JPH0744108B2 - Soft magnetic thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a soft magnetic thin film having a high saturation magnetic flux density and a high frequency magnetic permeability, which is suitable for a core material of a magnetic head for high density recording / reproducing.

[Background of the Invention]

For example, in magnetic recording / reproducing devices such as audio tape recorders and VTRs (video tape recorders), higher recording density and higher quality of recording signals are being advanced. As magnetic powder Fe, Co,
Developed a so-called metal tape using powder made of a metal or alloy such as Ni, and a so-called vapor-deposition tape in which a ferromagnetic metal material is directly deposited on a base film by a vacuum thin film forming technology, and put into practical use in various fields. Has been done.

[Problems to be Solved by Prior Art and Invention]

By the way, in order to exert the characteristics of the magnetic recording medium having such a predetermined coercive force, in addition to having a high saturation magnetic flux density as the characteristics of the core material of the magnetic head,
When reproducing with the same magnetic head, it is required to have high magnetic permeability as well.

Conventionally, sendust alloys (Fe-Si-Al, Bs10KG) and Co
Although amorphous amorphous alloys have been used, sendust alloys have large internal stress in the film, and it is difficult to increase the film thickness because crystal grains grow easily. Moreover, the saturation magnetic flux density Bs is about 10 KG, which is insufficient for higher density recording. In addition, Co-based amorphous alloys with good characteristics can also be produced with high saturation magnetic flux density Bs, but since they crystallize at about 450 ° C, glass bonding cannot be performed at high temperature during head formation, and sufficient bonding strength is obtained. There was a difficulty that I could not do it.

Another soft magnetic material is iron nitride, which is generally formed into a thin film by ion beam deposition or sputtering with iron as a target in a nitrogen-containing atmosphere. Furthermore, this thin film was sometimes heat-treated if necessary. However, this soft magnetic thin film has a problem that the coercive force is significantly increased by heat treatment or heating, and the stability of the characteristics is insufficient.

Japanese Unexamined Patent Publication No. 63-299219 describes the following soft magnetic thin film, which is intended to improve such problems.

“Fe _x N _y A _z (where x, y, and z are composition ratios in atomic%
, A is Si, Al, Ta, B, Mg, Ca, Sr, Ba, Cr, Mn, Zr, Nb, T
Represents at least one of i, Mo, V, W, Hf, Ga, Ge, and rare earth elements. ), The composition range is 0.5 ≦ y ≦ 5.0 0.5 ≦ z ≦ 7.5 x + y + z = 100. However, the coercive force of the soft magnetic thin film described in JP-A-63-299219 is inevitably increased by heat treatment.

Furthermore, there is a drawback in that the magnetic permeability at high frequencies cannot be increased because it does not have uniaxial anisotropy.

In addition, depending on the film forming conditions, generally, crystalline materials are apt to become columnar crystals due to the self-shadowing effect during the process of depositing the film, and voids are formed at the grain boundary parts, so that they are magnetically inferior. It tends to be continuous and the soft magnetic characteristics tend to deteriorate. This self-shadowing effect becomes particularly noticeable when there is a step on the underlayer or when the film is thickened as in the case of manufacturing a magnetic head, and there is a drawback that sufficient characteristics cannot be obtained.

It is an object of the present invention to provide a soft magnetic thin film that solves the above problems of the prior art.

[Means for Solving the Problems]

According to the present invention, the above object can be achieved by the following soft magnetic thin film.

Fe _a B _b N _c (where a, b, and c are each atomic%, B is Z
It represents at least one of r, Hf, Ti, Nb, Ta, V, Mo and W. ), And the composition range is 0 <b ≦ 20 0 <c ≦ 22 (excluding b ≦ 7.5 and c ≦ 5). This composition range is defined as points E, F, G, H, I, J.
Is shown in FIG.

Preferably, the composition range is 69 ≦ a ≦ 93 2 ≦ b ≦ 15 5 <c ≦ 22. This composition range is first defined by points Q, K, L, U, M
Shown in the figure.

Preferably, Fe _a B _b N _c (where a, b and c each represent atomic% and B represents at least one of Zr, Hf, Ti, Nb, Ta, V, Mo and W). ), And its composition range is P (91,2,7) Q (93,2,5) R (88, in the three-component three-component composition coordinate system (Fe, B, N). 7,5) S (73,12,15) T (69,12,19) U (69,9,22) V (76,5,19) It is the range surrounded by the line segment connecting 7 points. This is a soft magnetic thin film. This composition range is defined by points P, Q, R, S, T, U, V.
Is shown in FIG.

The crystal grain size is preferably 300 Å or less.

[Preferable Embodiment and Action]

The soft magnetic thin film of the present invention comprises Fe and N, a specific additive element B,
That is, it consists of at least one element of Zr, Hf, Ti, Nb, Ta, V, Mo and W, and these three elements, Fe and N, and the specific additive element B (including two or more elements) are Within the specific composition range.

When the composition range is 0 <b ≦ 20 and 0 <c ≦ 22 (excluding b ≦ 7.5 and c ≦ 5), preferably,
b ≧ 0.5 and c ≧ 0.5. This is because in the case of b <0.5 or c <0.5, the effect due to their presence is often not exhibited.

If the additive element B exceeds 20 atom%, or N exceeds 22 atom%, good soft magnetism cannot be obtained.

The composition range is 69 ≦ a ≦ 93 and 2 ≦ b ≦ 15 and 5 <c
When ≦ 22 (more preferably 5.5 <c ≦ 22), better soft magnetism is exhibited.

Also, preferably, the composition is the specific points P, Q, R, S, T, U, in the three-component three-component composition coordinate system (Fe, B, N).
It is the area surrounded by the line segment connecting the seven points of V. Since the coercive force is small in this composition range, it is particularly suitable as a core material of a magnetic head. Most preferably, the composition range is a coercive force of 1.5 Oe or less (further, 1 Oe or less).

When the additional element B is Zr, the preferred composition range of the soft magnetic thin film is in the range represented by _{Fe d (Zr e N 1-} e) 100-d 77 ≦ d ≦ 88 0.3 ≦ e ≦ 0.38. This composition range is shown in FIG. 1 by points W, X, Y and Z. The coordinates of these points W, X, Y and Z are almost as follows.

W (88,3.6,8.4) X (88,4.56,7.44) Y (77,8.74,14.26) Z (77,6.9,16.1) That is, in this range, Fe is 77 to 88 atomic% and Zr Ratio c / b of the content rate b (atomic%) of N and the content rate c (atomic%) of N
Is about 1.63 to 2.33. The soft magnetic thin film in this composition range exhibits excellent soft magnetism (for example, coercive force Hc <5 Oe).

The additive element may be one kind or two or more kinds. For example, only Zr can be added, but a part of Zr (for example, 30 atom% of added Zr) can be replaced by other additive element.

Further, Fe can be replaced by one or more of Co, Ni or Ru. For example, 30 atomic% of Fe in the soft magnetic thin film
Can be replaced to a degree.

The soft magnetic thin film of the present invention is an amorphous thin film having the above-mentioned specific composition obtained by vapor deposition method such as RF sputtering, and the amorphous thin film is heat treated at 350 to 650 ° C. It can be manufactured by crystallizing a part or all of the thin film.
Preferably, a magnetic field may be applied during the heat treatment to induce uniaxial magnetic anisotropy to crystallize a part or all of the amorphous thin film.

When the soft magnetic thin film of the present invention is manufactured by the above method,
Since various characteristics of the soft magnetic thin film after production may differ depending on the type of substrate to be formed, it is preferable to appropriately select and produce the substrate.

Example 1 An alloy target having a composition of Fe _100-y Zr _y (y = 5.0, 10.0, 15.0 (at%)) was prepared, and each contained 2.5 to 12.5 mol% nitrogen and contained nitrogen. High-frequency sputtering was performed in an argon gas atmosphere with a gas pressure of 0.6 Pa and an input power of 200 W. The saturation magnetic flux density Bs and the coercive force Hc of each thin film thus obtained after heat treatment in a magnetic field were measured. Bs and Hc
AC BH tracer (applied magnetic field 50Hz, 25Oe,
When Hc> 25, 90 Oe) (same as below). As the substrate, a crystallized glass substrate (PEG3130C HOYA) and a single crystal sapphire substrate were used. The film thickness was about 0.6 μm in each case.

The results are shown in Table 1-A. Hc is shown as a value in the easy axis direction. For some soft magnetic thin films, 5MH
The magnetic permeability μ and the magnetostriction at z were measured. For magnetostriction, the sign of magnetostriction was judged from the change in BH characteristics when stress was applied to the film. The results are also shown in Table 1-A.

On the other hand, in FIG. 1-B, three kinds of heat-treated thin films (No. of Comparative Example 1) obtained on the crystallized glass substrate in the same manner as in Example 1 except that nitrogen was not contained in the atmosphere during sputtering. .
The measurement results of the composition of 1,2,3), the saturation magnetic flux density Bs, and the coercive force Hc are shown.

Further, FIG. 2 shows the relationship between the composition and coercive force Hc of the soft magnetic thin film manufactured by the method of the above-mentioned example and the positive / negative judgment of the magnetostriction (when heat-treated at 550 ° C. using a crystallized glass substrate).
Furthermore, the Fe content in the Fe-Zr alloy target and the N ₂ content in the sputter gas, the manufacturing conditions of the soft magnetic thin film, and the coercive force Hc
And the saturation magnetostriction λs (using a crystallized glass substrate
FIG. 3 shows the case of heat treatment at 0 ° C.).

X-Ray Diffraction and Electrical Resistivity The results of X-ray diffraction of the thin film which was not heat-treated (as depo) and the thin film which was heat-treated at 250, 350, 450 or 550 ° C. for the composition of Fe _80.9 Zr _6.5 N _{12.6 in} the above Examples are shown in FIG. Table 2 shows the measurement results of the electric resistivity. According to Figure 4, 550
It was found that the crystal grain size of the thin film annealed at ℃ was about 130Å from the half-width. It was found that the as depo thin film and the 250 ° C heat-treated thin film were amorphous, the 350 ° C and 450 ° C heat-treated thin film consisted of microcrystals, and the 550 ° C heat-treated thin film consisted of further grown microcrystals. These microcrystals are considered to contribute to the soft magnetism of the thin film, and the formation of such microcrystals is considered to be due to the presence of N and Zr. Second
According to the table, the resistivity of this thin film decreases with increasing heat treatment temperature, but even when the temperature is increased up to 550 ℃ and heat treatment is performed, its value is much higher than that of pure iron, permalloy, etc. -The values are almost the same as those of Si alloy and Sendust. Therefore, when used as the core of a magnetic head, eddy current loss is small and advantageous.

Vickers hardness Furthermore, the Vickers hardness was measured for a thin film having a composition of Fe _80.9 Zr _6.5 N _12.6 Hv = 1000 (kg / mm ² , weight 10 g)
The value of was obtained. This value is much higher than Sendust and Co-based amorphous alloys (Hv = 500 to 650), which have been used as magnetic head materials, and wear resistance can be sufficiently improved.

BH Curves BH curves of some thin films in the above examples by AC BH tracer are shown in FIG.

The sample shown in Fig. 5 is 10 Tor in a magnetic field of 1 kOe after film formation.
Heat-treated at 550 ° C for 60 minutes in rN ₂ atmosphere. As is clear from this figure, a clear in-plane uniaxial anisotropy is induced in the thin film by the heat treatment in the magnetic field. Therefore, by making the hard axis direction of this thin film the magnetic direction, the magnetic permeability at frequencies higher than 1 MHz can be made sufficiently high, which is also advantageous as a magnetic head material. Since this anisotropic magnetic field Hk changes from 3 to 18 Oe depending on the composition, the material can be selected depending on the target magnetic permeability and the frequency range to be used. For example, when it is desired to obtain a high magnetic permeability at 10 MHz or less, a composition with Hk = 3 to 5 Oe can be used, and a higher Hk composition can be used in order to prevent the magnetic permeability from deteriorating even at higher frequencies.

MH Curve FIG. 6 shows the result of the MH curve measured using VSM for the thin film of the composition of Fe _80.9 Zr _6.5 N _12.6 in Example 1 above. In the figure, (a) shows the MH curve for the thin film immediately after film formation (as depo), and (b) shows the MH curve for the thin film after heat treatment in a magnetic field at 550 ° C. (No demagnetizing field correction was performed. However, the sample shape was φ5 mm × t0.63 μm.) The coercive force measured using VSM was one digit or more smaller than the value obtained by the AC BH tracer, and (b ) About 50
I got mOe. This value is almost the same as that of Sendust and Co-based amorphous alloys, and it can be seen that the soft magnetic characteristics are excellent. Further, from (b), 4πMs = 14.5KG, which is sufficiently higher than that of Sendust or Co-based amorphous alloy, and is advantageous as a magnetic head material for recording on a high coercive force medium.

The 4πMs of the thin film before heat treatment is 13.0 KG, which is slightly lower than that after heat treatment. It also has a vertical anisotropy (Hk400Oe),
The Hc is also high and the soft magnetic characteristics are poor.

Corrosion _Resistance The thin film having the composition of Fe _80.9 Zr _6.5 N _12.6 in Example 1 was evaluated for corrosion resistance based on the change in the surface condition after immersion in tap water for about 1 week. As a result, the surface condition of this sample remained mirror-like and did not change at all. For comparison, similar experiments were conducted for Co _88.4 Nb _8.0 Zr _3.6 amorphous alloy film and Fe-Si alloy (magnetic steel sheet). As a result, the Co-Nb-Zr alloy did not change at all, but the Fe-Si alloy had rust on the entire surface. From the above, it was found that the alloy thin film of the present invention has excellent corrosion resistance.

(Example 2) Using an alloy target having a composition of Fe _92.5 Zr _7.5 , 2.5, 5.0, 7.
High-frequency sputtering was performed in a nitrogen-containing argon gas atmosphere containing nitrogen of 5, 10.0 or 12.5 mol% respectively, and Fe-Zr-N amorphous thin films of various compositions were formed on a sapphire substrate (R
Surface).

