JPH02216640A - 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(SmzDy1-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 Application Field] The present invention relates to a magneto-optical recording medium used for magneto-optical recording, and in particular to a material for 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.
, 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.
Mn8 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 very small in these materials, while the magneto-optic effect is small at operating temperatures. 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, heavy rare earth
A material in which Sm, a light rare earth element, is added to an iron-based alloy has been proposed. (Unexamined Japanese Patent Publication No. 59-17864) This material makes it possible to improve optical reproduction characteristics without reducing recording sensitivity.

[Problem to be Solved by the Invention 1] However, this material still has the following bending points that should 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 about 3000 e or more is applied around the recording bit. Furthermore, in order to realize downsizing and lower power consumption of recording and reproducing devices, materials that can record and erase data 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 magnetic field sensitivity. , a high voltage is applied to the coil due to the need 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 solves the problems of the conventional optical 6ftft edge medium, 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. There it is.

[Means for Solving the Problems] In the 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.

iNd, Pr1x (SmJy+-5ly fFe,'
Go, Nil When expressed as 1oo-x-y.

0<x≦10 15≦x+y≦40 It is characterized in that 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, so as not to set physical properties such as Curie temperature and compensation temperature to desired values. However, in this composition system, the perpendicular m, 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) INdo, 5Pro, sea, o fsmo,
+5Dyo, asl 23. O(Feo, asc
.

. 181? +. Light E whose recording layer is an amorphous film with the composition
A recording medium was fabricated using a polycarbonate substrate with a diameter of 120 mm and having spiral guide grooves with a pitch of 1.6 μm. In addition, as a comparative example (Smo, l
Jyo, ssl a3. a (Feo, 5scO
o, l alt? An optical 6n recording medium having a recording film having a composition of .

Figure 1 shows the NdPrSmDyFeCo(0) of this example.
This figure shows the dependence of the reproduction CN ratio on the recording bias magnetic field of a magneto-optical recording medium using SmDyFeCo (x) as a recording film as a comparative example. The CN ratio of the magneto-optical recording medium of this example saturates at about 7000e, whereas the Nd, P of the comparative example
A magneto-optical recording medium that does not contain r takes about 300 mL to saturate.
It can be seen that a bias magnetic field of 0e is required. Furthermore, the reproduction CN ratio of the optical recording medium according to the embodiment of the present invention is about 2 dB higher, and the reproduction characteristics are also excellent.

(Example 2) INdo, aPra, 41 X fsmo, l
On! 10. sol 22. OfFeo, soc
.

. 2°), 8°-8, NdPr! Magneto-optical recording media were produced by varying x.

FIG. 2 is a plot of the magnitude of the recording bias m field required for saturation of the CN ratio versus N d P r l x. The saturation bias magnetic field decreases as NdPrjlx increases, reaches a minimum at x = 6 (at%), and then increases to °
increase On the other hand, as shown in FIG. 3, after the reproduction CN ratio of the optical 6n recording medium gradually increases to about x=8 (at%),
Declines rapidly. 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) lNd, Pr l-1)1. o (Srao, +
oDyo, sol**, o fFeo, aoc
.

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

Figure 4 shows the magnitude of the recording bias magnetic field necessary for saturation of the CN ratio with respect to N d l a. 6 The saturation bias magnetic field is smaller over the entire region than in the case of only Nd or only Pr. , it can be seen that by mixing both elements, Nd and Pr, recording and erasing with a smaller applied magnetic 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, the recording bias magnetic field and CN required for saturation of the CN ratio of the magneto-optical recording media of these examples and comparative examples in which magneto-optical recording media having recording films having the compositions shown in Table 2 were fabricated are shown. The ratios are shown in Table 3.

The saturation recording bias magnetic fields of the Examples of the present invention are all smaller than that of Comparative Example Sample No. 6. In addition, 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%), S
Although an improvement in the saturation bias magnetic field is observed in both cases where the ratio of m and Dy 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, the recording film of the SmDyFeCo composition can perform good recording and erasing even in a low bias magnetic field.

It is possible to provide a magneto-optical recording medium with the highest possible performance.

[Brief explanation of the drawing]

FIG. 1 shows NdPr5 m D in an embodiment of the present invention.
y F e Co II and the conventional example SmDyFeC. 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 film as a recording film. Figure 2 shows 1 fNdo of the present invention, aPro, 4) 8 (
Smo, +oDyo, sol tx, o fFe
FIG. 3 is a diagram showing the relationship between (NdPr)ffiX and the saturation bias magnetic field of a magneto-optical recording medium using o, 5ocoa, sol 2+1-X. Figure 3 shows the relationship between the same < (NdPrl amount
oDyo, *ol tz. (Feo, ao(: Oa, zol tx, diagram showing the relationship between N d fi a and the CN ratio in the composition formula a. Applicant: Seiko Epson Corporation Representative Patent Attorney: Masayoshi Kamiyanagi (1st name) 1-・N
Recording film with dPrSmDyFeCo composition. Bias magnetic field (Oe) Figure 1 NdPr1. 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 in a direction perpendicular to the film surface, the composition of which is (Nd, Pr)_x(Sm_zD_y_1_-_z)_ in atomic ratio.
y(Fe, Co, 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.