JPH0746652B2 - Crystalline soft magnetic thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a soft magnetic thin film which exhibits good soft magnetic properties and is suitable for magnetic head materials and the like.

[Outline of Invention]

The present invention provides a soft magnetic thin film having a novel composition containing Fe, Co, Al and Ge as main components, and particularly a soft magnetic thin film having a very high saturation magnetic flux density Bs.

[Prior Art] For example, in magnetic recording / reproducing devices such as audio tape recorders and VTRs (video tape recorders), high density and high quality of recording signals are being advanced, and it is necessary to cope with this high recording density. As a magnetic recording medium, magnetic powder such as Fe, Co,
So-called metal tapes using powders of metals such as Ni or alloys, and so-called vapor-deposition tapes made by directly depositing a ferromagnetic metal material on the base film by vacuum thin film forming technology have been developed and put into practical use in various fields. Has been done.

By the way, in order to bring out the characteristics of the magnetic recording medium having such a high coercive force, it is attempted to perform reproduction with the same magnetic head while having a high saturation magnetic flux density as the characteristics of the core material of the magnetic head. In some cases,
It is also required to have a high magnetic permeability. For example, the saturation magnetic flux density is low in a ferrite material which has been widely used as a core material of a magnetic head in the related art, and permalloy has a problem in wear resistance.

Conventionally, Fe-Al-
It is well known that a sendust alloy made of a Si-based alloy is considered to be suitable and has already been put into practical use.

However, in a material having excellent soft magnetic characteristics such as this Sendust alloy, magnetostriction λs and crystalline magnetic anisotropy K
Is preferably near zero, and the material composition that can be used for the magnetic head is determined in consideration of both values. 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, instead of the Sendust alloy, an amorphous magnetic alloy material (so-called amorphous magnetic alloy material) having a high saturation magnetic flux density with little decrease in magnetic permeability in a high frequency region
However, even with this amorphous magnetic alloy material, the saturation magnetic flux density is about 12k gauss, and since it is thermally unstable and there is a high possibility of crystallization, a temperature of 500 ° C or higher is applied for a long time. However, there is a process limitation when used in a magnetic head which requires various heat treatments such as Gaussian fusion.

[Problems to be solved by the invention]

Under such circumstances, attempts to increase the coercive force of magnetic recording media for higher quality and higher recording density are naturally limited by the limit of saturation magnetic flux density as long as the conventional core material is used. It is the current situation.

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and has the same soft magnetic characteristics (permeability, coercive force, etc.) as the Sendust alloy and has a high saturation magnetic flux density. The purpose is to provide a thin film.

[Means for solving problems]

The present inventors have obtained the following findings as a result of earnest research over a long period of time without achieving the above object.

That is, (1) In order to obtain a soft magnetic material having a saturation magnetic flux density Bs higher than that of Sendust alloy, the intersection of the line of magnetostriction λs = 0 and the line of magnetocrystalline anisotropy K = 0 is higher in the Fe concentration side. What you have to do. Moreover, it is desirable to use an element whose magnetization reduction rate is milder than that of Si or Al.

(2) From the viewpoint of reducing the magnetic moment, the rate of decrease of the magnetic moment at absolute zero is:
Per atomic% Al is −2.66μ _B , Si is −2.99μ _B , Ga is −
1.43Myu _B, because it is -1.36Myu _B in Ge, by combining these elements properly, also a combination of Fe-Si-Al is a high saturation magnetic flux density may be obtained.

(3) The addition of Co has the effect of improving not only the saturation magnetic flux density but also the corrosion resistance and wear resistance.

Therefore, in the present invention, the composition is changed to Fe-Co-Al-Ge.
As a system alloy, further investigation was added.

First, the Fe-Co-Al-Ge alloy is divided into three-component systems,
When the lines of crystal magnetic anisotropy K = 0 and magnetostriction λ _S = 0 were examined, they were as shown in FIGS. 1 (A) to 1 (C). That is, in the Fe-Al-Ge ternary system,
As shown in FIG. 1 (B), there is an intersection of K = 0 and λ _S = 0, and soft magnetic characteristics can be obtained in that region. Fe-Co-Ge3
In the original system as well, as shown in FIG.
There is an intersection of = 0 and λ _S = 0. On the other hand, Fe-Co-Al3
In the original system, the line of K = 0 exists as shown in FIG. 1 (A), but the line of λ _S = 0 is unclear and does not exist on the high Fe concentration side. Therefore, when the phase diagram of Fe-Co-Al-Ge is considered three-dimensionally, the plane of K = 0 and the plane of λ _S = 0 exist in at least the Fe high concentration side region, and the soft magnetic characteristic Is estimated to be obtained.