Amorphous thin film formed on the substrate at 350 ℃ or 550 ℃ 1
The Fe-Zr-N soft magnetic thin film of the present invention was obtained by heat treatment for a period of time. Table 3 shows the composition, the saturation magnetic flux density Bs, and the coercive force Hc of the obtained Fe-Zr-N soft magnetic thin film.

(Comparative Example 2) Table 3 also shows the composition, saturation magnetic flux density Bs, and coercive force Hc of the heat-treated thin film obtained in the same manner as in Example 2 except that the atmosphere during sputtering did not contain nitrogen.

(Example 3) Using a target having a composition of Fe ₉₀ Zr ₁₀ (at%), 6.0 mol%
High-frequency sputtering was carried out in a nitrogen-containing argon gas atmosphere containing nitrogen at a gas pressure of 0.6 Pa and an input power of 400 W, and was placed on a sapphire substrate (R surface, {102} surface).
Fe _75.9 Zr _7.3 N _{16.8 An} amorphous thin film was formed.

Amorphous thin film formed on the substrate, 250 ℃, 350 ℃, 450
℃, 500 ℃ or 550 ℃ 60 minutes, 120 minutes, 180 minutes, 240 minutes,
540 minutes, 1140 minutes, 2400 minutes or 4800 minutes Isothermal magnetic field (<0
Then, a soft magnetic thin film according to the present invention was obtained. BH characteristics (measurement magnetic field Hm = 25 (Oe)), coercive force Hc and anisotropic magnetic field of the obtained Fe-Zr-N soft magnetic thin film
Hk is shown in FIG.

Figure 8 shows the Fe-Z obtained for the heat treatment time t [min].
The relationship between (a) coercive force Hc and (b) anisotropic magnetic field Hk of the r-N soft magnetic thin film is shown respectively. FIG. 9 shows (a) the relationship between the heat treatment time t [min], the heat treatment temperature and the coercive force Hc, and (b) the relationship between the heat treatment time t [min], the heat treatment temperature and the anisotropic magnetic field Hk. Are shown respectively.

From these, the change in BH characteristics depending on the heat treatment temperature is 350 to 50.
It can be seen that there are three temperature ranges: 0 ° C, over 500 ° C, and under 350 ° C.

In addition, the Fe _75.9 Zr _7.3 N _16.8 amorphous thin film at 480 at 480
The composition (at%) of five kinds of soft magnetic thin films obtained by heat treatment at 0 min, 350 ° C. for 240 min, 450 ° C. for 180 min, 500 ° C. for 180 min, or 550 ° C. for 1140 min. Zr content (at
%) And Fe content (at%) ratio Zr / Fe, N content (at%)
To Zr content (at%) ratio N / Zr and BH characteristics (measurement magnetic field H
m = 25 (Oe)) is shown in Table 4. Each composition below is Fe
_91.2 (Zr · N _x ) _8.8 However, it can be expressed by x = N / Zr.

According to Table 4, the value of N / Zr is almost constant in the range up to heat treatment temperature 250 ℃ and in the range 350 ℃ ~ 500 ℃, the heat treatment temperature around 300 ℃ and around 500 ℃ It can be estimated that there is a heat treatment temperature at which the N / Zr value changes abruptly.

X-Ray Diffraction Patterns X-ray diffraction patterns of the Fe-Zr-N soft magnetic thin film obtained in Example 3 and the Fe _75.9 Zr _7.3 N _16.8 amorphous thin film (as depo) before heat treatment (source Cu Kα ray 40 kV , 30mA, λ = 1.5405Å)
Is shown in FIG. The X-ray diffraction pattern will be described below.

The thin film of as depo shows a typical halo pattern, which confirms that it is amorphized.

The position of the main peak shifts to the wide-angle side as the heat treatment temperature rises, and finally becomes 2θ = 44.6 ° by heat treatment at 550 ° C and αFe
Consistent with the (110) peak. 2θ at 250 ° C x 4800 minutes
= 43.7 °, which is consistent with the Fe ₃ Zr (440) peak. In the heat treatment from 350 ° C to 500 ° C, 2θ≈44 °,
This corresponds to a value approximately midway between the αFe (110) and Fe ₃ Zr (440) peaks.

The crystal grain size calculated from the half-width of the main peak by the Scherrer's equation is about 100Å from 250 ℃ to 450 ℃, and about 1 at 500 ℃ × 180 minutes.
Approx. 170 Å at 20Å, 550 ℃ x 1140 minutes (Approx. 13 at 550 ℃ x 60 minutes)
0 Å (see Example 1 and FIG. 4)) and temperature × time, and continuously increases.

