JP2927285B1 - Magnetoresistive head - Google Patents

Abstract

An object of the present invention is to provide a magnetoresistive head having stable read characteristics and capable of being manufactured with a high yield in a current manufacturing process. SOLUTION: The magnetic shields 21 and 22 of the magnetoresistive head A have uniaxial magnetic anisotropy in the track width direction when assembled as a magnetic recording device, and have a saturation magnetic flux density and an anisotropic magnetic field. The magnetic anisotropy constant represented by
It is composed of a soft magnetic thin film of 50 J / m ³ or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetoresistive head, and more particularly to a magnetoresistive head having stable read characteristics and a high production yield.

[0002]

2. Description of the Related Art A thin-film magnetic head is a magnetic head manufactured by forming a fine magnetic circuit on a substrate using a thin-film forming technique and a photolithography technique, and then performing a machining process such as a cutting process or a polishing process. This is one of the main technologies indispensable for increasing the recording density of magnetic recording devices such as magnetic disk devices and magnetic tape devices in recent years. In particular, a magnetoresistive head using a magnetoresistive effect in which the resistance value of a magnetic film changes according to a magnetic field applied from the outside is a key device for promoting the recent miniaturization and large capacity of hard magnetic disk devices. .

[0003] Among the magnetoresistive heads, those utilizing the spin valve effect, in which the resistance change corresponds to the cosine between the magnetization directions of two adjacent magnetic layers, show a large resistance change with respect to a small signal magnetic field. , Is being actively developed.

FIG. 4 shows a general form of each magnetic layer in a magnetoresistive head utilizing the spin valve effect. A magnetization free layer 11 responding to the signal magnetic field and a magnetization fixed layer 12 whose magnetization is fixed in the signal magnetic field direction are located at the center,
Bias layers 13 and 13 for applying a bias magnetic field for stabilizing the magnetic domain of the magnetization free layer are formed adjacent to both sides thereof, and these magnetization free layer 11, magnetization fixed layer 12 and bias layers 13 and 13 This constitutes a resistance effect element.

Further, a pair of magnetic shields 121 and 122 are formed so as to sandwich these layers in order to cut magnetic flux leakage from adjacent recording data. Here, as a measure for fixing magnetization in the signal magnetic field direction in the magnetization fixed layer 12, an antiferromagnetic layer (not shown) is laminated on the magnetization fixed layer 10, and an exchange coupling magnetic field at the interface between both layers is used. This is commonly done.

In a magneto-resistance effect type head, a pair of magnetic shields 122 and 121 formed so as to sandwich the magneto-resistance effect element indirectly affect the bias state of the magnetization of the magneto-sensitive layer of the magneto-resistance effect element. It is known that a so-called mirror image bias effect exists. The magnetic shields 121 and 122 are made of a soft magnetic thin film and generally form a circulating magnetic domain structure having an easy axis of magnetization in the same direction as the track width direction of the magnetoresistive element. At this time, if the magnetic domain structure of the magnetic shield is not formed stably and varies for each individual head, the mirror image bias effect fluctuates. As a result,
There is a problem in that the read characteristics vary from head to head, which hinders an improvement in manufacturing yield. Especially,
This problem has been caused by the increase in the recording density of magnetic disk devices.
It is conceivable that the influence becomes larger as the read gap becomes thinner.

As described above, it is necessary to consider the contribution of the stress-induced anisotropy as a cause of the variation in the magnetic domain structure of the magnetic shields 121 and 122 for each individual head. In particular, in the above-described magnetoresistive head utilizing the spin valve effect, in order to increase the stability of the magnetization direction in the magnetization fixed layer 12, high temperature is applied in a magnetic field in the signal magnetic field direction during the manufacturing process or at the end of the manufacturing process. Heat treatment may be performed. This heat treatment is performed on the soft magnetic thin film forming the magnetic shields 121 and 122 in a magnetic field in a direction perpendicular to the original easy axis direction. Is also reduced. As a result, the influence of the stress-induced anisotropy on the magnetic domain structure of the magnetic shield becomes relatively large.

As an attempt to stably form a magnetic domain structure of a magnetic shield, Japanese Patent Application Laid-Open No. Hei 8-212521 discloses a technique of providing a magnetic shield with a magnetic domain control layer for stabilizing a magnetic domain. Specifically, a method is described in which an antiferromagnetic film or a hard magnetic film is formed on a magnetic shield to realize a single magnetic domain structure having a single magnetization direction.

