JPH10149514A - Magneto-resistance effect type magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an output signal having good vertical symmetry in waveform even in a narrower track by making a dimension of a magneto- resistance effect(MR) film in its heightwise direction larger than a width of a track and impressing a lateral bias magnetic field upon the MR film by a permanent magnet film disposed in both end parts of the MR film in the widthwise direction of the track. SOLUTION: The MR film 1 is formed in its heightwise direction aligned with an axis of easy magnetization to be longer than the track width. The permanent magnet film 2 is disposed on both sides of the MR film in the direction of the track width, and magnetization 4 of the MR film 1 in its heightwise direction is inclined by the permanent magnet film 2. An electrode 3 is disposed on the permanent magnet film 2 for the purpose of supplying a sense electric current to the MR film 1. By such an MR element composed of the above structure, a magnetic signal can be read out of a recording medium 9. In this constitution, a required bias for a linear response can be impressed enough even on a narrower track.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistance effect type magnetic head for reading a magnetic signal from a recording medium, and more particularly to a lateral bias type MR having high sensitivity characteristics.
Related to element.

[0002]

2. Description of the Related Art A magnetoresistance effect type magnetic head (hereinafter referred to as MR)
Head) is conventionally known as a magnetic head capable of reading a magnetic signal recorded on a recording medium at high density. This head is widely used as a read-only head of a recording / re-separation type magnetic head that uses dedicated heads for recording and reproduction.

[0003] This head records by utilizing the fact that the electric resistance of a magnetoresistive film (hereinafter referred to as MR film) made of a material exhibiting a magnetoresistive effect changes as a function of the strength and direction of an external magnetic field. It detects a magnetic signal from a medium. MR heads using various detection methods have been developed, and these have been conventionally used to satisfy the requirements of recording / reproducing devices.

In order for the MR film to operate optimally, two types of bias magnetic fields having different directions must be applied. One is a lateral bias magnetic field applied to tilt the magnetization of the MR film so that the response to an external magnetic field has a linearity. When the angle (bias angle) between the sense current and the magnetization of the MR film is about 45 °, the output signal of the MR head has the maximum output amplitude and the best vertical symmetry of the waveform.

Another bias magnetic field is a longitudinal bias magnetic field for suppressing Barkhausen noise caused by a multi-domain structure in the MR film. The MR film is a thin film having a weak anisotropic magnetic field, an unstable magnetic domain structure, and a multi-domain structure. In order to stabilize the magnetic domain structure of the MR film, MR
A longitudinal bias magnetic field is applied in the easy axis direction of the MR film so as to increase the anisotropic magnetic field of the film. Instead of applying a longitudinal bias magnetic field, even if the dimension in the easy axis direction is made larger than other dimensions so as to strengthen the shape anisotropic magnetic field of the MR film, M
The multi-domain of the R film is suppressed.

As means for applying a lateral bias magnetic field, Japanese Unexamined Patent Publication No. Sho 52-062417 discloses SA as shown in FIG.
An MR head using the L bias method is disclosed. S
The AL bias method is the most commonly used bias method. In FIG. 6, a lateral bias magnetic field is applied to the MR film 1 using the saturation magnetization of the SAL film 22 disposed on the MR film 1 via the non-magnetic film 21 to incline the magnetization 4 of the MR film 1. Further, the permanent magnet film 2 adjacent to the MR film 1
Thus, a longitudinal bias magnetic field is applied in the easy axis direction of the MR film 1 to stabilize the magnetic domain structure of the MR film. The electrode 3 is means for supplying a sense current to the MR film via the permanent magnet film 2. With such a structure, a magnetic signal from the recording medium 9 is read by the MR film 1.

On the other hand, Japanese Patent Laying-Open No. 52-100217 discloses an MR head using a permanent magnet bias method as shown in FIG. In FIG. 7, the M
A lateral bias magnetic field is applied using the magnet magnetic field of the permanent magnet film 2 laminated on the R film 1 to incline the magnetization 4 of the MR film 1. Further, a longitudinal bias magnetic field is applied from the permanent magnet film 2 adjacent to the MR film 1 in the easy axis direction of the MR film 1 to stabilize the magnetic domain structure of the MR film.

