JP2921794B2 - Magneto-optical disk - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk, and more particularly to a magneto-optical disk having high recording / reproducing characteristics while suppressing writing laser power.

[Conventional technology]

Magneto-optical disks that record, reproduce and erase information by irradiating a magneto-optical recording medium layer with a laser beam can record rewritable information at high density, and are expected to be widely used in various fields. ing.

As a structure of this type of magneto-optical disk, a magneto-optical recording medium described below is protected as a first layer on a transparent substrate conventionally formed of a transparent polymer material such as glass, polycarbonate, acrylic, epoxy, and polymethylpentene. Dielectric film, a rare earth metal such as Gd, Tb, Dy, Ho, etc. and Fe,
Magneto-optical recording media films with a film thickness of 500 mm or less, such as amorphous thin films made of alloys with transition metals such as Co and Ni,
As the third layer, the magneto-optical recording medium is protected, and the read-out light of the information transmitted through the film is multiply reflected (interfered) between the film and a metal film described later to make the apparent Faraday rotation angle of the read-out reflected light. A dielectric film for enhancing the reproduction C / N ratio by increasing the enhancement (enhancement effect), and a metal film formed as a fourth layer (Japanese Patent Application Laid-Open No. 60-129951,
No. 60-209947).

[Problems to be solved by the invention]

However, in the magneto-optical disk having this structure, the extinction ratio is reduced in the detection system, and the detection signal intensity is apt to decrease. Therefore, at present, the allowable range of the film thickness of the magneto-optical recording medium film is narrow.

An object of the present invention is to solve this problem and to provide a magneto-optical disk in which the allowable range of the thickness of the magneto-optical recording medium film is as wide as possible.

[Means for solving the problem]

The present invention achieves the above object by forming a dielectric film as a first layer and oxygen as a second layer on a transparent substrate.
TbFeCoCr-based or T with a thickness of 500 mm or less containing 12 atomic%
This is a magneto-optical disk comprising a bFeCo-based magneto-optical recording medium film, a dielectric film as a third layer, and a metal film as a fourth layer.

[Action]

In the present invention, the magneto-optical recording medium film as the second layer must contain 8 to 12 atomic% of oxygen. This oxygen reduces the absorption coefficient of the magneto-optical recording medium film and makes it difficult for the reflected linearly polarized light to be elliptical. If this amount is less than 6 atomic%, the above-mentioned effect of oxygen is diluted, while if it exceeds 12 atomic%, the coercive force of the magneto-optical recording medium film decreases, and
Long-term weather resistance decreases.

The film thickness of this magneto-optical recording medium film needs to be 500 ° or less in order to effectively use the Faraday effect.
Å or more is preferable.

〔Example〕

Example 1 A silicon nitride having a refractive index of 2.0 was formed as a first layer dielectric on a 1.2 mm thick transparent substrate with a groove made of polycarbonate by a high-frequency magnetron sputtering method at 900 mm, and a film was formed thereon by a DC magnetron sputtering method. 200 ~ 600Å (Tb _0.16
Fe _0.72 Co _0.10 Cr _0.02 ) _1-x O _x (x = 0 to 0.13) composition magneto-optical recording medium is formed, and silicon nitride is formed as the third layer in the same manner as the first layer by 300 silicon nitride. Then, Al was formed as a reflective layer to a thickness of 400 °.

The phase difference, figure of merit, coercive force and squareness ratio {Mr (saturation magnetization / Ms (residual magnetization)}} of the magneto-optical disk manufactured in this manner measured using a vibrating magnetometer are shown in FIGS.
Shown in the figure.

Example 2 Film thickness 300 mm, (Tb _0.15 Fe _0.68 Co _0.09 O _0.08 ) _1-y Cr
_A magneto-optical disk was manufactured in the same manner as in Example 1 except that a magneto-optical recording medium having a composition of _y (where y: 0 to 0.07) was formed.

FIGS. 4 and 5 show the coercive force, squareness ratio, and composition distribution in the depth direction of this magneto-optical disk measured by an oscillating magnetometer by Auger electron spectroscopy.

Example 3 (Tb _0.17 Fe _0.72 Co _0.11 ) _1-x O _x (where x: 0.04 to 0.1
3) A magneto-optical disk was produced in the same manner as in Example 1, except that a magneto-optical recording medium having the composition 3) was formed.

FIGS. 6 and 7 show the phase difference and the figure of merit of the magneto-optical disk.

According to FIGS. 1 and 6, when oxygen is added to the magneto-optical recording medium film, the phase difference is greatly reduced, and
It can be seen that 00 ° is 3 ° or less. 2 and 7 that addition of oxygen to the magneto-optical recording medium film greatly widens the range of film thickness at which the figure of merit is high.

FIG. 3 shows that when the amount of oxygen added to the magneto-optical recording medium film exceeds 12 atomic%, the coercive force and the squareness decrease.

FIG. 4 shows that when the component composition of the magneto-optical recording medium film is (Tb _0.15 Fe _0.68 Co _0.09 O _0.08 ) _1-y Cr _y , y is preferably 6 or less.

Further, FIG. 5 shows that oxygen is reliably added to the magneto-optical recording medium film.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a magneto-optical disk capable of producing a magneto-optical recording medium having a significantly large allowable range of film thickness, thereby producing a high yield, and having a large figure of merit.

[Brief description of the drawings]

FIGS. 1 and 6 show the relationship between the phase difference of the magneto-optical disk and the thickness of the magneto-optical recording medium film, and FIGS. 2 and 7 show the figure of merit of the magneto-optical disk and the magneto-optical recording medium film. FIG. 3 shows the relationship between the coercive force and the squareness ratio of the magneto-optical disk and the oxygen content in the magneto-optical recording medium film, and FIG. 4 shows the coercive force of the magneto-optical disk. And the relationship between the squareness ratio and the Cr content in the magneto-optical recording medium film.
The figure shows the composition distribution in the depth direction of the magneto-optical disk by Auger electron spectroscopy.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-166509 (JP, A) JP-A-4-67334 (JP, A) JP-A-63-32748 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G11B 11/10 501

Claims (1)

(57) [Claims] 1. A TbFeCoCr-based or TbFeCo-based magneto-optical recording medium film having a film thickness of 500 ° or less containing a dielectric film as a first layer and containing 8 to 12 atomic% of oxygen as a second layer on a transparent substrate.
A magneto-optical disk comprising a dielectric film as a layer and a metal film as a fourth layer.