JPH02216636A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording medium which enables good recording/erasing even in a low bias magnetic field by constituting the recording layer of a specific amorphous metal thin film having the easily magnetizing axis perpendicular to the film surface. CONSTITUTION:The magneto-optical recording medium has the recording layer of an amorphous film having the easily magnetizing axis perpendicular to the surface thereof and the composition expressed by (Nd,Pr)x(Smz(DyGd)1-z)y(Fe, Co, Ni)100-x-y, wherein x, y and z satisfy the formula I. Proportions of the amounts of Fe, Co and Ni can be arbitrarily controlled according to the conditions of recording/erasing for the medium so as to obtain desired values of physical properties such as Curie temp. and compensation temp. However, to obtain a perpendicularly magnetized film, which is the requirement for the magneto-optical recording medium, from the composition above described, it is necessary to make the proportion of total rare earth elements (x+y) in the film in the range from 15at.% to 40at.%. Thus, the obtd. recording medium enables good recording/erasing even in a low bias magnetic field.

Description

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

[Prior Art] Conventionally known optical Iit! The i-recording medium consists of a disk-shaped substrate made of glass or resin having guide grooves and a recording layer formed thereon.
An amorphous alloy film of an amorphous heavy rare earth such as eCo or GdFeCo and a transition metal is used. These films have a Curie temperature of 100 to 200°C, making them suitable for recording and erasing using focused light from a semiconductor laser, and since they are amorphous,
There is no grain boundary noise, which is a drawback of crystalline materials such as MnB1, and light m
It has desirable properties as a black recording material.

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 this magneto-optic effect is extremely small in these materials. It is empirically known that there is a positive correlation with the Curie temperature. Therefore, the magneto-optic effect can be increased by increasing the Curie temperature of the recording film. However, as the Curie temperature rises, 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 Unexamined Patent Publication No. 59-178641) 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 should be improved.

In optical 6R recording, a bias magnetic field is required to record the information. When such a material is used for the recording layer, good recording cannot be performed unless a bias magnetic field of at least 3000e or more is applied around the recording bit.In addition, it is necessary to miniaturize and reduce power consumption of recording and reproducing devices. In order to achieve this, materials that can be recorded and erased in a low bias magnetic field are required. 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, it is desirable to use a recording medium with high m-field sensitivity. In this case, 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 high frequency, if the coil is brought closer to the surface of the medium by several micrometers, 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 the conventional optical 1if1 recording medium, and its purpose is to:

The object of the present invention is to provide a magneto-optical recording medium that can perform good recording and erasing even with a low bias magnetic field.

[Means for Solving the Problems 1] The magneto-optical recording medium of the present invention is such that the recording layer is an amorphous film having an axis of easy magnetization in a direction perpendicular to the film surface, and has a composition in atomic ratio of fNd, Pr. )x fsm*fDyGdl+-! ly
fFe, Go, Ni) When expressed as 100-++-y, it is characterized by the following: 0<x≦10 15≦x+y≦40 0<z≦0.3.

Here, the ratios of Fe, Co, and Ni can be arbitrarily set depending on the recording/reproducing conditions of the medium in order to set physical properties such as Curie temperature and compensation temperature to desired values. However, in this composition system, in order to achieve the perpendicular impurity, 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) fNdo, 5Pro, sl m, o fs, ma
, l! fDyGdl O,ssl *s.

IFeo, ascOo, +8171. A magneto-optical recording medium having an amorphous film with a composition of BN and a thickness of 1.6 μm
Diameter 120mm with pitch spiral guide groove
It was made using a polycarbonate substrate.

In addition, as a comparative example, fsmo, Ill (DyGdl
0.88123゜fFeo, ascOa, +sl
? ? An optical recording medium having a recording film having a composition of , (l) was prepared.

FIG. 1 shows the NdPrSmDyGdF e C of this example.
o (O) and SmDyGdFeC as a comparative example.

(x) indicates the dependence of the reproduction CN ratio on the recording bias magnetic field of a magneto-optical recording medium with a recording film. It can be seen that the CN ratio of the magneto-optical recording medium of this example is saturated at about 7000e, whereas the magneto-optical recording medium of the comparative example that does not contain Nd or Pr requires a bias magnetic field of about 3000e to reach saturation. . Furthermore, the reproduction CN ratio of the magneto-optical recording medium according to the embodiment of the present invention is about 2 dB higher (the reproduction characteristics are also superior).

