Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-10-03
2003-08-19
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S324110
Reexamination Certificate
active
06608739
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spin valve thin film magnetic element, a thin film magnetic head, and a method of manufacturing the spin valve thin film magnetic element. Particularly, the present invention relates to a spin valve thin film magnetic element comprising a synthetic ferrimagnetic free layer comprising two magnetic layers with a nonmagnetic intermediate layer provided therebetween.
2. Description of the Related Art
Magnetoresistive magnetic heads include a MR (Magnetoresistive) head comprising an element exhibiting a magnetoresistive effect, and a GMR (Giant Magnetoresistive) head comprising an element exhibiting a giant magnetoresistive effect. In the MR head, the element exhibiting the magnetoresistive effect has a single layer structure comprising a magnetic material. On the other hand, in the GMR head, the element exhibiting the magnetoresistive effect has a multilayer structure in which a plurality of materials are laminated. Of several types of structures creating the giant magnetoresistive effect, a relatively simple structure exhibiting a high rate of change in resistance with an external magnetic field is a spin valve thin film magnetic element.
Recently, high-density magnetic recording has been increasingly required, and a spin valve thin film magnetic element adaptable to high density recording has increasingly attracted attention.
A conventional spin valve thin film magnetic element is described with reference to the drawings.
FIG. 19
is a schematic sectional view showing a conventional spin valve thin film magnetic element
101
, as viewed from the magnetic recording medium side, and
FIG. 20
is a schematic sectional view of the spin valve thin film magnetic element
101
, as viewed from the track width direction.
A reproducing thin film magnetic head comprises the spin valve thin film magnetic element
101
, and shield layers formed above and below the spin valve thin film magnetic element
101
with gap layers provided therebetween. In addition, a recording inductive head may be laminated on the reproducing thin film magnetic head.
The thin film magnetic head is provided at the trailing side end of a floating slider together with the inductive head to form a thin film magnetic head for detecting a recording magnetic field of a magnetic recording medium such as a hard disk, or the like.
In
FIGS. 19 and 20
, the Z direction coincides with the movement direction of the magnetic recording medium, the Y direction coincides with the direction of a leakage magnetic field from the magnetic recording medium, and the X
1
direction coincides with the track width direction of the spin valve thin film magnetic element.
The spin valve thin film magnetic element
101
shown in
FIGS. 19 and 20
is a bottom-type single spin valve thin film magnetic element in which an antiferromagnetic layer
103
, a pinned magnetic layer
104
, a nonmagnetic conductive layer
105
, and a free magnetic layer
111
are laminated in turn.
In
FIGS. 19 and 20
, reference numeral
100
denotes an insulating layer made of Al
2
O
3
or the like, and reference numeral
102
denotes a base layer made of Ta (tantalum) or the like, and laminated on the insulating layer
100
. The antiferromagnetic layer
103
is laminated on the base layer
102
, the pinned magnetic layer
104
is laminated on the antiferromagnetic layer
103
, and the nonmagnetic conductive layer
105
made of Cu is laminated on the pinned magnetic layer
104
. Furthermore, the free magnetic layer
111
is laminated on the nonmagnetic conductive layer
105
, and a protecting layer
120
made of Ta or the like is laminated on the free magnetic layer
111
.
The layers from the base layer
120
to the protecting layer
120
are laminated in turn to form a lamination
121
having a substantially trapezoidal sectional shape having a width corresponding to the track width.
The pinned magnetic layer
104
is made of, for example, Co, and laminated in contact with the antiferromagnetic layer
103
. An exchange coupling magnetic field (exchange anisotropic magnetic field) occurs in the interface between the pinned magnetic layer
104
and the antiferromagnetic layer
103
so that the magnetization direction of the pinned magnetic layer
104
is pinned in the Y direction.
The free magnetic layer
111
comprises first and second free magnetic layers
110
and
108
with a nonmagnetic intermediate layer
109
provided therebetween. The first free magnetic layer
110
is provided on the protecting layer side of the nonmagnetic intermediate layer
109
, and the second free magnetic layer
108
is provided on the nonmagnetic conductive layer side of the nonmagnetic intermediate layer
109
.
The thickness t
1
of the first free magnetic layer
110
is larger than the thickness t
2
of the second free magnetic layer
108
.
The first free magnetic layer
110
is made of a ferromagnetic material such as a NiFe alloy or the like, and the nonmagnetic intermediate layer
109
is made of a nonmagnetic material such as Ru or the like.
The second free magnetic layer
108
comprises an anti-diffusion layer
106
, and a ferromagnetic layer
107
, both of which are made of a ferromagnetic material. For example, the anti-diffusion layer
106
is made of Co, and the ferromagnetic layer
107
is made of a NiFe alloy. The first free magnetic layer
110
and the ferromagnetic layer
107
are preferably made of the same material.
The anti-diffusion layer
106
is provided for preventing mutual diffusion between the ferromagnetic layer
107
and the nonmagnetic conductive layer
105
to increase the GMR effect (&Dgr;MR) produced in the interface with the nonmagnetic conductive layer
105
.
Assuming that saturation magnetizations of the first and second free magnetic layers
110
and
108
are M
1
and M
2
, respectively, the magnetic thicknesses of the first and second free magnetic layers
110
and
108
are M
1
·t
1
and M
2
·t
2
, respectively.
Since the second free magnetic layer
108
comprises the anti-diffusion layer
106
and the ferromagnetic layer
107
., the magnetic thickness M
2
·t
2
of the second free magnetic layer
108
is the sum of the magnetic thickness of the anti-diffusion layer
106
, and the magnetic thickness of the ferromagnetic layer
107
.
The free magnetic layer
111
is formed to satisfy the relation M
1
·t
1
>M
2
·t
2
between the magnetic thicknesses of the first and second free magnetic layers
110
and
108
.
Actually, the saturation magnetization of Co which constitutes the anti-diffusion layer
106
is higher than that of the NiFe alloy which constitutes the ferromagnetic layer
107
and the first free magnetic layer
110
, and thus the thickness t
1
of the first free magnetic layer
110
is set to be extremely larger than the thickness t
2
of the second free magnetic layer
108
in order to establish the relation M
1
·t
1
>M
2
·t
2
.
The first and second free magnetic layers
110
and
108
are antiferromagnetically coupled with each other. Namely, when the magnetization direction of the first free magnetic layer
110
is oriented in the X
1
direction shown in the drawings by bias layers
132
, the magnetization direction of the second free magnetic layer
108
is oriented in the direction opposite to the X
1
direction.
Since the magnetic thicknesses of the first and second free magnetic layers
110
and
108
have the relation M
1
·t
1
>M
2
·t
2
, magnetization of the first free magnetic layer
110
remains so that the magnetization direction of the entire free magnetic layer
111
is oriented in the X
1
direction. At this time, the magnetic effective thickness of the free magnetic layer
111
is (M
1
·t
1
−M
2
·t
2
).
In this way, the first and second free magnetic layers
110
and
108
are antiferromagnetically coupled with each other so that the magnetization directions thereof are antiparallel to each other, and the magnetic thicknesses thereof have the relation M
1
·t
1
>M
2
·t
2
. Therefore, the first and second free magnetic lay
Hasegawa Naoya
Ide Yosuke
Saito Masamichi
Tanaka Ken'ichi
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Evans Jefferson
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