JPH0584658B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a spinel-type oxide ferromagnetic thin film, and more specifically, it relates to a method for manufacturing a spinel-type oxide ferromagnetic thin film. ,Fe
The object of the present invention is to obtain a spinel-type oxide ferromagnetic thin film whose main components are Fe and Co.

In the present invention, "spinel-type oxides containing Fe as a main component" include magnetite (Fe ₃ O ₄ ), maghemite (γ-Fe ₂ O ₃ ), and intermediate oxides thereof (FeOx・Fe ₂ O ₃ 0 <x<1), and the spinel-type oxide mainly composed of Fe and Co refers to the above-mentioned magnetite, maghemite, and intermediate oxides thereof.
This refers to materials containing metallic elements, mainly Co.

The spinel type oxide ferromagnetic thin film obtained according to the present invention is mainly used as a magnetic recording medium.

[Conventional technology]

In recent years, there has been a remarkable trend toward miniaturization and high reliability of information devices and systems, and there is a strong demand for high-density magnetic recording media with excellent reproduction output and sensitivity.

Conventionally, the mainstream of magnetic recording media has been to mix magnetic particles such as acicular magnetite particles and acicular maghemite particles with a binder to form a magnetic paint.
It was a so-called coated magnetic recording medium obtained by oriented coating the magnetic paint on a film.

Various attempts have been made to improve the above-mentioned coated magnetic recording media for higher density recording, but since they contain binders that are not involved in magnetic recording, the Bm value of the magnetic recording media is only about 2000 Gauss, which is high. Improved density recording technology is also approaching its limits.

Therefore, spinel-type oxide magnetic thin films containing Fe as a main component are attracting attention as new magnetic recording media capable of high-density recording.

Currently, as typical methods for producing spinel-type oxide magnetic thin films containing Fe as a main component, methods using reactive vapor deposition, methods using reactive sputtering, etc. are known.

The former method is to ``evacuate to a sufficiently high degree of vacuum, set the substrate temperature to a specified temperature, then flow oxygen gas through a variable leak valve to maintain a specified oxygen pressure.''
Evaporate Fe. (High-density magnetic recording technology compilation, published by Sogo Gijutsu Center Co., Ltd. (1983) No. 191
page)”, which reacts oxygen gas with iron atoms or clusters of iron atoms on the substrate surface to form Fe ₃ O ₄
It produces a film.

The latter method involves sputtering an iron target in a mixed gas of Ar and O ₂ to form an α-Fe ₂ O ₃ thin film on the substrate. This is then heat-treated in a reducing atmosphere.
Making a Fe ₃ O ₄ film... (Material MR74-41, Magnetic Recording Research Group, Institute of Electronics and Communication Engineers) In any case, in order to make a γ-Fe ₂ O ₃ film, for example, As described in Japanese Patent No. 55-118620, it is necessary to further oxidize the obtained Fe ₃ O ₄ film at 250°C to 350°C.

[Problem that the invention seeks to solve]

A spinel-type oxide magnetic thin film containing Fe as a main component is preferable as a high-density magnetic recording medium, but in the case of using the above-mentioned known technology, a high temperature of 250 to 300°C or more is required in the manufacturing process. As a result, the types of substrates are inevitably limited, resulting in industrial and economical disadvantages.

That is _, in the method using reactive vapor deposition, depending on the vapor deposition conditions such as the _substrate temperature, hematite (α
-Fe ₂ O ₃ ) is generated, and the lower the substrate temperature is, especially below 250° C., the easier it is for hematite to be generated. This fact can be seen, for example, in the aforementioned ``High-density Magnetic Recording Technology Collection'', pages 191-192, ``α-Fe ₂ O ₃ and Fe ₃ O ₄ are obtained by changing the deposition conditions.
...In order to obtain an intermediate film Fe ₃ O ₄ for γ-Fe ₂ O ₃ that is promising as a magnetic recording medium, the higher the substrate temperature and the faster the film formation rate, the more desirable. ” and “IEICE Technical Research Report” published by the Institute of Electronics and Communication Engineers.
(1975) MR75-18 pp. 1-2, ``As the substrate temperature decreases and the deposition rate decreases, α-Fe ₂ O ₃ becomes more likely to be formed.
℃), a film consisting only of Fe ₃ O ₄ is formed over a wide range of deposition rates. ” as stated.

In the reactive sputtering method, a hematite (α-Fe ₂ O ₃ ) thin film formed on a substrate is heat-treated in a reducing atmosphere to form a magnetite (Fe ₃ O ₄ ) thin film, and the heat treatment temperature is 300°C ( ``Magnetic Recording Research Group Material MR74-41, page 13)'' mentioned above.