(Example 2) (Nda, 5Pro, 41 It (Smo, 1o
(DyGdl O, sol z*, o fFeo,
a.

Coo, 20) Magneto-optical recording media were fabricated by changing NdPrNx in the composition qa, o-++. FIG. 2 is a plot of the magnitude of the recording bias magnetic field required for saturation of the CN ratio with respect to NdPrMx. The saturation bias magnetic field decreases as NdPrfix increases, reaches a minimum at x=6 (at%), and then increases. On the other hand, as shown in FIG. 3, the reproduction CN ratio of the magneto-optical recording medium gradually increases to about x=8 (at%) and then rapidly decreases. Taking all of these things into account, if the amount of NdPr is 10 (at%) or less, the reduction in the recording/erasing bias magnetic field, which is the effect of adding NdPr, can be achieved without deteriorating the reproduced signal.

(Example 3) (NdPr addition-Ill S, o (Smo, +o
fDyGdl O,sol *z, o fFeo,
a.

Coo, z. )centre,. In the composition, Nd and Pr
Magneto-optical recording media were fabricated by changing the amount ratio a.

FIG. 4 shows the magnitude of the recording bias 6fl field necessary for saturation of the CN ratio with respect to N d @a.

The saturation bias magnetic field is applied over the entire area in the case of only Nd or in the case of P.
It can be seen that by mixing both Nd and Pr elements, recording and erasing with a smaller applied m field and a larger magneto-optic effect can be obtained than when using each element alone. .

(Example 4) As an example of the present invention, a magnetic film having a recording film having the composition shown in Table 1 was produced.

Furthermore, for comparison, a magneto-optical recording medium having a recording film having the composition shown in Table 2 was prepared.

The recording bias 1if field and CN ratio required for saturation of the CN ratio of the magneto-optical recording media of these examples and comparative examples are
Shown in the table.

The saturation recording bias magnetic fields of the examples of the present invention are all smaller than that of comparative example sample number 6, and the CN ratio is also
A value equal to or higher than that of Comparative Example Sample No. 6 without r is obtained. Furthermore, the ratio of total rare earths is 15 (
at%) or more than 40 (at%), Sm
Although an improvement in the saturation bias magnetic field is observed in both cases where the ratio of (DyGd) and (DyGd) exceeds 3 nia and a large amount of Sm is contained, and when the amount of Nd and Pr exceeds 10 (at%), It can be seen that this is not preferable because it involves a decrease in the CN ratio.

Note that the difference in the ratio of heavy rare earth elements Dy and Gd does not affect the characteristics of the magneto-optical recording medium. Therefore, in this embodiment, the ratio of Dy and Gd is not limited to the same ratio.

Table 1 3 Table 2 [Effects of the invention] As described above, according to the present invention, the C
The saturation bias magnetic field of the CN ratio can be reduced without reducing the N ratio. 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 shows NdPrSmDyG in an embodiment of the present invention.
FIG. 3 is a diagram showing the relationship between the CN ratio and the recording bias magnetic field of a magneto-optical recording medium using a dFeCo film and a conventional SmDyGdFeCo film as a recording film. FIG. 2 shows one of the present invention (Ndo, aPro, al*
fsmafDyGdl o, sol it, o
(A diagram showing the relationship between the (NdPr) amount A diagram showing the relationship.
, l o foycdl O,5azz, of
A diagram showing the relationship between the Nd amount a and the CN ratio in the composition formula Feo, aacOo, aol ts, a. 1- Bias magnetic field (Oe) of NdPrSmDyGdFeCo composition Figure 1 Recording film. Recording film with SmDyGdFeCo composition. Applicant Seiko Epson Co., Ltd. Agent Patent Attorney 1. Masa Homare (1 other person) NdPr amount, X (at%) Figure 2 NdPr amount, X (at%) Nd amount ratio, a

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,Pr)x(Smz(DyGd)1-z)y(in atomic ratio) F
A magneto-optical recording medium characterized in that, when expressed as _1_0_0_-_x_-_y, 0<x≦10 15≦x+y≦40 0<z≦0.3.