The relationship between the 550 ° C heat treatment time, the position of the main peak, and the grain size is as follows.

From this, it can be seen that, although a fine αFe phase precipitates relatively quickly in the 550 ° C heat treatment, the crystal grains grow slightly with time.

In addition, at 550 ℃ heat treatment, new peaks of Fe ₃ Zr and ZrN were observed in addition to αFe, and it is considered that these peaks are finely precipitated.

(Example 4) Using a target having a composition of Fe ₉₀ Zr ₁₀ (at%), 5.0 mol%
In a nitrogen-containing argon gas atmosphere containing nitrogen, the high-frequency sputtering was performed under the conditions of a gas pressure of 0.6 Pa and an input power of 200 W to form a Fe-Zr-N amorphous thin film on the sapphire substrate (R surface).

The change in temperature of the magnetization of the amorphous thin film (about 0.6 μm thick) formed on the substrate (normalized by the magnetization at room temperature) is VS.
Measured by M. The results are shown in Fig. 11. The measurement is
Start from room temperature and raise the temperature at about 3 ° C / min, sample B at 340 ° C for 120 minutes, sample D at 450 ° C for 60 minutes, sample E at 500 ° C for 60 minutes, sample G at 520 ° C. 180 minutes, sample F
Was kept at 550 ° C for 120 minutes. Then this time, -3 ℃ / min
The temperature was lowered to room temperature at. From Fig. 11, the Curie temperature of the Fe-Zr-N amorphous thin film (as depo) before the heat treatment is about 250 ° C, and the magnetization value rises when the temperature is kept at 340 ° C or higher, and the Curie temperature increases. You can see that it will rise. It can be seen that, when kept at 550 ° C for 120 minutes, the Curie temperature rises above 700 ° C and approaches the Curie temperature of αFe (770 ° C) by heat treatment. Although the magnetization at room temperature is higher than that of the as depo amorphous thin film in all cases, it is almost saturated when kept at 520 to 550 ° C, which is 1.12 to 1.14 times that of the as depo amorphous thin film.

What is found from Example 3 and Example 4 will be described for each heat treatment temperature.

(A) Before heat treatment (as depo) Structurally amorphous. Soft magnetism is not obtained,
The Curie temperature is much lower than that of αFe, and the magnetic moment is lower than that after heat treatment. These are properties that can be considered as an Fe-based amorphous alloy. The N content is as high as 16.8% and N / Zr = 2.3.

(B) Heat treatment at 250 ° C BH characteristics were slightly improved as compared with as depo, and Hc was 5 to 7 Oe. Crystallization was confirmed by X-ray at 4800 minutes by increasing the heat treatment time, and the uniaxial anisotropic film (Hc = 1.4O
e) was obtained. The position of the main peak corresponds to the Fe ₃ Zr (440) peak. The N content after heat treatment is the same as as depo.

(C) Heat treatment at 350-500 ° C The main peak is located between the Fe ₃ Zr (400) and αFe (110) peaks, but a broad swelling is seen near ZrN (200), resulting in a complicated state. It is thought that In terms of BH characteristics, Hc 0.7 to 0.9 Oe, Hk = 9 to 12 Oe, heat treatment time ×
Hk tends to increase as the temperature increases. The Curie temperature changes continuously in this range, but the magnetization at room temperature is 1.06 to 1.08 times that before heat treatment, which is almost constant.
The N content after heat treatment is slightly lower at 500 ° C than before heat treatment, but it is in the N / Zr2 region.

(D) 550 ° C heat treatment The main peak clearly corresponds to the αFe (110) peak, and new peaks believed to be Fe ₃ Zr and ZrN also appear. From this, it was found that after heat treatment at 550 ° C, α oriented in (110)
Fine crystals of Fe (grain size 100-200Å) and finer Fe
₃ It is considered that Zr, ZrN, etc. are precipitated. However,
The Curie temperature is lower than the Curie temperature of αFe at 770 ℃, which is considered to be related to the fact that the crystal grains are fine.

Hc decreases with long-term heat treatment, reaches a minimum at about 400 minutes, and then increases slightly again. Hk decreases with time,
It becomes almost isotropic in 250 minutes.

The N content after heat treatment depends on the heat treatment time, and it decreases to N / Zr1.8 in the heat treatment for 60 minutes and N / Zr1.1 in the heat treatment for 1140 minutes. It is considered that a part of nitrogen is released outside the sample as N ₂ gas by the heat treatment at 550 ° C.

Thus, when the Fe-Zr-N amorphous thin film is heat-treated, the structure and properties of the soft magnetic thin film obtained differ depending on the heat-treatment temperature. This means that the second electric resistance of Example 1
Corresponds to the table.

The above contents are schematically shown in FIG.

