JPH0636372A - Magneto-optical recording medium and its production - Google Patents

Abstract

(57) [Summary] [Purpose] Having a large perpendicular magnetic anisotropy (Ku) and coercive force (Hc) even if the amount of Tb is small (or not),
Provided is an inexpensive magneto-optical recording medium having high recording density and high reliability. [Structure] After forming a recording layer made of a rare earth metal-iron group transition metal amorphous alloy, (1) pulsing light from a high-power laser or a lamp such as xenon, mercury, or halogen to the entire medium for short-time irradiation Method, (2) irradiating a high-power laser such as argon or CO ₂ while rotating the medium, (3) higher power than when the user actually records or erases using a magneto-optical disk drive, etc. By a method such as a method in which the processing is performed at a low rotation speed, the processing is instantaneously performed to make the temperature higher than that during magneto-optical recording.

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 its manufacturing method.

[0002]

2. Description of the Related Art The magnetic film of magneto-optical disks currently on the market is mainly composed of TbFeCo. However, since Tb is expensive, it is necessary to use Tb in order to reduce the cost. The smaller the amount, the better. However, it is generally said that the larger the perpendicular magnetic anisotropy (Ku) and the coercive force (Hc) of a magnetic film for a magneto-optical disk, the better, and when Tb is decreased, the perpendicular magnetic anisotropy (Ku) and the coercive force (Ku) are reduced. Hc) decreases, and it becomes impossible to obtain a material that can be used practically.

On the other hand, the use of a short wavelength laser is required to increase the density of magneto-optical recording, but as the wavelength of the TbFeCo magnetic film becomes shorter, the magneto-optical effect (θk) decreases, and the read performance is improved. Is reduced. On the other hand, a rare-earth metal (RE) -iron group transition metal (TM) amorphous alloy containing Nd (hereinafter sometimes referred to as RE-TM amorphous alloy) attracts great attention due to its magneto-optical effect (θk) in a short wavelength region. (The 11th Japan Society for Applied Magnetics, Academic Lecture Summary 3aD-2, p.262,1987.11, 3
aD-4, p. 264, 1987.11., 3aD-
3, p. 263, 1987.11., 3aD-6, p.
266, 1987.11., Proceedings of the 12th Annual Meeting of the Applied Magnetics Society of Japan, 1aB-2, p. 112, 1988, ibid. 1
aB-4, p. 114, 1988). Since the Nd-iron group transition metal (TM) alloy film is an in-plane magnetized film, it cannot be used as a magnetic film of a magneto-optical disk, but when a heavy rare earth metal, especially Tb is added thereto, the perpendicular magnetic anisotropy (Ku) is increased. ) And coercive force (Hc) increase to reach a level at which it can be used as a magnetic film of a magneto-optical disk, but the Nd ratio must be reduced accordingly, and at the same time the magneto-optical effect (θk) also decreases, which is not preferable.

Further, an Nd-based RE-TM alloy film and TbFe having large perpendicular magnetic anisotropy (Ku) and coercive force (Hc) are used.
A method for solving the above problems by using a recording film of a multilayer film type in which a Co alloy film is exchange-coupled has been proposed (12th Annual Meeting of the Japan Society for Applied Magnetics, 1a).
B-3, p. 113, 1988, Proc. Of the 13th Japan Society for Applied Magnetics, 24aC-1, p. 325,198
8), the layer structure becomes complicated, the film formation becomes difficult, the film thickness of the entire magnetic film increases, and the recording sensitivity deteriorates.
Further, the Nd-based RE-TM alloy film originally has a small perpendicular magnetic anisotropy, and when the film thickness increases, the perpendicular component of the surface magnetization decreases, so that the film thickness cannot be increased so much that the magneto-optical effect (θk) is reduced. There is a problem that there is a limit to the increase.

