JPS62222609A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To enable fabrication of an alloy target of low oxygen concentration and to improve a recording sensitivity without damaging reproducing characteristics by composing a part of rare earth elements which compose a thin film of an amorphous rare earth - transition metal alloy as a recording film out of light rare earth element. CONSTITUTION:A part of rare earth elements for composing a thin film of an amorphous rare earth - transition metal alloy as a recording film of a photomagnetic recording medium is composed of light rare earth element. The rare earth element (LR) is composed of at least one of the elements Ce, PR, Nd, and Sm. The transition metal (TM) and the rare earth element are composed of at least one of Fe, Co, and Ni, and Gd, Tb, and Dy, respectively. When a composition formula of the recording film is (LRxHR1-x)yTM100-y, 0.01<x<=0.60, 10<=y<=50. As the recording medium, aluminum nitride AlN 2, a recording layer 3, and an AlN film 4 are grown on a polycarbonate substrate 1 provided with grooves by spattering technique.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides, for example, by irradiating laser light,
Pertains to magneto-optical recording media that can be recorded, reproduced, and erased.

[Conventional technology]

The material conventionally proposed as a recording material for magneto-optical recording media is an amorphous alloy thin film consisting of at least one element of Gd, Tb+Dy, and at least -m or more of Fe+Co+Ni. Manufactured using sputtering and vacuum evaporation methods.

Furthermore, the apparent magnetization is called the compensation composition, which is 1g1l.
It is commonly used in compositions that do not exceed 11+1J.

In general, in magneto-optical recording, the reproduction C/N (carrier-to-noise ratio) is determined by the magneto-optical rotation angle (magnetic Kerr rotation angle "K r
and the Faraday rotation angle θF).

In addition, the writing sensitivity, especially in the case of single-point writing, is affected by the temperature of the key, and the temperature of the key is 150 to 200°C.
medium is considered appropriate.

[Problem that the invention seeks to solve]

However, there is a generally positive correlation between temperature and magneto-optical rotation angle. J There is a negative correlation between temperature and writing sensitivity. Therefore, T b
F e Cor G o l T b F e +
A material with a large magneto-optic effect such as T b D y F e Co requires a large amount of energy to write, and
A material with a low keying point such as bFerDyFe has the disadvantage that the reproduced signal is small and a large C/N cannot be obtained.

On the other hand, as the heavy rare earth-centered metal film used in conventional magneto-optical recording, a sputtered film having a composition close to the compensation composition having a large coercive force is generally used. In order to form a film by sputtering, it is essential to use a target with a composition close to the desired film composition. However, such alloy systems usually form a large number of intermetallic compounds, and alloys made by casting methods generally become polycrystalline bodies with large grains of various compound phases and cracks. However, special techniques are required to produce alloy targets. Therefore, in order to create a thin film by sputtering, a multi-target simultaneous sputtering method or a composite target method is often used, in which a plurality of different targets are used simultaneously and alloyed during film formation. However, these methods also require uniformity of film properties,
There are problems with composition control, etc. Furthermore, a sintered body produced by powder metallurgy can be used as a target, but it is recommended that the oxygen content in the target be kept below 11,000 pp. This has a serious effect on the properties of the recording film, so It is desirable to use concentration targets.

Therefore, the present invention aims to solve these problems.
The purpose is to enable the production of f'l- alloy targets with low oxygen concentrations and to provide a magneto-optical recording medium with excellent recording film and strength without impairing the repeatability characteristics.

[Failure to solve the problem]

In order to solve the above problems, the magneto-optical recording medium of the present invention is characterized in that a part of the rare earth elements constituting the amorphous rare earth-transfer metal alloy thin film which is the recording film thereof is a light rare earth element. , the light rare earth element (hereinafter referred to as LR) is Ce +
From PR+Nd, Sm, the transition metal (TM) is Fe +C
From o+Nt, the remaining rare earth is composed of one or more elements selected from Gd, Tb, and D)'.

When the compositional formula of the recording film is (LRXHRI-z)y TMto o-y, in the present invention, α01×x≦α6o, 1o≦y≦50
It is.

〔Example〕

The present invention will be described in detail below based on Examples.

