JP3099489B2 - Magneto-optical recording medium - Google Patents

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, the present invention relates to a magneto-optical recording medium in which a Kerr rotation angle is hardly reduced even when recording and reproduction are performed by inputting a short-wavelength laser beam.

[0002]

2. Description of the Related Art Conventionally, a magneto-optical recording medium using an amorphous alloy thin film of a rare earth element such as terbium-iron-cobalt and a transition metal element as a recording layer has insufficient readout characteristics. As shown in FIG. 1, a terbium-silicon dioxide (Tb-Si
A first protective layer 2-1 of O ₂₎ was formed as an interference layer, thereby improving the reading characteristics by the magneto-optical effect on a large. Since the recording layer 3 of the amorphous alloy thin film of the rare earth element and the transition metal element is easily oxidized, the above-described Tb-SiO ₂
The recording layer 3 is formed as a second protective layer 2-2 by a film to protect the recording layer 3 from permeation of oxygen and moisture in the atmosphere.

The substrate 1 of such a magneto-optical recording medium is made of a transparent material such as a transparent glass or a transparent plastic substrate. Light is incident on the recording layer 3 to record and reproduce information.

As a substrate material, a durable aluminum substrate is used in place of a transparent glass substrate or a transparent plastic substrate which is easily broken. In this case, light is incident from the upper side of the substrate 1 to record information. , Is playing.

[0005]

SUMMARY OF THE INVENTION Terbium-iron-cobalt (Tb-Fe-Co), dysprosium-iron-cobalt (Dy-Fe-Co), gadolinium-iron-cobalt (Tb-Fe-Co) conventionally used for the recording layer. An amorphous alloy thin film of a rare earth element such as Gd-Fe-Co) and a transition metal element has a large Kerr rotation angle near a wavelength of 800 nm, and is therefore a sufficiently practical material as a recording layer of a magneto-optical recording medium. It is.

[0006] However, there is an increasing demand for recording and reproducing information at higher densities, and for this purpose, it has been attempted to record by using short-wavelength light as laser light used for recording and reproduction. However, when recording at such a short wavelength, the rare earth-transition metal amorphous alloy described above tends to have a small Kerr rotation angle on the short wavelength side, so that the C / N of the recording signal is low.
Has a small value, and high-precision recording and reproduction cannot be performed.

An object of the present invention is to provide a high-quality magneto-optical recording medium which eliminates the above-mentioned problems and has a small decrease in the Kerr rotation angle even on the short wavelength side.

[0008]

According to a first aspect of the present invention, there is provided a magneto-optical recording medium having a first protective layer, a recording layer, and a second protective layer provided on a substrate. Preferably, the recording layer is formed by providing an alloy layer of a rare earth element and a transition metal element above and below an alloy layer of cobalt and chromium.

Further, as set forth in claim 2, claim 1
Use rare earth elements of the mounting and as an alloy layer of a transition metal element, lanthanum, cerium, neodymium, praseodymium and at least one of summary <br/> Riu arm and the heavy rare earth elements including one element of the alloy layer of the transition metal element It is characterized by having been.

According to a third aspect of the present invention, the alloy layer of cobalt and chromium has a cobalt content of 85 to 95 atomic%.

[0011]

When the alloy layer of cobalt and chromium is used as the recording layer, the rare earth-transition metal alloy layer of Tb-Fe-Co shown by the curve b, or the neodymium-transition metal shown by the curve c, as shown by the curve a in FIG. Compared to a rare earth-transition metal alloy layer containing a light rare earth element such as dysprosium-iron-cobalt (NdDyFeCo), the Kerr rotation angle does not decrease even on the short wavelength side of 500 nm.

However, the Co-Cr alloy layer has a small coercive force as compared with the rare earth-transition metal alloy, and is unsuitable as a material for a recording layer of a magneto-optical recording medium. Therefore, a magneto-optical recording medium having a three-layer structure in which a Co-Cr alloy layer having a small coercive force is sandwiched between rare earth-transition metal alloy layers having a large coercive force.

Since the recording of information is performed by the rare earth-transition metal alloy layer by using the recording layer having the three-layer structure, the coercive force of the rare earth-transition metal alloy layer only needs to be kept large. Become.

