JPH0721602A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To enable the use of the next-generation laser light as well as the existing laser light by successively laminating a protective layer, a memory layer, a recording layer and a protective layer on a glass substrate and forming a GdTbFeCo film as the memory layer. CONSTITUTION:A protective layer 13, a memory layer 15A, a recording layer 17 and a protective layer 19 are successively laminated on a glass substrate 12 by forming layers 13, 19 with an SiNx film 14 and 20 respectively, a layer 15A with a Gd5.8Tb17.2Fe69.3 theta Co7.7 film 31, a layer 17 with a Tb2Dy24Fe44Co30 film 18. The thickness of layer 13, 19 is 85 nm, layer 15A is 30nm, layer 17 is 80nm, and to obtain a magneto-optical disk 30. The memory layer 15A acts so as to keep a large angle of Kerr rotation even when the wavelength of laser light 11 is shortened from 780nm to 680nm and such satisfactory performance as 49.8dB C/N of a reproduced signal after overwriting is ensured with a device using laser light of wavelength used now or the next-generation laser light of short wavelength.

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 that can be overwritten only by modulating laser light.

Magneto-optical drive devices currently on the market have a structure in which a laser diode (hereinafter referred to as LD) having a wavelength of 780 nm or 830 nm is incorporated.

On the other hand, in order to increase the recording density, an LD having a shorter wavelength is being developed, and a next-generation short wavelength LD having a wavelength of 680 nm is about to be put into practical use.

When this short wavelength LD is put to practical use, a magneto-optical drive device equipped with this short wavelength LD is commercialized.

Therefore, as a magneto-optical disk, not only in the present magneto-optical disk apparatus but also in the next-generation magneto-optical disk apparatus, overwrite by only modulation of laser light should be performed at a sufficiently high C / N. There is a need to realize a magneto-optical disk capable of achieving the above, that is, a magneto-optical disk whose signal quality does not deteriorate from the current long wavelength (780 nm) to short wavelength (680 nm) region.

[0006]

2. Description of the Related Art FIG. 12 shows an example of a conventional magneto-optical disk 10 which can be overwritten only by modulating laser light.

This magneto-optical disk 10 has a laser beam 11
The glass 2P substrate 12 is provided on the side where
On the upper surface of 2, the SiNx film 14 having a film thickness of 85 nm as the protective layer 13, the TbFeCo film 16 having a film thickness of 30 nm as the memory layer 15, and the film thickness of 80 nm as the recording layer 17 are sequentially formed.
The Tb ₂ Dy ₂₄ Fe ₄₄ Co ₃₀ film 18 and the SiNx film 20 having a film thickness of 85 nm as the protective layer 19 are laminated.

The recording layer 17 has its magnetization reversed in response to the information to be recorded by the laser beam modulated in the recording mode.

The memory layer 15 is coupled to the recording layer 17 by the exchange coupling force, and the magnetization of the recording layer 17 is transferred to record information.

[0010]

The above-mentioned magneto-optical disk 10 is used as two experimental magneto-optical disk devices No1 and No.
It was attached to No. 2 and experimented.

In both No. 1 and No. 2, the initializing magnetic field is 5
The kOe and the recording magnetic field are 300 Oe, and the rotation speed of the turntable is such that the linear velocity becomes 10 m / s at the radial position of 40 mm of the magneto-optical disk.

The No. 1 device has an LD with a wavelength of 780 nm.
Is installed.

The No. 2 device has an LD with a wavelength of 680 nm.
Is installed. [Experiment 1] The magneto-optical disk 10 was mounted on the No. 1 apparatus, and the signal of 4τ was overwritten to the signal of 1.5τ at a position of a radius of 40 mm, and then reproduction was performed to measure the C / N. Subsequently, the signal of 1.5 τ was overwritten to the signal of 4 τ, and then the reproduction was performed to measure the C / N.

Both of them are overwritten, and the portion having the highest C / N among the portions that can be overwritten under the same power condition is set as the signal quality.

