JPH01138607A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To eliminate the generation of a contour effect and a false pulse to occur at the time of traveling a recording medium by providing a first area and a second area in which a permeability is changed from the gap corresponding surface of a pole piece to the rear surface of the thickness direction gap surface. CONSTITUTION:Pole pieces 1 and 2 to sandwich a gap 3 are composed of the first areas 1a and 2a connected to a gap 3 and the second areas 1b and 2b at the outside respectively. The first areas 1a and 2a have the high permeability, and the second areas 1b and 2b are constituted so that the permeability can be continuously reduced from a boundary 1c or 2c toward the outside. By such a constitution, the permeability is continuously changed on a magnetic head sliding surface, the steep break of a magnetic body is eliminated at the time of traveling a recording medium, and the problems such as a contour effect and a false pulse can be resolved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel structure of a ring-type thin film magnetic head.

Conventional technology The general structure of a conventional ring-type thin film magnetic head is as follows:
It is as shown in FIG. 5, and is composed of a lower magnetic layer 1, an upper magnetic layer 2, a gap 3, a thin film coil 4, and the like.

One of the characteristics of such a thin film head when compared to a bulk head is that the pole piece thicknesses 5a and 5b have a finite length when considering dimensions on the order of recording wavelength. A head with such a finite ball length has the advantage that the head magnetic field distribution in the direction in which the recording medium runs is sharper than that of a bulk head, resulting in less recording demagnetization. It is known that there are problems such as the outer edges 6a and 6b of the pole piece have recording and reproducing sensitivity, and pseudo pulses are generated in the reproduced signal.

One known method for solving this problem is to eliminate the portions of the outer edge lines 7a, 7b of the pole pieces that are parallel to the gap line, as shown in FIG. Note that this figure shows the recording medium sliding surface of the head. By doing this, the contour effect is
The contour effect, which differs for each minute area, is canceled out as a result of being integrated over 8〉 in the track width direction, and the spurious pulses can be ignored by becoming a collection of minute pulses that are temporally dispersed in each minute area. Become. However, with normal thin film technology, it is difficult to form a thin film so that the bottom and top surfaces are non-parallel, so some pre-processing and post-processing are required, which complicates the manufacturing process.

FIG. 7 shows yet another solution.

This figure shows a partial sectional view of the vicinity of the tip of the pole piece of the head. Here, by processing the sliding surface into the shape shown in the figure, the magnetic material of the pole piece gradually separates from the recording medium 9, and the outer edges 6a and 6b become concave portions and are completely separated from the recording medium 9. They seem to be leaving. This eliminates abrupt discontinuities in the magnetic material on the sliding surface, which can cause contour effects and spurious pulses.However, considering that the pole piece thickness is usually about a few microns, such The processing itself is not easy, and there are also problems such as magnetic powder falling off from the recording medium that accumulates in the grooves of the used soil, and concavities disappearing due to wear on the sliding surfaces.

Problems to be Solved by the Invention As described above, thin-film magnetic heads have problems such as contour effects and spurious pulses caused by the finite ball length, and conventional techniques have not been able to provide effective solutions to these problems. .

Means for Solving the Problems In the present invention, a pole piece is provided with a first region having a high magnetic permeability from a surface facing the gap to a certain depth in the thickness direction of the pole piece, and a region in contact with the first region having a high magnetic permeability. It is constituted by a second region in which the distance decreases continuously and reaches the back surface of the gap surface.

Operation: With this configuration, the magnetic permeability changes continuously on the sliding surface of the magnetic head, eliminating abrupt discontinuities in the magnetic material, thereby eliminating problems such as contour effects and spurious pulses. Furthermore, since the second region is more semi-hard magnetic than the first region, if magnetic anisotropy with an easy axis of magnetization in the track width direction is given here, this will be different from that of the first region. An extremely useful side effect is also produced that the anisotropy in the track width direction of the first region is easily maintained stably by acting like a magnetic biasing means for the region. As a result, even when the track width is narrow, the anisotropy of the first region can be maintained stably, and a magnetic head with excellent high frequency characteristics can be obtained.

