JPH0240151A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To increase the Kerr rotating angle thetak on a short wavelength side by forming the recording medium of a specific thin amorphous alloy film having the axis of easy magnetization in the direction perpendicular to the film plane. CONSTITUTION:This recording medium is formed of the thin amorphous alloy film of Pr-R-Fe-Co-M (where R is at least >=1 kinds of Tb and Dy; M is at least >=1 kinds among Ti, Pt, Cr, Ta, and Al) having the axis of easy magnetiza tion in the direction perpendicular to the film plane. Namely, a light rare earth element has the f level near a Fermi plane, unlike from a heavy rare earth element and, therefore, the contribution to the magneto-optical effect by f d transition is expected but the amorphous light rare earth-3d transition metal film does not become a perpendicular magnetized film when the heating of the substrate to about 200 deg.C is not executed during the film formation. Since the heavy rare earths such as Tb and Dy have the effect of enhancing the perpendicular magnetic anisotropy, the thetak on the short wavelength side is in creased by the light rare earths Pr and the perpendicular magnetic anisotropy can be enhanced by the heavy rare earths. The Kerr rotating angle at the short wavelength is increased in this way.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a magneto-optical recording medium that is used for rewritable optical disks and the like, and that can be read using magneto-optic effects such as the magnetic Kerr rotation effect or the Faraday effect. It is related to.

(Prior Art) The following conditions are mainly required for materials for magneto-optical recording media.

a. It must be a perpendicularly magnetized film.

b. Curie temperature is between 100'C and 2000C.

C9 Has a large coercive force.

d. Kerr rotation angle θk is large.

It is known that when heavy rare earth elements such as Tb and Gd are added to Fe, Co, etc., magnetic anisotropy increases and a perpendicularly magnetized film is formed. For these reasons, GdTbFe, DyFe, GdCo, and TbCo are used as materials for magneto-optical recording media.
, TbDyFe.

A heavy rare earth-3d transition metal amorphous alloy thin film such as TbFeCo satisfies the above conditions, is suitable for mass production, and has no read noise, and is therefore considered to be promising. Especially TbFeCo
is seen as promising and is being studied for practical use.

(Problems to be Solved by the Invention) In order to improve the performance of magneto-optical disks, higher recording density is required. In order to increase the recording density, the wavelength of the semiconductor laser used for recording and reproducing magneto-optical disks has been reduced from the current 8.
Progress is being made to further shorten the wavelength from 30 nm. In heavy rare earth-3d transition metal materials such as TbFeCo, as the wavelength becomes shorter, θ gradually decreases. For this reason, when a magneto-optical disk using a heavy rare earth-3d transition metal material such as TbFeCo as a recording medium is recorded and reproduced using a short wavelength laser, the reproduction output is lower than in the past. Therefore, conventional recording media are not suitable as high recording density media.

The present invention has been made in order to solve the conventional problems as described above, and it is an object of the present invention to provide a recording medium that has a larger θ than TbFeCo on the short wavelength side as a medium that can accommodate higher density. .

(Means for solving the problem) Pr-R-Fe with magnetic easy axis in the direction perpendicular to the film surface
-Co-M (provided that M is at least one of Tb and Dy, M is at least one of Ti, Pt, Cr, Ta, and Al). It is characterized by

(Function) Unlike heavy rare earth elements, light rare earth elements have an f level close to the Fermi surface, so they can be expected to contribute to the magneto-optical effect through the f-+d transition. In particular, in light rare earth-3d transition metal amorphous films such as PrFeCo, an increase in θ has been measured on the short wavelength side. However, light rare earth-3d transition metal amorphous films are
If the substrate is not heated to about 200° C. during film formation, a perpendicularly magnetized film will not be formed, and the film cannot be used as it is as a recording medium for a magneto-optical disk using a polymer such as polycarbonate for the substrate.

