Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-11-07
2001-04-03
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603130, C029S603150, C427S130000, C427S131000
Reexamination Certificate
active
06209192
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a thin film magnetic head to be used in a magnetic recording device, and more particularly to a thin film magnetic head with an improved reliability achieved by reducing to a lower level the magnitude of “undershoot” that appears on both sides of a main peak of the waveform of the reproduced data signal.
(2) Description of the Related Art
A magnetic recording device comprises as essential components thereof a magnetic recording medium for storing data that is mainly made of a hard magnetic thin film and a magnetic head for recording data into and reproducing them from the magnetic recording medium. Because of the recent technological development for high density data storage, the thin film magnetic head has been remarkably improved in terms of not only data recording density but also the data recording frequency. Currently, thin film magnetic heads having a low inductance and a high signal reproducing efficiency are generally used to realize a high data recording density. A thin film magnetic head comprises a pair of magnetic poles with a gap disposed therebetween, which magnetic poles are made of respective thin films having a thickness of several micrometers.
A first known thin film magnetic head is shown in
FIGS. 1A and 1B
of the accompanying drawings, of which
FIG. 1A
illustrates a schematic sectional view of the head, and
FIG. 1B
illustrates an output waveform of a reproduced signal.
As shown, in this known thin film magnetic head comprises first and second magnetic pole layers
100
and
102
that are connected to each other at the respective base sections
100
d
and
102
d
and are made of thin film soft magnetic materials, a thin film coil
103
wound at least around either the first magnetic pole layer
100
or the second magnetic pole layer
102
and a magnetic gap layer
104
disposed between the front end sections
100
a
and
102
a
of the first and second magnetic pole layers
100
and
102
.
As shown, an isolated transition of magnetization
112
is formed to separate opposite magnetizing directions
108
and
110
of a recording medium
106
disposed under the magnetic head. When the recording medium moves along arrow
113
, the data signal reproduced by the thin film magnetic head shows a waveform having an isolated main peak
114
representing the reproduced data signal and two undershoots
116
located respectively on lateral sides of the main peak
114
and produced respectively corresponding to a lateral section
100
b
of the first magnetic pole layer
100
and a lateral section
102
b
of the second magnetic pole layer
102
.
The undershoot output
116
located on the respective lateral sides of the isolated main peak
114
have a polarity opposite to that of the isolated main peak
114
and interferes with the isolated main peak
114
to change the value of the isolated main peak
114
as the recording linear density of the recording medium increases and the distance separated by the isolated transition of magnetization
112
is reduced. Additionally, the isolated main peak
114
can eventually be caused to be shifted.
The undershoot outputs
116
appear when the isolated transition of magnetization
112
of the recording medium
106
passes by the lateral section
100
b
and goes under the first magnetic pole layer
100
and when it passes by the lateral section
102
b
and leaves the second magnetic pole layer
102
, and this is because the rate at which the magnetic flux generated by the isolated transition of magnetization
112
flows into the first magnetic pole layer
100
and the second magnetic pole layer
102
changes abruptly at those respective points.
A second known thin film magnetic head is proposed in IEEE Transactions on Magnetics, Vol. 29, No. 6., pp. 3837-3839 (Nov. 1993) to reduce the undershoots
116
having the polarity opposite to that of the isolated main peak
114
.
FIGS. 2A and 2B
of the accompanying drawings illustrate the proposed magnetic head.
FIG. 2A
shows an enlarged schematic partial sectional view of the head and
FIG. 2B
shows the output waveform of a reproduced signal. Here, the components that are same or similar to their counterparts of the magnetic head of
FIGS. 1A and 1B
are denoted respectively by the same reference symbols.
The second known thin film magnetic head is provided on the front end sections
100
a
and
102
a
of the first and second magnetic pole layers
100
and
102
with recesses
100
c
and
102
c
. These recesses
100
c
and
102
c
are formed by partly removing the respective front end sections
100
a
and
102
a
by means of an appropriate technique such as ion etching or ion milling. As a result, the undershoots
118
have an amplitude slightly smaller than that of the undershoots of the first known magnetic head.
However, the above described second known thin film magnetic head is accompanied by the following problems.
(1) While the undershoot outputs
118
have a low profile, they are still there. As described above, the undershoots result in shifting of the isolated main peak and hence raising the detection error rate in the peak detecting operation conducted when the magnetic recording device is operating for data reproduction.
(2) As the front end sections
100
a
and
102
a
are partly removed, they are made partly very thin on the respective sides of the magnetic gap
104
. Then, a magnetically saturated state appears in the front end sections
100
a
and
102
a
when an electric current flows therethrough for data recording operation so that the transition of magnetization
112
is broadened resulting in the reduction of the output level for high density data recording.
(3) Because of the recessed profile of the front end sections
100
c
and
102
c
, dust and other contaminants can easily be caught there to consequently reduce the reliability of the magnetic recording device comprising such a thin film magnetic head.
(4) In order to form recesses in the front end sections
100
a
and
102
a
, their forming process must be carried out from the side that is to be magnetically floated. More specifically, after slicing a wafer into rows to be worked with a slider for preparing thin film magnetic heads, each of the rows is exposed to light and subjected to an intricate processing operation typically involving ion milling to produce recesses
100
c
and
102
c
. Thus, wafers cannot be treated on a mass production basis and the productivity of preparing such recesses is inevitably low.
SUMMARY OF THE INVENTION
An object of the present invention, therefore, is to overcome the problems existing in the prior art, and to provide a thin film magnetic head and a fabrication process therefor, which enables the reduction of the magnitude of undershoots appearing on the lateral sides of the main peak of the waveform of the reproduced data signal to a low level and the avoidance of a magnetically saturated state that can appear in the front end sections of the magnetic head. Such a magnetic head may have a profile less prone to the adhesion of dust and other contaminants and can be manufactured on a mass production basis.
According to one aspect of the invention, there is provided a thin film magnetic head comprising:
first and second magnetic pole layers which are made of a thin film of a soft magnetic material and connected to each other at respective base sections thereof;
a thin film coil which is wound around at least one of the first magnetic pole layer and the second magnetic pole layer;
a magnetic gap layer which is disposed between a front end section of the first magnetic pole layer and a front end section of the second magnetic pole layer; and
at least one magnetically insulating layer which is disposed along a plane facing a recording medium, the magnetically insulating layer partitioning at least one of the front end section of the first magnetic pole layer and the frond end section of the second magnetic pole layer.
According to another aspect of the invention, there is provided a method of fa
Saitho Sinsaku
Urai Haruo
Hayes, Soloway, Hennessey Grossman & Hage, P.C.
NEC Corporation
Tugbang A. Dexter
Young Lee
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