JPH07287817A - Magnetoresistive head - Google Patents

Abstract

PURPOSE:To obtain sufficient shield characteristics, to eliminate cross talk, and to increase the reproduction sensitivity by forming a magnetic shield nearby an MR element in a slide surface direction, and connecting the magnetic shield to a nonmagnetic substrate and grounding it. CONSTITUTION:On the vertical surface 12 of an Al2O3.TiC substrate as a nonmagnetic conductive substrate 10, an MR head 1 and an inductive head 2 are formed across a protective film 5 formed of alumina, and a magnetic shield layer 3 is formed on a magnetic recording medium 8 and on a slide surface while surrounding the periphery of the sense part of the MR head. Then the magnetic shield layer 3 is arranged in parallel to the slide surface 9 during operation. The magnetic shield nearby the MR element is connected to the nonmagnetic conductive substrate 10 and grounded. Consequently, this magneto-resistance effect type head can suppress an off-track noise, a cross talk noise, etc., by the effects of the shield shape, and is adaptive to high density and attains high resolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a magnetoresistive head used in magnetic disk devices, magnetic tape devices and the like.

[0002]

2. Description of the Related Art A magnetoresistive head (hereinafter referred to as an MR head) is a thin film having a magnetoresistive effect such as Ni ₈₀ Fe ₂₀ (hereinafter referred to as an MR film) and has a property that its electric resistance value changes depending on an applied magnetic field. It is a magnetic head that reads the magnetization information from the magnetic recording medium by utilizing it, and has a higher reproduction sensitivity than the inductive head and does not depend on the peripheral speed of the magnetic disk. It is an advantageous device.

The MR head is a read-only head, and usually an inductive head for writing is arranged in close proximity and used as a recording / playback separation composite type head. The MR head has a magnetic shield arranged in the vicinity thereof. The structure of the conventional composite type head and the effect of the shield will be described with reference to FIG.

FIG. 5 is a cross-sectional view of a conventional composite type head, in which a reproducing MR head 1 and a writing inductive head 2 are arranged close to each other with a protective film 5 interposed therebetween. MR
The magnetic shield layers 3a and 3b are provided on both sides of the head, which are formed when the elements are stacked, and are present in the direction perpendicular to the magnetic recording medium 8 during head operation. The effect of the shield is described in JP-A-3-290812 and JP-B-58-3.
6406 and the like, this is to prevent the magnetic flux generated from the pole tip of the inductive head during recording from adversely affecting the magnetization state of the MR film in the MR head. It is known that the disorder of the magnetization in the MR film causes Barkhausen noise due to the movement of magnetic domains during reproduction, and how to suppress it is a technical issue.

The magnetic shield layer also has the effect of removing stray magnetic flux from adjacent bits and adjacent tracks during reproduction. The magnetic shield layer functions as a return yoke for efficiently guiding the magnetic flux from the medium during reproduction, and the gap between the magnetic shield layer and the MR head corresponds to the gap length.

Further, when the magnetic shield layer is grounded by some method, the MR head can be protected from damage due to the influence of static electricity or the like.

[0007]

The above-mentioned prior art has the following problems. In the conventional MR head, since both sides of the MR element are sandwiched by the shield layers,
The lower shield, the gap between the lower shields, the MR element including the MR film and the bias applying means, the gap between the upper shields, and the upper shield must be stacked in the above order, but the layers are electrically insulated, magnetically separated, Alternatively, in order to secure the magnetic shield effect, each layer needs to have a certain thickness or more.

However, in this structure, the shield layer and the M
The distance between the R films could not be reduced, and it was difficult to narrow the gap. Further, since the distance between the MR head and the inductive head cannot be reduced, when used in an HDD or the like that uses a rotary actuator, the skew angle changes from the inner circumference to the outer circumference of the disk, and thus the writing inductive head and the reproducing MR head. There is a problem in that the track center deviation of No. 2 becomes large and the off-track noise increases.

Similarly, since each layer as described above is laminated with a certain thickness or more and in a different shape, it is not only structurally complicated, but also flattened when an inductive head is formed thereon. A process is needed. Alternatively, when the above process is not performed, there arises a problem that a thin film such as an electrode layer is arranged so as not to cross a high step, and the pattern arrangement is restricted.

