JPS6231048A - Photomagnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a magneto-optical recording medium used in magneto-optical memories, magneto-optical recording display elements and the like.

``Prior art'' Circular acid has an axis of easy magnetization perpendicular to the film surface and is used as a magneto-optical memory or magneto-optical recording display element. Circular acids record information by creating reversed magnetic domains of arbitrary shapes, and can be used as magnetic cards. Thin-film magneto-optical recording media are used that read recorded information using magneto-optic effects.

In general, in a ferromagnetic thin film whose axis of easy magnetization is perpendicular to the film surface, by irradiating it with a light beam such as a laser, it is possible to uniformly magnetize the S or N pole in the film surface. Small reversal magnetic domains with uniform magnetization polarity and opposite magnetic poles can be created within the irradiated area. The presence or absence of this reversed magnetic domain is "1".

By recording information in correspondence with "0", such a ferromagnetic thin film can be used as a high-density magnetic recording medium. Information recorded in this manner can be read using the magneto-optic effect.

Among these ferromagnetic thin films, thin films that have a large coercive force at room temperature and whose Kiley temperature or magnetic compensation temperature is relatively close to room temperature are those that have a Kiley temperature or magnetic compensation temperature that is relatively close to room temperature. It is used as a beam-addressable file because information can be recorded by creating an inverted magnetic domain at an arbitrary position using a light beam.

Conventional ferromagnetic thin films that have an axis of easy magnetization perpendicular to the film surface, are capable of high-density magnetic recording, and can be used as beam-addressable files include polycrystalline metal thin films such as MnB1, and Gd-Tb-F'e.

Dy-Fe, Tb-Fe, Tb-Fe-C
Multi-component amorphous metal thin films such as O, etc. or compound single crystal thin films typified by GIG are used. Each of these ferromagnetic thin films that can be used as a beam addressable file has advantages and disadvantages as described below.

That is, a polycrystalline metal thin film typified by MnB1 is excellent as a magnetic recording medium in that writing is performed using the Curie temperature and has a large coercive force of several koe.

However, since the temperature is high, for example, Tc=360° C. for MnB1, it has the disadvantage that a large amount of energy is required for writing.

Furthermore, since it is a polycrystalline material, it is necessary to create a thin film with a composition that satisfies stoichiometric conditions, and its production is technically difficult.

Furthermore, compound single crystal thin films, such as GIG, have a high Curie temperature and require a large amount of energy for writing, and are significantly more expensive to manufacture than other films due to material or manufacturing technology. The problem is that it increases.

A rare earth-transition metal amorphous thin film has been proposed as a solution to the various problems in the characteristics of these polycrystalline metal thin films or compound single crystal thin films as magneto-optical recording media.

The composition of this rare earth-transition metal amorphous thin film is Tb-Fe, DY-Fe + Gd-Tb-Fe
, Tb-Fe-C.

Amorphous thin films with multicomponent compositions have been proposed.

These proposed rare earth-transition metal amorphous thin films are
Since the Keely temperature is as low as 60° C. to 200° C., it is possible to write using the Keely temperature, and it has a large coercive force of several koe over a wide composition range under room temperature conditions.

Further, when used as a recording medium, it is not necessary to create an amorphous thin film under particularly high-precision manufacturing conditions in terms of composition, and the manufacturing technology is relatively easy, resulting in a high production yield.

``Problems to be Solved by the Invention'' As described above, the rare earth-transition metal amorphous thin film has a large coercive force over a wide range of compositions, can be written using Kz'J humidity temperature, is 6D, and is It has the advantage that the manufacturing technology is relatively easy and the manufacturing yield is good.

However, Tb, which is conventionally used as an important compositional metal element in rare earth-transition metal amorphous thin films, has an extremely small amount of 0.9xy/l on earth, and its supply is limited due to resource constraints. As a result, there are difficulties in terms of supply price.