As a method for obtaining the same effect, Japanese Patent Application Laid-Open No. Hei 7-169523 describes that the magnetic shield has a multilayer structure composed of a laminate of a soft magnetic film and a non-magnetic film.

[0010]

However, all of these methods require a significant change in the manufacturing process, which complicates the manufacturing process, and has a problem in terms of practicality.

The present invention has been made in view of the above problems, and has as its object to provide a magnetoresistive head having stable reading characteristics and capable of being manufactured with a high yield in the current manufacturing process.

[0012]

According to a first aspect of the present invention, there is provided a magnetoresistive head comprising: a magnetoresistive element for detecting a signal magnetic field from a magnetic recording medium by using a resistance change; A magnetoresistive head comprising a pair of magnetic shields sandwiching the magnetoresistive element with a read gap therebetween, wherein the magnetic shield is uniaxially magnetically anisotropic in the track width direction when assembled as a magnetic recording device. And a soft magnetic thin film having a magnetic anisotropy constant represented by a saturation magnetic flux density and an anisotropic magnetic field of 250 J / m ³ or more.

When considering the actual head manufacturing process, the stress-induced anisotropy is mainly determined by the magnetostriction constant of the soft magnetic film. Among them, it is necessary to precisely control the fluctuation factors such as film quality, heat treatment conditions, and mechanical polishing conditions for forming the head air bearing surface.
On the other hand, since the magnetostriction constant is greatly affected by the composition of the soft magnetic film, it is necessary to eliminate the composition variation between each deposition run or the composition variation in the wafer. Even if the influence of the stress-induced anisotropy varies to some extent for each individual head, it is a practical method to derive a condition under which the magnetic domain structure of the magnetic shield is not largely affected. The present invention has been found as a result of studying the conditions required for the magnetic properties of the soft magnetic thin film forming the magnetic shield from such a viewpoint.

In the case of a soft magnetic thin film pattern having a finite size like a magnetic shield, a state in which no magnetic charge is generated on the pattern end surface, that is, a circulating magnetic domain structure is generally formed so as to reduce the magnetostatic energy of the film. . At this time, when the film has uniaxial magnetic anisotropy, a magnetic domain structure having a magnetic domain width that minimizes the sum of magnetic anisotropic energy and domain wall energy is realized. Since both the magnetic anisotropy energy and the domain wall energy are represented by the magnetic anisotropy constant of the film, it is understood that the magnetic domain structure (magnetic domain width) in the magnetic shield can be controlled by the magnitude of the magnetic anisotropy constant of the film.

Here, the magnetic anisotropy constant of a film having uniaxial magnetic anisotropy is generally represented by the following equation (1).

Magnetic anisotropy constant = [saturation magnetic flux density of film × anisotropic magnetic field of film] / 2 (1) Actually, since the influence of stress-induced anisotropy cannot be ignored as described above, The magnitude of the magnetic anisotropy constant may change. Here, even if the influence of the stress-induced anisotropy varied to some extent for each individual head during the head manufacturing process, the conditions under which the magnetic domain structure of the magnetic shield did not change significantly were examined by computer simulation. The result is shown in FIG.

FIG. 2 shows the effect of a variation (± 50 J / m ³ ) of the stress-induced anisotropy that occurs during a normal manufacturing process on the magnetic domain structure using the magnetic anisotropy constant of the film as a parameter. 6 is a graph showing a result of an investigation using a variation rate of a magnetic domain width as an index. From FIG. 2, it is recognized that the fluctuation rate of the magnetic domain width sharply decreases as the magnetic anisotropy constant of the film increases, and the fluctuation rate can be suppressed to 10% or less in the range of 250 J / m ³ or more. Preferably, the magnetic anisotropy constant is 400 J / m ³
By doing so, the variation rate of the magnetic domain width can be suppressed to approximately 5%.

Therefore, according to the first aspect of the present invention, the magnetoresistive head has a stable magnetic domain structure and can be manufactured in the same manufacturing process as the conventional one. A magnetoresistive head having read characteristics can be provided.

