JPS61240612A - Soft magnetic thin film - Google Patents

Abstract

PURPOSE:To obtain a soft magnetic thin film having high saturated magnetic flux density and superior anti-corrosiveness, by selecting Fe, Co, Si as constituent elements of the soft magnetic thin film and setting up the composition ratio of them within a specific limited composition range. CONSTITUTION:The composition comprises Co 9-15atom%, Si 19-23atom%, and Fe as the remaining part. When the Si content becomes less than 19atom% or larger than 23atom%, a coercitive force of a produced soft magnetic thin film becomes more than 2.0 Oersteds. Particularly, with the composition range being made Si 20-21.5atom% and Co 11-13.5atom%, the coercitive force can be attained to less than 0.7 Oersted, to make magnetostriction curves crossed with each other. Moreover, because the too large Si content causes a saturated magnetic flux density to be lowered, the Si content should be preferably restricted to the degree of 23atom%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a soft magnetic thin film that exhibits good soft magnetic properties and is suitable for magnetic head materials and the like.

[Summary of the invention]

The present invention provides a composition range that exhibits extremely excellent soft magnetic properties especially when used as a thin film in soft magnetic materials mainly composed of Fe, Co, and Si, and provides a magnetic material for magnetic recording media with high coercive force. The present invention aims to provide a soft magnetic thin film suitable as a hesodo core material.

[Conventional technology]

For example, in magnetic recording and reproducing devices such as audio tape recorders and VTRs (video tape recorders), the recording signal density and quality are being improved. As a magnetic recording medium, a so-called metal tape using magnetic powder made of a metal or alloy such as Fe, Co, or Ni, or a ferromagnetic metal 4A material directly deposited on the base fill J1 by vacuum thin film forming technology. So-called vapor deposition tapes have been developed and put into practical use in various fields.

By the way, in order to make use of the characteristics of a magnetic recording medium with such a high coercive force, it is necessary that the core material of the magnetic material has a high saturation magnetic flux density and that it is possible to perform reproduction with the same magnetic head. In this case, it is also required to have high magnetic permeability. for example,
Ferrite grains, which have been commonly used as the core material of conventional magnetic heads, have a low saturation magnetic flux density, and permalloy has a problem with wear resistance of 1 (1).

Conventionally, Fe-
Centast alloys made of Aff-3i series alloys are considered suitable and have already been put into practical use.

However, this -1 pin dust alloy has -11, magnetostriction λS and 'A material with excellent soft magnetic properties.
It is desirable that the magnetic anisotropy K of the magnetic anisotropy K of the magnetic heel is close to 1, and the composition of the material that can be used for the magnetic heel 1 is determined by taking these two values into consideration. Therefore, the saturation magnetic flux density is uniquely determined depending on the composition of the metal, and in the case of Sendust alloy, the limit is 10-11 Gauss.

Alternatively, an amorphous magnetic alloy material Gimi 1 (so-called amorphous magnetic alloy material) has been developed, which is similar to the above-mentioned Sendust alloy and has a high saturation magnetic flux density with little decrease in magnetic permeability in the high frequency range. Even amorphous magnetic alloy materials have a saturation magnetic flux density of about 12 Gauss, and are thermally unstable and have a high possibility of crystallization, so it is impossible to apply temperatures above 500'C for a long time. For example, if it is used in a magnetic head that requires various heat treatments such as glass fusing, there will be a T-shape limitation.

Under these circumstances, research into soft magnetic materials that exhibit even better soft magnetic properties has progressed.
0 year), Fe, Co.

It has been reported that a Fe-Co-3i alloy containing St as a main component exhibits good soft magnetic properties.

[Problem that the invention seeks to solve]

However, the above-mentioned Fe-Co-Si alloy material
It was extremely brittle and impractical, making it difficult to use it directly as a core material for magnetic heads.

For this reason, attempts to increase the coercive force of magnetic recording media in order to achieve higher quality and higher recording density are naturally constrained by the IIIA field of saturation magnetic flux density, as long as the conventional core + I material is used. The current situation is that

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and has the object of providing a Φu+ magnetic thin film that overcomes the high saturation magnetic flux density than Sendust alloy and has an excellent corrosion resistance of 1η. do.