The present invention aims to solve the problem of the limited supply of Tb used as a rare earth metal in rare earth-transition metal amorphous thin films and the associated supply price. In this invention, the total composition ratio conditions of the Gd-Pr-Fe-based amorphous alloy thin film are set, and the recording bits are stable, excellent in magneto-optical recording characteristics, and manufacturing costs can be reduced. A magnetic recording medium can be provided.

"Structure of the Invention" The magneto-optical recording medium of the present invention is an amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface.
It is expressed as d1-XPrX)YFel-Y and has a composition in which X is 3 to 14 atoms and Y is 24 to 30 atoms.

"Embodiments of the Invention" Hereinafter, the magneto-optical recording medium of the present invention will be described in detail with reference to the drawings based on the embodiments and the manufacturing method thereof.

As already mentioned, Tb, which is mainly used as a rare earth element in magneto-optical recording media made of rare earth-transition metal amorphous thin films, has an abundance on earth of 0,9
The amount of tfI/l is extremely low, and there is a resource problem in terms of supply amount.

On the other hand, Gd, which the inventors focused on, has an abundance of 6.3611/l, which is more than 60 times that of Tb, which solves the supply problem in terms of resources and eliminates the difficulty in terms of price. It is possible to solve it.

However, Gd−, which is composed of Gd as a rare earth metal element,
As a result of actual measurements by the inventors, magneto-optical recording media such as Fe, etc.
T whose coercive force is composed of Tb as a rare earth metal element
It has the disadvantage that it is smaller than magneto-optical recording media such as b-Fe and lacks stability of recording bits.

The inventors solved this problem regarding the coercive force of the magneto-optical recording medium, proceeded with research to increase the coercive force, and developed a new method by using Pr together with Gd as a rare earth metal element in the magneto-optical recording medium. It was confirmed that the coercive force of the resulting magneto-optical recording medium was improved.

In this case, it is thought that by adding the light rare earth element Pr, the structure of the magneto-optical recording medium changes and the coercive force increases. The inventors have confirmed that a similar tendency is obtained when pr is added to, for example, a Tb-Fe based magneto-optical recording medium.

The magneto-optical recording medium of the present invention is composed of a ternary amorphous alloy thin film of Gd-Pr-Fe, and has an axis of easy magnetization in a direction perpendicular to the film surface. In order to provide a magneto-optical recording medium with sufficient magnetic anisotropy to orient the magnetization direction perpendicular to the film surface, it is necessary to form the film surface as thick as possible. For this reason, in the present invention, the thickness is, for example, 0.3 m.
An amorphous alloy thin film having a thickness of several hundred times or more is formed on this substrate by a so-called dry manufacturing method such as a sputtering method or a vacuum evaporation method.

When using a dry manufacturing method such as vacuum evaporation or sputtering, it is possible to form a metal thin film by obliquely injecting the constituent atoms into the substrate in order to improve the coercive force (Japanese Patent Application No. 1986- 129335).

Also in this invention, when creating an amorphous alloy thin film,
A method can be used in which the constituent atoms are incident obliquely onto the substrate.

When creating a magneto-optical recording medium, when constituent atoms are incident obliquely onto a substrate, an acicular thin metal film structure grows with the crystal orientation direction being oblique to the substrate. When a magneto-optical recording medium is created in such a state, the orientation and shape anisotropy of the crystals are the cause of the magnetic anisotropy characteristics, and the increase in magnetic anisotropy causes the magneto-optical recording medium to deteriorate. It becomes possible to improve coercive force.

For example, a magneto-optical recording medium in the form of a thin film is prepared on a soda glass substrate having a thickness of 0.3 fm by using a targut having a composition approximately equal to that of the film, by a four-layered splattering method. In this case, the production atmosphere is an atmosphere using argon gas as an inert gas, and the atmospheric pressure is maintained at 3 to 8 Pa.

In this case, in order to create a thin film with sufficient magnetic anisotropy to have an axis of easy magnetization in the direction perpendicular to the film surface, it is necessary to cool the substrate with water to keep the substrate temperature low. In the example, a magneto-optical recording medium was prepared by forming an amorphous alloy thin film to a thickness of about 1000X on a soda glass substrate under such an atmosphere with a supplied power of 50W.

