JPH0457637B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a method of manufacturing a magnetic thin film, and more particularly to a method of manufacturing a rare earth iron garnet thin film suitable for use as a magnetic recording and photothermal magnetic recording material.

b Conventional technology In recent years, rare earth iron garnet R ₃ (Fe, M) ₅ o ₁₂
(R: rare earth element, M: Al ³⁺ , Ga ³⁺ , Sc ³⁺ ,
Iron garnet R _3-X Bix (Fe, M) ₅ O ₁₂ , in which part of R in Tl ³⁺ , (Co ²⁺ +Tl ⁴⁺ ), etc.) is replaced with Bi, is attracting attention as a photothermal magnetic recording material. This Bi
Substituted rare earth iron garnet contains some of the rare earth elements.
By substituting Bi, it has the property that the Faraday rotation angle θF can be increased without increasing the absorption coefficient α too much, and is generally an excellent photothermal magnetic recording material.

In order to improve the performance of Bi-substituted rare earth iron garnets having such properties as photothermal magnetic recording materials, it is possible to increase the Bi substitution amount X and increase the Faraday rotation angle θ _F , but conventional liquid phase epitaxy It has been difficult to produce a Bi-substituted rare earth iron garnet thin film with a large Bi substitution amount X using production methods such as the Yall method.

The present inventors, in Japanese Patent Application No. 58-216750,
A method for manufacturing a magnetic thin film in which a high concentration Bi-substituted rare earth iron garnet single crystal thin film in which Bi is dissolved in solid solution up to the solid solution limit (50% of dodecahedral positions) can be epitaxially grown on a GGG substrate by sputtering method. proposed. However, this manufacturing method has the disadvantage that the substrates that can be used are limited to GGG substrates, so it is difficult to form a high concentration Bi-substituted rare earth iron garnet thin film on an amorphous substrate such as a glass substrate. A manufacturing method that would allow for this was desired.

Such requirements have existed for rare earth iron garnet thin films other than those mentioned above, and various attempts have been made. However, the thin films obtained to date are polycrystalline in-plane magnetized films with magnetization in a direction parallel to the plane, and a perpendicularly magnetized film preferable as a magnetic recording and photothermal magnetic recording material has not yet been obtained. . Furthermore, at present, no attempt has been made to form a perpendicularly magnetized Bi-substituted rare earth iron garnet film on an amorphous substrate.

In view of the above-mentioned problems, the present inventors have developed a magnetic thin film that can be formed on various substrates such as an amorphous substrate by using a rare earth iron garnet thin film such as a Bi-substituted rare earth iron garnet thin film having good perpendicular magnetization characteristics. In order to provide a manufacturing method, an amorphous rare earth iron garnet thin film is formed on a predetermined substrate by a vapor phase growth method, a protective film is formed on the amorphous rare earth iron garnet thin film, and then a protective film is formed on the amorphous rare earth iron garnet thin film. A method for producing a magnetic thin film in which the amorphous rare earth iron garnet thin film described above is crystallized by heat treatment was disclosed in an earlier patent application (Japanese Patent Application No. 1983-6134).

The above method prevents the adverse effects of heat treatment for crystallization, such as surface roughening due to crystallization of the magnetic thin film and scattering of Bi in the magnetic thin film, by providing a protective film on the magnetic thin film. However, it has the additional process of forming a protective film, and during magnetic writing using a reflective film usually provided on the surface of a magnetic film, the heat of the heated reflective film is transferred to the magnetic thin film. The disadvantage was that the presence of the protective film impeded the conduction of data, resulting in a slow response when writing.

c. Purpose of the Invention The present invention aims to produce rare earth iron garnet thin films with extremely good perpendicular magnetization characteristics by a sputtering method.
The objective is to provide a method for manufacturing on arbitrary substrates, such as amorphous substrates.

d Structure of the Invention The present invention comprises sputtering a target consisting of an oxide having a composition represented by the following chemical formula or a plurality of oxides mixed to have a composition represented by the following chemical formula in a reduced pressure atmosphere. A sputtering step of coating the amorphous magnetic thin film containing the target component on a substrate heated to 300 to 500°C, and then a step of heating the amorphous magnetic thin film to 500 to 900°C to crystallize it. This is a method of manufacturing a rare earth iron garnet thin film having perpendicular magnetization characteristics on a substrate.