The C / N was 50.0 dB. [Experiment 2] The magneto-optical disk 10 was mounted on the No. 2 apparatus, overwriting was performed under the same conditions as in Experiment 1, and then reproduction was performed to measure the C / N.

C / N was as low as 46.3 dB.

In order to put the magneto-optical disk and the magneto-optical disk device into practical use, it is necessary that the C / N is 48 dB or more.

As can be seen from the above experiment, the current magnetic disk is used in the next-generation magneto-optical disk device as follows.
There is a problem that the signal quality is deteriorated and unsuitable.

Therefore, the present invention provides a magneto-optical recording medium in which the signal quality does not deteriorate from the currently used long wavelength to the short wavelength region used in the next generation by changing the composition of the memory layer. To aim.

[0020]

According to a first aspect of the present invention, at least a recording layer on which a magnetization is reversed by a laser beam modulated in a recording mode and the recording layer are coupled on a substrate by a magnetic exchange coupling force. In the magneto-optical recording medium having a memory layer to which the magnetization of the recording layer is transferred, the memory layer is composed of a film having a composition of GdTbFeCo.

According to a second aspect of the present invention, at least the recording layer that is magnetization-inverted by the laser light modulated in the recording mode and the recording layer are coupled to each other by the magnetic exchange coupling force on the substrate, and the magnetization of the recording layer. In a magneto-optical recording medium having a memory layer to which is transferred, the memory layer is composed of a film having a composition of GdTbFe.

[0022]

The composition of the memory layer according to claim 1 is GdTb.
The film made of FeCo acts so as to keep a large Kerr rotation angle even when the wavelength of the laser light becomes a short wavelength.

The composition constituting the memory layer of claim 2 is Gd
The film made of TbFe acts so as to maintain a large Kerr rotation angle even when the wavelength of the laser light becomes a short wavelength.

[0024]

【Example】

[First Embodiment] (See FIG. 1) The magneto-optical disk 30 of FIG. 1 has a two-layer film structure except for the protective layer, and is different from the magneto-optical disk 10 of FIG.
Only the memory layer.

The memory layer 15A has a film thickness of 30 nm,
The film 31 is composed of Gd _5.8 Tb _17.2 Fe _69.3 Co _7.7 .

This magneto-optical disk 30 was mounted on the above-mentioned experimental devices No1 and No2, overwritten under the same conditions as described above, and then reproduced to measure C / N.
The results are as follows.

The C / N of the reproduced signal was 49.8 dB when it was mounted on the experimental apparatus No. 1 equipped with the 780 nm LD and overwriting was performed under the same conditions as described above, and then reproduced.

The C / N of the reproduced signal was 49.8 dB when it was mounted on the experimental apparatus No. 2 equipped with a 680 nm LD, overwritten under the same conditions as above, and then reproduced. 49.8 dB is not lower than the above 49.8 dB, and is sufficiently higher than the practical limit of 48 dB.

From this, the following can be understood.

The magneto-optical disk 30 can be applied to existing devices.

The magneto-optical disk 30 can be sufficiently applied to next-generation devices.

Here, Gd _5.8 Tb _17.2 Fe _69.3 Co
The film of _7.7 was irradiated with laser light of different wavelengths, and the Kerr rotation angle (θk) of the laser light at this time was measured.
The result shown by line I was obtained.

Line II is for a TbFeCo film.

From the figure, in the case of the TbFeCo film, when the wavelength of the laser light becomes shorter, the Kerr rotation angle θk decreases considerably, whereas in the case of Gd _5.8 Tb _17.2 Fe.
_In the case of the _69.3 Co _7.7 film, the Kerr rotation angle θk does not decrease so much even if the wavelength of the laser light becomes shorter.
That is, the Gd _5.8 Tb _17.2 Fe _69.3 Co _7.7 film is TbFe
It can be seen that the magneto-optical effect has less wavelength dependence than the Co film.

The signal quality of the above magneto-optical disk 30 is good even under a laser beam of 680 nm because Gd _5.8 Tb _17.2
It is considered that the Fe _69.3 Co _7.7 film has a Kerr rotation angle θk of about 1 deg and is still large even if the wavelength of the laser beam is shortened. [Second Embodiment] (See FIG. 3) The magneto-optical disk 40 has a two-layer structure except for the protective layer, and differs from FIG. 1 only in the memory layer.

