Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-03-30
2002-12-10
Ometz, David L. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S327000
Reexamination Certificate
active
06493194
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of thin film magnetic heads that employ a magnetoresistive layer and which are used as reproduction heads for magnetic disk devices.
BACKGROUND OF THE INVENTION
In response to the increasing recording density of hard disk drives, reproduction heads are being developed with a narrower reproduction track width and greater reproduction output than those of conventional thin film magnetic heads. One of these new reproduction heads is a MR head which utilizes the magnetoresistive effect, in which electric resistance changes in response to changes in an externally applied magnetic field. Types using materials with greater magnetoresistive effect are called GMR heads.
FIG. 4
is a sectional view of a part of a conventional thin film magnetic head. In
FIG. 4
, an insulating base layer
21
made such as of alumina, a lower shield magnetic layer
22
made of soft magnetic material such as nickel and iron, a first insulating layer
23
made of a non-magnetic material such as alumina, and a magnetoresistive layer
24
are formed on a substrate (not illustrated) made such as of alumina/titanium carbide. In the magnetoresistive layer
24
, a magnetic response region
24
a
is for generating normal signals and an unwanted signal generating region
24
b
generates unwanted signals when the current flows through this region. A magnetic bias layer
25
, made such as of hard magnetic film and antiferromagnetic film, for applying a magnetic bias to the magnetoresistive layer
24
; lead
26
; and a second insulating layer
27
for covering the lead
26
, etc. are also formed.
The end face of the tip of the lead
26
is tapered, and a first taper close to the magnetoresistive layer
24
is formed at a large angle &thgr;, and a second taper far from the magnetoresistive layer
24
is formed at a smaller angle &phgr;. For simplification, the upper shielding magnetic layer formed on the second insulating layer
27
is not illustrated.
In the prior art shown in
FIG. 4
, the magnetic bias layer
25
is disposed in a clearance created on the first insulating layer
23
, and the magnetoresistive layer
24
is formed on the magnetic bias layer
25
and the clearance. The tip of the lead
26
contacts the magnetoresistive layer
24
beyond the end of the magnetic bias layer
25
.
In general, the magnetic response region
24
a
is approximately equivalent to the area between the tips of the leads
26
. Strictly speaking, however, it is not electrically equivalent to the area between the tips of the leads
26
because the current from the lead
26
flows not only from the tip of the lead
26
but also extensively in the lengthwise direction of the lead
26
.
In order to satisfy the increasing demand for higher recording density, the magnetic head needs to achieve a narrower reproduction track width by narrowing the magnetic response region but without degrading the sensitivity and S/N ratio. Accordingly, the current needs to be fed efficiently only to the magnetic response region, which is equivalent to the width of a track, without any current leakage to other regions.
In the aforementioned prior art, the width of the magnetic response region is accurately specified by forming the large angle &thgr; at the tip of the lead
26
against the main face of the magnetoresistive layer
24
. The coverage of the second insulating layer
27
at the step portion is improved by forming a portion following the tip of the lead with a smaller angle &phgr; for a gentle slope.
However, the magnetoresistive layer
24
is formed crossing the step portion at the tip of the magnetic bias layer
25
, and this causes a different concern. More specifically, the magnetic bias layer
25
needs to be disposed as close as possible to the magnetic response layer
24
a
in order to efficiently apply a magnetic bias to the magnetic response layer
24
a
in the above conventional configuration. On the other hand, the tip of the magnetic bias layer
25
and the tip of the lead
26
also come closer when the magnetic bias layer
25
and the magnetic response layer
24
a
are in closer proximity. This requires that the lead
26
be thickened at the portion close to the magnetic bias layer
25
, resulting in an overall increase in the thickness of the lead
26
. Greater thickness at the tip of the lead
26
, which is thickness of a slope portion having the angle &thgr;, causes problems in coverage of the second insulating layer
27
at the step portion covering the lead
26
, and occurrence of cracks.
Also in the conventional configuration, the lead
26
directly contacts the magnetoresistive layer
24
, and this requires that a material for the lead
26
be selected for good adhesivity to the magnetoresistive layer
24
without causing a reaction with the magnetoresistive layer
24
, resulting in many restrictions on its practical use.
The present invention aims to provide a thin film magnetic head which allows the accurate definition of the magnetic response region, to reduce current to the magnetoresistive layer at regions other than the magnetic response region, and to increase the S/N ratio by increasing the proportion of current flowing in the magnetic response region; and to offer a structure that is easy to manufacture.
SUMMARY OF THE INVENTION
The thin film magnetic head of the present invention includes an insulating base layer; a lower shield magnetic layer formed on the insulating base layer; a first insulating layer formed on the lower shield magnetic layer; a magnetoresistive layer formed selectively over at least a portion of the first insulating layer; a magnetic bias layer formed sandwiching the magnetoresistive layer for applying magnetic bias to the magnetoresistive layer; a pair of leads formed over at least a portion of the magnetic bias layer for detecting a change in electric resistance of the magnetoresistive layer by an external magnetic field; a non-magnetic cap layer formed under the lead between the lead and the magnetoresistive layer; a second insulating layer at least covering the magnetoresistive layer, magnetic bias layer, and pair of leads; and an upper shield magnetic layer formed on the second insulating layer.
In the above configuration, the non-magnetic cap layer under the leads accurate specification of the width of the magnetic response region, allowing the current to effectively flow from the lead to the magnetic response region.
Moreover, the thin film magnetic head of the present invention includes an insulating base layer; a lower shield magnetic layer formed on the insulating base layer; a first insulating layer formed on the lower shield magnetic layer; a magnetoresistive layer formed over at least a portion of the first insulating layer; a magnetic bias layer formed sandwiching the magnetoresistive layer for applying magnetic bias to the magnetoresistive layer; a non-magnetic cap layer formed on a main face of the magnetoresistive layer; a pair of leads formed over at least a portion of the magnetic layer for detecting a change in electric resistance of the magnetoresistive layer by an external magnetic field; a second insulating layer at least covering the magnetoresistive layer, magnetic bias layer; and pair of leads; and an upper shield magnetic layer formed on the second insulating layer. The portion of the non-magnetic cap layer under the lead is thicker than the portion of the non-magnetic cap layer not under the lead.
This configuration enables to effectively protect the main face of the magnetoresistive layer in the manufacturing process, and, at the same time, the thick non-magnetic cap layer under the leads enables to accurately specify the width of the magnetic response region, allowing the current to effectively flow is from the lead to the magnetic response region.
Still more, the thin film magnetic head of the present invention includes an insulating base layer; a lower shield magnetic layer formed on the insulating base layer; a first insulating layer formed on the lower shield magnetic layer; a magnetoresistive lay
Kimura Tadashi
Mitani Satoru
Sakaguchi Masaya
Sekiguchi Hiroyoshi
Tsuji Hiroyasu
Matsushita Electric - Industrial Co., Ltd.
Nguyen Dzung
Ometz David L.
RatnerPrestia
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