JPH1125424A - Magnetic field application device - Google Patents

Abstract

(57) [Summary] (With correction) [PROBLEMS] To realize a magnetic head with low noise and good responsiveness, a magnetic field applying device capable of applying a magnetic field distribution having desired strength and parallelism at the time of plating film formation is realized. SOLUTION: In a magnetic field applying device used in a magnetic pole plating film forming step of a magnetic head, rare earth magnets 1a and 1b are opposed to each other with a plating tank interposed therebetween, and the magnets are connected with a yoke 5 to form the magnet. The thickness of the central part is smaller than the thickness of the outer peripheral part, and a plurality of adjusting holes 4 are provided on the magnet surface, and a magnet or a magnetic material is inserted into the adjusting hole 4 to adjust the magnetic field distribution of the air gap. apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field applying apparatus, and is most suitable for use in a thin film forming process of a thin film head of a magnetic head used for reading and writing signals of a hard disk drive.

[0002]

2. Description of the Related Art Various magnetic heads are used to read magnetic signals written on a recording medium of a hard disk drive (hereinafter referred to as HDD). Inductive heads are commonly used because they can perform both writing and reading of signals. Induction heads include ferrite heads and MIG heads (Metal in Gap Hea
d; a composite head in which a metal thin film is laminated in the gap of a ferrite head) and a thin film head. Currently, HDDs commonly use MIG heads and thin film heads. On the other hand, an MR head (Magnet Resistive Head) has begun to be used as a signal read-only head. MR
Since the head can read out signals regardless of the peripheral speed, it is suitable for high recording density and small diameter of HDDs, and the number of heads used recently is increasing rapidly. GMR head (Giant Magnet
o-resistive Head) is also being actively developed as a next-generation head. Because the MR head is read-only,
Used in combination with an inductive thin-film magnetic head for writing. FIG. 2 is a schematic sectional view of an example of the element structure of the thin film / MR composite head. Permalloy (Fe-Ni alloy) is often used as the magnetic pole material for both the thin film head and the MR head. Since the permalloy magnetic pole of the MR head requires a thickness on the order of microns, a plating method having an excellent film forming speed is used. The present invention particularly relates to the formation of a thin-film head magnetic pole formed by a plating method. Thin film /
The schematic configuration of the MR compound head is as shown in FIG.
FIG. 3A shows the magnetic pole portion of the thin film head. In particular, the orientation of permalloy in the magnetic pole head is important. The permalloy of the magnetic pole head preferably has a magnetic domain structure as shown in FIG. This is because, in the case of a magnetic domain structure having an easy axis of magnetization in the longitudinal direction of the head magnetic pole as shown in FIG. 4A, the magnetic domain wall moves due to the leakage magnetic field from the recording medium, and magnetization reversal occurs. The domain wall moves discontinuously while being locally trapped at a pinning location where the domain wall energy is low. This causes Barkhausen noise. In addition, since the moving distance of the domain wall for the magnetization reversal is long, there is a problem that the magnetic field response to the write signal is delayed. On the other hand, when an easy axis is provided in the width direction of the magnetic pole portion as shown in FIG. 4B, simultaneous rotation of magnetization occurs due to a leakage magnetic field from the recording medium, and magnetization reversal is performed. The simultaneous rotation of magnetization is continuous and smooth, and the reversal speed is high, so that problems such as domain wall movement (barkhausen noise, signal response delay, etc.) do not occur. Particularly, since the data transfer rate is required to be further improved in the future, the carrier frequency of the signal is further improved, and the magnetic field response is required to be further improved. Therefore, after forming and processing the permalloy film, FIG.
The film quality must be improved so that the magnetic field orientation as described above can be obtained.

In order to obtain a magnetic field orientation as shown in FIG. 4 (b), it is common practice to apply a magnetic field when forming a permalloy film. It is known that the axis of easy magnetization is oriented in the direction of the magnetic field (induced magnetic anisotropy). However, it is not easy to apply a parallel and uniform magnetic field to the entire surface of the head substrate. When the parallelism of the applied magnetic flux is disturbed, the axis of easy magnetization of the permalloy film is also disturbed, so that domain wall movement is mixed with simultaneous magnetization reversal. Further, the distribution of the applied magnetic field also affects the thickness and the degree of orientation of the permalloy.
If the magnetic field strength is strong and uniform, the film quality is improved, which is desirable. However, when the magnetic field strength is 300 G or more, the influence of the non-uniformity of the magnetic field strength on the degree of orientation decreases, and it is not possible to increase the magnetic field strength indefinitely. It is desired to make the magnetic flux parallelism uniform. The present inventors propose a permanent magnet type magnetic field applying device for realizing a desirable magnetic field distribution (intensity and parallelism).

[0004]

In order to realize a thin film head with low Barkhausen noise and good responsiveness, a magnetic field applying device capable of applying a desired magnetic field distribution during NiFe plating film formation has been expected.

