JPH02265047A - 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 Application Field] The present invention relates to a magneto-optical recording medium used for magneto-optical recording, and particularly to the material of the magneto-optical recording layer.

[Prior Art] A conventionally known optical 6R 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.
, GdTbFe, and other amorphous alloy thin films of amorphous heavy rare earths and transition metals are used. These films have a Curie temperature of 100°C to 200°C, making them suitable for erasing records using convergent light from a semiconductor laser, and because they are amorphous, they do not have grain boundary noise, which is a drawback of crystalline materials such as MnB1, and can be used with light. It has desirable properties as a magnetic recording material.

However, these materials 4 have the following drawbacks. That is, magneto-optical recording is performed using the Kerr effect and Faraday effect, but these materials have very small magneto-optic effects. 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, the magneto-optic effect can be increased by increasing the Curie temperature of the recording film. However, as the Curie temperature increases, the laser power required for recording and erasing increases. In order to improve these 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 Application Laid-Open No. 178641/1983). With this material, optical reproduction characteristics can be improved without reducing recording sensitivity.

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

Optical LiR recording requires a bias magnetic field to record information. When such a material is used for the recording layer, good recording cannot be performed unless a bias magnetic field of at least 3000 e or more is generated around the recording pits. In order to realize downsizing and lower power consumption of recording and reproducing devices, there is a long-awaited material that can perform recording and erasing in a low bias 6R field. On the other hand, an FFI field modulation recording method has been proposed as a method for realizing overwriting in optical 6R recording, but even if this method is used, a recording medium with high 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, if the coil is brought closer to the surface of the medium by several micrometers in order to obtain a high magnetic field at a high frequency, most of the advantages of magneto-optical recording as an optical memory will be lost.

The present invention solves the problems of conventional magneto-optical 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. .

[Means for Solving the Problems] The optical recording medium of the present invention has a recording layer that is an amorphous thin film having an axis of easy iiR in the direction perpendicular to the film surface, and whose composition is PrX ( Smz (TbDy)+-zly(FeCo
Ni), 0<x≦10.15≦x+y≦4
0, O<z≦03.

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, the perpendicular 6R, which is a necessary condition for a magneto-optical recording medium,
In order to form a chemical film, it is necessary that x+y, that is, the ratio of all 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(Tbo5I)yo,s)
o, a) 26.0 (Feo7CO0,3) An optical recording medium having an amorphous film with a composition of TO as a recording layer,
A polycarbonate substrate having a diameter of 130 mm and having spiral guide grooves with a pitch of 1.6 μm was used.

Also, as a comparative example (S m o2 (T bo5D yo5
) o, a ) 26.0 (F eo7CO0,3)
An optical 6R recording medium having a recording film having a composition of 74° was prepared.

FIG. 1 shows PrSmTbDyFeC of this example.

(B) and Comparative Example SmTbDyFeCo (◆) The dependence of the reproduction C/N ratio on the recording bias magnetic field of the magneto-optical recording medium with the recording film (◆) is shown. The reproduced C/N ratio of the medium of this example is saturated at about 1500e, whereas the medium not containing Pr of the comparative example is saturated at about 3000e.
It can be seen that a bias magnetic field of e is required.

(Example 2) P r X (Smo2o (T bo5D yo5)
o, eo) 2s, o (Feo, aoCOo, zo)
Magneto-optical recording media were prepared by varying the Pr amount X in the compositions ts and ox.

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=4at%, 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 by about at%, it suddenly decreases. Taking all of these things into account, if the amount of Pr is 10 at % or less, it is possible to reduce the main field of recording bias, 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 X (Sm2 (Tbo5Dyo5)+-z)
y(F e p COq N 1 +−++−q )
Ioo-ni-1' 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 Table 3 shows the saturation recording bias and fi field of the Examples of the present invention. , smaller than 11. In addition, the C/N ratio is equal to or higher than that of the material No. 1 which does not contain Pr. Furthermore, if the ratio of rare earths is less than 15 at% or exceeds 40 at%, or the ratio of Sm and TbDy is 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 heavy rare earth elements Tb-Dy is arbitrary, various characteristics such as the saturation bias magnetic field and the C/N ratio will not be deteriorated.

Furthermore, even if the composition ratio of the transition metals Fe--Co and Ni is arbitrary, various characteristics such as the saturation bias magnetic field and the C/N ratio will not be deteriorated.

[Effects of the Invention] As described above, according to the present invention, the saturation bias 6R field of the C/N ratio can be reduced without reducing the C/N ratio of the magneto-optical recording medium. Therefore, it is possible to provide a high-performance optical recording medium that can perform good recording and erasing even with a low bias magnetic field.

[Brief explanation of drawings]

FIG. 1 shows the P r S m T I) D y of the present invention.
Fe Co film (b) and conventional SmTbDyFeCo
FIG. 3 is a diagram showing the relationship between the C/N ratio and the recording bias magnetic field of a magneto-optical recording medium in which a film (♦) is used as a recording film. FIG. 2 shows the P rx (Smo, +o (T
bo5D, Y o, s ) 0.80) 25.0
FIG. 3 is a diagram showing the relationship between Prrx and the saturation bias magnetic field of a magneto-optical recording medium using (F e o, aoc OO, 20)76,0-X. FIG. 3 is a diagram showing the relationship between the same <Pr1iLx 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(TbDy)_1_-_z)_y( in terms of atomic ratio).
A magneto-optical recording medium characterized in that when expressed as FeCoNi)_1_0_0_-_x_-_y, 0<x≦10 15≦x+y≦40 0<z≦0.3.