JPH01258249A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To enable the execution of recording and erasing at a low bias magnetic field by limiting the ratios of the total rear earths in a thin amorphous alloy film which has the compsn. expressed by the prescribed formula and has the axis of easy magnetization perpendicular to the film plane to a prescribed range. CONSTITUTION:The recording layer is formed of the thin amorphous alloy film having the axis of easy magnetization perpendicular to the film plane and the compsn. ratios of the thin amorphous alloy film are specified to 0<x<=10, 15<=x+y<=40, 0<z<=0.3 by atomic ratios when expressed by the formula I. The saturation bias magnetic field of the C/N is thereby decreased without lowering the C/N and the good recording and erasing are enabled even at the low bias magnetic field.

Description

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

[Conventional technology]

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.
, GdTbFe, or other amorphous heavy rare earth metal and transition metal amorphous alloy film is used. These films have a Chierie temperature of 1
Recording at 00-200℃ and convergent light from a semiconductor laser,
MnB is suitable for erasing and is amorphous.
It has desirable characteristics as a magneto-optical recording material without grain boundary noise, which is a drawback of primary crystal materials.

However, these materials have the following drawbacks. That is, in magneto-optical recording, information is reproduced using the Kerr effect or the Faraday effect, but the magneto-optic 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 Chierly 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 Chierie temperature increases, the laser power required for recording and erasing increases. Therefore, in order to improve this drawback, heavy rare earth
A material in which Sm, a light rare earth element, is added to an iron-based alloy has been proposed (Japanese Unexamined Patent Publication No. 1781542/1983). With this material, optical reproduction characteristics can be improved without reducing recording sensitivity.

[The problem that the invention attempts to solve]

However, this material still has some problems that need to be improved as shown below.

Magneto-optical 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 about 5000 e is generated around the recording pits. In order to realize smaller size and lower power consumption of recording and reproducing devices, there is a long-awaited material that can record and erase data in a low bias magnetic field. On the other hand, a magnetic 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 magnetic field sensitivity is desirable. That is, when using a conventional magneto-optical recording medium,
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 medium surface by several micrometers in order to obtain a high magnetic field at high frequency, most of the advantages of magneto-optical recording as an optical memory will be lost.

The present invention is intended to solve 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. It is in.

[Means to solve the problem]

In the magneto-optical recording medium of the present invention, the recording layer is an amorphous thin film having an axis of easy magnetization in a direction perpendicular to the film surface, and has a composition in atomic ratio of Nd, z(SmzTbl-2)y(Fe ,OO,N1)
When expressed as 10(1-,2;-y, mouth<x<10
y15<,,x+yri40,O(z<:(L
It is characterized by being 50.

Here, the ratios of IFe, Oo, and Ni can be arbitrarily set in order to set the physical properties such as Chierly temperature and compensation temperature to desired values depending on the recording and reproducing conditions of the medium.

However, in this composition system, '+'J
e, that is, the ratio of the total rare earth in the film is increased from 15αt% to 40%.
It is necessary to keep it within the range of αt%.

〔Example〕

The present invention will be described in detail below based on Examples (Example 1) Ndao(Smo, 1sTbo, as)zs,o(?e
A magneto-optical recording medium having an amorphous recording layer having the following composition was fabricated using a polycarbonate substrate with a diameter of 120 mm and having spiral guide grooves with a pitch of 1.6 μm. Also, as a comparative example (Smo, zsTba, 5s) 23. o('Peo, 5
A magneto-optical recording medium having a recording film having a composition of s000.15)77.0 was prepared.

FIG. 1 shows the dependence of the reproduction a/N ratio on the recording bias magnetic field of a magneto-optical recording medium in which the recording film was made of NdSmTb1FeOo(·) of the present example and SmTbIFθ0o(-) of the comparative example. It can be seen that the O/N ratio of the medium of this example saturates at about 10,000, whereas the medium that does not contain Nd of the comparative example requires a bias magnetic field of about 300 oe to saturate. The value of the /N ratio is also approximately 2 dB higher in the example of the present invention, and the reproduction characteristics are also excellent.

(Example 2) Nd, (SmoloTbo, 5o)22. o (reo
, aoo□1lL2o)ys,ox, magneto-optical recording media were prepared by varying the Nd amount X.

FIG. 2 is a plot of the magnitude of the recording bias magnetic field required to saturate the O/N ratio against the Nd amount X.

The saturation bias magnetic field decreases with increasing Ndi, x;6
After reaching the minimum at (06%), it increases. On the other hand, as shown in Figure 3, the reproduction 0/N ratio of the magneto-optical recording medium is x=
After increasing to about 8 (06%), it suddenly decreases. Taking all these things together, %Ndi is 10αt%
If it is below, the reduction in the recording bias magnetic field, which is the effect of Nd addition, can be achieved 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.

Further, for comparison, magneto-optical recording media having recording films having the compositions shown in Table 2 were prepared.

Table 3 shows the recording bias magnetic field and O/N ratio required for saturation of the O/N ratio of the recording media of these Examples and Comparative Examples.

Table 1 Table 2 Table 3 The saturation recording bias magnetic fields of the examples of the present invention are all smaller than that of the comparative example Nα11. Moreover, the o/N ratio is equal to or higher than that of the Nα11 sample containing no Nd. Furthermore, if the ratio of rare earths is less than 15αt% or exceeds 40αt%, or the ratio of Sm and Tb is 3
When Nd#L exceeds 7 or when Nd#L exceeds 10αt%, an improvement in the saturation bias magnetic field is recognized in both cases, but it is found that this is not preferable because it is accompanied by a significant decrease in the 0/N ratio [Invention Effects] As described above, according to the present invention, the saturation bias magnetic field of the O/N ratio can be reduced without reducing the O/N ratio of the magneto-optical recording medium. Therefore, it is possible to provide a high-performance magneto-optical recording medium that can perform good recording and erasing even with a low bias magnetic field.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the a/N ratio and the recording bias magnetic field of magneto-optical recording media in which the recording film is the NdSmTb"Fe0OIJ (•) of the present invention and the conventional SmTbFe0o film (theory). The figure shows the Ndr(SmO, 10TM, 90)2 of the present invention.
2.0 (Feo, a. 00G, 20) 78.0-□ is a diagram showing the relationship between the amount of N d and the saturation bias magnetic field of the magneto-optical recording medium. This is a diagram showing the relationship between t and G/N ratio. Applicant Seiko Epson Co., Ltd. Agent Patent attorney Masayoshi Kamiyanagi (and one other person) Figure 2

Claims (1)

[Claims] An amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface, the composition of which is Nd_x(Sm_zTb_1_-_z)_y(Fe,C
o, Ni)_1_0_0_-_x_-_y A magneto-optical recording medium characterized in that 0<x≦10 15<x+y≦40 0<z≦0.3.