JPS63302448A - Optical thermomagnetic recording medium - Google Patents

Abstract

PURPOSE:To enable efficient taking out of light reproduction output by disposing a 1st ternary amorphous magnetic TbFeCo alloy layer where the sub-lattice magnetization of FeCo is dominant at a room temp. and further, disposing the 2nd ternary amorphous magnetic TbFeCo alloy layer where the sub-lattice magnetization of Tb is dominant at a room temp. and utilizing an exchange bonding. CONSTITUTION:This recording medium has a magnetic layer 4 which is formed by laminating the 1st ternary amorphous magnetic alloy layer of TbFeCo having the axis of easy magnetization in the direction perpendicular to the film plane and expressed by Tbx(Fe1-yCoy)1-x and the 2nd ternary amorphous magnetic alloy layer 3 of TbFeCo having the axis of easy magnetization in the direction perpendicular to the film plane and expressed by Tbx(Fe1-yCoy)1-x and in which the 1st and 2nd amorphous magnetic alloy layers 2, 3 are exchange-bonded. The 1st amorphous magnetic alloy layer 2 is of 0.1<=x<=0.2, 0<y<0.5 and the 2nd amorphous magnetic alloy layer 3 is of 0.2<x<=0.35, 0<=y<0.5. The sub-lattice magnetization of FeCo is dominant in the 1st amorphous magnetic alloy layer 2 at the room temp. and the sub-lattice magnetization of Tb is dominant in the 2nd amorphous magnetic alloy layer. The light reproduction output is taken out efficiency by effectively utilizing the resultant max. angle of Kerr rotation.

Description

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

C. Prior Art] Conventionally, as a photothermal magnetic recording medium, MnB1. MnC
Polycrystalline thin film such as uB1, GdCo, GdFe, Tb
Amorphous thin films such as Fe, DyPe5GdTbFe, and TbDyFe, and single crystal thin films such as CRC are known. Among these 'fi1m', there is film-forming ability to produce a large-area thin film at a temperature near room temperature, writing efficiency to write signals with small photothermal energy, and write signals of 511.
Recently, the above-mentioned amorphous thin film is considered to be superior in terms of readout efficiency.

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.

In addition, GdFe and GdCo perform writing using magnetic compensation points, and in order to make the writing efficiency uniform,
There is a problem in that the film composition must be strictly controlled during film formation. Also, TbFe, DyFe, Tb
Since DyFe allows writing at a single Curie point, there is no need to control the film composition so severely, but since the single Curie point is low at around 100 degrees Celsius, there is a problem in that high-power light cannot be used when reading signals. . If the Curie temperature is lower, the writing efficiency will improve, but the written signal will be disturbed by the ambient temperature or the read light. Considering this, a temperature of around 200°C is desirable.

Further, the read SN ratio by reflected light is proportional to 5θK, where R is the reflectance and θ is the Kerr rotation angle.

Therefore, in order to read with a good signal-to-noise ratio, the Kerr rotation angle should be increased. FIGS. 6(a) and (b) respectively show Tbx(Fel-y
Coy) Kerr rotation angle (d) depending on the composition (x) of the I-X film
3 is a characteristic diagram showing changes in Curie temperature ('C) depending on composition (x); and FIG.

In the figure, (^) is the characteristic of y=0.17, and (B) is the characteristic of y
In each figure, the horizontal axis is the composition (x), the vertical axis is the Kerr rotation angle (deg・) (Figure 6 (a)), the horizontal axis is the composition (x), and the vertical axis is the composition (x). Curi temperature (℃) (Figure 6 (b)
)).

Regarding TbFeCo in Table 1, JP-A-58
It is reported in Publication No.-73746.

Table 1 Furthermore, as a method using a film with a high Curie temperature, a writing layer having a high coercive force and perpendicular magnetic anisotropy is provided on the upper surface of the substrate, as shown in Japanese Patent Application Laid-open No. 153546/1983. However, a medium has been proposed in which a reading layer having a large magneto-optic effect, low coercive force, and perpendicular magnetic anisotropy is disposed on the upper surface of the writing layer.

