Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-01-17
2003-10-28
Heinz, A. J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06639762
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to spin valve thin-film magnetic devices, thin-film magnetic heads, and floating type magnetic heads, and to methods for manufacturing spin valve thin-film magnetic devices, and more particularly, relates to a spin valve thin-film magnetic device in which the asymmetry thereof can be reduced.
2. Description of the Related Art
A giant magnetoresistive head is provided with a device having magnetoresistance, in which the device has a multilayer structure composed of a plurality of materials exhibiting giant magnetoresistance. Among several types of structures exhibiting giant magnetoresistance, a spin valve thin-film magnetic device may be mentioned as a device which has a relatively simple structure and a high rate of change in resistance with respect to application of a minute external magnetic field. As a spin valve thin-film magnetic device, a single spin valve thin-film magnetic device and a dual spin valve thin-film magnetic device may be mentioned.
FIGS. 28 and 29
show schematic cross-sectional views of conventional spin valve thin-film magnetic devices.
FIG. 28
is a cross-sectional view observed from a recording medium side, and
FIG. 29
is a cross-sectional view observed from a track width direction side.
In
FIGS. 28 and 29
, an X
1
direction in the figure is the track width direction of the spin valve thin-film magnetic device, a Y direction in the figure is the direction of a leakage magnetic field from the magnetic recording medium, and a Z direction in the figure is the moving direction of the magnetic recording medium.
The spin valve thin-film magnetic device
9
shown in
FIGS. 28 and 29
is a so-called a dual spin valve thin-film magnetic device composed of a free magnetic layer provided on each surface thereof in the thickness direction with a nonmagnetic conductive layer, a fixed magnetic layer, and an antiferromagnetic layer, in that order, from the free magnetic layer.
In the spin valve thin-film magnetic device
9
, an underlying layer
115
is formed on an insulating layer
264
, and on the underlying layer
115
, a second antiferromagnetic layer
172
, a second fixed magnetic layer
151
, a second nonmagnetic conductive layer
132
, a free magnetic layer
141
, a first nonmagnetic conductive layer
131
, a first fixed magnetic layer
121
, a first antiferromagnetic layer
171
, and a cap layer
114
are sequentially formed, in that order.
In addition, on both sides of a laminate composed of the layers from the underlying layer
115
to the cap layer
114
in the X
1
direction in the figure, conductive layers
116
and
116
, interlayers
117
and
117
, bias layers
118
and
118
, and bias underlying layers
119
and
119
are formed.
The first and the second fixed magnetic layers
121
and
151
are magnetized respectively by exchange anisotropic magnetic fields which appear at the interfaces between the first fixed magnetic layers
121
and the first antiferromagnetic layers
171
and between the second fixed magnetic layer
151
and the second antiferromagnetic layer
172
, and the magnetization directions of the first and the second fixed magnetic layers
121
and
151
are fixed in the Y direction in the figure.
The free magnetic layer
141
is placed in a single domain state by the bias layers
118
and
118
, and the magnetization direction of the free magnetic layer
141
is aligned in the direction opposite to the X
1
direction in the figure, i.e., in the direction crossing the magnetization directions of the first and the second fixed magnetic layers
121
and
151
.
When the free magnetic layer
141
is placed in a single domain state, the generation of Barkhausen noise is prevented.
In this spin valve thin-film magnetic device
9
, when sensing current is imparted from the conductive layers
116
and
116
to the free magnetic layer
141
, the first and the second nonmagnetic conductive layers
131
and
132
, and the first and the second fixed magnetic layers
121
and
151
, and when leakage magnetic field from the magnetic recording medium running to the Z direction is imparted to the free magnetic layer
141
in the Y direction in the figure, the magnetization direction of the free magnetic layer
141
is changed from the direction opposite to the X
1
direction to the Y direction. The combination of the change in the magnetization direction in the free magnetic layer
141
and the magnetization directions of the first and the second fixed magnetic layers
121
and
151
changes the electrical resistance, and the leakage magnetic field from the recording medium is detected by the change in voltage in accordance with the change in the electrical resistance.
In a typical spin valve thin-film magnetic device, as shown in
FIG. 30
, when an external magnetic field from the recording medium is not applied, it is ideal for the magnetization direction H
3
of the free magnetic layer
141
to be perpendicular to the magnetic directions H
1
and H
2
of the first and the second fixed magnetic layers
121
and
151
.
However, in the conventional spin valve thin-film magnetic device
9
, ferromagnetic interlayer coupling occurs between the free magnetic layer
141
and the first and the second fixed magnetic layers
121
and
151
with the first and the second nonmagnetic conductive layers
131
and
132
, respectively, and as a result, magnetic moments H
4
and H
5
are generated by the ferromagnetic interlayer coupling magnetic fields. The directions of the magnetic moments H
4
and H
5
are parallel to the magnetization directions of the first and the second fixed magnetic layers
121
and
151
, i.e., the directions of the magnetic moments H
4
and H
5
are in the Y direction in the figure.
Consequently, since the magnetization direction H
3
of the free magnetic layer
141
is inclined by the magnetic field moments H
4
and H
5
to the Y direction so as to be H
6
, and hence, the magnetization direction H
6
of the free magnetic layer
141
cannot be perpendicular to the magnetization directions H
1
and H
2
of the first and the second fixed magnetic layers
121
and
151
, there is a problem in that an asymmetric property (hereinafter referred to as “asymmetry”) of wave shapes for reading is increased.
In addition, in the conventional spin valve thin-film magnetic device
9
, as shown in
FIG. 31
, when an external magnetic field from the recording medium is not applied, it is ideal for the magnetization direction H
3
of the free magnetic layer
141
to be perpendicular to the magnetic directions H
1
and H
2
of the first and the second fixed magnetic layers
121
and
151
. However, dipole magnetic fields H
14
and H
15
leaked from the first and the second fixed magnetic layers
121
and
151
, respectively, penetrate into the free magnetic layer
141
from the direction opposite to the Y direction in the figure and incline the magnetization direction H
3
of the free magnetic layer
141
toward the magnetization direction H
16
which is a direction opposite to the Y direction. As a result, the magnetization direction H
16
of the free magnetic layer
141
cannot be perpendicular to the magnetization directions H
1
and H
2
of the first and the second fixed magnetic layers
121
and
151
, and there is a problem in that the asymmetry wave shapes for reading, i.e., the asymmetry, is increased.
SUMMARY OF THE INVENTION
In consideration of the problems described above, an object of the present invention is to provides a spin valve thin-film magnetic device in which the inclination of the magnetization direction of the free magnetic layer can be prevented, and the asymmetry can be reduced, a thin-film magnetic head provided with the spin valve thin-film magnetic device, and a floating type magnetic head provided with the thin-film magnetic head. The present invention also provides a method for manufacturing the spin valve thin-film magnetic device described above.
To these ends, the structures described below are employed in the present invention.
A s
Hasegawa Naoya
Ide Yosuke
Koike Fumihito
Saito Masamichi
Tanaka Ken'ichi
Alps Electric Co. ,Ltd.
Blouin Mark S
Heinz A. J.
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