In this invention, when the composition of the ternary amorphous alloy thin film of Gd-Pr-Fe is expressed as (Gd, -xPrx)yFe1-Y, the results of research by the inventors show that the respective atomic ratios X, For Y, 0.03<X≦0.14, 0.
24≦Y: It was confirmed that a row group value of <0.30 is necessary.

Generally, in a rare earth-iron amorphous film, the magnetic moment due to the rare earth element determined by the composition ratio of the rare earth element and the magnetic moment due to the iron element determined by the composition ratio of the iron element cancel each other out. The overall saturation magnetization Ms is determined.

Therefore, by setting the ratio of rare earth elements and ferrous elements in the total composition, the magnetic anisotropy constant is Kn)
A saturation magnetization Ms that satisfies the perpendicular magnetization condition of 2πMg can be obtained. If a composition satisfying the perpendicular magnetization condition is obtained in this manner, a magnetic thin film having an axis of easy magnetization perpendicular to the film surface can be obtained.

The total composition ratio in this invention is (Gd 1- XP r
As a result of research by the inventors, in the magneto-optical recording medium represented by
It was confirmed that there is a predetermined condition on the composition ratio of the -Pr binary system composition.

According to the results of research conducted by the inventors on the composition of the Gd-Pr binary system, the atomic ratio X of Pr in the Gd-Pr binary system composition is 0.03) In this case, the coercive force and magnetic anisotropy of the rare earth-iron amorphous thin film decrease. Such characteristics are undesirable when a magneto-optical recording medium is used as a beam-addressable file using an optical beam, and must be avoided during production.

Even if the atomic ratio of the total of the binary composition of Gd and Pr to the total composition of the ternary amorphous alloy thin film is 1c, according to the results of research and study by the inventors, Y(0,24 or Y)0. 30, a similar decrease in the coercive force of the rare earth-iron amorphous thin film is observed. In this state, it becomes impossible for the rare earth-iron amorphous thin film to maintain recording, and furthermore, it becomes impossible to have an axis of easy magnetization in the direction perpendicular to the film surface.

On the other hand, it is composed of a rare earth-iron amorphous thin film in which the total atomic ratio Y of the Gd-Pr binary composition to the total composition satisfies the composition range of 0.24<Y≦0,29. The Kerr hysteresis loop obtained with the magneto-optical recording medium has a square shape. In a magneto-optical recording medium having a square-shaped Kerr hysteresis loop, it is possible to form a certain anti-axial magnetic domain in a predetermined magnetic field, and desirable characteristics as a magneto-optical recording medium can be obtained.

□ −1−−2;
I1, )] 1 to 1 In Table 1, the composition, coercive force) (c (KOe), and Kerr rotation angle θK (deg)) of each sample are assigned sample numbers 1 to 12 and are shown by the inventors. These are examples of magneto-optical recording media of the present invention prepared by and comparative examples for reference.

In the comparative example shown as sample number 9, the total production ratio of the magneto-optical recording medium was (Gd[180PrO, 20)1121FeQ, 7?
It is expressed as, X=0.20 Y=0.21 and
This is a case where Y exceeds the upper limit of the composition range of the present invention and Y does not reach the lower limit of the composition range of the present invention. In this comparative example, the coercive force He is 0.1 (KOe) and the Kerr rotation angle θK is 0.12 (deg), so that sufficient characteristics as a magneto-optical recording medium cannot be obtained.

In the comparative example shown in sample number 10, the magneto-optical recording medium had a total composition ratio of (Gd1.(IQPr[100)(155"0.
67, X=0, Y=0.33,
Y does not reach the lower limit of the composition range of this invention, and Y exceeds the upper limit of the composition range of this invention. In this comparative example, the coercive force He is 0.3 (KOe) and the Kerr rotation angle θK is 0.23 (deg), so that sufficient characteristics as a magneto-optical recording medium cannot be obtained.

