JPH11312302A - Magnetic head, method of manufacturing magnetic head, and magnetic recording / reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic head having a high saturation magnetic flux density and the like, a magnetic head with reduced deterioration of magnetic characteristics and improved corrosion resistance, a method of manufacturing the magnetic head, and a magnetic head using the magnetic head. Provided is a recording / reproducing device. SOLUTION: At least a magnetic gap is formed by abutting a pair of magnetic core halves 1 and a magnetic film is formed on the entire abutting surface of the pair of magnetic core halves 1 over the entire surface. In the head, a magnetic film is formed on the magnetic core half 1 with Fe as a main component and C, N, Ta, N
b, Zr, Mo, Ti, Cr, Si, Ru, Pd, P
The first magnetic film 3 includes an element containing at least one of t, Ga, and Au in an amount of 0.1 at% (atomic%) to 50 at%, and on the first magnetic film 3 And a second magnetic film 4 made of a material similar to that of the first magnetic film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic head, a method of manufacturing a magnetic head, and a magnetic recording / reproducing apparatus.
More specifically, the present invention relates to a magnetic head in which a pair of magnetic core halves having a magnetic film formed on both surfaces of a magnetic gap abutting surface are fused with glass, a method of manufacturing the magnetic head, and a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art With the remarkable progress of high density of magnetic recording technology in recent years, a magnetic head for recording and reproducing a medium having a high coercive force such as a metal tape has sufficient magnetic characteristics such as a high saturation magnetic flux density. Is required. As a material for the magnetic head for this purpose, a material having a higher saturation magnetic flux density for obtaining a sufficient recording magnetic field and having excellent soft magnetic properties is required.

In such a magnetic head, a magnetic gap is formed by abutting a pair of magnetic core halves, and a magnetic thin film is formed over the entire abutting surface of the pair of magnetic core halves. MIG (Metal In G
An ap) type magnetic head will be described as an example with reference to FIG. 5 which is a schematic perspective view of the magnetic head.

[0004] As shown in FIG.
Are the track width regulating groove 8 and the gap depth regulating groove 9
A pair of magnetic core halves 1 formed with are abutted to form a magnetic gap 14 and are integrally joined by fusion with glass 11.

In this case, Mn is used as one magnetic core half material.
Film 1 having a high saturation magnetic flux density using a ferromagnetic oxide composed of -Zn ferrite, Ni-Zn ferrite, or the like
Numerals 5 are formed on the abutting surfaces of the magnetic core halves 1 and over all surfaces. The magnetic film 15 has F
Since a microcrystalline metal magnetic thin film containing e as a main component has a high saturation magnetic flux density and excellent soft magnetic properties, it has been put to practical use as a substitute for a conventional metal magnetic material for a magnetic head. .

However, as the saturation magnetic flux density increases, the proportion of the Fe component increases, and accordingly, there arises a problem that the corrosion resistance decreases. As a countermeasure, a method of increasing the addition amount of an additional element for improving corrosion resistance is conceivable, but conversely, there is a limit because the saturation magnetic flux density is lowered.

In a use environment such as a VTR having the above-mentioned MIG type magnetic head 13, dew condensation due to high humidity in rainy weather and temperature difference between indoor and outdoor is unavoidable. Rust may occur. Magnetic film 15
When rust is generated, soft magnetic characteristics are significantly deteriorated, and sufficient recording / reproducing ability is not obtained. In a VTR, image quality is deteriorated. In a magnetic disk device such as a data recorder or a hard disk drive (HDD), There was a problem that the error rate was significantly reduced.

[0008]

SUMMARY OF THE INVENTION In view of the foregoing problems, the present invention provides a magnetic head and a magnetic head in which the deterioration of magnetic characteristics is reduced and the corrosion resistance is improved in a MIG type magnetic head or the like having a high saturation magnetic flux density. It is an object of the present invention to provide a method of manufacturing the same and a magnetic recording / reproducing apparatus using the magnetic head.

[0009]

According to the present invention, there is provided a magnetic head comprising:
At least a pair of magnetic core halves, a magnetic gap formed by abutting a pair of magnetic core halves, and a magnetic gap formed over the entire butting surface of the pair of magnetic core halves. In a magnetic head having a film, the magnetic film has a first magnetic film on a magnetic core half, and has a second magnetic film on the first magnetic film.

