JPH05120624A - Magnetic head - Google Patents

Abstract

PURPOSE:To decrease a pseudo magnetic flux effect by constituting the soft magnetic thin film of the MIG type magnetic head to have the saturation magnetic flux density (Bs) lower on a core side and higher on a gap side. CONSTITUTION:This magnetic head has a pair of the cores 1, 2 constituted of ferrite and has the soft magnetic thin film 4 having the saturation magnetic flux density higher than the saturation magnetic flux density of the core 1 between at least one core 1 and a gap 5. This soft magnetic thin film 4 consists of Fe, Al and Si as its essential components and the saturation magnetic flux density of the soft magnetic thin film 4 is set lower near the cores 1, 2 than near the gap 5. The pseudo gap effect is thereby drastically decreased while the effect of the MIG type magnetic head is maintained. The soft magnetic thin film is formed of a 'SENDUST R' alloy, etc., by which the heat resistance of the soft magnetic thin film is enhanced.

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 saturation magnetic flux density higher than that of a core in a gap portion.

[0002]

2. Description of the Related Art In recent years, with the progress of information-oriented society, there is a strong demand for magnetic recording devices to have a large capacity, and it is an important issue in magnetic recording technology to further increase the recording density. To address this issue, the medium has a high coercivity (Hc)
Technology has been developed.

On the other hand, magnetic heads having a magnetic core of ferrite have been mainly used in the past, but in recent years,
A so-called MIG (metal-in-gap) type magnetic head in which a metal soft magnetic thin film such as sendust or a Co-based amorphous material is formed in a gap of a ferrite magnetic head has appeared. The saturation magnetic flux density (Bs) of ferrite is about 500
Since it is about 0 G, Hc of the medium which can be recorded by the conventional ferrite head is limited to about 800 to 900 Oe. Therefore, it is necessary to enhance the recording ability of the magnetic head as the Hc of the medium increases. As a means for that, a high B such as sendust is added to the gap of the conventional ferrite head.
s A MIG type magnetic head having 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 is possible to record even on a high Hc medium. For example, sendust whose Bs is about 10 kG is recorded on the soft magnetic thin film. When used as
Recording is now possible on media with c up to about 1300 Oe. Further, when Super sendust having a Bs of about 15 kG or a Fe-Me (Me is Zr, Mo, Ta, etc.)-N based thin film was used, it was possible to record on a medium having a 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 occur. 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 the oxidation or reduction of metal or oxide, or the characteristic component in the soft magnetic thin film (for example, in the Sendust film, Al , Si) is diffused to the interface to form a non-magnetic layer, or is due to an initial deterioration layer that occurs during the formation of the soft magnetic thin film, and various discussions have been made.

In digital recording, so-called bit shift occurs due to the presence of the sub-pulse, and the waveform shifts in the time axis direction, so that the recording wavelength cannot be shortened. Also, in analog recording, due to the presence of sub-pulses,
Periodic undulation occurs in the frequency characteristic curve.

In order to reduce such a pseudo-gap effect, Ni-- is formed between the sendust thin film and the ferrite core.
Attempts have been made to provide a Fe (permalloy) thin film as a base film. However, when the Ni-Fe thin film is heat-treated at 600 ° C. or higher, Ni diffuses into the sendust and the magnetic permeability is significantly reduced (Journal of Applied Magnetics, Japan 13,277-2).
80 (1989)). Therefore, when the Ni-Fe base film is used, glass having a welding temperature of 600 ° C or higher cannot be used.

In order to obtain a so-called low melting point 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 the environment resistance such as humidity resistance becomes insufficient, and the mechanical properties The target strength is also reduced. Therefore, conventionally
Glass used as a fused glass has low environmental resistance and poor mechanical strength. Therefore, it has not been possible to achieve both reduction of the pseudo gap effect and improvement of reliability and manufacturing yield.

[0009]

SUMMARY OF THE INVENTION The present invention has been made under such circumstances, and an object of the present invention is to provide a MIG type magnetic head which has a small pseudo gap effect, and has high reliability and high manufacturing yield. ..

[0010]

These objects are achieved by the present invention described in (1) to (7) below.

(1) A magnetic head having a pair of cores each made of ferrite, and a soft magnetic thin film having a saturation magnetic flux density higher than that of the core between at least one of the cores and the gap, The soft magnetic thin film is Fe,
A magnetic head comprising Al and Si as main components, wherein a saturation magnetic flux density of the soft magnetic thin film is lower near the core than near the gap.

(2) The magnetic head according to (1), wherein the saturation magnetic flux density of the soft magnetic thin film gradually decreases from the side in contact with the gap to the side in contact with the core.

(3) The magnetic head according to (2) above, wherein the composition of the soft magnetic thin film is Al: 3 to 7% by weight, Si: 5 to 12% by weight, and the balance: Fe.

(4) The soft magnetic thin film is composed of at least two thin films having different saturation magnetic flux densities.
The magnetic head described in 1.

(5) The soft magnetic thin film comprises: a core side thin film having a composition of Al: 3 to 7% by weight, Si: 5 to 12% by weight, and balance: Fe; Al: 3 to 7% by weight, Si: The magnetic head according to (4) above, which comprises 3 to 8% by weight, Ni: 1 to 5% by weight, and the balance: a thin film on the gap side having a composition of Fe.

(6) An undercoating film composed of at least one of Cr, Mo, Ta, Ti, W, V and Nb is provided between the soft magnetic thin film and the core, and the above (1) to (5) are provided. ) The magnetic head as described in any one of 1.

(7) Working temperature Tw is 300 to 850 ° C.
7. The magnetic head according to any one of the above (1) to (6), wherein the pair of cores are fused and integrated by the fused glass of.

[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 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 difference of s, the pseudo gap effect can be significantly reduced. Further, since the soft magnetic thin film near the gap has the same Bs as that of the conventional one, the high writing ability is unchanged.

Moreover, the soft magnetic thin film is composed of a sendust-based alloy containing Fe, Al and Si as main components, and Fe and A.
Since it is a super sendust-based alloy containing 1, 1, Si and Ni as the main components, it has high heat resistance, and 6
There is no deterioration in magnetic properties even when heat-treated at a temperature of 00 ° C. or higher. Therefore, a fused glass having good environment resistance and high strength can be used, and a magnetic head having high reliability and high manufacturing yield can be realized.

Further, by providing the base film, the adhesiveness between the soft magnetic thin film and the core is improved. In particular, when the base film is made of Cr, the pseudo gap effect can be further reduced.

By the way, Japanese Patent Application Laid-Open No. 61-34707 discloses an MIG type magnetic head using a ferrite core. The gap portion of this magnetic head constitutes 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 sequentially arranged. 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]

Specific Structure Hereinafter, a specific structure of the present invention will be described in detail with reference to the accompanying drawings. The magnetic head of the present invention shown in FIGS. 1 and 2, respectively, has a pair of cores of a first core 1 and a second core 2, and both cores are integrated by a fused glass 3 via a gap 5. , The second core 2
And the gap 5 have a soft magnetic thin film 4 having a larger Bs than each core. The winding is usually wound around the first core 1.

The soft magnetic thin film 4 has a composition containing Fe, Al and Si as main components, and is configured so that Bs is smaller near the second core 2 than near the gap 5.
In order to make Bs have such a distribution, the Bs of the soft magnetic thin film 4 may be gradually reduced from the side in contact with the gap 5 to the side in contact with the second core 2, or the Bs The soft magnetic thin film 4 may be composed of at least two different thin films.

The magnetic head shown in FIG. 1 has a soft magnetic thin film 4 in which Bs is gradually reduced. Bs like this
The soft magnetic thin film 4 having a distribution can be formed by continuously changing the content ratio of constituent elements. In this case, the total composition of the soft magnetic thin film 4 is preferably Al: 3 to 7% by weight, Si: 5 to 12% by weight, and the balance: Fe. By providing a composition distribution such that the content ratios of Si and Al gradually decrease from the second core 2 side to the gap 5 side, Bs can be gradually decreased from the gap 5 side to the second core 2 side. .. Specifically, the content ratios of Al and Si in the vicinity of the second core 2 are preferably Al: 7 to 9% by weight and Si: 10 to 15% by weight, and A in the vicinity of the gap 5 is A.
The content ratio of 1 and Si is preferably Al: 1 to 4% by weight and Si: 3 to 8% by weight.

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

The magnetic head shown in FIG. 2 has a soft magnetic thin film 4 composed of two thin films having different Bs. The soft magnetic thin film 4 is composed of a core-side thin film 41 on the second core 2 side and a gap-side thin film 42 on the gap 5 side,
The core side thin film 41 is Bs more than the gap side thin film 42.
Is low. In this configuration, the core-side thin film and the gap-side thin film are each composed of a sendust-based alloy, and the composition of each thin film may be the composition in the vicinity of the core and the composition in the vicinity of the gap of the composition continuously changing film described above, but preferably, the core side. It is preferable that the 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 preferably Al: 3 to 7% by weight, Si: 5 to 12% by weight, and the balance: Fe, and the composition of the gap side thin film is Al: 3 to 7% by weight. It is preferable that Si: 3 to 8% by weight, Ni: 1 to 5% by weight, and the balance: Fe. By appropriately selecting the composition of each thin film from such a range, the core-side thin film has a composition of 8,000.
~ 11,000G, 12000 for thin film on the gap side
Bs of about 15,000 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 the core thin film described above, and the thin film closest to the gap is the gap thin film described above. The Bs of the thin film existing between the two thin films is preferably higher than the core-side thin film and lower than the gap-side thin film.

The Bs of the ferrite core is 3000
It is about 6000G.

The soft magnetic thin film 4 includes, in addition to Fe, Si, Al and Ni, Cr, Mo, Ti, Ta, W, Zr, Hf,
Ga, Ru, Au, Ag, Co, Zn, Sn and the like may be contained in an amount of 1 atom% or less based on the whole.
It is preferable to contain Au because the soft magnetic characteristics are 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. When 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. Further, if the film thickness exceeds the above range, especially 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 ratio of the thickness of each thin film is not particularly limited, but normally the thickest thin film is 3 times or less than the thinnest thin film, It is preferably set to be 1.5 times or less.

In the present invention, it is preferable to provide a base film 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 preferable. By forming the base film 6 of 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.

The thickness of the base film 6 is usually 0.001 to
The thickness is preferably 0.1 μm, and more 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 the thickness exceeds the above range, the volume of the soft magnetic thin film cannot be sufficiently increased.

In the illustrated example, the soft magnetic thin film 4 is provided between the second core 2 and the gap 5, but it may be provided between the first core 1 and the gap 5. Moreover, you may provide a soft magnetic thin film to both cores as needed. In that case, it is preferable to provide a base film on both cores.

In the present invention, each core is made of ferrite. There is no particular limitation on the ferrite used, but M
It is preferable to select n-Zn ferrite or Ni-Zn ferrite according to the purpose. As Mn—Zn ferrite, Fe ₂ O _{3 of} about 50 to 60 mol%, ZnO
It is preferably about 8 to 25 mol% and the balance substantially MnO. 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%.

The direct current Bs of each core is preferably 30
It is set to 00-6000G. If the Bs is less than the above range, the overwrite characteristic is deteriorated and the Bs
With the above composition, the Curie temperature becomes low, so that the thermal stability deteriorates. If the amount exceeds the above range, magnetostriction increases to deteriorate the characteristics of the magnetic head, and it becomes easy to magnetize.

The initial magnetic permeability μ _i of each core is 100
It is preferable that 0 or more and Hc be 0.3 Oe or less.

Further, it is preferable that the gap facing surface of each core is smoothed by mirror polishing or the like so that the soft magnetic thin film 4 and the base film 6 are 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. For example, Japanese Patent Application No. 1-7150
The glass shown in No. 6 or the like is suitable. Further, the gap 5 may be composed of only the adhesive glass, but it 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 forming speed and the gap strength. In this case, it is preferable to use SiO ₂ for the gap 51 and adhesive glass for the gap 53. In the case of a magnetic head in which the fused glass 3 flows into both sides of the gap, the gap 5 may be made of silicon oxide only. The method for forming the gap 5 is not particularly limited, but it is preferable to use the 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. When the composition is such that the composition continuously changes from the core side to the gap side, the vapor deposition method is preferably used. in this case,
Due to the difference in vapor pressure, Al and Si are likely to evaporate initially, and a low Bs film having a high ratio of these is formed. Then, the evaporation amounts of Al and Si gradually decrease, and
It changes to a high Bs film with a high ratio of. Al and Si
By properly selecting the amount of Bs and the heating power, it is possible to realize an arbitrary Bs and its change pattern.

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

In the case of a composite type flying magnetic head, the magnetic head having the structure shown in FIGS. 1 and 2 is bonded to the slider by glass in the secondary welding process.

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 rise even if it is welded using such Tw glass, and a good softness is obtained. The magnetism is retained. For this reason, since a fused glass containing a small amount of lead, alkali metal, etc. can be used, a magnetic head having good environmental resistance and high mechanical strength can be realized.

The soft magnetic thin film is preferably subjected to a heat treatment in order to improve the soft magnetic characteristics. However, since the 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 is of a tunnel erase type such as a so-called laminate type or a bulk type, or a floppy head for overwriting recording such as a read / write type without an erase head, a flying type of a monolithic type or a composite type. It is used as various magnetic heads such as computer heads, rotary VTR heads and R-DAT heads.

The present invention relates to a MIG type magnetic head.
It can be applied to a so-called enhanced dual gap length (EDG) type magnetic head. In that case, a soft magnetic thin film having a lower Bs than that of the core is provided on the core facing the soft magnetic thin film with a gap in between. That is, in the configuration shown in FIG. 1, the first core 1
A soft magnetic thin film having Bs lower than that of the ferrite forming the core is provided between the gap 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 produced. 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 the sputtering method,
The thickness was 2 μm. However, in Sample No. 5, the film was formed by the vapor deposition method and the composition was changed continuously by utilizing the difference in vapor pressure of the vapor deposited elements.

