JPH05250737A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To provide a magneto-optical recording medium having such intermediate layer as the exchange bonding force between a memory layer and a recording layer does not fluctuate even if overwrite test is repeated and which can be overwritten through an optical modulation system. CONSTITUTION:The magneto-optical recording medium comprises a recording layer 3 and a memory layer 5 composed of a thin film of rear earth-transition metal amorphous alloy and an intermediate layer 4-1 for controlling the exchange bonding force between the recording layer 3 and the memory layer 5. The intermediate layer 4-1 is composed of a film formed by sputtering at least one nonmagnetic rear earth element, e.g. yttrium or scandium, or lanthanum element and the film thickness of the intermediate layer 4-1 is set in the range of 5-10Angstrom .

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 that includes a recording layer and a memory layer and can be overwritten by an optical modulation method.

[0002]

2. Description of the Related Art Conventionally, as a magneto-optical recording medium which can be overwritten by an optical modulation method, a transparent substrate such as polycarbonate or a glass substrate, for example, terbium-iron-cobalt (Tb-Fe-Co) is used. A recording layer made of a rare earth-transition metal amorphous alloy and a memory layer are laminated and provided. The recording layer is formed by changing the composition of the elements forming the recording layer and the memory layer so that the coercive force is higher at room temperature and the Curie temperature is lower than that of the memory layer.

In order to further control the exchange coupling force between the recording layer and the memory layer, the rare earth-transition metal amorphous alloy forming the recording layer and the memory layer is nitrided between the recording layer and the memory layer. Overwritable magneto-optical recording media formed by providing an intermediate layer made of a film have been developed.

[0004]

The nitride film obtained by nitriding the rare earth-transition metal alloy used for the intermediate layer has the effect of controlling the exchange coupling force between the recording layer and the memory layer to a predetermined value. However, in the process of repeating the overwrite test many times, the recording medium is heated by the irradiation of the laser power, and this heating may separate nitrogen in the nitride film of the rare earth-transition metal alloy of the intermediate layer.

Then, the separated nitrogen moves from the intermediate layer to the recording layer or the memory layer and diffuses, so that the constituent components of the intermediate layer fluctuate, so that the exchange coupling force between the recording layer and the memory layer is increased. It fluctuates and affects the characteristics of the magneto-optical recording medium.

In order to eliminate such inconvenience, it is desirable to use, for the intermediate layer, a material whose exchange coupling force does not change between the memory layer and the recording layer even when the overwrite test is repeated.

An object of the present invention is to solve the above problems and to provide a magneto-optical recording medium having an intermediate layer in which the exchange coupling force between the memory layer and the recording layer does not fluctuate even if the overwrite test is repeated.

[0008]

According to a first aspect of the present invention, a magneto-optical recording medium is provided with a rare earth-transition metal amorphous alloy thin film as a recording layer and a memory layer, and between the recording layer and the memory layer. In a magneto-optical recording medium having an intermediate layer for controlling exchange coupling force, a sputtered film formed of at least one element of nonmagnetic rare earth elements yttrium, scandium, or lanthanum is used for the intermediate layer. The film thickness of the intermediate layer is in the range of 5 to 10Å.

Further, the magneto-optical recording medium of the present invention comprises:
As shown in FIG. 4, a sputtered film formed of an alloy film of at least one element of nonmagnetic rare earth elements yttrium, scandium, or lanthanum and a rare earth transition metal amorphous alloy film is used as the intermediate layer, Layer thickness 50-150
It is characterized in that the range is Å, and the addition amount of the nonmagnetic rare earth element in the alloy film is 30 to 40 atom%.

[0010]

[Function] Elements such as yttrium (Y), scandium (Sc) and lanthanum (La) are non-magnetic rare earth elements having no magnetism. Therefore, a simple substance of elements such as Y, Sc, and La, or a combination of two or more of these elements is formed into an alloy,
When the intermediate layer is formed between the recording layer and the memory layer, the exchange coupling force between the recording layer and the memory layer is weakened by the intermediate layer. Since this intermediate layer is a simple substance or an intermetallic compound, unlike the conventional nitride intermediate layer, it does not decompose even when heated during overwriting.

When the thickness of the intermediate layer is controlled to a predetermined value, the exchange coupling force between the recording layer and the memory layer can be controlled to a predetermined value. In addition, if other elements such as Y, Sc, La, etc. are mixed with the rare earth-transition metal alloy forming the recording layer or the memory layer to form an alloy, the magnetism originally possessed by the rare earth-transition metal alloy becomes Since it is weakened by the addition of such elements as Y, Sc, and La, the perpendicular magnetic anisotropy becomes small.