Furthermore, in JP-A-57-78652, a low coercive force layer having one low Curie point that can be perpendicularly magnetized is formed on the negative side, and a low coercive force layer having one high Curie point on the other side. A medium in which the high coercive force layer and the low coercive force layer are exchange-coupled has been reported.

[Problem to be Solved by the Invention 3] As shown in Table 1, the TbFeCo film preferably has a Curie temperature of around 200° C., has the largest Kerr rotation angle among them, and can be read out with a good signal-to-noise ratio.

However, even in this TbFeCo film, the Kerr rotation angle and Curie temperature depend on the composition as shown in Figure 5, and in order to obtain the maximum Kerr rotation angle, it is better to have less Tb1l, but when Tb1l is small, However, due to the temperature dependence of saturation magnetization (Ms), the N (noise) level increases and the S/N ratio decreases. Therefore, Tb1jl is 22
A TbFeCo film of about 35 at% was suitable.

Furthermore, as the amount of Co increases, the Kerr rotation angle increases, but there is a drawback that the Curie temperature increases and a large amount of energy is required for writing.

Furthermore, in the TbFeCo ternary alloy thin film, Tbx (Fe
+ Y Coy) When l-11, y≧0.5
In this case, regardless of whether it is used for the first layer or the second layer, the Curie temperature of the film becomes too high and recording is impossible.

Furthermore, in the method disclosed in Japanese Patent Application Laid-Open No. 56-153546, information is written in a writing layer, the information is transferred from the writing layer to a reading layer, and the reading layer is irradiated with polarized light to reproduce the information. Since it uses a layer combination that allows easy transfer, it is necessary to choose a combination of layers that can be easily transferred. Therefore, a TbCo film or a DyFe film is used for the writing layer, etc., and a GdFe film is used for the reading layer.

It is necessary to use a GdCo film or the like, which has the disadvantage that the structure is complicated and the manufacturing method is also complicated. Furthermore, since there is a writing layer between the readout layer and the substrate, the reproduction light does not pass through the substrate and is read directly from the ventral side even if it passes through a protective film. It has the disadvantage of being influenced.

Further, in Japanese Patent Application Laid-Open No. 57-78652, the high coercive force layer is preferably a TbFe film, a DyFe film,
A GeFe film, a GdCo film, etc. are exemplified as the low coercive force layer, and when a two-layer film containing different elements is used, the structure becomes complicated and the manufacturing conditions become difficult.

Furthermore, even if the medium is exchange-coupled, for example, Tb
In the case of a combination of an Fe film and a GdFe film, a TbPe film with dominant Tb sublattice magnetization and a GdFE film with dominant Gd sublattice magnetization cannot obtain a large Kerr rotation angle, and no improvement in the S/N ratio can be expected. In addition, when using a TbFe film in which Fe sublattice magnetization is dominant and a GdFe film in which Fe sublattice magnetization is dominant, the noise level increases and an improvement in the S/N ratio cannot be expected.

The present invention has been made to solve these problems, and provides a photothermal magnetic recording medium that can efficiently extract 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(Fe+yCoy)+
TbFeCo ternary system first amorphous magnetic alloy layer represented by -8, and Tb having an axis of easy magnetization perpendicular to the film surface and represented by the general formula Tby (Fe, V Coy) + -x.
A FeCo ternary-based second amorphous magnetic alloy layer is laminated on a substrate, the first and second amorphous magnetic alloy layers are exchange-coupled, and the first amorphous magnetic alloy layer is In,
0.1≦X≦0.2, o<y<o, s, in the second amorphous magnetic alloy layer, 0.2<X≦0.35.0≦y<
o, s, and the first amorphous magnetic alloy layer has FeCo sublattice magnetization predominant, and the second amorphous magnetic alloy layer has Tb sublattice magnetization predominant at room temperature.

[For production]

The photothermal magnetic recording medium of the present invention has a T
A large signal level can be obtained by disposing the bFeCo ternary first amorphous magnetic alloy layer, and further by disposing the TbFeCo ternary second amorphous magnetic alloy layer in which Tb sublattice magnetization is dominant at room temperature. By using exchange coupling, we were able to suppress the increase in noise level and obtain a large signal-to-noise ratio. Furthermore, as a result of using exchange coupling, it has become possible to reduce the write energy.

