JPS62120460A - Material for soft magnetic thin film - Google Patents

Abstract

PURPOSE:To lower the coefft. of thermal expansion of a thin Fe-Si-Al alloy film and to improve the magnetic characteristics by adding specified amounts of Nb and a rare earth element to a material for the alloy film. CONSTITUTION:The alloy composition of a material for a soft magnetic thin film is composed of, by weight, 2-8% Si, 0.5-2.5% Al, 0.5-6% Nb, 0.01-2% rare earth element and the balance Fe. Ce may be selected as the rare earth element. A thin alloy film made of the material has a low coefft. of thermal expansion, so it has superior adhesion to a substrate and increased mechanical strength. The film also has high magnetic permeability and superior corrosion resistance.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to the improvement of soft magnetic thin film materials made of Fe-8i-Al alloy used in thin film magnetic elements, such as thin film magnetic heads and thin film magnetic sensors. In particular, the present invention relates to a soft magnetic thin film material that has a small coefficient of thermal expansion and excellent magnetic properties.

<Prior art> In recent years, in the field of magnetic applications, magnetic cores have tended to become smaller, have higher frequencies, and have higher densities.Especially in the field of magnetic recording, for example,
As seen in fixed head digital audio, PCM, perpendicular magnetic recording, etc., as recording density increases, the trend is toward narrower tracks, shorter wavelengths, and higher frequency bands.

Thin plates and ribbons of soft magnetic materials are being used to reduce the size and increase the frequency of magnetic elements, but these materials cannot be said to be sufficiently compatible. Therefore, soft magnetic thin films manufactured by the suction method, vapor deposition method, plating method, etc. are attracting attention. Although this thin film is inferior in coercive force and magnetic permeability in the low frequency range, it is significantly superior in the high frequency range due to its advantageous shape. That is, the thin film can significantly reduce the eddy current loss characteristic of metal materials with low electrical resistance, and therefore can suppress the decrease in magnetic permeability in the high frequency band.

Generally, a thin film is a main component of a thin film magnetic element, and among them, a soft magnetic thin film determines the performance of the magnetic element. This includes Ni-Fe alloy, Fe-8i-At
Prototypes of amorphous magnetic thin films such as Co--Zr alloys and Co--Zr alloys have been produced and studied.

<Problems to be Solved by the Invention> By the way, each of the above-mentioned soft magnetic thin films has advantages and disadvantages, and reports to date have not necessarily yielded satisfactory results. Among them, Fe-5t-AA alloy is
Although it is expected to be a material with a high saturation magnetic flux density that can be used to increase the coercive force of media, it has the problem of low magnetic permeability when made into a thin film. This is due to the difference in thermal expansion coefficient between the thin film and the substrate, as will be described later.

In addition, although this alloy has high mechanical strength, when used as a thin film element, especially a thin film head, it is necessary to perform microfabrication after film formation, making it more difficult to handle and process. It is necessary to increase mechanical strength.

Furthermore, this magnetic thin film is rarely used on its own; rather, alloy films are formed on substrates made of magnetic or non-magnetic materials by the various methods mentioned above, and used as components in a wide range of fields. . This substrate material is M
n-Zn ferrite, crystalline glass, etc. are used. The coefficient of thermal expansion of this substrate material is 100-120
10-7. 'C Te, the largest one is 140~1
- Approximately 15X10 /'C. On the other hand, Fe −
The coefficient of thermal expansion of the Fe-9~11%Si-5~7% At alloy (the ratio represents the weight ratio, the same applies hereinafter), which is the most typical alloy composition range among the 81-Al alloys, is approximately 175.
X I F7. /'C and 30 compared to that of the board.
~75 X 10-7. 'C is the only one who is acting like a dog.

(The coefficient of thermal expansion here is a value in the temperature range of 40 to 60°C. The same temperature range will be used hereinafter unless otherwise specified.) In order to minimize the contribution of thermal stress via magnetostriction to magnetic properties. It is better to make the thermal expansion coefficients of the substrate and the magnetic thin film the same or close to each other. Here, if the thermal expansion coefficients of the substrate and the magnetic thin film are different, the following problem occurs.

