JP3214716B2 - Magnetic head and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-in-gap type magnetic head having a soft magnetic thin film having a higher saturation magnetic flux density than a core in a gap portion, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the progress of the information-oriented society, there has been a strong demand for a magnetic recording device having a large capacity, and it has become an important issue for magnetic recording technology to further increase the recording density. To cope with this problem, the medium has a high coercive force (Hc).
Technologies such as noise reduction and noise reduction have been developed.

[0003] On the other hand, in the past, magnetic heads using a ferrite as a magnetic core have been mainly used.
A so-called MIG (metal-in-gap) type magnetic head has appeared, in which a soft magnetic thin film of a metal such as sendust or a Co-based amorphous material is formed in a gap of a ferrite magnetic head. Ferrite has a saturation magnetic flux density (Bs) of about 500
Since it is about 0 G, the limit of Hc of the medium recordable by the conventional ferrite head is about 800 to 900 Oe. Therefore, it is necessary to increase the recording performance of the magnetic head in accordance with the increase of the Hc of the medium.
s A MIG type magnetic head formed with a soft magnetic thin film made of metal was developed and put into practical use.

Since the MIG type magnetic head can apply a strong magnetic flux to the medium from the soft magnetic thin film formed in the gap, it can also record on a high Hc medium. For example, a soft magnetic thin film having a Bs of about 10 kG can be used. When used as
It is now possible to record on a medium whose c is up to about 1300 Oe. When a super sendust having a Bs of about 15 kG or a Fe-Me (Me is Zr, Mo, Ta, etc.)-N thin film was used, recording was possible on a medium having an Hc of about 1600 Oe.

However, in the MIG type magnetic head, the boundary between the core and the soft magnetic thin film becomes a pseudo gap, and a false signal called a sub-pulse may be generated. The cause of the pseudo gap effect is, for example, that the interface between the ferrite core and the soft magnetic thin film is deteriorated by oxidation or reduction of a metal or an oxide, or that a characteristic component in the soft magnetic thin film (for example, Al in a sendust film). , Si) are diffused to the interface to form a non-magnetic layer, or to an initial deterioration layer generated at the time of forming a soft magnetic thin film.

In digital recording, a so-called bit shift occurs due to the presence of a sub-pulse, and a waveform shifts in the time axis direction, so that it is impossible to shorten the recording wavelength. In analog recording, the presence of sub-pulses
A periodic undulation occurs in the frequency characteristic curve.

[0007] In order to reduce such a pseudo gap effect, a Ni—
Attempts have been made to provide an Fe (permalloy) thin film as a base film. However, when a Ni—Fe thin film is subjected to a heat treatment at 600 ° C. or more, Ni diffuses into sendust and the magnetic permeability is significantly reduced (Journal of the Japan Society of Applied Magnetics 13,277-2).
80 (1989)). For this reason, when using a Ni—Fe underlayer, glass whose welding temperature is 600 ° C. or higher cannot be used.

In order to obtain a so-called low-melting glass having a welding temperature of less than 600 ° C., it is necessary to add a large amount of lead, an alkali metal, etc., so that environmental resistance such as moisture resistance becomes insufficient, and mechanical The target strength also decreases. Therefore, conventionally,
Glass used as a deposition glass has low environmental resistance and poor mechanical strength. For this reason, it has not been possible to realize both the reduction in the pseudo gap effect and the improvement in reliability and manufacturing yield.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a MIG type magnetic head having a low pseudo gap effect, high reliability and a high production yield, and a method of manufacturing the same. With the goal.

[0010]

