JPH06274951A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a MSR medium which can be formed in films with small number of targets. CONSTITUTION:This magneto-optical recording medium (MSR medium) consists of a transparent substrate, dielectric material layer, and an exchange coupling multilayer film consisting of at least a reproducing layer, intermediate layer and recording holding layer. Recorded signals in the medium are read by changing the magnetized state of the reproducing layer. Among the films of the exchange coupling multilayer film, the layer having the lower Curie temp. consists of (Tb, Fe, Co)1-xSix (x<=0.18). Thereby, the number of targets necessary for formation of the multilayer film can be decreased, and by only controlling the Si density, the margin for the Curie temp. of the intermediate layer can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable magneto-optical recording medium for reading a recording signal while changing the magnetization state of a reproducing layer.

[0002]

2. Description of the Related Art A magneto-optical recording medium is a rewritable optical recording medium, and is excellent in repeated erasing / writing durability and erasing ratio as compared with a phase change type optical recording medium and is a portable large capacity recording medium. Attention has been paid.

The magneto-optical recording medium employs a recording / reproducing method in which a recording bit is formed by local heating by laser light irradiation, and the recording bit is read by the curling effect. The recording bit interval can be made considerably smaller than the laser spot diameter by adjusting the laser light irradiation power, the recording magnetic field strength, etc., but the reading is the laser wavelength during reproduction. , It is limited by the aperture ratio of the lens.

As an attempt to improve the reading beyond the recording density determined by such a restriction at the time of reproduction, a method of reading a recording signal while at least having a reproduction layer and a recording holding layer and changing the magnetization state of the reproduction layer. Is MSR (Magn
physically induced Super Re
In recent years, it has been drawing attention as a solution. For example, extinction type MSR or FAD (Front Ap)
A method called "entry detection" is disclosed in Japanese Laid-Open Patent Publication No. 1-143041 and Japanese Laid-Open Patent Publication No. 1-14304.
This is a technique disclosed in Japanese Patent Laid-Open No. 2 (1994), in which the reproduction resolution is improved by reproducing the recorded bits while enlarging or reducing the recorded bits. In this method, the recording magnetic layer is a reproducing layer, an intermediate layer,
A beam spot is formed by using an exchange-coupling multilayer film composed of a recording holding layer, and utilizing the temperature rise due to the irradiation of reproducing light, and always orienting the reproducing layer in the direction of the reproducing magnetic field in a high temperature region above the Curie temperature of the intermediate layer. It is a so-called mask partly, which reduces the intersymbol interference at the time of reproduction and makes it possible to reproduce a signal having a period less than the diffraction limit of light.

In addition, a raised MSR or RAD
(Rear Aperture Detection)
A method called "a" is disclosed in Japanese Patent Laid-Open No. 3-93058, and the recording magnetic layer is an exchange coupling multilayer film including a reproducing layer, a reproducing auxiliary layer, an intermediate layer and a recording holding layer, and a reproducing layer is formed by an initialization magnet before reproducing. Is a technique for improving the reproduction resolution by reproducing the recording bits of the recording holding layer while transferring the recording bits of the recording holding layer to the reproducing layer after aligning the magnetization directions.

The lowest Curie temperature in each layer of the multilayer film is the intermediate layer in the FAD system and the regeneration assisting layer in the RAD system. These materials are disclosed, for example, in JP-A-1-
No. 143041 discloses TbFe, TbFeCo, Dy.
FeCo, TbFe in JP-A-4-255937
CoAl and the like are shown.

[0007]

These complicated multi-layered films are usually formed by a sputtering method, but even if they are formed by an alloy target, it is necessary to have as many targets as the number of films.
Further, in order to determine the optimum combination of each layer, it is necessary to carry out simultaneous sputtering, and the number of targets is further increased.

[0008] The problem to be solved by the present invention is to make it possible to obtain an MSR medium capable of forming a film with as few targets as possible.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention pay attention to Si necessary for dielectric film formation and reduce the number of targets by using TbFeCoSi as an intermediate layer or a reproduction assisting layer. It was made possible, and the present invention was completed.

That is, according to the present invention, an exchange-coupling multilayer film is formed on a transparent substrate through a dielectric layer, at least a reproducing layer, a recording holding layer, and an intermediate layer provided between the reproducing layer and the recording holding layer. , In a magneto-optical recording medium that reads a recording signal while changing the magnetization state of the reproducing layer, a layer that should have the lowest Curie temperature in the film forming the exchange coupling multilayer film (hereinafter,
The specific layer) is at least (Tb, Fe) _1-x S
The present invention relates to a magneto-optical recording medium characterized by comprising an element represented by i _x (where x ≦ 0.18).

In the present invention, the specific layer corresponds to the intermediate layer in the FAD system and the reproduction auxiliary layer in the RAD system. When Si is contained in TbFeCo as the specific layer, the Curie temperature is lowered by increasing the Si concentration x, and when Si is not contained at x = 0.18 (TbFeCo
It is about 150 ° C lower than that of Co only). Even if x> 0.18, the Curie temperature is further lowered, but the perpendicular magnetic anisotropy is significantly lowered, and good MSR characteristics cannot be obtained.

