JPH09138913A - Magneto-resistive head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To practicably prevent flank reading by making the width of end part regions narrower than a central region which is a magnetosensitive part to the extent of obviating the occurrence of a side lobe by the transition region at the boundary between both regions. SOLUTION: This magneto-resistive head(MR head) has stripes consisting of laminates of magneto-resistance effect films(MR films) 1, nonmagnetic films 3 and magnetic films 2. The central region of these stripes has a reproducing function. The end part regions are provided with a pair of electrodes 6, 7 via antiferromagnetic films or permanent magnet films 5. The width P of the end regions is made narrower than the width of the central region and is set at P<5μm to the extent of substantially obviating the occurrence of the side lobe by the transition region at the boundary between the central region and the end part regions in the reproduced output characteristics at the time of off- tracking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive effect magnetic head for a magnetic disk device, and more particularly to an MR element terminal structure most suitable for a narrow track width.

[0002]

2. Description of the Related Art In magnetic disk devices, MIG (Met)
A magnetoresistive head has been actively developed as a head that replaces an inductive head such as an al in Gap) head or a thin film magnetic head. Since the magnetoresistive head is a read-only head that reproduces data by utilizing the magnetoresistive effect of a magnetic film such as Ni-Fe, it is usually constructed integrally with a recording head. As the recording head, an inductive head having a thin film structure in which the number of coil turns is slightly reduced compared to the conventional one is used so that recording can be performed up to a high frequency.

A detailed disclosure of the magnetoresistive head for read-only use is found in US Pat. No. 4,663,685.
It is publicly known from Japanese Patent Publication No. The magnetoresistive head has high sensitivity regardless of the peripheral speed, and in principle does not have an inductance component, so white noise due to the head is small even in the high frequency range, and undershoot does not occur in the isolated wave, so a specific frequency It has features suitable for high density, such as no reduction in output. For this reason, the magnetoresistive head is more suitable than the MIG head or the thin film magnetic head for the high density magnetic disk device, and the development of the magnetoresistive head has become very important.

However, there are many problems to be solved in the magnetoresistive head (MR head), for example, instability of reproduction signal output characteristics, occurrence of side reading, reproduction waveform asymmetry problem on the MR head side. In addition to the problems related to the single performance, there are many problems due to the combination of the head and the medium, such as the problem of medium noise or modulation.

The problem of side reading in the prior art will be described in detail below. The existence of slight active areas at the end areas on both sides of the reproduction track width (central area) causes the recording information to be mixed into the reproduction signal component even when the target recording track is deviated. In the conventional magnetoresistive head, the length of the end region in the track width direction is 15
Since the length is selected to be 25 μm to 25 μm, such a problem occurs. When the side reading exceeds a certain threshold value, the signal ratio to noise decreases, and in some cases, a servo defect causes a head positioning error. In view of the current situation where the recording track width is becoming narrower, this side reading problem must be solved by all means in order to read the recording information from the recording track without error.

Japanese Unexamined Patent Publication (Kokai) No. 6-176324 discloses a magnetoresistive read transducer assembly in which the critical dimension of the end region is defined with respect to the total head length in the track width direction. The critical dimension is a thin film magnetoresistive layer having equal length end regions of 5-10 microns, and a magnetoresistive read transducer assembly including the same is disclosed. By reducing the length of the end region that causes side reading, the side reading component is reduced. However, as a result of detailed study of the end region of the MR head, the inventor of the present application found that the length of the end region is 5 to 1
It has been found that there is almost no effect of suppressing side surface reading in the range of 0 μm, and the length of the end region needs to be shortened to 5 to 10 μm or less.

The MR head will be described with reference to FIGS.
FIG. 7 is a perspective view of the MR head as seen from the medium surface.
The cross section of the MR element portion which is the detection portion is shown in FIG. M shown in FIG.
The R head is integrally formed on the substrate 16 via an insulating layer with a head using an MR film for reading and an inductive head having a thin film for recording. The thin film inductive head shown here includes a lower magnetic pole 12, an upper magnetic pole 13,
The recording gap 14 constitutes a magnetic circuit, and the recording current is supplied to the coil 13 to record information on a medium such as a disk. As shown in FIG. 8, the MR head includes a magnetoresistive effect film (hereinafter abbreviated as MR film) 1,
A stripe is formed by a laminated body of the non-magnetic film 3 and the soft magnetic film 2, and antiferromagnetic films or permanent magnet films 4 and 5 are arranged in end regions on both sides of the stripe, and electrodes 6 and 7 are further formed. To be done. This stripe is electromagnetically shielded by the lower shield 8 and the alumina insulating film 9. As shown in FIG. 8, the length P of the electrode and the antiferromagnetic film or permanent magnet film in the end region is determined by the method described in JP-A-6-1763.
According to Japanese Patent Laid-Open No. 24, it has a length of 5 microns or more. The inventor of the present application discovered that there is an active area in this end area. Therefore, in order to reliably read information from the narrower recording track without a read error, it is necessary that the end regions do not show activity.

