JPS6280844A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the recording characteristic of a photomagnetic recording medium by laminating a reading out layer consisting of a vertical magnetically anisotropic film composed of cobalt ferrite and writing layer consisting of a vertical magnetically anisotropic film composed of a rare earth-transition metal amorphous alloy on a substrate. CONSTITUTION:The writing layer 15 consisting of the rare earth-transition metal amorphous alloy and having the vertical magnetic anisotropy is low in Tc and therefore, Hc thereof decreases and a magnetic moment inverts to the direction of an external magnetic field when a laser beam 121 is irradiated on the photomagnetic recording medium from the substrate 11 side. The reading out layer 13 consisting of the vertical magnetically anisotropic film composed of Co ferrite is small in Hc and is, therefore, subjected to magnetic transfer according to such inversion. The magnetic moment in the part corresponding to the inverted part of the layer 15 is then inverted and the recording of information is executed. The reproduction of the information is executed by irradiating laser beam 21 on the layer 13 from the surface and reading out the magnitude of the Faraday rotating angle of the light reflected from the layer 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording medium used for document files, floppy disks, hard disks, and the like.

In recent years, magneto-optical recording media have attracted attention, in which information is recorded by writing magnetic domains on a magnetic thin film using the thermal effect of light, and information is read out using the magneto-optic effect. .

Traditionally, there was a lot of sales, but there was a lot of trouble.
Thin films made of rare earth-transition metal-based amorphous magnetic materials such as Tb-Fa gold alloy are known (Japanese Patent Publication No. 57-2
0691). Recording of information on such a magneto-optical recording medium is carried out using the characteristics of a sudden change in coercive force at the Curie temperature or compensation temperature of a magnetic material.
This is done by irradiating a perpendicularly magnetized magnetic thin film with a laser beam modulated by a value signal, heating it, and reversing the direction of magnetization. Further, reproduction is performed by utilizing the difference in the magneto-optical effect of the magnetic film subjected to inversion recording.

A rare earth-transition metal amorphous magnetic thin film exhibits perpendicular magnetic anisotropy and has a large coercive force He, making it suitable as a memory material, but its magneto-optic effect is small and its reproduction characteristics are insufficient.

DISCLOSURE OF THE INVENTION An object of the present invention is to improve the reproduction characteristics of a magneto-optical recording medium using a rare earth-transition metal based amorphous magnetic material.

The magneto-optical recording medium of the present invention has a readout layer made of a cobalt ferrite perpendicular magnetic anisotropy film and a write layer made of a perpendicular magnetic anisotropy film made of a rare earth-transition metal based amorphous alloy on a substrate. It is characterized by

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of the structure of the magneto-optical recording medium of the present invention, in which a reading layer 13 and a writing layer 1 are provided on a substrate 11.
5 are sequentially stacked.

The readout layer 13 is made of a perpendicular magnetic anisotropic film of cobalt ferrite. Cobalt ferrite is typically Cox
It is represented by Fe3−Xo4 (o, s≦X≦2), and
Some of the Fe atoms are Al and Ga.

It can also be replaced with Cr or the like. The readout layer 13 is G
A perpendicular magnetic anisotropic film of o-ferrite can be formed by a vapor deposition method, a sputtering method, an ion blating method, a plating method, etc., and the film thickness is suitably about 1,000 to 10,000.

The writing layer 15 is made of a perpendicularly magnetized film of an amorphous rare earth-transition metal alloy. Rare earth metals include Tb (terbium), Dy (dysprosium), Gd (gadolinium), Sm (samarium), Ho (holmium), and transition metals include Fe (iron) and C.
o (cobalt), Cu (copper), Ni (nickel), C
Examples include r (chromium). Specific examples of rare earth-transition metal-based amorphous alloys include Tb-Fe, Dy-
Fe, Gd-Tb-Fe, Tb-Dy-Fe.

Tb-Fe-Co, Gd-Tb-Fe-Go.

Examples include Tb-Fe-Cu. The appropriate thickness of the writing layer is about 500 to 5,000 layers, and it can be formed by a vapor deposition method, a sputtering method, an ion blasting method, or the like.

As the substrate 11, a non-magnetic and transparent material such as glass, plastic, ceramic, etc. is used.

FIG. 2 shows another configuration example of the present invention, in which a protective film 17 is further provided on the writing layer 15 of the optical recording medium shown in FIG. The protective film 17 is mainly used to prevent the amorphous alloy magnetic material from being oxidized and corroded by oxygen or water, and is made of Si3N4. AIN, Sin, S
It is formed from in, etc. The thickness of the protective film is 500~5
Approximately 1,000 people are suitable and can be formed by a vapor deposition method, a sputtering method, an ion blating method, or the like.