[0012] Curie - temperature, the specific layer from the relationship between the perpendicular magnetic _{anisotropy, (Tb y (Fe 1-} z Co z)) 1-x Si x ( where, x ≦ 0.18,0.14 ≦ y ≦ 0.30, 0 ≦
z ≦ 0.20) is preferable.

Further, in the specific layer of the magneto-optical recording medium of the present invention, Cr, Ti, Ta, etc. are added in an amount of 0.1 to 0.1% in order to improve durability.
It may be contained at 15 atm%.

In the method of manufacturing the magneto-optical recording medium of the present invention, it is possible to form a film by using Gd, Tb, FeCo, and Si as targets and combining them by any desired simultaneous sputtering. More specifically, in the case of FAD, the dielectric layer can be formed of silicon nitride, the reproducing layer can be formed of GdFeCo, the intermediate layer can be formed of TbFeCoSi, and the recording holding layer can be formed of TbFeCo. In the case of RAD, the dielectric layer can be formed of silicon nitride, The reproducing layer is GdFeCo, and the reproducing auxiliary layer is TbFeCo.
Si, the intermediate layer is GdFeCo or GdFeCoSi,
The recording holding layer can be formed as TbFeCo. Conventionally, a method of adding Al to the intermediate layer or changing the composition ratio of Co and Fe between the recording holding layer and the intermediate layer has been taken.
The number of sputter chambers had to be increased by adding a get.

In the magneto-optical recording medium of the present invention, when the recording holding layer is made of TbFeCo and the specific layer is made of TbFeCoSi, the composition ratios of Co and Fe are the same, so that the Curie temperatures of the specific layer and the recording holding layer are the same. In order to obtain a remarkable MSR effect due to the difference, the Si concentration x is preferably 0.07 <x.

[0016]

【Example】

Example 1 An FAD type magneto-optical recording medium as shown in FIG. 1 was manufactured by using each target of Gd, Tb, Fe _0.87 Co _0.13 and Si individually or as a combination of co-sputtering. A dielectric layer 2 made of silicon nitride (film thickness: 800 angstrom) is formed on a polycarbonate substrate 1.
Reproducing layer 3 made of GdFeCo (film thickness: 300 Å, magnetization: 20 emu / cc (room temperature), Curie temperature: 340 ° C.), intermediate layer 4 made of TbFeCoSi
(Film thickness: 100 Å, compensation composition, Curie temperature: 80 to 200 ° C.), TbFeCo recording holding layer 5 (film thickness: 400 Å, coercive force:> 1)
2 kOe, Curie temperature: 260 ° C.), and a silicon nitride layer 6 (film thickness: 800 Å) was further formed.

In order to change the Curie temperature of the intermediate layer at 80 to 200 ° C., the Si concentration in TbFeCoSi is x =
The value varied from 0.08 to 0.19. The Tb concentration was also changed at the same time to obtain a compensation composition. FIG. 2 shows the Curie temperature with respect to the Si concentration x and the Tb concentration y of the compensation composition.

Next, this magneto-optical recording medium was set in a recording / reproducing apparatus, and while being rotated at a linear velocity of 5.5 m / sec, a laser beam having a wavelength of 780 nm and a duty ratio of 33% were used.
5.4m while modulating at 7.1MHz on the tee
Recording was performed with a W laser power. The bias magnetic field during recording was 250 Oe.

A bias magnetic field of 300 Oe (H
The laser power was adjusted to 1 to 2.5 mW and regenerated while applying r), and the maximum C / N value obtained is shown in FIG. 3 in comparison with the Si concentration. 40d when Si concentration is 0.18 or less
Good C / N of B or more, especially 45d when x <0.15
An even better C / N of B or higher was obtained.

[0020]

In the magneto-optical recording medium of the present invention, the specific layer of the MSR medium is composed of at least Tb, Fe and Si, so that the Si target and the target required for the dielectric film formation are made common. It is possible to reduce the number of targets necessary for forming a multilayer film. Further, since the perpendicular magnetic anisotropy is gradually decreased by adding Si, the range of selection of the Curie temperature of the specific layer can be set to about 150 ° C. only by adjusting the Si concentration, and the MSR medium considering the margin can be obtained. Design is possible.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship with a Curie temperature or a compensation composition when the Si concentration of a TbFeCoSi intermediate layer is changed.

FIG. 3 is a diagram showing a relationship between Si concentration and C / N when FAD reproduction is performed on the magneto-optical recording medium of Example 1.

Claims (1)

[Claims] 1. A reproducing layer is formed on a transparent substrate by forming at least a reproducing layer, a recording holding layer and an intermediate layer between the reproducing layer and the recording holding layer with a dielectric layer interposed therebetween. In a magneto-optical recording medium for reading out a recording signal while changing the magnetization state of, the layer that should have the lowest Curie temperature in the film forming the exchange-coupling multilayer film is at least (T
b, Fe) _1-x Si _x (provided that x ≦ 0.18), a magneto-optical recording medium.