[0008] A higher recording density is required for the recording / reproducing apparatus, and the track width is becoming narrower. But,
The conventional bias method shown in the elevation view of the conventional SAL bias method MR element in FIG. 6 and the elevation view of the conventional permanent magnet bias MR element in FIG. 7 makes it difficult to obtain an MR head having a narrower track width. ing.

[0009]

The problems of the conventional bias method will be described below. The SAL bias method shown in FIG. 6 is a method in which the magnetization of the SAL film is saturated by a sense current, and a bias magnetic field is applied to the MR film by a leakage magnetic field from the SAL film. For this reason, the bias angle changes depending on the magnitude of the sense current. The bias angle is an angle between the sense current and the magnetization of the MR film. Therefore, the vertical symmetry of the output varies depending on the magnitude of the sense current.

However, when the height of the MR film decreases with an increase in the recording density, the demagnetizing field in the height direction of the MR film increases, and it is necessary to flow a larger sense current for applying a sufficient lateral bias magnetic field. On the other hand, when a larger sense current is passed, the element temperature of the MR element rises due to Joule heat and M
The rate of change in resistance of the R film decreases, and the output signal of the MR head also decreases. For the above reasons, at high recording densities, SA
It becomes difficult to apply a bias magnetic field required for linear response using the L bias method.

On the other hand, to suppress the temperature rise, 2 × 10 ⁷ A
When a sense current of about / cm ² flows, the bias magnetic field becomes insufficient as the track width becomes narrower, and the output signal decreases. The output signal of the MR head is required not only to have a large amplitude but also to have good vertical symmetry.
If the bias angle deviates from 45 °, the response of the MR head to the magnetic field of the recording medium becomes non-linear, the amplitude corresponding to one of the positive and negative signals becomes larger than the other, and the vertical symmetry deteriorates. In order to process the signal as a signal in an amplification process by an electric circuit after the detection of the output signal of the MR head, the difference between the positive and negative amplitudes needs to be within about 20% of the average amplitude. However, to suppress the temperature rise, 2 × 1
In passing the 0 ⁷ A / cm ² about the sense current, the bias magnetic field larger the track width is narrowed becomes insufficient, vertical symmetry is deteriorated.

Another bias method disclosed in the prior art is as follows. As shown in FIG.
This is a permanent magnet bias method in which a lateral bias magnetic field is applied using the magnet magnetic field of the permanent magnet film 2 laminated on the substrate. Even if the track is narrowed, there is an advantage that there is no problem of a rise in element temperature due to Joule heat as in the SAL bias method described above.

However, the conventional permanent magnet bias method is SA
There is a problem that the output signal is small as compared with the L bias method. In FIG. 7, the film is formed such that the easy axis of the MR film 1 is oriented substantially in the track width direction and the easy axis of the permanent magnet film is oriented substantially in the height direction of the MR film. Therefore, the magnetization 4 of the MR film in the vicinity of the air bearing surface where the magnetic field of the recording medium is largest is strongly fixed by the permanent magnet film 2, and the output signal becomes smaller than in the SAL bias method.

Therefore, according to the present invention, even if the track is narrowed, a bias magnetic field necessary for a linear response can be sufficiently applied.
An object of the present invention is to provide an MR head capable of obtaining an output signal having good vertical symmetry of an output signal waveform.

[0015]

An MR head according to the present invention comprises:
By making the dimension of the MR film in the height direction larger than the track width, M
A lateral bias magnetic field is applied to the MR film by permanent magnet films disposed at both ends in the track width direction of the R film.

Further, in the MR head of the present invention, the easy axis of the MR film is substantially in the height direction of the MR film, and the easy axis of the permanent magnet film is substantially in the track width direction.
A lateral bias magnetic field is applied to the R film.

Further, the MR head of the present invention is characterized in that an antiferromagnetic film is disposed on the entire surface or a part of the MR film, thereby applying a lateral bias magnetic field while stabilizing the magnetic domain structure of the MR film. And

Further, the MR head according to the present invention is characterized in that by setting the height of the MR film higher than the height of the electrodes, an output signal having a stable magnetic domain structure and good vertical symmetry of the waveform can be obtained.