Therefore, there is a strong desire to establish a method for manufacturing spinel-type oxide magnetic thin films containing Fe as the main component at as low a temperature as possible.

[Means for solving problems]

The present inventor has arrived at the present invention as a result of various studies on methods for manufacturing spinel-type oxide magnetic thin films containing Fe as a main component at as low a temperature as possible.

That is, in the present invention, a metal containing Fe as a main component is used as a vapor-deposited metal, and the vapor-deposited metal is evaporated onto the substrate at a temperature higher than room temperature and lower than 150°C in a high vacuum chamber of 10 ^-5 Torr or less. After forming a thin metal layer mainly composed of Fe with a thickness of 50 Å or less,
A spinel-type oxide containing Fe as a main component is produced by introducing an oxygen-containing gas exceeding 10 ^-5 Torr into a vacuum chamber at a temperature range from room temperature to below 150°C to oxidize the metal thin film containing Fe as a main component. said operation of forming a thin layer and then evaporating the deposited metal;
By alternately repeating the above operation of oxidizing the metal thin layer containing Fe as the main component, a spinel-type oxide ferromagnetic thin film consisting of laminated spinel-type oxide thin layers containing Fe as the main component can be produced. A manufacturing method, and an alloy mainly composed of Fe and Co is used as a vapor deposited metal, and the vapor deposited metal is evaporated onto the substrate at a temperature higher than room temperature and lower than 150°C in a high vacuum chamber of 10 ^-5 Torr or less. with a thickness of less than 50Å
After forming a thin metal layer of an alloy mainly composed of Fe and Co, an oxygen-containing gas exceeding 10 ^-5 Torr is introduced into a vacuum chamber at a temperature range from room temperature to below 150°C to remove the Fe and Co. The thin metal layer of the alloy containing Fe and Co as the main components is oxidized to form a spinel-type oxide thin layer containing Fe and Co as the main components, and then the above operation of evaporating the deposited metal and the A method for producing a spinel-type oxide ferromagnetic thin film, which comprises stacking spinel-type oxide thin layers containing Fe and Co as main components by alternately repeating the above-described operation of oxidizing a metal thin layer. .

[Effect]

First, the most important point in the present invention is to evaporate the metal containing Fe as the main component to form a thin metal layer on the substrate, and then introduce an oxygen-containing gas to evaporate the Fe. When a spinel-type oxide thin layer containing Fe as the main component is obtained by oxidizing a metal thin layer containing Fe as the main component, the substrate temperature and the oxidation temperature at the time of introducing the oxygen-containing gas should be set to less than 150°C, especially
The temperature can be kept near room temperature, and a spinel-type oxide thin layer containing Fe as a main component can be obtained at a low temperature.

In the present invention, an oxygen-containing gas is introduced.
By selecting the oxidation conditions for oxidizing the thin metal layer containing Fe as the main component, the composition of the spinel-type oxide thin layer containing Fe as the main component is changed.

That is, regarding the oxygen gas concentration, Fe ₃ O ₄ is likely to be produced in a range where the oxygen gas concentration is low, and γ-Fe ₂ O ₃ is likely to be produced in a region where the oxygen gas concentration is high.

Regarding the oxidation temperature, the higher the temperature within the above-mentioned temperature range, the easier it is to obtain γ-Fe ₂ O ₃ .

In addition, in the present invention, Fe is used as the vapor-deposited metal.
A higher coercive force is obtained by using an alloy whose main components are Fe and Co to obtain a spinel-type oxide thin layer whose main components are Fe and Co.

Next, various conditions for implementing the present invention will be described.

In the present invention, a metal containing Fe as a main component can be used as the deposited metal.

In addition, in the present invention, when obtaining a spinel type oxide ferromagnetic thin film having higher coercive force,
An alloy containing Fe and Co as the main components can be used as the deposited metal, and by adjusting the amount of Co in the deposited metal, the composition of the alloy can be controlled so that Fe and Co having an arbitrary composition can be used as the main components. A thin metal layer can be obtained.

The vapor-deposited metal in the present invention may include, if necessary,
Furthermore, metals such as Ni, Cr, Zn, Cu, Ti, and Mn may be added.

Vapor deposition in the present invention is performed under a high vacuum of 10 ^-5 Torr or less.

When depositing in a low vacuum exceeding 10 ^-5 Torr,
It is difficult to obtain the desired ferromagnetic oxide because it contains impurities or produces an oxide that does not have magnetism.

The method of heating the evaporated metal in the present invention may be a well-known resistance heating method, an induction heating method, an electron beam heating method, or the like.

