JPS60107751A - Photothermomagnetic recording medium - Google Patents

Abstract

PURPOSE:To improve recording efficiency and reproducing efficiency with a photothermomagnetic recording medium formed with a recording layer consisting of a thin film of an amorphous magnetic alloy having the axis of easy magnetization in the direction perpendicular to the film plane on a base plate by selecting the amorphous magnetic alloy from GdDyFeCo, TbDyFeCo or GdTb-DyFeCo. CONSTITUTION:An amorphous magnetic alloy selected from GdDyFeCo, TbDyFeCo or GdTbDyFeCo is used with a photothermomagnetic recording medium formed with an amorphous magnetic alloy layer having the axis of easy magnetization in the direction perpendicular to the film plane on a base plate. Fe and Co exist preferably in the range of 50-90atm% in the total amt. thereof as the compsn. to provide substantial magnetic anisotropy for directing the axis of easy magnetization in the direction perpendicular to the film plane with such photothermomagnetic recording medium. Said amt. is more particularly preferably 70-85atm%. Co exists preferably by >=0.5atm% with respect to Fe in order for the Kerr rotating angle to attain the value substantially larger than the value by the conventional constituting elements. The film is formed by a sputtering method or vacuum deposition method in order to constitute the amorphous thin film.

Description

[Detailed Description of the Invention] This invention relates to a photothermal magnetic recording medium used for
In particular, the present invention relates to a photothermal magnetic recording medium that can be read using magneto-optical effects such as the magnetic Kerr effect or the Faraday effect.

Conventionally, MnBi, Mn-
Polycrystalline thin film such as CuBi, GdCo, GdFe, T
bFe.

Amorphous thin films such as DyFe, GdTbFe, and TbDyFe, and single crystal thin films such as GdIG are known.

Among these thin films, the film-forming ability of producing a large-area thin film at a temperature close to room temperature, the writing efficiency for writing signals with light thermal energy, and the ability to read the written signals with a good S/N ratio are important. In consideration of read efficiency and the like, the amorphous film is recently considered to be excellent as a photothermal magnetic recording medium.

However, various drawbacks have been pointed out in these amorphous thin films as well. For example, GrlFe has a small coercive force and recorded information is unstable. Also, GdFe, G
dCo performs writing using a magnetic compensation point, and 7:C cannot be achieved unless the film composition is strictly controlled during film formation in order to make the writing efficiency uniform. TbFe,D
For yFe and TbDyFe, the film composition is not so strictly controlled because the Gyuri single point is applied, but because the Cure single point is low at less than 100 degrees Celsius, it is said that it is not possible to use strong light when reading out signals. There are some difficulties.

If the Curie temperature is low, the writing efficiency will improve, but the written signal will be disturbed by the ambient temperature or read light. Therefore, considering the usage conditions, the magnetic transformation temperature is preferably 100° C. or higher. The readout S/N by reflected light is proportional to IK-fjk, where R is the reflectance and θ is the Kerr rotation angle. Therefore, in order to read with a good S/N ratio, the Kerr rotation angle may be increased.

Table 1 shows the Kerr rotation angle of the amorphous magnetic film.

Table 1 Among these, GdTbFe has the largest Kerr rotation angle.

However, even this value was still not sufficient, and as a result of research to further increase the Kerr rotation angle, GdFe
or Gd Fe Co , which is TbFe with Co added.

TbFeCo has a large Kerr rotation angle, especially GdTb
A quaternary amorphous magnetic alloy of GdTbFeCo, which is made by adding Co to Fe, has excellent thermal stability, has a sufficiently large Kerr rotation angle, and is a photothermal magnetic recording medium that enables readout with a good S/N ratio. I found out.

Thus, it can be seen that in conventional rare earth-transition metal based amorphous magnetic alloys, systems containing Fe and Co as transition metals increase the Kerr rotation angle.

However, systems containing CO increase the Curie temperature. Table 2 shows the Kerr rotation angle and Curie temperature of TbFeCo and GdFeCo.

Table 2 By adding Co in this way, it is possible to increase θk, but since the Curie temperature also increases,
Recording sensitivity decreased significantly.

The object of the present invention is to have a sufficiently large Kerr rotation angle and
The object of the present invention is to provide a photothermal magnetic recording medium that not only allows reading with a good N ratio but also has an appropriate Curie temperature value.

The photothermal magnetic recording medium of the present invention is a photothermal magnetic recording medium in which an amorphous magnetic alloy layer having an axis of easy magnetization perpendicular to the film surface is formed on a substrate, wherein the amorphous magnetic alloy is GdD.
yFeCo, TbDyFe0off, if GdT
bDyFeC.

It is characterized by being selected from.

In the photothermal magnetic recording medium according to the present invention, the composition of Fe and Co is 1' fi as a composition that provides sufficient magnetic anisotropy to orient the axis of easy magnetization in the direction perpendicular to the film surface.
It is desirable that ``i'' exists in the range of 50 atom % to 90 atom %. Particularly preferably 70 atom % to 85 atom %
It is.

