JPH0782943B2 - Amorphous magneto-optical layer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magneto-optical recording medium used for a hard disk, a floppy disk, a document file, etc., and particularly to an amorphous magneto-optical layer excellent in magneto-optical properties. It is related.

2. Description of the Related Art In recent years, various studies have been conducted on a high-density recording magneto-optical recording medium that performs magnetic recording with a semiconductor laser beam. In particular, in order to be used for high density recording, it is necessary that the magnetic film has an easy axis of magnetization in the direction perpendicular to the film surface. Conventionally, as magnetic films used in these magneto-optical recording media, those using amorphous alloys such as Gd-Co, Gd-Fe, Tb-Fe, Gd-Tb-Fe, and Tb-Dy-Fe are known. However, the magneto-optical recording medium using these amorphous alloy magnetic materials has a high recording sensitivity and a high speed (frequency, several MHz) by the semiconductor laser light.
However, there is a problem that the magneto-optical effect is not sufficiently satisfied, although there is an advantage that the recording can be performed in (1). Therefore, the applicant of the present application has already proposed to increase the Kerr rotation angle θk and improve the magneto-optical effect by using a quaternary amorphous magnetic film made of Tb-Dy-Fe-Co. In order to manufacture a magneto-optical recording medium using such a magnetic film, generally, the magnetic material is attached onto a substrate such as a glass plate by a method such as vacuum deposition and sputtering to form the magnetic film. Recording and reproduction on the thus obtained magneto-optical recording medium are performed as follows. That is, recording is performed by irradiating and heating the magnetic film with a laser beam modulated by an information signal by utilizing the rapid change characteristic of the coercive force corresponding to the temperature change near the Curie temperature or the compensation temperature of the magnetic film. This is done by reversing the direction of. Further, the reproduction is performed by reading the Kerr rotation angle of the magnetic film thus recorded in reverse. The Kerr effect is used for recording and reproducing an information signal when light is difficult to pass through as in such an amorphous alloy magnetic body. The Kerr effect is the rotation phenomenon of the plane of polarization when light is reflected on the surface of a magnetic material, and is a) polar effect, b) vertical (longitudi).
nal) effect and c) transverse effect. Especially, in the case of an amorphous alloy magnetic body, the pole effect of a is used, and the Kerr rotation angle θk is used to perform reproduction. Therefore, if the Kerr rotation angle θk is increased as much as possible, the magneto-optical effect is increased and the reproduction characteristic is improved.

However, the Kerr rotation angle θk of the quaternary amorphous alloy magnetic film made of Tb-Dy-Fe-Co is 0.29 due to its composition.
It is about deg or about 0.30 deg, and there is a demand for improvement of the optical reproduction characteristic.

OBJECT The object of the present invention is to provide an amorphous magneto-optical layer having an increased Kerr rotation angle θk in an amorphous alloy magnetic film having an easy axis of magnetization in a direction perpendicular to the film surface, thereby improving the light reproduction characteristics. To provide.

Structure The present invention is a Tb-Dy having an easy axis of magnetization in a direction perpendicular to the film surface.
It is an amorphous magneto-optical layer composed of a quinary amorphous alloy magnetic film of -Fe-Co-Cu.

Further, the amorphous magneto-optical layer of the present invention is required to exhibit perpendicular magnetic anisotropy and have a high coercive force Hc. Therefore, the composition formula of the magnetic material of the present invention is represented by {(Tb _1-X Dy _X ). _When expressed as _Z (Fe _1-Y CO _Y ) _1-Z } _1-A Cu _A , 0 <X <1,0.01 ≦ Y ≦ 0.5,0.1 ≦ Z ≦
It is desirable that 0.5, 0.001 ≦ A ≦ 0.1.

The amorphous magneto-optical layer of the present invention is formed on a suitable support by a method such as vacuum deposition, sputtering, ion plating and the like to have a film thickness of about 0.01 to 1 μm. The magnetic film thus obtained is one that is perpendicularly magnetized to the film surface.

When forming a magnetic thin film by sputtering,
Each material component is used individually or in combination to form a target, and the magnetic material composition is controlled by the area ratio of the target surface.

As the support, glass, plastic, ceramic or the like can be used.

When the magneto-optical layer of the present invention is used in a magneto-optical recording medium, it may be used alone or in combination with other films. For example, an acrylic resin, a polyurethane resin, a polycarbonate resin, a polyethersulfone resin, a polyamide resin, an epoxy resin, TiN, Si ₃ N ₄ , Al as a protective film on the upper surface or the upper and lower surfaces of the Tb-Dy-Fe-Co-Cu film.
Apply N, CrN, TaN, SiO ₂ , SiO, etc. to the film thickness of 0.1 to 10 μm by the coating method for resin and vacuum evaporation, sputtering, reactive sputtering, CVD etc. for other materials. May be.

Effect When the amorphous magneto-optical layer made of Tb-Dy-Fe-Co-Cu thus obtained is heated by irradiation with laser light modulated by an information signal, the Kerr rotation angle of the amorphous magneto-optical layer θ
Since k is larger than that of the conventional one, the optical reproduction characteristic when reproducing this by the Kerr effect is improved, the S / N ratio is improved, the number of recording dots is increased, and high-density recording / reproduction is possible. A recording medium will be obtained.

Examples will be shown below.

Example Tb-on a slide glass support by the sputtering method
An amorphous magneto-optical layer made of Dy-Fe-Co-Cu was formed.
The target was formed by using a composite method by placing an alloy chip of Tb _0.5 Dy _0.5 and a Cu chip on a Fe _0.9 Co _0.1 alloy disk, and forming a film while controlling each composition ratio by the area ratio of the target surface.

The conditions for forming the amorphous magneto-optical layer are shown in the following table.

Each amorphous magneto-optical layer has a large coercive force Hc near the compensation composition.
In the composition of (Fe _0.9 Co _0.1 ) _0.79 (Tb _0.5 Dy _0.5 ) _0.21 , (T
b _0.5 Dy _0.5 ) partly replaced by Cu, that is, (Fe _0.9 Co
_0.1 ) _0.79 {(Tb _0.5 Dy _0.5 ) _1-X Cu _X } _0.21 was prepared.

The film was evaluated by irradiating a He-Ne laser (λ = 633 nm) from the substrate side and using the Kerr effect, the Kerr rotation angle θk and the coercive force.
I asked for Hc.

The results are shown in FIG. From these figures, it can be seen that by increasing X, that is, the amount of Cu, Hc decreases but θk increases. In this embodiment, (Tb
_{Since 0.5} Dy _0.5 ) was partially replaced by Cu, increasing the amount of Cu reduced the amount of Tb contributing to anisotropy and decreasing Hc, so the amount of Cu could not be increased so much. _0.9 C
If the ratio of (O _0.1 ) and (Tb _0.5 Dy _0.5 ) is kept constant and the amount of Cu is increased, the decrease in Hc can be suppressed and the amount of Cu can be increased.

Here, Tb-Dy-Fe-Co- in the case where the Kerr rotation angle is maximized in the amorphous magneto-optical layer in each of the examples.
The Cu film composition, the Kerr rotation angle θk, and the increase value of θk compared with the case where Cu is not contained are shown.

[Brief description of drawings]

FIG. 1 is a change diagram of θk and Hc when the amount of Cu in each amorphous magneto-optical layer is changed in the examples.

Claims (1)

[Claims] 1. A Tb having an easy axis of magnetization in a direction perpendicular to a film surface.
An amorphous magneto-optical layer formed of a quinary amorphous alloy magnetic film of -Dy-Fe-Co-Cu.