This and other objects are achieved by the present invention which is defined below as (1) to (6). (1) A magnetic head having a pair of cores each made of ferrite, and a soft magnetic thin film having a higher saturation magnetic flux density than the core between at least one of the cores and the gap. Is lower in the vicinity of the core than in the vicinity of the gap, and the soft magnetic thin film is composed of at least two thin films having different saturation magnetic flux densities. A core-side thin film having a composition of Si: 5 to 12% by weight, the balance: Fe; and a composition of Al: 3 to 7% by weight, Si: 3 to 8% by weight, Ni: 1 to 5% by weight, and the balance: Fe. A magnetic head comprising: a gap-side thin film having: (2) Cr, M between the soft magnetic thin film and the core.
The magnetic head according to the above (1), which has a base film composed of at least one of o, Ta, Ti, W, V and Nb. (3) The magnetic head according to the above (1) or (2), wherein the pair of cores is welded and integrated by welding glass having a working temperature Tw of 300 to 850 ° C. (4) A method of manufacturing a magnetic head having a pair of cores each composed of ferrite and having a soft magnetic thin film having a higher saturation magnetic flux density than at least one core and a gap between at least one core and a gap, The magnetic flux density is lower in the vicinity of the core than in the vicinity of the gap, and is composed of at least two layers of thin films having different saturation magnetic flux densities: Al: 3 to 7% by weight; Si: 5 to 12% by weight; Forming a soft magnetic thin film having a core side thin film having a composition and a gap side thin film having a composition of Al: 3 to 7% by weight, Si: 3 to 8% by weight, Ni: 1 to 5% by weight, and balance: Fe And a method for manufacturing a magnetic head, wherein the soft magnetic thin film is subjected to a heat treatment. (5) Cr, M between the soft magnetic thin film and the core.
5. The method of manufacturing a magnetic head according to claim 4, wherein a base film made of at least one of o, Ta, Ti, W, V and Nb is formed. (6) The method of manufacturing a magnetic head according to (4) or (5), wherein the pair of cores is welded and integrated by welding glass having a working temperature Tw of 300 to 850 ° C., and heat treatment is performed by heating at this time.

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

The magnetic head of the present invention is a MIG type magnetic head having a soft magnetic thin film having a higher Bs than the core between the core and the gap. In the present invention, Bs near the core of the soft magnetic thin film is configured to be smaller than Bs near the gap.
Thus, B at the boundary between the ferrite core and the soft magnetic thin film
By reducing the step of s, the pseudo gap effect can be significantly reduced. Since the soft magnetic thin film in the vicinity of the gap has the same Bs as the conventional one, the high write performance does not change.

Further, the soft magnetic thin film includes a core-side thin film of a sendust-based alloy containing Fe, Al and Si as main components, and a gap-side thin film of a super sendust-based alloy containing Fe, Al, Si and Ni as main components. Therefore, the heat resistance is high, and the magnetic properties are not deteriorated even when heat treatment is performed at a temperature of 600 ° C. or more during glass welding.
Therefore, a high-strength fused glass having good environmental resistance can be used, and a magnetic head with high reliability and high production yield can be realized.

Further, the provision of the underlayer improves the adhesion between the soft magnetic thin film and the core. In particular, when the base film is made of Cr, the pseudo gap effect can be further reduced.

Japanese Patent Application Laid-Open No. 61-34707 describes a MIG type magnetic head using a ferrite core. The gap portion of the magnetic head forms a magnetic circuit by connecting a polycrystalline magnetic alloy, an amorphous magnetic alloy, and a ferrite core in this order. The polycrystalline magnetic alloy, the amorphous magnetic alloy, and the ferrite are arranged in this order. , The saturation magnetic flux density is low. However, since this magnetic head uses an amorphous magnetic alloy, it has low heat resistance and cannot use glass having a high welding temperature.

[0022]

The specific structure of the present invention will be described below in detail with reference to the accompanying drawings. The magnetic head of the reference example shown in FIG. 1 and the magnetic head of the present invention shown in FIG. 2 have a pair of cores of a first core 1 and a second core 2,
The two cores are integrated by a welding glass 3 via a gap 5, and a soft magnetic thin film 4 having a larger Bs than each core is provided between the second core 2 and the gap 5. Usually,
A winding is wound around the first core 1.

The soft magnetic thin film 4 has a composition mainly composed of Fe, Al and Si, and is configured such that Bs is smaller near the second core 2 than near the gap 5.
In order for Bs to have such a distribution, Bs of the soft magnetic thin film 4 is gradually reduced from the side in contact with the gap 5 to the side in contact with the second core 2 as in the reference example of FIG. Although it is conceivable to form the soft magnetic thin film 4 in the present invention, as shown in FIG. 2, at least two thin films having different Bs are used.