〔Example〕

FIG. 1 is a sectional view of a photothermal magnetic recording medium according to an embodiment of the present invention, in which fil is a substrate, (2) is a TbFeCo ternary first amorphous magnetic alloy layer, and (3) is a TbFeCo ternary first amorphous magnetic alloy layer. 2 amorphous magnetic alloy layer, the above-mentioned 1. A magnetic layer (4) is formed from the second amorphous magnetic alloy layer. As the substrate fil,
Non-magnetic materials such as glass, ceramics, and plastics are used as materials.

The TbFeCo ternary first amorphous magnetic alloy layer (2) is
When Tbx(Fe+ y CoyL-++, X is in the range of 0.1≦X≦0.2, and y is in the range of 0<y<0
．． 5, and the FeCo sublattice magnetization is dominant at room temperature.

The TbPeCo ternary-based second amorphous magnetic alloy layer (3) is
When Tbx(Fe+y Coy)+-++, X is in the range of 0.2<X≦0.35, and y is 05
The range is y<0.5, and Tb sublattice magnetization is dominant at room temperature. and TbFeC.

It is necessary that the first ternary amorphous magnetic alloy layer and the second TbFeCo ternary amorphous magnetic alloy layer are exchange-coupled.

Note that in order to form the magnetic layer having the above structure, a film is formed by, for example, a sputtering method, a vacuum evaporation method, or the like.

Hereinafter, this invention will be explained in detail by way of examples.

Example 1 Substrate: 1.2m thick plastic substrate TbPeCo Ternary first amorphous magnetic alloy layer: Tb+s
, 1 (FeyoCOso) ez, n Film thickness: 200 Coercive crab llc z 2 KOe Curie temperature: 250
℃ TbFeCo Ternary system second amorphous 'Jf magnetic alloy layer: Tb
zs, h(FewoGO+o) vi, a Film thickness: 600
A photothermal magnetic recording medium according to an embodiment of the present invention was obtained by a sputtering method using the above-mentioned constituent materials.

Comparative Example 1 The TbFeCo ternary first amorphous magnetic alloy layer in Example 1 was omitted, and Tb+e, h (FetoCos
o) A photothermal magnetic recording medium was obtained by laminating only 800 people of sz and a in the same manner as in Example 1. FIG. 2 shows its cross-sectional view.

Examples 2 to 11 Other examples of photothermal magnetic recording media of the present invention were obtained in the same manner as in Example 1, except that the constituent materials shown in Table 2 were used.

Comparative Examples 2 to 9 Photothermal magnetic recording media were obtained in the same manner as in Example 1, except that the constituent materials shown in Table 2 were used.

Recording/Reproduction Characteristic Test A recording/reproduction characteristic test was conducted on the photothermal magnetic recording medium of the example of the present invention and the photothermal magnetic recording medium of the comparative example obtained as described above at a disk speed of 9.8 m/s and a recording frequency of IMHz. Ta. The results are shown in Figures 3 and 4.
As shown in the figure. Figure 3 shows S by write power (mW).
/N (dB) change, and in the figure (n+
) is the characteristic of Example, and (n) is the characteristic of Comparative Example 1. Here, the horizontal axis is the write power (mW), and the vertical axis is S
/N (dB). Figure 4 shows the readout power (m
This is a special table 2 characteristic chart showing the change in S/N (dB) due to W), in which (Al) (A2) is the characteristic of the example,
(Bl) (B2) are the characteristics of Comparative Example 1. Here, the horizontal axis represents read power (-), and the vertical axis represents S/N (d
B) is shown.

Further, Table 2 shows the constituent materials used and the S/N of the obtained photothermal magnetic recording medium.

According to this, the example has S from a lower power than the comparative example.
The N-ratio is high, ie, it can be written with less energy, and in embodiments a high SNR can be maintained up to high read powers. Further, the change in S/N (dB) due to changing the composition of Tb is shown in FIG. 5. From this figure, it can be seen that the S/N is good when 0.1≦X≦0,2.

