JPH0338726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic thin film and a method for manufacturing the same.

[Conventional configuration and its problems]

First, regarding soft magnetic metal materials,
Crystalline materials such as Ni-Fe alloy, Ni-Fe-Mo alloy, metal metalloid amorphous materials such as Co-Fe-Si-B system, and metal-metal amorphous materials such as Co-Zr system. Known for its quality materials. Bulk soft magnetic materials are in demand for transformer core materials, magnetic shield materials, magnetic head core materials, etc. On the other hand, thin films of soft magnetic materials are also used for thin film memories, thin film magnetic heads, transfer patterns of magnetic valve elements, and the like.

The properties required of soft magnetic materials vary slightly depending on the application, but basically they are low coercive force (low coercive force), high residual magnetic flux density, and high magnetic permeability. As a thin film soft magnetic material, Fe−
Ni alloys (permalloy materials) and metal-metal amorphous materials are mainly used. Fe-ni alloy is
Due to the high Ni concentration, the saturation magnetic flux density is approximately 8,000 Gauss, which is approximately one-third of the 22,000 Gauss of iron alone. On the other hand, in the case of a metal-metal amorphous thin film, the saturation magnetic flux density can be increased, but it is necessary to use sputtering to prepare the thin film. Sputtering has problems such as a slow deposition rate of a thin film and the introduction of gas, which may be incorporated into the film and cause aging of the properties.

Second, regarding materials with high coercive force for magnetic recording media, recently, a magnetic recording medium using a metal thin film, in which a Co-Ni alloy is formed on a polyester film, has been put into practical use as an audio magnetic tape. It's starting to happen. In order to obtain a large coercive force relatively easily under the two conditions of oblique incidence deposition and deposition in an oxygen atmosphere, the Co-Ni thin film must be reduced to less than half of its bulk value as a saturation magnetic flux density. I have to let it happen.

It is true that magnetic thinning is required to obtain a large coercive force, but when lowering the density by creating voids within a thin film, such as in oblique deposition, reliability is inevitably insufficient. Therefore, supplementary measures such as applying rust inhibitors must be used. It is good as long as the coercive force is not lowered without creating a void. As a method, it is sufficient to replace the role of the binder in the conventional coating type media with metal. The metal that acts as a binder is preferably non-magnetic and has good corrosion resistance.

[Purpose of the invention]

The purpose of this invention is to have a high residual magnetic flux density,
Another object of the present invention is to provide a magnetic thin film having a sufficiently low or sufficiently high coercive force in a range that has not been previously available, and to provide a method for producing such a magnetic thin film.

[Structure of the Invention] The magnetic thin film of the present invention is made of iron (hereinafter referred to as Fe).
contains at least one metal selected from silver (Ag), magnesium (Mg) and bismuth (Bi) (hereinafter referred to as Z), and boron (hereinafter referred to as B), and has a compositional formula of Fe _{1- (X+a)} Z _x B _a (0.2≦x≦0.8 0<a<0.2 x, a is the atomic ratio).

Even if such magnetic thin films have the same composition, two types of magnetic thin films with different characteristics can be obtained depending on the manufacturing process. One is one with low coercive force, which is suitable for soft magnetic materials. The other is one with high coercive force, which is suitable for magnetic recording media.

This point will be explained in detail below.

Among magnetic thin films with the above composition, those in which each constituent element is uniformly and disorderly distributed at the atomic level within the thin film have less anisotropy caused by the crystal, and for example, the magnetic properties may vary from the inner surface. Since the anisotropy is eliminated, a product with low coercive force can be obtained.

On the other hand, even if they have the same constituent elements, they are not uniform at the atomic level, and there are also systems in which ferromagnetic metal atoms and non-magnetic metal atoms separate to form particles with a size of several tens to hundreds of angstroms. Conceivable. In this case, the non-magnetic metal particles and the ferromagnetic metal particles are mixed, and the ferromagnetic particles are floating in the metal binder. A thin film having such a structure has a large coercive force and is suitable for use in magnetic recording media.
The problem is how to realize such a structure.

