Spin-valve thin-film magnetic element

Details Spin-valve thin-film magnetic element Spin-valve thin-film magnetic element

2001-05-22

2003-07-01

Kiliman, Leszek (Department: 1773)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S611000, C428S622000, C428S627000, C428S629000, C428S632000, C428S639000, C428S641000, C428S660000, C428S607000, C428S670000, C428S678000, C428S900000, C360S112000, C324S252000

Reexamination Certificate

active

06586121

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spin-valve thin-film magnetic element in which electrical resistance changes due to the relationship between the pinned magnetization direction of a pinned magnetic layer and the magnetization direction of a free magnetic layer which is influenced by an external magnetic field, and to a thin-film magnetic head provided with the spin-valve thin-film magnetic element. More particularly, the invention relates to a technique which can improve the rate of resistance change and which can decrease the coercive force of the free magnetic layer.
2. Description of the Related Art
A spin-valve thin-film magnetic element is one type of giant magnetoresistive (GMR) element exhibiting a giant magnetoresistance effect, and detects a recorded magnetic field from a magnetic recording medium, such as a hard disk.
The spin-valve thin-film magnetic element has a relatively simple structure among GMR elements, and has a high rate of resistance change relative to an external magnetic field, thus, the resistance changes in response to a weak magnetic field.
FIG. 11
is a sectional view of a conventional spin-valve thin-film magnetic element, viewed from a surface facing a recording medium (air bearing surface; ABS).
The spin-valve thin-film magnetic element shown in
FIG. 11
is a so-called “top-type” single spin-valve thin-film magnetic element in which an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer, one each, are deposited.
For the spin-valve thin-film magnetic element, a magnetic recording medium, such as a hard disk, travels in the Z direction in the drawing, and a fringing magnetic field from the magnetic recording medium is directed in the Y direction.
As shown in
FIG. 11
, an underlying layer
121
is provided on a substrate. A free magnetic layer
125
, a nonmagnetic conductive layer
124
, a pinned magnetic layer
123
, an antiferromagnetic layer
122
, and a protective layer
127
are formed in that order on the underlying layer
121
.
Hard bias layers
126
are provided on both sides, in the track width (Tw) direction, of the underlying layer
121
, the pinned magnetic layer
123
, the nonmagnetic conductive layer
124
, and the free magnetic layer
125
, and electrode layers
128
are formed on the hard bias layers
126
. Reference numeral
129
represents a laminate, which has a trapezoidal cross-section, including the underlying layer
121
, the free magnetic layer
125
, the nonmagnetic conductive layer
124
, the pinned magnetic layer
123
, the antiferromagnetic layer
122
, and the protective layer
127
.
In the spin-valve thin-film magnetic element, the magnetization direction of the pinned magnetic layer
123
is pinned antiparallel to the Y direction.
The underlying layer
121
is composed of tantalum (Ta) or the like, and the antiferromagnetic layer
122
is composed of an IrMn alloy, an FeMn alloy, an NiMn alloy, or the like. The pinned magnetic layer
123
and the free magnetic layer
125
are composed of Co, an NiFe alloy, or the like, the nonmagnetic conductive layer
124
is composed of copper (Cu), the hard bias layers
126
are composed of a cobalt-platinum (Co—Pt) alloy, and the electrode layers
128
are composed of a good conductor, such as Cu. In the spin-valve thin-film magnetic element having the structure shown in
FIG. 11
, the free magnetic layer
125
has a layered structure including an NiFe layer
125
A and a Co layer
125
B which is in contact with the nonmagnetic conductive layer
124
.
FIG. 12
is a sectional view of another conventional spin-valve thin-film magnetic element, viewed from a surface facing a recording medium (ABS).
The spin-valve thin-film magnetic element shown in
FIG. 12
is a so-called “bottom-type” single spin-valve thin-film magnetic element in which an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer, one each, are deposited.
For the spin-valve thin-film magnetic element, a magnetic recording medium, such as a hard disk, travels in the Z direction in the drawing, and a fringing magnetic field from the magnetic recording medium is directed in the Y direction.
The conventional spin-valve thin-film magnetic element shown in
FIG. 12
includes a laminate
109
in which an underlying layer
106
, an antiferromagnetic layer
101
, a pinned magnetic layer
102
, a nonmagnetic conductive layer
102
, a free magnetic layer
104
, and a protective layer
107
are deposited in that order on a substrate, a pair of hard bias layers
105
, and electrode layers
108
formed on the hard bias layers
105
.
The underlying layer
106
is composed of Ta or the like, and the antiferromagnetic layer
101
is composed of an NiO alloy, an FeMn alloy, an NiMn alloy, or the like. The pinned magnetic layer
102
and the free magnetic layer
104
are composed of Co, an NiFe alloy, or the like, the nonmagnetic conductive layer
103
is composed of Cu, the hard bias layers
105
are composed of a Co—Pt alloy, and the electrode layers
108
are composed of a good conductor, such as Cu.
Since the pinned magnetic layer
102
is formed in contact with the antiferromagnetic layer
101
, an exchange coupling magnetic field (exchange anisotropic magnetic field) is produced at the interface between the pinned magnetic layer
102
and the antiferromagnetic layer
101
, and the pinned magnetization of the pinned magnetic layer
102
is pinned, for example, in the Y direction in the drawing.
Since the hard bias layers
105
are magnetized in the X
1
direction in the drawing, the variable magnetization of the free magnetic layer
104
is aligned in the X
1
direction. Thereby, the variable magnetization of the free magnetic layer
104
and the pinned magnetization of the pinned magnetic layer
102
are perpendicular to each other.
The free magnetic layer
104
includes an NiFe sub-layer
104
A and a Co sub-layer
104
B which is in contact with the nonmagnetic conductive layer
103
.
In the spin-valve thin-film magnetic element shown in
FIG. 12
, a sensing current is applied from the electrode layer
108
formed on the hard bias layer
105
to the pinned magnetic layer
102
, the nonmagnetic conductive layer
103
, and the free magnetic layer
104
. A magnetic recording medium, such as a hard disk, travels in the Z direction in the drawing, and when a fringing magnetic field from the magnetic recording medium is applied in the Y direction, the magnetization direction of the free magnetic layer
104
is rotated from the X
1
direction to the Y direction. At this stage, electrical resistance changes due to the relationship between the varied magnetization direction of the free magnetic layer
104
and the pinned magnetization direction of the pinned magnetic layer
102
, which is referred to as a magnetoresistance (MR) effect, and the fringing magnetic field from the magnetic recording medium is detected by a voltage change based on the change in the electrical resistance.
With respect to the spin-valve thin-film magnetic element shown in
FIG. 11
, a structure has been proposed, in which a back layer composed of a nonmagnetic conductive material, such as Au, Ag, or Cu, is formed at the underlying layer
121
side of the free magnetic layer
125
so that the mean free path of spin-up electrons, that contribute to the magnetoresistive effect, is extended, that is, a so-called “spin filter effect” is used, thus enabling to obtain a large rate of resistance change (&Dgr;R/R).
However, in the structure shown in
FIG. 11
, when a back layer composed of Cu is added between the free magnetic layer
125
and the underlying layer
121
composed of Ta, if the Cu back layer is deposited at a thickness of approximately several ten angstroms on the Ta underlying layer
121
, it is difficult to deposit the back layer of Cu with satisfactory crystal orientation, resulting in a decrease in orientation of the back layer, and thus it is difficult to obtain a large rate of resistance c

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