JPH02262306A - Soft magnetic thin film and its manufacture - Google Patents

Abstract

PURPOSE:To obtain desirable core material having high magnetic flux saturation density, low coersive force, and large permeability at high frequency, by using material having uniaxial anisotropy whose main component is one or more kinds of a specified amount of Si and Mo, a specified amount of N, and rest part Fe. CONSTITUTION:A soft magnetic thin film having uniaxial anisotropy whose main component is one or more kinds of Si and Mo equat to or less than 4atomic%, N equal to or less than 5atomic%, and the rest part Fe. An amorphous thin film composed of the above composition is heat-treated at 220 to 450 deg.C and crystallized, thereby manufacturing a soft magnetic thin film. The composition of the above soft magnetic thin film is preferably set is a range (a range EFGHI in figure) in which the following are satisfied; in the above composition range (a range ABCD in figure), one or more kinds of Si and Mo are 0.1 to 4atomic%, N is 2 to 5atomic%, Fe is 93.8 to 97.9atomic%, and the total of them becomes 100atomic%. The above amorphous thin film having the specified composition can be formed by vapor phase deposition method like, e.g., RF sputtering method.

Description

Detailed Description of the Invention 6 [Field of Industrial Application] The present invention relates to a soft magnetic thin film suitable as a material for a magnetic head.

[Background of the Invention] For example, in magnetic recording and reproducing devices such as audio tape recorders and VTRs (video tape recorders), the density and quality of recording signals are increasing, and it is necessary to cope with this increase in recording density. Fe is added to magnetic powder as a magnetic recording medium.
, Co, Ni, or other metals or alloys were used. A so-called metal tape or 5 ferromagnetic metal material was deposited directly onto the base film by vacuum thin film formation technology. So-called vapor deposition tapes have been developed and put into practical use in various fields.

[Prior art and problems to be solved by the invention] By the way, in order to exhibit the characteristics of a magnetic recording medium that achieves a predetermined coercive force, a high saturation magnetic flux density is required as a characteristic of the core material of the magnetic head. In addition to having a high magnetic permeability, if reproduction is to be performed using the same magnetic head, it is also required to have a high magnetic permeability. However, for example.

Ferrite material, which is often used as the core material of conventional magnetic heads, has a low saturation magnetic flux density.

Permalloy had problems with wear resistance.

Conventionally, Fe-A1 has been used as a core material that satisfies these requirements.
A Sendust alloy consisting of a -5i alloy is considered suitable and has already been put into practical use.

However, in materials with excellent soft magnetic properties such as this Sendust alloy, magnetostriction λS and magnetocrystalline anisotropy K
It is desirable that both of these values be around zero, and the material composition that can be used in the magnetic head is determined by taking these two values into consideration. Therefore, the saturation magnetic flux density is also uniquely determined according to this composition.

For Sendust alloys, the limit is 10 to Ilk Gauss.

Therefore, in place of the above-mentioned Sendust alloy, C is used, which has a high saturation magnetic flux density with little decrease in magnetic permeability in the high frequency range.
An o-based amorphous magnetic alloy material (so-called amorphous magnetic alloy material) has also been developed, but even this amorphous magnetic alloy material has a saturation magnetic flux density of about 14 Gauss.

On the other hand, Japanese Patent Laid-Open No. 63-299219 describes a primary soft magnetic thin film.

rFe N A (However, x, y, z are each x
y z Composition ratio is expressed as atomic %, A is Si, A, p.

Ta, B, Mg, Ca, Sr, Ba, Cr.

Mn, Zr, Nb, Ti, Mo, V, W, HfGa
, Ge, and at least one rare earth element. ), and the composition range is 0.5≦y≦5.0 0.5≦2≦7,5 x+y+z−1o.

A soft magnetic thin film characterized by: The soft magnetic thin film is formed by preparing an alloy of the element represented by A and iron, and sputtering the alloy as a target in an atmosphere containing nitrogen. For metals that do not form a solid solution with iron, such as alkaline earth metals, chips are prepared and sputtering is performed by placing the chips on an iron target. The soft magnetic thin film produced by the above method has a drawback in that it cannot have high magnetic permeability at high frequencies because it does not have -axis anisotropy.

