Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-12-05
2002-12-31
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C360S324110, C148S108000, C148S121000, C029S603080
Reexamination Certificate
active
06500570
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to spin-valve magnetoresistive elements exhibiting variable electrical resistance in response to the relationship between the magnetization vector of a free magnetic layer and the magnetization vector of a pinned magnetic layer, relates to thin-film magnetic heads provided therewith, and relates to methods for making the same. In particular, the present invention relates to a structure of a spin-valve magnetoresistive element having two separated pinned magnetic layers and relates to a technology for reducing asymmetry when a detecting current magnetic field is applied.
2. Description of the Background
Anisotropic magnetoresistive (AMR) heads using anisotropic magnetoresistive effects and giant magnetoresistive (GMR) heads using spin-dependent scattering phenomena of conduction electrons are known as magnetoresistive reading (MR) heads. One of the known GMR heads is a spin-valve head exhibiting a high magnetoresistive effect with respect to a low external magnetic field.
FIG. 22
is a cross-sectional view of a conventional spin-valve magnetoresistive element when viewed from a face opposing a recording medium. In this spin-valve magnetoresistive element, an antiferromagnetic layer
102
and a pinned magnetic layer
103
are deposited on a substrate
101
, in that order. The pinned magnetic layer
103
is in contact with the antiferromagnetic layer
102
, and an exchange coupling magnetic field (exchange anisotropic magnetic field) is generated at the interface between the pinned magnetic layer
103
and the antiferromagnetic layer
102
. The pinned magnetic layer
103
is magnetized, for example, in the Y direction in the drawing.
A nonmagnetic conductive layer
104
composed of copper or the like is formed on the pinned magnetic layer
103
, and free magnetic layer
105
is formed on the nonmagnetic conductive layer
104
. Hard biasing layers
106
formed of, for example, a cobalt-platinum (CoPt) alloy, are formed on both sides of the free magnetic layer
105
and are magnetized in the X direction in the drawing so that the free magnetic layer
105
is aligned to a single-domain state in the X direction. Thus, the variable magnetization of the free magnetic layer
105
and the pinned magnetization of the pinned magnetic layer
103
are substantially orthogonal to each other. Current lead layers
108
are provided on the hard biasing layers
106
.
In this spin-valve magnetoresistive element, a detecting current (sensing current) from the current lead layers
108
flows in the element. When the magnetization vector of the free magnetic layer
105
varies with a fringing magnetic field from a magnetic recording medium such as a hard disk, the electrical resistance varies due to the relationship with the pinned magnetization direction of the pinned magnetic layer
103
. Thus, the spin-valve magnetoresistive element detects the fringing magnetic field from the magnetic recording medium as a variable voltage due to the variable electrical resistance.
It is preferable that asymmetry of the output waveform be as small as possible in the spin-valve magnetoresistive element. The asymmetry is determined by the relationship between the variable magnetization vector of the free magnetic layer
105
and the pinned magnetization vector of the pinned magnetic layer
103
. When no external magnetic field is applied, it is preferable that the variable magnetization vector of the free magnetic layer
105
be orthogonal to the pinned magnetization vector of the pinned magnetic layer
103
.
With reference to a schematic view in shown in
FIG. 23
, the variable magnetization vector of the free magnetic layer
105
, which affects the output asymmetry, will be described. In the spin-valve magnetoresistive element, which reads magnetic information with a detecting current, the magnetization of the free magnetic layer
105
is affected by a demagnetizing field (dipole magnetic field) H
d
generated by the magnetization M
p
of the pinned magnetic layer
103
, a detecting current magnetic field (sensing current magnetic field) H
j
due to the detecting current J, and an interactive magnetic field H
int
due to interlayer interaction between the free magnetic layer
105
and the pinned magnetic layer
103
(a magnetic field, which affects so that the magnetization of the pinned magnetic layer
103
and the magnetization of the free magnetic layer
105
are parallel to each other).
It is considered that the asymmetry is reduced when these magnetic fields are relatively small with respect to the variable magnetization M
f
of the free magnetic layer
105
. Thus, when no external magnetic field is applied, canceling these magnetization vectors, as represented by the following equation, minimizes the asymmetry:
H
j
+H
d
+H
int
=0
As shown in
FIG. 23
, the magnetization of the free magnetic layer
105
, the detecting current magnetic field H
j
and the interactive magnetic field H
int
are in the same direction, whereas the demagnetizing field H
d
is in a different direction. Thus, in order to minimize the asymmetry, such a spin-valve magnetoresistive element is preferably produced so as to satisfy the equation H
d
=H
j
+H
int
based on the above relationship.
With reference to
FIGS. 25A
to
25
E, a method for making a spin-valve magnetoresistive element of a composite ferri-pinned structure shown in
FIG. 24
will be described. As shown in
FIG. 24
, in the composite ferri-pinned structure, the pinned magnetic layer is divided into a first pinned magnetic layer
111
and a second pinned magnetic layer
112
. In
FIGS. 25A
to
25
E, only an antiferromagnetic layer
110
, the first pinned magnetic layer
111
, the second pinned magnetic layer
112
, and a free magnetic layer
113
are depicted for simplicity, and thus a nonmagnetic interlayer provided between the first pinned magnetic layer
111
and the second pinned magnetic layer
112
and a nonmagnetic conductive layer provided between the second pinned magnetic layer
112
and the free magnetic layer
113
are not depicted. Moreover, the depicted layers are shifted to show magnetization vectors of these layers. The magnetic thickness of the first pinned magnetic layer
111
is smaller than the magnetic thickness of the second pinned magnetic layer
112
in which the magnetic thickness corresponds to the product of the intensity of the magnetization and the thickness.
The spin-valve magnetoresistive element shown in
FIG. 24
is produced as follows. The antiferromagnetic layer
110
composed of PtMn or the like, the first pinned magnetic layer
111
composed of Co or the like, the nonmagnetic interlayer (not shown in the drawing), the second pinned magnetic layer
112
composed of Co or the like, the nonmagnetic conductive layer (not shown in the drawing), and the free magnetic layer
113
composed of NiFe or the like are deposited on a substrate to form a composite. In this process, the first pinned magnetic layer
111
and the second pinned magnetic layer
112
are deposited while a magnetic field is applied in a direction perpendicular to the track width direction, then the nonmagnetic conductive layer is formed. Moreover, the first pinned magnetic layer
111
is formed while a magnetic field is applied in the track width direction. As a result, as shown in
FIG. 25A
, the magnetization vector of the first pinned magnetic layer
111
and the magnetization vector of the second pinned magnetic layer
112
are orthogonal to the magnetization vector of the free magnetic layer
113
.
With reference to
FIG. 25B
, the composite is annealed while an annealing magnetic field H
100
of 400 kA/m or more, which is perpendicular to the track width direction, is applied so that the PtMn antiferromagnetic layer
110
has an ordered structure. After the annealing, an intense exchange coupling magnetic field (exchange anisotropic magnetic field) occurs at the interface between the PtMn antiferromagnetic layer
110
and the first pinned magnetic layer
Hasegawa Naoya
Ide Yosuke
Koike Fumihito
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Resan Stevan A.
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