JP2800484B2 - Magnetoresistive head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shield type magnetoresistive head used for a magnetic recording device such as a magnetic disk device and a magnetic tape device.

[0002]

2. Description of the Related Art A magnetoresistive head (hereinafter referred to as an MR head) has a high reproducing sensitivity and a reproducing output does not depend on a relative speed between a magnetic recording medium and a magnetic head. This device is advantageous for high density and miniaturization. In an MR head, a magnetoresistive element (hereinafter, referred to as an MR element) is generally arranged perpendicular to a magnetic recording medium, and detects a component perpendicular to the magnetic recording medium among magnetic fluxes generated from the magnetic recording medium. I do. As an example of an MR head having increased resolution, a shield type MR head in which a magnetic shield made of a soft magnetic material is arranged on both sides of an MR element is known, and is published in 1975 by IEE Transactions On. · magnetics magazine the MAG-11 Volume 1206 pages, JP Akira 60-151
816, JP Sho 63-184906 Patent Publication is shown like in JP-B-63-50769.

In a shield type MR head, a magnetic shield absorbs extra magnetic flux among magnetic fluxes emitted from a magnetic recording medium, and detects a magnetic flux detected by an MR element from a low linear density recording area to a high linear density recording area. The amount will be almost constant. Therefore, the output voltage reproduced by the MR element has a constant amplitude from the low linear density recording area to the high linear density recording area, and a signal with small waveform interference and no reading error can be obtained.

[0004]

In order to increase the resolution of an MR head by disposing a magnetic shield, it is necessary to make the shield width larger than the MR detection width. However, as the shield width increases, the risk of crosstalk from adjacent tracks increases.

FIG. 3 shows an MR detector having a width of 8 μm and a width of 100 μm.
5 is an example of off-track characteristics of a shield type MR head having a shield of m and a thickness of 1 μm.

The off-track characteristic is measured as a reproduction output when a shield type MR head is shifted in the track width direction with respect to a track having a track width of 8 μm and a recording density of 15 KFCI created on a magnetic disk by a recording head. . The reproduction output has a maximum value when the MR detection unit comes right above the track (X = 0 in FIG. 3).

From the off-track characteristics shown in FIG. 3, even when the track is sufficiently away from the MR detecting section, if the track is under the shield, magnetic flux flows through the shield to the MR detecting section, causing output to occur. It can also be seen that the output hardly depends on the distance between the MR detector and the track.

Usually, a recording signal is recorded on a plurality of tracks on a medium as shown in FIG. 4, and each track is separated by a guard band.

Accordingly, in the MR head having the off-track characteristic as shown in FIG. 3, since the output from the tracks other than the on-track is included as noise, the crosstalk increases. The amount of crosstalk

[0010]

(Equation 1)

Under the conditions that the track width is 8 μm and the guard band is 4 μm, the crosstalk amount of the head having the characteristics shown in FIG. 3 is −19 dB, which does not reach −25 dB required from the viewpoint of reliability. . Conversely, in order to reduce the amount of crosstalk, it is necessary to increase the track interval (guard band), which is extremely disadvantageous for increasing the recording density.

It is an object of the present invention to obtain a head having a high resolution with the above-mentioned crosstalk being smaller than the level required by the apparatus and suitable for a high track density.

[0013]

According to the present invention, a soft magnetic lower shield layer, a lower shield gap layer, a magnetoresistive element, an upper shield gap layer, and a soft magnetic upper shield layer are laminated on a non-magnetic substrate. A magnetoresistive head for reading signals recorded on tracks separated by guard bands on a magnetic recording medium, wherein the soft magnetic lower shield layer and the soft magnetic upper shield layer have a thickness of 3 μm or more. There is a feature.

[0014]

The output is generated when the track is sufficiently away from the MR detector as shown in FIG. 3 because the magnetic flux from the track flows into the MR detector through the shield.

FIG. 5 is a calculation result showing the off-track dependence of the magnetic field applied to the MR detecting portion of the MR head having a shield having a width of 100 μm and a thickness of 1 μm. Since the same off-track dependency as the experimental result in FIG. 3 is shown, it is clear that this magnetic field is the cause of the crosstalk output.

FIG. 6 shows the dependence of the magnetic field on the shield thickness when the off-track amount is 25 μm. Since the magnetic flux absorbed by the shield increases as the thickness of the shield increases, the magnetic field applied to the MR detection unit decreases.
In order to reduce the amount of crosstalk, it is effective to reduce this magnetic field. As described above, when the thickness of the shield is 1 μm, the crosstalk amount is 6 dB larger than the value required for realizing the device. Therefore, in order to reduce the amount of crosstalk by 6 dB, it is necessary to reduce the magnetic field applied to the MR element to half or less. According to FIG. 6, this is achieved by setting the thickness of the shield to 3 μm or more, and it is possible to obtain a shield type MR head having small crosstalk and suitable for high track density.