All of the examples of the present invention were created by the sputtering method, and unless otherwise noted, an alloy target of 4 inches in diameter and 411IL in thickness was used in a low-frequency induction heating furnace to create the recording film. are doing. In addition,
The oxygen concentration in the targets was less than 500 ppm for all targets. Sputtering was carried out after introducing a high purity argon gas of 2 x 10''3 Torr into a vacuum chamber that had been evacuated to less than IXIG-''l'orr in advance. , by applying high-frequency power.

Table 1 shows the composition of the thin film of this example and the composition of the comparative example.The sample of the comparative example was prepared using a composite target in which rare earth and CO chips were arranged on an Fe target.

Table 1 and Table 2 show the temperature at which the magneto-optic effect disappears (Kiely point) and the Kerr rotation angle at M11% for the examples and comparative samples described above.

Table 2 Sample name Single point (°C) -4th orbital angle (degrees)
Example 1 250 [138//
2 300 α
42//3 210
(L 55//4 220
α34tt5 210
α65 6 270
0.39 Comparative example 1 2
40 [L37//2 2
80 Q, 41 These records 1
T! i! A disk was created using the configuration shown in Figure 1. That is, on a grooved polycarbonate substrate 1, a film 4 of aluminum nitride (AIN) 2 (IOA) was formed by sputtering.
The recording and reproducing characteristics were compared using a recording and reproducing apparatus based on the Faraday method using an lAs semiconductor laser (g, length 780 nm). The recording/reproducing conditions are a medium rotation speed of 90 Orpm.
Recording frequency 1MHz + bias magnetic field 5000e
When the Funao laser power is 1 mW, the C/N is the value of the bandwidth KHz.

2 and 5 show the relationship between reproduction C/N (dB) and second harmonic suppression ratio (dB) with respect to write power in Example 1 and Comparative Example 1.

If the write power at which the second-order harmonic suppression ratio is minimized is expressed as the optimal write power pw (mw), then in the first embodiment, P
w = 5.5 m w + C/N -52d B
+Comparative example 1 is p vi -7.5m W+ C/N
-51 dB, and although Example 1 of the present invention had good recording sensitivity, a high reproduction C/N value was obtained.

Further, it is desirable that the rise of C/H near PW is steeper in this embodiment from the viewpoint of preventing erroneous writing during reproduction.

Table @3 shows the optimum write power and reproduction C/N of the present example and the comparative example.

Table 3 Similar to the example shown earlier, all of the present examples are capable of high-sensitivity writing and have a high reproduction C/N ratio.0 [Effects of the Invention] As described above, according to the present invention, , it is possible to supply an unprecedented magneto-optical recording medium with high recording sensitivity and high quality reproduction C/N. This effect is not limited to recording films made by sputtering, but can also be applied to conventional vacuum evaporation methods and ion grating methods, as well as to reproduction methods that utilize the Kerr effect. Of course, similar effects can be obtained.

Further, the substrate and the protective film are not limited to those shown in the embodiments. For example, the substrate may be made of acrylic plastic or glass, and the protective film may be a dielectric film such as Si3N4 or a mixture of AIN and 5iaN4.

Furthermore, when a recording film is formed by sputtering, an alloy target with a low oxygen content can be produced by a simple process of melting and casting, so a magneto-optical recording medium with excellent quality and cost can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the structure of a magneto-optical recording medium of the present invention, and FIGS. 2 and 3 show reproduction C with respect to recording power of a magneto-optical recording medium of the present invention and a conventional optical recording medium, respectively. FIG. 3 is a diagram showing the relationship between /N and second harmonic suppression ratio. 1... Surface-mounted transparent substrate 2... Transparent dielectric layer 3... Recording layer 4... Transparent dielectric layer and above Applicant Seiko Epson Corporation B Noah's 7-figure Ray No. 1 (Sold W) 21 0 2 μ 6 17 70 Ray No. 1 (M cape 4 colors U 19

Claims (3)

[Claims] (1) A magneto-optical recording medium having an amorphous rare earth-transition metal alloy thin film as a recording film, wherein a part of the rare earth element is a light rare element. (2) The light rare earth elements (LR) are Ce, Pr, and Nd.
, Sm, and the transition metal (TM) is composed of one or more elements selected from Fe, Co, and Ni. The magneto-optical recording medium described above. (3) The composition of the recording film is {LR_xHR_1_-_x}_yTM_1_0_0_ in atomic ratio
-_y[0.01<x≦0.6010≦y≦50] (wherein, HR is one or more elements selected from Gd, Tb, and Dy) Claim 1 Magneto-optical recording medium as described in .