Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1998-12-08
2001-10-09
Miller, Brian E. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S119050
Reexamination Certificate
active
06301075
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inductive type thin film magnetic head used for a floating type magnetic head or the like, and more particularly, to a thin film magnetic head which can reduce eddy current loss without forming a secondary magnetic gap by improving the structure of a core layer, and a method of fabricating such a thin film magnetic head.
2. Description of the Related Art
FIG. 7
is a longitudinal sectional view of a conventional thin film magnetic head.
The thin film magnetic head shown in
FIG. 7
is a so-called “combined magnetic head”, in which a reading head, using a magnetoresistance effect, and an inductive magnetic head, for writing the signal into a recording medium such as a hard disk, are deposited. The combined magnetic head is provided on the end of a slider of a floating type magnetic head on the trailing side facing a recording medium such as a hard disk.
As shown in
FIG. 7
, an underlying layer
41
, a lower shield layer
42
, a lower insulating layer
43
, a magnetoresistive element layer
44
, and an upper insulating layer
45
are sequentially deposited on a substrate
40
composed of Al
2
O
3
—TiC, and an inductive magnetic head for writing is formed thereon.
A lower core layer
20
is composed of a magnetic material having high magnetic permeability such as an Fe—Ni alloy (permalloy). In a combined magnetic head in which the inductive magnetic head shown in
FIG. 7
is sequentially deposited on a reading head using a magnetoresistance effect, the lower core layer
20
functions also as an upper shield layer for the reading head.
A gap layer
2
composed of a nonmagnetic material such as Al
2
O
3
(aluminum oxide) is formed on the lower core layer
20
. An insulating layer
3
composed of a resist or other organic resin is formed on the gap layer
2
.
A coil layer
4
, composed of a conductive material having low electrical resistance such as Cu, is spirally formed on the insulating layer
3
. Although the coil layer
4
is formed so as to go around a base
21
b
of an upper core layer
21
, only a portion of the coil layer
4
is shown in FIG.
7
.
An insulating layer
5
composed of a resist or other organic resin is formed on the coil layer
4
. The upper core layer
21
is formed by plating a magnetic material such as a permalloy on the insulating layer
5
. A tip
21
a
of the upper core layer
21
is joined to the lower core layer
20
with the gap layer
2
therebetween at the section facing a recording medium to form a magnetic gap having a gap length G
11
. Also, a gap depth Gd is determined by the depth of the tip
21
a.
Also, the base
21
b
of the upper core layer
21
is connected to the lower core layer
20
through a hole formed in the gap layer
2
and the insulating layer
3
.
In the inductive magnetic head for writing, when a recording current is applied to the coil layer
4
, a recording magnetic field is induced to the lower core layer
20
and upper core layer
21
, and a magnetic signal is recorded onto a recording medium such as a hard disk by means of a leakage magnetic field from the magnetic gap between the lower core layer
20
and the tip
21
a
of the upper core layer
21
.
Although the recording frequency must be increased in order to meet the high-density recording, if the resistivity in the lower core layer
20
and the upper core layer
21
is low, eddy-current heat loss increases at high frequencies.
Therefore, the resistivity in the lower core layer
20
and the upper core layer
21
must be increased, and one of the known methods for increasing the resistivity is to change the structure of the lower and upper core layers
20
and
21
from a single layer to a laminate.
In accordance with Japanese Patent Laid-Open Nos. 63-244407 and 1-1027:12, as shown in
FIG. 8
, an upper core layer
21
(and/or a lower core layer
20
) is formed of a laminate in which a nonmagnetic material layer
24
is interposed between magnetic material layers
22
and
23
.
In such a laminate, eddy current loss can be reduced.
However, as shown in
FIG. 8
, the nonmagnetic material layer
24
is revealed to the surface (air bearing surface) facing a recording medium D, and magnetic gaps (secondary magnetic gaps) having a gap length G
12
are formed by nonmagnetic material layers
24
.
Accordingly, in the thin film magnetic head shown in
FIG. 8
, in addition to a magnetic gap having a gap length G
11
by a gap layer
2
, the magnetic gaps by the nonmagnetic material layer
24
(hereinafter referred to as “secondary magnetic gaps”) are formed, resulting in unstable recording characteristics.
In particular, if a secondary magnetic gap is formed on the upper core layer
21
, the secondary magnetic gap is located on the trailing side in relation to the original magnetic gap toward the recording medium D, and since the secondary magnetic gap is scanned after the original magnetic gap is scanned toward the recording medium D, the leakage magnetic field from the secondary magnetic gap largely affects the recording medium D.
Japanese Patent Laid-Open No. 63-247906 discloses a thin film magnetic head in which the structure of the tip of a core layer has been improved so as not to form a secondary magnetic gap in the core layer.
In the thin film magnetic head disclosed in the patent described above, as shown in
FIG. 9
, a nonmagnetic material layer
24
is formed in regions other than a region near a tip
21
a
of an upper core layer
21
, and the nonmagnetic material layer
24
is not exposed at the surface facing a recording medium D.
By employing such a structure, no trouble is caused by secondary magnetic gaps, and because of the laminate in the regions other than the tip
21
a
, there is low eddy-current heat loss, enabling an improvement in recording characteristics at high frequencies.
However, since the nonmagnetic material layer
24
is not formed near the tip
21
a
of the upper core layer
21
, the region near the tip
21
a
is single-layered, which increases eddy current loss near the tip
21
a
. Also, the fabrication process becomes significantly complex.
SUMMARY OF THE INVENTION
The present invention has been achieved in order to overcome the difficulties noted above with respect to the conventional art. It is an object of the present invention to provide a thin film magnetic head that does not cause a secondary magnetic gap and that can reduce eddy current loss by forming a core layer into a laminate having a nonmagnetic material layer interposed between magnetic material layers, and, in particular, by improving the structure of the tip of the core layer.
In accordance with the present invention, a thin film magnetic head includes first and second core layers composed of a magnetic material, and a coil layer provided between the core layers for inducing a recording magnetic field to both core layers. At least one of the core layers is a laminate in which a nonmagnetic material layer is interposed between magnetic material layers, the nonmagnetic material layer is exposed between the first and second core layers at the surface facing a recording medium, and a magnetic gap is formed by the nonmagnetic material layer.
Preferably, a core layer on the trailing side is a laminate.
The nonmagnetic material layer may be formed by oxidizing a nonmagnetic metal layer.
Also, in accordance with the present invention, in a method of fabricating a thin film magnetic head, the head including first and second core layers composed of a magnetic material, a gap layer composed of a nonmagnetic material provided between the core layers, a coil layer for inducing a recording magnetic field to both core layers, and an insulating layer for covering the coil layer, the method includes the steps of:
after forming the gap layer on the lower core layer and forming the coil layer and the insulating layer on the gap layer, forming a magnetic underlying layer to extend from the gap layer to the insulating layer;
forming a first magnetic material layer on the underlying layer excluding a tip region
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Miller Brian E.
Watko Julie Anne
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