JPH04281202A - Composite type magnetic head and its production - Google Patents

Abstract

PURPOSE:To produce a magnetic head having high quality recording and reproducing properties by interposing a Cr-rich layer and a Fe-rich layer between the jointing surface of a core and a metallic magnetic thin film in the head and preventing the occurrence of a pseudo gas even if Cr diffuses to the Fe-rich layer since the Fe-rich layer have magnetism. CONSTITUTION:An I core 5 and a C core 6 are separately formed by using a Mn-Zn ferrite. The core 5 is put in a spattering device and the jointing surface is spattered with the Cr. Then, without exposing a obtained Cr layer to oxidizing atmosphere such as the atmosphere, Fe is spattered on this layer, thereafter, without exposing the Fe layer to the oxidizing atmosphere similarly, a Fe-Al-Si based thin film 23 is applied on this layer, then, a Cr layer is diffused to be vanished by heat treatment. After the Cr of the Cr layer are diffused to the Fe layer and the-Cr rich layer 21, the Fe-rich layer 22 and the thin film 23 are laminated in such a manner, the core 5 and the core 6 having a magnetic layers stuck thereto are joined with glass 7.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite magnetic head for recording and reproducing information to and from a magnetic disk in a magnetic disk drive, and a method for manufacturing the same. More specifically, the present invention relates to a so-called floating magnetic head having an air bearing surface and a method of manufacturing the same.

0002

2. Description of the Related Art A floating magnetic head consists of a monolithic head in which a slider and a head chip are integrally formed using a magnetic material (for example, Mn-Zn ferrite), and a monolithic head made of a non-magnetic material (for example, CaTiO3, Al2O3-TiC).
) and composite heads in which a magnetic head chip made of magnetic material is embedded in a slider. The monolithic head has the configuration shown in FIG. 9, and the composite head has the configuration shown in FIG. 7. The composite head shown in FIG. 7 will be explained below as an example. A magnetic head chip 1 is attached to a slider 2, and the slider 2 has two air bearing surfaces 3 and 4. In this composite head, a slit 9 in the longitudinal direction of the slider is provided at the exit end of the air flow flowing along the air bearing surface 3 of the slider 2, and the magnetic head chip 1 is inserted into this slit 9 and bonded with glass. It is buried. The magnetic head chip 1 has the configuration shown in FIG.
It has a pair of cores 5 and 6 joined by a glass 7, and the core 5
, 6, a metal magnetic thin film 11 is interposed therebetween, and a gap 8 is formed. One core 5 is linear I-shaped, and the other core 6 is C-shaped, with a winding window 10 provided in the center. Also, magnetic head chip 1
is protruded so that the surface facing the disk is approximately the same as the track width of the disk. In addition, cores 5 and 6 are Mn
It is formed of Mn-Zn ferrite mainly composed of O, ZnO and Fe2O3.

Then, the gap 8 of the magnetic head chip is made to face the disk, and the magnetic change generated from the disk is detected by the gap 8, and the magnetic head reads the information recorded on the disk, or conversely, the magnetic flux generated from the gap 8 is detected. Depending on the change, it may be recorded on a disc.

In the field of magnetic recording, studies are underway to increase the density of recording both in terms of recording media, such as disks and magnetic heads. Since the ferrite head has a saturation magnetic flux density of about 5000 G, it has become impossible to generate a head magnetic field sufficient to saturate the medium. For this reason, as shown in FIG. 8, a magnetic head has been used in which a metal magnetic thin film 11 having a high saturation magnetic flux density is attached by sputtering or the like to the joint surface of the I core to the C core.

However, in this magnetic head chip 1, a reaction occurs at the joint surface between the ferrite core 5 and the metal magnetic thin film 11, forming a non-magnetic reaction layer, which causes deterioration of the recording and reproducing characteristics. There is. That is, as shown in FIG. 10, in addition to the reproduction output E1 due to the gap 8, another reproduction output E2 is generated due to the reaction layer becoming a pseudo gap. This may cause fluctuations in the frequency characteristics of the reproduced signal, leading to a decrease in the performance of the magnetic head due to a decrease in the reproduction output. Further, when a metal magnetic thin film is directly deposited on the core 5 by sputtering or the like, there is a problem that the bonding strength is low and the metal magnetic thin film peels off.

In order to improve the bonding strength of the metal magnetic thin film, a magnetic head is also known in which a Cr layer is formed on the joint surface of the core by sputtering, and a metal magnetic thin film is further formed on the surface of the Cr layer by sputtering. ing. However, even in this case, there was a problem that the Cr layer became a pseudo gap.

In order to prevent this Cr layer from forming a pseudo gap, a structure in which Cr is diffused has been proposed (Japanese Unexamined Patent Publication No. 2-273305). That is, a Cr film is formed on the joint surface of the core by sputtering or the like, and Cr is reacted with oxygen in the ferrite of the core to form a 3-100 Å thick Cr oxide layer or the like between the Cr layer and the ferrite. Next, a metal magnetic thin film (Fe-Al-Si alloy thin film) is formed on the surface of the Cr layer by sputtering or the like without bringing the Cr layer into contact with an oxidizing atmosphere, and Cr is diffused into the metal magnetic thin film. Even in such a case, the pseudo gap can be suppressed because Cr diffuses and the thickness of the nonmagnetic layer becomes thinner, but there is a problem in that the magnetic properties of the metal magnetic thin film are deteriorated.

[0008] Furthermore, when the Cr layer diffuses into the metal magnetic thin film,
In order to prevent the recording and reproducing characteristics from deteriorating, a Cr layer that strengthens the adhesion between the metal magnetic thin film and the ferrite core, and an F
It is known that a non-magnetic oxide film of SiO2 or Al2O3 with a thickness of 50 to 200 Å is formed as a diffusion prevention film between an e-Al-Si alloy thin film (Japanese Unexamined Patent Application Publication No. 1999-1-1999).
260615). However, in this case, Cr is Fe-Al-
Although diffusion into the Si-based thin film can be prevented, there is a problem in that the Cr film and the nonmagnetic oxide film act as a pseudo gap layer.

Furthermore, due to the difference in thermal expansion coefficient at the joint surface between the ferrite core and the metal magnetic thin film, the magnetic properties of the initial layer of the metal magnetic thin film deteriorate, resulting in magnetic discontinuity at the joint with the ferrite core. There is also a known method that prevents the occurrence of pseudo gaps (Japanese Patent Laid-Open No. 63-2794).
04). That is, when a ferromagnetic Fe having a bcc structure or a Fe-based alloy thin film and a Fe-Al-Si based thin film are laminated in this order on a strain-free and highly flattened ferromagnetic oxide surface (core surface), the underlying Fe or Fe F along the crystal orientation of the thin film
It is said that an e-Al-Si thin film is formed, the crystal orientation of the initial layer is less disturbed, and the soft magnetic properties are easily improved by heat treatment. The preferred conditions for the core surface and thin film during film formation are that the substrate needs to have a flat surface of 40 Å or less, and the thickness of the ferromagnetic Fe or Fe-based alloy thin film should be 0.1
~0.5 μm, the thickness of the Fe-Al-Si alloy thin film is 0
．． The thickness is set at 1 to 10 μm.

0010

As mentioned above, in a magnetic head, a Cr layer is formed on the ferrite core surface, and the Cr layer is formed on the ferrite core surface.
There is one in which r is diffused into a metal magnetic thin film so that the Cr layer does not act as a pseudo gap layer. In this case, in order to improve the soft magnetic properties of the Fe-Al-Si alloy thin film, it is annealed at around 650°C, so the vicinity of the interface between the Cr layer and the metal magnetic thin film reacts and becomes a layer with deteriorated magnetic properties. On the other hand, there was a problem of a false gap. Note that there are some types in which a diffusion prevention film such as SiO2 is formed between the Cr layer and the metal magnetic thin film to prevent a reaction-degraded layer from forming between the two, but in that case, the Cr layer and the diffusion prevention film form a pseudo gap. It becomes layers.

[0011] Also, on the surface of the strain-free and highly flattened magnetic core, bc
A magnetic head in which a metal magnetic thin film is attached via a c-structure Fe or Fe-based alloy thin film prevents the crystal orientation of the initial layer from being disturbed due to the difference in thermal expansion coefficient between the core and the metal magnetic thin film. It is something. In other words, the premise for solving the problem is different from that in which a Cr layer is interposed between the core surface and the metal magnetic alloy thin film in order to improve the bonding strength as described above. In this case, the bond between the core and the Fe film reacts to form a degraded layer, which tends to form a pseudo gap, and the bond strength is insufficient. Therefore, the present invention provides carbon fiber on the core surface of a magnetic head to improve bonding strength.
By intervening the r layer and further intervening the Fe film, the purpose is to suppress deterioration of magnetic properties due to diffusion of Cr from the Cr layer into the metal magnetic thin film.

0012

[Means for Solving the Problems] A composite magnetic head of the present invention has a pair of ferrite cores arranged facing each other through a magnetic cap, and a metal magnetic thin film is coated on the opposing surface of at least one of the cores. It is characterized in that a Cr-rich layer, an Fe-rich layer, and a metal magnetic thin film are laminated in this order on the surface of a ferrite core.

[0013] The thickness of the Cr-rich layer is 20 to 200 Å, F
The thickness of the e-rich layer is preferably 150 to 1500 Å, more preferably 500 to 1000 Å. Further, it is desirable that the metal magnetic thin film has a thickness of 0.5 to 2 μm. The thickness of the Cr-rich layer was set to the above range at 20
This is because if the thickness is smaller than Å, the bonding strength cannot be improved, and if it is larger than 200 Å, a pseudo gap is likely to occur. The reason why the thickness of the Fe-rich layer was set to the above range was 150 Å.
If it is smaller, the diffusion of Cr into the metal magnetic thin film will not be sufficiently prevented and the effect of improving the magnetic head characteristics will not be seen. Also 15
If it is thicker than 00 Å, the soft magnetic properties of Fe-Al-Si will deteriorate, which is not preferable.

As the metal magnetic thin film, a Fe-Al-Si magnetic thin film usually called sendust can be used, and in addition, permalloy Fe-Ni, Fe-Ni with high saturation magnetic flux density can be used.
Si thin film, Fe-Al thin film, high saturation magnetic flux density, high permeability amorphous alloy such as Co-Nb (
It is preferable to use a Ta)-Zr thin film deposited by sputtering or the like. These thin films may contain 2% by weight or less of Cr or a noble metal element.

The method for manufacturing a composite magnetic head of the present invention includes:
A step of depositing Cr on the bonding surface of one of a pair of ferrite cores bonded by glass to form a Cr layer, and a step of depositing Fe on the surface of the Cr layer without bringing it into contact with a reactive gas atmosphere a step of depositing a layer of Fe on its surface without contacting said Fe layer with a reactive gaseous atmosphere;
-A process of depositing an Al-Si based thin film, a heat treatment process of diffusing Cr in the Cr layer into the Fe layer, and a process of bonding a pair of ferrite cores with glass.

In the method for manufacturing a composite magnetic head,
It is desirable to perform Cr diffusion and glass bonding in the same process. The heat treatment performed after forming the Fe layer is 640~
It is desirable to hold the temperature at 730°C for 10 to 25 minutes. Further, the atmosphere in which the thin film is deposited is one in which the sum of H2O partial pressure and O2 partial pressure is 10-1 Pa or more. When performing sputtering for depositing each thin film, the sum of the H2 O partial pressure and the O2 partial pressure is preferably kept below 10<-1>Pa, preferably below 10<-2>Pa throughout the entire process.

[0017]

