JPH0777043B2 - Magneto-optical recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention has a Curie temperature of 250 ° C.
The present invention relates to a magneto-optical recording medium having a magnetic thin layer made of a ferromagnetic oxide. More specifically, the present invention relates to a magneto-optical recording medium on which information can be written and recorded by light heat such as laser light.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
It is known to perform magneto-optical recording using a recording medium having an amorphous magnetic layer. However, these amorphous magnetic layers are easily oxidized, and if they are oxidized, the magneto-optical characteristics are deteriorated. Therefore, it is necessary to provide a protective layer on the amorphous magnetic layer immediately after forming the magnetic layer, which is a manufacturing problem. On the other hand, a ferromagnetic oxide such as ferrite is known to have a relatively large magneto-optical characteristic, but it has a problem that it is insufficient for application to magneto-optical recording and has a high Curie point.

The present invention has been made in view of the above problems, and provides a magneto-optical recording medium having a sufficiently large magneto-optical characteristic by using an iron oxide substituted with a specific metal for a magnetic thin layer. The purpose is to Another object of the present invention is to provide an oxide magnetic film that is neither oxidized nor corroded and has no deterioration in magnetic characteristics. Still another object of the present invention is to use an oxide magnetic material having a Curie temperature of 250 ° C. or lower as a material for the magneto-optical recording medium.

[0004]

In the magneto-optical recording medium of the present invention, a magnetic thin layer made of a ferromagnetic oxide represented by the following general formula 1 is provided on a transparent substrate, and the magnetic thin layer is further provided. It is characterized in that a transparent dielectric layer and a reflective layer are sequentially provided on the layer.

[Chemical 1]

Next, the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the magneto-optical recording medium of the present invention comprises a magnetic thin layer 2 provided on a transparent substrate 1, and a transparent dielectric layer 3 and a reflective layer 4 provided in this order on the magnetic thin layer 2.
The antioxidant layer 5 can be provided if necessary. As the transparent substrate, glass, quartz glass, heat resistant plastic or the like can be used. The thickness of the oxide magnetic thin layer on the substrate is about 100 to 30000Å, preferably 300.
It is ~ 5000Å. Next, a transparent dielectric layer 1000 to 5000 Å having a refractive index of about 2 is formed on this oxide magnetic thin layer. Further, a reflective layer such as Cu, Au, Ag, Pt, or Al is provided on the transparent dielectric layer in an amount of 500 to 1000.
About 0Å may be formed, and if necessary, an oxide such as SiO ₂ or TiO ₂ may be formed thereon as an antioxidant layer.

The ferromagnetic oxide constituting the oxide magnetic thin layer in the present invention is represented by the following general formula 1 and has a Curie temperature of 250 ° C. or lower. It is generally said that the oxide magnetic material cannot be used as a conventional magneto-optical memory material because of its high Curie temperature of 400 ° C. or higher.

[Chemical 1] (In the formula, the meaning of each symbol is as described above.) The present inventors have found that there is a specific relationship between the composition of the oxide and the Curie temperature, and use of the oxide magnetic material in a magneto-optical recording medium. Was made possible. Here, the relationship between the composition and the Curie temperature of a typical ferromagnetic oxide used in the present invention will be described as shown in FIG. When the ferromagnetic oxide of the above chemical formula 1 has a Curie temperature of 500 ° C. when x = 0, it is clear that when the Fe atom is replaced with a specific metal, that is, the Curie temperature decreases according to the amount of the x component. In addition, even with an oxide magnetic material having a low Curie temperature, the magneto-optical effect sufficiently maintains the rotation performance. For _{example, CoM 0. 9 Fe 1.} 1 in O ₄ thickness 2
In the case of 000Å, the Kerr rotation angle (2θ
k) is about 1 °. The magnetic thin layer of the present invention is obtained by forming a ferromagnetic oxide having a low Curie temperature as described above on a transparent substrate by a sputtering method, a vapor deposition method, an ion plating method or the like.

