JPH02265046A - Magnetic-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 x, y, z in formula I are set at the value satisfying formula II when the compsn. is expressed in atomic ratio by the formula I. The ratios of Fe, Co and Ni can be arbitrarily set in order to regulate the properties, such as Curie temp. and compensation temp., to desired values by the recording and reproducing conditions of the medium. However, x+y in the compsn. of the formula I, i.e. the ratio of the entire rare earth in the film are required to be confined in a 15 to 40 atomic % range in order for the compsn. to be the perpendicularly magnetized film which is the essential requirement as the magneto-optical recording medium. The satd. biasing magnetic field of the C/N is lowered 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 optical 6R recording, and particularly to the material of the magneto-optical recording layer.

[Conventional technology]

A conventionally known light 61 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, and the recording layer includes TbFe, TbFeC, etc.
An amorphous alloy thin film of an amorphous heavy rare earth such as O, GdTbFe, and a transition metal is used. These films have a Curie temperature of 100°C or 6,200°C, making them suitable for erasing records using convergent light from a semiconductor laser, and since 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 of 6i. It has desirable properties as a main air recording material.

However, these materials have the following drawbacks. Instant optical 6R optical recording is performed using the Kerr effect and Faraday effect, but the 611 optical 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 Curie temperature of the recording film at the operating temperature. Therefore, by increasing the Curie temperature of the recording film, it is possible to increase the 1ift tip-and-half effect. However, as the Curie temperature increases, 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 Patent Laid-Open No. 59-1.78641). With this material, optical reproduction characteristics can be improved without reducing recording sensitivity.

[Problem to be Solved by the Invention 1] However, the following problems remain in t and IIf that need to be improved.

Magneto-optical recording requires a bias magnetic field to record information. When such materials are 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 bit. In order to realize miniaturization and lower power consumption of recording/reproducing devices, there is a long-awaited material that allows recording and erasing with a low bias magnetic field. On the other hand, a 6R 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 a conventional optical E1 magnetic 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 placed several micrometers closer to the medium surface 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 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 1] The magneto-optical recording medium of the present invention is such that the recording layer is an amorphous thin film having an axis of easy magnetization in the direction perpendicular to the film surface, and the composition is P r x ( Smz Ttll-2)y(F ecoN
I) When expressed as 100-X-y, 0<x≦JO1
It is characterized in that 15≦x+y≦40 and 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, in order to obtain a perpendicularly magnetized film, which is a necessary condition for an optical UI main air recording medium, it is necessary that x+y, that is, the ratio of all rare earths in the film, be in the range of 15 at% to 40 at%. be.

[Example] The present invention will be described in detail below based on Examples.

(Example 1) P r 5.4 (Smo2+T bo79) 266
An optical 6R recording medium having an amorphous film having a composition of (Feo, tCOo, 3)11g as a recording layer was prepared using a polycarbonate substrate with a diameter of 130 mm and having spiral guide grooves with a pitch of 16 μm.

Also, as a comparative example (Smo2T bo7o) 26.6
(Feo7C00,3) A magneto-optical recording medium having a recording film having a composition of 73.4 was prepared.

FIG. 1 shows PrSmTbFeC of this example.

(b) and the recording bias magnetic field dependence of the reproduction C/N ratio of the optical 611 recording medium using SmTbFeCo (◆) as a comparative example as the recording film. The reproduced C/N ratio of the medium of this example is saturated at about 1000e, 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 (Smo, iOT bo, ao) 25
．． 0 (F eo, a.

CO020) Magneto-optical recording media were prepared by varying the Pr amount X in the composition 7s, Q-X.

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 to about at%, it rapidly decreases. Taking all of these things into consideration, if the amount of Pr is equal to or less than ]Oat%, the reduction in the recording bias magnetic field, which is the effect of adding Pr, can be achieved without deteriorating the reproduced signal.

(Example) 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.

Suffix y.

q is the composition ratio in the following composition formula does not represent.

r　X (Sm, Tb (F　e.

co.

i 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: 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: Saturation recording bias 6i Main field of Examples of the present invention: Comparative Example No. 1]. In addition, the C/N ratio is equal to or higher than that of material No. 11 which does not contain Pr. Furthermore, when the ratio of rare earth elements is less than 15 at% or exceeds 40 at%, or when the ratio of Sm and Tb exceeds 3 nia, or when the amount of Pr exceeds 10 at%, the saturation bias magnetic field is Although an improvement is observed, it is found that this is not preferable because it is accompanied by a significant decrease in the C/N ratio.

[Effect of the Invention 1] As described above, according to the present invention, the saturation bias magnetic 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 magneto-optical recording medium that can perform good recording and erasing even with a low bias magnetic field.

C/N ratio and recording bias m of magneto-optical recording medium made of silver film
FIG.

FIG. 2 shows the P r x (Smo2oT bo
, ao)26, o (F e o, goG O0,
20) P of magneto-optical recording medium using 711.0-X
FIG. 3 is a diagram showing the relationship between the r amount x and the saturation bias magnetic field.

FIG. 3 is a diagram showing the relationship between the amount of Pr and the C/N ratio.

that's all Applicant: Seiko Epson Corporation Agent: Patent attorney Kisanbe Suzuki (1 other person)

[Brief explanation of drawings]

Claims (1)

[Claims] An amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface, the composition of which is Pr_x(Sm_zTb_1_-_z)_y(FeCo
Ni) 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.