JP2544684B2 - Magneto-optical recording medium - Google Patents

Description

The present invention relates to a magneto-optical recording medium having a novel layer structure and a magnetic thin layer having a novel composition.

Conventionally, amorphous magnetic alloy films Gd-Co, Gd-Fe, Tb-Fe, Gd-Tb-Fe, Dy
Although -Tb-Fe or the like was used, the magneto-optical characteristics, the Kerr or Faraday rotation angle were insufficient, and the S / N during reproduction was low. When the Curie temperature is raised, for example, the Kerr rotation angle improves like Gd-Tb-Fe, but the Kerr rotation angle is still insufficient, and when the Curie temperature is high, the laser power during recording is large. There is.

Therefore, the present inventors have already proposed to increase the Kerr rotation angle by using a TbFeCo-based alloy as the magnetic film of the magneto-optical memory material. However, although the Kerr rotation angle is improved by using TbFeCo, the magneto-optical characteristics are not sufficiently satisfactory. Further, since the Curie temperature is high, it is necessary to increase the laser power at the time of recording, and as a result, there is a problem that a sufficient recording speed cannot be obtained.

The present invention has been made in view of the above problems, and in the alloy thin film of a transition metal (Fe, Co) and a rare earth (Dy, Tb, Gd), the magnetic moment of the transition metal mainly acts on the magneto-optical effect. We selected a magnetic alloy composition with a large Kerr or Faraday rotation angle while paying attention to the fact that the transition metal is properly combined with a rare earth element to minimize the laser power during recording, and a new layer structure is adopted. By doing so, it is possible to record with a small amount of energy and to have a large amount during playback.
Succeeded in developing a magneto-optical recording medium capable of obtaining S / N and completed the present invention.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magneto-optical recording medium having a small laser power on a memory medium during recording. It is another object of the present invention to provide a magneto-optical recording medium having a large S / N during reproduction, that is, a Kerr or Faraday rotation angle.

A first magneto-optical recording medium of the present invention has a structure in which a high refractive index layer, a magnetic thin layer and an antioxidant layer are sequentially provided on a substrate, and the magnetic thin layer has the following general formula (I) to It is characterized by comprising at least one kind of magnetic alloy film selected from (VI).

(Tb _X Dy _1-X ) _Z (FeyCo _1-y ) _1-Z (I) (Tb _X Bi _1-X ) _Z (FeyCo _1-y ) _1-Z (II) (Gd _X Dy _1-X ) _Z (FeyCo _1-y ) _1-Z (III) (Gd _X Bi _1-X ) _Z (FeyCo _1-y ) _1-Z (IV) (Dy _X Bi _1-X ) _Z (FeyCo _1-y ) _{1 -Z} (V) (Gd _X Tb _1-X ) _Z (FeyCo _1-y ) _1-Z (VI) (wherein 0.0 <x <1.0, 0.7 ≦ y ≦ 0.99 and 0.1 <z <
It is 0.3. The second of the magneto-optical recording medium of the present invention has a structure in which a magnetic thin layer, a high refractive index layer, a reflective layer and an antioxidant layer are sequentially provided on a substrate, and the magnetic thin layer has the following general formula: (I) ~
It is characterized by comprising at least one kind of magnetic alloy film selected from (VI).

(Tb _X Dy _1-X ) _Z (FeyCo _1-y ) _1-Z (I) (Tb _X Bi _1-X ) _Z (FeyCo _1-y ) _1-Z (II) (Gd _X Dy _1-X ) _Z (FeyCo _1-y ) _1-Z (III) (Gd _X Bi _1-X ) _Z (FeyCo _1-y ) _1-Z (IV) (Dy _X Bi _1-X ) _Z (FeyCo _1-y ) _{1 -Z} (V) (Gd _X Tb _1-X ) _Z (FeyCo _1-y ) _1-Z (VI) (wherein 0.0 <x <1.0, 0.7 ≦ y ≦ 0.99 and 0.1 <z <
It is 0.3. ) In the composition of the magnetic thin layer in the present invention, the Kerr or Faraday rotation angle is improved by two transition metals of Fe and Co, and perpendicular by the combination of two rare earth elements or the combination of one rare earth metal and Bi. It is considered that the anisotropy and Curie temperature are adjusted. Typical examples of the alloy composition used for the magnetic thin layer of the present invention include the following.