According to a second aspect of the invention, there is provided a magnetoresistive head.
The magnetoresistive element includes a central magneto-sensitive area formed of a spin valve element, and an end area adjacent to the central magneto-sensitive area for supplying a bias magnetic field and a sense current.

According to the invention having such a configuration, more stable read characteristics can be obtained, and it is possible to contribute to improvement in manufacturing yield.

According to a third aspect of the invention, there is provided a magnetoresistive head.
The soft magnetic thin film forming the magnetic shield is made of an amorphous material containing Co as a main component. According to the invention having such a configuration, it is possible to set the magnetic anisotropy constant of the magnetic shield within the above-described range.

According to a fourth aspect of the invention, there is provided a magnetoresistive head.
The soft magnetic thin film constituting the magnetic shield is made of Ni, F
The structure is made of an alloy material containing at least two kinds of metals selected from e and Co. According to the invention having such a configuration, it is possible to set the magnetic anisotropy constant of the magnetic shield within the above-described range.

According to a fifth aspect of the invention, there is provided a magnetoresistive head.
One or both of the pair of magnetic shields is composed of a plurality of soft magnetic thin films. According to the invention having such a configuration, the magnetic anisotropy of the magnetic shield can be set in the above-described range.

According to a sixth aspect of the invention, there is provided a magnetoresistive head.
One of the magnetic shields has a structure that also serves as one of magnetic pole films of an inductive head for writing a magnetic signal on a magnetic recording medium. According to the invention having such a configuration, it is possible to provide a composite head of the inductive head for recording and the magnetoresistive head for reproduction.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetoresistive head according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a magnetic head according to the present invention, and is a sectional view taken along a plane parallel to the surface of a magnetic recording medium when assembled as a magnetic disk drive.

This magnetic head is a composite magnetic head including a magnetoresistive head A for reproduction and an inductive head B for recording. This magnetic head is formed on a substrate 1 made of, for example, Al2O3-TiC, and is entirely protected by an overcoat layer 2 of alumina or the like. The magnetoresistive head A includes a magnetoresistive element 10 for detecting a signal magnetic field from a magnetic recording medium using a change in resistance, and a read gap 3
A first magnetic shield 21 and a second magnetic shield 22 sandwiched between the first and second magnetic shields 21 and 32;
0, the read gap 32, and the second magnetic shield 22 are stacked on the substrate 1 in this order.

In the inductive head B, the second magnetic shield 21 of the magnetoresistive head A also serves as a write magnetic pole, and the write magnetic pole (second magnetic shield) 21, the write gap 33, and the coil (shown in FIG. ), A coil insulating portion (not shown), and a write magnetic pole 41 in this order.

The first magnetic shield 21 and the second magnetic shield 22 are for absorbing extra magnetic flux from the recording medium so that the reproduced signal does not include noise. isotropic constant 250 J / m ³ or more, preferably 400 J / m ³ or more. As a material having such a magnetic anisotropy constant, an amorphous material containing Co as a main component or an alloy material containing two or more kinds of metals selected from Ni, Fe, and Co can be selected. .

Specifically, Co-Zr-Ta, Co-N
i-Fe, Ni-Fe and the like can be mentioned. The film is preferably formed to a thickness of 0.5 to several μm by, for example, a sputtering method, a vacuum evaporation method, a frame plating method, or the like. In addition, both or one of the first magnetic shield 21 and the second magnetic shield 22 can be formed of two or more composite layers. FIG. 3 shows a composite magnetic head suitable for high-density recording in which a soft magnetic thin film having high saturation magnetic flux density characteristics is arranged so as to sandwich the write gap 33. For example, the second magnetic shield 22 is formed of Ni-Fe from the substrate side. Layer 2
2a, a Co—Ni—Fe layer 22b,
1 can be a Co—Ni—Fe layer 41a and a Ni—Fe layer 41b.

The read gaps 31, 32 and the write gap 33 can be made of a non-magnetic material such as alumina.

Further, the magnetoresistive element 10 is arranged perpendicularly to the recording medium and detects a perpendicular component of a magnetic flux from the recording medium. The magnetoresistive element 10 and the magnetization fixed layer 12 shown in FIG. And a center magnetically sensitive region 13 composed of a spin valve element having the following, and end regions 14 and 14 for supplying a bias magnetic field and a sense current adjacent to both sides thereof.