[Failure to solve the problem]

As a result of extensive research over a long period of time, the inventors of the present invention have determined that the above objective cannot be achieved. (2) Thin J-simulated Fe-C
It has been found that o-3i alloys exhibit excellent soft magnetic properties only in a very limited composition range that is different from ordinary Fe-Co-Si alloys.

The present invention was completed based on such knowledge, and includes 9 to 15 atom% of Co, 19 to 23 atom% of Si,
A soft magnetic thin film having a composition with the remainder being Fe achieves high saturation magnetic flux density, high corrosion resistance, low coercive force, etc.

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 deviates from this range, the magnetic properties will deteriorate.

For example, even if the Si content is less than 19 atomic %, or conversely even if it exceeds 23 atomic %, the coercive force of the resulting soft magnetic thin film will exceed 2.0 oersteds, making it suitable for use as a core material for magnetic heads. It becomes impossible. Similarly, even if the Co content is less than 9 at %, or conversely even if it exceeds 15 at %, the coercive force will exceed 2.0 oersteds. In particular, S
By setting the composition range to i20 to 21.5 at% and Co11 to 13.5 at%, a coercive force of 0.7 oerstes or less is achieved, and the zero magnetostriction curve also intersects in this region, which is an extremely preferable range. I can say that.

Furthermore, if the content of Si becomes too large, the saturation magnetic flux density will decrease, so from this point of view as well, it is preferable to suppress the content of Si to about 23 at %.

As a method for manufacturing the soft magnetic thin film, a vacuum thin film forming technique is preferably used.

Vacuum oil 1 modeling techniques include sputtering, ion blasting, and vacuum evaporation.

Examples include the cluster ion heat method.

In addition, the horn method for adjusting the K and 11 elements of each component element described in 1. A method in which alloy ingots are formed by melting in a furnace, etc., and this alloy ingot is used as an evaporation source. (B) A method in which evaporation sources for individual elements of each component are prepared, and the number of these evaporation sources is (C) A method for controlling the composition by preparing evaporation sources for individual elements of each component and controlling the output (applied voltage) applied to these evaporation sources to control the evaporation speed 1; (D) Examples include a method of implanting other elements while depositing an alloy as an evaporation source.

Note that a soft magnetic thin film that has been thinned by a double vacuum thin film forming technique, etc., has a slightly high coercive force in its original state, and good soft magnetic properties cannot be obtained. It is preferable to remove the distortion and improve the soft magnetic properties.

``The 7 quality conditions for the heat treatment in item 1 are 400°C or higher.

[Effect]

In this case, Fe is used as a constituent element of the soft magnetic thin film.

By selecting Co and Si and setting their compositional peaks within a predetermined range, the saturation magnetic flux density Bs becomes significantly larger than that of Sendas alloys, etc., and soft magnetic properties such as coercive force and magnetic permeability are improved. It also ensures corrosion resistance.

〔Example〕

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

Example 1 Each of electrolytic iron, electrolytic cobalt, and metal silicon was
3. It was weighed so that it had an atomic ratio of ac O12.9s i 23.7, vacuum melted in an aluminum crucible using a high frequency induction heating furnace, and cast in a copper mold with a diameter of 105 yen to form a mother moon for Kukesoto. Obtained. In this case? The capacity was 600g.

Then, from this Il shrine, using a surface grinder, a thickness of 5 mm was made.
A sputtering machine was prepared.

Using this alloy target, a thin film was formed using a conventional sputtering device. Here, optically polished crystallized glass was used as the substrate, and the Ar gas pressure was set to 8
After preliminary sputtering for 1 hour at 10-'' Torr and input power of 150 W, film formation was performed under the same conditions.

When the thickness of the obtained thin film was examined, the average thickness was 1.4.
It was μm. The film thickness was determined by depositing a thin layer of aluminum on the surface of the sample and measuring the difference in level between the film and the substrate using a multi-interference film thickness meter.

Moreover, the average composition of the obtained thin film is Febb, +qCO
It was measured as 12,9113 Ito, sx (atomic ratio).

The measurement of this film composition is performed using E PMA (Electr
on probe (formerly known as cro-8 analysis) method.

In order to examine the soft magnetic properties of the thin film thus obtained, an AC BH curve (hysteresis curve) was measured.

FIG. 1(a) shows the B-8 curve in a state where sputtering is still being performed. The measurement frequency was 1711z and the maximum applied magnetic field was 100 oersteds.