_{(Tb 0 · 5 Dy 0 ·} 5) 0 · 22 (Fe 0 · 8 Co 0 · 2) 0 · 78 ... (a) (Tb 0 · 9 Bi 0 · 1) 0 · 17 (Fe 0 · 78 Co 0 _{・ 22} ) _0.83 (b)
_{(Gd 0 · 5 Dy 0 ·} 5) 0 · 18 (Fe 0 · 9 Co 0 · 1) 0 · 82 ... (c) (Gd 0 · 85 Bi 0 · 15) 0 · 26 (Fe 0 · 88 Co 0 _{・ 12} ) _0.74 … (d)
_{(Dy 0 · 9 Bi 0 ·} 1) 0 · 25 (Fe 0 · 8 Co 0 · 2) 0 · 75 ... (e) (Gd 0 · 7 Tb 0 · 3) 0 · 24 (Fe 0 · 95 Co 0 _{・ 05} ) _0.76 … (f)
An important issue of the magneto-optical recording medium is that it requires a small amount of energy during recording, while a large S / N must be obtained during reproduction. The Curie temperature of the magnetic film, the film thickness, and the thermal conductivity of the medium are major factors in the energy during recording. FIG. 1 is a graph showing the relationship between the film thickness and the energy (laser output) required for recording. As is clear from this figure, the film thickness and the laser output are linearly proportional to the increase of the film thickness up to the film thickness of 200Å (0.02 μm). When the film thickness is less than 200 ° (0.02 μm), the laser output increases. This is because the laser light is transmitted and heat is not accumulated. Therefore,
In the present invention, it is appropriate that the thickness of the magnetic thin layer is 200 to 1000Å.

FIG. 2 is a graph showing the relationship between the synthetic composition used for the magnetic thin layer of the present invention and the recordable output (laser power mW) and Curie temperature (° C.). In the graph, the solid line shows the laser wiper and the dotted line shows the Curie temperature. As the recording conditions, an LD wavelength of 800 nm, a laser pulse width of 5 μs, an external magnetic field 2000 e, and a film thickness of 200Å to 1000Å are used. As the amount of Dy having a low Curie temperature increases, the Curie temperature decreases, and the output of the laser power required for recording decreases.

The configuration of the magneto-optical recording medium of the present invention will be described below with reference to the drawings.

FIG. 3A is a schematic view showing an example of the layer structure of the magneto-optical recording medium of the present invention, in which a high refractive index layer 3, a magnetic thin layer 2 and an antioxidant layer 4 are sequentially provided on a substrate 1. Therefore, a reflection layer may be provided on the antioxidant layer 4 if necessary. Third
FIG. 2B is a schematic diagram showing another example of the layer configuration, and the substrate 1
A magnetic thin layer 2, a high refractive index layer 3, a reflective layer 5, and an antioxidant layer 6 are sequentially provided thereon. The magnetic thin layer 2 may be a single layer or a laminated layer.

As the substrate, glass, plastic, or the like can be used.

The high refractive index layer is, for example, Fe ₂ O ₃ , TiO ₂ , CeO ₂ , Sb ₂ O ₃ , W
An object having a refractive index of 2.0 or more, such as O ₃ , SiO, Bi ₂ O ₃ , and CdO, is attached by a sputtering method.

MgO, Al ₂ O ₃ , SiO ₂ , TiO ₂ and Th as the antioxidant layer
O ₂ oxide is used, and the film thickness is 1000 Å or more.

In FIG. 3 (B), a magnetic thin layer is attached on the substrate with a film thickness of 200 to 500Å, and the laser beam during reproduction can be transmitted.

As the reflection layer, metal thin films Cu, Ag, Cr, Al, Rh, Au, Ni and the like are used. When a metal thin film is used for the reflective layer, an antioxidation layer is required on it.

Next, a production example of the magneto-optical recording medium of the present invention will be specifically described.

First, a magnetic layer was formed on a glass substrate having a thickness of 1 mm by applying an argon gas pressure of 3 × 10 ^-2 Torr, a discharge power of 300 W, and a film formation speed of 20 mm / sec.
It is manufactured under the following conditions. Sputtering is performed by rotating the substrate using three targets. For example, the Gd, Tb, and Fe Co magnetic layers are arranged on the target such that Gd, Tb, and Co chips are arranged on the Fe target at an area ratio corresponding to the magnetic layer. One target is a high refractive index layer such as SiO, and the other target is an antioxidant layer such as MgO.
Each of the laminated films is one in which the shutter on the target is opened and closed in the same vacuum and the films are sequentially laminated to produce a magneto-optical recording medium.