The operation of the present invention will be described below. In the permanent magnet bias method according to the present invention, by arranging permanent magnet films at both ends in the track width direction of the MR film and applying a lateral bias magnetic field, it is easy to rotate the magnetization near the air bearing surface of the MR film, An output signal having a larger amplitude than that of the conventional permanent magnet bias method can be obtained.

The magnetic domain structure of the MR film becomes more stable as the dimension in the easy axis direction (here, the height of the MR film 7) is larger than the other dimensions (here, the track width 6 and the film thickness). On the other hand, the magnetic field of the recording medium rapidly attenuates in the height direction of the MR film.
A higher output signal voltage is obtained when the MR film height (here, the electrode height 8) in the region where the resistance change of the MR film 1 is detected as a difference between the output signal voltages is smaller. Accordingly, when the MR film height 7 is higher than the electrode height 8 as shown in FIG. 1, an MR head having a stable magnetic domain structure and a high output signal can be obtained.

Therefore, in the present invention, when the MR film height 7 is made sufficiently larger than the track width 6 as shown in FIG.
The magnetic domain structure is stabilized, and a longitudinal bias magnetic field for stabilizing the magnetic domain structure is unnecessary.

The characteristics of the permanent magnet bias method according to the present invention and the characteristics of the conventional SAL bias method are compared below.

FIG. 3 shows a simulation result of a bias angle when the track width Tw is changed for the bias method using the permanent magnet film according to the present invention and the conventional SAL bias method. Here, the electrode height was calculated as 60% of each track width. A desirable bias angle for a linear response is on the order of 45 ° as shown in the gray area in the figure.

The conventional SAL bias method is indicated by a circle. S
Depending on the conditions such as the saturation magnetization of the AL film, the demagnetizing field in the direction of the MR film sharply increases when the MR film height is about 1.0 μm or less, and the sense current flowing to apply the bias magnetic field necessary for linear response is also large. It will increase rapidly. For example, 10GB /
in ² equivalent (Track width 0.5 μm, MR film height 0.3
In order to apply the necessary bias magnetic field to the MR film of μm), a sense current of about 2 × 10 ⁸ A / cm ² has to flow in the SAL bias method.

When the sense current flowing to the MR head is increased, the element temperature rises due to Joule heat, the rate of change in resistance of the MR film decreases, and the output signal of the MR head also decreases in proportion to the rate of change in resistance. There is a problem. Joule heat is proportional to the square of the sense current density. Generally, the upper limit of the sense current is 2 × 10 ⁷ A / cm ² , preferably 1 × 10 ⁷ A / c in order to suppress the temperature rise to about 15 degrees Celsius or less.
m ² . Therefore, 1
When a necessary bias is applied to an MR film equivalent to 0 GB / in ² , in addition to a decrease in an output signal due to heat generation, a fusion of the MR element is caused by a temperature rise of about 1000 degrees Celsius.

On the other hand, to suppress the temperature rise, 2 × 10 ⁷ A
/ Cm ^{2, the} lateral bias magnetic field becomes insufficient as the track width becomes narrower, and 10 GB / cm ²
In the case of in ² , a bias can be applied only about 10 °.

On the other hand, the present invention indicated by the mark
The required bias magnetic field can be applied to the MR film corresponding to / in ² . The present invention is a method in which a lateral bias is applied by a magnetic field generated by a permanent magnet film. As is apparent from FIG. 3, the bias angle does not depend on the magnitude of the sense current. Therefore, in the SAL bias method, the vertical symmetry of the output signal waveform fluctuates depending on the magnitude of the sense current, but the present invention has an advantage that the vertical symmetry does not depend on the sense current.

In the SAL bias method, Joule heat is radiated mainly only in the film thickness direction. On the other hand, in the present invention, since the MR film of the MR film is large, heat can also be radiated in the MR film height direction. For this reason, even when used at a high sense current density of 5 × 10 ⁷ A / cm ² , the temperature rise of the device was suppressed to a little less than 15 degrees Celsius.

However, in the present invention, as the track width increases, the leakage magnetic field due to the magnet film near the center of the MR film decreases.
The magnetization of the MR film tends to be oriented in the height direction of the MR film, which is the axis of easy magnetization. FIG. 3 shows this tendency when the track width is 4 μm or more. Therefore, in order to obtain a desired bias angle for a linear response in the head according to the present invention, it is desirable to use the head in a region having a narrow track width (2 μm or less in FIG. 3).

In the structure of the present invention, when an antiferromagnetic film is laminated on a part of the MR film as shown in FIG. 2, a desirable bias angle for a linear response was obtained irrespective of the track width and the sense current density. This is because a lateral bias magnetic field was applied by the exchange interaction between the antiferromagnetic film and the MR film in addition to the magnetic field generated by the permanent magnet film.

FIG. 4 shows the track width Tw dependency of the amplitude of the reproduction output signal by the conventional SAL bias method and the MR head of the embodiment according to the present invention. Here, the sense current is 5 × 10 ⁷ A / cm ^{2 for} the conventional method and the method of the present invention, respectively.
× 10 ⁷ A / cm ² .

In both methods, the output signal is approximately proportional to the track width. Except for the case where the track width is 4 μm, the output signal of the present invention is larger than that of the conventional example. In the conventional example, the output signal sharply decreased when the track width was less than 2 μm.

The output signal is proportional to the sense current flowing in the MR film showing a change in magnetoresistance. In the present invention, since a bias can be applied with a single layer of the MR film, the efficiency does not decrease due to the shunting of the sense current (to the SAL film and the non-magnetic film) as in the SAL bias method, and the sensitivity is high. Head can be realized. Further, in the present invention, since the height of the MR film is high, the heat dissipation is good, and the temperature rise can be suppressed to the same degree even when the MR film is used at a high sense current density 2.5 times that of the SAL bias method. Further, the output signal of the MR head has a bias angle of 4
The output signal amplitude becomes maximum when the track width is about 5 °, but in the conventional example, when the track width is reduced to 0.5 μm, only a bias of about 10 ° can be applied. From these three points, the output signal of the present invention is larger than that of the conventional SAL bias method.

In Example 1 using only the permanent magnet film, the output signal was reduced when the track width was 3 μm or more, as shown in FIG. 3, because the bias was applied too much when the track width was wide. On the other hand, the output signal of the second embodiment using the antiferromagnetic film is larger than that of the conventional SAL bias method and the first embodiment, and the output signal increases almost in proportion to the track width even when the track width is 3 μm or more.

As shown in FIG. 3, in the second embodiment in which an antiferromagnetic film is also used, a bias angle which is desirable for a linear response even in a wide track width is obtained due to the exchange interaction between the antiferromagnetic film and the MR film. It is because it can be obtained. Further, in the first embodiment having only the permanent magnet film, the magnetization of the MR film near the permanent magnet film is strongly fixed by the permanent magnet film, and the output signal is reduced. On the other hand, in Example 2 in which the antiferromagnetic film was also used, a lateral bias magnetic field could be sufficiently applied even with a weaker permanent magnet film than in Example 1, and the output signal increased compared to Example 1. When an antiferromagnetic film is laminated on the entire surface of the MR film, a lateral bias magnetic field can be sufficiently applied even with a weaker permanent magnet film.
However, when laminated on the entire surface, the magnetization of the MR film is strongly fixed by the antiferromagnetic film even in the vicinity of the air bearing surface where the magnetic field of the recording medium is the largest, and the output signal is smaller than in the first embodiment. For this reason, when an antiferromagnetic film is used together, it is desirable to perform patterning and lamination in a region where a sense current hardly flows as shown in FIG. 2 or in a region away from the air bearing surface and where the magnetic field of the recording medium is weak.

The output signal of the MR head is required not only to have a large amplitude but also to have good vertical symmetry of the waveform. In order to process as a signal by an amplification process or the like by an electric circuit after the signal detection of the MR head, the difference between the positive and negative amplitudes needs to be within about 20% of the average amplitude. The range of the track width that satisfies the vertical symmetry criterion is 3 μm or less in the first embodiment using only the permanent magnet film.
In Example 2 where an antiferromagnetic film was also used, the entire range studied, S
In the AL bias method, it was 2 μm or more. This range substantially corresponds to the range indicated by the gray region in FIG. 3, and the MR head has a good linear response to a magnetic field at a bias angle of about 45 °.