[0014] The Kerr rotation angle is the rare earth on the light incident side.
When the thickness of the transition metal alloy layer is kept small and light is transmitted through this layer, the transition metal alloy layer is kept large under the influence of the Co-Cr layer having a large Kerr rotation angle.

More specifically, it is preferable that the thickness of the rare earth-transition metal alloy layer be kept at 5 to 20 nm. The Co-Cr alloy layer used as the recording layer has a Co content of 85 to 95 atomic%.
And The reason for this is that the content of Co is, for example, 80
Atomic%, the Kerr rotation angle is about the same as 85%
When the content decreases to 1/2 and the Co content is 95 atomic% or more, the recording layer does not exhibit perpendicular magnetic anisotropy. Is set to 85 to 95 atomic%.

By doing so, the Kerr rotation angle becomes large, and this recording layer becomes a perpendicular magnetization film, thereby increasing the recording and reproducing effects. Both of the Co-Cr layers are sandwiched between layers using an alloy layer of a heavy rare earth element and a transition metal element containing at least one of the light rare earth elements of lanthanum, cerium, neodymium, praseodymium and samarium. Even in this case, a high-quality magneto-optical recording medium with a small decrease in the Kerr rotation angle even on the short wavelength side can be obtained as in the case of sandwiching between the rare earth-transition metal alloy layers.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. First Embodiment As shown in FIG. 1A, the magneto-optical recording medium of the present embodiment has a glass substrate 1 on which a Y-SiO ₂ film as an interference layer and a first protective layer 2-1 is formed. The first rare earth-transition metal layer 4A-1 composed of a Tb ₂₁ Fe ₇₁ Co ₈ layer is formed by sputtering to a thickness of 90 nm, and a first rare earth-transition metal layer 4A-1 composed of a Tb ₂₁ Fe ₇₁ Co ₈ layer is formed by sputtering to a thickness of 10 nm. Co-Cr layer 11 of 90 atomic% of Co is formed to a thickness of 10 nm,
Further thereon, a second rare earth-transition metal layer 4A-2 composed of a Tb ₂₁ Fe ₇₁ Co ₈ layer was formed to a thickness of 80 nm by sputtering to form a recording layer 3. Furthermore, Y-SiO _{2 is formed} thereon as a second protective layer 2-2.
The film was formed to a thickness of 90 nm using a sputtering method to form a magneto-optical recording medium.

Further, such a magneto-optical recording medium according to the present embodiment is manufactured by using a laser beam having a wavelength of 514.5 nm and a linear velocity of 10 m / sec.
When the signal was recorded with a bit length of 0.5 μm, a value of 45 dB in C / N was obtained.

Modification Example 1 of First Embodiment As shown in FIG. 1B, the magneto-optical recording medium of this embodiment is formed on a glass substrate 1 as an interference layer and as a first protective layer 2-1. A 90-nm thick Y-SiO2 film is formed by sputtering, and a first rare earth-transition metal layer 4B-1 composed of a Dy ₂₆ Fe ₅₆ Co ₁₈ layer is formed thereon by sputtering to a thickness of 10 nm. And a Co-Cr layer 11 of 90 atomic% Co with a thickness of 10 nm is formed thereon,
Further, a second rare earth-transition metal layer 4B-2 composed of a Dy ₂₆ Fe ₅₆ Co ₁₈ layer was formed thereon to a thickness of 80 nm by a sputtering method to form a recording layer 3. On top of that, a second protective layer 2-2 is formed as Y-
An SiO ₂ film was formed to a thickness of 90 nm by a sputtering method to form a magneto-optical recording medium.

Further, such a magneto-optical recording medium of this embodiment is manufactured by using a laser beam having a wavelength of 514.5 nm, and has a linear velocity of 10 m / sec.
When a signal was recorded with a bit length of 0.5 μm, a C / N of 43 dB was obtained.

Modification 2 of First Embodiment As shown in FIG. 1C, the magneto-optical recording medium of this embodiment is formed on a glass substrate 1 as an interference layer and as a first protective layer 2-1. A 90-nm thick Y-SiO ₂ film is formed by sputtering, and a first rare earth-transition metal layer 4C-1 composed of a Gd ₂₆ Tb ₅₆ Co ₁₈ layer is sputtered thereon to a thickness of 10 nm. And a Co-Cr layer 11 of 90 atomic% of Co is formed thereon to a thickness of 10 nm.
Further, a second rare earth-transition metal layer 4C-2 composed of a Gd ₂₆ Tb ₅₆ Co ₁₈ layer was formed thereon to a thickness of 80 nm by a sputtering method to form a recording layer 3. Further, a second protective layer 2-2 is formed thereon as Y-Si
An O ₂ film was formed to a thickness of 90 nm by a sputtering method to form a magneto-optical recording medium.