Chemical formula (Bi ₂ O ₃ ) _X (R ₂ O ₃ ) _Y (F ₂ O ₃ ) _Z (M ₂ O ₃ ) _U 0<x≦3/2, 0<y≦3/2, 0<z<5 /2, 0≦u≦5/2 R is a rare earth element, M is Al ³⁺ , Ga ³⁺ , Sc ³⁺ ,
Tl ³⁺ , (Co ²⁺ + Tl ⁴⁺ ) Substrates used in the present invention include substrates that can withstand heating of about 700°C, such as amorphous substrates such as glass substrates, and crystalline substrates such as metals, semiconductors, and insulators. If so, you can use it.

A sputtering method is used as a vapor phase growth method to form an amorphous rare earth iron garnet thin film. Oxide _{or oxide} containing _at least _{Bi atom} , _Fe atom _and rare _earth atom _as represented by ₍ Bi ₂ O ₃ ) High frequency sputtering targeting a material consisting of a mixture of is preferred. In the above formula, 0<x≦3/2, 0<
y≦3/2, 0<z<5/2, 0≦u≦5/2, R is a rare earth element such as Y or Sm, M is Al ³⁺ ,
Ga ³⁺ , Sc ³⁺ , Tl ³⁺ , (Co ²⁺ + Tl ⁴⁺ ).

The amorphous magnetic thin film formed by the above vapor phase growth method becomes a magnetic thin film by heat treatment if it has a composition that creates rare earth iron garnet, but more than 20% of the dodecahedral positions of the garnet structure are due to Bi. A composition equivalent to Bi-substituted rare earth iron garnet is preferable because the magnetic anisotropy increases when crystallized into a garnet structure. Such an amorphous magnetic thin film containing a large amount of Bi is manufactured by a sputtering method using a target containing a large amount of Bi.

When creating an amorphous magnetic thin film by the sputtering method, it is necessary to heat the substrate to which the amorphous magnetic thin film is attached to a temperature of 300 to 500°C. More preferably, the temperature is set at 400 to 450°C in order to obtain a magneto-optical recording material. By setting the substrate at the above temperature, it is possible to produce a perpendicularly magnetized thin film that can be used as a magneto-optical recording material with less surface roughness of the magnetized film by subsequent heat treatment. 300 here
An amorphous magnetic thin film prepared at a temperature below 500°C is initially a smooth amorphous magnetic film, but after heat treatment, only a magnetic film with a rough surface is obtained, and at a temperature higher than 500°C, it becomes a smooth amorphous magnetic film. Instead of obtaining an amorphous magnetic thin film on the substrate, a crystalline magnetic thin film with surface roughness is produced directly. An amorphous film created at a substrate temperature of less than 300°C becomes a magnetic film with a rough surface due to heat treatment, and an amorphous film created at a substrate temperature of 300 to 500°C becomes a smooth perpendicularly magnetized thin film by heat treatment. The reason for this is unclear, but there are many very fine crystals in an amorphous thin film created at a low substrate temperature, and these grow during heat treatment, causing surface roughness. This is thought to be due to the large size and small number of these fine crystals in the amorphous thin film prepared by .

When a magnetic film with surface roughness is used as a magneto-optical recording material, it has the disadvantage that light is diffusely reflected on the surface of the magnetic film, making it unusable.

The heat treatment conditions for the amorphous magnetic film require a temperature of 500°C or higher. A temperature lower than 500°C is not preferred because crystallization is difficult to occur. Furthermore, if the temperature is higher than 900°C, Bi will volatilize from the magnetic film, so it is necessary to keep the temperature below 900°C.

Examples The method for manufacturing a magnetic thin film of the present invention will be described below (Y,
An embodiment applied to the production of a thin film of Bi-substituted rare earth iron garnet represented by Bi) ₃ (Fe, Al) ₅ O ₁₂ will be described with reference to the drawings. Furthermore, this (Y,
Bi) ₃ (Fe, Al) ₅ O ₁₂ is a yttrium iron garnet Y ₃ Fe ₅ O ₁₂ (YIG) in which part of Y is replaced with Bi and part of Fe is replaced with Al. The former increases the Faraday rotation angle θ _F without significantly increasing the absorption coefficient α, while the latter decreases the absorption coefficient α and lowers the saturation magnetization, making it easier to obtain a perpendicularly magnetized film and also lowering the Curie temperature. Are known.