The present invention has been made in view of the circumstances of the prior art as described above, and has a large perpendicular magnetic anisotropy (Ku) and a coercive force (H) even if the amount of Tb is small (or not).
An object of the present invention is to provide a magneto-optical recording medium having c), which is inexpensive, has a high recording density and high reliability, and a manufacturing method thereof.
In addition, the present invention provides an Nd-based RE-TM alloy film containing Nd.
Provided are a magneto-optical recording medium having a large perpendicular magnetic anisotropy (Ku) and a coercive force (Hc) even if it contains a large amount, and capable of coping with high density using a short wavelength laser, and a manufacturing method thereof. The purpose is to

[0006]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in order to solve the above problems, the RE-TM is formed on a substrate.
After forming a magnetic layer composed of an amorphous alloy,
By subjecting the magnetic layer to a temperature higher than that at the time of magneto-optical recording, the perpendicular magnetic anisotropy (Ku) and the coercive force (Hc) can be obtained even if the amount of Tb is reduced (or not used). ) Is a sufficiently large value, and also in the magnetic layer composed of the Nd-based RE-TM alloy, a sufficiently large perpendicular magnetic anisotropy (K
u) and coercive force (Hc) can be obtained, and it has been found that the above object can be achieved, and the present invention has been completed.

That is, according to the present invention, in a magneto-optical recording medium having a recording layer composed of an amorphous alloy film of a rare earth metal and an iron group transition metal, the recording layer is instantaneously magneto-optically formed. There is provided a magneto-optical recording medium characterized by being subjected to a treatment of making the temperature higher than that at the time of recording. Further, according to the present invention, there is provided a magneto-optical recording medium characterized in that a part or all of the rare earth metal is Nd. Further, according to the present invention, after forming a recording layer composed of an amorphous alloy film of a rare earth metal and an iron group transition metal on a substrate, by irradiating a high output light pulse on the entire film surface, There is provided a method of manufacturing a magneto-optical recording medium, which comprises performing a treatment for instantaneously raising the temperature of the recording layer to a temperature higher than that during magneto-optical recording. Further, according to the present invention, after a recording layer formed of an amorphous alloy film of a rare earth metal and an iron group transition metal is formed on a circular substrate, the laser actually used for magneto-optical recording while rotating the substrate. A method for manufacturing a magneto-optical recording medium, which comprises irradiating the recording layer with a laser beam having a power higher than that of light to momentarily raise the temperature of the recording layer to a temperature higher than that during magneto-optical recording. Provided.

The present invention will be described in detail below. An example of the structure of the magneto-optical recording medium of the present invention is shown in FIG. This magneto-optical recording medium comprises a substrate 1, a protective layer 2, a magnetic layer 3, a protective layer 4, a reflective layer 5 and a protective coat layer 6 which are sequentially laminated.
The magnetic layer 3 is made of an amorphous alloy film of a rare earth metal and an iron group transition metal, and the magnetic layer 3 is subjected to a treatment to make the temperature thereof instantaneously higher than that at the time of magneto-optical recording after the film formation.

In general, when magneto-optical recording is performed, the magnetic layer (recording layer) portion in the recording medium is raised to near the Curie temperature of the magnetic layer. At that time, the magnetization direction of the magnetic layer is reversed, but other chemical and structural changes do not occur. The recording layer 3 of the magneto-optical recording medium of the present invention is subjected to the treatment for instantaneously raising the temperature to a higher temperature than that during magneto-optical recording as described above, but an amorphous alloy film of a rare earth metal and an iron group transition metal is generally used. Since the crystallization temperature exists at a temperature about 100 to 300 ° C. higher than the Curie temperature, it is necessary to heat and cool within a short time so as not to crystallize. Although the actual heating temperature and the heating time cannot be measured, the heating temperature is preferably higher than the Curie temperature (the temperature at which a signal is recorded or erased) by 50 ° C. or more, and the heating time is about 10 μsec or less. Is preferred.

After the recording layer 3 is formed, the perpendicular magnetic anisotropy (Ku) is increased by subjecting the recording layer 3 to a sufficient temperature rise for a short time within a range that does not cause crystallization. It is conjectured that this is due to some structural change or morphological change.
The cause is unknown. Therefore, comparing those having the same deviation from the compensation composition before and after this treatment, the coercive force (Hc) is increased after the treatment.

As the method for performing the above heat treatment, (1) a method in which light from a high-power laser or a lamp such as xenon, mercury, or halogen is pulsed to the entire medium and irradiated for a short time, (2) the medium is rotated. However, a method of irradiating a high power laser such as argon or CO ₂ , (3) a method of processing at a higher power or a lower rotation speed than when a user actually records or erases using a magneto-optical disk drive, However, the present invention is not limited to this.

