Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2002-02-05
2004-10-05
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06801393
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head for recording which is suitable for, for example, a flying magnetic head and a contact magnetic head. More particularly, the present invention relates to a thin-film magnetic head which can produce a large magnetic field adjacent to the gap by properly preventing magnetic saturation in an upper magnetic layer, can enhance various characteristics, such as overwriting characteristics, and can enhance the controllability of the track width, and relates to a production method for the thin-film magnetic head.
2. Description of the Related Art
FIG. 30
is a partial front view showing the structure of a thin-film magnetic head (inductive head) as a related art, and
FIG. 31
is a partial longitudinal sectional view of the thin-film magnetic head, taken along line XXXI—XXXI in FIG.
30
and viewed from the direction of the arrows.
Referring to
FIGS. 30 and 31
, a lower core layer
1
is made of a magnetic material, such as permalloy, and an insulating layer
9
is formed thereon.
The insulating layer
9
has a groove
9
a
which extends from a surface opposing a recording medium (recording-medium opposing surface) in the height direction (Y-direction in the figure) and has an inner width in the track width direction (X-direction) equal to the track width Tw.
A lower magnetic layer
3
which is magnetically connected to the lower core layer
1
, a gap layer
4
, and an upper magnetic layer
5
which is magnetically connected to an upper core layer
6
are formed by plating, and are stacked from the bottom in that order inside the groove
9
a.
As shown in
FIG. 30
, the upper core layer
6
is formed on the upper magnetic layer
5
by plating.
As shown in
FIG. 31
, a coil layer
7
is formed in a spiral pattern on a portion of the insulating layer
9
offset from the groove
9
a
in the height direction (Y-direction).
The coil layer
7
is covered with a coil insulating layer
8
made of a resist or the like, and the upper core layer
6
is placed on the coil insulating layer
8
. The upper core layer
6
is magnetically connected to the upper magnetic layer
5
at a leading end portion
6
a,
and to the lower core layer
1
at a base end portion
6
b.
In the inductive head shown in
FIGS. 30 and 31
, when a recording current is applied to the coil layer
7
, a recording magnetic field is induced in the lower core layer and the upper core layer
6
, and a magnetic signal is recorded on a recording medium, such as a hard disk, by a leakage field produced between the lower magnetic layer
3
magnetically connected to the lower core layer
1
and the upper magnetic layer
5
magnetically connected to the upper core layer
6
.
The above-described thin-film magnetic head has the following disadvantages.
That is, the lengths between the recording-medium opposing surfaces and the rear end faces in the height direction of the lower magnetic layer
3
, the gap layer
4
, and the upper magnetic layer
5
are all set to T
1
. The length T
1
is called the gap depth (Gd). In the thin-film magnetic head of the related art, it is necessary to minimize T
1
in order to increase the leakage magnetic flux from the gap layer
4
.
As the gap depth decreases, the area of the joint surface between the upper core layer
6
and the upper magnetic layer
5
also decreases. Therefore, the magnetic flux flowing through the upper core layer
6
is condensed, and magnetic saturation occurs before the magnetic flux reaches the gap layer
4
. That is, a leakage magnetic flux is also produced in the portions spaced from the gap layer
4
. In particular, when the recording frequency is increased, precise recording is impossible.
Accordingly, the thin-film magnetic head has been improved, as shown in, for example, FIG.
32
.
FIG. 32
is a longitudinal sectional view of an improved thin-film magnetic head.
In the thin-film magnetic head shown in
FIG. 32
, a gap-depth defining layer
10
made of, for example, an organic insulating material is formed on a portion of a lower core layer
1
at a predetermined distance from a recording-medium opposing surface in the height direction.
A lower magnetic layer
3
, a gap layer
4
, and an upper magnetic layer
5
are stacked from the bottom in that order between the recording-medium opposing surface and the gap-depth defining layer
10
. In
FIG. 32
, the gap depth (Gd) is defined by the length T
2
from the recording-medium opposing surface to the position where the gap layer
4
and the gap-depth defining layer
10
contact each other, and can be easily optimized by changing the position of the gap-depth defining layer
10
. Moreover, since the upper magnetic layer
5
can be made longer than the gap depth by being extended onto the gap-depth defining layer
10
, the contact area between the upper magnetic layer
5
and an upper core layer
6
can be increased, regardless of the gap depth. This makes it possible to properly reduce the magnetic saturation in the upper magnetic layer
5
even when the recording density increases in future.
In order to further increase the recording density, it is necessary to increase the leakage field adjacent to the gap. For that purpose, it is preferable that the upper magnetic layer
5
have a multilayered structure composed of two or more magnetic layers, that a lower layer of the magnetic layers in contact with the gap layer
4
be formed of a high-Bs layer having a high saturation magnetic flux density Bs, and that an upper layer having a lower saturation magnetic flux density Bs than that of the high-Bs layer be formed on the high-Bs layer.
FIG. 33
is a process view of the thin-film magnetic head shown in FIG.
32
. The gap-depth defining layer
10
is formed on the lower core layer
1
, and the lower magnetic layer
3
and the gap layer
4
are formed on a portion of the lower core layer
1
disposed in front of the gap-depth defining layer
10
by plating. The upper magnetic layer
5
is then formed on the gap layer
4
by plating. In this case, however, a lower layer
11
of the upper magnetic layer
5
having a high saturation magnetic flux density cannot be suitably formed so as to extend onto the gap-depth defining layer
10
.
This is because the gap-depth defining layer
10
is an insulating layer made of an organic insulating material or the like. Even when the lower layer
11
is formed on the gap-depth defining layer
10
, the thickness thereof is much less than when formed on the gap layer
4
.
An upper layer
12
formed on the lower layer
11
by plating is, of course, not easily formed on the gap-depth defining layer
10
, and the thickness thereof on the gap-depth defining layer
10
is small. For this reason, the upper magnetic layer
5
formed on the gap-depth defining layer
10
is extremely thin.
In the subsequent step, the upper magnetic layer
5
is ground to line C—C in order to flatten the upper surface thereof. When the thickness of the upper magnetic layer
5
at the rear end is small, as described above, the volume is substantially reduced by the grinding step, and the upper magnetic layer
5
is prone to cause magnetic saturation.
For example, when the upper magnetic layer
5
is ground to line C′—C′, a recess
5
c
is sometimes formed or the upper magnetic layer
5
itself is not formed at the rear end, depending on the accuracy of the flattening.
Since the lower layer
11
having a high saturation magnetic flux density formed on the gap-depth defining layer
10
is extremely thin, as described above, a magnetic flux flowing from the upper core layer
6
to the upper magnetic layer
5
is not properly guided to the lower layer
11
, that is, the flow efficiency of the magnetic flux to the lower layer
11
declines. For this reason, the upper magnetic layer
5
is prone to cause magnetic saturation, and the leakage field adjacent to the gap layer
4
cannot be increased. As a result, it is impossible to produce a thin-film magnetic head which can suitably respond to future increase
Morita Sumihito
Oki Naruaki
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Tupper Robert S.
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