Although it depends on the film forming conditions, crystalline materials generally tend to become columnar crystals due to self-shadowing effect during the film deposition process, and voids are formed at one grain boundary, making them magnetically inefficient. It tends to become continuous and the soft magnetic properties deteriorate. This self-shadowing effect becomes particularly noticeable when there are steps on the base or when the film is thick, such as when manufacturing a magnetic head, and there is a problem in that sufficient characteristics cannot be obtained.

An object of the present invention is to provide a soft magnetic thin film and a method for manufacturing the same, which improve the drawbacks of the above-mentioned conventional techniques.

[Means for Solving the Problems] According to the present invention, the above objects can be achieved using a primary soft magnetic thin film and a method for manufacturing the same.

■ 4 at% or less of one or more of Si and Mo and 5 at%
A soft magnetic thin film mainly composed of the following N and the remainder Fe and having uniaxial anisotropy.

■ 4 at% or less of one or more of Si and Mo and 5 atoms9
1. A method for producing a soft magnetic thin film, which comprises heat-treating an amorphous thin film mainly composed of 6 or less N and the remainder Fe at 220 to 450° C. to crystallize the amorphous thin film.

Soft magnetic thin films and amorphous thin films are preferred.

The main components are 0.1 to 4 atomic % of one or more of Si and Mo, 2 to 5 atomic % of N, and 93.8 to 97.9 atomic % of Fe.

Preferably, the heat treatment is performed in a magnetic field to obtain a soft magnetic thin film having uniaxial anisotropy.

[Preferred Embodiments and Effects] The soft magnetic thin film of the present invention contains 4 atomic % (at%) or less of Si.
and Mo (i.e., one or both of Si and Mo), 5 atomic % or less of N, and the balance Fe, and has -axis anisotropy. This composition range is shown in FIG. 1 by points A, B, C, and D.

By using one or more of Si and Mo and N at the specific abundance ratio, the coercive force He can be lowered without lowering the saturation magnetic flux density Bs below a predetermined value.

Moreover, corrosion resistance can be improved and hardness can be increased. One or more of Si and Mo exhibits a significant effect when present in an amount of, for example, 0.1 atomic %. N exhibits a significant effect when present at 1, for example, 0.1 atomic %.

Since the soft magnetic thin film of the present invention has -axis anisotropy, for example, by setting the hard axis direction of the thin film as the magnetization direction,
Magnetic permeability at frequencies higher than IMHz can be made sufficiently high. Therefore, it is suitable as a core material for magnetic heads. In order to obtain high magnetic permeability at high frequencies, uniaxial anisotropy with an anisotropic magnetic field strength of approximately 1 Oe or higher is required.
Preferably.

The strength of the anisotropic magnetic field is about 2 to 5 Oe. For example 10
When it is desired to obtain high magnetic permeability at M1lz or higher, it is more preferably about 3 to 5 Oe.

A preferable composition range of the soft magnetic thin film is that one or more of Si and Mo is 0.1 to 4 atomic %, and N is 2 to 5 (more preferably 2.5 to 5) atomic %.

Fe is in a range of 93.8 to 97.9 atomic %, and the total thereof is 100 atomic %. This composition range is the point E
, F, G, H, I in FIG. In this composition range, the coercive force lie is small (approximately 10e or less), so it is particularly suitable as a core material for a magnetic head.

In the method for manufacturing a soft magnetic thin film of the present invention, the amorphous thin film having the specific composition is heat-treated at 220 to 450° C. to crystallize the amorphous thin film to obtain a soft magnetic thin film.

The amorphous thin film with the above-mentioned specific composition has a good base coverage when formed on a base with 9 steps (so-called step coverage).
is good, but does not show good soft magnetism. However, by heat-treating this amorphous thin film at 220 to 450°C to crystallize the amorphous thin film, a good soft magnetic thin film (for example, a thin film with a coercive force He of 40e or less) can be obtained. . Therefore.