[0008]

Generally, when side reading is evaluated, an evaluation method called off-track characteristic is used. The off-track characteristic indicates the relationship between the amount of movement and the output when the head is moved in the radial direction of the magnetic disk after recording on the medium with the recording position set to zero. FIG. 10 shows a measurement example. The maximum output value is reached when the entire reproduction track width is on-track at the recording position, and the output is at the minimum DC erase level when completely off-tracked. Further, the slope from the start of deviating from the recording track to the time of completely off-track becomes substantially linear if the sensitivity within the reproducing track width of the MR head is uniform. Looking at the off-track characteristics of the conventional example of FIG. 10, the output decreases as the track position moves away from the zero position,
The slope shows linearity in the range of 3 to 5 microns, but an extreme value is seen in the vicinity of 5 microns. Since the point where the slope is extended is considered to be the position at which the playback track width is completely off-track from the recording track, it is considered that this extreme value occurs at the end region outside the playback track width. Corresponds to side reading.
Hereinafter, this extreme value will be referred to as a side lobe. The cause of the side lobes is considered to be that the magnetic transition region B in the soft magnetic film 2 as shown in FIG. 9 guides the magnetic flux from the medium to the central region. The magnetization transition region B inevitably occurs because the magnetization distribution in the soft magnetic film 2 during active operation of the MR element is oriented in the stripe longitudinal direction in the end region and in the stripe minor axis direction in the central region. is there. Further, in the MR head of the prior art, the side lobes, that is, the positions where the magnetization transition regions are generated are very close to the boundary between the central region and the end regions, and at least on the order of several microns from the boundaries toward the end regions. Is expected to be. The inventor of the present application produced a required number of MR heads in which the length of the end region was changed in the order of several microns, and systematically evaluated the size of the side lobes that occur in the off-track characteristics of each head to obtain the ends. This is a study of the optimum size of the partial area.

On the other hand, Japanese Patent Laid-Open No. 3-125311 discloses that a thin film magnetoresistive layer (MR layer) is arranged only on a recording track. Disclosed is a magnetoresistive read transducer structure that forms a junction adjacent to a hard magnetic film and electrodes located outside the track width. In this known example, it is considered to correspond to the case where there is almost no end region, that is, zero. However, as in this known example, when the thin film magnetoresistive layer is only on the recording track and the bonding area with the electrode cannot be sufficiently secured, the contact resistance becomes large and the noise increases due to the Joule loss heating due to the bias current. However, the performance will be degraded accordingly. However, this Japanese Patent Laid-Open No. 3-12531
The purpose of the patent disclosed in Japanese Patent Laid-Open No. 1 is described as suppression of Barkhausen noise, and no particular description or teaching is given on the effect regarding side reading prevention. As is clear from the above description, the main object of the present invention is to obtain an MR head in which side reading is completely or practically suppressed without any problem.

[0010]

Means for solving the above problems will be described in detail. A stripe in which a magnetoresistive film (MR film), a non-magnetic separation film and a magnetic film are laminated is divided into a central region and an end region, and the central region has a reproducing function.
Further, in a magnetoresistive head (MR head) in which a pair of electrodes are arranged in the end region through an antiferromagnetic film or a permanent magnet film, the reproduction output characteristics at the time of off-track have a boundary between the center and end regions. The width of the end region is made narrower than that of the central region and the width of the end region is less than 5 μm so that the side lobe due to the transition region is not substantially generated.

[0011]

In the conventional MR head, the magnetic transition region in the soft magnetic film guides the magnetic flux from the medium to the central region to cause a side lobe in the reproduction output characteristic during off-track.
In the present invention, the side lobe was suppressed by making the end region less than 5 microns. This is because the magnetization distribution in the soft magnetic film during the active operation of the conventional MR element is oriented in the stripe longitudinal direction in the end region and in the minor axis direction in the central region, so that a transition region is inevitably generated. On the other hand, in the present invention, it is considered that this magnetization distribution is changed to a distribution that does not cause a transition region.