[Function] Since the Cr layer, Fe layer, and magnetic alloy magnet thin film are laminated in this order on the bonding surface of the ferrite, the Cr layer
is diffused into the Fe layer by heat treatment, and some Cr is diffused into the metal magnetic thin film, but it does not diffuse to the extent that it deteriorates the magnetic properties, and no altered layer is produced in the metal ferromagnetic alloy thin film. Part of the Cr layer undergoes an oxidation reaction on the core surface and remains at the boundary as an extremely thin Cr oxide layer, but most of it diffuses into the Fe layer, so the Cr layer does not act as a pseudo gap. Furthermore, since the Fe layer is a magnetic film, a pseudo gap will not occur even if it is interposed as a base for a metal magnetic thin film and Cr is diffused therein. In this way, the metal magnetic thin film is laminated on the bonding surface of the ferrite core via the Cr-rich layer and the Fe-rich layer, making it possible to significantly reduce the pseudo gap without deteriorating the magnetic properties of the metal magnetic thin film. Moreover, the Cr-rich layer increases the bonding strength.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic head of the present invention will be described with reference to FIG. 1 showing a magnetic core and FIGS. 2(a) and 2(b) showing a portion of the magnetic head facing a magnetic recording medium. The magnetic I core 5 and C core 6 that constitute this magnetic head are made of Mn-Z.
It is formed of n-ferrite and has a thickness of 2 on the joint surface of the I-core 5.
Cr-rich layer 21 with a thickness of 0 to 200 Å and a thickness of 150 to 150 Å
0 Å thick Fe-rich layers 22 are stacked in this order. Cr
The rich layer 21 is mainly made of Cr, the Fe rich layer 22 is mainly made of Fe, and the constituent members Mn-Zn, Cr, F
The elements e, Fe-Al-Si are mutually diffused. The Cr-rich layer 21 contains F from the front gap forming surface to the back gap forming surface via the Fe rich layer.
An e-Al-Si thin film 23 is deposited to a thickness of 0.5 to 2 μm, and the Fe-Al-Si thin film 23 and the core 6 are bonded with a glass 7 with a gap 8 between them. Note that FIGS. 1 and 2 are schematic diagrams, and the Cr-rich layer 21, F
Although the e-rich layer 22 and the Fe-Al-Si layer 23 are shown with a certain thickness, these thicknesses range from 20 to 150 mm.
It is less than 0 Å or several μm and cannot be discerned with the naked eye. In FIG. 2, (a) is an example in which a metal magnetic thin film is deposited on one core surface, and (b) is an example in which the I core and C
A Cr-rich layer, a Fe-rich layer, and an F layer are provided on both sides of the core, respectively.
This is an example in which e-Al-Si thin films are laminated, and in this case, the Fe-Al-Si thin films are bonded together with glass. Furthermore, the present invention is highly effective even when applied to the monolithic head shown in FIG. 9 using Mn--Zn polycrystalline ferrite or the like.

Next, a method of manufacturing the above magnetic head will be explained. First, the I core 5 and the C core 6 are made separately using Mn-Zn ferrite. Next, put the I core 5 into a sputtering device, and apply 20 to 200 Å of Cr on the joint surface of the I core 5.
sputter to a thickness of . During this sputtering, oxygen in the ferrite on the core side reacts with Cr, probably due to the energy of the Cr atoms colliding with the ferrite surface, and at least a portion of the oxidized Cr layer is formed. Cr
After forming the Cr layer, 150 to 150 Fe is added on top of the Cr layer without bringing the Cr layer into contact with an oxidizing atmosphere such as the atmosphere.
Sputter to a thickness of 0 Å. Next, F is applied on the Fe layer without bringing the Fe layer into contact with an oxidizing atmosphere such as the air.
The e-Al-Si thin film 23 is sputtered to a thickness of 0.5 to 2 μm. After this, C
Diffuse and eliminate the r layer. At this time, it is considered that the oxidized layer of Cr at the boundary between the ferrite core and the Cr layer also increases. In this case, the heat treatment temperature is preferably maintained at 640 to 730°C for 10 minutes or more. As a result, Cr in the Cr layer is diffused into the Fe layer, and the Cr-rich layer 21, Fe-rich layer 22, F
The e-Al-Si layer 23 is laminated in this order. The I core 5 with the magnetic film attached in this manner is coupled to the C core 6 through the glass 7. This glass has a higher softening point than that used when fixing the magnetic head to the slider. The reason for this is to prevent the glass 7 connecting the I core and C core from softening when heated to fix the magnetic head to the slider.

In the present invention, after forming the Fe layer and the Fe-Al-Si layer on the Cr layer, heat treatment only for Cr diffusion is not performed, but instead, the I core 5 and the C core 6 are When heating for glass bonding, the Cr layer may be diffused into the Fe layer. This reduces the number of heat treatment steps by one. The temperature at which the cores are glass-bonded is preferably 640 to 730°C. When diffusing Cr during glass bonding, the heating time is preferably 10 minutes or more, particularly 20 minutes or more,
Cr is sufficiently diffused into the Fe layer. In addition, I of C core 6
A metal magnetic thin film with high magnetic permeability may also be formed on the joint surface to the core 5.

[0021] Suitable Fe-A used in the present invention
As the l-Si thin film 23, Al: 2 to 1 in weight%
0%, Si: 3 to 16%, and the remainder substantially Fe. Particularly preferred is one containing Al: 4 to 8%, Si: 6 to 11%, and the balance being substantially Fe. Note that it is preferable that Ti, Cr, and Ru each be contained in an amount of 2% or less since corrosion resistance and wear resistance can be improved.

The constituent material of the I core 5 and C core 6 is M.
N-Zn ferrite, Ni-Zn ferrite, etc. are suitable. A preferable composition of Mn-Zn ferrite is as follows:
MnO: 25-37%, ZnO: 8-23%, in mol%
Fe2O3: 51 to 60% is mentioned. SiO2 − is used as the glass for bonding the I core and C core.
There are PbO-R2 O (R is an alkali metal) type glass and SiO2 -PbO-R2 O-B2 O3 type glass. Its composition is illustrated below. This glass has a softening point of 560-580°C. SiO2...28~49wt%
Na2O‥‥7～13wt% B2
O3 ‥‥ 5-15wt% PbO
An example of glass for bonding the remaining magnetic head to the slider is PbO-SiO2-A.
There is l2 O3 -B2 O3 type glass. An example of the composition of this glass is shown below. PbO‥‥‥‥78-83wt%
SiO2...6~13wt% Al2O
3 ‥‥ 3~10wt% B2 O3
The softening point of this glass containing 4 to 10 wt% PbO as a main component is 410 to 450°C. The invention will now be explained in more detail with reference to manufacturing examples.

(Embodiment 1) The I core 5 is placed in a sputtering apparatus having a high performance exhaust system. After evacuating this system to the following conditions, metal Cr (purity 99.99% or more), metal Fe (purity 99.99% or more) and Fe-Al-S
Each of these thin films is sequentially formed using each target of i-alloy. Exhaust characteristics are H2O partial pressure <10-2Pa, O
2 The partial pressure was <10-2 Pa and the core temperature was 300°C. The sputtering conditions were as follows: sputtering power 1kw, Cr film thickness 1kw, Cr film thickness 1kw.
00 Å, Fe film thickness 500 Å, Fe-Al-Si film thickness 1.
It was set to 5 μm. Further, the I core was heat-treated at a temperature of 600° C. for 30 minutes to diffuse Cr in the Cr film. After this, SiO2 35wt%, B2O3 10w
The I core and the C core were bonded using glass having a composition of 10 wt % Na2O, the balance PbO, and a softening point of 570°C. The heating temperature was 700°C, the time was 60 minutes, and the atmosphere was N2.

FIG. 3 is an enlarged photograph of the metallographic structure of the main part of the surface of the manufactured magnetic head facing the magnetic recording medium. From FIG. 3, it can be seen that the Cr film, Fe film, and Fe-Al-Si film (sendust film) each have a different laminated structure in the portions corresponding to the initially formed film thicknesses. Note that in FIG. 3, ferrite represents the core portion. FIG. 4 shows the results of detailed analysis of the portion shown in FIG. 3 using a scanning electron microscope. It can be confirmed from FIG. 4 that the Cr film is a Cr-rich layer, and the Fe film is an Fe-rich layer. Furthermore, when the isolated waveform of the magnetic head was measured, it was as shown in FIG. 5, and it was found that no pseudo gap was generated.

(Example 2) In the same manner as in Example 1, the Fe-rich layer was 100 Å, 200 Å, 500 Å, 1200 Å,
FIG. 6 shows the measured reproduction output and bit shift of each 1500 Å magnetic head and a comparative magnetic head prepared without an Fe-rich layer. From Figure 6, the playback output is from 200 Å to 1500 Å for Fe film thickness.
It can be seen that the sample is larger than the comparative example. Further, the bit shift is lower when the Fe film thickness is from 200 Å to 1500 Å than that of the comparative example, indicating that the magnetic head characteristics are good.