From FIG. 1(a), it was found that the coercive force showed a high value of about 2008, and good soft magnetic properties could not be obtained if only sputtering was performed.

Therefore, in order to remove the distortion of the film introduced during sputtering, the thin film sample obtained by the previous sputtering was heat-treated in a vacuum furnace evacuated to lx]]0-6T'or. The heat treatment temperature was 500° C., and the temperature was raised over 30 minutes, held for 1 hour, and then cooled in a furnace over 2 hours. The AC B-H curve after heat treatment is shown in FIG. 1(b). In this case, the measurement frequency is 1411z and the measurement magnetic field is 50e.

It can be seen from FIG. 1(b) that the soft magnetic properties of the N film obtained by sputtering are significantly improved by this heat treatment. In the case of this example, this heat treatment resulted in a coercive force of 0.70e.

Example 2 In order to clarify the composition range in which good soft magnetic properties can be obtained in a Fe-Co-Si alloy thin film, the previous Example 1 was used.
Alloy targets with various atomic ratios were prepared using the same method as described above, and Ar gas pressure was 5 to 10×10−.
``Various compositions obtained by high frequency sputtering method at Torr and input power range of 150-200W'' 4 I
An IJ was prepared.

The compositional analysis of each thin film was performed using the same E as described in Example 1 above.
The PMA method was used, and the heat treatment was performed in the same manner as described in Example 1 above, and the coercive force after the heat treatment was determined from the AC B-H curve.

FIG. 2 shows the relationship between the composition of the obtained thin film and the coercive force Hc after heat treatment.

From FIG. 2, it can be seen that when Fe--Co--3i alloy is used as a thin film, good soft magnetic properties can be achieved only within an extremely narrow composition range.

Furthermore, in order to evaluate the magnetostriction λS of the obtained thin film, changes in the shape of the B-8 curve when bending stress was applied to the substrate were investigated. The case where the B-8 curve slopes when compressive stress is applied in the measurement direction of the B-8 curve is defined as λs>O, and conversely, the case where the B-8 curve slopes when tensile stress is applied is defined as λs<Ol.
The case where no change appeared in any case was defined as λS=O. This measurement method is based on the principle that the slope of the B-8 curve, that is, the magnitude of the anisotropic magnetic field, is proportional to the product of the magnetostriction constant and the stress. - λs-0 determined by such a method in Fig. 2;
The area showing this is indicated by a curve S. In this second figure, the song!
In the region to the right of as, λs<O, and in the region to the left of the curve S, λs>0.

Furthermore, when applying such an alloy thin film, magnetic permeability in a high frequency region is an important characteristic. Therefore, as an example of this, Fe x,zCo +z, which showed good soft magnetic properties within the composition range described in this example.

The high frequency transmittance of a thin film having a composition of Si+q,a (atomic ratio) was measured.

FIG. 3 shows the frequency characteristics of the effective magnetic permeability of this thin film. Note that the thickness of this thin film is 2.0 μm, and 5
It was heat treated at 00°C for 1 hour. Further, in measuring the magnetic permeability, a high frequency magnetic permeability measuring device was used. This device uses an appropriate pickup coil to detect changes in magnetic flux due to a thin film sample placed in a high-frequency magnetic field, and by combining it with a unique circuit system, it can evaluate effective magnetic permeability over a range of 1 MHz to 100 Mllz with high precision. It is possible to do so.

Using similar methods, the magnetic permeability and coercive force of the various thin films obtained in this example were measured. The results are shown in the table below.

(Left blank space below) Table As is clear from this table and FIG. 3, the soft magnetic thin film obtained in this example exhibits excellent magnetic permeability even in the high frequency range.

Furthermore, the saturation magnetic flux density at room temperature was measured using a vibrating sample magnetometer for thin films having compositions in the composition range that showed good soft magnetic properties as a result of the measurements of each of the magnetic properties described above. FIG. 4 shows the change in saturation magnetic flux density as the amount of Si increases when the amount of Co is fixed at 13 at %.

From this Figure 4, it can be seen that the Fe-Co-3t alloy thin film has an extremely high saturation magnetic flux density that exceeds that of the Sendust alloy, and although this saturation magnetic flux density decreases as the amount of Si increases, for example, Fe67, ZcOI exhibiting soft magnetic properties
It was found that a thin film having a composition of :LOs'19.8 (atomic ratio) had a saturation magnetic flux density of 14.5 kG.

