JPH02216637A - 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(SmzGd1-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 1] The present invention relates to a magneto-optical recording medium used for optical alignment, and in particular to a material for a magneto-optical recording layer thereof.

[Prior Art] 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 thereon.
, GdFeCo, or other amorphous heavy rare earth and transition metal amorphous alloy films are used. These films have a Curie temperature of 1
Recording at 00 to 200℃ and using focused 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 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, by increasing the Curie temperature of the recording film, the magneto-optic effect can be increased. However, as the Curie temperature rises, the laser power required for recording and erasing increases. Therefore, in order to improve these drawbacks, a material has been proposed in which a light rare earth element, Sm, is added to a heavy rare earth-iron alloy. (Japanese Unexamined Patent Publication No. 59-178641) With this material, optical reproduction characteristics can be improved without reducing recording sensitivity.

[Problem to be Solved by the Invention 1] However, this material still has the following problems to be improved.

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 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 1 ga 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 m-field sensitivity is desirable. 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 conventional optical 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 for Solving the Problems 1] In the magneto-optical recording medium of the present invention, the recording layer is an amorphous film having an axis of easy magnetization in a direction perpendicular to the film surface, and the composition is expressed in atomic ratio.

fNd, Pr1x fsmxcd+-5ly fFe,
When expressed as Go, Nil 160-X-11, 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 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 %.

[Implementation example 1] The present invention will be described in detail below based on Examples.

(Example 1) (Ndo, 5Pro, sla, o fsmoI
sGdo, 115123. OIFeo, asc.

. 1slff1. A magneto-optical recording medium having an amorphous film having a composition as a recording layer was fabricated using a polycarbonate substrate having a diameter of 120 mm and having spiral guide grooves with a pitch of 1.6 μm. Also, as a comparative example, fsmo, +5
Gdo, ss) 2s, a fFeo, ss(:
Oo, +sl? ? , A record of the composition of o! ! A magneto-optical recording medium having a film was fabricated.

Figure 1 shows one example of NdPrSmGdFeCo (○).
The CN ratio of the magneto-optical recording medium of this example is saturated at about 7000e. In contrast, Nd, P in the comparative example
It takes about 3 to saturate a recording medium that does not contain r.
It can be seen that a bias magnetic field of 000e is required. Also,
The reproduction CN ratio is also about 2 dB higher in the magneto-optical recording medium in the example of the present invention, and the reproduction characteristics are also excellent6 (Example 2) fNdo, gPra, 41 X (Sn+o, l
oGdo, eat 2□, o (Feo, so
c.

. 2ot? a. Magneto-optical recording media were fabricated with a composition of □ while varying the NdPr amount X.

FIG. 2 is a plot of the magnitude of the recording bias magnetic field required to saturate the CN ratio versus N d P r @x. The saturation bias magnetic field decreases as the NdPr amount X increases, reaches a minimum at x=6 (at%), and then increases. On the other hand, as shown in FIG.
The N ratio gradually increases to approximately 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) fNd, Pr 1-ale, o (Srao, +
aGdo, sol **, o (FeI,, so
c.

. 2゜)2. . In the composition, the amount ratio a of Nd and Pr is
Magneto-optical recording media were fabricated by varying the

FIG. 4 shows the magnitude of the recording bias magnetic field necessary for saturation of the CN ratio with respect to N d Ia. The saturation bias magnetic field is smaller than that for Nd only or Pr only over the entire range, and by mixing both Nd and Pr elements, recording and erasing with smaller applied magnetic fields than using each element alone is possible. It can be seen that a large magneto-optical effect can be obtained.

(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.

Table 3 shows the recording bias magnetic field and CN ratio required for saturation of the CN ratio of the magneto-optical recording media of these Examples and Comparative Examples.

The saturation recording bias magnetic fields of the examples of the present invention are all smaller than that of Comparative Example Sample No. 6, and the CN° ratio is equal to or higher than that of Comparative Example Sample No. 6, which does not contain Nd and Pr. ing. Furthermore, the total rare earth ratio is 15
(at%) or more than 40 (at%), S
Although an improvement in the saturation bias magnetic field is observed in both cases where the ratio of m and Gd 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 is accompanied by a significant decrease in the CN 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.

Recording film with SmGdFeCo composition.

[Brief explanation of the drawing]

FIG. 1 shows NdPrSmGdF in an embodiment of the present invention.
eCo film and conventional SmGdFeC. 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 mirror as a recording film. Figure 2 shows 1Nda, 5Pro, 4) If of the present invention.
[5IIC+, +oGdo, eo) as, o
A diagram showing the relationship between the (NdPrl amount X and the saturation bias magnetic field) of a magneto-optical recording medium using (Fe0. Figure 4 shows fNdaPr+-ala. (smo, +oG
da, sol ax. The figure which shows the relationship between Ndla and CN ratio in the composition formula of IFeo, aacrQa, xJ yi, o.

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(SmzGd1-z)y(Fe,Co) in atomic ratio.
, Ni)_1_0_0_-_x_-_y, a magneto-optical recording medium characterized in that, when expressed as 0<x≦10 15≦x+y≦40 0<z≦0.3.