FIG. 3 shows still another configuration example of the present invention, in which a writing layer 15 made of a perpendicular magnetic anisotropic magnetic film of a rare earth-transition metal based amorphous alloy and a perpendicular magnetic anisotropic magnetic film of cobalt ferrite are formed on a substrate 11. Readout layers 13 made of films are sequentially laminated. Further, a protective film or a protective plate made of glass, plastic, ceramic, etc. may be provided on the readout layer 13. In this configuration example,
As the substrate 11, in addition to a transparent substrate, an opaque substrate such as ceramic or metal can also be used.

*、￥8 days/7'1 major! Tozen lit tairiichi phantom 1. A rare earth-transition metal magnetic film is used as the write layer, and a Co ferrite film is used as the read layer. That is, the characteristics of the rare earth-transition metal magnetic film having a low Curie temperature Tc and a large coercive force Hc are utilized to increase recording sensitivity and memory stability, while the Co ferrite film has a large magneto-optical effect.
By utilizing the characteristic of a small coercive force He, the reproduction sensitivity can be increased and the reproduction S/N ratio can be improved.

Recording and reproduction on the magneto-optical recording medium of the present invention can be performed, for example, as follows. When writing information, please
As shown in the figure, a laser beam 21 is applied to the magneto-optical recording medium.
When irradiated with , the writing layer 15 made of a rare earth-transition metal magnetic film has a low Tc, so the Hc becomes small, and the magnetic moment is reversed in the direction of the external magnetic field 27. Along with this, the reading layer 13 made of CO ferrite is magnetically transferred because of its small Hc-, and only the portion corresponding to the inverted portion of the writing layer 15 has its magnetic moment turned in half, and information is recorded. To play the information, click Go as indicated by the arrow.
Laser beam 21 is applied to readout layer 13 made of ferrite.
This can be done by reading out the magnitude of the Faraday rotation angle of the reflected light from the writing layer 15.

Further, a reflective layer can be further provided on the back side of the writing layer 15. In the magneto-optical recording medium of the type shown in FIG. 3, recording and reproduction can be similarly performed by irradiating the laser beam 21 from the readout layer 13 side as indicated by the arrow.

According to the present invention, by laminating a CO ferrite film with a large magneto-optical effect and a rare earth-transition metal based amorphous magnetic film, a light beam with high recording sensitivity and a good reproduction S/N ratio can be produced. A magnetic recording medium can be realized.

Example 1 A readout layer having a thickness of 2,000 mm and a composition of CoFe of 20° was formed on a quartz glass substrate by RF sputtering under the following conditions.

Residual gas pressure: 8 XIO"" Torro2 gas pressure:
5 X 10-'Torr (Ar+02) gas pressure: 2X
10'''' Torr discharge electric crab 400W Sputtering time: 120m1n Substrate temperature: 450°C Next, the substrate was water-cooled and a writing layer (with a composition of T b 02F e o, a) was formed by RF sputtering under the following conditions. A film thickness of 1,000 layers was formed.

Residual gas pressure: 8 Xl0-7TorrAr gas pressure: 2
X10'''' Torr discharge electric crab 400W Sputtering time: 8ml Further, a SiN protective film (film thickness 1000mm) was provided thereon by RF sputtering. At this time.

The writing layer consisting of Tb, , Fe, , Hc = 2.3
KOe, T c = 120 °C, and COF
The readout layer consisting of e204 is θF = 1.5deg
/μm, making it possible to increase recording sensitivity and reproduction S/N ratio.

Example 2 Instead of the T b 11,2 F e a,s film as the writing layer, (T b a,s D 3' a,s )0.
An optical recording medium was prepared in the same manner as in Example 1 except that a film having a composition of 21 F e o, ts was provided.

In this recording medium, the writing layer made of a Tb-Dy-Fe film has Hc = 1.8KOe and Tc = 100°C,
The readout layer made of CO ferrite is θ, = 1.5deg.
/μm, and both recording sensitivity and reproduction S/N ratio were large.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are cross-sectional views showing examples of the structure of each layer of the magneto-optical recording medium of the present invention. FIG. 4 is an explanatory diagram of the recording and reproducing method of the magneto-optical recording medium of the present invention. 11... Substrate 13... Readout layer 15.
...Writing layer 17...Protective film 21...Laser light 23...External magnetic field 12 evil rods 41

Claims (1)

[Claims] 1. A magneto-optical recording medium characterized in that a read layer made of a perpendicular magnetic anisotropic film of cobalt ferrite and a write layer made of a perpendicular magnetic anisotropic film of a rare earth-transition metal based amorphous alloy are laminated on a substrate. .