[0005]

Means for Solving the Problems In view of this point, the present inventors have conducted intensive studies and ascertained the influential factors, and realized an applied magnetic field and a formed NiFe magnetic film in order to realize a desirable magnetic field distribution. The present inventors have completed the present invention by examining the relationship between the two and extracting factors affecting magnetic domain generation. That is, the present invention relates to a magnetic field applying device used in a magnetic pole plating film forming step of a magnetic head, the device facing a rare earth magnet across a plating tank,
The magnets are joined by a yoke, the thickness of the magnet is thinner at the center than the thickness of the outer periphery, the magnet has a plurality of adjustment holes, and a magnet or a magnetic material is inserted into this hole to form a gap. The magnetic field distribution is adjusted. This will be described in more detail below.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS It is known that magnetic field-induced induced magnetic anisotropy occurs in a NiFe alloy, and is called a directional order mechanism. It is not always clear whether uniaxial anisotropy is generated by the same mechanism in the process of forming the NiFe magnetic film by plating, but it has been confirmed that the quality of the applied magnetic field is effective in improving the quality of the permalloy film. If a constant induced magnetic anisotropy can be obtained stably by applying a magnetic field, Barkhausen noise can be reduced.

In the step of forming a plating film in a magnetic field, the intensity of the magnetic field and the degree of the induced magnetic anisotropy are proportional to each other. Therefore, the magnetic field strength may be 300G to 1000G, more preferably
300G to 800G. If the magnetic field strength is within this range, the influence of the magnetic field gradient on the distribution of uniaxial anisotropy will be small, but if a uniform magnetic field strength is realized with the lowest possible magnetic field strength, a large effect can be obtained with a small amount of magnets. Can be. On the other hand, since the angular distribution of the magnetic flux greatly affects the distribution of the uniaxial anisotropy, it is desirable that the angular distribution be as small as possible within the range of the substrate inserted into the plating bath. Therefore, as the angle of the magnetic flux, it is desirable that the distribution of the angle between the magnetic fluxes in a space having a diameter of 100 mm in the center plane space of the air gap within the substrate surface is within 5 °. This is because, when it is greater than that, the directional regular arrangement gradually starts to be disturbed, and the degree of uniaxial anisotropy decreases and varies. The present invention proposes a magnetic field applying apparatus that reduces the applied magnetic field angle distribution during NiFe film formation based on the above findings.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the magnetic field application device of the present invention. The figure sandwiches a plating tank (not shown) inserted into the space 8,
This is a magnet-facing magnetic circuit in which the rare-earth permanent magnets 1a and 1b are opposed to each other and the opposed magnets are connected by a yoke 5. The basic magnetic circuit itself is already known, and the present invention relates to an improvement of the magnetic circuit. The feature of the permanent magnet type magnetic field applying device of the present invention is that, in order to make the angular distribution of the magnetic flux 9 in the air gap 8 parallel, the shape of the magnets 1a and 1b is not a simple plate magnet, but a relatively thick magnet at the center. The idea is to make the magnet thinner and thicker toward the end. By providing the magnet thickness distribution, it is possible to prevent the lines of magnetic force in the vicinity of the magnet end portions from expanding outward, thereby improving the angle distribution of the magnetic flux. Where the diameter of the center space of the air gap is 100mm
It is desirable that the distribution of the angle between the magnetic fluxes in the space is adjusted within 5 °. It is most desirable that the thickness of the magnets 1a and 1b be changed continuously. However, since it is difficult to manufacture individual magnets in manufacturing, it is practical to change the thickness stepwise (for example, step 7 in FIG. 1). The number of stages may be at least two as shown in FIG. 1, but if it is larger, it is easy to realize a parallel magnetic field in a wider range. On the other hand, in consideration of ease of manufacturing, it is desirable that the number be within 5 steps. In the present invention, in addition to the yoke 5 connecting the opposed magnets 1a and 1b, a non-magnetic support 6 is provided so that the back yoke 2 does not fall due to the attractive force between the magnets.

In addition to the improvement of the magnet shape, a plurality of adjustment holes 4 are provided at positions corresponding to the circumference of the magnet center.
This diameter is desirably 2 to 10 mm. By inserting a permanent magnet or a ferromagnetic material (not shown) into the adjustment hole 4, the magnetic flux angle distribution can be improved to be more parallel. The number of the adjustment holes 4 may be four or more on one side. Since the substrate wafer to be inserted into the plating tank has a disk shape, it is practically sufficient that even number of holes is 20 or less, preferably 10 or less. The adjustment hole 4 does not necessarily need to be provided in a circumferential shape,
Also, it is not always necessary to penetrate. It is also effective to provide an adjustment hole at the center of the magnet.