According to the method of manufacturing a magnetic head of the present invention, at least a pair of magnetic core halves are formed, and a pair of magnetic core halves are joined to form a magnetic gap. In a method of manufacturing a magnetic head in which a magnetic film is formed on the entire surface of any one of the surfaces, the step of forming a magnetic film includes forming a first magnetic film on a magnetic core half, A step of forming a second magnetic film on the one magnetic film.

In the magnetic head and the method of manufacturing a magnetic head according to the present invention, the first magnetic film and the second magnetic film are
Fe as a main component, C, N, Si, Ti, Cr, Ga,
Zr, Nb, Mo, Ru, Pd, Ta, Pt and Au
0.1a of an element containing at least one of
It is desirable to contain t% (atomic%) or more and 50 at% or less. The lower limit of the additive element other than Fe indicates the ratio of the lower limit of the addition effect, and the upper limit guarantees the lower limit of the magnetic properties such as the saturation magnetic flux density.

Preferably, the first magnetic film is a FeRuGaSi film, and the second magnetic film is a FeTaCrN film, and the composition ratio of the FeRuGaSi film is Fe _a R
u _b Ga _c Si when expressed as _d, the ratio a of each element,
b, c, d (at%) are 68 ≦ a ≦ 900.1 ≦ b ≦ 100.1 ≦ c ≦ 1510 ≦ d ≦ 25, and the composition ratio of the FeTaCrN film is Fe _e
Ta _f Cr _g N when expressed is _h, the proportion of each element e, f,
It is preferable that g and h (at%) satisfy the following condition: 71 ≦ e ≦ 856 ≦ f ≦ 150.5 ≦ g ≦ 109 ≦ h ≦ 16. (However, a + b + c + d =
100, and e + f + g + h = 100)

The thickness of the first magnetic film is preferably at least 0.05 μm, and the ratio of the first magnetic film to the thickness of the magnetic film is preferably at most 50%.

A magnetic recording / reproducing apparatus according to the present invention is characterized by mounting the magnetic head according to the first aspect.

The operation of the above means will be described below.
According to the magnetic head of the present invention, the magnetic film has a two-layer structure,
The first magnetic film having corrosion resistance can prevent the invasion of water due to dew condensation and the like, and can suppress the generation of rust on the second magnetic film. Therefore, a magnetic head having excellent corrosion resistance while satisfying a high saturation magnetic flux density can be obtained. can get. Further, according to the method of manufacturing a magnetic head of the present invention, the first magnetic film suppresses the generation of rust on the second magnetic film, and a magnetic head excellent in corrosion resistance while satisfying a high saturation magnetic flux density can be easily obtained. Can be manufactured. Further, a highly reliable magnetic recording / reproducing apparatus using this magnetic head can be provided.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a magnetic head to which the present invention is applied is described in which a magnetic gap is formed by abutting a pair of magnetic core halves, and any one of the abutting surfaces of the pair of magnetic core halves is formed. Also, referring to FIG. 5 which is a schematic perspective view of a magnetic head and FIG. 1 which is an enlarged view of a main portion in the vicinity of a magnetic gap of the magnetic head, taking a MIG type magnetic head in which a magnetic thin film is formed over the entire surface as an example. Will be explained. However, the same components as those in the conventional example are denoted by the same reference numerals.

As shown in FIG. 5, the MIG type magnetic head 13
Are formed integrally by abutting a pair of magnetic core halves 1 to form a magnetic gap 14 and fusing with the glass 11. A magnetic film 15 is formed over the entire butting surface of the magnetic core half 1.

The magnetic core half 1 is formed of a ferromagnetic oxide made of Mn-Zn ferrite, Ni-Zn ferrite or the like.

As shown in FIG. 1, a nonmagnetic reaction preventing film 2, a first magnetic film 3 and a second magnetic film 4 as a magnetic film 15 and a nonmagnetic The magnetic gap films 5 and 6 are stacked in this order.