Example 3 As described in Example 1 and Example 2 above, Fe-C
It is clear that good soft magnetic properties are achieved in o-3i alloy thin films after heat treatment.

Therefore, in order to investigate the effect of heat treatment temperature on soft magnetic properties, we measured the change in coercive force after holding each temperature for 1 hour from 350 to 700"C. The results are shown in Figure 5. .

In addition, in this FIG. 5, curve a is Feb3rOCO
+a, oS I 23. . (Atomic ratio, same below) 1 curve is F e64. zCO+z, +S iZl, S+ curve C is Fe6e.

COz, oS j 21.0 + curve d is F e67, z
CO+a, oSi+1. The changes in the thin film having the composition a are shown respectively.

As can be seen from FIG. 5, in the soft magnetic thin film of the present invention, the effect of heat treatment is noticeable from at least 400°C, and it can be seen that heating at temperatures of preferably 500°C or higher is effective.

Embodiment 4 When the soft magnetic thin film of the present invention is applied, for example, as a core material of a magnetic head, it is required to have not only soft magnetic properties but also high corrosion resistance.

Therefore, in order to evaluate the corrosion resistance of the soft magnetic thin film of the present invention, some of the thin film samples prepared in Example 2 were selected, and these thin film samples were placed in city water kept at room temperature for 130 minutes. The state of rust on the surface was visually observed.

The evaluation results are shown in Figure 6.

In Fig. 6, ○ marks are those whose surfaces maintained a mirror surface, Δ marks are slightly cloudy or partially rusted, and × marks are completely covered with rust. are shown respectively. Further, in FIG. 6, a region where the coercive force becomes 10e or less after heat treatment at 500° C. for 1 hour is also shown by a broken line.

From FIG. 6, it can be seen that in the region of the present invention exhibiting good soft magnetic properties, corrosion resistance is also excellent.

Comparative example f? A binary alloy thin film having a composition of eBBsl+□ was prepared in the same manner as in Example 1, and was subjected to heat treatment in the same manner as in Example 1, but the coercive force after heat treatment was 1 to 20e and 100 Mllz. The effective magnetic permeability was around 250.

Furthermore, when the corrosion resistance of this thin film was evaluated using the same method as in Example 4, it was found that it was completely covered with rust after 9 hours, and more than 50% of the thickness had disappeared after 30 hours.

〔Effect of the invention〕

As is clear from the above explanation, Fe, Co, and Si are selected as the component elements of the soft magnetic thin film, and their composition ratios are set within a very limited specific composition range that is different from when used as a bulk material. By doing so, it is possible to achieve a saturation magnetic flux density Bs that far exceeds that of Sendust alloy, amorphous magnetic alloy, etc. At the same time, good soft magnetic properties have been achieved, including high magnetic permeability in the high frequency range and extremely low coercive force and magnetostriction.
Furthermore, it has excellent corrosion 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 the increase in coercive force of a magnetic recording medium, and it becomes possible to achieve higher quality and higher recording density.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are characteristic diagrams showing the B-0 curve (hysteresis curve H&) of the soft magnetic thin film to which the present invention is applied, and FIG. 1(a) shows the B-0 curve before heat treatment. -0 curve, 1st
Figure (b) does not show the B-0 curve after heat treatment. Figure 2 shows Fe-Co-3i alloy 7jJIf! FIG. 3 is a characteristic diagram showing the relationship between the composition of F e 67.2CO+3.oS t 19.
A characteristic diagram showing the frequency characteristics of the effective magnetic permeability of a thin film with a composition of 1+ (atomic ratio). Figure 4 shows the change in the saturated Gn flux density as the Sl content increases when the Co content is fixed at 13 at%. The characteristic diagram shown in FIG. 5 shows the soft magnetic thin film of the present invention.
FIG. 3 is a characteristic diagram showing changes in coercive force after being held at each temperature from 50° C. to 700° C. for 1 hour. FIG. 6 is a characteristic diagram showing the relationship between the composition and corrosion resistance of a Fe-Co=Si alloy thin film.

Claims (1)

[Claims] Co9-15 at%, Si19-23 at%, balance Fe
A soft magnetic thin film with a composition consisting of: