JPH04298805A - Thin-film magnetic head - Google Patents

Abstract

PURPOSE:To allow dealing with high-density recording of the magnetic recording medium by suppressing the generation of the popcorn noise in the conventional thin-film magnetic head without degrading recording and reproducing characteristics. CONSTITUTION:A pair of front and rear 1st and 2nd magnetic pole layers 4, 5 which cover a part of an insulating layer 2 integrally cladding a coil 1 having plural turns 10, 10... and the whole of a gap layer 3 successively provided on one side in the juxtaposition direction of the turns 10, 10... of the insulating layer 2 and have the end edge on the gap layer 3 side as a surface 8 facing the magnetic recording medium are constituted of a front end region A having an approximately specified width in plane view and a rear side region B which is provided successively with the front end region A and is increased in width toward the other side. The angle formed by both side edges in the transverse direction of the rear side region B and the above-mentioned surface 8 facing the medium is set in a 60 to 75 deg. range and further the 1st and 2nd magnetic pole layers 4, 5 are so formed that one or both have a negative magnetorestriction constant.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic head that records and reproduces information on a recording track of a magnetic recording medium such as a magnetic disk.

0002

BACKGROUND OF THE INVENTION With the expansion of the scope of use of computers in recent years, there has been an increasing demand for increased storage capacity and miniaturization of magnetic disk drives, which are widely used as external storage devices for these computers. Achieving high-density recording has become an important issue in order to meet these demands.

Such high-density recording is achieved by reducing the width of the recording track on a magnetic disk serving as a recording medium to increase the recording density in the radial direction, and by reducing the magnetization reversal interval in the longitudinal direction of the recording track. This is achieved by increasing the recording density in the direction, but along with this, the magnetic head that records and/or reproduces information on the recording track also has to perform recording and reproducing operations on narrow recording tracks. It is required to be able to perform recording without being affected by adjacent recording tracks, and thin-film magnetic heads are widely used as a device that can meet this requirement.

This thin-film magnetic head has extremely small magnetic poles, so it is possible to keep inductance low, and the accompanying increase in resonance frequency makes it possible to transfer information at high speed, and also to reduce the rise and fall times of recording current. Since the reversal time of the recording current can be shortened by shortening the recording current, it is possible to cope with an increase in recording density.Furthermore, it is possible to increase the signal-to-noise ratio (S/N ratio) by reducing impedance noise, realizing high-density recording. It has many advantages that are useful for

FIG. 6 is a plan view showing essential parts of a conventional thin film magnetic head, and FIG. 7 is an enlarged cross-sectional view taken along line VII--VII in FIG. As shown in both figures, the thin-film magnetic head includes a coil 1 having a plurality of turns 10, 10, etc. in one plane, which is encased in an insulating layer 2 made of thermosetting resin or the like. A gap layer 3 made of a non-magnetic material such as Al2O3 and having a substantially constant narrow width in plan view is successively provided on one side in the direction in which the turns 10, 10... are arranged in parallel, and all of the gap layer 3 and the insulating layer Both sides of part 2 are made of NiFe.
The coil 1 is coated with a first magnetic pole layer 4 and a second magnetic pole layer 5 made of an alloy or the like, and these magnetic pole layers 4 and 5 are coated with each turn 1 of the coil 1.
0, 10... are joined to each other at a joint 6 penetrating the insulating layer 2 on the other side in the juxtaposition direction to form a yoke 7, and these are connected to the slider 11 facing the recording surface R of the magnetic recording medium. Edges of the first and second pole layers 4 and 5 on the gap layer 3 side are adhered to one side end surface so as to constitute a surface 8 facing the recording surface R.

A problem with such a thin film magnetic head is a phenomenon in which the reproduced waveform and reproduced output become unstable when reproducing information, the so-called wiggle phenomenon. JP-A-55-101124 discloses that this can be suppressed by controlling the alloy composition of each part in layer 5 so that both layers 1 and 2 have a negative magnetostriction constant.

Furthermore, Japanese Patent Laid-Open No. 55-84019 discloses that the conversion efficiency during recording and reproduction of a thin film magnetic head is influenced by the planar shape of the yoke 7 constructed as described above. According to the publication, as shown in FIG. 6, the first and second magnetic pole layers 4 and 5 forming the yoke 7
a tip region A extending in the normal direction from the opposing surface 8 as a starting point and having a substantially constant width in plan view;
The rear region B is connected to the rear region B and gradually increases in width toward the other side, that is, toward the insulating layer 2 side, and is fan-shaped in plan view. The opposing surface 8
, that is, the angle formed with the recording surface R of the magnetic recording medium (side angle)
It is described that by setting θ in the range of 30° to 60°, the magnetic saturation level of the yoke 7 can be increased and the conversion efficiency can be improved.