The first magnetic film 3 and the second magnetic film 4 are
Fe as a main component, C, N, Si, Ti, Cr, Ga,
Zr, Nb, Mo, Ru, Pd, Ta, Pt and Au
0.1a of an element containing at least one of
It is formed of a soft magnetic material having a high saturation magnetic flux density containing t% or more and 50 at% or less. It is desirable that the first magnetic film 3 has a thickness of 0.05 μm or more and 50% or less of the total thickness of the magnetic film.

Each of the above films can be formed by a sputtering method such as DC sputtering or RF sputtering, or a vacuum film forming method such as a vacuum evaporation method or an ion plating method.

The above magnetic head 13 is provided with a winding (not shown) and connected to a terminal plate (not shown) and then mounted on a magnetic recording / reproducing apparatus such as a VTR or HDD.

FIG. 6 is a schematic perspective view of an HDD device as an example of a magnetic recording / reproducing device to which the magnetic head 13 of the present invention is applied. FIG. 6 is a schematic perspective view showing a main part of the HDD device by cutting out a part of the housing.

That is, the magnetic head device 18 is mounted on one end of the support arm 19 having elasticity.
The other end is provided with an actuator 20. The support arm 19 freely rotates about its support shaft, and can move the magnetic head device 18 to a desired position.
The hard disk 21 for recording information is rotated by a spindle motor (not shown), and performs electromagnetic conversion of an information signal with the magnetic head device 18.

As shown in FIG. 7, the magnetic head device 18 has a magnetic head 13 mounted on one end of a slider 22 made of, for example, an Al ₂ O ₃ —TiC-based nonmagnetic ceramic.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in more detail with reference to FIGS. 2 to 3 and FIGS. Note that the present invention is not limited to these examples.

As shown in FIG. 2A, first, Mn-Zn
A soft magnetic oxide substrate from which a magnetic core half block 7 which is a precursor of the magnetic core half 1 such as ferrite or Ni—Zn ferrite is obtained is, for example, 45 mm × 45 mm ×
It is formed so as to have a shape of 1 mm.

Next, as shown in FIG. 2B, a track width regulating groove 8 having a substantially U-shaped cross section is formed so that a track of a prescribed width is formed on the main surface of the magnetic core half block 7. Form. For example, assuming that the angle of contact with the main surface is 60 degrees, the width of the groove opening is 190 μm, the depth is 95 μm, and the track width is 16 μm.
It was formed in a substantially U-shape of μm. This shape may be a rectangle consisting of a vertical plane and a horizontal plane or a V-shape.

Next, as shown in FIG. 2C, a gap depth regulating groove 9 deeper than the track width regulating groove 8 in a direction perpendicular to the track width regulating groove 8 on the main surface side of the magnetic core half block 7. To form For example, the opening width is 650 μm, the depth is 200 μm, the angle in contact with the main surface on the track surface side is 40 degrees, and the angle in contact with the main surface on the opposite surface side to the track surface is 90 degrees. did. After this,
Polishing is performed on a portion of the main surface to be the track width, so that the surface roughness is about 5 nm.

Next, as shown in FIG.
A ferromagnetic oxide and a magnetic film 15 to be formed later
A reaction prevention film 2 of, eg, SiO _{2 is formed} to a thickness of, for example, 5 nm in order to suppress a reaction between the layers. Then, as the magnetic film 15, F
A first magnetic film 3 having e as a main component is formed, and then a second magnetic film 4 made of the same material as the first magnetic film 3 is formed. For example, 200 μm of FeRuGaSi is used as the first magnetic film 3.
m, a 3.8 μm thick FeTaCrN film as the second magnetic film 4.
m is formed. Then, Cr films 10 nm each are used as magnetic gap films 5 and 6 for forming magnetic gaps.
And an SiO ₂ film having a thickness of 80 nm.

