Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-02-01
2001-08-14
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S900000, C360S112000, C360S125330
Reexamination Certificate
active
06274256
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head in which a coil layer is provided between core layers, and more particularly to a thin film magnetic head in which an excellent non-linear transition shift (hereinafter referred to as NLTS) characteristic and an excellent overwrite (hereinafter referred to as OW) characteristic can be simultaneously obtained.
2. Description of the Related Art
FIG. 8
is an enlarged detail of a conventional thin film magnetic head showing a construction of a facing surface facing a recording medium.
FIG. 9
is a longitudinal sectional view of the thin film magnetic head shown in FIG.
8
.
FIG. 10
is a fragmentary isometric view of an entire construction of the conventional thin film magnetic head.
The thin film magnetic head shown in
FIGS. 8
to
10
is a combined-type thin film magnetic head in which a read-out head h
1
using a magnetoresistive effect and an inductive magnetic head h
2
for writing a signal on a recording medium such as a hard disk are laminated. As shown in
FIG. 10
, the thin film magnetic head is provided at a trailing side end surface
12
a
of a slider
12
of a floating type magnetic head.
Reference numeral
20
in
FIGS. 8
to
10
indicates a lower core layer which is made of a magnetic material having a high magnetic permeability such as an Fe—Ni based alloy (Permalloy). The lower core layer
20
functions also as an upper shielding layer of the read-out head h
1
using a magnetoresistive effect. A gap layer
21
which is made of a nonmagnetic material such as A
1
2
O
3
(aluminum oxide) is formed on the lower core layer. As shown in
FIG. 9
, an insulating layer
22
which is made of organic resin materials including resist materials are provided on the gap layer
21
.
Coil layers
23
which are made of an electric conductive material having a low electric resistance such as Cu are helically provided on the insulating layer
22
. As shown in
FIG. 9
, an insulating layer
24
which is made of organic resin materials including resist materials is formed on the coil layers
23
. Further, a magnetic material such as Permalloy is plated on the insulating layer
24
to form an upper core layer
25
. As shown in
FIG. 8
, a protective layer
26
is provided on the upper core layer
25
.
As shown in
FIG. 10
, the upper core layer
25
includes a tip portion A having a constant width and a rear end portion B which gradually becomes wider starting from the tip portion A toward the rear end side. As shown in
FIG. 9
, the tip of the tip portion A is connected with the lower core layer
20
by interposing the gap layer
21
at a facing portion facing onto a recording medium so as to form a magnetic gap having a gap length of G
11
. In addition, as shown in
FIGS. 9 and 10
, a base end portion
25
a
of the upper core layer
25
is magnetically brought into contact with the lower core layer
20
through a groove formed at the gap layer
21
and the insulating layer
22
.
With respect to the inductive magnetic head for writing h
2
, when a recording current is applied to the coil layer
23
, a recording magnetic field is induced in the lower core layer
20
and the upper core layer
25
. Thus, a magnetic signal is recorded on a recording medium such as a hard disk using a leakage magnetic field from a magnetic gap portion between the tip of the lower core layer
20
and the tip of the upper core layer
25
.
In addition, as shown in
FIGS. 8
to
10
, the read-out head h
1
which is provided under the inductive magnetic head h
2
comprises a lower shielding layer
30
which is made of a magnetic material, a magnetoresistive device layer
32
which is provided on the lower shielding layer
30
by interposing a lower gap layer
31
, and an upper shielding layer
20
(a lower core layer) which is formed on the magnetoresistive device layer
32
by interposing an upper gap layer
33
.
When the recording density becomes higher, a leakage magnetic field which arises at a magnetic gap between the core layers
20
and
25
in the inductive magnetic head h
2
shown in
FIGS. 8
to
10
is affected by a leakage magnetic field which arises in a direction starting from a recording signal immediately recorded on a recording medium to the head side. Thus, nonlinear distortion arises so as to easily induce a phase shift (that is, NLTS). This NLTS characteristic greatly depends on the configuration of the portion A of the upper core layer
25
. In addition, an important recording characteristic in addition to the NLTS characteristic is the OW characteristic.
The term “overwrite” means “double write”. The OW characteristic is evaluated as follows. A signal is recorded at a low frequency and then another signal is overwritten at a high frequency. The OW characteristic is evaluated by the degree of decrease in a residual output power of the recording signal at a low frequency in the overwritten state compared with that before overwriting at a high frequency.
The OW characteristic also depends on the configuration of the tip portion A of the upper core layer
25
similarly to the NLTS characteristic. Conventionally, the tip portion A has been appropriately configured to be excellent in only one of the NLTS and OW characteristics, and excellent NLTS and OW characteristics cannot be simultaneously obtained.
SUMMARY OF THE INVENTION
The present invention intends to overcome the above-described problem. In particular, it is an object of the present invention to provide a thin film magnetic head capable of simultaneously obtaining excellent NLTS and OW characteristics by forming a tip portion of an upper core layer in a proper size.
According to one aspect of the present invention, there is provided a thin film magnetic head including: a lower magnetic core layer and an upper magnetic core layer separated by a coil layer therebetween for inducing a recording magnetic field to the lower and upper core layers; wherein the upper core layer includes a tip portion having a constant width starting from a facing portion facing onto a recording medium to the rearward direction which is distant from the recording medium, and a rear end portion which rearwardly becomes larger in width from the tip portion; and when a product (S×Bs) of a cross-sectional area of the tip portion (S) and a saturation magnetic flux density of a magnetic material consisting the upper core layer (Bs) is in a range of 1.5 to 10.5 &mgr;m
2
·T.
Furthermore, in accordance with the present invention, the product (S×Bs) is preferably in a range of 4.0 to 8.0 &mgr;m
2
·T.
Still furthermore, in accordance with the present invention, a length of the tip portion in the distant direction from the recording medium is preferably in a range of 3.5 to 7.6 &mgr;m.
In the conventional art, excellent NLTS and OW characteristics cannot be simultaneously obtained. However, in accordance with the present invention, the configuration of a tip portion of an upper core layer is improved so as to simultaneously obtain excellent NLTS and OW characteristics.
REFERENCES:
patent: 5224002 (1993-06-01), Nakashima et al.
patent: 5751522 (1998-05-01), Yamada et al.
patent: 06119618 (1994-04-01), None
patent: 06124415 (1994-05-01), None
Sato Atsushi
Takahashi Akira
Watanabe Toshinori
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kiliman Leszek
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