(Example 5) Fe _76.2 Zr _7.3 N _16.5 was obtained by high frequency sputtering using an alloy target having a composition of Fe ₉₀ Zr ₁₀ in a nitrogen-containing argon gas atmosphere containing 6.0 mol% of nitrogen.
Amorphous thin films of two compositions of Fe _75.9 Zr _7.3 N _16.8 were respectively formed on the sapphire substrate (R surface). However, the former is φ6
The total pressure is 0.15Pa and the input power is 1kW using an inch target. The latter is a φ4 inch target and the total pressure is 0.6Pa and the input power is 40kW.
Sputtered at 0W.

5 Fe _76.2 Zr _7.3 N _16.5 amorphous thin film formed on the substrate
After heat treatment in a magnetic field at 50 ° C. for 60 minutes, a Fe _77.8 Zr _7.6 N _14.6 soft magnetic thin film (thickness: about 1 μm) was obtained. Further, the Fe _75.9 Zr _7.3 N _16.8 amorphous thin film formed on the substrate was heat-treated at 550 ° C. in a magnetic field to obtain a soft magnetic thin film of the present invention. The composition of the soft magnetic thin film is Fe _79.2 Zr _7.5 N when the heat treatment time is 60 minutes.
_{It was 13.3} and was Fe _83.2 Zr _8.0 N _8.8 after 1140 minutes. Table 5 shows the composition, the saturation magnetic flux density Bs, the coercive force Hc, and the anisotropic magnetic field Hk of these obtained soft magnetic thin films.

Example 6 Using an alloy target having a composition of Fe _100−y Hf _y (y = 5.0,10.0,15.0 (at%)), nitrogen containing 2,4,6,8,10 or 12 mol% of nitrogen was used. Fe-Hf-N amorphous thin films having various compositions were formed on the sapphire substrate (R surface) by high-frequency sputtering in an atmosphere of contained argon gas.

Amorphous thin film formed on the substrate 350 ℃ or 550 ℃, 1.1
After heat treatment in a magnetic field of kOe for 1 hour, an Fe—Hf—N soft magnetic thin film (film thickness: about 1 μm) within the composition range specified in the present invention was obtained. Table 6 shows the composition, the saturation magnetic flux density Bs, and the coercive force Hc of the obtained Fe-Hf-N soft magnetic thin film.

(Comparative Example 3) Table 6 also shows the composition, saturation magnetic flux density Bs, and coercive force Hc of three kinds of heat-treated thin films obtained in the same manner as in Example 6 except that the atmosphere during sputtering did not contain nitrogen.

Example 7 Using an alloy target having a composition of Fe _100−y Ta _y (y = 5.0,10.0,15.0 (at%)), nitrogen containing 2,4,6,8,10 or 12 mol% of nitrogen was used. Fe-Ta-N amorphous thin films having various compositions were formed on the sapphire substrate (R surface) by high-frequency sputtering in an atmosphere of contained argon gas.

Amorphous thin film formed on the substrate 350 ℃ or 550 ℃, 1.1
By heat-treating for 1 hour in a magnetic field of kOe, an Fe-Ta-N soft magnetic thin film (film thickness: about 1 μm) within the composition range specified in the present invention was obtained. Table 7 shows the composition, the saturation magnetic flux density Bs, and the coercive force Hc of the obtained Fe-Ta-N soft magnetic thin film.

(Comparative Example 4) Table 7 also shows the composition, saturation magnetic flux density Bs, and coercive force Hc of the heat-treated thin film obtained in the same manner as in Example 7 except that the atmosphere during sputtering did not contain nitrogen.

Example 8 Using an alloy target having a composition of Fe _100−y Nb _y (y = 5.0,10.0,15.0 (at%)), nitrogen containing argon containing 2, 4, 6, 8 or 10 mol% nitrogen was used. Fe-Nb-N amorphous thin films having various compositions were formed on a sapphire substrate (R surface) by performing high frequency sputtering in a gas atmosphere.

Amorphous thin film formed on the substrate 350 ℃ or 550 ℃, 1.1
By heat-treating for 1 hour in a magnetic field of kOe, an Fe—Nb—N soft magnetic thin film (film thickness: about 1 μm) within the composition range specified in the present invention was obtained. Table 8 shows the composition, the saturation magnetic flux density Bs, and the coercive force Hc of the obtained Fe-Nb-N soft magnetic thin film.

(Comparative Example 5) Table 8 also shows the composition, saturation magnetic flux density Bs, and coercive force Hc of the heat-treated thin film obtained in the same manner as in Example 8 except that the atmosphere during sputtering did not contain nitrogen.