The first magnetic film 3 and the second magnetic film 4 have a composition ratio of FeRuGaSi film of Fe _a Ru _b
When represented as Ga _c Si _d, the ratio a of the elements, b, c,
d ((at%) is 68 ≦ a ≦ 900.1 ≦ b ≦ 100.1 ≦ c ≦ 1510 ≦ d ≦ 25, and the composition ratio of the FeTaCrN film is Fe _e
Ta _f Cr _g N when expressed is _h, the proportion of each element e, f,
g and h (at%) can be in the range of 71 ≦ e ≦ 856 ≦ f ≦ 150.5 ≦ g ≦ 109 ≦ h ≦ 16. (However, a + b + c + d = 1
00, and e + f + g + h = 100)

An example of a method for forming each film is shown below.
You. FeRuGaSi film DC magnetron sputtering device Power density 5.0W / cm²  Ar gas pressure 0.5 Pa Distance between electrodes 60 mm

FeTaCrN film DC magnetron sputtering equipment Introduced gas Ar + N₂ Power density 5.0W / cm^Two  Ar + N_TwoGas pressure 0.5 Pa (N_TwoPartial pressure 20%) Distance between electrodes 60mm

Magnetic gap film (Cr, SiO_Two) RF sputtering equipment Power density 1.0W / cm^Two  Ar gas pressure 0.4 Pa Distance between electrodes 60 mm

Next, as shown in FIG. 3D, a pair of magnetic core half-blocks 7 are combined so that their track width portions overlap, and glass 11 is poured.
The magnetic core block 10 of the magnetic head 13 is completed.

Next, as shown in FIG. 3E, a winding guide groove 12 is formed in a portion where the winding outside the magnetic core block 10 is wrapped, and a portion serving as a sliding surface of the magnetic recording medium is formed. Was subjected to cylindrical grinding to form a curved surface, and then cut into head chips so that the azimuth angle was 10 degrees. In the figure, a dotted line indicates a cutting portion.

A schematic perspective view of the MIG type magnetic head manufactured in the above steps is similar to FIG.

Further, in the magnetic head 13 as described above, a winding (not shown) is formed in the winding guide groove 12, and both ends of the winding are connected to lands of a terminal plate (not shown), so that the magnetic head of a VTR, HDD or the like can be used. It is mounted on a magnetic head device of a recording / reproducing device.

Magnetic head characteristics (self-recording / reproducing mode) of the magnetic head 13 of the above embodiment were measured by a magnetic head characteristic measuring device. The first magnetic film 3 and the second magnetic film 4 are respectively formed by Fe ₆₃ Ru ₈ Ga ₁₀ Si ₁₉ films (a
%), the composition ratio of the Fe ₇₃ Ta ₁₀ Cr ₂ N ₁₅ film (at%), the total thickness is 4 μm, and the Fe ₆₃ Ru ₈ Ga ₁₀ S
was measured for reproduction output in a self-recording mode when varying the thickness of the i ₁₉ film, The results are shown in Table 1. In this case, the measured values in Table 1 are Fe ₆₃ Ru ₈ Ga ₁₀ Si ₁₉
This is a relative output when the measured value when the film thickness is 200 nm is 0 dB.

[0040]

[Table 1]

Next, the magnetic film 15 is made of Fe ₆₃ Ru ₈ Ga ₁₀ S
a magnetic head 13 having a laminated film of i ₁₉ film (200 nm) and Fe ₇₃ Ta ₁₀ Cr ₂ N ₁₅ film (3.8 μm);
A dew condensation test was performed on the magnetic head 13 using a single-layer film of Fe ₇₃ Ta ₁₀ Cr ₂ N ₁₅ film. Test Conditions The magnetic head 13 stored at 25 ° C. was left in a high temperature and high humidity atmosphere at 60 ° C. and 93% RH for 96 hours. This temperature difference causes dew condensation. The test was repeated five times using the same head with 100 samples each. After the test, the results of observing the occurrence of rust are shown in Table 2.

[0042]

[Table 2]

As a result of the above evaluation test, the magnetic head characteristics show that the magnetic head characteristics of the magnetic head having a Fe ₆₃ Ru ₈ Ga ₁₀ Si ₁₉ film thickness of 2 μm or less do not show a significant change but exceed 2 μm. Then, the magnetic head characteristics decrease. This is presumably because the number of Fe ₆₃ Ru ₈ Ga ₁₀ Si ₁₉ films whose soft magnetic properties were smaller than that of Fe ₇₃ Ta ₁₀ Cr ₂ N ₁₅ was increased, and the magnetic head properties were reduced. Therefore, Fe ₆₃ Ru ₈ Ga ₁₀ Si ₁₉ occupying in the magnetic thin film
It is understood that the ratio of the film thickness is desirably 50% or less.

