JPH047023B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to an E-DRAW type optical disk, and more particularly to a magneto-optical recording medium carrying a recording film made of an amorphous alloy composed of rare earth metals and transition metals and having uniaxial magnetic anisotropy in the direction perpendicular to the film surface. Regarding. BACKGROUND ART Conventionally, alloy thin films of rare earth metals and transition metals such as GdTbFe (gadolinium-terbium-iron), TbFeCo (terbium-iron-cobalt), etc., have been produced by a method such as high-frequency sputtering under certain conditions. is known to have an amorphous structure and uniaxial magnetic anisotropy perpendicular to the film surface. This property can be utilized as a recording film of a magneto-optical recording medium. That is, recording and reading of information is performed as follows. First, a laser beam of a certain wavelength is focused on an amorphous alloy film having uniaxial magnetic anisotropy through an objective lens, etc., and the focused portion is heated to the Curie temperature or compensated by applying an external magnetic field using a permanent magnet or an electromagnet. Locally heats up to around temperature. At this time, due to the thermomagnetic effect of thermal demagnetization or magnetization reversal in the focused portion, information can be recorded by forming reversed magnetic domains in the plane of the alloy film that is uniformly magnetized in one direction. Next, a polarized laser beam is incident on the formed inverted magnetic domain, and the presence or absence of the inverted magnetic domain can be detected as a signal by the Polar Kerr effect or the like in the reflected light. In this way, by associating the presence or absence of an inverted magnetic domain with "1" and "0" in the recording medium, it becomes possible to read recorded information. Conventional amorphous alloys of rare earth metals and transition metals, such as GdTbFe and TbFeCo, have magneto-optical effects and magnetic properties, especially the Curie point, compensation temperature between room temperature and about 200℃, and coercive force of several
Since it is suitable as a magneto-optical recording material with KOe, it is attracting attention as a magneto-optical recording film material for magneto-optical recording media and its practical application is being considered. Regarding such a magneto-optical recording medium, as shown in the schematic cross-sectional view of a conventional magneto-optical recording medium in FIG. The most commonly developed. However, such an amorphous amorphous alloy film needs to be a perpendicularly magnetized film having uniaxial magnetic anisotropy in a direction perpendicular to the film surface, whereas conventional amorphous alloys require that their easy magnetization direction is perpendicular to the film surface. It cannot be said that the Kerr rotation angle is sufficient for reading with a laser beam. Therefore, in order to obtain a larger Kerr rotation angle, there has been a demand for an amorphous alloy film as a perpendicularly magnetized film in which the direction of easy magnetization of the recording film is as perpendicular to the film surface as possible. However, even in conventional magneto-optical recording media, it has not been possible to obtain a sufficiently large Kerr rotation angle. SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical recording medium having a large Kerr rotation angle. The magneto-optical recording medium of the present invention is a magneto-optical recording medium having a transparent substrate and a rare earth metal-transition metal amorphous alloy film supported on the substrate and having uniaxial magnetic anisotropy in a direction perpendicular to the film surface. , an intermediate film is provided between the transparent substrate and the amorphous alloy film, and the intermediate film is a simple substance of a group B element in the periodic table, a compound of a group B element and a group B element, and a compound of a group B element and a compound of a group B element. Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. FIG. 2 is an enlarged partial cross-sectional schematic diagram of the magneto-optical recording medium of the present invention. On one side of the disc-shaped PMMA substrate 1 with a guide groove, an intermediate film 4 made of a simple substance of Ge (germanium), which is an element of Group B in the periodic table;
A magneto-optical recording medium is prepared by sequentially laminating a rare earth metal-transition metal amorphous alloy film 2, which is a magneto-optical recording film, and a protective film 3 made of SiO ₂ by a method such as vacuum evaporation or sputtering. Note that the amorphous alloy film 2 is formed to have an alloy composition of the following formula. (R _x T _1-x ) _1-y Al _yIn the above formula, the rare earth metals R are Gd (gadolinium), Tb (terbium), and Dy (dysprosium).
The transition metal T is one or more metals selected from Fe (iron) and Co (cobalt). The atomic composition ratio x of the rare earth metal R and the transition metal T is set to a value in the range of 0.1≦x≦0.4 in R _x T _1-x . It is known that perpendicular magnetization in this range can be obtained by vacuum evaporation, sputtering, or the like. Furthermore, in this embodiment, Al (aluminum) is added as an additive element to this rare earth metal-transition metal alloy. An alloy (RT) in which aluminum is added to a rare earth metal-transition metal alloy in an amorphous alloy, _1-y Al _y is
The amorphous alloy film of the magneto-optical recording medium is formed such that y has a value in the range of 0.005≦y≦0.4. When y<0.005, the addition of Al has no effect on improving oxidation resistance. Also, y>
At 0.4, the magnetic properties and magneto-optical properties drop sharply, making it unsuitable as a magneto-optical recording medium. In Table 1, the wavelengths of the optical recording medium of this example and the conventional one were measured at 45°C and 90% RH (humidity).
The results of investigating each Kerr rotation angle θk in an experiment in which reproduction was performed using 830 nm semiconductor laser light are shown. Here, three materials are examined in which the optical recording medium of this embodiment and a conventional one were manufactured under the same conditions.