Originally, it is thought to be difficult to produce a thin film made of elements that do not form an alloy, but it is possible if the elements constituting the thin film are deposited separately, so-called multi-component vapor deposition. However, since the cohesive energy between different elements acts in a repulsive direction, if the temperature of the substrate is high,
Since the deposited atoms diffuse and migrate, and atoms of the same type agglomerate, the substrate temperature must be kept below the temperature at which significant atomic diffusion occurs. In this way, it is possible to obtain a thin film in which atoms of different types are stochastically and randomly distributed at the atomic level. A thin film in which atoms are randomly distributed at the atomic level naturally has low anisotropy, and works in the direction of reducing magnetocrystalline anisotropy, which has a negative effect on magnetic permeability. This makes it useful as a soft magnetic material.

However, in this case, the non-Rz/Ry of the atomic radius Ry of the ferromagnetic metal and the atomic radius Rz of the non-magnetic metal is approximately
If it is 1.25 or more, it may lose its ferromagnetism and become non-magnetic when it becomes a random structure. However, depending on the composition, magnetism occurs when heat treated in the range of 100°C to 200°C. This seems to be because the random structure is relaxed to some extent by the heat treatment, causing aggregation of similar elements. However, at this time, if the material is heat-treated at a temperature higher than the above-mentioned temperature, it will become a material with a high coercive force as described below, so it is necessary to adequately control the temperature.

The role of the non-metallic element B (boron) is firstly to stabilize the thin film itself and relieve internal stress within the thin film, and secondly to improve the controllability of the heat treatment temperature. The third is to improve reliability.

In addition, in order to obtain a high coercive force for the thin film of Fe-Z-B composition to be manufactured, silver (Ag) represented by Z,
The value of the atomic ratio of at least one metal selected from magnesium (Mg) and bismuth (Bi), that is, the value of x, is limited to 0.2≦x≦0.8, and from this value of x, Fe-Z-B The value of a was determined so that each composition did not become 0.

[Explanation of Examples]

The magnetic thin film of this invention is formed in vacuum. As a manufacturing apparatus, a multi-source vacuum evaporation apparatus as shown in FIG. 1 is used. Alternatively, a continuous winding type vacuum evaporation apparatus as shown in FIG. 2 may be used. In this case, a flexible plastic film is used as the substrate.

In FIG. 1, 1 is an electron beam heating hearth for evaporating ferromagnetic material, 2 is an alumina-coated tungsten heater for depositing non-magnetic metal, 3 is a substrate, 4 is a shutter, and 5 is a vacuum evacuation system. B (boron)
The additional elements may be evaporated in a mixed state from the hearth 1 or the heater 2, or a third evaporation source may be provided. Figure 2 is a schematic diagram of a continuous evaporation machine, in which 1 is an electron beam heating hearth, 2 is a crucible for non-magnetic metal evaporation, 3 is a flexible substrate, 5 is an exhaust system, 6 is a roller for cooling the substrate, and 7 is a The unwinding roll and 8 are the take-up rolls.

Since thin films of essentially immiscible metals are formed, multi-source equipment must be used, but sputtering with composite targets can also accomplish the same thing. For magnetic metals, it is stable to use electron beam heating, but resistance heating may also be used. For silver (Ag), which has a relatively low vapor pressure, electron beam heating and resistance heating are appropriate; however, for magnesium (Mg), which has a very high vapor pressure, a lid with small holes is used. Stabilization can be achieved by evaporating it from an attached alumina crucible.

Example 1 A thin film having a composition of (Fe _0.95 B _0.05 ) _1-X Ag _X was produced using the apparatus shown in FIG. The manufacturing conditions are shown below.

Degree of vacuum 2×10 ^-6 Torr or less Substrate speed 45°C or less Substrate Soda glass plate Heat-resistant plastic film Deposition temperature FeB alloy 300 Å/min Ag 0 to 2000 Å/min Incident angle 0° to 30° Film thickness 1500 Å The obtained thin film Figure 3 shows the values of coercive force Hc and initial magnetic permeability μ with respect to the atomic ratio of magnetic alloy and Ag.

