about 1/4 of the thickness of the recording layer 14 closer 61
As for b, the T _b concentration is constant at 22 at%.

The C / N ratio of this magneto-optical disk 60 is 5
It was 2 dB.

The memory layers 51 and 61 can be formed by changing the T _b sputtering power (output power of the DC power source 35 _-1 ) stepwise during sputtering.

[0068]

As described above, according to the present invention,
It is possible to realize an overwritable magneto-optical recording medium which has a higher C / N ratio than the conventional one and can obtain the C / N ratio to the extent obtained by the first-generation magneto-optical disk.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a magneto-optical disk according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a T _b concentration distribution in a film thickness direction of a memory layer of the magneto-optical disc of FIG.

FIG. 3 is a diagram showing a relationship between a T _b concentration X of T _bx (F _e90 C _o10 ) _{100-x and} a _car rotation angle θ _k .

FIG. 4 T _b sputter power and T _{b Fe} C _{o formed.}
It is a figure which shows the relationship with the _Tb density _| concentration of a layer.

5 is a view showing a sputtering apparatus used for manufacturing the magneto-optical disk shown in FIG.

FIG. 6 is a diagram showing a mode in which T _b sputtering power is applied when forming a memory layer.

FIG. 7 is a diagram showing a structure of a magneto-optical disk according to a second embodiment of the present invention.

8 is a diagram showing the T _b concentration distribution in the film thickness direction of the memory layer of the magneto-optical disk of FIG.

FIG. 9 is a diagram showing the structure of a magneto-optical disk according to a third embodiment of the present invention.

10 is a diagram showing a T _b concentration distribution in the film thickness direction of the memory layer of the magneto-optical disk of FIG.

FIG. 11 is a diagram showing the structure of a magneto-optical disk according to a fourth embodiment of the present invention.

12 is a diagram showing the T _b concentration distribution in the film thickness direction of the memory layer of the magneto-optical disk of FIG.

FIG. 13 is a diagram showing a structure of an example of a conventional magneto-optical disk.

14 is a diagram showing a T _b concentration distribution in the film thickness direction of the memory layer of the magneto-optical disk of FIG.

FIG. 15 is a diagram illustrating the basis for setting the T _b concentration of the memory layer of the magneto-optical disk of FIG. 13 to 19.5 at%.

[Explanation of symbols]

 11 Substrate 12 Underlayer Protection Layer 14 Recording Layer 15 Upper Ground Protection Layer 20, 40, 50, 60 Magneto-Optical Disk 21, 41, 51, 61 Memory Layer

Claims (2)

[Claims] 1. A magneto-optical recording medium having, on a substrate, a memory layer to which information written in a recording layer is transferred and a recording layer to which information is written, wherein the memory layer has a composition in the thickness direction of the layer. The concentration of a predetermined component is changed, the substrate side has a composition with a maximum curve rotation angle, and the recording layer side has a composition with the best exchange coupling force with the recording layer. A magneto-optical recording medium having a structure. 2. The memory layer according to claim 1, wherein the substrate side has T
_A magneto-optical recording medium having a composition of _b19 (F _e90 C _o10 ) ₈₁ and having a composition of T _b22 (F _e90 C _o10 ) ₇₈ on the recording layer side.