In order to examine the sense current dependency of the vertical symmetry, the sense current was set to 0.2 × 10 ⁷ for each method.
The variation in vertical symmetry was measured by increasing A / cm ² . As a result, in the method of the present invention, the variation was within 2% in all cases, but in the SAL bias method, the variation was nearly 20%.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. (Embodiment 1) FIG. 1 is an elevational view of an MR element using a permanent magnet bias method according to the present invention. The MR film 1 is formed so that the direction of the axis of easy magnetization is aligned with the height direction of the MR film and longer than the track width. The permanent magnet film 1 is arranged on both sides of the MR film 1 in the track width direction, and the magnetization 4 of the MR film facing the MR film height direction is inclined by the permanent magnet film. An electrode 3 is arranged on a permanent magnet 2 to supply a sense current to the MR film 1. A magnetic signal from the recording medium 9 can be read by the MR element having the above structure. Note that M shown in FIG.
FIG. 5 shows the arrangement of the R element in the MR head. FIG. 5 is an elevational view of the recording / reproducing separation type head and an enlarged view of the MR element 2.
0 is shown. The recording / reproducing separation type head is obtained by laminating a thin film induction type recording head 15 and a magnetoresistive effect type reproducing head 16 on a substrate 19. The thin-film inductive recording head 15 writes magnetic information on a recording medium by exciting the lower magnetic pole and upper shield film 12 connected to the upper magnetic pole 17 with the coil 18. The magnetoresistive read head 16 has the MR element 20 of the present invention between the lower magnetic pole / upper shield film 12 and the lower shield film 13. Insulating film 14 between each part
, But the description is omitted in FIG.

The MR element 20 has the permanent magnet film 2 disposed at both ends of the MR film 1 in the track width direction.
An electrode Mo3 is arranged thereon, and an antiferromagnetic film 10 is arranged on the surface of the MR film. Here, the MR film 1 is made of NiFe
The permanent magnet film 2 is formed of CoPt, and the electrode 3 is formed of Mo.

At this time, the track width, that is, the electrode interval is 0.1 mm.
It is formed to have a thickness of 5 to 4.0 μm. The MR film height 7 of the MR film was 20 μm and the film thickness was 25 nm. The distance (gap length) between the upper and lower shield films was 0.25 μm and 0.23 μm, respectively, for the conventional method and the present invention. The thickness of the magnet film is
The conventional method and the present invention are 50 nm and 25 nm, respectively. The saturation magnetization of each of the magnet films is 0.7T. The region where the sense current flows is defined by the height 8 of the electrodes at both ends of the track.
Since the resistance of the MR element 20 shows the electrode height dependence of the element resistance as shown in FIG. 8, a resistance lapping guide (RLG element) provided separately from the MR element is provided.
The element resistance was measured using an element and an element for monitoring the resistance and controlling the element height to perform lapping, and processing was performed so that the electrode height was 60% of the track width.

Recording was performed on a recording medium using the inductive head 15 actually formed on the MR element, and the reproduction characteristics of the MR element 20 were examined. At this time, a head having a track width of 3 μm was used as the inductive head. The sense current density is 2 × 10 ⁷ A / cm ² for the conventional head and 5 × 1 for the head of the present invention.
0 ⁷ A / cm ² . Twenty sets of sample heads were prepared for each track width, and a measurement was performed by applying a recording current of 0.3 AT to the thin film induction type recording head, and the average value was shown in FIG.

As a result, as shown in FIG. 4, the output signal is almost proportional to the track width in both methods. Track width 4
Except in the case of μm, the output signal of the head of the present invention is larger than that of the conventional method. In the conventional method, the output signal sharply decreased when the track width was less than 2 μm.

The output signal is proportional to the sense current flowing in the MR film showing a change in magnetoresistance. In the method of the present invention, it is possible to apply a bias with a single layer of the MR film, so that there is no reduction in efficiency due to the shunting of the sense current (to the SAL film and the non-magnetic film) as in the SAL bias method. A sensitive head can be realized. Further, in the method of the present invention, since the MR film has a high height, the heat dissipation is good, and the temperature rise can be suppressed to the same degree even when used at a high sense current density 2.5 times that of the SAL bias method. Further, the signal of the MR head has a bias angle of 4
When the track width is as small as 0.5 μm, the bias can be applied only to about 10 ° when the track width is reduced to 0.5 μm. From these three points, the output signal of the method of the present invention is larger than that of the conventional SAL bias method.