The memory layer 15B has a film thickness of 30 nm,
The film 41 is composed of Gd _4.6 Tb _18.4 Fe _7.7 .

The magneto-optical disk 40 was attached to the above-mentioned experimental devices No1 and No2, overwriting was performed under the same conditions as described above, and then reproduction was performed to measure the C / N, and the following results were obtained.

The magneto-optical disk 40 had a high C / N of 49.7 dB for a 780 nm LD and a C / N of 49.5 dB for a 680 nm LD.

49.5 dB is substantially lower than the above 49.7 dB and is sufficiently higher than 48 dB.

Therefore, the magneto-optical disk 40 can be used not only in the existing magneto-optical disk apparatus but also in the next-generation magneto-optical disk apparatus.

This is a film 41 of Gd _4.6 Tb _18.4 Fe ₇₇ .
Fig. 2 shows the changes in the Kerr rotation angle with respect to the laser light wavelength.
As shown by the middle line III, it is considered that the Kerr rotation angle θk is still high at about 1 deg even if the wavelength of the laser beam is shortened. [Third Embodiment] (See FIG. 4) The magneto-optical disk 50 includes a protective layer 13, a memory layer 15A,
The control layer 51, the recording layer 17, and the protective layer 19 are laminated and have a three-layer structure except for the protective layer. What is different from FIG. 1 is that the film thickness between the memory layer 15A and the recording layer 17 is 10 nm. Yes,
Control layer 51 comprising a film 52 having a composition of Gd ₃₄ Fe ₄₈ Co ₂₀
It is a structure having.

The magneto-optical disk 50 had a high C / N of 50.2 dB for a 780 nm LD and a high C / N of 50.1 dB for a 680 nm LD. [Fourth Embodiment] (see FIG. 5) The magneto-optical disk 60 has a memory layer 15B and has a three-layer structure except for the protective layer. The difference from FIG. 3 is that the memory layer 15B and the recording layer 17 are different from each other. The control layer 51 is provided between them.

The magneto-optical disk 60 had a high C / N of 50.0 dB for a 780 nm LD and a high C / N of 49.8 dB for a 680 nm LD. [Fifth Embodiment] (See FIG. 6) The magneto-optical disk 70 includes a memory layer 15A including a protective layer 17 and a film 31, a recording layer 17, and Tb ₁₈ Fe on a substrate 12.
_{It is made of} a film 72 of ₈₀ Co ₂ .

Control layer 71, Tb ₂₇ Fe ₂₅ Co ₄₈ film 73
It has a four-layer structure except for the protective layer formed by the initializing layer 74 and the protective layer 19 and is a structure that can be initialized without using an external magnet.

The magneto-optical disk 70 had a high C / N of 50.2 dB for a 780 nm LD and a high C / N of 50.2 dB for a 680 nm LD. [Sixth Embodiment] (See FIG. 7) A magneto-optical disk 80 includes a memory layer 15B made of a film 41 in place of the memory layer 15A of the magnetic disk 70 shown in FIG.
It is a structure having.

This magneto-optical disk 80 is a 780 nm LD
, The C / N was as high as 50.0 dB, and the C / N was as high as 49.8 dB for the 680 nm LD. [Seventh Embodiment] (See FIG. 8) A magneto-optical disk 90 includes a memory layer 15A made of a film 31.
And a magneto-optical disk 80 having the structure shown in FIG.
A control layer 51 is added between the memory layer 15A and the recording layer 17 and has a five-layer structure except for the protective layer.

This magneto-optical disk 90 is a 780 nm LD
, The C / N was as high as 50.2 dB, and the C / N was as high as 50.2 dB for the 680 nm LD. [Eighth Embodiment] (See FIG. 9) The magneto-optical disk 100 is a magneto-optical disk 90 shown in FIG.
Of the memory layer 1 made of the film 41 in place of the memory layer 15A of FIG.
This is a configuration having 5B.

