Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2002-04-29
2004-05-18
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S119050
Reexamination Certificate
active
06738223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to thin-film magnetic write heads for use in, for example, floating thin-film magnetic heads. Particularly, the present invention relates to a thin-film magnetic head having a small gap depth (Gd), which is free from side writing.
2. Description of the Related Art
FIG. 28
is a longitudinal sectional view of a conventional thin-film magnetic write head. As shown in
FIG. 28
, the conventional thin-film magnetic write head comprises a lower core layer
10
made of a magnetic material such as a NiFe alloy and a gap layer
11
made of Al
2
O
3
or SiO
2
formed on the lower core layer
10
.
Referring to
FIG. 28
, a gap depth (Gd) defining layer
12
is formed at a position on the gap layer
11
a predetermined distance L
1
behind in the height direction, i.e., the Y direction in the drawing, relative to the face opposing a recording medium. The Gd defining layer
12
is composed of an organic insulative material such as resist, for example. The predetermined distance L
1
is the gap depth (Gd).
Referring to
FIG. 28
, an upper magnetic pole layer
13
made by plating using a magnetic material such as a NiFe alloy extends from the face opposing the recording medium to the top of the Gd defining layer
12
while overlaying the gap layer
11
and the Gd defining layer
12
with a plating base layer
13
a
therebetween. An insulating layer
14
composed of Al
2
O
3
or the like is formed behind the upper magnetic pole layer
13
in the height direction.
A coil layer (not shown) is formed on the insulating layer
14
, and an insulating layer
18
composed of an organic insulative material or the like is formed on the insulating layer
14
so as to cover the coil layer.
Referring to
FIG. 28
, an upper core
15
is plated over the upper magnetic pole layer
13
, the insulating layer
14
, and the insulating layer
18
using a magnetic material such as a NiFe alloy.
FIG. 29
is a perspective view showing the structure of the vicinity of the face of the thin-film magnetic head opposing the recording medium shown in FIG.
28
. The drawing of
FIG. 29
is a schematic illustration and the upper core
15
, for example, is omitted from the drawing.
As shown in
FIG. 29
, the lower core layer
10
at the two sides of the upper magnetic pole layer
13
in the track width direction, i.e., the X direction in the drawing, is milled to form recesses
16
.
Referring to
FIG. 29
, a lower magnetic pole section
10
a
protruding from the upper surface of the lower core layer
10
is formed under the Gd defining layer
12
. The lower magnetic pole section
10
a
is also under the upper magnetic pole layer
13
. The width of the lower magnetic pole section
10
a
in the track width direction at a position below the upper magnetic pole layer
13
is the same as the track width Tw and is substantially the same as the width of the upper magnetic pole layer
13
.
In this conventional head, a recording magnetic field is mainly generated between the upper magnetic pole layer
13
and the lower magnetic pole section
10
a
and leaks from the face of the head opposing the recording medium. Since the lower magnetic pole section
10
a
protrudes from the surface of the lower core layer
10
toward the upper magnetic pole layer
13
, top faces
10
b
of the lower core layer
10
are distant from the upper magnetic pole layer
13
. This distance promotes generation of a recording magnetic field between the upper magnetic pole layer
13
and the lower magnetic pole section
10
a,
both having the track width Tw, thereby suitably inhibiting the occurrence of side fringing.
Trends toward higher recording densities demand narrower tracks and smaller gap depths. In order to prevent magnetic saturation, decrease in recording current is also necessary. Since a combination of a large gap depth (Gd) and decreased recording current causes drastic reduction in magnetic flux generated between the upper magnetic pole layer
13
and the lower magnetic pole section
10
a,
the gap depth (Gd) is preferably small.
In view of the above, conventionally, the Gd defining layer
12
is arranged near the face opposing the recording medium so as to shorten the gap depth L
1
, as shown in FIG.
29
. The gap depth L
1
is, for example, 0.6 &mgr;m or less.
However, the thin-film magnetic head shown in
FIG. 29
, which has a decreased gap depth L
1
, suffers from the following problems.
Referring to
FIG. 29
, the Gd defining layer
12
protrudes from the two sides of the upper magnetic pole layer
13
in the track width direction, i.e., the X direction in the drawing. The protruding Gd defining layer
12
functions as a mask for forming the recesses
16
by milling the lower core layer
10
with ions and allows the portion of the lower core layer
10
under the Gd defining layer
12
to remain intact during milling with ions. Thus, similarly to the Gd defining layer
12
, the resulting lower magnetic pole section
10
a
protrudes from the two sides of the upper magnetic pole layer
13
in the track width direction. The portion of the lower core layer
10
protruding from a side of the upper magnetic pole layer
13
is referred to as a protuberance
10
a
1
. The distance between the face opposing the recording medium and the protuberance
10
a
1
is substantially the same as the gap depth, which is represented by L
1
.
Since the protuberance
10
a
1
under the Gd defining layer
12
protrudes from the upper magnetic pole layer
13
in the track width direction, the protuberance
10
a
1
has a large cross-section taken in the direction parallel to the face opposing the recording medium. As a result, the demagnetizing field is strong at the protuberance
10
a
1
.
At a large gap depth L
1
, the demagnetizing field of the protuberance
10
a
1
hardly causes any problem because the protuberance
10
a
1
is distant from the face opposing the recording medium in the height direction, i.e., the Y direction in the drawing. However, at a small gap depth L
1
, the distance between the protuberance
10
a
1
and the face opposing the recording medium is decreased, resulting in generation of a leakage magnetic field between the upper magnetic pole layer
13
and the protuberance
10
a
1
.
Since the width of the protuberance
10
a
1
in the track width direction is larger than the track width Tw, the protuberance
10
a
1
also writes data and thus cause side writing.
FIG. 30
is a graph showing a track profile, i.e., an output profile in the cross-track direction, taken by actually reading data written on a recording medium using a magnetoresistive (MR) head comprising the thin-film magnetic head shown in FIG.
29
. In this experiment, data was recorded using the thin-film magnetic head having a skew angle, i.e., an inclination with respect to the tangential direction of the motion of the recording medium, and was read using the MR head.
As shown in
FIG. 30
, the read waveform has a peak A and a noise waveform B at a side of the peak A. The noise waveform B demonstrates that the upper magnetic pole layer
13
and the protuberance
10
a
1
caused side writing.
Side writing causes degradation, such as the generation of noise, in recording characteristics. In other words, as shown in
FIG. 29
, the conventional thin-film magnetic head comprising the Gd defining layer
12
and the lower magnetic pole section
10
a
formed by milling the surface of the lower core layer
10
cannot achieve both small gap depth and inhibition of side writing.
SUMMARY OF THE INVENTION
The present invention aims to solve the above-described problems of the conventional art. An object of the present invention is to provide a thin-film magnetic head having a narrower track width required for higher recording densities while suitably preventing side writing. Another object of the present invention is to provide a manufacturing method for such a thin-film magnetic head.
The present invention provides a thin-film magnetic head comprising: a lower core layer comprising a lower magnetic pole s
Sato Kiyoshi
Watanabe Toshinori
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Renner Craig A.
LandOfFree
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