Heavy rare earths such as Tb and Dy have the effect of increasing perpendicular magnetic anisotropy, so light rare earths Pr increase Ok on the short wavelength side, and heavy rare earths (Tb, Dy) increase perpendicular magnetic anisotropy. Because of this effect, Pr-R-Fe-Co containing both
(However, R is at least one of Tb and Dy.) The present inventors have found that this type of medium is effective as a medium for high recording density. Co is TbF
When Pr is added to e or DyFe, the Curie temperature decreases excessively, so Pr is added for the purpose of increasing it.

The atomic concentrations of Pr, R, Fe, and Co are x, y, and z, respectively.
, w, it is desirable that the following relational expression holds true.

1.00≧XfY+Z+W≧0.95 0.1≦X≦0.5 0.2≦Y≦0.3 0.05 or less (5% or less) of one or more elements of Pt, Ta, Cr, AI, and In
This is because addition is effective in improving the weather resistance of magneto-optical recording media, and addition of 5% or less does not cause a significant deterioration of magneto-optical properties. The number of elements to be added may be one or more. Further, depending on the use of the magneto-optical disk, this additive element may be omitted.

If the Pr concentration is 0.1 or more and 0.5 or less, it is 0.
．． Below 1, the increase in the Kerr rotation angle on the short wavelength side is small;
This is because if it is 0.5 or more, the alloy film will not become amorphous.

As mentioned above, Tb or Dy has the effect of increasing perpendicular magnetic anisotropy. The composition range in which this effect occurs is limited, and in the range of 0.2 or more and 0.3 or less, this amorphous alloy thin film has a large perpendicular magnetic anisotropy and a large coercive force, and this composition range becomes optical. Suitable as a magnetic recording medium. Note that, as the heavy rare earth element, only Tb or only Dy may be added. Further, both Tb and Dy may be added.

Co has the effect of increasing the Curie temperature, which has been lowered by the addition of Pr, Tb, and Dy. By adjusting the Co composition, the Curie temperature can be adjusted to a temperature range (100'C to 200°C) suitable for recording and reproduction.

(Example) A magneto-optical recording medium according to the present invention was formed on a glass substrate by three-pole RF magnetron sputtering. 5mm square Pr on Fe86Co2o target
, Tb, using a composite target with an array of Dy chips,
We created amorphous alloy thin films with varying rare earth compositions. The ultimate degree of vacuum was set to 3×10' Torr or less, Ar was used as the sputtering gas, and the gas pressure was set to 7×10=Torr.

The input power was 300W. The film thickness was set to 10100n. FIG. 1 shows the change in Kerr rotation θ depending on the Pr composition of the sample thus prepared. θ is 500 nm and 900 nm to clearly represent the increase in θ at short wavelengths.
The ratio of nm to θ (Ok(500nm)/θk(900n
m)). With the addition of Pr, there is a clear increase in θ at short wavelengths.

(Effects of the Invention) As described above, the magneto-optical recording medium produced according to the present invention exhibits an increase in the Kerr rotation angle at short wavelengths, and has the effect of being more suitable for high-density recording than conventional magneto-optical recording media. have

[Brief explanation of the drawing]

FIG. 1 shows P in the magneto-optical recording medium according to the present invention.
FIG. 3 is a diagram showing changes in Kerr rotation angle Ok depending on r composition.

Claims (1)

[Claims] (1) Pr-R having a magnetic easy axis in the direction perpendicular to the film surface
-Fe-Co-M (where, R is one or more of Tb and Dy, M is Ti, Pt, Cr, Ta, Al, In
A magneto-optical recording medium comprising an amorphous alloy thin film of at least one of the following. (2) The atomic concentrations of Pr, R, Fe, and Co are
Claim 1 that satisfies the following relationships, where Y, Z, and W: 1.00≧X+Y+Z+W≧0.95 0.1≦X≦0.5 0.2≦Y≦0.3 magneto-optical recording media.