1) To improve magnetic permeability when forming a thin film, the substrate may be heated to 200 to 400°C. in this case,
After the film is formed, the thin film is cooled together with the substrate, but at this time, strain due to thermal contraction is introduced into the thin film, resulting in a decrease in magnetic permeability.

This introduced distortion cannot be easily released even if some processing is performed.

2) Even if the substrate is not heated, mechanical strain will be introduced during film formation, so 40
Heat treatment is performed at a temperature of 0° C. or higher. At this time, if the substrate and the thin film have different coefficients of thermal expansion, thermal stress will be introduced into the thin film during heating or cooling, leading to a decrease in magnetic permeability.

3) Due to the above-mentioned thermal contraction or thermal stress, cracks occur in the thin film and it loses its function as a soft magnetic thin film.

Despite the above-mentioned problems, a substrate material with a large coefficient of thermal expansion has not yet been obtained industrially.

Here, in order to obtain a Fe-8i-At alloy soft magnetic thin film with a low coefficient of thermal expansion, previously disclosed in Japanese Patent Application No. 60-179318,
It is disclosed that the total amount of Si and At may be limited to 3 to 10%. At this time, the thermal expansion coefficient is 150 to 14
1 x 10-7. /'C was obtained. However, if materials for soft magnetic thin films with even lower coefficients of thermal expansion can be realized, there will be fewer restrictions on substrate materials, and magnetic thin film elements,
In particular, it can greatly contribute to the practical application of thin-film magnetic heads.

Therefore, the present invention was made in view of these circumstances.
The main purpose is to have a small coefficient of thermal expansion, and also to have a low magnetic permeability.
The object of the present invention is to provide a soft magnetic thin film that has excellent corrosion resistance and mechanical strength, has good adhesion to a substrate, and has various properties of the thin film.

Means for Solving the Problems> The above purpose is to change the alloy composition of the soft magnetic thin film material to Si2-8
This is achieved by using 5% to 2.5% AtO, 0.5% to 6% Nb, 0.01% to 2% rare earth element, and the balance Fe.

In other words, the thermal expansion coefficient of the Fe-8t-Ata alloy is F
The coefficient of thermal expansion largely depends on the e content, and as the amount of Fe increases, the coefficient of thermal expansion decreases. In other words, as the amount of (Si+At) decreases, the coefficient of thermal expansion decreases (Japanese Patent Application No. 6O-17
9318). It has been found that when Nb is added to this, the coefficient of thermal expansion is further reduced. This - as an example Fe9
1J-xS17”i, 5CeO, 2 alloy with Nb
Figure 1 shows the change in the coefficient of thermal expansion when % is added.

(Here, Ce was selected as the rare earth element.) From Figure 1, it can be seen that the coefficient of thermal expansion decreases as the amount of Nb added increases, and for example, when 2% Nb is added, it decreases by 1X10/C. Moreover, even if more than 6 inches are added, the coefficient of thermal expansion hardly changes. On the other hand, 0.5
When the amount is less than 1, the change in the coefficient of thermal expansion is slight, and the effect of its addition is not clear. The main purpose of adding Nb is to reduce the coefficient of thermal expansion, but other effects include improvements in corrosion resistance, mechanical strength, and magnetic permeability.

Rare earth elements are added primarily to improve mechanical strength, but they also have the effect of improving corrosion resistance and magnetic permeability. If the amount added is less than 0.01 inch, the effect will not be clear, and even if it is added in excess of 2 inches, no dramatic improvement in mechanical strength will be observed.

The same applies to corrosion resistance and transmittance. Further, the addition of this rare earth element hardly contributes to a change in the coefficient of thermal expansion.