Table 1 shows that the Kerr rotation angle θk of the optical recording medium of this example is approximately twice or more than the Kerr rotation angle θk of the conventional optical recording medium. As shown in Fig. 2, since the intermediate film 4 made of simple Ge, which is a group B element, is formed between the substrate 1 and the amorphous alloy film 2, the perpendicular magnetization is achieved by the intermediate film made of Ge. This shows that the component increases, giving an effect of increasing the Kerr rotation angle. Furthermore, in the above embodiment, Ge, which is a simple substance of Group B element, is used as the intermediate film, but similarly,
The same Kerr rotation angle as described above is also applied to an optical recording medium provided with an interlayer film formed of each of group B elements Sn (tin), Pb (lead), Si (silicon), and C (carbon). It was confirmed that there was an increasing effect. Furthermore, when GaAs (gallium-arsenide), InSb (indium-antimony), and InP (indium-phosphorus), which are compounds of group b elements and group b elements, are used as the intermediate film of the optical recording medium,
and compounds of group b elements and group b elements such as ZnS (zinc sulfide), ZnSe (zinc-selenium), and
Even in optical recording media using ZnTe (zinc-tellurium), the wavelength is
It was confirmed that when reproducing using an 830 nm semiconductor laser, there was the same effect of increasing the Kerr rotation angle as described above. Furthermore, in the above embodiments, an optical recording medium provided with one layer of the intermediate film was manufactured, but an optical recording medium provided with two or more layers of the intermediate film can also be manufactured. At this time, as a combination of two or more interlayer films, the above-mentioned Ge, Sn,
Pb, Si, C, GaAs, InSb, InP, ZnS, ZnSe,
An optical recording medium is produced so that two adjacent interlayer films made of a material selected from ZnTe are different from each other.
By doing so, it is possible to obtain an optical recording medium that has the effect of increasing the Kerr rotation angle. Effects of the Invention As described above, according to the present invention, a substance selected from a simple substance of a group B element, a compound of a group B element and a group B element, and a compound of a group B element and a group B element; A magneto-optical recording medium with an increased Kerr rotation angle can be obtained by providing one or more intermediate films consisting of one or more layers between the recording film and the substrate.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a conventional magneto-optical recording medium, and FIG. 2 is a schematic sectional view of a magneto-optical recording medium according to the present invention. Explanation of symbols of main parts, 1...PMMA board,
2...Amorphous alloy film, 3...Protective film, 4...
...intermediate film.

Claims (1)

[Scope of Claims] 1. A magneto-optical recording medium comprising a transparent substrate and a rare earth metal-transition metal amorphous alloy film supported on the substrate and having uniaxial magnetic anisotropy in a direction perpendicular to the film surface, which comprises: An intermediate film is provided between the transparent substrate and the amorphous alloy film, and the intermediate film is composed of an element of group b in the periodic table,
A magneto-optical recording medium characterized in that it is a film made of a material selected from the group consisting of a compound of a group b element and a group b element, and a compound of a group b element and a group b element. 2. The magneto-optical recording medium according to claim 1, wherein the intermediate film has two or more layers, and two adjacent layers are films made of different types of substances. 3 The elemental elements of group b are Ge, Sn, Pb, and Si.
and C, the compound of the group b element and the group b element is GaAs, InSb, and InP, and the compound of the group b element and the group b element is
The magneto-optical recording medium according to claim 1 or 2, characterized in that the medium is ZnS, ZnSe, and ZnTe.