Example 9 Using a target having a composition of Fe ₉₀ Zr ₁₀ (at%), 6.0 mol%
Fe-Zr-N amorphous thin film was formed on the substrate by high frequency sputtering in a nitrogen-containing argon gas atmosphere containing nitrogen. As the substrate, using the SiO ₂ film coated ferrite substrate formed by film formation of the SiO ₂ film on the ferrite substrate. The amorphous thin film was formed on the surface of the SiO ₂ film.

The amorphous thin film formed on the substrate was heat-treated in a magnetic field (magnetic field strength 1.1 kOe) at 550 ° C. for 1 hour to obtain a soft magnetic thin film (film thickness 5.9 μm) having uniaxial magnetic anisotropy. The composition of the obtained soft magnetic thin film was estimated to be Fe _77.8 Zr _7.6 N _14.6 from the composition of the soft magnetic thin film obtained under the same conditions except that a sapphire substrate was used instead of the above substrate.

The electrical resistivity ρ of the obtained thin film was 77 μΩ · cm, and the Vickers hardness Hv was 1010 kg / mm ² . The frequency characteristics of permeability of the obtained soft magnetic thin film are shown in Fig. 13-A, and B-
The H curve is shown in Figure 13-B.

Example 10 Using a target having a composition of Fe ₉₀ Hf ₁₀ (at%), 4.0 mol%
The Fe-Hf-N amorphous thin film was formed on the substrate by high-frequency sputtering in a nitrogen-containing argon gas atmosphere containing nitrogen. As the substrate, using the SiO ₂ film coated ferrite substrate formed by film formation of the SiO ₂ film on the ferrite substrate. The amorphous thin film was formed on the surface of the SiO ₂ film.

The thickness of the amorphous thin film formed on the substrate was 4.7 μm. This was heat-treated in a magnetic field of 1.1 [kOe] at 550 ° C for 1 hour to obtain a soft magnetic thin film. Then, after measuring the magnetic permeability and anisotropic magnetic field Hk of this thin film, an additional heat treatment was performed for 2 hours under the same conditions as above except for the time (heat treatment for a total of 3 hours). Here, the magnetic permeability and the anisotropic magnetic field were measured, and the additional heat treatment was performed for 3 hours (heat treatment for a total of 6 hours) under the same conditions as described above except for the time to determine the magnetic permeability and the anisotropic magnetic field Hk. It was measured. The compositions of the three kinds of soft magnetic thin films obtained were respectively Fe _77.4 Hf _7.5 from the compositions of the soft magnetic thin films obtained under the same conditions except that a sapphire substrate was used instead of the above substrate and the film thickness was 1 μm. It was estimated to be N _15.1 (1 hour heat treatment) and Fe _82.6 Hf _7.7 N _9.7 (6 hour heat treatment).

The electrical resistivity ρ of the obtained soft magnetic thin film (heat treatment for 6 hours) is
It was 60 μΩ · cm and Vickers hardness Hv was 1100 kg / mm ² . The frequency characteristic of magnetic permeability of the obtained soft magnetic thin film is shown in FIG. 14-A, and the BH curve is shown in FIG. 14-B.

In addition, the magnetic permeability (at 1MHz) μ _{1MHz of} the above three heat treatment steps
And the anisotropic magnetic field Hk is shown in FIG. 14-C. Figure 14-C shows F
It shows changes in the magnetic permeability μ _{1 MHz} and the anisotropic magnetic field Hk with respect to the heat treatment time of the e-Hf-N thin film.

Example 11 Using a target having a composition of Fe ₈₅ Ta ₁₅ (at%), 6.0 mol%
Fe-Ta-N amorphous thin film was formed on the substrate by high frequency sputtering in a nitrogen-containing argon gas atmosphere containing nitrogen. As the substrate, using the SiO ₂ film coated ferrite substrate formed by film formation of the ferrite substrate on the SiO ₂ film. The amorphous thin film was formed on the surface of the SiO ₂ film.

The amorphous thin film formed on the substrate was heat-treated in a magnetic field (magnetic field strength 1.1 kOe) at 550 ° C. for 1 hour to obtain a soft magnetic thin film (film thickness 5.6 μm) having uniaxial magnetic anisotropy. The composition of the obtained soft magnetic thin film was estimated to be Fe _69.8 Ta _11.5 N _18.7 from the composition of the soft magnetic thin film obtained under the same conditions except that a sapphire substrate was used instead of the above substrate.

The electrical resistivity ρ of the obtained soft magnetic thin film was 86 μΩ · cm, and the Vickers hardness Hv was 1220 kg / mm ² . The frequency characteristic of magnetic permeability of the obtained soft magnetic thin film is shown in FIG. 15-A, and the BH curve is shown in FIG. 15-B.

〔The invention's effect〕

As is apparent from the above description, the soft magnetic thin film of the present invention has a much higher saturation magnetic flux density than sendust alloys and amorphous soft magnetic alloys, can have zero magnetostriction, and has low retention. It is possible to obtain excellent soft magnetic characteristics such as magnetic force and high magnetic permeability.

