JP2522284B2 - Soft magnetic thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a soft magnetic thin film, and in detail,
The present invention relates to improvement of physical properties (eg wear resistance, corrosion resistance, internal stress, etc.) and magnetic properties of Fe-Ga-Si alloy thin films.

[Outline of Invention]

The present invention is a Fe-Ga-Si alloy thin film, or Fe-Co-
In the Ga-Si alloy thin film, at least one of the constituent elements is replaced with Ru of more than 10 atomic% and less than 15 atomic% to improve physical properties such as corrosion resistance, wear resistance and internal stress. At the same time, it is intended to further improve the soft magnetic characteristics, especially the coercive force.

[Conventional technology]

In order to achieve high density and high quality recording in magnetic recording, a magnetic recording medium having a high coercive force, for example, magnetic powder is used.
So-called alloy coating type metal tapes using magnetic metal powder made of metals such as Fe, Co, Ni or alloys have been developed, including audio tape recorders, so-called 8mm VTR (8mm video tape recorder), etc. Practical application is progressing in the field of consumer magnetic recording.

Therefore, in order to sufficiently magnetize such a magnetic recording medium, the core material of the magnetic head is required to have a sufficiently high saturation magnetic flux density commensurate with the coercive force of the medium. Further, particularly when recording and reproducing are performed by the same magnetic head, it is necessary that the material has not only the above-mentioned saturation magnetic flux density but also a sufficiently high magnetic permeability in the applied frequency band.

Conventionally, as a core material satisfying such basic magnetic characteristics, an Fe-Al-Si alloy (Sendust alloy) has been known, and it is well known that it has been put to practical use.

However, in a material having excellent soft magnetic properties such as this Sendust alloy, it is desirable that both the magnetostriction λs and the crystal magnetic anisotropy K are near zero, and the material composition usable for the magnetic head is the value of both of them. Can be decided in consideration. Therefore, the saturation magnetic flux density is uniquely determined corresponding to this composition, and in the case of Sendust alloy, the limit is 10 to 11 kGauss.

Alternatively, an amorphous magnetic alloy material (so-called amorphous magnetic alloy material), which has a high saturation magnetic flux density with a small decrease in magnetic permeability in the high frequency region, has been developed in place of the above Sendust alloy. Even with alloy materials, the saturation magnetic flux density is about 12 kGauss, and since it is thermally unstable and has a high possibility of crystallization, it is not possible to apply a temperature of 500 ° C or higher for a long time. When used in a magnetic head that requires various heat treatments, there are process restrictions.

[Problems to be solved by the invention]

Under such circumstances, researches on soft magnetic materials exhibiting further excellent soft magnetic properties have been advanced. For example, the applicant of the present application has previously described in Japanese Patent Application No. 60-77338 that Fe, Ga, Si as main components. Proposed Fe-Ga-Si soft magnetic thin film with high saturation magnetic flux density, and Fe-Ga-Si soft magnetic thin film in which a part of Fe was replaced by Co in Japanese Patent Application No. 60-218737. did.

The present invention aims to further improve the physical properties and soft magnetic properties of this Fe-Ga-Si based soft magnetic thin film.

That is, the present invention provides a soft magnetic thin film having a high saturation magnetic flux density superior to that of Sendust alloy, showing a lower coercive force, and having excellent properties in terms of wear resistance, corrosion resistance, and internal stress. With the goal.

[Means for solving problems]

The inventors of the present invention, as a result of earnest research to solve the above problems, addition of a predetermined amount of Ru is effective in improving corrosion resistance and wear resistance, and is also advantageous in terms of coercive force and internal stress. We have come to the knowledge that there is.

The soft magnetic thin film of the present invention was completed on the basis of such findings, and has a composition of Fe _a Ga _b Si _c (where a, b, and c are each represented by the composition ratio in atomic%). The composition range is 68 ≦ a ≦ 84, 1 ≦ b ≦ 23, 9 ≦ c ≦ 31, a
The soft magnetic thin film with + b + c = 100 is characterized in that at least one of Fe, Ga, and Si is replaced with Ru of more than 10 atomic% and 15 atomic% or less. In the above composition formula, Fe
May be partially replaced with 0 to 15 atomic% of Co.

