JPH02265049A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To allow a good recording and erasing with a low biasing magnetic field by using a thin film consisting of a specific compsn. as an amorphous alloy thin film having the axis of easy magnetization in the direction perpendicular to the film plane. CONSTITUTION:The recording layer is the amorphous alloy thin film having the axis of easy magnetization in the direction perpendicular to the film plane and the compsn. thereof, when expressed by formula I in atomic ratio, is so formed that x, y, z in the formula I attain the values satisfying formula II. The ratios of Fe, Co and Ni in this compsn. can be arbitrarily set in order to maintain the properties, such as Curie temp. and compensation temp., at desired values according to the recording and reproducing conditions of the medium. The compsn. of the formula I is required to have x+y, i.e., the ratio of the entire rare earth in the film within a 15 to 40 atomic % range in order to be a perpendicularly magnetized film which is the essential requirement as the magneto-optical recording medium. The satd. biasing magnetic field of C/N is decreased in this way without lowering the C/N of the magneto-optical recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an optical recording medium used for magneto-optical recording, and particularly relates to the material of its magneto-optical recording layer.

[Prior art 1 A conventionally known magneto-optical recording medium consists of a disk-shaped substrate made of glass or resin having a guide groove, and a recording layer formed on the substrate, and the recording layer includes TbFe, Tb
An amorphous alloy thin film of an amorphous heavy rare earth and a transition metal such as F e CO, G d T l:) F e is used.

These films have a Curie temperature of 100°C to 200°
It is suitable for recording and erasing using convergent light from C and a semiconductor laser, and since it is amorphous, it has desirable characteristics as a magneto-optical recording material since it is free from field noise, which is a drawback of crystalline materials such as MnBi.

However, these materials have the following drawbacks. That is, optical recording of the light E1 is performed using Kerr effect or Faraday effect, but this 6R optical effect is very small in these materials. On the other hand, it is empirically known that the magneto-optic effect has a positive correlation with the Curie temperature of the recording film at the operating temperature. Therefore, by increasing the crystallinity of the record 1 million, the 611 preemptive effect can be greatly enhanced. However, as the Curie temperature increases, the laser power required for recording and erasing increases. Therefore, in order to improve such drawbacks, a material in which a light rare earth element Sm is added to a heavy rare earth iron alloy has been proposed (Japanese Patent Laid-Open No. 59-1.78641). By using this material, optical reproduction characteristics can be improved without decreasing recording sensitivity.

[Problems to be Solved by the Invention] However, this material still has the following problems that need to be improved.

Magneto-optical recording requires a bias magnetic field to record information. When such materials are used for the recording layer,
Good recording cannot be performed unless a bias 6R field of at least 3000e or more is generated around the recording bit. In order to realize miniaturization and lower power consumption of recording/reproducing devices, there is a long-awaited material that allows recording and erasing with a low bias magnetic field. On the other hand, an iiR field modulation recording method has been proposed as a method for realizing overwriting in magneto-optical recording, but even in this method, a recording medium with high IT field sensitivity is desirable. That is, when a conventional magneto-optical recording medium is used, a high voltage is applied to the coil because it is necessary to switch a large magnetic field at high speed. Furthermore, in order to obtain a high magnetic field at a high frequency, if the coil is brought closer to the medium surface by several micrometers, the light E1? Most of the advantages of optical recording as optical memory will be lost.

The present invention solves the problems of conventional optical 611 recording media, and its purpose is to provide a magneto-optical recording medium that can perform good recording and erasing even in a low bias magnetic field. be.

[Means for Solving the Problems] The magneto-optical recording medium of the present invention has a recording layer which is an amorphous thin film having an axis of easy magnetization in a direction perpendicular to the film surface, and whose composition is Prxfsmz (TbGdD, TbGdD, Y) 1-z)y(
Fec.

N i ) +0O−x−y When expressed as O<x≦JO115≦x+y≦40.0
<z≦0.3.

Here, the ratios of Fe, Co, and Ni can be arbitrarily set in order to set physical properties such as the Curie temperature and compensation temperature to desired values depending on the recording and reproducing conditions of the medium. However, in this composition system, in order to obtain a perpendicularly magnetized film, which is a necessary condition for a magneto-optical recording medium, it is necessary that x+y, that is, the ratio of the total rare earth elements in the film, be in the range of 15 at % to 40 at %.

〔Example] The present invention will be described in detail below based on Examples.