Further, the magneto-optical recording medium of the present embodiment is manufactured by using a laser beam having a wavelength of 514.5 nm and a linear velocity of 10 m / sec.
When a signal was recorded with a bit length of 0.5 μm, a C / N of 44 dB was obtained.

Comparative Example 1 For comparison with the above-described example, a recording layer was formed using only the rare earth-transition metal alloy layer.

As shown in FIG. 4A, on a glass substrate 1,
Y-SiO as first protective layer 2-1 as interference layer_TwoMembrane
Sputtered to a thickness of 90 nm, and Tb_{twenty one}Fe
₇₁Co ₈The recording layer 3 is formed to a thickness of 100 nm.
Y-SiO as a second protective layer 2-2_TwoUse sputtering method for film
Then, a film was formed to a thickness of 90 nm to form a magneto-optical recording medium.

Further, such a magneto-optical recording medium of this embodiment is manufactured by using a laser beam of 830 nm, a linear velocity of 10 m / sec, and a bit length of
When the signal was recorded at 0.8 μm, the C / N was 50 dB. However, when a short-wavelength laser beam of 514.5 nm was used, when the signal was recorded at a linear velocity of 10 m / sec and a bit length of 0.5 μm, only a value of 38 dB was obtained for the C / N.

Second Embodiment Instead of the first and second rare earth element-transition metal element alloy layers used in the first embodiment, light rare earth element lanthanum is used.
(La), cerium (Ce), neodymium (Nd), praseodymium
A film was formed using an alloy layer of a transition metal element and a heavy rare earth element containing one element of (Pr) and samarium (Sm).

As shown in FIG. 2A, in the magneto-optical recording medium of this embodiment, a Y-SiO ₂ film as an interference layer and a first protective layer 2-1 is formed on a glass substrate 1 by sputtering. A first heavy and light rare earth-transition metal layer 5A-1 composed of a Nd ₃ Dy ₂₃ Fe ₆₃ Co ₁₁ layer is formed thereon by a sputtering method to a thickness of 10 nm, On top of this, a 90 atomic% Co-Cr layer
a second heavy and light rare earth-transition metal layer 5A-2 composed of an Nd ₃ Dy ₂₃ Fe ₆₃ Co ₁₁ layer is formed thereon by sputtering to a thickness of 80 nm. The recording layer 3 was obtained. Further, a Y-SiO ₂ film is formed thereon as a second protective layer 2-2 by a sputtering method.
A film was formed to a thickness of 90 nm to form a magneto-optical recording medium.

In the magneto-optical recording medium having such a structure, in the state where no enhancement is provided without providing the first protective layer as an interference layer, that is, in the state where there is no reflection from the first protective layer, the wavelength is increased. When the Kerr rotation angle was measured by irradiating the magneto-optical recording medium with a laser beam of 500 nm, a value of 0.34 degrees was obtained.

Further, such a magneto-optical recording medium of this embodiment is manufactured by using a laser beam having a wavelength of 514.5 nm and a linear velocity of 10 m / sec.
When the signal was recorded with a bit length of 0.5 μm, a C / N of 46 dB was obtained.

Modification Example 1 of Second Embodiment As shown in FIG. 2B, the magneto-optical recording medium of this embodiment is formed on a glass substrate 1 as an interference layer and as a first protective layer 2-1. A Y-SiO ₂ film is formed to a thickness of 90 nm by a sputtering method, and a first heavy-light rare earth-transition metal layer 5B-1 composed of a Pr ₃ Dy ₂₃ Fe ₆₃ Co ₁₁ layer is formed thereon to a thickness of 10 nm. Then, a Co-Cr layer 11 of 90 atomic% of Co is formed thereon to a thickness of 10 nm, and a second layer of a Pr ₃ Dy ₂₃ Fe ₆₃ Co ₁₁ layer is further formed thereon.
The heavy and light rare earth-transition metal layer 5B-2 was formed to a thickness of 80 nm by a sputtering method to form a recording layer 3. Further, a Y-SiO ₂ film was formed thereon as a second protective layer 2-2 to a thickness of 90 nm by sputtering to form a magneto-optical recording medium.

