JPS63282945A - Thermomagneto-optical recording medium - Google Patents

Abstract

PURPOSE:To make effective use of the largest angle of Kerr rotation and to enable efficient taking out of light reproduction output by laminating respectively specific ternary amorphous magnetic alloy layers on a substrate. CONSTITUTION:The ternary amorphous alloy layers satisfying formula I in which (x) increases and (y) decreases successively in a 0.15<=x<=0.35, 0<y<0.5 range are so laminated successively on the substrate that the axis of easy magnetization is perpendicular to the film plane. Then, the quantity of Tb decreases and the quantity of Co increases on the light incident surface and the film having the largest angle of Kerr rotation exists thereon. This film is effectively utilized to obtain the reproduction output of a high signal level and low noise level. The light reproduction output is thus efficiently taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording medium used for, for example, magneto-optical memory, magnetic recording, display elements, etc.

[Conventional technology]

Conventionally, as photothermal magnetic recording media, MnB1, Mn
Polycrystalline thin film such as CuB1, GdCo, GdFe
, TbFe%DyFe.

Amorphous thin films such as GdTbFe and TbDyFe, G
Single crystal thin films such as IG are known. Among these thin films, the film-forming ability of producing a large-area thin film at a temperature near room temperature, the writing efficiency of writing signals with a small amount of photothermal energy, and the ability to read the written signals with a good signal-to-noise ratio are important. Recently, the above-mentioned amorphous thin film is considered to be superior in terms of readout efficiency and the like.

However, various drawbacks have been pointed out even in these amorphous thin films. For example, GdFe has a small coercive force and recorded information is unstable.

Furthermore, since GdFe and GdCo perform writing using magnetic compensation points), there is a problem in that the film composition must be strictly controlled during film formation in order to make the writing efficiency uniform. In addition, TbFe, DyFe,
Since TbDyF e writes a single point, it is not necessary to control the film composition so severely, but one point of + Yuri is 10
Since the temperature is as low as around 0.degree. C., there is a problem in that high-power light cannot be used when reading signals. If the temperature is lower, the writing efficiency will improve, but the written signal will be disturbed by the ambient temperature or read light. Therefore, the higher the temperature of the cow lily is, the better, as long as it is writable, and considering practical conditions, around 200°C is desirable.

Further, the readout S/N ratio by reflected light is proportional to Jπθk, where the reflectance and R Kerr rotation angle are θ. Therefore,
In order to read with a good signal-to-noise ratio, the Kerr rotation angle may be increased. Therefore, CO-added materials such as TbFeCo and DyFeCo are used, for example, in JP-A-58-7374.
It is reported in Publication No. 6.

[Problem that the invention seeks to solve]

The TbFaCo film is preferably used at a temperature of about 200'C, has a large Kerr rotation angle, and can be read with a good signal-to-noise ratio. However, even in this TbFeCo film, the Kerr rotation angle and temperature depend on the composition, and in order to obtain the maximum Kerr rotation angle, it is better to have a small amount of Tb. However, when the amount of Tb is small, there is a drawback that the N (noise) level increases due to the temperature dependence of saturation magnetization (M8), and the S/N ratio decreases. Therefore, the amount of Tb is 22 to 35 it
% TbFeCo film was suitable. Also C.

As the amount increases, the Kerr rotation angle increases, but the disadvantage is that the temperature of the lily increases and a large amount of energy is required for writing.

The present invention has been made to solve these problems, and provides a photothermal magnetic recording medium that can efficiently produce optical reproduction output by effectively utilizing the maximum obtainable Kerr rotation angle. .

[Means for solving problems]

The photothermal magnetic recording medium of the present invention has an axis of easy magnetization perpendicular to the film surface, and has a general formula Tbx (Fe1-y Coy
) A Tb-F.-Co ternary amorphous magnetic alloy layer represented by 1-x is provided on the substrate, and the magnetic layer is 0.
The layers are stacked so that X increases and y decreases sequentially from the light incident surface within the range of 15<X≦0.35.0<y<0.5.

[Effect]

The photothermal magnetic recording medium according to the present invention has a T
If the amount of b is small (the amount of cobalt is large), there is a film with the maximum Kerr rotation angle that can be obtained, and a large signal level can be obtained. , an increase in the noise level can be suppressed.Therefore, the writing sensitivity is also good, and the optical reproduction output can be efficiently output.

〔Example〕

FIG. 1 is a cross-sectional view of a photothermal magnetic recording medium according to an embodiment of the present invention, in which (1) is a substrate, and (2) is a Tb-Fe-Co ternary non-containing material whose composition is sequentially changed in the depth direction. It is a crystalline magnetic alloy layer. For the substrate (1), non-magnetic materials such as plastics, glass, and T-lamics are used as materials.