From the viewpoint of adding Co to the Fe-Al-Ge alloy, not only the saturation magnetic flux density but also the corrosion resistance and wear resistance are obviously improved with the increase of the Co addition amount, but the Co addition amount is If it is too large, not only the saturation magnetic flux density is significantly deteriorated, but also the soft magnetic characteristics are deteriorated.

For example, when Fe _78-x Co _x Al _13.3 Ge _8.7 was used and the relationship between the Co addition amount and the coercive force Hc after heat treatment (500 ° C. and 650 ° C.) was examined, as shown in FIG. It was found that the coercive force Hc showed a minimum value near 10 atom%, and that the soft magnetic property was remarkably deteriorated when it exceeded 20 atom%. Therefore, there is an optimum value for the amount of Co added.

As a result of further experiments in consideration of the above points, the crystalline soft magnetic thin film of the present invention shows that Fe _x Co _y Al _a Ge _b (where x, y, a, b
Represents the composition ratio in atomic%. ), The composition range is 65 ≦ x + y ≦ 85,0 <y ≦ 20,1 ≦
It is characterized in that the relationship of a ≦ 35, 1 ≦ b ≦ 35, x + y + a + b = 100 is satisfied.

That is, the soft magnetic thin film of the present invention is Fe, Co, Al, Ge as a main component, the saturation magnetic flux density Bs is much higher than the sendust alloy, and also the Fe-Si alloy It has better soft magnetic properties and corrosion resistance than steel plates. In the above composition formula, part of Al may be replaced with Ga, and part of Ge may be replaced with Si.

In the soft magnetic thin film of the present invention, it is preferable to set the composition ratio of each component element within a predetermined range, and if it is out of this range, the magnetostriction becomes large and the magnetic characteristics deteriorate.

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

Examples of the technique of this vacuum thin film forming technique include sputtering, ion plating, vacuum evaporation method, cluster ion beam method and the like.

In addition, as a method of adjusting the composition of each of the above-mentioned component elements, i) Fe, Co, Al, and Ge are weighed so as to have a predetermined ratio, and these are melted in advance in, for example, a high-frequency melting furnace to form an alloy ingot. Forming and using this alloy ingot as an evaporation source, ii) preparing evaporation sources of individual elements of each component, and controlling composition by the number of these evaporation sources, iii) of individual elements of each component Prepare evaporation sources and control the output (applied voltage) applied to these evaporation sources to control the evaporation speed to control the composition, iv) the method of implanting other elements while depositing the alloy as the evaporation source, etc. Can be mentioned.

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, Fe, Co, Al, Ge are the constituent elements of the soft magnetic thin film.
Saturation magnetic flux density Bs becomes significantly larger than that of Sendust alloy by setting these composition ratios within a predetermined range, and soft magnetic characteristics such as coercive force and magnetic permeability, corrosion resistance, and corrosion resistance. Wearability is also secured.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

First, Fe, Co, Al, and Ge 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 further machined to have a diameter of 4 inches and a thickness of 4 mm. An alloy target for sputtering was obtained.

Next, using this alloy target, a high-frequency magnetron sputtering device was used to perform sputtering under conditions of an argon partial pressure of 5 × 10 ⁻³ Torr and an input power of 300 W, and a water-cooled crystallized glass substrate (trade name of Hoya Glass Co., Ltd.) HOYA PEG3130
A thin film having a thickness of about 1 μm was obtained on C).

Further, this thin film was annealed at a temperature of Ta for 1 hour under a vacuum of 1 × 10 ⁻⁶ Torr or less and gradually cooled to obtain a soft magnetic thin film.

According to the method described above, the composition ratio of the alloy target was set to the values shown in the following table, and samples 1 to 11 were manufactured.

For 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 (1 MHz and
The value at 100 MHz), magnetostriction and corrosion resistance were investigated.

Here, the saturation magnetic flux density Bs was measured by a sample vibrating magnetometer (VSM), the coercive force Hc was measured by a BH loop tracer, and the magnetic permeability μ was measured by an 8-shaped coil type magnetic permeability meter. The film thickness of each sample is
It was determined 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 compositional analysis of each sample is performed using EPMA (Electron
Probe Micro-Analysis) method.

The corrosion resistance of each sample depended on the observation of the surface of the film surface after immersion in tap water for about one week at room temperature. This evaluation of corrosion resistance is
It was judged from 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 thick 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, the Fe-Si alloy (electromagnetic steel sheet) and Fe-Si- formed by the same method as described above are used.
With respect to the Al alloy (Sendust), each value was measured as Comparative Sample 1 and Comparative Sample 2.

