Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-12-10
2004-07-06
Tugbang, A. Dexter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603070, C029S603080, C029S603120, C029S603150, C029S603160, C427S127000, C427S128000, C360S324110, C360S324120
Reexamination Certificate
active
06757962
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic field sensing element whose electrical resistance changes in relation to the direction of magnetization of a free magnetic layer that is affected by both the direction of pinned magnetization of a pinned magnetic layer and an external magnetic field. The present invention more particularly relates to a method for manufacturing a magnetic field sensing element that is able to increase a longitudinal bias magnetic field and allows magnetization of the free magnetic layer to align in a direction for appropriately intersecting magnetization of the free magnetic layer.
2. Description of the Related Art
A magnetoresistive magnetic field sensing element is categorized as an AMR (Anisotropic Magnetoresistive) head when it includes an element that exhibits a magnetoresistive effect, and a GMR (Giant Magnetoresistive) head when it includes an element that exhibits a giant magnetoresistive effect. The AMR head has a monolayer structure in which the element exhibiting the magnetoresistive effect is composed of a magnetic material. The GMR head has, on the other hand, is a multilayer structure in which the element includes a plurality of laminated materials. While the giant magetoresistance effect can be generated by several different structures, a spin-valve type thin film magnetic element is commonly used because it has a high rate of change of magnetoresistivity against a weak external magnetic field.
FIG. 15
is a cross sectional view of our exemplary conventional spin-valve type thin film magnetic element as seen from the side facing a recording medium.
The spin-valve type thin film magnetic element shown in
FIG. 15
is a so-called bottom type single spin-valve type thin film magnetic element that includes one layer each of an antiferromagnetic layer, pinned magnetic layer, non-magnetic layer and free magnetic layer.
The spin-valve type thin film magnetic element shown in
FIG. 15
is composed of, from the bottom to the top, an underlayer
6
, an antiferromagnetic layer
1
, a pinned magnetic layer
2
, a non-magnetic layer
3
, a multilayer film
9
composed of a free magnetic layer
4
and protective layer
7
, a pair of hard bias layers (permanent magnetic layers)
5
formed on both side faces of the multilayer film
9
, and a pair of electrode layers
8
formed on hard bias layers
5
. A track width Tw is determined by the width on the surface of the multilayer film
9
.
Usually, a Fe—Mn or Ni—Mn alloy film is used for the antiferromagnetic layer
1
, a Ni—Fe alloy film is used for the pinned magnetic layer
2
and free magnetic layer
4
, a Cu film is used for the non-magnetic layer
3
, a Co—Pt film is used for the hard bias layers
5
, a Cr or W film is used for the electrode layers
8
, and a Ta film is used for the underlayer
6
and protective layer
7
.
As shown in
FIG. 15
, the pinned magnetic layer
2
is magnetized as a single magnetic domain in the Y-direction (the direction of a leak magnetic field from a recording medium: height direction) by an exchange coupling magnetic field with the antiferromagnetic layer
1
, and magnetization of the free magnetic layer
4
is aligned in the X-direction (track width direction) under the affect of the bias magnetic field from the hard bias layers
5
.
In other words, magnetization of the pinned magnetic layer
2
and magnetization of the free magnetic layer
4
are adjusted to be approximately perpendicular to each other.
A sense current flows from the electrode layers
8
to the pinned magnetic layer
2
, non-magnetic layer
3
and free magnetic layer
4
in this spin-valve type thin film magnetic element. The direction of magnetization of the free magnetic layer
4
changes from the X-direction to the Y-direction when the leaking magnetic field from the recording medium is applied in the Y-direction. Electrical resistance changes in relation to the variation of the magnetization direction in the free magnetic layer
4
and the direction of pinned magnetization of the pinned magnetic layer
2
(referred to as a magnetoresistive effect). The leaking magnetic field from the recording medium is sensed by voltage changes based on this changes of electrical resistance.
The spin-valve type thin film magnetic element as shown in
FIG. 15
is however, incompatible with high density recording. While magnetization of the pinned magnetic layer
2
is fixed in the Y-direction as a single magnetic domain, as described above, the hard bias layers
5
, magnetized in the X-direction, are provided at both sides of the pinned magnetic layer
2
. Consequently, magnetization at each side edge of the pinned magnetic layer
2
is particularly affected by the bias magnetic field from the hard bias layers
5
, thereby making it difficult to fix the direction of magnetization in the Y-direction.
Accordingly, the direction of magnetization of the free magnetic layer
4
, being in a single magnetic domain state by the influence of magnetization of the hard bias layers
5
in the X-direction, and the direction of magnetization of the pinned magnetic layer
2
is not perpendicular in the vicinity of the side edges of the multilayer film
9
. Furthermore, magnetization in the vicinity of the side edges of the free magnetic layer
4
is fixed by the strong magnetization from the hard bias layers
5
and is likely to be insensitive to the external magnetic field. As a result, a dead zone having a poor regenerative sensitivity is formed in the vicinity of the side edges of the multilayer film
9
.
Although the central portion of the multilayer film
9
substantially contributes to regeneration of the recording medium so as to serve as a sensitive zone manifesting the magnetoresistive effect (a practical track width), it has been difficult to accurately determine the width of the sensitive zone due to irregularity of the dead zone. Therefore, it also becomes difficult to properly comply with narrowing of the track width for high density recording that will be required in the near future.
FIG. 16
shows an improved spin-valve type thin film magnetic element provided for solving the foregoing problems.
FIG. 16
also shows a manufacturing process thereof. The same reference numerals as in
FIG. 15
denote the same layers.
A part of each side
4
a
of the free magnetic layer
4
is removed in this spin-valve type thin film magnetic element, and an ferromagnetic layer
13
is formed at each removed part. Second antiferromagnetic layers
10
, and electrodes
8
are continuously deposited on the ferromagnetic layers
13
using a lift-off resist
12
. The second antiferromagnetic layer
10
is made of an antiferromagnetic material. The ferromagnetic layer
13
is made of, for example, a NiFe alloy film.
In the spin-valve type thin film magnetic element shown in
FIG. 16
, a longitudinal bias magnetic field is applied by a so-called exchange bias method. An exchange coupling magnetic field is generated between the second antiferromagnetic layer
10
and ferromagnetic layer
13
by the exchange bias method. Accordingly, the longitudinal bias magnetic field in the X-direction is applied to the free magnetic layer
4
by a ferromagnetic coupling between the ferromagnetic layer
13
and free magnetic layer
4
.
Use of the exchange bias method can eliminate the dead zone as seen in the spin-valve type thin film magnetic element shown in FIG.
15
. Accordingly, the track width can be accurately and easily determined for high density recording that will be required in the near future.
The spin-valve type thin film magnetic element as shown in
FIG. 16
, however, also has the following problems. Since the tip portions
10
a
and
10
a
of the second antiferromagnetic layers
10
, deposited by using the lift-off resist layer
12
, are tapered, as shown in
FIG. 16
, the exchange coupling magnetic field generated between each tip portion
10
a
and ferromagnetic layer
13
becomes extremely small. Particularly, the exchange coupling magnetic field is not generated at all when the
Hasegawa Naoya
Ide Yosuke
Saito Masamichi
Tanaka Ken'ichi
Umetsu Eiji
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kim Paul
Tugbang A. Dexter
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