The magnetic head of the reference example shown in FIG.
The soft magnetic thin film 4 has a configuration in which s gradually decreases. The soft magnetic thin film 4 having such a Bs distribution can be formed by continuously changing the content ratio of the constituent elements. In this case, the overall composition of the soft magnetic thin film 4 is preferably 3 to 7% by weight of Al, 5 to 12% by weight of Si, and the balance of Fe. By providing a composition distribution such that the content ratio of Si and Al gradually decreases from the second core 2 side to the gap 5 side, Bs can be gradually reduced from the gap 5 side to the second core 2 side. . Specifically, the content ratio of Al and Si in the vicinity of the second core 2 is preferably about 7 to 9% by weight of Al and about 10 to 15% by weight of Si.
It is preferable that the content ratio of 1 and Si is about 1 to 4% by weight of Al and about 3 to 8% by weight of Si.

By appropriately selecting the composition from such a range, 8000 to 1100 in the vicinity of the second core 2
0G, 12000-150 near gap 5
Bs of about 00G can be obtained.

The magnetic head of the present invention shown in FIG.
It has a soft magnetic thin film 4 composed of two thin films having different s. The soft magnetic thin film 4 includes a core-side thin film 41 on the second core 2 side.
And the gap side thin film 42 on the gap 5 side. The core side thin film 41 has a lower Bs than the gap side thin film 42. In this configuration, the core-side thin film and the gap-side thin film may each be made of a sendust-based alloy, and the composition of each thin film may be the composition near the core and the composition near the gap of the above-described composition continuously variable film. In this example, the core-side thin film has a Sendust alloy-based composition, and the gap-side thin film has a Super Sendust alloy-based composition. Specifically, the composition of the core-side thin film is Al: 3 to 7% by weight, Si: 5 to 12% by weight, and the balance: Fe. The composition of the gap-side thin film is: Al: 3 to 7% by weight, Si: 3 -8% by weight, Ni: 1-5% by weight, balance: Fe. By appropriately selecting the composition of each thin film from such a range, the core side thin film has a thickness of 8000 to 11000 G
In the gap side thin film, Bs of about 12000 to 15000 G can be obtained.

When the soft magnetic thin film 4 is composed of a plurality of thin films having different Bs, the thin film closest to the core is defined as the core-side thin film, and the thin film closest to the gap is defined as the gap-side thin film. It is preferable that Bs of the thin film existing between the two thin films is higher than the core-side thin film and lower than the gap-side thin film.

The Bs of the ferrite core is 3000
~ 6000G.

The soft magnetic thin film 4 is made of Cr, Mo, Ti, Ta, W, Zr, Hf, in addition to Fe, Si, Al and Ni.
Ga, Ru, Au, Ag, Co, Zn, Sn and the like may be contained at 1 atomic% or less of the whole.
It is preferable that Au is contained because the soft magnetic property is improved.

The thickness of the soft magnetic thin film 4 is preferably 0.2
10 to 10 μm, more preferably 0.5 to 5 μm. If the film thickness is less than the above range, the volume is insufficient and the film is easily saturated, and the function of applying a strong magnetic field becomes insufficient. On the other hand, if the thickness exceeds the above range, particularly in the case of a single-layer film, the eddy current loss increases and the high-frequency characteristics become insufficient. As shown in FIG. 2, when the soft magnetic thin film 4 is composed of a plurality of thin films, the thickness ratio of each thin film is not particularly limited, but usually the thickest thin film is three times or less the thinnest thin film, particularly It is preferable to make it 1.5 times or less.

In the present invention, it is preferable to provide an underlayer 6 between the soft magnetic thin film 4 and the second core 2. Base film 6
Is preferably composed of at least one of Cr, Mo, Ta, Ti, W, V and Nb. Of these, Cr is particularly preferred. By configuring the base film 6 with Cr, the pseudo gap effect can be further reduced. The base film 6 may be made of an alloy containing the above elements, for example, a Cr-Si alloy or the like.

The thickness of the base film 6 is usually 0.001 to
The thickness is preferably 0.1 μm, particularly preferably 0.002 to 0.05 μm. If the thickness is less than the above range, the effect as a base film is insufficient, and if it exceeds the range, the volume of the soft magnetic thin film cannot be sufficiently increased.

Although the soft magnetic thin film 4 is provided between the second core 2 and the gap 5 in the illustrated example, it may be provided between the first core 1 and the gap 5. If necessary, both cores may be provided with a soft magnetic thin film. In that case, it is preferable that the base film is also provided on both cores.