Therefore, an alloy formed by adding these nonmagnetic rare earth elements to the rare earth-transition metal alloy forming the recording layer or the memory layer is used for the intermediate layer, and the nonmagnetic rare earth element is used as the rare earth-transition metal alloy. The exchange coupling force between the recording layer and the memory layer can be controlled to a predetermined value by adjusting the ratio of addition to the alloy and the thickness of the intermediate layer.

Further, the non-magnetic rare earth element is
Unlike the conventional nitride intermediate layer, the intermediate layer made of the alloy formed by adding to the transition metal alloy is an intermetallic compound. The separation does not cause compositional fluctuations, so that the phenomenon of changing the exchange coupling force between the memory layer and the recording layer does not occur.

[0014]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 (a) is a sectional view of a magneto-optical recording medium according to a first embodiment of the present invention. As shown in the figure, on a transparent plastic substrate 1 made of polycarbonate, terbium-silicon dioxide (Tb -SiO ₂ ) is provided on the lower protective film 2, and 600 Å is a heavy and light rare earth-transition metal amorphous alloy, neodymium-dysprosium-iron-cobalt (Nd-Dy-Fe-Co). 2) is provided.

Further, an intermediate layer 4-1 made of yttrium (Y) having a thickness of 5 Å is provided on the recording layer 3, and terbium-iron-cobalt (Tb-Fe-) having a thickness of 300 Å is further provided thereon. A memory layer 5 made of Co) is provided, and the uppermost layer has a thickness of
An upper protective film 6 made of 1600Å terbium-silicon dioxide (Tb-SiO ₂ ) is provided.

To form such a magneto-optical recording medium, as shown in FIG. 1 (a) and FIG.
After exhausting the inside of the sputter chamber 11 to a vacuum degree of about 5 × 10 ^-5 Pa using an exhaust pump (not shown) connected to the exhaust pipe 12 inside, open the valve 14 of the gas introduction pipe 13 and argon. (A
r) Gas is introduced up to a pressure of 0.2 Pa, at which pressure Tb-SiO ₂
A high-frequency power is applied between the target 15 for forming a protective film and the substrate 1 to form a lower protective film 2 made of Tb-SiO ₂ on the substrate 1 by magnetron sputtering to a thickness of 1600Å.

Next, the recording layer 3 made of Nd-Dy-Fe-Co is formed on the substrate using the recording layer forming target 16 made of Nd-Dy-Fe-Co to a thickness of 600 Å. Next, the intermediate layer 4-1 made of Y is formed on the recording layer 3 by using the intermediate layer forming target 17-1 made of Y with a thickness of 5Å.

Then, using the memory layer forming target 18 made of Tb-Fe-Co, the memory layer 5 made of Tb-Fe-Co is formed on the intermediate layer 4 to a thickness of 300 Å. Then the above Tb
- on the memory layer 5 using the protective film formation target 15 made of SiO _2, to form the upper protective layer 6 made of Tb-SiO ₂ in a thickness of 1600 Å.

Here, in order to keep the film thickness of the intermediate layer at an optimum value, a magneto-optical recording medium in which the film thickness of the intermediate layer is changed by the above-described film forming method is formed, and in this magneto-optical recording medium. The relationship between the film thickness of the intermediate layer and the magnetic domain wall energy σ _W between the recording layer and the memory layer is examined, and the result is shown in FIG. 3 (a).

In FIG. 3A, the horizontal axis represents the film thickness of the intermediate layer, and the vertical axis represents the interfacial domain wall energy σ _W between the recording layer and the memory layer. As shown in the figure, the thicker the intermediate layer, the weaker the exchange coupling force between the recording layer and the memory layer.

The first method when the thickness of the intermediate layer is changed
Table 1 shows the relationship between the thickness of the intermediate layer of the magneto-optical recording medium of the example and the C / N upon overwriting.

[0022]

[Table 1]

From Table 1, it has been found that when the thickness of the intermediate layer is in the range of 5 to 10Å, the C / N value in overwriting becomes 45 dB or more, which is sufficiently practical. FIG. 1 (b) is a sectional view of a magneto-optical recording medium according to a second embodiment of the present invention. As shown, a transparent plastic substrate 1 made of polycarbonate is used.
On top, 1600Å thick terbium-silicon dioxide (Tb
A lower protective film 2 made of SiO ₂ ), and a recording layer 3 made of neodymium-dysprosium-iron-cobalt (Nd-Dy-Fe-Co) having a thickness of 600 Å formed on the lower protective film 2. An intermediate layer 4-2 made of yttrium-neodymium-dysprosium-iron-cobalt (Y-Nd-Dy-Fe-Co) is provided at a thickness of 100Å.

On top of that, terbium with a thickness of 300 Å-
A memory layer 5 made of iron-cobalt (Tb-Fe-Co) is provided, and an upper protective film 6 made of terbium-silicon dioxide (Tb-SiO ₂ ) having a thickness of 1600Å is provided on the uppermost layer. There is.