In the magneto-optical recording medium having such a structure, a laser beam having a wavelength of 500 nm is irradiated to the magneto-optical recording medium without enhancement without providing the first protective layer as an interference layer. When the Kerr rotation angle was measured, a value of 0.35 degrees was obtained.

Further, the magneto-optical recording medium of this embodiment is manufactured by using a laser beam having a wavelength of 514.5 nm and a linear velocity of 10 m / sec.
When the signal was recorded with a bit length of 0.5 μm, a value of 45 dB in C / N was obtained.

Modified Example 2 of Second Embodiment As shown in FIG. 2C, the magneto-optical recording medium of this embodiment is formed on a glass substrate 1 as an interference layer and as a first protective layer 2-1. A Y-SiO ₂ film is formed to a thickness of 90 nm by a sputtering method, and a first heavy-light rare earth-transition metal layer 5C-1 composed of a Nd ₅ Tb ₂₂ Fe ₅₆ Co ₁₇ layer is formed thereon to a thickness of 10 nm. Then, a Co-Cr layer 11 of 90 atomic% of Co is formed thereon to a thickness of 10 nm, and a second Nd ₅ Tb ₂₂ Fe ₅₆ Co ₁₇ layer is further formed thereon.
The recording layer 3 was formed by depositing a heavy-light rare earth-transition metal layer 5C-2 having a thickness of 80 nm by a sputtering method. Further, a Y-SiO ₂ film was formed thereon as a second protective layer 2-2 to a thickness of 90 nm by sputtering to form a magneto-optical recording medium.

In the magneto-optical recording medium having such a structure, a laser beam having a wavelength of 500 nm is irradiated on the magneto-optical recording medium without enhancement without providing the first protective layer as an interference layer. When the Kerr rotation angle was measured, a value of 0.36 degrees was obtained.

Further, the magneto-optical recording medium of the present embodiment is manufactured by using a laser beam having a wavelength of 514.5 nm and a linear velocity of 10 m / sec.
When the signal was recorded with a bit length of 0.5 μm, a C / N of 46 dB was obtained.

Modification 3 of the Second Embodiment As shown in FIG. 2D, the magneto-optical recording medium of this embodiment is formed on a glass substrate 1 as an interference layer and as a first protective layer 2-1. A Y-SiO ₂ film is formed to a thickness of 90 nm by a sputtering method, and a first heavy-light rare earth-transition metal layer 5D-1 composed of a Sm ₃ Tb ₂₃ Fe ₅₇ Co ₁₇ layer is formed thereon to a thickness of 10 nm. Then, a Co-Cr layer 11 of 90 atomic% of Co is formed thereon to a thickness of 10 nm, and a second Sm ₃ Tb ₂₃ Fe ₅₇ Co ₁₇ layer is further formed thereon.
The recording layer 3 was formed by depositing the heavy and light rare earth-transition metal layer 5D-2 to a thickness of 80 nm by sputtering. Further, a Y-SiO ₂ film was formed thereon as a second protective layer 2-2 to a thickness of 90 nm by sputtering to form a magneto-optical recording medium.

Further, the magneto-optical recording medium of this embodiment is manufactured by using a laser beam having a wavelength of 514.5 nm at a linear velocity of 10 m / sec.
When the signal was recorded with a bit length of 0.5 μm, a C / N of 46 dB was obtained.

In the magneto-optical recording medium having such a structure, a laser beam having a wavelength of 500 nm is irradiated on the magneto-optical recording medium without enhancement without providing the first protective layer as an interference layer. When the car rotation angle was measured, a value of 0.34 degrees was obtained.

COMPARATIVE EXAMPLE 2 In order to compare with the second embodiment, the recording layer was made of a rare earth element.
-A film was formed using only the transition metal alloy layer or only the heavy and light rare earth-transition metal alloy layer.