In the case of the method (1), a high-power light source such that the magnetic layer has a sufficiently high Curie temperature or higher and a short-time irradiation that does not cause crystallization are necessary conditions. In the case of the method of (2), it is ideal to perform each recording track, but several tracks to several hundred tracks may be collectively processed by using a homogeneous beam having high output and no intensity distribution. When processing is performed for each track, a servo system similar to a general optical disk drive is required, but when performing processing collectively, a precise control system is not required. In the case of method (3), it is desirable to perform the same operation as the signal erasing operation at the highest speed possible, and with a higher power than when recording or erasing the signal. It is also possible to lower the rotation speed with.

In the above, the recording layer may be a single layer film or a multilayer film. RE can be Tb, Dy, Gd, etc., and TM can be Fe, Co, Ni, etc. Further, the layer configuration is not limited to the above configuration example,
Various modifications and changes are possible.

For the short wavelength LD, the recording layer is made of Nd.
In the case of using the RE-TM amorphous film containing
Despite containing Nd, a large perpendicular magnetic anisotropy (Ku) and a coercive force (Hc) were obtained, and it was found that it is possible to sufficiently cope with high density using a short wavelength laser. .

[0014]

EXAMPLES Examples of the present invention will be described below. Example 1 On a polycarbonate substrate 1 having a thickness of 1.2 mm, a protective layer 2 (100 nm thick) made of a SiN film, a magnetic layer 3 (30 nm thick) made of a DyFeCo film, a protective layer 4 (100 nm thick) made of a SiN film, Reflective layer 5 (50 made of Al film
nm thickness) and a protective coat layer 6 (5 μm thickness) were formed. After forming the magnetic layer 3, a linear velocity of 1 is obtained by the same method as in ordinary optical recording.
The film surface was entirely irradiated with 15 mW of DC laser light at 1 m / sec. The coercive force (H
When c) was measured, the values shown in Table 1 were obtained.

Example 2 A recording medium was obtained in the same manner as in Example 1 except that an NdTbFeCo film was formed as the magnetic layer 3. When the coercive force (Hc) of this medium was measured, the values shown in Table 1 were obtained.

Comparative Example 1 A medium in which the entire surface was not irradiated with laser light in Example 1 was prepared and its coercive force (Hc) was measured. The values shown in Table 1 were obtained.

Comparative Example 2 When a medium in which the entire surface of the laser beam was not irradiated in Example 2 was prepared and the coercive force (Hc) was measured, the values shown in Table 1 were obtained.

[0018]

[Table 1]

[0019]

According to the magneto-optical recording medium of the present invention, RE
The perpendicular magnetic anisotropy (Ku) was used because the recording layer formed of the TM amorphous alloy film was subjected to a treatment that was momentarily heated to a temperature higher than that during magneto-optical recording after the recording layer was formed. Also, since the coercive force (Hc) is increased, the recording stability is improved. Furthermore, even if Tb is replaced with Dy, Gd, etc., the same characteristics can be obtained, and the cost of the recording medium can be reduced while maintaining high density recording. Further, the RE-TM amorphous film containing Nd can be provided with a coercive force (Hc) that can be used as a magneto-optical recording medium, and a recording medium with good reproduction performance can be provided even when a short wavelength LD is used. Further, according to the manufacturing method of the present invention, the recording medium having the above advantages can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a magneto-optical recording medium having one configuration example of the present invention.

[Explanation of symbols]

 1 Substrate 2, 4 Protective Layer 3 Magnetic Layer 5 Reflective Layer 6 Protective Coating Layer

Claims (4)

[Claims] 1. A magneto-optical recording medium comprising a recording layer composed of an amorphous alloy film of a rare earth metal and an iron group transition metal, wherein the recording layer is instantaneously heated to a temperature higher than that during magneto-optical recording. A magneto-optical recording medium, which has been subjected to a treatment. 2. The magneto-optical recording medium according to claim 1, wherein a part or all of the rare earth metal is Nd. 3. After forming a recording layer composed of an amorphous alloy film of a rare earth metal and an iron group transition metal on a substrate, the recording layer is irradiated with a high-power optical pulse over the entire film surface. A method for manufacturing a magneto-optical recording medium, which comprises performing a treatment for making the temperature instantaneously higher than that during magneto-optical recording. 4. After forming a recording layer composed of an amorphous alloy film of a rare earth metal and an iron group transition metal on a circular substrate, the substrate is rotated and the laser beam used for actual magneto-optical recording A method of manufacturing a magneto-optical recording medium, which comprises irradiating the recording layer with a high-power laser beam so that the recording layer is momentarily heated to a temperature higher than that during magneto-optical recording.