In the present invention, the output signal is reduced when the track width is 3 μm or more, as shown in FIG. 3, because the bias is applied too much when the track width is wide.

The output signal of the MR head is required not only to have a large amplitude but also to have good vertical symmetry of the waveform. In order to process as a signal by an amplification process by an electric circuit after the signal detection of the MR head, the difference between the positive and negative amplitudes needs to be about 20% of the average amplitude. The range of the track width satisfying the criterion of the vertical symmetry was 3 μm or less in the method of the present invention and 2 μm or more in the SAL bias method. FIG. 3 in which the bias angle is predicted by simulation
When compared with this range, this range substantially corresponds to the range indicated by the gray region, and the MR head has a good linear response to a magnetic field at a bias angle of about 45 °.

Next, in order to examine the sense current dependency of the vertical symmetry, the sense current was set to 0.2 × 10 ⁷ for each method.
The variation in vertical symmetry was measured by increasing A / cm ² . As a result, in the method of the present invention, the variation was within 2%,
In the L bias method, it fluctuated by almost 20%.

In the method of the present invention, Barkhausen noise caused by the multi-domain structure in the MR element was not observed. This is because the MR film height, which is a dimension in the easy axis direction, is 20 μm and other dimensions (track width 0.5 to 4 μm, M
This is because the MR film was maintained in a single magnetic domain state.

As described above, in this embodiment, even if the track is narrowed, a bias necessary for a linear response can be sufficiently applied, and an output signal having a large amplitude of the output signal and a good vertical symmetry of the waveform as compared with the conventional head can be obtained. can get. This is because, in the method of the present invention, a bias can be applied with a single layer of the MR film, so that a high-sensitivity head can be realized without a decrease in efficiency due to a shunt of a sense current unlike the SAL bias method.

(Embodiment 2) FIG. 2 is an elevational view of an MR element using a permanent magnet bias method according to the present invention. In contrast to Example 1, FIG. 2 shows an MR element in which an antiferromagnetic film 10 is patterned and laminated on a part of the MR film 1. Here, as the permanent magnet film 2, a CoNi-based magnet film having a saturation magnetization of 0.4T was used.
In addition, FeMn was used as the antiferromagnetic film.

As a result, as shown in FIG. 3, the output signal of the embodiment 2 in which the antiferromagnetic film is also used is larger than that of the conventional SAL bias method and the embodiment 1. In the first embodiment using only the permanent magnet film, the output signal decreased when the track width was 3 μm or more. In the second embodiment using the antiferromagnetic film, the output signal was almost proportional to the track width even when the track width was 3 μm or more. increased.

This is because, as shown in FIG. 3, due to the exchange interaction between the antiferromagnetic film 10 and the MR film 1, a desired bias angle for linear response can be obtained even with a wide track width. In the first embodiment using only the permanent magnet film 2,
The magnetization of the MR film near the permanent magnet film is strongly fixed by the permanent magnet film, and the output signal is reduced. On the other hand, the second embodiment in which the antiferromagnetic film 10 is also used is the first embodiment.
Even with a weaker permanent magnet film, a sufficient lateral bias magnetic field could be applied, and the output signal increased compared to Example 1.

When the antiferromagnetic film is laminated on the entire surface of the MR film, a lateral bias magnetic field can be sufficiently applied even with a weaker permanent magnet film. However, when laminated on the entire surface, the magnetization of the MR film is strongly fixed by the antiferromagnetic film even in the vicinity of the air bearing surface where the magnetic field of the recording medium is the largest, and the output signal is smaller than in the first embodiment. For this reason, when an antiferromagnetic film is used together, it is desirable to pattern and laminate in a region where no sense current flows as shown in FIG.