For example, even when a film must be formed on a base with a one-step difference, such as when manufacturing a magnetic head, a soft magnetic thin film with good coverage can be formed.

If the heat treatment is performed at a temperature lower than 220°C or higher than 450°C, the coercive force Ha cannot be lowered to the desired value (40e or less). A preferred heat treatment temperature range is approximately 250-400°C.

The crystal grain size is preferably 500 Å or less, more preferably 300 Å or less.

The amorphous thin film having the specific composition can be formed by, for example, a vapor deposition method such as RF sputtering.

A preferable composition range of the amorphous thin film is that one or more of Si and Mo is 0.1 to 4 atomic %, and N is 2 to 5 (more preferably 2.5 to 5) atomic %.

Fe is in a range of 93.8 to 97.9 atomic %, and the total thereof is 100 atomic %. By using an amorphous thin film in this composition range, a soft magnetic thin film with a small coercive force He (approximately 10e or less) can be manufactured.

More preferably, the heat treatment is performed in a magnetic field,
- The amorphous thin film can be manufactured by inducing axial magnetic anisotropy and crystallizing part or all of the amorphous thin film. The magnetic field is
Preferably, the magnetic field is sufficiently larger than the demagnetizing field of the amorphous thin film.

[Example] Examples 1 to 20 A Fe-SL gold alloy target was used as the atmospheric gas.
Amorphous thin films of various compositions were formed on sapphire substrates by RF sputtering using r and N2. The film composition was changed by changing the Si content of the target and the N2 partial pressure in the atmospheric gas. The sputtering conditions are as follows.

Cathode power 200W, total gas (A r + N 2 )
The pressure was 2.0 Pa. Examples 1 and 2 of the present invention were obtained by heat-treating the amorphous thin film at 350° C. for 1 hour in a magnetic field of 1 kOe.
A soft magnetic thin film of o was obtained and the B-H curve uJ was determined.

The B-H curve is measured magnetic field llm=25 (Oe),
Coercive force measured at frequency 5011z! ! c (value in the easy axis direction) and magnetic flux density B25 when a magnetic field of 250e was applied. These results are shown in Table 1. Examples 1-20
The soft magnetic thin film has B25>18KG and tlc<40e. Further, the strength of the anisotropic magnetic field is about 2 to 50 e.

Examples 21-24 Soft magnetic thin films (Examples 21-24) were produced in the same manner as Examples 1-20 except that the Fe-8i alloy target was changed to a Fe-Mo alloy target. The coercive force 11c (value in the easy axis direction) and magnetic flux density B25 of these soft magnetic thin films were determined in the same manner as in Examples 1 to 20 above. These results are shown in Table 2. Moreover, the strength of the anisotropic magnetic field of these soft magnetic thin films is about 2 to 50 e.

Comparative Examples 1 to 7 Comparative Examples include those that do not contain both Si and N, or either one (Comparative Examples 1 to 5).

Composed of Fe-3i-N and containing more than 4 atomic % of Si (
He and B25 of Comparative Example 6) and Fe-8i-N containing more than 5 atom % of N (Comparative Example 7) were determined in the same manner as above. These results are shown in Table 3.

According to Tables 1 to 3, it can be seen that by adding specific amounts of Si and N to Fe, there is a significant improvement in soft magnetism (reduction in lie).

Relationship between heat treatment temperature and coercive force
5.9 1.0 3.1 The thin film was heat treated in a magnetic field (1 hour). The coercive force 1ie (value in the easy axis direction) of these thin films after heat treatment was determined in the same manner as above. The results are shown in FIG. Second
According to the figure, it can be seen that a soft magnetic thin film with low coercive force can be obtained when heat treatment is performed at 220 to 450°C.