Further, as apparent from the results of the condensation test,
And Fe₆₃Ru₈Ga_TenSi₁₉Film and Fe₇₃Ta_TenC
r_TwoN_FifteenThe magnetic head using the laminated film of the film is made of Fe₇₃Ta
_TenCr _TwoN_FifteenCompared to a magnetic head using a single layer film,
It can be seen that the durability against dew condensation is significantly improved.

The above reason will be described below with reference to FIG. 5 and FIG. 4 which is an enlarged view of a main part of the part A in FIG. The conventional MIG type magnetic head 13 is cut in a manufacturing process by a rotating grindstone or the like of a composite made of ferrite, a magnetic thin film, glass, and the like. It is inevitable that a part of the surface having the weakest bonding strength is peeled off. In this case, peeling occurs between the magnetic core half 1 of the ferromagnetic oxide and the magnetic film 15 as shown in part A of FIG. If moisture adheres to this part and dew condensation or the like occurs, moisture penetrates into the peeling part by capillary action, but hardly evaporates in an environment of normal temperature and normal humidity. For this reason, the magnetic film 15 is kept in contact with moisture for a long time, and the corrosion resistance of the magnetic film 15 is not sufficient.
In the magnetic head 13 of the mold type, rust is easily generated from that portion. Then, the magnetic film 15 expands due to the generation of rust, the peeling increases, the moisture penetrates further into the depth, and the rust also progresses to a deeper portion, so that the magnetic head characteristics are greatly deteriorated.

On the other hand, for example, between the magnetic core half 1 and the FeTaCrN film having excellent magnetic properties as the second magnetic film 4, the first magnetic film 3 having excellent corrosion resistance is made of FeR.
In the MIG-type magnetic head 13 of the present invention on which a uGaSi film is formed, as shown in FIG. 4, peeling 16 occurs between the magnetic core half 1 and the first magnetic film 3, and moisture enters into it. However, rust does not occur from the first magnetic film 3 having excellent corrosion resistance. The bonding force between the interface between the first magnetic film 3 and the second magnetic film 4 and between the glass 11 (including the magnetic gap films 5 and 6) and the interface between the second magnetic film 4 and the magnetic core half 1 First
Is stronger than the bonding force at the interface of the magnetic film 3 of FIG.
No gap is formed at both interfaces of the magnetic film 4 for moisture to enter, and the generation of rust due to dew condensation can be suppressed.

Therefore, by using the magnetic head 13 of this embodiment, it is possible to provide a highly reliable magnetic head having excellent magnetic properties such as saturation magnetic flux density and improved durability such as dew condensation. Further, if the magnetic head 13 is mounted on a magnetic head device of a magnetic recording / reproducing device such as a VTR or an HDD device, a magnetic recording / reproducing device having high reliability with respect to corrosion resistance and the like can be provided.

[0048]

According to the magnetic head of the present invention, it is possible to provide a highly reliable magnetic head having excellent magnetic properties such as saturation magnetic flux density and improved durability such as dew condensation. Further, according to the method of manufacturing a magnetic head of the present invention, a highly reliable magnetic head having excellent magnetic properties such as saturation magnetic flux density and improved durability such as dew condensation can be easily manufactured. By using the magnetic head device using the magnetic head of the present invention, it is possible to provide a highly reliable magnetic recording and reproducing device with improved durability due to dew condensation.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a main part of a magnetic head according to the present invention.

FIGS. 2A to 2C are schematic perspective views illustrating a method for manufacturing a magnetic head according to the present invention.

FIGS. 3D to 3E are schematic perspective views illustrating the method of manufacturing the magnetic head of the present invention, following FIG. 2C.

FIG. 4 is an enlarged view of a main part of a portion A of the magnetic head of the present invention.

FIG. 5 is a schematic perspective view of a conventional magnetic head.

FIG. 6 is a schematic perspective view of a magnetic recording / reproducing apparatus.