Further, since the process is lengthened, there is a manufacturing problem such as a decrease in yield. On the other hand, in the conventional shield structure of the MR head, since there is no shield on both sides of the MR element portion, there is a problem that crosstalk occurs when off-tracking.

An object of the present invention is to provide an MR head having a magnetic shield effective against crosstalk during off-track, in addition to the effect of the conventional magnetic shield structure. Another object of the present invention is magnetic shield and MR.
It is an object of the present invention to provide an MR head having a small distance between heads, a narrow gap, and high reproduction efficiency. Another object of the present invention is to provide a composite head having a small off-track between the read / write heads. Another object of the present invention is to provide an MR head that is less susceptible to electrostatic breakdown. Another object of the present invention is to provide a composite head having a simple structure and easy to manufacture.

[0012]

In order to solve the above problems, the magnetic shield in the MR head of the present invention has a magnetic shield layer formed around the MR element so as to be arranged parallel to the magnetic recording medium. The pattern of the shield layer is connected to a conductive ceramic substrate such as Altic on the sliding surface.

[0013]

In the magnetoresistive head of the present invention, since the magnetic shield layers cover the four sides of the magnetoresistive element, unnecessary magnetic flux due to noise is almost completely removed, and the magnetic shield layer is provided near the MR element. The potential is electrically the same as that of the magnetic recording medium, and electrostatic breakdown is less likely to occur.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. This figure is a plan view of the main part as seen from the sliding surface 9 side.
An MR head 1 and an inductive head 2 are formed on a vertical surface 12 of an AlTiC substrate which is a non-magnetic conductive substrate 10 with a protective film 5 made of Al ₂ O ₃ (hereinafter referred to as alumina) interposed therebetween. The magnetic shield layer 3 is formed on the sliding surface 9 that slides on the magnetic recording medium 8 so as to surround the periphery of the magnetic recording medium 8. A sectional view taken along the line AA 'in this figure is shown in FIG.

In FIG. 2, an MR head 1 and an inductive head 2 are formed with a protective film 5 on an AlTiC substrate 10 which is a conductive ceramic Al ₂ O ₃ —TiC (hereinafter referred to as AlTiC), and the vicinity of the MR head sensing portion is formed. The magnetic shield layer 3 is formed on. Therefore, during operation, the magnetic shield layer 3 in the MR head of this structure is arranged parallel to the sliding surface 9.

A method of manufacturing the above head will be described. The MR head is processed into a so-called low state in which elements are arranged side by side for one row without a magnetic shield layer. Here, the gap depth processing stops polishing just before the desired amount. In this state, a mask having a desired pattern is formed on the row using a photoresist having photosensitivity. After that, the peripheral region of the MR head made of AlTiC and alumina on the surface is etched by ion milling. At this time,
The etching depth b is set larger than the depth of the MR film at that time. Further, a soft magnetic material such as permalloy is continuously formed to a desired thickness. After that, the resist is peeled off, lifted off, and further polished by pole height processing until the gap depth reaches a desired amount, and the MR element having the magnetic shield layer of this configuration is completed. Finally, the thickness of the magnetic shield layer after processing is larger than the MR depth after processing. This increases the shield effect. Although ion milling is used as the etching method here, a method such as powder beam, reactive ion etching, or excimer laser may be used. Although permalloy is used as the magnetic shield layer here, another conductive soft magnetic material, C, is used.
Needless to say, the same effect can be obtained with an amorphous film or sendust. Although AlTiC is used as the substrate, that is, the slider material, the same effect can be obtained by using other nonmagnetic conductive material such as nonmagnetic ferrite.

Next, the shield characteristics of the MR head having this shield structure were compared with those of the conventional structure. The specifications are the same except for the shield. In addition, the writing inductive head and the distance between the heads are the same. Measurement frequency 1
The S / N ratio in four types of MHz, 2 MHz, 5 MHz, and 10 MHz was measured. The results are shown in Table 1.