Embodiment FIG. 1 is a sectional view showing the tip of a thin film magnetic head according to a first embodiment of the present invention. Here, each of the pole pieces 1.2 sandwiching the gap 3 consists of a first region 1a, 2a in contact with the gap, and a second region 1b, 2b outside the first region 1a, 2a. Here, the first region 1a,
2a is a portion having high magnetic permeability, and the second region 1
b and 2b are portions in which the magnetic permeability continuously decreases outward from the boundary 1c or 2c. Ideally, the first area and boundary 1c and 2c are
It is desirable that the magnetic permeability of the first region and the second region is continuous, and that the magnetic permeability of the second region is substantially reduced to 1 at least at the outer boundary positions 1d and 2d. .

More specifically, the pole piece 1 is formed by, for example, a sputtered film of sendust, permalloy, or an amorphous magnetic alloy in a film forming direction 11. The film is formed while changing the composition ratio from the boundary 1d to the boundary 1c, and with a constant high magnetic permeability composition from the boundary 1c to the gap surface. Conversely, in the pole piece 2, the film is formed with a constant composition from the gap surface to the boundary 2c, and with a varying composition ratio from the boundary 2c to 2d. To do this, for example, the film forming apparatus may be of a multi-target type, and the ratio of power input to each target may be changed. Naturally, the composition ratio is changed so that the magnetic permeability changes as described above. Further, it is desirable that the first region and the second region are continuous in the film forming process.

With the structure of the thin film magnetic head as described above, the magnetic permeability of the pole piece portion changes continuously from the high magnetic permeability portion to the non-magnetic portion from the vicinity of the gap toward the outside. Therefore, since there is no sharp discontinuity in the magnetic material on the sliding surface, the problem of contour effects and spurious pulses can be solved.Next, using FIG. Explain. Here, the composition of the second regions 1b and 2b is assumed to be such that another element is added to the composition of the first region (high magnetic permeability composition), and the magnetic permeability is changed by changing the addition ratio. There is. For example, when forming the pole piece by sputtering with a magnetic film similar to that in the first embodiment, when film formation starts at the boundary 1d, oxygen or nitrogen is generated in the sputtering gas (argon) to the extent that the film becomes non-magnetic. After that, the degree of contamination is gradually reduced,
From the boundary 1c onwards, the original high magnetic permeability film is formed. The same applies to the subsequent film formation on the pole piece 2 portion.

FIG. 2 is a partial sectional view showing a third embodiment of the present invention. Here, a diffusion layer 10 (for example, a thin film of gold or Au) is further provided on the outside of the pole piece. After forming each layer in FIG. 2 (pole piece 1.2 is a film with high magnetic permeability over the entire thickness), by performing extensive heat treatment, the diffusion layer 10 is diffused into pole piece 1.2, thereby making it permeable. Second regions 1b and 2b are formed in which the magnetic constant changes continuously.

FIG. 3 shows a fourth embodiment of the invention. Here, the head sliding surface is shown. The first and second regions of the pole piece are formed as shown in each of the above embodiments, but in particular, the second regions 1b and 2b are given anisotropy with an axis of easy magnetization in the track width direction. It is being In the figure,
Arrow 12 represents the direction of magnetic anisotropy. Here, since the second region with low magnetic permeability includes a part that is more magnetically hard (semi-hard) than the first region, when magnetic anisotropy in the track width direction is given to this region, This acts like a magnetic bias applied by a hard magnetic film to the first region, making it easier to maintain stable anisotropy in the track width direction in the first region. In addition to the original effects of the present invention, the first regions 1a, 2a (
In other words, it can have a great effect on stabilizing the magnetization state of the main head magnetic path.

