JPH05174437A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To lower a Curie temp. without impairing a Kerr rotating angle and to improve recording efficiency and reproducing efficiency by consisting the magneto-optical recording medium of a quaternary alloy of amorphous Td-Dy- Fe-Co having an axis of easy magnetization in the direction perpendicular to the film plane. CONSTITUTION:The magneto-optical recording medium consists of the quaternary alloy of the amorphous Td-Dy-Fe-Co having the axis of easy magnetization in the direction perpendicular to the film plane and has the magnetic alloy film satisfying the following general formula (Tb1-zDy)1-y(Fe1-xCox)y, 0<x<=0.3, 0.2<=y<=0.8, 0.3<=z<=1. The sufficient magnetic anisotropy and the sufficient Kerr rotating angle are provided on the magneto-optical recording medium by adopting the compsn. regulated by the above-mentioned general formula. In addition, reading out at a good S/N is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium used for a magneto-optical memory, magnetic recording, a display element, etc., and particularly for reading using a magneto-optical effect such as a magnetic Kerr effect or a Faraday effect. The present invention relates to a magneto-optical recording medium that can be used.

[0002]

2. Description of the Related Art Conventionally, MnB has been used as a magneto-optical recording medium.
i, MnCuBi and other polycrystalline thin films, GdCo, GdF
e, TbFe, DyFe, GdTbFe, TbDyFe
Amorphous thin films such as GdIG and single crystal thin films such as GdIG are known.

Among these thin films, film-forming properties when a large-area thin film is manufactured at a temperature near room temperature, writing efficiency for writing a signal with small optical energy, and S / N ratio of a written signal. Considering the reading efficiency for good reading, the amorphous thin film has recently been considered to be excellent as a magneto-optical recording medium.

[0004]

However, various drawbacks have been pointed out in the above amorphous thin film.

For example, GdFe has a small coercive force, and recorded information is unstable. In addition, GdFe, GdCo
Performs writing using a magnetic compensation point, and in order to make writing efficiency uniform, the film composition must be strictly controlled during film formation. TbFe, DyF
In e and TbDyFe, since the Curie point is written, the film composition is not so strictly controlled, but since the Curie point is as low as 100 ° C. or lower, there is a drawback that light with high power cannot be used when reading a signal. ..
If the Curie temperature is low, the writing efficiency is improved, but the written signal is disturbed more by the ambient temperature and the reading light. Therefore, the magnetic transformation temperature is preferably 100 ° C. or higher in consideration of the condition of use.

On the other hand, the read S / N ratio by reflected light is
Let R be the reflectance and θk be the rotation angle of the car.

[0007]

[Equation 1] Proportional to. Therefore, in order to read out with a good S / N ratio,
The car rotation angle should be increased. Table 1 shows the Kerr rotation angle of the amorphous magnetic film.

[0008]

[Table 1] Of these, the Kd rotation angle of GdTbFe is the largest.

However, this value is still not sufficient, and as a result of further research on increasing the Kerr rotation angle, GdFeC obtained by adding Co to GdFe or TbFe was found.
o and TbFeCo have large Kerr rotation angles, especially GdT
It was found that a quaternary amorphous magnetic alloy of GdTbFeCo in which Co is added to bFe is excellent in thermal stability, has a sufficiently large Kerr rotation angle, and can be read out with a good S / N ratio. It was

As described above, in the conventional rare earth-transition metal type amorphous magnetic alloy, Fe and Co are used as transition metals.
It can be seen that the system containing K increases the Kerr rotation angle.

However, the addition of Co raises the Curie temperature. Table 2 shows TbFeCo and GdFeC
The Kerr rotation angle and Curie temperature of o are shown.

[0012]

[Table 2] As described above, by adding Co, it is possible to increase θk, but if the Curie temperature becomes too high accordingly, the recording sensitivity is significantly lowered.

An object of the present invention is that not only the Kerr rotation angle is sufficiently large and the reading with a good S / N ratio is possible.
An object is to provide a magneto-optical recording medium having an appropriate Curie temperature value.