(Left below) Table 1 Table 2 Table 3 Relationship between average crystal grain size and coercive force Using a Fe Si target, 9 g of N2
, 0 2.0 rate 0. 2.5. R changes to 4.0 and 6.0%
A thin film was formed by the F-spanter method. These thin films are
The samples were heat-treated for 50' CI time and designated as samples ab, c and d, respectively. A thin film formed with a -N2 fraction of 6.0% and not subjected to the heat treatment was designated as sample e. Sample a does not contain N.

The compositions of samples b, c, d, and e are within the range specified by the present invention, and the N content satisfies b<c<d.

Note that the N2 fraction refers to the total pressure in the sputtering gas (Ar+N
) is the ratio of N2 partial pressure to

Average grain size and coercive force 1 of the crystals of these samples a - d
I found 1c. The average particle size was determined from the half width of the (110) peak of the X-ray diffraction of each sample shown in FIG. Note that S in FIG. 3 is the result of X-ray diffraction of iron (bulk) used as a reference sample of half width. The coercive force is B-H
It was measured with a curve tracer (50fiz, 250e). These results are shown in Table 4.

On the other hand, an attempt was made to obtain sample e in the same manner as above. However, the (110) peak of X-ray diffraction did not appear (see e in Figure 3), and Ha + (!P1 constant magnetic field) -
Even when 90 (Oe) was applied, there was almost no magnetization.

According to the above results, before the heat treatment (sample e), it was amorphous (see e in Figure 3) and did not exhibit any soft magnetism, but as a result of the heat treatment, the amorphous became microcrystallized (sample e). (see b-d in the figure), it can be seen that soft magnetism appeared.

In addition, when comparing a to d in Figure 3, the average grain size of the crystals suddenly becomes smaller with the addition of nitrogen (crystals become finer), and at the same time the coercive force He also decreases (improvement of soft magnetism). ).

Table 4 [Effects of the Invention] The soft magnetic thin film of the present invention has a high saturation magnetic flux density because the soft magnetic thin film of the present invention is mainly composed of 4 atomic % or less of one or more of Si and Mo, 5 atomic % or less of N, and the balance Fe. Bs (e.g. B25>
16KG) and low coercive force lie (He < 40e), as well as high voice resistance and high hardness. The saturation magnetic flux density Bs is FeAJ! -5i
and Fe-Ga-31-Ru based soft magnetic materials.

In addition, since the soft magnetic thin film of the present invention has uniaxial anisotropy,
For example, by setting the difficult axis direction of the thin film as the magnetization direction, the magnetic permeability at frequencies higher than IMIlz can be made sufficiently high.

Therefore, the soft magnetic thin film of the present invention is suitable as, for example, a core material for a magnetic head.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the composition range of the soft magnetic thin film of the present invention. Figure 2 shows an amorphous thin film (Fe 5i95.9 1.
3.1 is a diagram showing the relationship between the heat treatment temperature TA of O N ) and the coercive force He of the soft magnetic thin film obtained by the heat treatment. FIG. 3 is a diagram showing the results of X-ray diffraction.

Claims (5)

[Claims] (1) A soft magnetic thin film having uniaxial anisotropy and consisting mainly of one or more of Si and Mo at 4 atomic % or less, N at 5 atomic % or less, and the balance Fe. (2) 0.1 to 4 at% of one or more of Si and Mo and 2
2. The soft magnetic thin film according to claim 1, characterized in that the main components are ~5 atomic % of N and 93.8 to 97.9 atomic % of Fe. (3) An amorphous thin film mainly composed of 4 atomic % or less of one or more of Si and Mo, 5 atomic % or less of N, and the balance Fe is heat-treated at 220 to 450°C to form the amorphous thin film. A method for producing a soft magnetic thin film characterized by crystallization. (4) The amorphous thin film contains 0.1 to 4 atomic % of one or more of Si and Mo, 2 to 5 atomic % of N, and 93.8 to 97 atomic %.
4. The method of manufacturing a soft magnetic thin film according to claim 3, wherein the main component is 9 atomic % of Fe. (5) The method of manufacturing a soft magnetic thin film according to claim 3 or 4, wherein the heat treatment is performed in a magnetic field to obtain a soft magnetic thin film having uniaxial anisotropy.