FIG. 7 is a schematic perspective view of a magnetic head device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Half magnetic core, 2 ... Reaction prevention film, 3 ... First magnetic film, 4 ... Second magnetic film, 5, 6 ... Magnetic gap film, 7 ...
Magnetic core half block, 8: track width regulating groove, 9: gap depth regulating groove, 10: magnetic core block, 11 ...
Glass, 12: winding guide groove, 13: magnetic head, 14
... magnetic gap, 15 ... magnetic film, 16 ... peeling, 17 ...
HDD device, 18 magnetic head device, 19 support arm, 20 actuator, 21 hard disk, 2
2 ... Slider

Claims (13)

[Claims] At least one of a pair of magnetic core halves, a magnetic gap formed by abutting the pair of magnetic core halves, and an abutting surface of the pair of magnetic core halves. Wherein the magnetic film has a first magnetic film on the magnetic core half and a second magnetic film on the first magnetic film. A magnetic head comprising: 2. The method according to claim 1, wherein the first magnetic film and the second magnetic film contain Fe as a main component, and include C, N, Si, Ti, Cr, and G.
an element containing at least one of a, Zr, Nb, Mo, Ru, Pd, Ta, Pt and Au.
2. The magnetic head according to claim 1, wherein the magnetic head contains 1 at% (atomic%) or more and 50 at% or less. 3. The magnetic head according to claim 1, wherein the first magnetic film is a FeRuGaSi film, and the second magnetic film is a FeTaCrN film. 4. The composition ratio of the FeRuGaSi film is F
When represented as _{e a Ru b Ga c Si d} , the ratio a of the elements, b, c, d (at %) is, 68 ≦ a ≦ 90 0.1 ≦ b ≦ 10 0.1 ≦ c ≦ 15 10 with a ≦ d ≦ 25, the composition ratio of the FeTaCrN film, Fe _e Ta _f Cr _g
When expressed as N _h , the ratio e, f, g, h (at
%): 71 ≦ e ≦ 856 ≦ f ≦ 150.5 ≦ g ≦ 109 ≦ h ≦ 16, The magnetic head according to claim 3, wherein:
(However, a + b + c + d = 100 and e + f +
g + h = 100) 5. The film thickness of the first magnetic film is 0.05 μm.
2. The magnetic head according to claim 1, wherein: 6. The magnetic head according to claim 1, wherein the ratio of the first magnetic film to the thickness of the magnetic film is 50% or less. 7. At least a pair of magnetic core halves are formed, a magnetic gap is formed by abutting the pair of magnetic core halves, and a magnetic gap is formed on any of the abutting surfaces of the pair of magnetic core halves. In a method of manufacturing a magnetic head in which a magnetic film is formed over the entire surface, the step of forming the magnetic film comprises forming a first magnetic film on the magnetic core half, and forming the first magnetic film A method for manufacturing a magnetic head, comprising a step of forming a second magnetic film thereon. 8. The first magnetic film and the second magnetic film have Fe as a main component and C, N, Si, Ti, Cr, G
an element containing at least one of a, Zr, Nb, Mo, Ru, Pd, Ta, Pt and Au.
8. The method according to claim 7, wherein the content is 1 at% or more and 50 at% or less. 9. The method according to claim 7, wherein the first magnetic film is a FeRuGaSi film, and the second magnetic film is a FeTaCrN film. 10. The composition ratio of the FeRuGaSi film is as follows:
Fe _a Ru _b when Ga represented as _c Si _d, the ratio a of the elements, b, c, d (at %) is, 68 ≦ a ≦ 90 0.1 ≦ b ≦ 10 0.1 ≦ c ≦ 15 10 with a ≦ d ≦ 25, the composition ratio of the FeTaCrN film, Fe _e Ta _f Cr _g
When expressed as N _h , the ratio e, f, g, h (at
%) Satisfies 71 ≦ e ≦ 856 ≦ f ≦ 150.5 ≦ g ≦ 109 ≦ h ≦ 16. The method of manufacturing a magnetic head according to claim 9, wherein: (However, a + b + c + d = 100 and e + f + g + h = 100) 11. The film thickness of the first magnetic film is 0.05 μm.
8. The method according to claim 7, wherein the value is not less than m. 12. The method according to claim 7, wherein the ratio of the first magnetic film to the thickness of the magnetic film is 50% or less. 13. A magnetic recording / reproducing apparatus equipped with the magnetic head according to claim 1.