Comparative Example 2-1 As shown in FIG. 4A, a Y-SiO ₂ film as an interference layer and as a first protective layer 2-1 was formed on a glass substrate 1 to a thickness of 90 nm by sputtering. A recording layer 3 made of Tb ₂₁ Fe ₇₁ Co ₈ is formed thereon to a thickness of 100 nm, and a Y-SiO ₂ film is sputtered thereon as a second protective layer 2-2. A magneto-optical recording medium was formed by forming a film to a thickness of 90 nm by using the method.

In the magneto-optical recording medium having such a structure, a laser beam having a wavelength of 500 nm is irradiated on the magneto-optical recording medium without enhancement without providing the first protective layer as an interference layer. When the car rotation angle was measured, only a value of 0.25 degrees was obtained.

Further, such a magneto-optical recording medium of this embodiment is irradiated with a laser beam of 830 nm, and has a linear velocity of 10 m / sec and a bit length of 10 m / sec.
When the signal was recorded at 0.8 μm, the C / N was 50 dB. However, when a short-wavelength laser beam of 514.5 nm was used, when the signal was recorded at a linear velocity of 10 m / sec and a bit length of 0.5 μm, only a value of 38 dB was obtained for the C / N.

Comparative Example 2-2 As shown in FIG. 4 (b), a Y-SiO ₂ film as an interference layer and as a first protective layer 2-1 was formed on a glass substrate 1 to a thickness of 90 nm by sputtering. A recording layer 3 made of Nd ₃ Dy ₂₃ Fe ₆₃ Co ₁₁ is formed thereon to a thickness of 100 nm, and a Y-SiO ₂ film is formed thereon as a second protective layer 2-2. Was formed to a thickness of 90 nm by sputtering to form a magneto-optical recording medium.

In the magneto-optical recording medium having such a structure, a laser beam having a wavelength of 500 nm is irradiated to the magneto-optical recording medium without enhancement without providing the first protective layer as an interference layer. When the car rotation angle was measured, only a value of 0.27 degrees was obtained.

Further, such a magneto-optical recording medium of this embodiment is irradiated with a laser beam of 830 nm, and has a linear velocity of 10 m / sec and a bit length of 10 m / sec.
When the signal was recorded at 0.8 μm, the C / N was 50 dB. However, when a laser beam with a short wavelength of 514.5 nm was used, when the signal was recorded at a linear velocity of 10 m / sec and a bit length of 0.5 μm, the C / N was only 40 dB.

Table 1 shows the first embodiment of the present invention, and Table 2 shows the second embodiment.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

As described above, according to the magneto-optical recording medium of the present invention, even when a short-wavelength laser beam is irradiated, a decrease in the Kerr rotation angle is small, and the C / N value of the recording signal is reduced. There is an effect that a high-quality magneto-optical recording medium suitable for high-density recording with little reduction can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a diagram showing the relationship among the type of magneto-optical recording medium, the Kerr rotation angle, and the wavelength of incident light.

FIG. 4 is a sectional view showing a comparative example of the magneto-optical recording medium of the first embodiment and the second embodiment.

FIG. 5 is a sectional view of a conventional magneto-optical recording medium.

[Explanation of symbols]

 1 Glass substrate 2-1 First protective layer 2-2 Second protective layer 3 Recording layer 4A-1,4B-1,4C-1 First rare earth-transition metal layer 4A-2,4B-2,4C -2 Second rare earth-transition metal layer 5A-1,5B-1,5C-1,5D-1 First heavy and light rare earth-transition metal layer 5A-2,5B-2,5C-2,5D-2 Second heavy-light rare earth-transition metal layer 11 Co-Cr layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 11/105

Claims (3)

(57) [Claims] In a magneto-optical recording medium having a first protective layer, a recording layer, and a second protective layer provided on a substrate, the recording layer is formed by transition between a rare-earth element and a cobalt-chromium alloy layer above and below. A magneto-optical recording medium formed by providing an alloy layer of a metal element. 2. An alloy layer of a rare earth element and a transition metal element according to claim 1 , wherein lanthanum, cerium, neodymium,
Praseodymium and magneto-optical recording medium, characterized in that an alloy layer of at least the heavy rare-earth element and a transition metal element include one element among samarium. 3. A magneto-optical recording medium according to claim 1, wherein said cobalt and chromium alloy layer has a cobalt content of 85 to 95 atomic%.