Further, a feature of the present invention is to provide a transparent dielectric layer on the thin oxide magnetic layer in order to obtain a sufficient Kerr rotation angle. Here, the relationship between the film structure and the Kerr rotation angle will be described with reference to the drawings. FIGS. 3A and 3B show a conventional structure, where FIG. 3A shows a (glass) substrate 1.
An example in which the magnetic layer 2 (film thickness 4000Å) is provided on the top is shown, and (B) shows an example in which the magnetic layer 2 (film thickness 200Å) and the reflection layer 4 are sequentially provided on the substrate 1. As shown in FIG. 1, a comparison is made with that of the present invention (hereinafter abbreviated as (C)) in which a transparent dielectric layer 3 is provided on a magnetic layer 2 (film thickness 300Å).
In each of (A), (B) and (C), the Kerr rotation angle was measured from the substrate side. FIG. 4 shows the relationship between the structure of the film and the Kerr rotation angle.
In the case where the magnetic layer is thick, is the Kerr rotation angle only for reflection from the medium surface, and in (B), the rotation angle is increased because the magnetic layer is a thin film that can transmit light and the light is reflected by the reflection layer. Further, (C) is a structure in which a dielectric layer is further provided on (B), and the reflected light becomes small due to the interaction with the magnetic layer, and as a result, the rotation angle increases. As described above, in the present invention, the Kerr rotation angle is increased by providing the transparent dielectric layer.

[0008]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples illustrated herein.

Example 1 A fine powder of the following general formula 2 was sintered to have a diameter of 5 cm and a thickness of 1
A mm target was created. Next, on the glass substrate, the total gas pressure is 60 mTorr and the oxygen partial pressure is 0.3 mTorr.
At a film production speed of 25Å / min, a magnetic thin layer having a film thickness of 500Å was obtained by sputtering. On this magnetic thin layer,
SiO ₂ transparent dielectric layer with a film thickness of 2000 to 3000Å, Cu reflective layer with a film thickness of 3000Å and Si with a film thickness of 2000Å
The O ₂ antioxidant layer was sequentially deposited by sputtering.

[Chemical 2] (However, 0.75 ≦ x ≦ 1.3)

The recording medium prepared in this manner is magnetized in one direction, and then a magnetic field of 0.3 KOe to 1 KOe opposite to the direction of magnetization is applied to this part while laser output 1 is applied.
The magnetization was reversed by irradiating an 800 nm semiconductor laser with 0 mW and a medium surface of about 5 mW for 5 μs pulse. The medium surface was irradiated with a laser for about 0.5 to 2 mW, and the Kerr rotation angle of the light returning from the medium surface was measured. 2θk is 1.3 ~
It was 2.4 °. 2 when the composition is x = 0.9 to 1.0
θk is the peak value.

As shown in Table 1, the magnetic thin layer of this recording medium did not deteriorate in magnetic properties even after being stored at 100 ° C. for 7 days. On the other hand, the amorphous magnetic alloy film was oxidized and crystallized, and the magnetic properties were significantly deteriorated.

[0012]

[Table 1]

[Brief description of drawings]

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

FIG. 2 is a graph showing the relationship between the composition of ferromagnetic oxide and the Curie temperature.

FIG. 3 is a sectional view showing a configuration example of a conventional magneto-optical recording medium.

FIG. 4 is a graph showing the relationship between the configuration of a magneto-optical recording medium and the Kerr rotation angle.

[Explanation of symbols]

 1 Transparent Substrate 2 Magnetic Thin Layer 3 Transparent Dielectric Layer 4 Reflective Layer 5 Antioxidant Layer

Claims (1)

[Claims] 1. A magnetic thin layer made of a ferromagnetic oxide represented by the following general formula 1 is provided on a transparent substrate, and a transparent dielectric layer and a reflective layer are sequentially provided on the magnetic thin layer. A magneto-optical recording medium characterized by: [Chemical 1]