Tb -Fe-Co ternary amorphous magnetic layer [21tiTb
When x (Fel −y Coy ) 1-1, in the range of 0.15≦x≦0.35, y is 0 (y <
0.500 node range When recording and reproducing by entering light from the substrate side, X
In this layer, y increases and y decreases.

Examples of methods for forming this layer include a sputter link method and a vacuum evaporation method. In the case of sputter link method, Tb,
By sequentially changing the power input to each of the single metal targets of Fe and Co, the composition is changed in the film thickness direction. Further, it is thought that exchange coupling occurs between adjacent layers constituting the magnetic alloy layer, the composition of which changes sequentially.

Hereinafter, the present invention will be specifically explained using examples.

Example board: 1.2+im thick grooved plastic board Tb-
Fe-Co ternary amorphous magnetic alloy layer: thickness 1000
' Composition of the film surface on the A substrate side Tb1a, a (Fe7oC
o3o) sx, + Composition of the bottom surface of the membrane Tb33 (F
ee, C015) 67 A photothermal magnetic recording medium according to an embodiment of the present invention shown in FIG. 1 having the above structure was obtained.

FIG. 2 shows the results obtained by analyzing the Tb-Fe-Co ternary amorphous magnetic layer of the photothermal magnetic recording medium according to the embodiment of the present invention using an Auger electron spectrometer. Changes in each compositional element within the film thickness from the light incident surface (a 10%)
In the figure, (3) is Tb, (4
) is the characteristic of Fe, and (5) is the characteristic of Co.

Next, the optical reproduction output of the photothermal magnetic recording medium according to the embodiment of the present invention was measured. Disk speed is 9.
8 m/s, recording frequency IME (,.Compared with a recording medium using a TbFeCo ternary amorphous magnetic alloy layer with a constant composition in the film thickness direction, the S/N ratio is 5 dB higher. Ta.

In addition, in the above example, the magnetic layer was provided directly on the plastic substrate, but Si3N4 was provided on the plastic substrate.
A large S/N ratio is also obtained in a recording medium in which a dielectric film such as a dielectric film is provided, the composition of which is varied in the film thickness direction according to the present invention, and a protective film is finally formed.

In addition, although the composition was continuously changed in the examples,
Even if the composition changes in a stepwise manner, E
The same effects as in the embodiment described above are achieved.

FIG. 3 is a cross-sectional view of a photothermal magnetic recording medium according to another embodiment of the present invention). In the figure, (2m) to (2j) are magnetic layers, and Tbx(F@1-yCoy) l- When x, (2a) is X=18.7=30, (2b) is
=19.5.7=28, (2c) is! =21. y=26
, (2d) itx=22.5, 7=24, (2e) is! =24. y=22, (2f) is x=25.5.7=2
0. (2g) is X-27,7=18, (2h) is! =
28.5.7=16, (21) is X=30°7=14,
(2j) x=31.5+y=12.

〔Effect of the invention〕

As explained above), this invention has an axis of easy magnetization perpendicular to the film surface, and has a general formula Tbx(Fel-yCoy)l
In the case where the TbFeCo ternary thread amorphous ternary amorphous magnetic alloy layer is represented by -x, the magnetic alloy layer is
<X<0.35.0 (y (in the range of 0.5, by using stacked layers such that X increases sequentially and y decreases from the light incidence surface, the maximum obtainable It is possible to obtain a photothermal magnetic recording medium that can efficiently produce optical reproduction output by effectively utilizing the Kerr rotation angle.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a photothermal magnetic recording medium according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a photothermal magnetic recording medium according to an embodiment of the present invention. FIG. 3, a characteristic diagram showing changes in compositional elements (a 10%), is a sectional view of a photothermal magnetic recording medium according to another embodiment of the present invention. In the figure, (1) is the substrate, (2) is T b-F e-
This is a Co ternary amorphous magnetic alloy layer.

Claims (1)

[Claims] It has an axis of easy magnetization in the direction perpendicular to the film surface, and has the general formula Tb_x(
T denoted by Fe_1_-_yCo_y)_1_-_x
In the case where a b-Fe-Co ternary amorphous magnetic alloy layer is provided on the substrate, the magnetic layer has a 0.15≦x≦0.35
, 0<y<0.5, the photothermal magnetic recording medium is characterized in that the layers are stacked so that x increases and y decreases sequentially from the light incident surface within the range of 0<y<0.5.