Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-07-26
2003-09-02
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S319000
Reexamination Certificate
active
06614629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head. More particularly, the present invention relates to a floating magnetic head having the thin film magnetic head.
2. Description of the Related Art
Magnetoresistive thin film magnetic heads include AMR (Anisotrophic Magnetoresistive) and GMR (Giant Magnetoresistive) heads. An AMR head has an element exhibiting a magnetoresistive effect. A GMR head has an element exhibiting a giant magnetoresistive effect.
In a GMR head, the element exhibiting the giant magnetoresistive effect has a multilayer structure. Among several types of multilayer structures creating the giant magnetoresistive effect, a relatively simple structure exhibiting a high rate of change in resistance with an external magnetic field is the structure of a spin-valve thin film magnetic element. This structure has at least a free magnetic layer, a pinned magnetic layer, and a nonmagnetic layer. Such spin-valve thin film magnetic elements include single and dual spin-valve thin film magnetic elements.
In addition, there are different systems for orienting the magnetization direction of the free magnetic layer including hard and exchange bias systems. In recent years, the exchange bias system has become more widely used because it is adaptable to the track narrowing associated with increases in magnetic recording density.
FIG. 31
shows a thin film magnetic head
501
comprising an exchange bias system.
FIG. 32
shows the structure of a principal portion of a floating magnetic head
500
comprising the thin film magnetic head
501
shown in
FIG. 31 and a
write inductive head
503
, as viewed from the surface facing a medium.
The floating magnetic head
500
comprises the thin film magnetic head
501
and the inductive head
503
, which are laminated on the trailing end
504
a
of a floating slider
504
.
The thin film magnetic head
501
is a reproduction-only magnetic head, and comprises a pair of shield layers
507
and
508
laminated on both sides of a spin-valve thin film magnetic element
502
in the direction of the thickness. Insulating layers
505
and
506
are provided between the spin valve thin film magnetic element
502
, and the shield layers
507
,
508
respectively.
In
FIGS. 31 and 32
, the Z direction is the movement direction of a magnetic recording medium. The Y direction is the direction of a leakage magnetic field from the magnetic recording medium. The X
1
direction is the direction of the track width of the thin film magnetic head
501
and the inductive head
503
.
As shown in
FIG. 32
, the floating magnetic head
500
comprises an insulating layer
509
laminated on the trailing side end
504
a
of the floating slider
504
. The lower shield layer
508
, the spin-valve thin film magnetic element
502
, the upper shield layer
507
, a gap layer
510
, and an upper core layer
511
, are laminated in turn on the insulating layer
509
.
As shown in
FIG. 32
, the thin film magnetic head
501
comprises the spin-valve thin film magnetic element
502
, and the shield layers
507
and
508
. The inductive head
503
comprises the lower core layer (upper shield layer)
507
, the gap layer
510
and the upper core layer
511
.
In the inductive head
503
, the upper and lower core layers
511
and
507
are arranged opposite to each other with the gap layer
510
provided therebetween to form a write magnetic gap G
1
.
The upper shield layer
507
is also the lower core layer of the inductive head
503
.
The spin-valve thin film magnetic element
502
is a bottom-type single spin-valve thin film element comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer, which are laminated in turn.
In the spin-valve thin film magnetic element
502
, the insulating layer
506
is made of Al
2
O
3
and is laminated on the lower shield layer
508
. An antiferromagnetic layer
512
, a pinned magnetic layer
513
, a nonmagnetic conductive layer
514
made of Cu or the like, and a free magnetic layer
515
are laminated in turn on the insulating layer
506
.
A pair of bias layers
516
are laminated on the free magnetic layer
515
with a pair of ferromagnetic layers
518
provided therebetween. The ferromagnetic layers
518
are made of, for example, a NiFe alloy and are spaced along the X
1
direction shown in FIG.
31
.
A pair of conductive layers
517
made of Cu are laminated on the bias layers. An insulating layer
505
made of Al
2
O
3
is laminated to cover the conductive layers
517
and the free magnetic layer
505
. The upper shield layer
507
is laminated on the insulating layer
515
.
The antiferromagnetic layer
512
comprises an antiferromagnetic material such as a PtMn alloy, or the like. The antiferromagnetic layer
512
is laminated in contact with the pinned magnetic layer
513
so that an exchange coupling magnetic field (exchange anisotropic magnetic field) is exhibited in the interface between the pinned magnetic layer
513
and the antiferromagnetic layer
512
. The magnetization direction of the pinned magnetic layer
513
is pinned in the Y direction as shown in the drawings.
Each of the bias layers
516
is made of an antiferromagnetic material such as an IrMn alloy or the like. The bias layers
516
are laminated in contact with the ferromagnetic layers
518
so that an exchange coupling magnetic field (exchange anisotropic magnetic field) is exhibited in each of the interfaces between the bias layers
516
and the ferromagnetic layers. The magnetization direction of the free magnetic layer
515
is oriented in the X
1
direction shown in the drawings by the exchange coupling magnetic field. As a result, the free magnetic layer
515
is put into a single magnetic domain state to suppress Barkhausen noise.
Therefore, the magnetization direction of the free magnetic layer
515
crosses the magnetization direction of the pinned magnetic layer
513
.
In addition, the pair of bias layers
516
are laminated with a space therebetween to produce a portion where the bias layers
516
are not laminated on the free magnetic layer
515
. This portion serves as a track portion G
2
of the thin film magnetic head
501
.
In the thin film magnetic head
501
, the magnetization direction of the free magnetic layer
515
is oriented in the X
1
direction and changes with a leakage magnetic field from a recording medium such as a hard disk. The magnetization of the pinned magnetic layer
513
is pinned in the Y direction as shown in the drawings. Accordingly, the changing orientation of the free magnetic layer
515
changes the electric resistance of the spin-valve thin film magnetic element. The voltage changes based on the change in the electric resistance, thus detecting the leakage magnetic field from the recording medium.
In the conventional thin film magnetic head
501
, as shown in
FIG. 31
, the pair of bias layers
516
and the conductive layers
517
are laminated on the free magnetic
515
. A step
505
a
occurs in the insulating layer
505
near the write track portion G
2
. This step
505
a
is patterned by the gap layer
510
through the upper shield layer
507
to warp the shape of the write magnetic gap G
1
of the inductive head
503
, as shown in FIG.
32
. Consequently, a magnetic recording pattern recorded on the magnetic recording medium is also warped, thus causing potential errors during reproduction.
In manufacturing the floating magnetic head
500
, a plurality of thin film magnetic heads
501
and inductive heads
503
are formed on a substrate by a thin film deposition technique. The substrate is cut. To determine the gap depth, the medium-facing surface must be polished with a grinding stone or the like. Namely, the surface of the drawing of
FIG. 32
is the polished surface.
In the conventional thin film magnetic head
501
, smearing occurs during polishing. The grind stone causes small portions of the polished surfaces of the shield layers
507
and
508
which are made of metal, to extend on the
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Tupper Robert S.
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