In the present invention, since the substrate temperature and the temperature at the time of oxygen introduction can be kept at a low temperature of less than 150°C, especially around room temperature, the substrate material can be made of aluminum, polyimide, glass, etc., as well as heat-sensitive polyester, etc. can also be used and can be appropriately selected depending on the purpose, which is very advantageous industrially and economically.

The substrate temperature and the temperature at the time of oxygen introduction are related to the crystallinity of the spinel type oxide that is generated.
When obtaining a spinel type oxide thin film with higher magnetic properties, it is preferable to select a temperature of 50 to 150°C.

In the present invention, Fe is the main component, or
The thickness of the metal thin layer containing Co as a main component is 50 Å or less.

If it exceeds 50 Å, the thin metal layer may remain unoxidized, making it difficult to obtain the desired ferromagnetic thin film consisting only of a uniform spinel-type oxide layer.

Furthermore, even when the thickness of the metal thin film exceeds 50 Å, the entire thin metal layer can be oxidized by selecting the oxidation conditions, but as the thickness of the metal thin layer increases, the oxidation temperature needs to be raised. , cracks are more likely to occur when oxides are formed.

The deposition rate in the present invention may be selected within a range that allows the thickness of the thin metal layer to be controlled.

In the present invention, Fe is the main component, or
and spinel type oxide thin layer mainly composed of Co,
Obtained by introducing an oxygen-containing gas exceeding 10 ^-5 Torr into a vacuum chamber and uniformly oxidizing the surface of a thin metal layer of an alloy whose main component is Fe or Co. .

If the oxygen atmosphere is below 10 ^-5 Torr,
It becomes difficult to uniformly oxidize the thin metal layer from the surface in a short period of time.

When the oxygen concentration is between 10 ^-5 and ^{10 -3} Torr,
Fe ₃ O ₄ ^is easily generated, and γ-
Fe ₂ O ₃ is easily generated.

In the present invention, Fe is the main component, or
The thickness of the laminated layer consisting of a spinel-type oxide thin layer mainly composed of , it can be made less than 1000 Å, making it suitable for high density.

The spinel-type oxide ferromagnetic thin film made of Fe and Co in the present invention has a higher coercive force, and the coercive force improves as the amount of Co increases.

Co can be added up to about 30 atomic %, but in practice, 0.2 to 10 atomic % is preferable.

〔Example〕

Next, the present invention will be explained with reference to examples.

Example 1 Metallic iron was deposited to a thickness of 15 Å at a deposition rate of 0.5 Å/sec on a base film substrate of polyethylene terephthalate kept at 60°C in a vacuum chamber kept at 4× ¹⁰ -6 Torr to form a thin iron layer. After forming the layer, oxygen gas of 1×10 ⁻² Torr was introduced for 50 seconds to oxidize the iron thin film. Then, the inside of the tank was washed 4x again.
After evacuating to 10 ^-6 Torr, the following operations were repeated 50 times to obtain an oxide thin film.

The obtained oxide thin film had a brown color, and the presence of fine iron particles was not observed by measuring the Mössbauer effect. Further, as a result of electron beam diffraction performed using a thin film simultaneously formed on a NaCl substrate for structural analysis, it was confirmed that it had a spinel structure. Therefore, the obtained thin film is presumed to be a uniform oxide thin film mainly composed of γ-Fe ₂ O ₃ .

Regarding the above oxide thin film, the results of magnetic measurement by VSM are that coercive force Hc = 290 Oe, saturation magnetic flux density
Bm=4400Gauss, residual magnetic flux density Br=3400Gauss,
It had a squareness ratio Rs of 0.773, high Bm and Br, and was suitable for magnetic recording media.

Example 2 Metallic iron was deposited to a thickness of 20 Å at a deposition rate of 0.5 Å/sec to form a thin iron layer on a polyimide film substrate kept at 150°C in a vacuum chamber kept at 4×10 ^-6 Torr. After that, oxygen gas of 8×10 ^-4 Torr was introduced for 30 seconds to oxidize the iron thin film. Then, the inside of the tank was washed 4x again.
After evacuating to 10 ^-6 Torr, the following operations were repeated 50 times to obtain an oxide thin film.

The obtained oxide thin film had a blackish brown color, and the presence of fine iron particles was not observed by measuring the Mössbauer effect. Further, from the results of electron beam diffraction performed in the same manner as in Example 1, it was confirmed that it had a spinel structure. Therefore, the obtained thin film is
It is estimated that it is a uniform oxide thin film with a composition intermediate between Fe ₃ O ₄ and γ-Fe ₂ O ₃ .