It is desirable that the magnetic field distribution be as smooth as possible on the wafer surface of the plating tank in the plating step.
Therefore, this can be realized by attaching the magnetic shunt plate 3 having a magnetic shunt function to the magnets 1a and 1b. The magnetic shunt plate may be any soft magnetic material, such as iron, ferrite, silicon steel sheet,
Permalloy, a composite soft magnetic material, and the like are included. The thickness of the magnetic shunt plate varies depending on the material, so it cannot be said unconditionally.
If it is less than 10 mm, there is no effect due to magnetic saturation, and if it exceeds 10 mm, the magnetic efficiency is reduced. When the width of the plating tank is large (for example, 500 mm or more), a smooth magnetic field distribution can be obtained without attaching the magnetic pole material to the magnet surface.

Although any permanent magnet can be used, it is desirable to use a rare earth magnet because the gap between the opposed magnets is large. Suitable rare earth magnets are SmCo-based sintered magnets and NdFeB-based sintered magnets. Since it is used in a wet plating process, it is desirable to coat a rare earth magnet with a corrosion resistant film in consideration of corrosion resistance.

The magnetic field applying apparatus of the present invention makes it possible to realize a magnetic field strength of 300 G or more within a magnetic flux parallelism of 5 ° or less. It has become possible to manufacture a thin film head with low noise and good responsiveness.

[0013]

Next, the present invention will be described with reference to examples. Example As shown in FIG. 1, NdFeB sintered magnet (Shin-Etsu Chemical Co., Ltd.
Product name N-42) Distance for inserting plating tanks for 1a and 1b
They were opposed to each other via a gap 8 of 300 mm. These magnets were previously plated with Ni to form a corrosion-resistant film. Magnet size is 3
00mm x 300mm square, center thickness is 15mm, peripheral thickness is
It has a two-stage structure of 25 mm. As a magnetic shunt plate 3 on the surface of the magnet,
An iron plate (S400) having a thickness of 5 mm was attached. The magnets 1a and 1b are connected with a yoke 5 to form a magnetic circuit, which is 80 mm from the center of the magnet.
An iron bolt (M5) was inserted into the eight adjustment holes 4 provided on the circumference of the circle, and a SUS support 6 was provided so that the back yoke 2 would not fall down, thereby producing a permanent magnet type magnetic field applying device. As for this magnetic field applying device, when the magnetic field distribution in a space of 100 mm was measured at the center of the gap between the magnets, the magnetic field intensity was 520 G on average.
In the plane of the board (100mm diameter), it is within 30G.
In addition, the angle between magnetic fluxes in this space was within 4.4 °, and it was confirmed that the angle was optimal for use in applying a magnetic field in a plating process of a thin film head.

[0014]

According to the magnetic field applying apparatus of the present invention, in the step of forming the magnetic film of the thin film head by plating, the magnetic field strength of 300 G or more can be realized with the magnetic flux parallelism within 5 °. Thus, the effect of the magnetic field makes it possible to manufacture a thin film head having good characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of a magnetic field application device of the present invention.

FIG. 2 is a schematic diagram showing a cross section of a combined head of an inductive thin-film magnetic head and an MR head.

3A is a schematic cross-sectional view of a permalloy magnetic pole of a thin film head, and FIG. 3B is a schematic diagram of a magnetic domain pattern at a tip end of FIG.

4A is a schematic diagram of magnetization reversal due to magnetic wall movement of a magnetic pole tip, and FIG. 4B is a schematic diagram of magnetization reversal due to simultaneous rotation of a magnetic pole tip.

[Explanation of symbols]

1a, 1b {Rare earth permanent magnet 2}
‥‥ Back yoke 3 ‥‥‥‥‥ Magnetic shunt 4 ‥‥‥
調整 Adjustment hole 5 ‥‥‥‥‥ Yoke 6 ‥‥‥
支 え Support 7 ‥‥‥‥‥ Step 8 ‥‥‥
‥‥ air gap 9 ‥‥‥‥‥ magnetic flux

Claims (2)

[Claims] In a magnetic field applying apparatus used in a magnetic pole plating film forming step of a magnetic head, the apparatus is configured such that a rare earth magnet is opposed to a plating tank and the magnets are connected by a yoke. Is thinner at the center than at the outer periphery,
A magnetic field applying apparatus having a plurality of adjusting holes, and adjusting a magnetic field distribution in a gap by inserting a magnet or a magnetic material into the adjusting holes. 2. The magnetic field applying apparatus according to claim 1, wherein two to five steps for changing the thickness of the magnet in a stepwise manner are provided, and a soft magnetic thin plate having a thickness of 0.1 to 10 mm is provided on the surface of the magnet. A magnetic field applying device in which the distribution of the angle between magnetic fluxes in a space having a diameter of 100 mm in the center space of the gap is adjusted to be within 5 °, and the magnetic field intensity is 300 to 1000 G.