Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-01-30
2003-08-19
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06608740
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spin-valve thin-film magnetic element which undergoes a change in electric resistance in relation to the magnetization vector of a pinned magnetic layer and a magnetization vector of a free magnetic layer affected by an external magnetic field, and to a thin-film magnetic head provided with the spin-valve thin-film magnetic element. In particular, the present invention relates to a technology suitable for a spin-valve thin-film magnetic element which includes a free magnetic layer having improved soft magnetic characteristics and thus exhibits an enhanced rate of change in resistance.
2. Description of the Related Art
A spin-valve thin-film magnetic element is a type of giant magnetoresistive element (GMR) exhibiting giant magnetoresistive effects and detects recorded magnetic fields from a recording medium such as a hard disk. The spin-valve thin-film magnetic element has a relatively simple structure among GMRs, and exhibits a high rate of change in resistance in response to external magnetic fields and thus a change in resistance by a weak magnetic field.
FIG. 17
is a cross-sectional view of an exemplary conventional spin-valve thin-film magnetic element when viewed from a face opposing a recording medium (air bearing surface: ABS). This spin-valve thin-film magnetic element is a bottom-type single spin-valve thin-film magnetic element including an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. In this spin-valve thin-film magnetic element, a recording medium such as a hard disk moves in the Z direction in the drawing, and a leakage magnetic field occurs in the Y direction in the drawing.
In the conventional spin-valve thin-film magnetic element, a composite
109
is formed on a substrate. The composite
109
includes an underlying layer
106
, an antiferromagnetic layer
101
, a pinned magnetic layer
102
, a nonmagnetic conductive layer
103
, a free magnetic layer
104
, and a protective layer
107
. Moreover, the spin-valve thin-film magnetic element includes, from the substrate side, a pair of hard bias layers
105
and a pair of electrode layers
108
formed on the hard bias layers, both provided on two side faces of the composite
109
.
The underlying layer
106
is composed of tantalum (Ta) or the like, whereas the antiferromagnetic layer
101
is composed of a NiO alloy, an FeMn alloy, or NiMn alloy. The pinned magnetic layer
102
and the free magnetic layer
104
are composed of elemental cobalt (Co) or a NiFe alloy. The nonmagnetic conductive layer
103
is composed of a copper (Co) film. In addition, the hard bias layers
105
are composed of a cobalt-platinum (Co—Pt) alloy and the electrode layers
108
are composed of Cu or the like.
Since the pinned magnetic layer
102
is in contact with the antiferromagnetic layer
101
, an exchange coupling magnetic field (exchange anisotropic magnetic field) is generated at the interface between the pinned magnetic layer
102
and the antiferromagnetic layer
101
. The magnetization vector of the pinned magnetic layer
102
is pinned, for example, in the Y direction in the drawing.
The hard bias layers
105
are magnetized in the X
1
direction in the drawing to orient the variable magnetization of the free magnetic layer
104
in the X
1
direction in the drawing. As a result, the variable magnetization vector of the free magnetic layer
104
and the pinned magnetization vector of the pinned magnetic layer
102
intersect each other.
The free magnetic layer
104
includes a NiFe sublayer
104
A and a Co sublayer
104
B in contact with the nonmagnetic conductive layer
103
.
In this spin-valve thin-film magnetic element, a sensing current is applied from electrode layers
108
to the pinned magnetic layer
102
, the nonmagnetic conductive layer
103
, and the free magnetic layer
104
. When a leakage magnetic field is applied in the Y direction in the drawing from the magnetic recording medium moving in the Z direction in the drawing, the magnetization vector of the free magnetic layer
104
changes from the X
1
direction to the Y direction in the drawing. Such a change in the magnetization vector of the free magnetic layer
104
changes electrical resistance in relation to the pinned magnetization vector of the pinned magnetic layer
102
(this change is referred to as magnetoresistive (MR) effects). As a result, the leakage magnetic field from the magnetic recording medium is detected as a change in voltage due to the change in the electrical resistance.
In such a spin-valve thin-film magnetic element, a surface oxide layer is formed at the interface between the NiFe sublayer
104
A and the Co sublayer
104
B in the free magnetic layer
104
. This oxide layer causes an increase in resistance of the element and thus a decrease in the rate of change in resistance (&Dgr;R/R) in the GMR effects, resulting in deterioration of read output characteristics of the spin-valve thin-film magnetic element.
Moreover, the thickness of the Co sublayer
104
B is set to be approximately 3 to 5 angstroms; hence, interdiffusion may occur between the Cu nonmagnetic conductive layer
103
and the NiFe sublayer
104
A. Such interdiffusion of Cu and NiFe causes deterioration of characteristics of these layers and thus a decrease in the rate of change in resistance (&Dgr;R/R) in the GMR effects, resulting in deterioration of read output characteristics of the spin-valve thin-film magnetic element.
A possible means for solving the above problems is to provide a single Co layer configuration in the free magnetic layer
104
. In this case, however, the coercive force Hc of the free magnetic layer
104
is undesirably large and the variation of the magnetization vector in the free magnetic layer
104
is less sensitive to the leakage magnetic field from the exterior, resulting in a reduction in detection sensitivity.
Another possible means is to provide a NiFe single free magnetic layer
104
. In this case, there is no barrier layer for preventing interdiffusion of Cu and NiFe. The interdiffusion of Cu and NiFe causes significant deterioration of characteristics of these layers and thus a decrease in the rate of change in resistance (&Dgr;R/R) in the GMR effects, resulting in significant deterioration of read output characteristics of the spin-valve thin-film magnetic element.
FIG. 18
is a cross-sectional view of another conventional spin-valve thin-film magnetic element when viewed from a surface opposing a recording medium (ABS). This spin-valve thin-film magnetic element is a top-type single spin-valve thin-film magnetic element including an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. In this spin-valve thin-film magnetic element, a recording medium such as a hard disk moves in the Z direction in the drawing, and a leakage magnetic field occurs in the Y direction in the drawing.
With reference to
FIG. 18
, an underlying layer
121
is formed on a substrate. A free magnetic layer
125
is formed on the underlying layer
121
, and a nonmagnetic conductive layer
124
is formed on the free magnetic layer
125
. A pinned magnetic layer
123
is formed on the nonmagnetic conductive layer
124
, and an antiferromagnetic layer
122
is formed on the pinned magnetic layer
123
. Moreover, a protective layer
127
is formed on the antiferromagnetic layer
122
. These layers define a composite
129
. A pair of hard bias layers
126
and a pair of electrode layers
128
are formed on both sides of the composite
129
.
In this spin-valve thin-film magnetic element, the pinned magnetic layer
123
is magnetized in a direction which is opposite to the Y direction in the drawing.
The underlying layer
121
is composed of tantalum or the like, and the antiferromagnetic layer
122
is composed of an IrMn alloy, an FeMn alloy, or a NiMn alloy. The pinned magnetic layer
123
and the free magnetic layer
125
are composed of elemental cobalt or a
Hasegawa Naoya
Ide Yosuki
Saito Masamichi
Tanaka Ken'ichi
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Cao Allen
LandOfFree
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