[0012]

Example 1 FIG. 5 shows the relationship between the length P of the end region and the size of the side lobe. The size of the side lobe is the ratio (%) to the size of the main peak of the off-track characteristics.
Indicated by Looking at the figure, in the edge region of 5 μm to 10 μm, which is the critical dimension of Japanese Patent Laid-Open No. 6-176324, there is some improvement compared with the length longer than that, but it is rather shorter than 5 μm. Therefore, it can be seen that a remarkable side lobe reduction effect can be obtained. The reason for this is considered to be that the generation of the magnetic transition region, which inevitably occurs in the conventional head, is suppressed. That is, the magnetization distribution in the soft magnetic film during the active operation of the conventional MR element is oriented in the stripe longitudinal direction in the end region and in the minor axis direction in the central region, so that a transition region is inevitably generated. On the other hand, in this example, it is considered that this magnetization distribution is changed to a distribution that does not cause a transition region. Furthermore, when the length of the end region is set to 4 μm or less, the size of the side lobe can be reduced to 3%. In recent magnetic disk devices,
It is considered that at least the side lobe needs to be suppressed to 3% or less in order to position the head without causing a servo error, and it can be said that the end length of 4 μm or less satisfies this condition. Further, when the length of the end region is set to 1.5 μm or less, the ratio of the main peak to the side lobes becomes almost zero, and it can be seen that the side lobes disappear completely. Set the length of the edge region to 1.
Setting the thickness to 5 microns or less is difficult in terms of the manufacturing process and may increase the contact resistance, but it is absolutely necessary to obtain an MR head optimal for narrowing the track. FIG. 6 shows an example of the contact resistance of the MR head having a short end region length, which is manufactured by using high-precision photolithography equipment. When using an exposure device such as a stepper with good performance, the latest film forming device, and etching device, good contact conditions can be obtained and the low contact resistance can be maintained when the end region length is 0.2 μm or more. I was able to. For the edge region length of 0.2 μm or less, the contact area could not be sufficiently secured, and an unacceptable increase in the contact resistance value was observed.

[0013]

In the conventional magnetoresistive head having a wide end area, the recorded information outside the target recording track is also reproduced as the reproduced signal component, and it is necessary to reduce the side reading. This meant that it was difficult to read information from narrow recording tracks without error. According to the present invention, side reading can be completely prevented in practical use, and it is possible to provide an MR head most suitable for narrowing the track.

[0014]

[Brief description of the drawings]

FIG. 1 is a sectional view of a magnetoresistive head of the present invention.

FIG. 2 is a sectional view of a magnetoresistive head of the present invention.

FIG. 3 is a schematic diagram of reproduction by the magnetoresistive head of the present invention.

FIG. 4 shows off-track characteristics of the magnetoresistive head of the present invention.

FIG. 5 is a relationship between a side lobe and an end region length.

FIG. 6 shows the relationship between contact resistance and end region length.

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

FIG. 8 is a sectional view of a conventional magnetoresistive head.

FIG. 9 is a schematic diagram of reproduction by a conventional magnetoresistive head.

FIG. 10 shows off-track characteristics of a conventional magnetoresistive head.

[Explanation of symbols]

1 magnetoresistive effect film, 2 magnetic film, 3 non-magnetic film, 4
Antiferromagnetic film or permanent magnet film, 5 Antiferromagnetic film or permanent magnet film, 6 electrodes, 7 electrodes, 8 recording track region, 9 guard band, 10 lower shield, 11
Alumina insulating film, 12 lower magnetic pole, 13 upper magnetic pole,
14 recording gaps, 15 coils, 16 substrates.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Kobayashi 5200 Mikashiri, Kumagaya-shi, Saitama Hitachi Metals Co., Ltd.

Claims (4)

[Claims] 1. A stripe comprising a laminated body of a magnetoresistive film (MR film), a non-magnetic separation film and a magnetic film, the stripe being divided into a central region and an end region, and the central region having a reproducing function. In a magnetoresistive head (MR head) having a pair of electrodes provided in the end region through an antiferromagnetic film or a permanent magnet film, the center of the reproducing output characteristics during off-track is And the MR is characterized in that the end region width is narrower than the central region and the end region width is less than 5 microns so that side lobes due to transition regions at the boundaries of the end regions are not substantially generated.
head. 2. The MR head according to claim 1, wherein
An MR head having a width of the end region of 4 μm or less. 3. The MR head according to claim 1, wherein:
The MR head according to claim 1, wherein the terminal region width is in the range of 0.2 to 1.5 microns. 4. The MR head according to any one of claims 1 to 3, wherein the magnetic film is disposed only in the central region or extends to the end regions to the extent that side lobes due to the transition regions are not substantially generated. An MR head characterized in that