Regarding the above oxide thin film, the results of magnetic measurement by VSM are that coercive force Hc = 320Oe, saturation magnetic flux density
Bm=4960Gauss, residual magnetic flux density Br=3890Gauss,
It had a squareness ratio Rs of 0.784, high Bm and Br, and was suitable for magnetic recording media.

Example 3 A thin iron layer was formed by depositing a metal plate to a thickness of 15 Å at a deposition rate of 0.5 Å/sec on a base film substrate of polyethylene terephthalate kept at room temperature in a vacuum chamber kept at 1×10 ^-7 Torr. After forming the iron thin film, oxygen gas of 1×10 ⁻⁴ Torr was introduced for 30 seconds to oxidize the iron thin film. Then, the inside of the tank was washed 4x again.
After evacuating to 10 ^-6 Torr, the following operations were repeated 50 times to obtain an oxide thin film.

The obtained oxide thin film had a black color, and as a result of electron beam diffraction conducted in the same manner as in Example 1, it was confirmed that it was an oxide having a spinel structure.
Also, no presence of iron particles was found in the Mössbauer effect measurement. Therefore, the obtained thin film is
It is presumed to be a uniform oxide thin film mainly composed of Fe ₃ O ₄ .

Regarding the above oxide thin film, the results of magnetic measurement by VSM are that coercive force Hc = 230 Oe, saturation magnetic flux density
Bm=5340Gauss, residual magnetic flux density Br=3900Gauss,
It had a squareness ratio Rs of 0.730, high Bm and Br, and was suitable for magnetic recording media.

Example 4 A 1.8 at% Co-Fe alloy was deposited to a thickness of 10 ^Å at a deposition rate of 0.3 Å/sec on a base film substrate of polyethylene terephthalate kept at room temperature in a vacuum chamber kept at 1×10 -7 Torr. After forming a thin Fe-Co alloy layer, oxygen gas of 5×10 ^-4 Torr was introduced for 20 seconds to
The Fe-Co alloy thin film was oxidized. Next, the inside of the tank was again evacuated to 1 x 10 ^-7 Torr, and the following operations were repeated 100 times to obtain an oxide thin film.

The obtained oxide thin film had a black color, and as a result of electron beam diffraction conducted in the same manner as in Example 1, it was confirmed that it was an oxide having a spinel structure.
Also, no presence of iron particles was found in the Mössbauer effect measurement. Therefore, the obtained thin film is
It is presumed to be a uniform oxide thin film mainly composed of Fe ₃ O ₄ containing Co.

Regarding the above oxide thin film, the results of magnetic measurement by VSM are that coercive force Hc = 560 Oe, saturation magnetic flux density
Bm=5030Gauss, residual magnetic flux density Br=4000Gauss,
It had a squareness ratio Rs of 0.795, high Bm and Br, and was suitable for magnetic recording media.

Example 5 4 at% Co and 1 at% Cu-Fe alloys were deposited to a thickness of 0.5 Å/sec on a base film substrate of polyethylene terephthalate kept at 80°C in a vacuum chamber kept at 1×10 ^-7 Torr. After forming a thin layer of Fe-Co-Cu alloy by vapor deposition to a thickness of 15 Å, oxygen gas of 5 × 10 ^-3 Torr was introduced for 60 seconds to
A Fe-Co-Cu alloy thin film was oxidized. Next, the inside of the tank was again evacuated to 1×10 ⁻⁷ Torr, and the steps 2 and 4 were repeated 60 times to obtain an oxide thin film.

The obtained oxide thin film had a brown color, and as a result of electron beam diffraction conducted in the same manner as in Example 1, it was confirmed that it was an oxide having a spinel structure.
Also, no presence of iron particles was found in the Mössbauer effect measurement. Therefore, the obtained thin film is
It is presumed to be a uniform oxide thin film mainly composed of γ-Fe ₂ O ₃ containing Co and Cu.

Regarding the above oxide thin film, the results of magnetic measurement by VSM are that coercive force Hc = 700 Oe, saturation magnetic flux density
Bm=4600Gauss, residual magnetic flux density Br=3770Gauss,
It had a squareness ratio Rs of 0.820, high Bm and Br, and was suitable for magnetic recording media.

Example 6 A 2at% Co-Fe alloy was deposited to a thickness of 15 ^Å at a deposition rate of 0.3 Å/sec on a base film substrate of polyethylene terephthalate kept at room temperature in a vacuum chamber kept at 5 × 10 -6 Torr. After forming a thin Fe-Co alloy layer, oxygen gas of 2×10 ^-2 Torr was introduced for 20 seconds.
The Fe--Co alloy thin film was subjected to oxidation treatment. Next, the inside of the tank was again evacuated to 5 x 10 ^-6 Torr, and the following operations were repeated 50 times to obtain an oxide thin film.