Furthermore, in the photothermal magnetic recording medium according to the present invention,
In order for the Kerr rotation angle to be sufficiently larger than the value due to conventional constituent elements, it is desirable that Co be present in an amount of 0.5 atomic % or more relative to Fe.

GdDyFeCo, TbDyFe0o, G of the present invention
The dTbDyFeCo amorphous alloy photothermal magnetic recording medium must have sufficient magnetic anisotropy so that the axis of easy magnetization is oriented perpendicular to the film surface. For the mouth, it is first necessary to form a thin film of amorphous material, and this is accomplished by forming the thin film by a sputtering method, a vacuum evaporation method, or the like. The composition to have sufficient magnetic anisotropy and sufficient Kerr rotation angle is (Dy+-zAz)+-y(Fe+-XcoX)y
\ and A is Gd, Tb, or (Gd + - wTbw
), then X, Y, Z and W are 0.005≦X<1.0.5≦Y≦09, 0≦Z<
1. It is desirable that O≦W≦1.

Example 1 In a high-frequency sputtering device, a 3-inch square white glass plate was used as a substrate, and a 4-inch f (Fe 0,
70 Co o, ao) Five square Dy on the alloy,
Gd pieces with a viewing angle of 5 were uniformly arranged. Inside the chamber 1. ．． After evacuation to 5×10′ Pa or less, Ar gas was introduced to 4×10 −′ Pa, and the Ar pressure was brought to 3 Pa by operating the main valve of the vacuum evacuation system. 200W from high frequency power supply
The film was formed with a sputtering power of . The film thus formed with a thickness of 1000 mm had an axis of easy magnetization in the direction perpendicular to the film surface, and was confirmed by X-ray diffraction to be amorphous. Moreover, as a result of compositional analysis, this magnetic film is (DNl
o,50Gd O,50) 0.28 (Fe 007
0 Co o, 8o)0. ? ? The Kerr rotation angle was 0.38 degrees when measured using a He--Ne laser with an oscillation wavelength of 633 nm. Moreover, the cucumber temperature was about 300°C. This is the Gd created in the same way.
0125 (Fe 0,70 Co o, go )
0.75 Kerr rotation angle 0.40 degrees, cucumber temperature approx. 3
Although the Kerr rotation angle was slightly lower than that at 80°C,
We were able to significantly lower the cucumber temperature.

Example 2. ~6 Composition ratio and D'l, Gd of 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 6, which were formed in the same manner as in Example 1 except that the number of pieces was changed.

Table 3 By changing the amount of Co with respect to Fe in this way, Kerr rotation angles with various values of different y'z can be obtained, and the values are much lower than those of the conventional GdTbFe system. There were also values that were much larger and almost similar to those of the GdFeCo system. Also, compared to the Curie temperature of the GdFeCo system,
Because it contains Dy, it has become possible to lower the cucumber temperature.

Examples 7 to 16 The same procedure as in Example 1 was carried out except that the 5-square Tb piece or the Tb piece and the Gd piece were arranged together with the Dy piece on the various Fe Co alloy targets in Examples 1 to 3. The compositions, Kerr rotation angles, and Curie temperature of the thin films of Examples 7 to 16 prepared by the method are as shown in Table 4.

Table 4 In this way, DyTbFeCo system, DyTb Gd Fe
Co-based magnetic films include TbFeCo-based, GdTbFeCo-based
Since it contains Dy compared to other magnetic films, it is possible to lower the Curie temperature, and the Kerr rotation angle is also sufficiently large, making it possible to provide a photothermal magnetic recording medium with excellent recording efficiency and reproduction efficiency. .

DyGdFeCo, DyTbFeCo, which are non-quality magnetic alloys used in the photothermal recording medium according to the present invention,
In Dy-Tb Gd Fe Co, Dy,!
l: C because it contains CO.

The advantage of increasing the Kerr rotation angle due to addition, and the disadvantage of increasing the Curie temperature due to Co addition, are offset by the decrease in Curie tm due to the addition of Dy. It became possible to lower the Therefore, the photothermal magnetic recording medium of the present invention has excellent characteristics in both recording efficiency and reproduction efficiency.

Claims (1)

[Scope of Claims] (]) A photothermal magnetic recording medium in which a recording layer consisting of a thin film of an amorphous magnetic alloy having an axis of easy magnetization perpendicular to the film surface is formed on a substrate (= where the amorphous The magnetic alloy is GdDy
FeCo, TbDyFeCo or GdTb-DyF
A photothermal magnetic recording medium characterized in that it is selected from eCo. (2) The total amount of Fe and Co in the amorphous alloy is 5
The photothermal magnetic recording medium according to claim 1, which has an atom density of 0 to 90 atoms.