To form such a magneto-optical recording medium, as shown in FIGS. 1 (b) and 2 (b), a sputtering container is used.
After exhausting the inside of the sputter chamber 11 to a vacuum degree of about 5 × 10 ^-5 Pa using an exhaust pump (not shown) connected to the exhaust pipe 12 inside 11, open the valve 14 of the gas introduction pipe 13. Argon
(Ar) gas is introduced up to the pressure of 0.2Pa, and at this pressure, Tb-Si
High frequency power is applied between the protective film forming target 15 made of O ₂ and the substrate 1, and the substrate 1 is formed by the magnetron sputtering method.
A lower protective film 2 made of Tb-SiO ₂ is formed thereon with a thickness of 1600Å.

Next, a recording layer 3 made of Nd-Dy-Fe-Co is formed on the substrate using a recording layer forming target 16 made of Nd-Dy-Fe-Co to a thickness of 600 Å. Then Y-Nd-Dy-Fe-C
The intermediate layer 4-2 made of Y-Nd-Dy-Fe-Co is formed on the recording layer 3 by using the intermediate layer forming target 17-2 of the second embodiment.
Is formed with a thickness of 100 Å. The intermediate layer forming target 17-2 of the second embodiment is an alloy target of the recording layer forming target 16 made of Nd-Dy-Fe-Co and Y.

Next, using the memory layer forming target 18 made of Tb-Fe-Co, the memory layer 5 made of Tb-Fe-Co is formed on the intermediate layer 4-2 to a thickness of 300 Å. Then described above
On the memory layer 5 with Tb- protective film forming target 15 made of SiO _2, 1600 Å upper protective layer 6 made of Tb- SiO ₂
Formed with a thickness of.

Here, in order to keep the thickness of the intermediate layer at an optimum value, the magneto-optical recording medium of the second embodiment is formed in which the thickness of the intermediate layer is changed by the above-mentioned film forming method. The relationship between the film thickness of the intermediate layer and the interfacial domain wall energy σ _W between the recording layer and the memory layer in the magneto-optical recording medium of Example 2 is shown in FIG. 3 (b).

The horizontal axis of FIG. 3 (b) is Y-Nd-Dy-Fe-C of the second embodiment.
The film thickness of the intermediate layer consisting of o is shown, and the vertical axis shows the interface wall energy σ _W between the recording layer and the memory layer. As shown in the figure, the thicker the intermediate layer, the weaker the exchange coupling force between the recording layer and the memory layer.

The results of the overwrite test of the magneto-optical recording medium of the second embodiment are shown in FIG. Second from FIG.
The thickness of the intermediate layer made of Y-Nd-Dy-Fe-Co in the example is 50 to 15
When it is in the range of 0 Å, the C / N value during overwriting is 45
It was found that a practical magneto-optical recording medium could be obtained by using an intermediate layer having a film thickness in the range of dB or more.

Then, as in the second embodiment of FIG. 1 (b), after forming the lower protective film 2 on the substrate, neodymium-dysprosium-iron-cobalt (Nd-Dy-cobalt) having a thickness of 600 Å is formed. Fe-C
The recording layer 3 consisting of o) is provided, and yttrium-
Neodymium-Dysprosium-Iron-Cobalt (Y-Nd-Dy-F
An intermediate layer 4-2 made of e-Co) is provided with a thickness of 100 Å, and further terbium-iron-cobalt (Tb-
A magneto-optical recording medium having a memory layer 5 made of Fe-Co) and an upper protective film 6 is prepared.

The magneto-optical recording medium in which the thickness of the intermediate layer of Y-Nd-Dy-Fe-Co of the second embodiment is kept constant at 100 Å is used, and the optimum content of Y contained in this intermediate layer is used. In order to detect the specific content, the atomic% of Y contained in this intermediate layer is changed, and the result of an experiment on the relationship between the atomic% of Y and the interfacial domain wall energy between the recording layer and the memory layer is shown. As shown in FIG.

The horizontal axis of FIG. 5 is the atomic% of Y contained in the intermediate layer made of Y-Nd-Dy-Fe-Co, and the vertical axis is the interfacial domain wall energy between the recording layer and the memory layer. As shown in FIG. 6, when the Y content increases, the exchange coupling force between the recording layer and the memory layer tends to decrease.

FIG. 6 shows the relationship between the atomic percentage of Y contained in the intermediate layer of Y-Nd-Dy-Fe-Co and the C / N value at the time of overwriting of the formed magneto-optical recording medium. Shown in. The horizontal axis of FIG. 6 is the atomic% of Y contained in the intermediate layer made of Y-Nd-Dy-Fe-Co, and the vertical axis is the C / N value in overwrite.