In this structure, when an external magnetic field is applied,
Since the magnetization direction of the magnetization free layer 11 is freely rotated in accordance with the direction of the external magnetization, an angle difference occurs between the magnetization direction of the magnetization fixed layer 12 and the magnetization direction. Depending on the angle difference, the spin-dependent scattering of conduction electrons changes, and the electric resistance value changes. By detecting the change in the electric resistance value, the signal magnetic field from the magnetic recording medium is detected.

In such a magnetic head, the magnetic domain structure of the magnetic shield has a small variation and is stable. Therefore, the magnetic head has a small influence on the bias state of the magnetization of the magnetosensitive layer of the magnetoresistive element, and has a stable readout characteristic. Good production yield.

Next, an example of actually manufacturing the magnetic head shown in FIG. 1 will be described with reference to an embodiment and a comparative example. [Embodiment 1] First, a method of manufacturing a magnetoresistive head for reproduction utilizing the spin valve effect will be described.

An Al 2 O 3 —TiC substrate 1 was used as a substrate to be processed into a slider shape in the final step, and a 1 μm-thick Co—Zr—Ta film was formed thereon by sputtering. Thereafter, heat treatment was performed at 350 ° C. for 1 hour while applying a static magnetic field in the track width direction when the magnetic recording device was assembled as an initial heat treatment. The film was patterned to form a first magnetic shield 21. Next, an Al2O3 film having a thickness of 0.06 .mu.m to be a read gap 31 was formed by a sputtering method.

Subsequently, Ni—Fe, Cu, Co—Fe, and Ni—Mn as an antiferromagnetic material for fixing the magnetization direction of the magnetization fixed layer from the substrate side by a sputtering method.
In this order to form a spin valve laminate forming the central magnetosensitive region 13. The film thicknesses are 8 nm and 2.5 nm, respectively.
nm, 4 nm, and 30 nm. After this film formation, heat treatment is performed at 270 ° C. for 10 hours in a static magnetic field in a direction orthogonal to the time of the initial heat treatment of the first magnetic shield 21 in order to fix the magnetization direction in the magnetization fixed layer (see FIG. 4). Was.
Next, the spin valve element is set to 1 μm equivalent to the reproduction track width.
The central magnetic sensing region 13 was formed by patterning to a width.

Further, as the end region 14, a 20 nm thick Co for applying a bias magnetic field to the central magnetosensitive region 13 is used.
A Cr-Pt film and 150 for supplying a sense current.
After forming an Au film having a thickness of nm by a sputtering method,
The end region 14 was formed by processing into a predetermined shape.

Next, 0.0, which is the read gap 32, is used.
An Al2O3 film having a thickness of 9 μm was formed by a sputtering method. After that, a 2 μm-thick Co—Zr—Ta film serving as the second magnetic shield 22 is formed by a sputtering method.
After performing a heat treatment at 200 ° C. for one hour in a static magnetic field in the same direction as the initial heat treatment of the first magnetic shield 21,
The second magnetic shield 22 was formed by patterning into a predetermined shape.

Subsequently, an inductive type write element portion was formed, and a 0.3 μm thick Al 2 O 3 film was formed by a sputtering method to form a write gap 33.

Next, a magnetic field generating coil (not shown) of the write element section was formed. Specifically, a structure in which the Cu coil portion is embedded in the hard cure photoresist in the order of the coil insulation portion made of the hard cure photoresist, the Cu coil portion formed by the frame plating method, and the coil insulation portion made of the hard cure photoresist is described. Formed. Here, 260 ° C. for hard curing of the photoresist,
Heat treatment was performed for one hour. Subsequently, a Ni—Fe film to be the write pole film 41 was formed by frame plating.

Finally, Al 2 O 3 is applied so as to cover the whole.
An overcoat layer 2 made of a film was formed.

Incidentally, the magnetization direction of the magnetization fixed layer of the spin valve element may be disturbed by being subjected to various heat treatments during the step of forming the writing element after being fixed once immediately after the film formation. In order to rearrange the disturbance of the magnetization direction in the magnetization fixed layer 12, a heat treatment at 200 ° C. for one hour was performed in a static magnetic field in a direction perpendicular to the track width direction when assembled as a magnetic recording device. This was performed after the completion of the wafer process.