The output signal of the MR head is required not only to have a large amplitude but also to have good vertical symmetry of the waveform. In order to process as a signal by an amplification process or the like by an electric circuit after the signal detection of the MR head, the difference between the positive and negative amplitudes needs to be within about 20% of the average amplitude. The range of the track width that satisfies the vertical symmetry criterion is 3 μm or less in the first embodiment using only the permanent magnet film.
In Example 2 where an antiferromagnetic film was also used, the entire range studied, S
In the AL bias method, it was 2 μm or more. This range substantially corresponds to the range indicated by the gray region in FIG. 3, and the MR head has a good linear response to a magnetic field at a bias angle of about 45 °.

Further, in order to examine the sense current dependency of the vertical symmetry, the sense current was set to 0.2 × 10 ⁷ for each method.
The variation in vertical symmetry was measured by increasing A / cm ² . As a result, in the method of the present invention, the variation was within 2% in all cases, but in the SAL bias method, the variation was nearly 20%. This is because the SAL bias method is a method in which the SAL film is saturated by the sense current and a bias is applied to the MR film by a leakage magnetic field from the SAL film, and the bias angle changes depending on the magnitude of the sense current. As a result, as shown in FIG. 4, the output signal is almost proportional to the track width in both methods. Except for a track width of 4 μm, the head of the present invention has a larger output signal than the conventional method. In the conventional method, the output signal sharply decreased when the track width was less than 2 μm.

Also, according to the method of the present invention, Barkhausen noise caused by the multi-domain structure in the MR element is not observed. This is because the MR film height, which is the dimension in the easy axis direction, is 20 μm and other dimensions (track width 0.5 to 4 μm, MR
This is because the MR film was maintained in a single magnetic domain state.

As described above, in this embodiment, even if the track is narrowed, a bias necessary for a linear response can be sufficiently applied, and an output signal having a large amplitude of the output signal and a good vertical symmetry of the waveform as compared with the conventional head can be obtained. can get. This is because the bias can be applied with a single layer of the MR film in the method of the present invention, so that the efficiency does not decrease due to the shunt of the sense current in the multilayer film as in the SAL bias method, and a high-sensitivity head can be used. realizable.

According to the present invention, even if the track is narrowed,
The bias required for the linear response can be sufficiently applied, and an output signal having a larger amplitude of the output signal and a good vertical symmetry of the waveform as compared with the conventional head can be obtained.

[Brief description of the drawings]

FIG. 1 is an elevation view of an MR element using a permanent magnet bias method according to the present invention.

FIG. 2 is an elevation view of a permanent magnet bias method MR element according to the present invention.

FIG. 3 shows a bias method using a permanent magnet film according to the present invention;
And the conventional SAL bias method, the track width Tw
Bias angle when changing

FIG. 4 shows the dependence of the amplitude of a reproduction output signal from the MR head of the embodiment of the present invention on the track width Tw.

FIG. 5 is an elevation view of a recording / reproducing separation type head and an enlarged view of an MR element.

FIG. 6 is an elevation view of a conventional SAL bias method MR element.

FIG. 7 is an elevation view of a conventional permanent magnet bias method MR element.

FIG. 8: Dependence of element resistance on electrode height

[Explanation of symbols]

1 MR film, 2 permanent magnet film, 3 electrodes, 4 MR film magnetization direction, 6 MR element track width, 7 MR film height, 8 electrode height, 9 recording medium, 10 antiferromagnetic film,
11 Easy magnetization axis of antiferromagnetic film 12 Lower pole / upper shield film, 13 Lower shield film, 14 Insulating film, 1
5 thin film induction type recording head, 16 magnetoresistive effect reproducing head, 17 upper magnetic pole, 18 coil, 19 substrate,
20 MR element, 21 non-magnetic film, 22 SAL film.

Claims (3)

[Claims] In a magnetoresistive head having a configuration in which permanent magnet films are arranged at both ends in the track width direction of an MR film, a dimension in a height direction of the MR film is made larger than a track width to form the permanent magnet film. A magnetoresistance effect type magnetic head characterized by applying a lateral bias magnetic field by using the same. 2. The magnetoresistive head according to claim 1, wherein the easy axis of the MR film is substantially in the direction of the height of the MR film, and the easy axis of the permanent magnet film is substantially in the direction of the track width. A magneto-resistance effect type magnetic head, characterized in that: 3. The magneto-resistance effect type magnetic head according to claim 1, wherein an anti-ferromagnetic film is disposed on the entire surface or a part of the MR film. head.