[0008] On the other hand, ``Journal of the Japan Society of Applied Magnetics, Vol. 13, No. 2 (1989), PP99-102'' describes a magnetic pole layer composed of first and second magnetic pole layers 4 and 5 having a positive magnetostriction constant. As a result of a comparative experiment of the reproduction output when the side angle θ is 30°, 45°, and 60° for a thin film magnetic head equipped with the yoke 7, it was found that the maximum output was obtained when the side angle θ was 60°. It has been reported that a thin film magnetic head having a yoke 7 having a negative magnetostriction constant has a reduction in reproduction output as the side angle θ increases.

[0009]

[Problems to be Solved by the Invention] In addition to the above-mentioned problems, conventional thin-film magnetic heads suffer from pulsed noise having a peak value significantly higher than white noise with an appropriate time delay after the information recording operation. It is known that noise, so-called popcorn noise, occurs.
If this popcorn noise occurs during a playback operation following the recording operation, it may lead to operational errors.

[0010] The research report on popcorn noise is as follows:
“IEEE TRANSACTIONS ON MAG
NETICS, Vol. 25, NO. 5. SEPT
EMBER 1989, PP3212-3214, and according to this report, the probability of occurrence of popcorn noise decreases as the elapsed time after the recording operation increases. This can be solved by lengthening the time until the start, but this is not a desirable countermeasure because it runs counter to the demands for high-density recording and high-speed operation.

[0011] The generation of popcorn noise occurs when the first
, this is thought to be due to a time delay occurring in the change of the magnetic domain structure in the second magnetic pole layers 4 and 5. Focusing on this point, the present invention proposes a thin-film magnetic head that attempts to suppress the generation of popcorn noise itself. As far as I know, there are none.

The present invention has been made in view of the above circumstances, and proposes a yoke shape that can suppress the generation of popcorn noise in addition to improving the reproduction waveform, instability of the reproduction output, and conversion efficiency. An object of the present invention is to provide a thin film magnetic head having recording and reproducing characteristics.

[0013]

[Means for Solving the Problems] A thin film magnetic head according to the present invention includes an insulating layer that collectively covers a coil having a plurality of turns in one plane or in a plurality of planes, and each turn of the insulating layer. gaps that are continuous on one side in the direction in which the turns are arranged, each covering all of the gaps and a part of the insulating layer, and are joined to each other on the other side in the direction in which the turns are arranged to form a yoke. In a thin-film magnetic head comprising a pair of front and back magnetic pole layers, the edges of the magnetic pole layers on the gap side serving as a surface facing the magnetic recording medium, wherein both the magnetic pole layers have a substantially constant width in a plan view. An angle formed by both widthwise edges of the rear region and the opposing surface, which is composed of a tip region on the opposing surface side and a rear region that is connected to the tip region and increases in width toward the other side. is set in the range of 60° to 75°, and one or both of the magnetic pole layers has a negative magnetostriction constant.

[0014]

[Operation] In the present invention, the planar shape of a pair of magnetic pole layers that sandwich an insulating layer and a gap layer to form a yoke is set so that the side edges of their rear region and the surface of their tip region facing the recording medium are aligned. The generation of popcorn noise is suppressed by setting the angle (side angle θ) in the range of 60° to 75°, and in addition to this, one or both of the magnetic pole layers has a negative magnetostriction constant. do. Note that the side angle θ exceeding 75°
If a side angle θ of less than 60° is adopted, the conversion efficiency during recording and playback will decrease, and if a side angle θ of less than 60° is adopted, the probability of popcorn noise occurring will increase, the inductance will increase, and the resonant frequency will decrease. The available transfer rate will be reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to drawings showing embodiments thereof. FIG. 1 is a perspective view showing essential parts of a thin film magnetic head according to the present invention, and FIG. 2 is a plan view thereof. In the thin film magnetic head according to the present invention, as in the conventional case, a coil 1 having a plurality of turns 10, 10, .
A gap layer 3 having a substantially constant narrow width in plan view is provided in succession on one side in the juxtaposition direction of 10..., and the entire gap layer 3 and both sides of a part of the insulating layer 2 are connected to the first magnetic pole. Layer 4 and 2nd
While each is coated with a magnetic pole layer 5, these magnetic pole layers 4, 5
The turns 10, 10... of the coil 1 are joined to each other at a joint 6 penetrating the insulating layer 2 on the other side in the juxtaposition direction to form a yoke 7, which faces the recording surface R of the magnetic recording medium. The first and second magnetic pole layers 4 and 5 are arranged on one side end surface of the slider 11.
The edge of the gap layer 3 side forms a surface 8 facing the recording surface R.