Next, the results of heat treatment to improve temperature stability and increase coercive force are shown for cases where x is 0.40 and 0.55.
Heat treatment was performed under an argon atmosphere (1 atm),
The constant temperature holding time is 1 hour. The results are shown in Figure 4. The coercive force hardly changes up to 200℃,
Above that, the coercive force increases rapidly. There are compositional variations, but the trend is the same.
Moreover, when heat treated within the range of 250°C to 350°C, it becomes a hard magnetic thin film. Therefore, as a soft magnetic material, it is stable at temperatures below 200°C.

When heat treated at 300℃ for 1 hour (Fe _0.95
Figure 5 shows the coercive force values of B _0.05 ) _1-X Ag _X. FEB
The coercive force is maximum when the amounts of and Ag are approximately equal.

Example 2 Using the apparatus outlined in Figure 2 (Fe _0.95 B _0.05 ) _1-X
Mg _x was continuously fabricated on a heat-resistant plastic film. The manufacturing conditions are shown below.

Vacuum degree 5×10 ^-6 Torr or less Substrate (can temperature) Water temperature Substrate Heat-resistant plastic film Vapor deposition rate FeB alloy 1000 Å/sec Mg 0 to 10000 Å/sec Incident angle 0° to ±45° Film thickness 1500 Å Obtained film thickness Figure 6 shows the coercive force Hc and initial magnetic permeability for the atomic ratio of magnetic alloy and Mg. In addition,
In this type of thin film, when x is 0.5 or more, the magnetization is small immediately after evaporation, so specifically, large-scale atomic diffusion occurs and the magnetization is increased once at a temperature at which the coercive force does not increase, that is, 120°C. Measurements were made from This heat treatment was carried out using a continuous atmosphere heat treatment apparatus as schematically shown in FIG. In FIG. 7, 9 is a heating roller for heat treatment, 10 is a heater for heating atmospheric gas, 11 is an atmospheric gas introduction hole,
In this embodiment, the inert gas argon was used as the atmospheric gas, but other inert gases may be used. 12 is an unwinding roll, 13 is a winding roll, 14
16 is a preliminary heating roller, 16 is a slow cooling roller, and 16 is a preliminary gas sealing chamber. By using this apparatus, heat treatment can be performed under stable conditions.

Next, we will discuss (FeB) as a high coercive force magnetic thin film.
Explain Mg thin film. Heat treatment was performed continuously at 250° C. for 30 seconds using the atmospheric heat treatment apparatus shown in FIG. The results are shown in FIG. (FeB)Mg-based thin films can be heat-treated at lower temperatures than (FeB)/Ag-based films. Furthermore, since the heat treatment time can be carried out continuously, rapid heating and cooling can be performed and the time can be shortened.

Example 3 FeBAg-based and FeBMg-based metal hard magnetic thin films were fabricated by vapor deposition at a substrate temperature at which atomic diffusion occurs significantly. The manufacturing conditions are shown below.

Degree of vacuum 5×10 ^-6 Torr or less Substrate temperature 50 to 350℃ (variable) Substrate Heat-resistant plastic film Glass plate Vapor deposition rate Fe _0.95 B _0.05 alloy Approx. 300 Å/min Mg and Ag Approx. 400 Å/min Incident angle 0° to 30° Film thickness 1400Å (Fe _0.95 B _0.05 ) _0.45 Ag _0.55 and (Fe _0.95 B _0.05 ) _0.
45
Figure 9 shows the coercive force values when a thin film of Mg _0.55 was prepared by changing the substrate temperature. The dependence on substrate temperature is different between Ag and Mg systems, but this is thought to be due to the difference in the melting points of the respective metals.

Example 4 A FeBBi-based metal hard magnetic thin film was prepared by vacuum evaporation while maintaining the substrate temperature at about room temperature, and then heat-treated in an argon atmosphere. The manufacturing conditions are shown below.

Degree of vacuum 5×10 ^-6 Torr or less Substrate temperature 25℃ Substrate Glass plate Vapor deposition rate Fe _0.95 B _0.05 alloy Approx. 300Å/min Bi 0 to 1500Å/
Min. Incident angle 0° to 30° Film thickness 1800 Å Heat treatment temperature 50 to 350°C (variation) Figure 10 shows the results when the ratio of Fe-B alloy to Bi was varied.