After completing the above-described wafer process, through a predetermined mechanical polishing step and a head assembling step, the fabrication of a composite type head including the magnetoresistive head A shown in FIG. 1 was completed.

According to the results of measurement of the magnetic properties of the obtained magnetic head monitor sample, the anisotropic magnetic field of the first magnetic shield 21 and the second magnetic shield 22 after these series of heat treatments was both 8 Oe. The saturation magnetic flux density was 1.5 T in each case. From these results, the magnetic anisotropy constants of the corresponding films were both 480 J / m ³ .

The stability of the readout characteristics of the magnetoresistive head thus manufactured was examined. As an index of stability of read characteristics, 1000 write /
The read operation was repeated, and each time, the symmetry of the read waveform was evaluated, and the rate of change with respect to the average value was examined. Here, the symmetry of the waveform is defined by the following equation (2) when the magnitude of the upper peak is Vp and the magnitude of the lower peak is VN.

(Vp−VN) / (Vp + VN) × 100% (2) As a result of extracting heads from different positions in the wafer or from different wafers and examining the stability of readout characteristics using the above index, it was found that all heads , The symmetry variation rate is 5
%, And a high production yield was obtained.

Example 2 A magnetoresistive head was manufactured in exactly the same steps as in Example 1 except that a Co—Ni—Fe film formed by frame plating was used for the second magnetic shield 22.

The anisotropic magnetic fields of the first magnetic shield 21 and the second magnetic shield 22 after a series of heat treatments are 80
e and 6 Oe. The saturation magnetic flux densities were 1.5T and 2T, respectively. From these results, the magnetic anisotropy constants of the corresponding films were both 480 J / m ³ .

With the magnetoresistive head manufactured in this manner, it was found that a magnetoresistive head with stable read characteristics and a high production yield was obtained as in the first embodiment.

[Embodiment 3] Ni-Fe / Co-Ni- formed on the second magnetic shield 22 by frame plating.
An Fe film was used. As shown in FIG. 3, the order of film formation was as follows: a Ni—Fe film 22a and a Co—Ni—Fe film 22b from the substrate side. The film thickness was 1 μm. Also, the write pole 41
Co-Ni-Fe /
A Ni—Fe film was used. As shown in FIG. 3, the order of film formation is such that the Co—Ni—Fe film 41a, the Ni—Fe film
1b. Except for this, the magnetoresistive head shown in FIG. 3 was manufactured in exactly the same steps as in Example 1. In addition,
3, the same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The anisotropic magnetic fields of the first magnetic shield 21 and the second magnetic shield 22 after a series of heat treatments are 80
e, 4Oe. The saturation magnetic flux density was 1.5 T in each case. From this result, the magnetic anisotropy constant of the corresponding film, were respectively ^{480J / m 3, 250J / m} 3.

With the magnetoresistive head manufactured in this manner, it was found that a magnetoresistive head having stable read characteristics and a high production yield was obtained as in the first embodiment.

Comparative Example 1 For the first magnetic shield 21 and the second magnetic shield 22, a Ni—Fe film formed by frame plating was used. The heat treatment temperature of the second magnetic shield 22 was 200 ° C. Otherwise, a magnetoresistive head was manufactured in exactly the same steps as in Example 1.

The anisotropic magnetic fields of the first magnetic shield 21 and the second magnetic shield 22 after a series of heat treatments are 1.5
Oe and 2 Oe. Further, the saturation magnetic flux density was 1T in each case. From these results, the magnetic anisotropy constants of the corresponding films were 60 J / m ³ and 80 J / m ³ , respectively.

With respect to the magnetoresistive head manufactured as described above, the head was extracted from a different position in the wafer or from a different wafer, and the stability of the read characteristics was examined. It was found that the variation was as large as about 30%, and as a result, the manufacturing yield was reduced.

[Comparative Example 2] An Fe-Ta-N film formed by reactive sputtering on the first magnetic shield 21 and a Ni-Fe film formed by frame plating on the second magnetic shield 22 were used. The heat treatment temperature of the first magnetic shield 21 was set to 500 ° C. Otherwise, a magnetoresistive head was manufactured in exactly the same steps as in Example 1.