The addition of Ru is extremely effective in improving the corrosion resistance and the wear resistance, and the composition of the soft magnetic thin film is Fe _76-x Ru _x Ga _7.5 Si _16.5 ... (I) (where the numerical values represent atomic% respectively). .), The amount of wear was investigated by changing the amount x of Ru added, and as shown in FIG. 1, a remarkable effect in reducing the amount of wear was shown as the amount x of Ru added was increased. For example, the addition amount x of Ru is 10
When it exceeded the atomic percentage, it showed significantly better wear resistance than Sendust. However, there is a limit to the improvement of wear resistance by the addition of Ru, and even if the addition amount x of Ru is increased too much, no further improvement is observed. Here, the amount of wear was a value after the above soft magnetic thin film was processed into a magnetic head and the magnetic tape was run for 30 hours.

Experiments have also revealed that the addition of Ru is advantageous in terms of coercive force Hc and internal stress.

First, the composition of the soft magnetic thin film (thickness 7 μm) is the same as in (I) above.
When the composition x of Ru was changed to 0, 4, 10 atom% and the dependence of the coercive force Hc at room temperature on the heat treatment temperature Ta was investigated, as shown in FIG. Coercive force Hc
Was found to be reduced, and there was little deterioration at high temperatures.
In particular, when the Ru addition amount x was set to 10 atomic%, no deterioration of the coercive force Hc was observed even when the heat treatment was performed at a high temperature, and the lowest coercive force Hc was shown at any heat treatment temperature.
Therefore, when the heat treatment temperature was set to 550 ° C. and the dependence of the coercive force Hc on the Ru addition amount x was examined, the results shown in FIG. 3 were obtained.

Next, the film thickness of the soft magnetic thin film having the same composition is 5 μm.
Then, the dependence of the film internal stress σ on the sputtering gas pressure (Argon gas pressure) P _Ar was examined for two types of sample thin films in which the Ru addition amount x was 4 atom% and 10 atom%. Results are shown in FIG. In general, there is an optimum value of the sputtering gas pressure P _{Ar in} order to obtain good soft magnetic characteristics, and in this case, it is around 4 to 6 mTorr. Comparing the film internal stress σ in this range, it is clear that the film stress is smaller when the amount of Ru added is 4 at% than when it is 10 at%, and film peeling from the substrate after sputtering or the film itself It turned out that the cracks hindered.

Therefore, the sputtering gas pressure that gives the best magnetic characteristics
When fixed to P _Ar (5 mTorr) and the composition of the film was set to fe _77-x Ru _x Ga _8.5 Si _14.5 ... (II), the internal stress σ of the film was examined when the amount x of Ru added was changed. As shown in FIG. 5, the Ru addition amount x is 10 to 12
The internal stress showed the minimum value at around atomic%.

On the other hand, when Ru is replaced with, for example, Fe, the saturation magnetic flux density Bs is slightly decreased, and about 0.138 k per 1 atomic% replacement of Ru and Fe.
G (kilo gauss) decreases. The saturation magnetic flux density Bs of the composition showing the best soft magnetic characteristics of the Fe-Ga-Si soft magnetic thin film is about 13 kG, so that when the substitution amount of Ru and Fe exceeds 15 atomic%, the saturation magnetic flux density Bs is This is less than 11 kG, and there is no great merit regarding the saturation magnetic flux density Bs as compared with the sendust-based alloy (Fe-Al-Si-based alloy).

Based on the above experimental results and ideas, the amount of Ru added in the present invention is more than 10 atomic% and 15 atomic% or less. 10 added
If it is less than atomic%, sufficient effects cannot be expected to improve wear resistance, coercive force, internal stress, etc. On the other hand, if the amount added exceeds 15 atomic%, soft magnetic properties deteriorate and saturation magnetic flux density decreases. This is because the original meaning is lost in terms of superiority to sendust-based alloys.

On the other hand, in the soft magnetic thin film of the present invention, in order to secure predetermined magnetic characteristics, the basic components Fe, Ga, and Si are Ga1 to 23 atom%, Si9 to 31 atom%, and the balance Fe. However, the Fe content is in the range of 68 to 84 atomic%. If these basic components deviate from the above composition ranges, it becomes difficult to secure magnetic characteristics such as saturation magnetic flux density, magnetic permeability, and coercive force.