Moreover, the electrical resistivity is as high as Sendust, and uniaxial anisotropy can be given by heat treatment in a magnetic field, and its size can be controlled by the composition and heat treatment time.
It is possible to obtain high frequency magnetic permeability according to the purpose. further
Since the characteristics do not deteriorate even by heat treatment up to 650 ° C, it has excellent heat resistance against glass bonding, etc., and also has high hardness and corrosion resistance, which makes it a highly wear-resistant and highly reliable material. ing.

Since the soft magnetic thin film of the present invention can be formed as an amorphous alloy at the time of film formation and can be microcrystallized later by heat treatment, it has good step coverage and is easy to obtain a mirror surface when forming a film, and thus can be formed into a multilayer film. Since it is possible to prevent the crystal grains from becoming coarse without resorting to any means, it is possible to increase the film thickness.

Therefore, by using the soft magnetic thin film of the present invention as a core material of a magnetic head, for example, it is possible to deal with a magnetic recording medium having a high coercive force, and it is possible to achieve high quality, high bandwidth, and high recording density. .

[Brief description of drawings]

FIG. 1 is a diagram showing the composition range of the soft magnetic thin film of the present invention. FIG. 2 is a diagram showing the relationship between the composition and the coercive force Hc of the soft magnetic thin film manufactured in the example, and the positive / negative judgment of magnetostriction. FIG. 3 is a diagram showing the relationship between the coercive force Hc and the saturation magnetostriction λs of the soft magnetic thin film manufacturing conditions and the soft magnetic thin film manufactured thereby. FIG. 4 is a diagram showing the X-ray diffraction measurement results of thin films having different heat treatment conditions. FIG. 5 is a diagram showing AC BH curves of thin films having different compositions. FIG. 6 is a diagram showing IH curves of the thin film before and after the heat treatment, which are obtained from VSM. FIG. 7 is a diagram showing BH characteristics, coercive force Hc, and anisotropic magnetic field Hk of the Fe-Zr-N soft magnetic thin film. FIG. 8 is a diagram showing the relationship between the coercive force Hc and the anisotropic magnetic field Hk of the Fe—Zr—N soft magnetic thin film obtained with respect to the heat treatment time t. 9 (a) and 9 (b) show heat treatment time t, heat treatment temperature and coercive force.
It is a figure which shows the relationship with Hc, the heat processing time t, the heat processing temperature, and the relationship of an anisotropic magnetic field Hk, respectively. Figure 10 shows Fe-Zr-
It is a figure which shows the X-ray-diffraction pattern of N soft magnetic thin film and the amorphous thin film before heat processing. FIG. 11 is a diagram showing the temperature change of the magnetization of the Fe—Zr—N soft magnetic thin film. FIG. 12 is a diagram showing the estimation of the characteristics of the soft magnetic thin film obtained by the heat treatment time t and the heat treatment temperature. Figures 13-A, 14-A and 15
FIG. 6A is a diagram showing frequency characteristics of magnetic permeability of the soft magnetic thin film of one embodiment of the present invention. 13-B, 14-B
FIG. 15 and FIG. 15-B are diagrams respectively showing AC BH curves in the easy axis direction (upper stage) and the hard axis direction (lower stage) of the soft magnetic thin film of one embodiment of the present invention, where B is an arbitrary unit. is there. 14th-C
The figure shows the Fe-Hf-N amorphous thin film with respect to the heat treatment time.
FIG. 3 is a diagram showing changes in magnetic permeability μ _{1 MHz} and anisotropic magnetic field Hk of an fN soft magnetic thin film.

Claims (4)

[Claims] 1. Fe _a B _b N _c (where a, b and c each represent atomic% and B represents at least one of Zr, Hf, Ti, Nb, Ta, V, Mo and W) .), And the composition range is 0 <b ≦ 20 0 <c ≦ 22 (excluding b ≦ 7.5 and c ≦ 5). 2. The soft magnetic thin film according to claim 1, wherein the composition range is 69 ≦ a ≦ 93 2 ≦ b ≦ 155 5 <c ≦ 22. 3. Fe _a B _b N _c (where a, b and c each represent atomic% and B represents at least one of Zr, Hf, Ti, Nb, Ta, V, Mo and W) .) And the composition range is P (91,2,7) Q (93,2,5) R (88) in the three-component three-component composition coordinate system (Fe, B, N). , 7,5) S (73,12,15) T (69,12,19) U (69,9,22) V (76,5,19) In the area surrounded by the line segment connecting 7 points A soft magnetic thin film characterized by being present. 4. The soft magnetic thin film according to claim 1, wherein the crystal grain size is 300 Å or less.