(Example 1) Prs, o(Smo2(Tbo3Gdo, a Dyo,
+ ) o, a ) 2s, o (F e O,7COo
3) Light m whose recording layer is an amorphous film with a composition of 70.0
A recording medium was prepared using a polycarbonate substrate with a diameter of 130 mm and having spiral guide grooves with a pitch of 1.6 μm. As a comparative example, (S m o2 (TbG
do5Dyo5)o,a)25.0(Feo.7CO
o, s) A magneto-optical recording medium having a recording film having a composition of 7s, o was prepared.

Figure 1 shows PrSmTbGdDyFeCo (b) of this example and S m T l) G d D y F of the comparative example.
eC.

(♦) shows the dependence of the reproduction C/N ratio on the recording bias magnetic field of the magneto-optical recording medium using the recording film. It can be seen that the reproduced C/N ratio of the medium of this example is saturated at about 1000 e, whereas the medium of the comparative example that does not contain Pr requires a bias magnetic field of about 3000 e.

(Example 2) Pry (Smo, zo (TbGdo5Dyo5)0
．． 80) 211.0 (F eo, ++ocOo2o
) Magneto-optical recording media with a composition of 75.0-X were prepared by varying the amount of Pr (X).

FIG. 2 is a plot of the magnitude of the recording bias magnetic field required for saturation of the C/N ratio against the amount of Pr. The saturation bias recording magnetic field decreases as the amount of Pr increases,
After reaching a minimum at x=6at%, it increases. -Rikitsutsu 3
As shown in the figure, the reproduction C/N ratio of the magneto-optical recording medium is x=6
After gradually increasing to about at%, it rapidly decreases. Taking all of these things into consideration, if the amount of Pr is 10 at % or less, it is possible to actually reduce the recording bias magnetic field, which is the effect of adding Pr, without deteriorating the reproduced signal.

(Example 3) As an example of the present invention, a magneto-optical recording medium having a recording film having the composition shown in Table 1 was prepared. Subscripts x, y, z, p
, q represent the composition ratio in the following composition formula.

Pr, (Smz (Tbo3Gdo3D:Jo4)z
) y (F ep Coq N 11-1'-Q
) +oo-x-y Table 1 Further, for comparison, magneto-optical recording media having recording films having the compositions shown in Table 2 were prepared.

It is shown in Table 3.

Table 2 shows the recording bias magnetic field and C/N ratio required to saturate the C/N ratio of the recording media of these Examples and Comparative Examples. smaller than 11. In addition, the C/N ratio is equal to or higher than that of material No. 11 which does not contain Pr. Furthermore, the ratio of rare earth elements is less than 15 at% or 40
If the ratio of Sm and TbGdDy exceeds 3%, or the ratio of Sm and TbGdDy exceeds 3
．． When it exceeds 7 or when the amount of Pr exceeds 10at%,
Although an improvement in the saturation bias magnetic field is observed in either case, it is found that this is not preferable because it is accompanied by a significant decrease in the C/N ratio.

It should be noted that the present invention should not be considered limited to these examples, and various modifications can be made without departing from the gist of the present invention.

For example, even if the composition ratio of the heavy rare earth elements T1], Gd, and Dy is arbitrary, various characteristics such as the saturation bias limit and the C/N ratio will not be deteriorated.

Furthermore, even if the composition ratio of Fe--Co--Ni, which is a transition metal, is set to an arbitrary value, various characteristics such as the saturation bias 611 field and C/N will not be deteriorated.

[Effects of the Invention] As described above, according to the present invention, the saturation bias magnetic field of the C/N ratio can be reduced without reducing the C/N ratio of the magneto-optical recording medium. Therefore low bias 1
It is possible to provide a high-performance magneto-optical recording medium that can perform good recording and erasing even in the IFT world.

[Brief explanation of drawings]

Figure 1 shows the C/N ratio and recording bias 6 of an optical 6B recording medium in which the PrSmTbGdDyFeCo film of the present invention (b) and the conventional SmTbGdDyFeC film (◆) are used as recording films.
It is a figure showing the relationship of R field. Figure 2 shows Prx (Smo2o (TbGd
. 5D yO,B ) 0.80) 2e,O(F e
Light 61 using o, aoc O0,20) 75.0-8
FIG. 3 is a diagram showing the relationship between the Pr amount X and the saturation bias magnetic field of a 1Q recording medium. FIG. 3 is a diagram showing the relationship between the same <Pr amount X and the C/N ratio. that's all

Claims (1)

[Claims] An amorphous alloy thin film having an axis of easy magnetization in a direction perpendicular to the film surface, the composition of which is Pr_x(Sm_z(TbGdDy)_1_-_z)_ in atomic ratio.
A magneto-optical recording medium characterized in that when expressed as y(FeCoNi)_1_0_0_-_x_-_y, 0<x≦10 15≦x+y≦40 0<z≦0.3.