As is already known, in thin-film magnetic heads, the thin-film core (pole piece) is generally given anisotropy with an axis of easy magnetization in the track width direction, so that the direction in which the recording and reproducing magnetic flux passes is the axis of hard magnetization. However, as magnetic recording tracks become narrower, the ratio of (ball thickness)/(track width) becomes thicker, resulting in a narrower magnetic field in terms of demagnetizing field. It becomes difficult to maintain the axis of easy magnetization of the pole piece of the track in the track width direction.In order to deal with this situation, in this fourth embodiment, a second magnet having anisotropy in the track width direction is used. Area 1b, 2
Since magnetization b is adjacent to the first regions 1a and 2a, the magnetization in the track width direction of the first region can exist more stably.

FIG. 4 shows a sliding surface of a thin film head according to a fifth embodiment of the present invention. In this example, the composition distribution in the thickness direction of the pole piece is basically the same (the magnitude of the magnetic anisotropy imparted in the track width direction of the second regions 1b and 2b increases as it approaches the back surface of the pole piece). As a result, the magnetic permeability in the head magnetic path direction (perpendicular to the plane of the paper) decreases as it approaches the back surface of the pole piece. Furthermore, the first regions 1a and 2a are given relatively small anisotropy that allows high magnetic permeability to be obtained.

In the figure, the direction and magnitude of arrow 12a represent the direction and magnitude of magnetic anisotropy. To actually continuously change the magnitude of anisotropy in the thickness direction, for example, there is a method of continuously changing the substrate temperature in the deposition of permalloy in a magnetic field. With this configuration as well, a thin film head free from the problems of contour effects and spurious pulses can be obtained, similar to the embodiments described above. Furthermore, even during narrow tracks, the presence of the second region having strong anisotropy makes it easy to maintain the anisotropy of the first region in the track width direction.

Effects of the Invention According to the present invention, it is possible to obtain a thin film magnetic head that is free from problems such as contour effects and spurious pulses (and is capable of stably maintaining high frequency characteristics even during narrow tracks).

[Brief explanation of the drawing]

1 to 2 are partial cross-sectional views of thin film magnetic heads showing first to third embodiments of the present invention, and FIGS. 3 to 4 show fourth to fifth embodiments of the present invention. A front view of a sliding surface of a thin film magnetic head, and FIGS. 5 to 7 are a sectional view, a front view, and a partial sectional view, respectively, illustrating a thin film magnetic head according to the prior art. ■...Lower magnetic layer, 2...Upper magnetic layer, 1a, 2a
...first region, 1b, 2b...second region, 3.
... Gap, 4... Coil, 8... Track width direction, 9... Magnetic recording medium, 10... Diffusion layer. Name of agent Patent attorney Toshio Nakao 1 person 1-m-lower magnetism 1 (Zul C-S) 2nd figure 1', j 203 4th figure 2a 5th part 6th figure 7th figure

Claims (6)

[Claims] (1) In a thin film magnetic head having a pole piece made of a magnetic thin film, the pole piece has a first region having high magnetic permeability from a surface facing the gap to a certain depth in the thickness direction, and a region in contact with the first region having high magnetic permeability. A thin film magnetic head comprising: a second region in which the magnetic field is continuously decreased; (2) The thin film magnetic head according to claim 1, wherein the second region has the same composition as the first region, and the composition ratio changes continuously. (3) The composition of the second region is obtained by adding another component to the composition of the first region, and the addition ratio of the other component changes continuously. The thin film magnetic head according to item 1. (4) The pole piece further has a diffusion layer adjacent to the back surface of the gap-opposed surface, and the other component in the second region is a diffusion component from the diffusion layer. The thin film magnetic head described in . (5) The thin film magnetic head according to claim 1, wherein the second region is provided with magnetic anisotropy having an axis of easy magnetization in the track width direction. (6) The second region is given magnetic anisotropy with an axis of easy magnetization in the track width direction, and the magnetic permeability of the second region can be changed by changing the magnitude of the magnetic anisotropy. The thin film magnetic head according to claim 1, characterized in that the thin film magnetic head is changed.