First, as shown in FIG. 1, a quartz glass substrate 2 is placed on a stainless steel electrode plate (sample stage) 1 of a radio frequency (RF) sputtering device, and a first target 4 is attached to the electrode plate 3. . Note that this first target 4 has the composition formula
It consists of a disc-shaped sintered body of polycrystalline iron garnet expressed as _{Bi 2.0 Y 1.0Fe 3.8} Al _{1.2 O 12 .}

Next, after evacuating the inside of the sputtering device to a predetermined degree of vacuum, Ar and O ₂ are added to the sputtering device.
A mixed gas (Ar:O ₂ =9:1) is introduced up to about 7Pa. With the degree of vacuum stable, electrode plate 1
A predetermined high frequency voltage is applied between the electrode plate 3 and the electrode plate 3 to start glow discharge. Ar ⁺ generated by this discharge
The ions spatter the surface of the first target 4, and the sputtering causes the first target 4 to sputter.
Atoms such as Bi, Y, Fe, Al, and O are released from the
These detached atoms adhere to a quartz glass substrate 2 heated to, for example, 440°C by a heater 5 via an electrode plate 1, and (Y, Bi) ₃ (Fe, An amorphous thin film (hereinafter referred to as thin film) 6 of Al) ₅ O ₁₂ is formed. The power used for sputtering was 110W, and the sputtering time was 2.
When the time is 30 minutes, the thickness of the obtained thin film 6 is
It was 0.8 μm.

Next, the quartz glass substrate 2 with the thin film 6 formed as described above was heat treated in air at 700° C. for 3 hours to crystallize the magnetic thin film.

The magnetic thin film thus produced had a relatively low surface roughness and was in a surface condition suitable for use as a photothermal magnetic recording material.

When the crystallinity of the thin film 6 thus produced was examined by X-ray diffraction, it was found that it was a polycrystal without a dominant orientation. However, as a result of observation using an optical microscope, thin film 6, despite being polycrystalline, has an arabesque-like and bubble-like magnetic domain structure, and is an extremely good perpendicularly magnetized film with the following excellent properties. This was revealed through measurements.

That is, as shown in FIG. 2, when we measured the hysteresis characteristics of the Faraday rotation angle θ _F of the thin film 6 with respect to the magnetic field H in the direction perpendicular to the film surface, a loop with good squareness was obtained, and from the magnetic torque measurement It turned out to be a perpendicularly magnetized film. Furthermore, the Faraday rotation angle θ _F is extremely large at approximately 1.5°, and the coercive force Hc is also approximately
It is large enough at 200Oe. It can thus be seen that the thin film 6 has extremely favorable properties as a magnetic recording material. Note that since a perpendicularly magnetized film having excellent properties as shown in FIG. 2 can be obtained, larger perpendicular magnetic anisotropy is imparted to the thin film 6.
It is estimated that Bi is dissolved in solid solution up to the solid solution limit. In FIG. 2, a He--Ne laser (wavelength: 6328 Å) was used as a light source for measuring the Faraday rotation angle θ _F . Further, the measurement was performed by transmitting light through the thin film 6.

f Effects of the Invention According to the present invention, as is clear from the examples, a magnetic thin film having a sufficiently large Faraday rotation angle θ _F and a sufficiently large coercive force Hc and with little surface roughness can be coated with a protective film, etc. It can be created without attaching anything to the top.

In this way, a magnetic thin film without a protective film can be used as a photothermal magnetic recording material, and since a reflective film can be formed directly on the magnetic thin film, it is possible to write with relatively low intensity light, and it is very fast. It has the effect of increasing writing speed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing a high-frequency sputtering apparatus used in an embodiment of the method for producing a magnetic thin film of the present invention, and FIG. Bi) ₃ (Fe, Al) ₅
3 is a graph showing hysteresis characteristics of an O ₁₂ thin film. In the symbols used in the drawings, 1... electrode plate (sample stand), 2... quartz glass substrate, 3... electrode plate, 4... first target, 5... heater, 6
...(Y, Bi) ₃ (Fe, Al) ₅ O ₁₂ thin film.

Claims (1)

[Claims] 1. Sputtering a target consisting of an oxide having a composition represented by the following chemical formula or a plurality of oxides mixed so as to have a composition represented by the following chemical formula in a reduced pressure atmosphere, It consists of a sputtering process in which an amorphous magnetic thin film containing a target component is coated on a substrate heated to 300 to 500°C, and then a crystallization process in which the amorphous magnetic thin film is heated to 500 to 900°C. A method for producing a rare earth iron garnet thin film having perpendicular magnetization characteristics on a substrate. Chemical formula (Bi ₂ O ₃ ) _X (R ₂ O ₃ ) _Y (F ₂ O ₃ ) _Z (M ₂ O ₃ ) _U 0<x≦3/2, 0<y≦3/2, 0<z<5 /2, 0≦u≦5/2 R is a rare earth element, M is Al ³⁺ , Ga ³⁺ , Sc ³⁺ ,
Tl ³⁺ , (Co ²⁺ + Tl ⁴⁺ )