JPH05182265A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To provide a magneto-optical recording medium enough large in Kerr rotation angle, not only able to have reading out in good signal to noise ratio but also high in recording sensitivity and having a proper thermal stability. CONSTITUTION:As a magnetic film of the magneto-optical recording medium, an alloy magnetic film consisting of five elements system (Dy-Gd-Tb-Fe-Co) amorphous allay having an easily magnetized axis at the perpendicular direction to the face of the film, being 190-230 deg.C Curie temp., >=0.3 Kerr rotation angle and satisfying formula {Dy1-z(Gd1-wTbw)z}1-y (Fe1-xCox)y in the formula, 0.2<=x<=0.3, 0.5<=y<=0.9, 0.3<=z<=0.7, 0<=w<=1 is used.

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, it is difficult to use light with high power when reading a signal. ..
If the Curie temperature is low, the writing efficiency is improved, but the written signal is disturbed by the ambient temperature and the reading light. Therefore, the magnetic transformation temperature is preferably 100 ° C. or higher in consideration of thermal stability.

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.

[0009]

[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 research on further 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.

[0013]

[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 not only that the Kerr rotation angle is sufficiently large and that a good S / N ratio can be read out.
An object of the present invention is to provide a magneto-optical recording medium having a high recording sensitivity and an appropriate thermal stability.

[0015]

The magneto-optical recording medium of the present invention which can achieve the above object is an amorphous Dy-Gd-Tb-Fe-Co quaternary system having an easy axis of magnetization in the direction perpendicular to the film surface. The following general formula (I) {Dy _1-Z (Gd _1-w Tb _w ) _z } _1-y (Fe _{1 having an} Curie temperature of 190 ° C. to 230 ° C. and a Kerr rotation angle of 0.3 ° or more is used. _-x Co _x ) _y (I) 0.2 ≦ x ≦ 0.3 0.5 ≦ y ≦ 0.9 0.3 ≦ z ≦ 0.7 0 ≦ w ≦ 1 It is characterized by having.

In the present invention, amorphous DyGdTbFe is used.
When the Curie temperature of the Co quinary amorphous alloy is 190 ° C. or higher, 23 considering the thermal stability of the recorded information in relation to the recording sensitivity.
It is set below 0 ° C.

The magneto-optical medium having the film of the DyGdTbFeCo amorphous alloy 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 high recording sensitivity, appropriate thermal stability and sufficient Kerr rotation angle. ..

[0019]

【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 ) alloy, on which 5 mm square Dy pieces, Gd pieces and Tb pieces were uniformly arranged were used. After evacuating the chamber to 1.5 × 10 ^-5 Pa or less, A
The r gas was introduced to 4 × 10 ⁻¹ Pa and the Ar pressure was set to 3 Pa by operating the main valve of the vacuum exhaust 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 _0.25
Gd _0.25 ) _0.20 (Fe _0.70 Co _0.30 ) _0.80 , and the Kerr rotation angle was 0.37 degrees when measured with a He—Ne laser having an oscillation wavelength of 633 nm. The Curie temperature was about 220 ° C. This is the same as G
Kerr rotation angle of d _0.25 (Fe _0.70 Co _0.30 ) _0.75 0.40
Degree, Curie temperature is about 380 ℃
Although slightly lowered, the Curie temperature could be lowered significantly.

Examples 2 to 5 FeCo alloy composition ratio or Dy piece 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 numbers of Gd pieces and Td pieces were changed.

[0021]

[Table 3]

[0022]

As described above, the magneto-optical recording medium of the present invention has a high recording sensitivity, an appropriate thermal stability, and a sufficient Kerr rotation angle. It is a magnetic recording medium.

Claims (1)

[Claims] 1. An amorphous Dy-Gd-Tb-Fe-Co quaternary alloy having an easy axis of magnetization perpendicular to the film surface, and a Kerr rotation angle of 0. The following general formula (I) of 3 ° or more {Dy _1-Z (Gd _1-w Tb _w ) _z } _1-y (Fe _1-x Co _x ) _y (I) 0.2 ≦ x ≦ 0 A magneto-optical recording medium having a magnetic alloy film satisfying 0.5 ≦ y ≦ 0.9 0.3 ≦ z ≦ 0.7 0 ≦ w ≦ 1.