Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-03-30
2004-06-15
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06751053
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic write head used, for example, as a floating-type magnetic head. More particularly, the invention relates to a thin-film magnetic head in which fringing flux can be produced at an appropriate section in the periphery of a gap layer and which is suitable for an increased recording density and an increased recording frequency.
2. Description of the Related Art
FIG. 23
is a partial front view showing the structure of a conventional thin-film magnetic head (inductive head), and
FIG. 24
is a sectional view taken along the line XXIV—XXIV of FIG.
23
.
As shown in
FIGS. 23 and 24
, an insulating layer
9
is formed on a lower core layer
1
composed of a magnetic material, such as Permalloy.
The insulating layer
9
is provided with a trench
9
a
which extends in the height direction (in the Y direction in the drawing) from a surface facing a recording medium (hereinafter referred to as an “ABS”) with the inner width being set to be a track width Tw.
In the trench
9
a
, a lower pole layer
3
, a gap layer
4
, and an upper pole layer
5
which is magnetically coupled to an upper core layer
6
are formed by plating in that order from the bottom.
As shown in
FIG. 23
, the upper core layer
6
is formed by plating over the upper pole layer
5
.
As shown in
FIG. 24
, a coil layer Co is spirally formed by patterning on the insulating layer
9
at the back of the trench
9
a
formed in the insulating layer
9
.
The coil layer Co is covered by a coil insulating layer
8
composed of a resist or the like, and the upper core layer
6
is formed on the coil insulating layer
8
. A tip
6
a
of the upper core layer
6
is magnetically coupled to the upper pole layer
5
and a base
6
b
of the upper core layer
6
is magnetically coupled to the lower core layer
1
.
In the inductive head shown in
FIGS. 23 and 24
, when a recording current is applied to the coil layer Co, a recording magnetic field is induced in the lower core layer
1
and the upper core layer
6
, and magnetic signals are written into a recording medium, such as a hard disk, by a fringing magnetic field between the lower pole layer
3
which is magnetically coupled to the lower core layer
1
, and the upper pole layer
5
which is magnetically coupled to the upper core layer
6
.
In the inductive head shown in
FIGS. 23 and 24
, the lower pole layer
3
, the gap layer
4
, and the upper pole layer
5
are locally formed with the track width in the vicinity of the ABS, and an inductive head of this type is suitable for track narrowing.
A method for fabricating the inductive head shown in
FIGS. 23 and 24
will be described. First, the insulating layer
9
is formed on the lower core layer
1
, and the trench
9
a
having the track width Tw is formed in the insulating layer
9
for a predetermined length from the ABS in the height direction.
Next, in the trench
9
a
, the lower pole layer
3
, the gap layer
4
, and the upper pole layer
5
are continuously formed by plating, and then the coil layer Co is formed by patterning on the insulating layer
9
at the back of the trench
9
a
formed in the insulating layer
9
.
The coil layer Co is covered by the coil insulating layer
8
, and the upper core layer
6
is formed over the upper pole layer
5
and the coil insulating layer
8
by frame plating, and thus the inductive head shown in
FIGS. 23 and 24
is obtained.
In the thin-film magnetic head shown in
FIGS. 23 and 24
, as described above, when a recording current is applied to the coil layer Co, a recording magnetic field is induced in the lower core layer
1
and the upper core layer
6
, and magnetic flux flows into the lower pole layer
3
and the upper pole layer
5
. Consequently, the upper pole layer
5
is magnetically saturated in the vicinity of the gap layer
4
, resulting in a fringing flux, and magnetic recording is performed on the recording medium by the fringing flux.
However, in the inductive head shown in
FIG. 24
, at the joint between the upper pole layer
5
and the upper core layer
6
, the inner end of the lower surface of the upper core layer
6
and the inner end of the upper surface of the upper pole layer
5
are located at the same position.
If the inner end of the upper core layer
6
and the inner end of the upper pole layer
5
are located at the same position at the joint between the upper pole layer
5
and the upper core layer
6
, flux from the upper core layer
6
cannot be concentrated at the joint and it may not be possible for the flux to magnetically saturate the upper pole layer
5
, resulting in a deterioration of the recording characteristics of the inductive head.
The depth T
1
in the height direction of the joint between the gap layer
4
and the upper pole layer
5
is generally referred to as a gap depth (Gd), and in order to increase the fringing flux at the gap layer
4
, the gap depth T
1
must be decreased.
However, in the inductive head shown in
FIG. 24
, the gap depth T
1
is equal to the length from the front surface at the ABS to the back surface in the height direction of the upper pole layer
5
.
With respect to the structure of the thin-film magnetic head shown in
FIGS. 23 and 24
, since the width in the track width direction (in the X direction in the drawing) of the upper core layer
6
is larger than the width in the track width direction of the upper pole layer
5
, which is equal to the track width Tw, the fringing magnetic field occurring between the upper core layer
6
and the upper pole layer
5
is wider than the track width Tw, and thus side fringing easily occurs.
In order to fabricate a thin-film magnetic head which is suitable for an increased recording density, in addition to the narrowing of the track width Tw, side fringing must be suppressed.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a thin-film magnetic head in which accurate magnetic recording can be performed by reliably producing fringing flux at a gap layer even if the track width is decreased.
It is another object of the present invention to provide a thin-film magnetic head in which, in particular, side fringing can be appropriately suppressed and also to provide a method for fabricating the same.
In one aspect of the present invention, a thin-film magnetic head includes a lower core layer; a gap layer formed on the lower core layer directly or with a lower pole layer therebetween, the lower pole layer having a smaller width in the track width direction than that of the lower core layer; an upper pole layer formed on the gap layer, the upper pole layer having a smaller width in the track width direction than that of the lower core layer; and an upper core layer joined to the upper pole layer. In the joint between the upper pole layer and the upper core layer, the width in the track width direction of the lower surface of the upper core layer is larger than the width in the track width direction of the upper surface of the upper pole layer, and also the inner end of the lower surface of the upper core layer is located at the back, in the height direction, of the inner end of the upper surface of the upper pole layer.
In this aspect of the present invention, at the joint between the upper pole layer and the upper core layer, flux from the upper core layer can be concentrated, and thus the upper pole layer can be reliably magnetically saturated by the flux. Therefore, recording characteristics of the thin-film magnetic head can be stabilized.
Since the flux flows satisfactorily from the upper core layer to the upper pole layer, high frequency recording characteristics of the thin-film magnetic head are also improved.
Preferably, the inner end of the lower surface of the upper core layer is 0.2 &mgr;m to 1.5 &mgr;m distant from the inner end of the upper surface of the upper pole layer in the height direction.
Preferably, the back surface of the upper pole layer is located towards the back, in the height direction, from the depth
Ikegami Chiaki
Ikegami Masaki
Kobayashi Kiyoshi
Sato Kiyoshi
Watanabe Toshinori
Alps Electric Co. ,Ltd.
Cao Allen
Ikegami Chiaki
LandOfFree
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