Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-09-24
2004-12-07
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06829122
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a magnetic head, and, more particularly, to a magnetic head used in reproducing magnetically recorded information from a magnetic recording medium such as a hard disk.
2. Description of the Related Art
A magnetic recording and reproducing device, such as a magnetic disk device, is widely employed as an external recording and reproducing device of a computer. Recently, as such a magnetic recording and reproducing device has drastically come to have a mass capacity, a magnetic recording medium has come to have a sharply increased recording density. Accordingly, there have been increasing needs for a magnetic head capable of providing a high performance. A magnetic head of a magnetoresistance type (an MR head) is drawing attention as a magnetic head satisfying these needs, since the MR head can provide a high-level output without depending on a speed of the magnetic recording medium. Such an MR head includes an MR head using a single-layer film, an MR head using a spin-valve film, and an MR head using a tunnel-effect film.
Especially, the MR head using the spin-valve film utilizing a huge magnetoresistance effect has recently been popular, while the MR head using the tunnel-effect film is being brought into practical use. These MR heads include a free magnetic layer as a structure thereof. As a magnetic recording and reproducing device has come to have a mass capacity, these MR heads have been further miniaturized. In order to provide these MR heads with a still higher capability under this circumstance, technologies have soon to be established, in which technologies a magnetic domain of the above-mentioned free magnetic layer is surely regulated.
Known as one of the above-mentioned technologies is a structure of an MR head of a spin-valve type, in which a magnetic-domain regulating film is connected to each side of a spin-valve film functioning as a magnetoresistance film.
FIG. 1
shows a basic structure of a conventional spin-valve-type MR head
100
. It is noted that a conductor lead-out layer and an upper insulating layer described hereinafter are not shown in FIG.
1
.
In this spin-valve-type MR head
100
, an insulating layer
101
is formed of such a material as alumina (Al
2
O
3
) so as to form a gap. A spin-valve film
103
(a magnetoresistance film) is formed on the insulating layer
101
. A magnetic-domain regulating film
106
is also formed on the insulating layer
101
so as to flank the
103
. This magnetic-domain regulating film
106
is referred to as a hard film
106
since the magnetic-domain regulating film
106
is formed of a hard-magnetic material consisting of such a material as a Co-group material. An underlying layer
105
formed generally of a Cr-group material is provided between the insulating layer
101
and the hard film
106
for the purpose of improving a crystallinity of the hard film
106
.
For example, the above-mentioned spin-valve-type MR head
100
can be manufactured by steps shown in
FIG. 2A
to FIG.
2
F. The manufacturing steps shown in
FIG. 2A
to
FIG. 2F
form the above-mentioned films one by one on the insulating layer
101
by using thin-film formation technologies including sputtering and etching so as to form a desired laminated structure. It is noted that
FIG. 2A
to
FIG. 2F
show only the left side of the spin-valve film
103
, because both sides of the spin-valve film
103
are symmetrical.
FIG. 2A
shows a step of forming the spin-valve film
103
on the insulating layer
101
composed of alumina (Al
2
O
3
). If the spin-valve film
103
has a regular-order laminated structure, the spin-valve film
103
has a free magnetic layer, a nonmagnetic layer, a pinned magnetic layer and an antiferromagnetic layer laminated in this order from the bottom; if the spin-valve film
103
has a reverse-order laminated structure, the spin-valve film
103
has an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic layer and a free magnetic layer laminated in this order from the bottom, though not shown in the figures. Besides, an underlying layer
102
is formed under the spin-valve film
103
, i.e., between the insulating layer
101
and the spin-valve film
103
. This underlying layer
102
is provided case by case so as to improve a crystallinity of the spin-valve film
103
.
FIG. 2B
shows a step of patterning the spin-valve film
103
and the underlying layer
102
. In this step, the spin-valve film
103
and the underlying layer
102
are patterned into a shape corresponding to a track width (in the crosswise direction in
FIG. 2A
to
FIG. 2F
) of a magnetic recording medium. It is noted that the underlying layer
102
is not shown in
FIG. 2C
to FIG.
2
F.
FIG. 2C
shows a step of forming the underlying layer
105
for the hard film
106
that is to be formed in the next step.
FIG. 2D
shows a step of forming the hard film
106
on the underlying layer
105
so that the hard film
106
contacts each end of the spin-valve film
103
.
FIG. 2E
shows a step of forming a conductive lead-out layer
107
on the hard film
106
. The conductive lead-out layer
107
is to be used to electrically take out a magnetoresistance change in the spin-valve film
103
.
Finally,
FIG. 2F
shows a step of forming an insulating layer
109
on the spin-valve film
103
and the conductive lead-out layer
107
. The heretofore-mentioned steps shown in
FIG. 2A
to
FIG. 2F
form the conventional spin-valve-type MR head
100
.
In the above-described spin-valve-type MR head
100
, the underlying layer
102
is on the insulating layer
101
, and the spin-valve film
103
is on the underlying layer
102
; that is, the upper surface of the insulating layer
101
and the bottom surface of the underlying layer
102
are in the same plane.
However, there are two problems regarding a regulation of a magnetic domain of the above-mentioned free magnetic layer of the spin-valve film
103
.
A description will be given, with reference to
FIG. 1
,
FIG. 3A
, FIG.
3
B and
FIG. 4
, of the first problem. FIG.
3
A and
FIG. 3B
show magnetic characteristics of the hard film
106
. Specifically,
FIG. 3A
shows a magnetic characteristic of the hard film
106
in a territory TER-A shown in
FIG. 1
, and
FIG. 3B
shows a magnetic characteristic of the hard film
106
in a territory TER-B shown in FIG.
1
.
The magnetic characteristic of the hard film
106
shown in
FIG. 3A
is good, marking a coercive force of
1230
Oe and a squareness ratio of 0.86, because the hard film
106
is formed on the underlying layer
105
composed of a Cr-group material provided on the insulating layer
101
.
However, a part of the spin-valve film
103
, the antiferromagnetic layer for example, remains under the joining part between the spin-valve film
103
and the hard film
106
in the territory TER-B. Therefore, there is a lamination, around the joint part in the territory TER-B, of the underlying layer
105
formed on the antiferromagnetic layer and the hard film
106
formed on this underlying layer
105
.
Additionally, in the territory TER-B, the underlying layer
105
for the hard film
106
tends to be formed thinner than in the territory TER-A. Therefore, the underlying layer
105
does not function sufficiently in improving a crystallinity of the hard film
106
. In other words, since the underlying layer
105
is formed on the spin-valve film
103
that has a predetermined crystallinity, the spin-valve film
103
puts a bad influence on the crystallinity-improvement function of the underlying layer
105
.
The inventors of the present invention have confirmed that forming the underlying layer
105
on the antiferromagnetic layer of the spin-valve film
103
deteriorates the crystallinity-improvement function of the underlying layer
105
. Thus, when the hard film
106
is formed on the underlying layer
105
having such a deteriorated crystallinity-improvement function, the hard film
106
naturally comes to have a deteriorated crystallinity. Accordingly, the hard film
1
Kanai Hitoshi
Mukoyama Naoki
Suzuki Hidehiko
Yamada Ken'ichiro
Evans Jefferson
Fujitsu Limited
Greer Burns & Crain Ltd.
LandOfFree
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