In the range of 2 to 8% Si and 0.5 to 2.5% At, the thermal tensile modulus largely depends on the amount of Si and has little relation to the amount of At. However, by adding At, it is possible to reduce the magnetic anisotropy and improve the magnetic permeability. That is, Si
The coefficient of thermal expansion is set by the amount of Nb and the amount of Nb, and the magnetic permeability can be improved by At and rare earth elements, which hardly contribute to the coefficient of thermal expansion. 2% for Si2~8ch
This is because if it is less than 8%, the magnetic permeability is low, and if it exceeds 8%, a material with a small thermal expansion coefficient and high magnetic permeability cannot be obtained even by adding At, Nb, or rare earth elements. On the other hand, At0.
5 to 2.5% is because if it is less than 0.5%, the effect of reducing magnetic anisotropy is small, and if it exceeds 2.5%, Si2
This is because the magnetic permeability is lowered in the range of ~8%.

Further, the method for producing the soft arsenic thin film of the present invention is not particularly specified, but can be arbitrarily selected from among the sun-sealing method, vapor deposition method, plating method, and the like. The addition amount of each element specified here is the alloy composition of the thin film, and the composition of the sputter target, vapor deposition master alloy, etc. for manufacturing this thin film may be determined depending on the manufacturing equipment and manufacturing conditions.

Hereinafter, the present invention will be described in detail with reference to 9 examples using the Sufu 4 Tsuta method.

<Example> A crystallized glass substrate (thermal expansion coefficient 140 x 10"-7, /'C) with an outer diameter of 10 mm and an inner diameter of G gate, and a thickness of 0.5 m was prepared using the SiR ivy method. An alloy having the composition shown in 1 was deposited to a thickness of 3 μm.In order to clarify the effect of adding Nb and rare earth elements, most of the alloys were coated with an S1 content of 7%,
The At content was kept constant at 1.5%. As a result of analyzing these Snock ivy films, in addition to the elements shown in Table 1, 3 ppm or less of S and 5 ppm or less of C were detected. In addition, no second phase precipitation was observed by microstructural observation and X-ray diffraction results of the sputtered film. After film formation, 4
Heat treatment is performed at a temperature of 00 to 800℃ depending on the film composition-1
The effective magnetic permeability (μe) at 5 MHz was measured. Note that heat treatment in a magnetic field or cooling in a magnetic field was performed as necessary.

The results are shown in Table-1.

The coefficient of thermal expansion shown in Table 1 was not measured directly on a thin film, but was measured using materials with the same composition as 3 x 3 x 15 (unit:
A sample of the throat) was cut out and measured.

In addition, 5cr was used for mechanical strength measurement and corrosion resistance testing.
A thin film with a thickness of 3 μm, which was prepared at the same time as described above, was used as a sample on a polyimide film substrate with r1 square dimensions. The salt water jet test method (JIS Z2371) was used for the corrosion resistance test. The evaluation method was to calculate the relative corrosion area by setting the corrosion area of sample number A2 as 100.

Mechanical strength was determined by performing a tensile test on the obtained film and taking the strength at which cracks occurred in the film.

The evaluation method was a relative evaluation with the strength of sample number 2 being 100. The results are shown in Table-1.

In this example, Si 2-8%, At 0.5-2.5%
, NbO, 5-6%, rare earth elements 0.01-2%, and the balance Fe, the soft magnetic alloy thin film has a small coefficient of thermal expansion, so it has excellent adhesion to the substrate, high magnetic permeability, and corrosion resistance. It can be seen that the material has excellent mechanical strength.

<Effects of the Invention> As described above, according to the soft magnetic thin film material according to the present invention, a thin film having excellent adhesion to a substrate and high magnetic permeability, corrosion resistance, and mechanical strength can be realized.

[Brief explanation of drawings]

FIG. 4 is a diagram showing the relationship between the amount of Nb added and the coefficient of thermal expansion.

Claims (1)

[Claims] 1) Weight ratio: Si2-8%, Al0.5-2.5%, N
A soft magnetic thin film material comprising 0.5 to 6% b, 0.01 to 2% rare earth element, and the balance Fe.