Example 5 Fe-B-Ag system, Fe-B-Mg system and Fe-B
- Characteristics of Bi-based thin films were investigated by varying the proportion of B (boron). The thin film manufacturing method was the same as in Examples 1, 2, and 4, and heat treatment was performed to obtain a hard magnetic thin film. The results are shown in FIG. The heat treatment temperature is
For Fe-B-Ag thin films, 300℃, Fe-B-
The temperature is 250°C for Mg-based thin films and 120°C for Fe-B-Bi-based thin films.

As explained in each of the above embodiments, this invention
It can be seen that this material exhibits useful properties for the production of hard and soft magnetic thin films containing Fe as the main component.

〔Effect of the invention〕

According to this invention, the magnet has a high residual magnetic flux density,
In addition, there is an effect that a magnetic thin film having a sufficiently low or sufficiently high coercive force in a range that has not been obtained conventionally can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a multi-source vacuum evaporation apparatus, Figure 2 is a diagram of a continuous winding vacuum distillation apparatus, and Figure 3 is a diagram of the coercive force and initial permeability of a Fe-B-Ag soft magnetic thin film. A graph showing the compositional dependence of magnetic property. Figure 4 is a graph showing the relationship between heat treatment temperature and coercive force of a Fe-B-Ag based magnetic thin film deposited at a low temperature. Figure 5 is a graph showing the relationship between coercive force and Fe-B-Ag magnetic thin film deposited at a low temperature.
-A graph showing the compositional dependence of coercive force after heat treatment of Ag-based soft magnetic thin film. Figure 6 is a graph showing compositional dependence of coercive force and initial permeability of FeB-Mg-based soft magnetic thin film. Figure 7 is A schematic configuration diagram of a heat treatment apparatus for continuously deposited films. Figure 8 is a graph showing the compositional dependence of coercive force after heat treatment of Fe-B-Mg based hard magnetic thin films. Figure 9 is a graph showing the composition dependence of coercive force after heat treatment of Fe-B-Mg based hard magnetic thin films. -A graph showing the relationship between substrate temperature and coercive force of a B-Mg based hard magnetic thin film, Figure 10 is a graph showing the relationship between heat treatment temperature and coercive force of an Fe-B-Bi based hard magnetic thin film, and Figure 11 is a graph showing the relationship between coercive force and substrate temperature of a Fe-B-Bi based hard magnetic thin film. -B-Ag, Fe-B-Mg and Fe-B-Bi
Coercive force and B (boron) after heat treatment of hard magnetic thin film
It is a graph showing the relationship between the content ratio of

Claims (1)

[Claims] 1. Iron (hereinafter referred to as Fe), at least one metal selected from silver (Ag), magnesium (Mg) and bismuth (Bi) (hereinafter referred to as Z), and boron (hereinafter referred to as Z); A magnetic thin film having a compositional formula of Fe _1-(X+a) Z _x B _a (0.2≦x≦0.8 0<a<0.2 x, where a is the atomic ratio). 2 Iron (hereinafter referred to as Fe), at least one metal selected from silver (Ag), magnesium (Mg) and bismuth (Bi) (hereinafter referred to as Z), and boron (hereinafter referred to as B). A method for forming a magnetic thin film on a substrate, including Fe _1-(X+a) Z _x B _a (where 0.2≦x≦0.8 0<a<0.2 x, a is the atomic ratio). A method for manufacturing a magnetic thin film, which comprises maintaining a substrate at a temperature at which atoms constituting the thin film do not significantly diffuse and move during formation of the thin film. 3 After forming a thin film by holding the substrate at a temperature at which the constituent atoms of the thin film do not significantly diffuse and move,
The method for manufacturing a magnetic thin film according to claim 2, characterized in that the material is made into a low coercive force material by heat treatment at a temperature of .degree. C. to 200.degree. 4 Iron (hereinafter referred to as Fe), at least one metal selected from silver (Ag), magnesium (Mg) and bismuth (Bi) (hereinafter referred to as Z), and boron (hereinafter referred to as B). A method for forming a magnetic thin film on a substrate, including Fe _1-(X+a) Z _x B _a (where 0.2≦x≦0.8 0<a<0.2 x, a is the atomic ratio). A method for producing a magnetic thin film, which comprises maintaining a substrate at a temperature at which atoms constituting the thin film are significantly diffused and moved during the formation of the thin film.