Also, when Co is added, it is necessary to improve the saturation magnetic flux density, corrosion resistance and wear resistance, and to secure soft magnetic characteristics.
It is preferable that the amount of substitution with respect to is suppressed to 0 to 15 atom%.
That is, when the composition is Fe _a Co _b Ga _c Si _d (where a, b, c, and d are each the composition ratio expressed as atomic%), the composition range is 65 ≦ a + b ≦ 850 ≦ b ≦ 15 1 ≦ c ≦ 35 1 ≦ d ≦ 35 a + b + c + d = 100. In any case, part of Ga may be replaced with Al, and part of Si may be replaced.
It may be replaced by Ge.

The soft magnetic thin film of the present invention is obtained by substituting Ru for at least one of the above-mentioned basic components within the above range.

Various methods are conceivable as the method for manufacturing the above-mentioned soft magnetic thin film, and among them, the vacuum thin film forming technique is preferable.

This vacuum thin film forming technique includes sputtering, ion plating, vacuum deposition, cluster
An ion beam method and the like can be mentioned.

In addition, as a method for adjusting the composition of each of the above-mentioned component elements, i) Fe, Ru, Ga, Si and, if necessary, Co are weighed so as to have a predetermined ratio, and these are preliminarily measured, for example, in a high frequency melting furnace. And melted to form an alloy ingot,
A method of using this alloy ingot as an evaporation source, ii) a method of preparing evaporation sources of individual elements of each component, and a method of controlling the composition by the number of these evaporation sources, iii) preparation of evaporation sources of individual atoms of each component , A method of controlling the vaporization speed by controlling the output (applied voltage) applied to these vaporization sources, iv) a method of implanting another element while vapor-depositing the alloy as the vaporization source, and the like.

The soft magnetic thin film formed by the above-mentioned vacuum thin film forming technique has a slightly higher coercive force in the state as it is, and good soft magnetic characteristics cannot be obtained. It is preferable to remove and improve the soft magnetic properties.

[Action]

In this way, Ru to the Fe-Ga-Si-based alloy containing Fe, Ga, and Si as the basic components or the Fe-Co-Ga-Si-based alloy containing Co is added.
Especially, when the amount of addition exceeds 10 atomic%, it significantly acts in terms of improvement of wear resistance, corrosion resistance, reduction of coercive force, elimination of internal stress of film, and the like. Further, the reduction of the saturation magnetic flux density due to the addition of Ru is remarkably small, and if the addition amount is suppressed to 15 atomic% or less, the saturation magnetic flux density higher than that of the Sendust alloy can be secured.

〔Example〕

Hereinafter, specific examples of the present invention will be described,
The invention is not limited to this example.

First, Fe, Ru, Ga, Si, and Co are weighed so that each has a predetermined composition ratio, melted and cast in a high-frequency induction heating furnace in an argon atmosphere, and then machined by a surface grinder. An alloy target for sputtering with a diameter of 4 inches and a thickness of 4 mm was obtained.

Next, using this alloy target, an argon partial pressure of 5 × 10 ⁻³ Torr, by a high frequency magnetron sputtering device,
Crystallized glass substrate water-cooled by sputtering under the condition of input power of 300 W
A thin film having a film thickness of about 1 μm was obtained on 130C).

Furthermore, this thin film was Ta under a vacuum of 1 × 10 ^-6 Torr or less.
It was annealed at the following temperature for 1 hour and gradually cooled to obtain a soft magnetic thin film.

According to the method described above, the composition ratio of the alloy target is set to the values shown in the following table, and the sample 1 to the sample 4 are set.
Was produced.

With respect to each of the obtained samples, the film composition of the soft magnetic thin film was analyzed, and the saturation magnetic flux density Bs, coercive force Hc, magnetic permeability μ (value at 1 MHz), wear amount and corrosion resistance were examined.

Here, the saturation magnetic flux density Bs is the sample vibration magnetometer (VSM),
Coercive force Hc is AC BHz loop tracer with 10Hz, permeability μ
Was measured with an 8-shaped coil permeability meter. The film thickness of each sample was obtained by thinly depositing aluminum on the surface of the sample and measuring the step between the film and the substrate with a multiple interference film thickness meter. In addition, the composition analysis of each sample
(Electron Probe Micro-Analysis) method.

The amount of wear was determined as follows. That is, first, a pseudo head made of ferrite was prepared as a substrate, and a soft magnetic thin film having a film thickness of 18 μm was formed on the tip of the head chip under the same sputtering conditions as described above. This pseudo head is a video tape recorder with a tape width of 1 inch (relative speed 2
5.6 m / sec) with a track width of 0.5 mm and a protrusion of 80 μm, and a magnetic tape containing γ-Fe ₂ O ₃ as magnetic powder was run for 30 hours, and the amount of film reduction was observed with a microscope. I asked.