The obtained oxide thin film had a dark brown color, and as a result of electron beam diffraction conducted in the same manner as in Example 1, it was confirmed that it was an oxide having a spinel structure. Also, no presence of iron particles was found in the Mössbauer effect measurement.

Therefore, the obtained thin film is estimated to be a uniform oxide thin film having an intermediate oxidation composition of Co-containing Fe ₃ O ₄ and γ-Ee ₂ O ₃ .

Regarding the above oxide thin film, the results of magnetic measurement by VSM are that coercive force Hc = 640 Oe, saturation magnetic flux density
Bm=4710Gauss, residual magnetic flux density Br=4750Gauss,
The squareness ratio Rs was 0.796, which was a suitable characteristic as a magnetic recording medium.

Example 7 On a polyimide film substrate kept at 130°C in a vacuum chamber kept at 1×10 ^-7 Torr, 3at%Co, 0.5at%Zn, 96.5at%Fe alloy was deposited at 1 Å/sec as a deposition source. The alloy at a speed of 50Å
After depositing the Fe-Co-Zn alloy thin layer to a thickness of , oxygen gas of 1×10 ^-2 Torr was introduced for 40 seconds.
The Fe-Co-Zn alloy thin film was oxidized. Next, the inside of the tank was again evacuated to 1×10 ^-7 Torr, and the following operations were repeated 20 times to obtain an oxide thin film.

The obtained oxide thin film had a brown color, and as a result of electron beam diffraction and Mössbauer effect measurements performed in the same manner as in Example 1, it was found that γ- containing Co and Zn.
It was confirmed that it was a uniform oxide thin film mainly composed of Fe ₂ O ₃ . The result of magnetic measurement is coercive force Hc=
720Oe, saturation magnetic flux density Bm = 3970Gauss, residual magnetic flux density Br = 3210Gauss, squareness ratio Rs = 0.809,
It was suitable for high-density magnetic recording media.

〔effect〕

According to the method for producing a spinel-type oxide ferromagnetic thin film of the present invention, as shown in the previous example, it is possible to produce a spinel-type oxide ferromagnetic thin film containing Fe as the main component or Fe and Co as the main component at a low temperature of above room temperature and below 150°C. Since it is possible to obtain a spinel-type oxide ferromagnetic thin film, especially a ferromagnetic thin film mainly composed of γ-Fe ₂ O ₃ , the range of substrate types can be expanded, and it is very advantageous from an industrial and economical point of view. be.

The main component is Fe obtained according to the present invention, or
A spinel-type oxide ferromagnetic thin film containing Fe and Co as main components has high magnetic properties as shown in the previous example, and is suitable as a high-density magnetic recording medium.

Claims (1)

[Claims] 1. A metal containing Fe as a main component is used as an evaporation metal, and the evaporation metal is evaporated onto a substrate at a temperature higher than room temperature and lower than 150°C in a high vacuum chamber of 10 ^-5 Torr or less. After forming a thin metal layer mainly composed of Fe with a thickness of 50 Å or less,
By introducing an oxygen-containing gas exceeding 10 ^-5 Torr into a vacuum chamber at a temperature range of less than Then, by alternately repeating the above operation of evaporating the evaporated metal and the above operation of oxidizing the thin metal layer containing Fe as the main component, a spinel-type oxide thin layer containing Fe as the main component is laminated. A method for producing a spinel-type oxide ferromagnetic thin film, characterized by: 2. An alloy mainly composed of Fe and Co is used as an evaporation metal, and the evaporation metal is evaporated onto a substrate at a temperature higher than room temperature and lower than 150°C in a high vacuum chamber of 10 ^-5 Torr or less, thereby forming a layer of 50 Å or less on the substrate. After forming a thin metal layer of an alloy mainly composed of Fe and Co, an oxygen-containing gas exceeding 10 ^-5 Torr is introduced into a vacuum chamber at a temperature range from room temperature to 150°C to remove the Fe and Co. and Co as the main components by oxidizing the metal thin layer of the alloy containing Fe and Co as the main components to form a spinel-type oxide thin layer containing Fe and Co as the main components, and then the above operation of evaporating the evaporated metal and Fe and Co as the main components. Production of a spinel-type oxide ferromagnetic thin film characterized by laminating spinel-type oxide thin layers containing Fe and Co as main components by alternately repeating the above-mentioned operation of oxidizing a metal thin layer. Method.