The base film 6 is a 0.01 μm thick Cr film, and was formed by the sputtering method.

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

SiO ₂ was used for the gap 51 and was formed by the sputtering method, and the thickness thereof was 0.3 μm. For the gap 53, an adhesive glass having a working temperature Tw of 800 ° C. was used. The gap 53 was formed by the sputtering method, and the thickness thereof was 0.1 μm.

The composition of the fused 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. It was 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 a slider to form a composite type flying magnetic head.

Table 1 shows the 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 a magnetic head and subjected to a heat treatment under the same conditions as those for glass welding. Is. The composition was measured by SIMS. Sample No. 5 in which the composition changed continuously showed the composition of the core side surface and the composition of the gap side surface. The core side Bs and the gap side Bs in sample No. 5 were measured by forming a single layer film having a core side composition and a single layer film having a gap side composition, respectively.

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 waviness width in this case is the difference between the peaks and troughs of the output near 2 MHz.

Further, comparative samples Nos. 1 to 3 and N
o. The overwrite characteristics and the saturation characteristics of the samples of the present invention of 5 to 6 were measured. Overwrite characteristics (O
/ W characteristics), sample No. 1-3 (comparative example)
Fig. 5 (a) shows that of Sample Nos. 5 and 6 (Example), and Fig. 5 (b) shows that of Saturation characteristics of Sample Nos. 1-3 (Comparative Example). 6A is shown in FIG. 6A, and those of Sample Nos. 5 and 6 (Examples) are shown in FIG. 6B. The overwrite characteristics are
This is the output of the 1f signal with respect to the output of the 2f signal when the 1f signal of 1.25 MHz is recorded and then the 2f signal of 2.5 MHz is overwritten from above.

[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 waviness of the frequency characteristic curve due to the pseudo gap effect is extremely small. Further, as is clear from FIGS. 5 and 6, the samples of the present invention have suppressed the pseudo-gap effect without impairing the good overwrite characteristics and saturation characteristics of Comparative Sample Nos. 2 and 3. Recognize.

Further, the sample of the present invention has a yield improved by 10% or more as compared with the magnetic head using the conventional fused glass having a working temperature Tw of 550 ° C. or less.

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

Even 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 Cr underlayer.

[0062]

According to the present invention, in the MIG type magnetic head, since Bs of the soft magnetic thin film is configured to be low on the core side and high 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 the sendust type alloy or the super sendust type alloy,
The soft magnetic thin film has high heat resistance, and the holding temperature at the time of glass welding in manufacturing a magnetic head can be increased to 600 ° C. or higher. Therefore, a fused glass having good environment resistance and high mechanical strength can be used, and a magnetic head with high reliability and high manufacturing yield can be realized.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an example of a magnetic head of the present invention.

FIG. 2 is a partial cross-sectional view showing an example of a magnetic head of 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 and a magnetic head of the present invention, respectively.

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

[Explanation of symbols]

 1 1st core 2 2nd core 3 Welding glass 4 Soft magnetic thin film 41 Core side thin film 42 Gap side thin film 5,51,53 Gap 6 Underlayer film

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masayuki Arakawa 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation

Claims (7)

[Claims] 1. A magnetic head comprising a pair of cores each made of ferrite, and a soft magnetic thin film having a saturation magnetic flux density higher than that of the core between at least one core and the gap, A magnetic head, wherein the magnetic thin film contains Fe, Al and Si as main components, and the saturation magnetic flux density of the soft magnetic thin film is lower near the core than near the gap. 2. The magnetic head according to claim 1, wherein the saturation magnetic flux density of the soft magnetic thin film gradually decreases from the side in contact with the gap to the side in contact with the core. 3. The magnetic head according to claim 2, wherein the composition of the soft magnetic thin film is Al: 3 to 7% by weight, Si: 5 to 12% by weight, and the balance: Fe. 4. The magnetic head according to claim 1, wherein the soft magnetic thin film is composed of at least two layers of thin films having different saturation magnetic flux densities. 5. The soft magnetic thin film comprises: a core side thin film having a composition of Al: 3 to 7% by weight, Si: 5 to 12% by weight, balance: Fe; Al: 3 to 7% by weight, Si: 3 The magnetic head according to claim 4, further comprising: a thin film on the gap side having a composition of -8% by weight, Ni: 1-5% by weight, and the balance: Fe. 6. C is provided between the soft magnetic thin film and the core.
6. 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. 7. The magnetic head according to claim 1, wherein the pair of cores are fused and integrated by a fused glass having a working temperature Tw of 300 to 850 ° C.