In the present invention, each core is made of ferrite. The ferrite used is not particularly limited.
It is preferable to select n-Zn ferrite or Ni-Zn ferrite according to the purpose. The Mn-Zn ferrite, Fe ₂ O ₃ 50 to 60 mol%, ZnO
About 8 to 25 mol%, the balance being substantially MnO is preferred. Further, Ni-Zn ferrite is exhibits excellent characteristics particularly in a high frequency region, as the preferred composition, Fe ₂ O ₃ is 30 to 60 mol%, NiO is 1
It is about 5 to 50 mol% and ZnO is about 5 to 40 mol%.

Bs at the direct current of each core is preferably 30
00 to 6000G. When Bs is less than the above range, overwrite characteristics are deteriorated, and such Bs
In the case of the composition described above, the Curie temperature is lowered, so that the thermal stability is lowered. If the ratio exceeds the above range, the magnetostriction increases and the characteristics as a magnetic head deteriorate, or the magnetic head is easily magnetized.

The initial magnetic permeability μ _i of each core at DC is 1,00
It is preferable that Hc is 0 or more and 0.3 Oe or less.

It is preferable that the gap opposing surface of each core be smoothed by mirror polishing or the like so that the soft magnetic thin film 4 and the base film 6 can be easily formed.

The gap 5 is made of a non-magnetic material. Adhesive glass is preferably used for the gap 5 in order to increase the adhesive strength.
Glass shown in No. 6 or the like is preferable. Further, the gap 5 may be composed of only the adhesive glass, but is preferably composed of two layers of the gap 51 and the gap 53 as shown in the figure in order to increase the gap formation speed and the gap strength. In this case, it is preferable to use SiO ₂ for the gap 51 and use an adhesive glass for the gap 53. In the case of a magnetic head of a type in which the welding glass 3 flows into both sides of the gap, the gap 5 may be made of only silicon oxide. The method of forming the gap 5 is not particularly limited, but it is preferable to use a sputtering method. The gap length is usually about 0.2 to 2.0 μm.

The magnetic head of the present invention is usually manufactured as follows. The soft magnetic thin film 4 and the base film 6 are preferably formed by a vapor phase film forming method such as sputtering or vapor deposition, but may be formed by liquid phase plating. In the case of the configuration of the reference example in which the composition continuously changes from the core side to the gap side, it is preferable to use an evaporation method. In this case, due to the difference in vapor pressure, Al and Si are likely to evaporate at first, and a low Bs film having a high ratio of these is formed. Then, the evaporation amounts of Al and Si gradually decrease, and the film changes to a high Bs film having a high ratio of Fe. By appropriately selecting the amounts of Al and Si and the heating power, an arbitrary Bs and its change pattern can be realized.

The bonding of the cores is usually carried out by thermocompression bonding with the adhesive glass in the gap 53 and at the same time pouring in the welding glass 3. Working temperature T of welding glass 3 to be used
It is preferable that w is 300 to 850 ° C., particularly about 600 to 700 ° C. In this case, the holding temperature at the time of glass welding is 300 to 850 ° C., particularly about 600 to 700 ° C. The working temperature Tw is a temperature at which the viscosity of the glass becomes 10 ⁴ poise, as is well known.

In the case of a composite floating magnetic head, the magnetic head having the structure shown in FIG. 1 (reference example) or FIG. 2 (example of the present invention) is formed by a glass with a slider in a secondary welding step. Glue.

In the magnetic head of the present invention, since the soft magnetic thin film 4 has good heat resistance, Hc of the soft magnetic thin film 4 does not increase even when welding is performed using such a glass of Tw, and the soft magnetic thin film 4 has good softness. Magnetism is maintained. For this reason, it is possible to use a deposition glass having a low content of lead, an alkali metal, or the like, thereby realizing a magnetic head having good environmental resistance and high mechanical strength.

The soft magnetic thin film is preferably subjected to a heat treatment in order to improve the soft magnetic characteristics. However, since the above-mentioned heating at the time of welding can be used as the heat treatment, the number of steps can be reduced.

The magnetic head of the present invention may be of a tunnel erase type such as a so-called laminate type or a bulk type, a floppy head for performing overwrite recording such as a read / write type having no erase head, a floating type of a monolithic type or a composite type. It is used as various magnetic heads such as a computer head, a rotary VTR head and an R-DAT head.