[0014]

The magneto-optical recording medium of the present invention which can achieve the above object is made of an amorphous Td-Dy-Fe-Co quaternary alloy having an easy axis of magnetization in the direction perpendicular to the film surface. becomes the following general formula _{(I) (Tb 1-Z} Dy z) 1-y (Fe 1-x Co x) y ··· (I) 0 <x ≦ 0.3 0.2 ≦ y ≦ 0.8 0 It is characterized by having a magnetic alloy film satisfying 3 ≦ z ≦ 1.

The magneto-optical medium having the DyTbFeCo type amorphous alloy film of the present invention must have sufficient magnetic anisotropy that the easy axis of magnetization is oriented in the direction perpendicular to the film surface. .. For this purpose, it is first necessary to form the thin film in an amorphous state, and this is achieved by forming the thin film by a sputtering method, a vacuum evaporation method or the like.

Further, by adopting the composition defined by the above general formula (I), the magneto-optical recording medium can have a sufficient magnetic anisotropy and a sufficient Kerr rotation angle.

[0017]

【Example】

Example 1 In a high-frequency sputtering apparatus, a 3 inch square white glass plate was used as a substrate, and a 4 inch φ (Fe _0.70 C
o _0.30 ) Alloys each having 5 mm square Dy pieces and Tb pieces uniformly arranged were used. 1.5x inside the chamber
After evacuation to 10 ⁻⁵ Pa or less, Ar gas was introduced up to 4 × 10 ⁻¹ Pa and the Ar pressure was set to 3 Pa by operating the main valve of the vacuum evacuation system. The film was formed with a sputtering power of 200 W by a high frequency power source. The thus-formed film having a film thickness of 1000 angstrom had an easy axis of magnetization in the direction perpendicular to the film surface, and was confirmed by X-ray diffraction to be amorphous. As a result of composition analysis, this magnetic film was (Dy _0.50 Tb _0.50 ) _0.20 (F
e _0.70 Co _0.30 ) _0.80 , and the Kerr rotation angle was measured with a He-Ne laser with an oscillation wavelength of 633 nm.
It was 0.31 degree. Curie temperature is about 160 ℃
Met. This is the same as Gd _0.25 (Fe _0.70
Co _0.30 ) _0.75 Kerr rotation angle 0.40 degrees, Curie temperature of about 380 ℃, compared with the Kerr rotation angle slightly decreased, it was possible to significantly reduce the Curie temperature.

Examples 2-5 Composition ratios or Dy pieces of the FeCo alloy in Example 1,
Table 3 shows the composition, Kerr rotation angle, and Curie temperature of the magnetic thin films of Examples 2 to 5 formed in the same manner as in Example 1 except that the number of Tb pieces was changed.

[0019]

[Table 3] Thus, the DyTbFeCo-based magnetic film is
Since it contains Dy as compared with Co-based and GdTbFeCo-based magnetic films, it is possible to lower the Curie temperature and the Kerr rotation angle is sufficiently large, so that a magneto-optical recording medium having excellent recording efficiency and reproducing efficiency is provided. be able to.

[0020]

The magnetic film of the amorphous DyTbFeCo alloy used in the magneto-optical recording medium according to the present invention is composed of Dy and C.
Since O is included, the advantage of increasing the Kerr rotation angle due to Co addition is utilized, and the disadvantage of the increase in Curie temperature due to Co addition is offset by the effect of decreasing Curie temperature due to Dy addition, thereby increasing the original Kerr rotation angle. It has become possible to lower the Curie temperature without damaging the temperature. Therefore, the magneto-optical recording medium of the present invention has excellent characteristics in both recording efficiency and reproducing efficiency.

Claims (1)

[Claims] 1. A following formula becomes an amorphous Td-Dy-Fe-Co quaternary alloy having an axis of easy magnetization in a direction perpendicular to the film plane _{(I) (Tb 1-Z} Dy z) 1-y ( Fe _1-x Co _x ) _y (I) having a magnetic alloy film satisfying 0 <x ≦ 0.3 0.2 ≦ y ≦ 0.8 0.3 ≦ z ≦ 1 Magneto-optical recording medium.