The first and second magnetic pole layers 4 and 5 constituting the yoke 7 have a tip region A extending in the normal direction starting from the opposing surface 8 and having a substantially constant width in plan view; A rear region B that is connected to the tip region A and gradually increases in width toward the other side, that is, toward the insulating layer 2 side, and has a substantially fan shape in plan view.
It is equipped with A feature of the thin film magnetic head according to the present invention is that the angle between both edges of the rear region B and the opposing surface 8, that is, the recording surface R of the magnetic recording medium, that is, the side angle θ is 60° to
The angle is set within a range of 75°, and one or both of the first and second pole layers 3 and 4 has a negative magnetostriction constant.

The cross-sectional shape of the yoke 7 is as shown in FIG. A thin gap layer 13 is then formed on the surface of the tip region A of the first magnetic pole layer 4 using a non-magnetic material such as alumina (Al2O3). Side region B surface and the slider 11
An insulating layer 2 is formed on one end surface by enclosing a coil 1 having a plurality of turns 10, 10, etc. substantially orthogonal thereto at an extended portion of the tip region A, and finally, this insulating layer 2 and A second magnetic pole layer 5 is formed on the surface of the gap layer 3 in correspondence with the first magnetic pole layer 4, and the second magnetic pole layer 5 and the first magnetic pole layer 4 are connected to the turns 10, 10 of the coil 1. This is obtained by joining each other at a joining part 6 formed by cutting out a part of the insulating layer 2 on the other side.

The magnetostriction constants of the first and second magnetic pole layers 4 and 5 can be set by selecting the composition of the alloys constituting these. Two magnetic pole layers 4 and 5 are obtained.

Now, the inventor of the present invention has discovered that the unsolved problem in conventional thin-film magnetic heads, that is, the generation of popcorn noise, occurs when the first and second magnetic pole layers 4 and 5 are Considering that this is due to a time delay occurring in the change of the magnetic domain structure, the shape of the first and second magnetic pole layers 4 and 5 must be changed within a range that can maintain good recording and reproducing characteristics, especially the appropriate side angle θ. The aim is to reduce the probability of popcorn occurrence by selecting
A yoke 7 having a side angle θ of 0° is created, and the probability of occurrence of popcorn noise, recording/reproducing characteristics,
An experiment was conducted to investigate the playback output.

Note that both the first and second magnetic pole layers 4 and 5 are N
It is an iFe alloy, and the magnetostriction constant is set to -2×10 −6 by controlling its composition ratio. The thickness of the first and second pole layers 4 and 5 is approximately 3.3 μm, and the thickness of the gap layer 3 is approximately 0.0 μm.
4 μm, the width of the tip region A and the distance between the opposing surface 8 and the recording surface R are both approximately 12 μm, and the magnetic path length L, that is, the junction 6
The length in the normal direction between the coil 1 and the facing surface 8 is 140 μm, and the number of turns of the coil 1 is 24 turns.

FIG. 3 shows the relationship between the side angle θ and the incidence of popcorn noise. In addition, since the occurrence rate of popcorn noise is easily affected by the measurement conditions, the measurement conditions were strictly controlled and the write frequency was 9 MHz and the write current was 50 mA.
OP, writing time 0.5 msec, time from end of writing to start of reading 0.02 msec, read time 1.0 m
It was determined that popcorn noise occurred when noise having a level of 40 μVop or more was detected under the same conditions of sec.

As is clear from FIG. 3, the occurrence rate of popcorn noise starts to decrease when the side angle θ exceeds 50°, and thereafter decreases as the side angle θ increases until it reaches 75°.
It becomes approximately 0 in a range exceeding . Therefore, it can be seen that increasing the side angle θ is effective in suppressing the generation of popcorn noise.