(Example 3) Next, the magnetic heads made in Example 1 using Cr and Fe (thickness: 500 Å) as a base and various comparative magnetic heads were made, and the respective metal magnetic The adhesion strength, pseudo gap, reproduction output, and bit shift of the thin film were measured and shown in Table 1. Note that the adhesion force was determined by a scratch method. Comparative magnetic heads include those without a base material interposed between the joint surface of the core and the metal magnetic thin film, those with a Cr base, those with a Cr diffusion layer, those with Fe as a base, A substrate made of Cr and SiO2 was used. As can be seen from Table 1, the adhesive strength of this example and the comparative example using Cr as the base are greater. This is thought to be because by using Cr as the base, it is firmly fixed to the core via the Cr oxide layer, and the Fe layer or the metal magnetic thin film is also firmly fixed via the Cr oxide layer. Furthermore, regarding the pseudo gap, it can be confirmed that almost no pseudo gap occurs in this example and in the comparative example using a Cr diffusion layer as the base, which is desirable. Regarding the reproduction output, it is desirable that the present example and the comparative example using a Cr substrate have a reproduction output of 250 mV or more, and among them, the present example is more desirable. Furthermore, regarding the bit shift, it can be seen that this embodiment is the smallest and desirable.

[0027]

[Table 1]

[0028]

[Effects of the Invention] According to the magnetic head of the present invention, since the Cr-rich layer and the Fe-rich layer are interposed between the joint surface of the core and the metal magnetic thin film, Cr is diffused into the Fe-rich layer. However, since the Fe-rich layer has magnetism, it does not create a pseudo gap, and the Cr-rich layer increases the bonding strength, and furthermore, Cr does not diffuse into the metal magnetic thin film to the extent that it deteriorates the magnetic properties. This results in a magnetic head with good recording and reproducing characteristics. Further, according to the method for manufacturing a magnetic head of the present invention, a Cr layer, an Fe layer,
Metal magnetic thin films are laminated in order, and Cr in the Cr layer is removed by heat treatment.
Since the Cr layer is diffused, the Cr layer does not remain as a pseudo gap, and is adhered to the core side as a Cr oxide layer with good bonding properties, making it possible to reliably produce a magnetic head with good recording and reproducing characteristics.

[Brief explanation of the drawing]

FIG. 1 is an overall perspective view of a magnetic head chip in a magnetic head of the present invention.

FIG. 2 is a partial perspective view of two examples of a portion of a magnetic head that faces a magnetic recording medium.

FIG. 3 is an enlarged photograph of the metal structure of the surface of the magnetic head facing the magnetic recording medium.

FIG. 4 is a compositional analysis diagram of a laminated portion on the surface of the magnetic head facing the magnetic recording medium.

FIG. 5 is an output waveform diagram of the magnetic head.

FIG. 6 is a measurement diagram showing a reproduction output of a magnetic head and a bit shift.

FIG. 7 is a perspective view of a conventional magnetic head.

FIG. 8 is a perspective view of a magnetic head chip in a conventional magnetic head.

FIG. 9 is a perspective view of a monolithic head in a magnetic head.

FIG. 10 is a waveform diagram showing an output waveform of a conventional magnetic head.

[Explanation of symbols]

5 I core 6 C core 8 Gap 11 Metal magnetic thin film 21 Cr-rich layer 22 Fe rich layer 23 Fe-Al-Si thin film

Claims (4)

[Claims] 1. A magnetic head in which a pair of ferrite cores are arranged facing each other through a magnetic gap, and a metal magnetic thin film is deposited on the opposing surface of at least one of the cores, the side to which the metal magnetic thin film is deposited. A composite magnetic head characterized in that a Cr-rich layer, an Fe-rich layer, and a metal magnetic thin film are laminated in this order on a surface of a ferrite core. [Claim 2] The thickness of the Cr-rich layer is 20 to 200 Å.
2. The composite magnetic head according to claim 1, wherein the Fe-rich layer has a thickness of 150 to 1500 Å. 3. The composite magnetic head according to claim 1, wherein the metal magnetic thin film is an Fe-Al-Si based magnetic thin film. [Claim 4] Cr is coated on the bonding surface of one of the pair of ferrite cores bonded by glass.
a step of forming an Fe layer by depositing the Cr layer on the surface of the Cr layer without contacting the reaction gas atmosphere; The method is characterized by comprising the steps of depositing the ferrite cores on the ferrite core to form a Fe-Al-Si thin film, a heat treatment step of diffusing Cr in the Cr layer into the Fe layer, and a step of bonding a pair of ferrite cores with glass. A method for manufacturing a composite magnetic head.