As shown in FIG. 6, when the atomic percentage of Y contained in the intermediate layer of Y-Nd-Dy-Fe-Co is 30 to 40%, the C / N at the time of overwriting is practical. 45 dB as a guide for
It turns out that the value is exceeded.

As a modification of the first embodiment, the intermediate layer is formed by using a sputtered film of a light rare earth element such as Sc or La and a non-magnetic element instead of Y which is a constituent element of the intermediate layer. May be.

As a modification of the first embodiment, the above Y, S
Two or more elements of c and La may be appropriately combined to form an intermediate layer as an alloy film. As a modification of the first embodiment, instead of using Nd-Dy-Fe-Co for the recording layer and Tb-Fe-Co rare earth-transition metal amorphous metal alloy for the memory layer,
Rare earth metal elements other than gadolinium (Gd), for example, dysprosium (Dy), terbium (Tb), neodymium (Nd) and other elements, a recording layer, a memory layer by appropriately combining with a transition metal such as iron or cobalt. May be formed.

As a modification of the second embodiment, neodymium which is an amorphous alloy of rare earth-transition metal is used as the intermediate layer.
Dysprosium-iron-cobalt (Nd-Dy-Fe-Co) alloy with Y
Instead of adding, other non-magnetic elements such as light rare earth elements such as Sc and La are added in the same proportion as Y, and the neodymium-dysprosium-iron-cobalt (Nd-Dy-Fe-Co) is added.
It may be added to the alloy to form an alloy film.

As a modification of the second embodiment, neodymium, which is an amorphous alloy of rare earth-transition metal, is used as the intermediate layer.
Dysprosium-iron-cobalt (Nd-Dy-Fe-Co) alloy with Y
Instead of adding, two or more elements of Y, Sc, and La may be appropriately combined and added to a neodymium-dysprosium-iron-cobalt (Nd-Dy-Fe-Co) alloy.

As a modification of the second embodiment, the recording layer is
Nd-Dy-Fe-Co, instead of using Tb-Fe-Co rare earth-transition metal amorphous metal alloy for the memory layer, gadolinium (Gd)
Rare earth metal elements other than, for example, dysprosium (Dy),
An element such as terbium (Tb) and neodymium (Nd) is appropriately combined with a transition metal such as iron or cobalt to form a recording layer,
A memory layer may be formed.

[0041]

As described above, according to the magneto-optical recording medium of the present invention, a highly reliable medium having an intermediate layer in which the exchange coupling force between the memory layer and the recording layer does not change even if the overwrite test is repeated. There is an effect that a high-speed magneto-optical recording medium can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of first and second embodiments of the present invention.

FIG. 2 is an explanatory diagram of a manufacturing apparatus according to first and second embodiments of the present invention.

FIG. 3 is a relationship diagram between the film thickness of the intermediate layer and the interface domain wall energy in the first and second examples.

FIG. 4 is a graph showing the relationship between the thickness of the intermediate layer and the C / N ratio in overwriting according to the second embodiment.

FIG. 5 is a relationship diagram of Y concentration and interface domain wall energy in the second embodiment.

FIG. 6 is a relationship diagram of Y density and C / N in overwriting in the second embodiment.

[Explanation of symbols]

 1 Substrate 2 Lower protective film 3 Recording layer 4-1,4-2 Intermediate layer 5 Memory layer 6 Upper recording film 11 Sputter container 12 Exhaust pipe 13 Gas introduction pipe 14 Valve 15 Target for protective film formation 16 Target for recording layer formation 17 -1,17-2 Intermediate layer forming target 18 Memory layer forming target

Claims (2)

[Claims] 1. An intermediate for controlling exchange coupling between the recording layer (3) and the memory layer (5), wherein a rare earth-transition metal amorphous alloy thin film is provided as the recording layer (3) and the memory layer (5). In a magneto-optical recording medium having a layer (4-1), the intermediate layer (4-1) in the non-magnetic rare earth element yttrium,
Using a sputtered film formed of at least one element of scandium or lanthanum, the intermediate layer (4-1)
A magneto-optical recording medium having a thickness of 5 to 10 Å. 2. A rare earth-transition metal amorphous alloy thin film is provided as a recording layer (3) and a memory layer (5), and an intermediate layer for controlling the exchange coupling force between the recording layer (3) and the memory layer (5). In a magneto-optical recording medium having a layer (4-2), the intermediate layer (4-2) in the non-magnetic rare earth element yttrium,
A sputtering film formed of an alloy film of scandium or at least one element of lanthanum and a rare earth-transition metal amorphous alloy is used, and the thickness of the intermediate layer (4-2) is 50 to 150.
The magneto-optical recording medium is characterized in that the content of the non-magnetic rare earth element contained in the alloy film is 30 to 40 atomic% in the range of Å.