In the comparative example shown in sample number 11, the total composition ratio of the magneto-optical recording medium was (Gd1.00Pra00)[126Fe[174
This is the case where X=0 and Y=0.26, where Y is within the composition range of the present invention but X does not reach the lower limit of the composition range of the present invention. The magneto-optical recording medium of this comparative example has a coercive force He of 0.1 (KOe) and a Kerr rotation angle θ
When K is 0.25 (deg), sufficient characteristics as a magneto-optical recording medium cannot be obtained.

In the comparative example shown in sample number 12, the total composition ratio of the magneto-optical recording medium was (Gd1198PrQ,02)[125Fe(17
5, X=0.02, Y=0.25, Y is within the composition range of the present invention, but X does not reach the lower limit of the composition range of the present invention. In this comparative example, the coercive force He is 0.1 (KOe) and the Kerr rotation angle θK is θ
K = 0.28 (deg), and sufficient characteristics as a magneto-optical recording medium cannot be obtained.

The magneto-optical recording media shown in sample numbers 1 to 8 are examples of the present invention, and both X and Y are within the composition range of the present invention. In each of these examples, the coercive force He
is in the range of 0.2 to 1.3, and the Kerr rotation angle θ3 is in the range of 0.20 to 0.36, so that sufficient characteristics as a magneto-optical recording medium can be obtained.

Figure 1 (A) and (B) are sample number 1 in Table 1, respectively.
and 2 are the results of Kerr hysteresis loop measurements conducted by the inventors for Example 2. Figure 1 (4) (B)
, the vertical axis is the Kerr rotation angle θ)C (deg), and the horizontal axis is the magnetic field H (KOe). In the example of sample number 1, the coercive force Hc is 1.1 (KO
In e), the Kerr rotation angle θK is 0.2 s (deg), and the loop has a rectangular shape. Also in the example of sample number 2 shown in FIG. 1(B), the coercive force He was 1.1 (KO
In e), Kerr rotation angle θK is 0.27 (deg),
The square shape of the loop is also maintained. In each of the examples, the Kerr rotation angle θK almost reaches a saturation value when the magnetic field is returned to zero, and it is clear that the medium has excellent optical reproduction characteristics as a magneto-optical recording medium.

Therefore, the total composition ratio is (Gd1-XNdX)YFe
In a rare earth-transition metal amorphous thin film expressed as l-Y, by setting X in the range of 3 to 14 atoms [Y in the range of 24 to 30 atoms], magnetization in the direction perpendicular to the film surface of the thin film is easily achieved. It has a coercive force of 0.2 (KOe) to 1.3.
(KOe) and the car rotation angle θK is 0.
A magneto-optical recording medium having excellent characteristics in the range of 20 (deg) to Q,36 (deg) can be obtained.

As explained in detail above, according to the present invention, the total composition is (G d , -xP r x ) yF e 1- y
In the rare earth-transition metal amorphous thin film represented by
By selecting Y in the range of 3 to 14 atoms and Y in the range of 24 to 30 atoms, the magnetic moment due to rare earth elements and the magnetic moment due to iron elements are balanced, and the axis of easy magnetization is set perpendicular to the film surface of the thin film. It becomes possible to provide a magneto-optical recording medium having excellent magneto-optical recording characteristics.

[Brief explanation of the drawing]

FIGS. 1A and 1B show Kerr hysteresis loops obtained for each example of the magneto-optical recording medium of the present invention. Ku: magnetic anisotropy constant, Ms: saturation magnetization, Hc: coercive force, θ is Niker rotation angle.

Claims (1)

[Claims] It consists of an amorphous alloy thin film with an axis of easy magnetization perpendicular to the film surface, and the total composition ratio is (Gd_1_−_XPr_X).
A magneto-optical recording medium, represented as _YFe_1_-_Y, having a composition in which X is 3 to 14 atomic % and Y is 24 to 30 atomic %.