It should be noted that the present invention relates to a MIG type magnetic head 1
It is applicable to a so-called enhanced dual gap length (EDG) type magnetic head. In this case, a soft magnetic thin film having a lower Bs than the core is provided on the core facing the soft magnetic thin film with a gap therebetween. That is, in the configuration of the reference example shown in FIG. 1, a soft magnetic thin film having a lower Bs than the ferrite constituting the core is provided between the first core 1 and the gap 5.

[0046]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

A magnetic head sample having the structure shown in FIG. 1 was manufactured. The composition of the soft magnetic thin film of each magnetic head sample is shown in Table 1 below.

The soft magnetic thin film 4 is formed by a sputtering method.
The thickness was 2 μm. However, in Sample No. 5 (Reference Example), a film was formed by a vapor deposition method, and a composition in which the composition was continuously changed utilizing the difference in vapor pressure of the element to be vapor deposited was used.

The underlayer 6 is a Cr film having a thickness of 0.01 μm and is formed by a sputtering method.

The material of each core is Mn-Zn ferrite (B
_s = 5 kG, μ _i = 3000, Hc = 8 A / m).

The gap 51 is formed by sputtering using SiO ₂ and has a thickness of 0.3 μm. Adhesive glass with a working temperature Tw of 800 ° C. was used for the gap 53. The gap 53 was formed by a sputtering method, and the thickness was set to 0.1 μm.

The composition of the welding glass 3 is as follows: SiO ₂ : 27.0, B ₂ O ₃ : 2.0, PbO: 59.0, Al ₂ O ₃ : 2.0, ZnO: 4.0, by weight ratio. Na ₂ O: 6.0, and the working temperature Tw was 690 ° C. And 7
Welding was performed at 00 ° C. for 1 hour. Then, each magnetic head sample was integrated with the slider to obtain a composite type floating magnetic head.

Table 1 shows Bs of each soft magnetic thin film after welding. Bs was measured by VSM.

The composition and Bs were measured on a crystallized glass substrate on which a soft magnetic thin film was formed under the same conditions as in the production of the magnetic head and subjected to heat treatment under the same conditions as the heat treatment during the glass welding. It is. The composition was measured by SIMS. Sample No. 5 (Reference Example) in which the composition changes continuously shows the composition on the core side surface and the composition on the gap side surface. The core-side Bs and gap-side Bs in Sample No. 5 (Reference Example) were measured by forming a single-layer film having a core-side composition and a single-layer film having a gap-side composition.

With these magnetic heads, a 3.5-inch hard disk (Hc 1500 Oe, 3600 rpm)
Was recorded. The frequency characteristic curves of Sample Nos. 2 and 6 are shown in FIGS. 3 and 4, respectively. Table 1 shows the undulation width of the frequency characteristic curve of each sample.
The undulation width in this case is the difference between the peak and the valley of the output near 2 MHz.

The comparative samples Nos. 1 to 3 and N
o. Overwrite characteristics and saturation characteristics of the reference examples 5 to 6 and the sample of the present invention were measured. Regarding overwrite characteristics (O / W characteristics), sample Nos. 1-3
FIG. 5 (a) shows the result of Comparative Example and FIG.
FIG. 5 (b) shows the results of the reference examples and 6 (example), and FIG. 6 (a) shows the saturation characteristics of the samples Nos. 1-3 (comparative example). FIGS. 5 (reference example) and 6 (example) are shown in FIG.
The overwrite characteristic refers to the output of the 1f signal with respect to the output of the 2f signal when a 1.25 MHz 1f signal is recorded and then a 2.5 MHz 2f signal is overwritten thereon.

[0057]

[Table 1]

From the above results, the effect of the present invention is clear. That is, as is clear from FIGS. 3 and 4 and Table 1, in the sample of the present invention, the undulation of the frequency characteristic curve caused by the pseudo gap effect is extremely small. As is clear from FIGS. 5 and 6, the sample of the present invention shows that the pseudo gap effect is suppressed without impairing the favorable overwrite characteristics and saturation characteristics of Comparative Samples Nos. 2 and 3. Understand.

The yield of the sample of the present invention was improved by 10% or more as compared with the magnetic head using the conventional welding glass whose working temperature Tw was 550 ° C. or less.