[0018]

[Table 1] As can be seen from this, it can be seen that the shield characteristics of this structure are almost the same as the conventional one. 5MHz here
The S / N ratio value of was slightly lower than the normal frequency characteristic, but this is due to the increase in noise due to the servo signal from adjacent bits, in particular, due to the contour effect of the lower shield side edge. I understood. Therefore, when the shield shape was changed to a shape having a curve as shown in FIG. 3, the S / N ratio at 5 MHz was 30.2.
It was found that it was further improved to dB. This indicates that the contour effect of the magnetic shield is made non-parallel to the sensing portion like a curved shape to suppress the contour effect and effectively suppress noise for a signal of a specific frequency.

Next, the results of measuring the off-track characteristics of this structure will be compared with those of the conventional example. It is known that the MR head having the conventional structure can easily pick up noise from adjacent tracks on one side. This is the MR when reproducing the MR head.
A bias is applied up to a so-called linearized region in which the magnetization direction M in the film is inclined in a direction of about 45 degrees, and when off-tracking to one side, a leakage magnetic field H substantially parallel to the magnetization direction M enters from an adjacent track. Although not much affected in the direction of M, when off-tracking to the other side, a leakage magnetic field H'which is substantially perpendicular to the magnetization direction M enters, which causes rotation of the magnetization M and becomes noise. The off-track characteristic of the MR head having the shield of the conventional structure is shown in FIG. Thus, it can be seen that the same head exhibits asymmetrical off-track characteristics. In comparison with this, the head of this structure is MR
Since the magnetic shield absorbs the leakage magnetic field from the lateral direction of the sensing unit, the crosstalk from the adjacent track is reduced, and FIG.
It has a symmetrical off-track characteristic as shown in FIG.

Further, in the head of the present invention, the vicinity of the MR element is covered with a magnetic shield layer of a conductor and is connected to Altic, and the slider and the magnetic shield which are processed into a desired shape for floating are electrically connected. The slider is mechanically and electrically connected to the gimbal on the back surface, and is further grounded. Therefore, it is more effective against electrostatic noise and the like than the conventional shield in which the shield is in an electrically floating state.

Further, the distance between the writing inductive head and the reproducing MR head can be made closer than that of the conventional structure by connecting the magnetic shield to the lower magnetic pole of the inductive head, and the leakage magnetic flux at the time of writing the inductive head. It is possible to improve the shield effect against the like.

Further, the shield of this structure has a head in which the tip of the MR head is processed to have a track width, or an MR head having a convex flux guide, and a yoke type M.
It can also be applied to the R head and has the above-mentioned shield characteristics,
Improvements in off-track characteristics and electrostatic characteristics were observed.
Further, since the magnetic shield is connected to the upper and lower yokes and the magnetic shield is provided with a notch, this acts as a reproducing gap.

[0023]

As described above, the magnetoresistive head according to the present invention can suppress off-track noise, crosstalk noise and the like by the effect of the shield shape, and can achieve high density and high resolution.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part of an MR head that is an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA ′ in FIG.

FIG. 3 is a plan view of an essential part of an MR head that is an embodiment of the present invention.

FIG. 4 is an off-track characteristic diagram of the head of the present invention and the head of the conventional structure.

FIG. 5 is a cross-sectional view of a main part of a conventional MR head.

[Explanation of symbols]

 1 MR head 2 Inductive head 3 Magnetic shield layer 4 Yoke 5 Protective film 6 MR electrode 7 Mask 8 Magnetic recording medium 9 Sliding surface 10 Altic substrate 11 Read gap 12 Vertical surface

Claims (2)

[Claims] 1. A non-magnetic conductive substrate having a sliding surface that slides on a magnetic recording medium and having a vertical surface perpendicular to the sliding surface; and a protective film formed on the vertical surface via a protective film. A magnetoresistive head comprising: a magnetoresistive film vertically provided on a sliding surface; and a magnetic shield layer provided near the periphery of the magnetoresistive film. A magnetoresistive head, wherein the layer is defined around the magnetoresistive film in parallel to the sliding surface and is connected to the non-magnetic conductive substrate. 2. The magnetoresistive head according to claim 1, wherein the depth of the magnetic shield layer from the sliding surface is greater than the depth of the magnetoresistive film from the sliding surface.