The corrosion resistance of each sample was based on the observation of the surface of the film surface after being immersed in 1N saline for 1 week at room temperature. The evaluation of the corrosion resistance was made based on the following surface conditions.

A: There is no change in the film surface and the mirror surface is maintained.

B: A state where thin rust is generated on the film surface.

C: A state where thin rust is generated on the film surface.

D: Rust generated to such an extent that the film itself disappears.

The results are shown in the table below. For comparison, a Fe-Ga-Si alloy (not including Ru) and Fe formed in the same manner as the above method were used.
With respect to —Ga—Si—Ru alloy (however, the amount of Ru added is out of the range of the present invention) and Fe—Al—Si alloy, each value was measured as Comparative Sample 1 to Comparative Sample 5.

From this table, in each of the samples to which the present invention is applied, a remarkable improvement effect can be seen particularly in the corrosion resistance, the wear amount, and the coercive force, and the saturation magnetic flux density and the magnetic permeability are Fe-
It was found to be comparable to Al-Si alloys.

On the other hand, in the samples containing a small amount of Ru added (Comparative Samples 3 and 4), the effects of improving the amount of wear and the coercive force were slightly insufficient. The sample with a Ru content of more than 15 atomic% (Comparative sample 5) had a saturation magnetic flux density of Fe-Al.
-It was below the Si alloy.

〔The invention's effect〕

As is clear from the above description, Fe, Ga, and Fe-Ga-Si-based alloys having Si as basic components or Fe-Co with Co added.
By adding more than 10 atomic% of Ru to the —Ga—Si alloy, the corrosion resistance and wear resistance are significantly improved, and the internal stress of the film can be suppressed. At the same time, the soft magnetic properties, especially the coercive force, are improved, and the coercive force becomes extremely small.

Further, the reduction of the saturation magnetic flux density due to the addition of Ru is smaller than that of the other additive elements, and by suppressing the addition amount to 15 atomic% or less, the saturation magnetic flux density higher than that of the Fe-Al-Si alloy is secured. It

Therefore, it is possible to provide a soft magnetic thin film that is excellent in practical properties such as corrosion resistance, wear resistance, and film internal stress, and is also excellent in soft magnetic properties, particularly coercive force and saturation magnetic flux density.
It can be said that it has extremely high practical value as a core material of a magnetic head.

[Brief description of drawings]

Figure 1 shows Ru when the film composition is Fe _76-x Ru _x Ga _7.5 Si _16.5.
FIG. 2 is a characteristic diagram showing the relationship between the addition amount x of Al and the amount of wear. FIG. 2 is a characteristic diagram showing the change in the heat treatment temperature Ta dependence of the coercive force Hc due to Ru substitution, and FIG. It is a characteristic view which shows the relationship between Ru addition amount x and coercive force Hc when it is set to ° C. FIG. 4 is a characteristic diagram showing the sputtering gas pressure P _Ar dependence of the internal stress σ of the film when the added amount of Ru is 4 atom% and 10 atom%, and FIG. 5 shows the film composition of Fe _77-x Ru. _x Ga _8.5 Si _14.5 and sputtering gas pressure 5 mTorr, Ru addition amount x
FIG. 6 is a characteristic diagram showing the relationship between the film internal stress σ and

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Aso, 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo, Sony Corporation (56) References Japanese Patent Publication 7-89527 (JP, B2)

Claims (2)

(57) [Claims] 1. A composition formula of Fe _a Ga _b Si _c (where a, b, and c are each expressed as an atomic percentage), and the composition range is 68 ≦ a ≦ 84,1 ≦ b. ≤23,9 ≤c≤31, a + b + c = 10
In the soft magnetic thin film of 0, at least one of Fe, Ga, and Si is replaced with Ru of more than 10 atomic% and 15 atomic% or less. 2. A composition formula of Fe _a Co _b Ga _c Si _d (where a, b, c, and d are each represented by the composition ratio in atomic%), and the composition range is 65 ≦ a + b ≦ 85. , 0 <b ≦ 15,1 ≦ c ≦ 35,1 ≦
A soft magnetic thin film in which d ≦ 35, a + b + c + d = 100, wherein at least one of Fe, Co, Ga, and Si is replaced by Ru in an amount of more than 10 atomic% and 15 atomic% or less.