In the sample No. 4, the core side Fe
The Hc of the -Ni (permalloy) film increased to 5 Oe by the heat treatment, and the film could not be used as a soft magnetic film.

When Mo, Ta, Ti, W, V and Nb were used as the underlayer, almost the same results were obtained, but the waviness of the frequency characteristics was the smallest in the case of the Cr underlayer.

[0062]

According to the present invention, in the MIG type magnetic head, since the soft magnetic thin film has a lower Bs on the core side and a higher Bs on the gap side, the pseudo gap effect can be significantly reduced while maintaining the effect of the MIG type magnetic head. .

Further, in the present invention, since the soft magnetic thin film is composed of a sendust-based alloy and a super sendust-based alloy, the soft magnetic thin film has a high heat resistance, and the holding temperature at the time of glass welding at the time of manufacturing a magnetic head is 600. ℃ or higher.
Therefore, a deposited glass having good environmental resistance and high mechanical strength can be used, and a magnetic head with high reliability and high production yield can be realized.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an example of a magnetic head of a reference example.

FIG. 2 is a partial sectional view showing an example of a magnetic head according to the present invention.

FIG. 3 is a graph showing frequency characteristics of a conventional magnetic head.

FIG. 4 is a graph showing frequency characteristics of the magnetic head of the present invention.

5A and 5B are graphs showing overwrite characteristics of a conventional magnetic head, a reference example, and a magnetic head of the present invention, respectively.

FIGS. 6A and 6B are graphs showing saturation characteristics of a conventional magnetic head, a reference example, and a magnetic head of the present invention, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st core 2 2nd core 3 Deposition glass 4 Soft magnetic thin film 41 Core side thin film 42 Gap side thin film 5, 51, 53 Gap 6 Base film

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masayuki Arakawa 1-1-13 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-62-185212 (JP, A) JP-A-64 -1110 (JP, A) JP-A-63-275005 (JP, A) JP-A-61-240412 (JP, A) JP-A-61-34707 (JP, A) JP-A-63-58607 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 5/127-5/255

Claims (6)

(57) [Claims] 1. A magnetic head having a pair of cores each made of ferrite, and a soft magnetic thin film having a higher saturation magnetic flux density than the core between at least one of the cores and a gap. The saturation magnetic flux density of the magnetic thin film is lower in the vicinity of the core than in the vicinity of the gap, and the soft magnetic thin film is composed of at least two thin films having different saturation magnetic flux densities. Core side thin film having a composition of 5% by weight, Si: 5 to 12% by weight, balance: Fe, Al: 3 to 7% by weight, Si: 3 to 8% by weight, Ni: 1 to 5% by weight, balance: Fe And a gap-side thin film having the following composition. 2. The method according to claim 1, wherein C is provided between the soft magnetic thin film and the core.
The magnetic head according to claim 1, further comprising a base film made of at least one of r, Mo, Ta, Ti, W, V, and Nb. 3. The magnetic head according to claim 1, wherein the pair of cores is welded and integrated by welding glass having a working temperature Tw of 300 to 850 ° C. 4. A method for manufacturing a magnetic head, comprising: a pair of cores each made of ferrite; and a soft magnetic thin film having a higher saturation magnetic flux density than at least one of the cores and the gap. The core is lower in the vicinity of the core than in the vicinity of the gap, and is composed of at least two thin films having different saturation magnetic flux densities; Al: 3 to 7% by weight; Si: 5 to 12% by weight; Soft magnetic thin film having a core-side thin film having a composition of Fe, and a gap-side thin film having a composition of Al: 3 to 7% by weight, Si: 3 to 8% by weight, Ni: 1 to 5% by weight, and the balance: Fe Forming a soft magnetic thin film and performing a heat treatment on the soft magnetic thin film. 5. A method according to claim 1, wherein C is provided between said soft magnetic thin film and said core.
5. The method of manufacturing a magnetic head according to claim 4, wherein a base film made of at least one of r, Mo, Ta, Ti, W, V and Nb is formed. 6. The method for manufacturing a magnetic head according to claim 4, wherein the pair of cores is welded and integrated by welding glass having a working temperature Tw of 300 to 850 ° C., and heat treatment is performed by heating at this time.