From this table, it can be seen that in each sample according to the present invention, although the soft magnetic characteristics are slightly inferior to the Sendust alloy, the saturation magnetic flux density Bs is much higher. Also, it can be seen that the soft magnetic characteristics and corrosion resistance of each of these samples are superior to those of the Fe-Si alloy.

By the way, in this embodiment, after the soft magnetic thin film is deposited by sputtering, the heat treatment is performed at a temperature of 500 to 650 ° C. This is for the following reason.

For example, when the coercive force Hc of the soft magnetic thin film (film thickness 2 μm) having the composition of Fe _67.3 Co _10.2 Al _13.8 Ge _8.7 was measured while being deposited by sputtering,
It was quite high, at 17 Oersted.

Therefore, the present inventors further conducted experiments, performed heat treatment on the thin film deposited by sputtering, and investigated the relationship between this heat treatment temperature and the coercive force Hc of the obtained soft magnetic thin film and the magnetic permeability μ at 1 MHz. The results are shown in FIGS. 3 and 4.

From this Fig. 3, it is found that the coercive force Hc of the soft magnetic thin film obtained by subjecting the thin film deposited by sputtering to the heat treatment is significantly reduced, and shows a minimum value particularly when the heat treatment temperature is 450 ° C. It was Similarly, from FIG. 4, it was found that the magnetic permeability μ was improved by the heat treatment and showed the maximum value at the heat treatment temperature of 550 ° C.

In fact, for this soft magnetic thin film, before heat treatment and at a temperature of 550
When the magnetization curve after annealing / slow cooling under the condition of 1 ° C for 1 hour was obtained, as shown in Figs. 5 and 6, the temperature was 550 ° C.
It was found that the magnetic properties of the soft magnetic thin film obtained by the heat treatment in the above were significantly improved.

The optimum value of the heat treatment temperature is slightly different depending on the composition ratio,
Therefore, the heat treatment temperature Ta was determined for each sample.

〔The invention's effect〕

As is clear from the above description, Fe, Co, Al, Ge are selected as the component elements of the soft magnetic thin film, and the saturation magnetic flux density Bs superior to that of the Sendust alloy is set by setting the composition ratio of these to a predetermined value. In addition to being able to achieve this, it has become possible to secure soft magnetic properties, corrosion resistance, and wear resistance.

Therefore, by using this soft magnetic thin film as a core material of a magnetic head, for example, it is possible to sufficiently cope with a high coercive force of a magnetic recording medium, and it is possible to achieve high quality and high recording density.

[Brief description of drawings]

FIG. 1 (A) is a characteristic diagram showing a line of magnetocrystalline anisotropy K = 0 and a line of magnetostriction λ _S = 0 in the Fe-Co-Al3 ternary system, and FIG. 1 (B) is Fe-Al-Ge3. Crystal magnetic anisotropy in the original system K =
Characteristic diagram showing the line of 0 and the line of magnetostriction λ _S = 0, FIG. 1 (C)
FIG. 3 is a characteristic diagram showing a line of magnetocrystalline anisotropy K = 0 and a line of magnetostriction λ _S = 0 in the Fe-Co-Ge ternary system. FIG. 2 is a characteristic diagram showing the relation between the Co addition amount x and the coercive force Hc in Fe _78-x Co _x Al _13.3 Ge _8.7 at the heat treatment temperatures of 500 ° C. and 650 ° C. Figure 3 shows a soft magnetic thin film (Fe
_67.3 is a characteristic diagram showing the relationship between the coercive force Hc of Co _10.2 Al _13.8 Ge _8.7 ) and the heat treatment temperature, and FIG. 4 is a characteristic diagram showing the relationship between the magnetic permeability and the heat treatment temperature. FIG. 5 is a characteristic diagram showing the magnetization curve of this soft magnetic thin film before heat treatment, and FIG. 6 is a characteristic diagram showing the magnetization curve after heat treatment at 550 ° C. for 1 hour.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hideki Matsuda, 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor, Osamu Ishikawa 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Hiroshi Iwasaki 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Koichi Aso 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni -Incorporated (56) Reference JP-A-58-27941 (JP, A)

Claims (1)

[Claims] 1. A composition formula of Fe _x Co _y Al _a Ge _b (where x, y, a, and b are expressed as atomic%), and the composition range is 65 ≦ x + y ≦ 85, 0 <y ≤ 20, 1 ≤ a ≤ 35, 1 ≤
A crystalline soft magnetic thin film characterized by satisfying a relationship of b ≦ 35, x + y + a + b = 100