FIG. 4 shows the relationship between the side angle θ and the recording/reproducing characteristics. Note that this is an overwrite characteristic at a position with a radius of 35 mm on a 1350 Oe sputter medium of a magnetic disk rotating at 3600 rpm, and the separation distance between the recording surface R and the opposing surface 8 of the yoke 7 is
It is 0.145±0.005 μm. The evaluation of the overwrite characteristics was performed by overwriting a track that had already been written at 3MHz at 8MHz.
The procedure was to examine the amount of attenuation occurring in the write signal at Hz, and the recording current magnetomotive force was selected under conditions that would allow the yoke 7 to saturate sufficiently.

As is clear from this figure, the amount of attenuation of the previously recorded signal during overwriting is
It is substantially constant for the side angle θ in the range of 30° to 75°, rather than the range of 30° to 60° as shown in Publication No. 019, and the upper limit is 75° without deteriorating the recording characteristics. It can be seen that the side angle θ can be adopted as follows.

FIG. 5 shows the relationship between the side angle θ and the reproduction output. The reproduction output was measured at various frequencies, and FIG. 5 shows the results at each frequency of 1, 3, 8, and 12 MHz. As is clear from this figure, the reduction in reproduction output at each frequency occurs in the range where the side angle θ exceeds 75°, and the upper limit of the side angle θ in terms of reproduction characteristics is also 75°.
It turned out to be 5°.

According to the results of the above experiments, it is possible to adopt a side angle θ in the range of 30° to 75° from the viewpoint of recording and reproducing characteristics, and from the viewpoint of the occurrence rate of popcorn noise, it is possible to adopt a side angle θ in the range of 30° to 75°.
It is clear that it is desirable to adopt a side angle θ of 60° to 75°, and in the thin film magnetic head according to the present invention having a side angle θ in the range of 60° to 75°, the popcorn The generation of noise can be effectively suppressed.

Further, as a result of more detailed experiments, the recording current magnetomotive force at which the yoke 7 is sufficiently saturated is determined when the side angle θ is 30° to 30°.
It is clear that it is approximately constant in the range of 60° and increases slightly when it reaches 75°. Under a constant recording current magnetomotive force, the recording characteristics change in the range where the side angle θ is 60° to 75°. However, this decrease can be eliminated by optimizing the recording current magnetomotive force, and the side angle θ of 30° to 60° can be reduced.
It is possible to obtain recording characteristics equivalent to those obtained by having the following.

[0028]

As detailed above, in the thin film magnetic head according to the present invention, the angle between the rear region of the pair of magnetic pole layers and the surface facing the magnetic recording medium is set in the range of 60° to 75°. Furthermore, by making one or both of the magnetic pole layers have a negative magnetostriction constant, the generation of popcorn noise can be effectively suppressed, and the recording and reproducing characteristics can be maintained at a high level. The present invention has excellent effects such as being able to meet demands for density recording.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a thin film magnetic head according to the present invention.

FIG. 2 is a plan view of a thin film magnetic head according to the present invention.

FIG. 3 is a graph showing the relationship between the side angle θ and the incidence of popcorn noise.

FIG. 4 is a graph showing the relationship between side angle θ and recording/reproducing characteristics.

FIG. 5 is a graph showing the relationship between side angle θ and reproduction output.

FIG. 6 is a plan view of a conventional thin film magnetic head.

FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6;

[Explanation of symbols]

1 Coil 2 Insulating layer 3 Gap layer 4 First magnetic pole layer 5 Second magnetic pole layer 6 Joint part 7 York 8 Opposite surface A Tip area B Posterior area

Claims (1)

[Claims] 1. An insulating layer that collectively encloses a coil having a plurality of turns in one plane or in a plurality of planes, and a gap continuous on one side in a direction in which the turns of the insulating layer are arranged side by side.
covering all of the gap and a part of the insulating layer, respectively;
A pair of front and back magnetic pole layers that are joined to each other on the other side in the direction in which the turns are arranged to form a yoke, and edges of these magnetic pole layers on the gap side serve as a surface facing the magnetic recording medium. In the thin film magnetic head, each of the magnetic pole layers has a tip region on the opposing surface side having a substantially constant width in plan view;
and a rear region that is connected to the tip region and increases in width toward the other side, and the angle between the opposite sides in the width direction of the rear region is in the range of 60° to 75°. 1. A thin film magnetic head characterized in that one or both of the magnetic pole layers has a negative magnetostriction constant.