This magneto-optical disk 100 has a 780 nmL
C / N was as high as 50.1 dB for D, and C / N was as high as 50.1 dB for 680 nm LD. [Ninth Embodiment] (See FIG. 10) The magneto-optical disk 110 has a structure in which a heat dissipation layer 111 is added to the magneto-optical disk 50 shown in FIG.

On the substrate 12, a memory layer 15A composed of a protective layer 13 and a film 31, a control layer 51, a recording layer 17, SiNx.
A dielectric layer 113 made of a film 112 and a heat dissipation layer 111 made of an Al film 114 are laminated.

This magneto-optical disk 110 is 780 nmL
C / N was as high as 51.2 dB for D, and C / N was as high as 51.2 dB for 680 nm LD. [Tenth Embodiment] The magneto-optical disk 120 includes a film 4 instead of the memory layer 15A of the magneto-optical disk 110 in FIG.
This is a configuration having a memory layer 15B of 1.

This magneto-optical disk 120 is 780 nmL
C / N was as high as 50.8 dB for D, and C / N was as high as 50.8 dB for 680 nm LD.

[0052]

As described above, according to the first aspect of the present invention, it goes without saying that when the present invention is mounted on a magneto-optical disk device equipped with an LD of 780 nm and used for overwriting,
Sufficient signal quality can be obtained even when it is mounted on a magneto-optical disk device equipped with a 680 nm LD, which is the next-generation magneto-optical disk device, and used by overwriting.

According to the invention of claim 2, the present 780 nm
Of the next generation magneto-optical disk device mounted on the magneto-optical disk device equipped with the LD, and of course, overwriting by mounting it on the magneto-optical disk device equipped with the 680 nm LD of the next generation. Even when used, sufficient signal quality can be obtained.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship between a wavelength of laser light of a film and a Kerr rotation angle.

FIG. 3 is a diagram showing a structure of a magneto-optical disk according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a structure of a magneto-optical disk according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a structure of a magneto-optical disk according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a structure of a magneto-optical disk according to a fifth embodiment of the present invention.

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

FIG. 8 is a diagram showing a structure of a magneto-optical disk according to a seventh embodiment of the present invention.

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

FIG. 10 is a diagram showing the structure of a magneto-optical disk according to a ninth embodiment of the present invention.

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

FIG. 12 is a diagram showing a configuration of an example of a conventional magneto-optical disk.

[Explanation of symbols]

12 glass substrate 13, 19 protective layer 14, 20 SiNx film 15A, 15B memory layer 17 recording layer 18 Tb ₂ Dy ₂₄ Fe ₄₄ Co ₃₀ film 30, 40, 50, 60, 70, 80, 90, 100,
110,120 magneto-optical disk 31 Gd _5.8 Tb _17.2 Fe _69.3 Co _7.7 film 41 Gd _4.6 Tb ₁₈ Fe ₇₇ film 51,71 control layer 52 G ₃₂ Fe ₄₈ Co ₂₀ film 72 Tb ₁₈ Fe ₈₀ Co ₂ film 73 Tb ₂₇ Fe ₂₅ Co ₄₈ film 74 Initialization layer 111 Heat dissipation layer 112 SiNx film 113 Dielectric layer 114 Al film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomonori Ikeya 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (2)

[Claims] 1. A recording layer on which at least a magnetization is inverted by a laser beam modulated in a recording mode on a substrate, and a memory which is coupled to the recording layer by a magnetic exchange coupling force and in which the magnetization of the recording layer is transferred. A magneto-optical recording medium having a layer, wherein the memory layer (15A) is composed of a film (31) having a composition of GdTbFeCo. 2. A recording layer on which at least a magnetization is inverted by a laser beam modulated in a recording mode on the substrate, and a memory which is coupled to the recording layer by a magnetic exchange coupling force and in which the magnetization of the recording layer is transferred. A magneto-optical recording medium having a layer, wherein the memory layer (15B) is composed of a film (41) having a composition of GdTbFe.