Table 1 below shows an example of the configuration of the magneto-optical recording medium of the present invention produced as described above. In the column of the magnetic thin layer, (a), (b), (c), (d), (e) and (f) respectively correspond to the alloy compositions exemplified above. Regarding the magneto-optical recording medium of the present invention shown in Table 1, Kerr rotation angle (θ _K ) and Faraday rotation angle θ _F measured with a laser (wavelength 800 nm and intensity of 1 mW on the medium surface) and recording frequency 2 M bit / The recording laser power in s is shown in Table 2 below.
Shown in

Table 2 θ _K due to Kerr effect (for sample A) and θ _F due to Faraday effect (for sample B) Sample No. (deg) Recording laser power A-1 0.58 7mW A-2 0.52 8 A-3 0.62 7 A-4 0.64 6 A-5 0.60 5 A-6 0.74 6 B-1 0.68 2.5 B-2 0.60 2.8 B-3 0.74 2.8 B-4 0.72 2.5 B-5 0.70 2.3 B-6 0.88 3.5 As described above, in the magneto-optical recording medium according to the present invention, since the composition of the magnetic alloy film is defined as described above, it exhibits a sufficient Kerr rotation angle or Faraday rotation angle, and the laser power at the time of recording is also an appropriate value. be able to. Incidentally, the Kerr rotation angle of a conventional ternary magnetic alloy film such as TbFeCo, TbDyFe, GdDyFe, and GdTbFe has a Kerr rotation angle of about 0.2 to 0.35 deg.
-159252 gazette), it can be seen that the present invention is considerably improved. Further, in the magneto-optical recording medium according to the present invention, the composition of the magnetic alloy film is specified, and the layer structure in which the high refractive index layer and the antioxidant layer or the high refractive index layer, the reflective layer and the antioxidant layer are provided is adopted. The effects such as enhancement of the Kerr effect or Faraday effect due to multiple reflection of laser light in the high refractive index layer, weight of the Kerr effect and Faraday effect by the reflection layer, and prevention of deterioration of the magnetic alloy film by the antioxidation layer can be expected.

The magneto-optical recording medium according to the present invention can be applied to both the optical modulation method and the magnetic field modulation method, and can also be applied to an overwriting type recording method.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the film thickness of the magnetic thin film and the recording energy, FIG. 2 is a graph showing the relationship between the alloy composition of the magnetic thin layer and the recording energy, and FIG. 3 (A). And (B) are schematic views showing the layer structure of the magneto-optical recording medium. 1 ... Substrate, 2 ... Magnetic thin film, 3 ... High refractive index layer, 4,6
...... Antioxidant layer, 5 ...... Reflective layer.

Claims (2)

(57) [Claims] 1. A structure in which a high refractive index layer, a magnetic thin layer and an antioxidant layer are sequentially provided on a substrate, and the magnetic thin layer is selected from the following general formulas (I) to (VI). A magneto-optical recording medium comprising at least one type of magnetic alloy film. (Tb _X Dy _1-X ) _Z (FeyCo _1-y ) _1-Z (I) (Tb _X Bi _1-X ) _Z (FeyCo _1-y ) _1-Z (II) (Gd _X Dy _1-X ) _Z (FeyCo _1-y ) _1-Z (III) (Gd _X Bi _1-X ) _Z (FeyCo _1-y ) _1-Z (IV) (Dy _X Bi _1-X ) _Z (FeyCo _1-y ) _{1 -Z} (V) (Gd _X Tb _1-X ) _Z (FeyCo _1-y ) _1-Z (VI) (wherein 0.0 <x <1.0, 0.7 ≦ y ≦ 0.99 and 0.1 <z <
It is 0.3. ) 2. A structure in which a magnetic thin layer, a high refractive index layer, a reflective layer and an antioxidant layer are sequentially provided on a substrate, and the magnetic thin layer is represented by the following general formulas (I) to (VI). A magneto-optical recording medium comprising at least one magnetic alloy film selected from the inside. (Tb _X Dy _1-X ) _Z (FeyCo _1-y ) _1-Z (I) (Tb _X Bi _1-X ) _Z (FeyCo _1-y ) _1-Z (II) (Gd _X Dy _1-X ) _Z (FeyCo _1-y ) _1-Z (III) (Gd _X Bi _1-X ) _Z (FeyCo _1-y ) _1-Z (IV) (Dy _X Bi _1-X ) _Z (FeyCo _1-y ) _{1 -Z} (V) (Gd _X Tb _1-X ) _Z (FeyCo _1-y ) _1-Z (VI) (wherein 0.0 <x <1.0, 0.7 ≦ y ≦ 0.99 and 0.1 <z <
It is 0.3. )