As described above, by using the photothermal magnetic recording medium of the embodiment of the present invention, it is possible to write with small energy, maintain a high S/N ratio up to a large read power, and have a higher optical reproduction output than the conventional one. Therefore, if it is used as a photothermal magnetic memory such as a so-called beam-addressable file memory that performs reading using a writing Kerr effect using a light beam, an excellent memory device with extremely high density and a high signal-to-noise ratio can be realized.

It goes without saying that a dielectric layer such as a silicon nitride film may be provided between the substrate fil and the TbFeCo ternary first amorphous magnetic alloy layer (2) to provide an effect of increasing the Kerr rotation angle. Nor.

In the above embodiment, recording and reproduction are performed from the substrate side, but when recording and reproduction is performed from the film surface side, the TbFeCo ternary first amorphous magnetic alloy layer and the TbF
It goes without saying that the configuration in which the eCo ternary-based second amorphous magnetic alloy layer is formed and implemented in reverse is the same as in the embodiment of the present invention.

That is, the TbFeCo ternary first amorphous magnetic alloy layer and the TbFeCo ternary amorphous magnetic alloy layer
The bFeCo S-based second amorphous magnetic alloy layer does not specify which layer is the read layer and which is the write layer.

Further, it does not define a high coercive force layer and a low coercive force layer.

(Effects of the Invention) As explained above, the present invention has an axis of easy magnetization perpendicular to the film surface, and has a general formula Tbx(Fe+ -y Coy
), and a TbFeCo ternary first amorphous monomagnetic alloy layer represented by , and a TbFeCo ternary having an axis of easy magnetization perpendicular to the film surface and represented by the general formula Tbx (Fe, -y Coy) +4. A system second amorphous magnetic alloy layer is laminated on a substrate, the first and second amorphous magnetic alloy layers are exchange-coupled, and the first amorphous magnetic alloy layer includes: 0.1≦X≦0.2, O<7<0.5
, in the second amorphous magnetic alloy layer, 0.2<X≦0
．． 35, O≦y<0.5, and at room temperature, the first amorphous magnetic alloy layer has dominant FeCo sublattice magnetization, and the second amorphous magnetic alloy layer has dominant Tb sublattice magnetization. By using this method, it is possible to obtain a photothermal magnetic recording medium that can efficiently utilize the maximum Kerr rotation angle that can be obtained to obtain optical reproduction output.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a photothermal magnetic recording medium according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of a conventional photothermal magnetic recording medium, and Fig. 3 is S/N (dR) depending on writing power (m-). A characteristic diagram showing changes in S
/N (dB) change, Figure 5 is a characteristic diagram showing S/N (dB) change when the composition of Tb is changed, and Figures 6 (a) and (b) are Tbx ( Fe+
FIG. 3 is a characteristic diagram showing changes in the Kerr rotation angle (deg, ) depending on the composition (x) and changes in the Curie temperature ('C) depending on the composition (x) of each of the 'ICoy)+-x films. In the figure, (1) is the substrate, and 2) is TbFeCo 3
The first amorphous magnetic alloy layer (3) is TbFeCo 3
The second amorphous magnetic alloy layer (4) is a magnetic layer. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa Fig. 1 1: Board Fig. 2 Fig. 3 Fig. 4 1 “Kiko H Power (11l/J)
DIEh output Lno17-(ynW') Fig. 5 X ((at'A) Tbx (Feo, 7Coo3) l-x Fig. 6 (b)

Claims (1)

[Claims] (1) Has an axis of easy magnetization perpendicular to the film surface, and has the general formula Tb
It has a TbFeCo ternary first amorphous magnetic alloy layer represented by _X(Fe_1_-_yCo_y)_1_-_X and an axis of easy magnetization perpendicular to the film surface, and has a general formula Tb_X(
T denoted by Fe_1_-_yCo_y)_1_-_X
a bFeCo ternary-based second amorphous magnetic alloy layer is laminated on a substrate, the first and second amorphous magnetic alloy layers are exchange-coupled, the first amorphous magnetic alloy layer , 0.1≦X≦0.2, 0<y<0.5, and in the second amorphous magnetic alloy layer, 0.2<X≦0.35, 0≦y
<0.5, and the first amorphous magnetic alloy layer has a dominant FeCo sublattice magnetization, and the second amorphous magnetic alloy layer has a dominant Tb sublattice magnetization at room temperature.