The anisotropic magnetic fields of the first magnetic shield 21 and the second magnetic shield 22 after a series of heat treatments were both 2 Oe. The saturation magnetic flux densities are 1.6T and 1T, respectively.
Met. From this result, the magnetic anisotropy constant of the corresponding film, were respectively ^{130J / m 3, 80J / m} 3.

With respect to the magnetoresistive head manufactured as described above, the head was extracted from a different position in the wafer or from a different wafer, and the stability of the read characteristics was examined. It was found that the variation was as large as about 30%, and as a result, the manufacturing yield was reduced.

From the results of the above-described Examples and Comparative Examples, by setting the magnetic anisotropy constant of the magnetic shield to 250 J / m ³ or more, it is possible to obtain a magnetoresistive head having stable read characteristics and a high production yield. It is recognized that
This is because the variation rate of the magnetic domain width due to the variation of the stress-induced anisotropy for each individual head can be maintained at a small variation rate of 10% or less as shown in FIG. It is considered that the fluctuation of the mirror image bias effect that occurred was reduced.

The antiferromagnetic material for fixing the magnetization direction of the magnetization fixed layer is not limited to Ni-Mn, but Mn-X (X is C
r, at least one element selected from Fe, Ni, Pd, Ir, Ru, Pt, and Rh). Further, an oxide antiferromagnetic material such as Ni-O may be used.

In the above-described embodiment, a composite head of a reproducing head and a recording head is used. However, the reproducing head and the recording head may be composed only of a resistance effect type head for reproduction.

[0062]

As described above, according to the magnetoresistive head of the present invention, the variation in the magnetic domain structure of the magnetic shield can be suppressed to a minimum without changing the manufacturing process, so that the manufacturing yield is high. At the same time, the read characteristics are stable, and reproduction with good reproducibility can be performed.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a composite magnetic head including a magnetoresistive head for reproduction and an inductive head for recording according to the present invention, on a surface of a magnetic recording medium when assembled as a magnetic disk. It is sectional drawing at the time of cutting by a parallel surface.

FIG. 2 is a graph showing a relationship between a magnetic anisotropy constant of a soft magnetic thin film constituting a magnetic shield and a variation rate of a magnetic domain width.

FIG. 3 shows a magnetic head formed in Example 3.
FIG. 3 is a cross-sectional view when cut along a plane parallel to the surface of the magnetic recording medium when assembled as a magnetic disk.

FIG. 4 is a conceptual diagram showing a general form of each magnetic layer of a magnetoresistive head using a spin valve effect.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Overcoat layer 10 Magnetoresistive element 13 Central magneto-sensitive area 14 End area 21 First magnetic shield 22 Second magnetic shield 31, 32 Read gap 33 Write gap 41 Write pole A Reproducing head B Recording head

Claims (6)

(57) [Claims] 1. A magnetoresistive element comprising: a magnetoresistive element for detecting a signal magnetic field from a magnetic recording medium using a change in resistance; and a pair of magnetic shields sandwiching the magnetoresistive element via a read gap. In the head, the magnetic shield has uniaxial magnetic anisotropy in a track width direction when assembled as a magnetic recording device, and has a magnetic anisotropy constant represented by a saturation magnetic flux density and an anisotropic magnetic field. A magnetoresistive head comprising a soft magnetic thin film having a thickness of 250 J / m ³ or more. 2. The magneto-resistance effect element comprises a central magneto-sensitive area comprising a spin valve element, and an end area adjacent to the central magneto-sensitive area for supplying a bias magnetic field and a sense current. The magnetoresistive head according to claim 1. 3. The magnetoresistive head according to claim 1, wherein the soft magnetic thin film forming the magnetic shield is made of an amorphous material containing Co as a main component. 4. The soft magnetic thin film forming the magnetic shield is made of at least two of a metal selected from Ni, Fe, and Co.
3. The magnetoresistive head according to claim 1, wherein the magnetoresistive head is made of an alloy material containing a seed as a main component. 5. The magnetoresistive head according to claim 1, wherein one or both of said pair of magnetic shields is formed of a plurality of soft magnetic thin films. 6. The magnetic shield according to claim 1, wherein one of said magnetic shields has a structure also serving as one of magnetic pole films of an inductive head for writing a magnetic signal on a magnetic recording medium. Magnetoresistive head.