[0017]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

First, on a ceramic non-magnetic substrate, a thickness of 3
A lower shield 5 using a permalloy of μm is formed by a plating method, and is patterned to a width of 100 μm by ion milling. On top of this, 0.4 μm thick SiO ₂
Is formed by a sputtering method. Further, an MR film 1 made of a permalloy film having a thickness of 0.04 μm, a shunt film 2 made of a Ti film having a thickness of 0.02 μm, and CoZr having a thickness of 0.05 μm
An MR element on which a bias film 3 made of a Mo film is laminated is formed by a sputtering method. CoZrMo film 3
Is magnetically coupled to the permalloy film 1 to give a bias, and the magnetoresistance effect of the permalloy film 1 is detected. Ti
The film 2 magnetically separates the permalloy film 1 and the CoZrMo film 3. An electrode 4 using Au having a thickness of 0.2 μm is formed thereon by a vapor deposition method, and the MR element and the electrode 4 are simultaneously patterned using photolithography technology and ion etching technology. Next, the detection portion 8 of the MR element
Only for μm, the electrode 4 is removed by chemical etching.
Further, a gap 8 between upper shields using an SiO ₂ film having a thickness of 0.3 μm is formed by a sputtering method, and an upper shield 6 using a permalloy having a thickness of 3 μm is formed thereon.
Is formed by a plating method, and is formed into a pattern having a width of 100 μm using a photolithography technique and an ion etching technique.

In the first embodiment, the MR detection width is 8 μm.
m, and the shield thickness was 3 μm. Similarly, heads having a shield thickness of 1.6 μm were prepared, and they were used as Comparative Example 1 and Example 2, respectively.

Using these shield type MR heads,
The measurement was performed on a disk having a track width of 8 μm and a guard band width of 4 μm. A signal is recorded at a recording density of 15 KFCI on an on-track and 10 KFCI on another track,
When the difference between the two outputs was measured as the amount of crosstalk by a spectrum analyzer, the results in Table 1 were obtained.

[0021]

[Table 1]

As shown in Table 1, the shield type M according to the embodiment of the present invention is shown.
The R head has a crosstalk amount of −25 dB or less,
It can be seen that the head has low crosstalk. On the other hand, in a head with a thinner shield than the value determined by the present invention, the crosstalk amount becomes -25 dB or more,
It turns out that it is difficult to implement the device.

Next, as a third embodiment, an example in which the track width and the MR detection width are not equal will be described.

Using a shield type MR head having an MR detection width of 4 μm, a shield width of 30 μm, and a shield thickness of 3 μm manufactured in the same manner as in Example 1, measurement was performed on a disk having a track width of 5 μm and a guard band width of 1 μm. As a result, the crosstalk amount was −26.1 dB. From this example, it can be seen that the present invention is also applied to the case where the track width and the MR detection width are not equal.

Next, an example using a shunt bias method will be described as a fourth embodiment. FIG. 2 is a perspective view of a magnetoresistive head using a shunt bias method. In this embodiment, M
The R element is composed of only the MR film 1 made of permalloy and the shunt film 2 made of Ti, and a magnetic field generated by a current flowing through the Ti film becomes a bias magnetic field. MR detection width 8μ
When a measurement was performed on a disk having a track width of 8 μm and a guard band width of 4 μm using a shield type MR head having a shield width of 50 μm and a shield width of 50 μm, the crosstalk amount was −2.
It was 8.2 dB. This example shows that the present invention is also applied to a shield type MR head using the shunt bias method.

It is needless to say that the results obtained by the present invention are also valid for bias methods other than the soft film bias method and the shunt bias method shown in the examples.

In the above embodiment, permalloy is used as the shield, but the same effect can be obtained with other soft magnetic materials.

[0028]

As described above, in the magneto-resistance effect head according to the present invention, it is possible to obtain a magneto-resistance effect head having small crosstalk and suitable for high track density.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a magnetoresistive effect head according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a magnetoresistive effect head according to a fourth embodiment of the present invention.

FIG. 3 is a diagram illustrating off-track characteristics of a shield type MR head.

FIG. 4 is a diagram of a medium and a head viewed from a direction perpendicular to a medium surface.

FIG. 5 is a diagram illustrating the off-track amount dependency of a magnetic field applied to a detection unit of a magneto-resistance effect head.

FIG. 6 is a diagram illustrating a shield thickness dependence of a magnetic field applied to a detection unit of the magnetoresistive head.

[Explanation of symbols]

 Reference Signs List 1 MR film 2 Shunt film 3 Bias film 4 Electrode 5 Lower shield 6 Upper shield 7 Lower shield gap 8 Upper shield gap 9 MR detector 10 Track 11 Guard band

Claims (1)

(57) [Claims] A magnetic recording medium having a structure in which a soft magnetic lower shield layer, a lower shield gap layer, a magnetoresistive element, an upper shield gap layer, and a soft magnetic upper shield layer are laminated on a non-magnetic substrate. A magnetoresistive head for reading signals recorded on tracks separated by an upper guard band, wherein the thickness of the lower soft magnetic shield layer and the upper soft magnetic shield layer is 3 μm or more. Effect type head.