Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
2003-08-14
2004-10-19
Donovan, Lincoln (Department: 2832)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
C360S112000, C360S324120, C336S232000
Reexamination Certificate
active
06806804
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spin valve magnetic detecting element, and particularly to a magnetic detecting element capable of effectively improving a change &Dgr;R in resistance.
2. Description of the Related Art
FIG. 10
is a sectional view showing a conventional magnetic detecting element.
The spin valve magnetic detecting element shown in
FIG. 10
comprises a multilayer film
6
comprising an antiferromagnetic layer
2
, a pinned magnetic layer
3
, a nonmagnetic material layer
4
, and a synthetic ferrimagnetic free magnetic layer
5
including a first free magnetic sub-layer
5
a
, a nonmagnetic intermediate layer
5
b
, and a second free magnetic sub-layer
5
c
, which are laminated in that order from the bottom. The spin valve magnetic detecting element further comprises electrode layers
1
and
7
formed below and above the multilayer film
6
, hard bias layer
8
formed on both sides of the free magnetic layer
5
, insulating layers
9
formed below the respective hard bias layers
8
, and insulating layers
10
formed on the respective hard bias layers
8
.
The antiferromagnetic layer
2
is made of PtMn, and each of the pinned magnetic layer
3
, and the first and second free magnetic sub-layers
5
a
and
5
c
of the free magnetic layer
5
is made of CoFe, the nonmagnetic intermediate layer
5
b
of the free magnetic layer
5
is made of Ru, the nonmagnetic material layer
4
is made of Cu, each of the hard bias layers
8
is made of a hard magnetic material such as CoPt or the like, each of the insulating layers
9
and
10
is made of alumina, and each of the electrode layers
1
and
7
is made of an electrically conductive material.
The magnetic detecting element shown in
FIG. 10
is referred to as a “spin valve magnetic detecting element”, for detecting a recording magnetic field from a recording medium such as a hard disk or the like.
The magnetic detecting element shown in
FIG. 10
is a CPP (current perpendicular to the plane) type magnetic detecting element in which a current flows perpendicularly to the film plane of each of the layers of the multilayer film
6
.
The magnetization direction of the pinned magnetic layer
3
is pinned in the Y direction shown in the drawing. For example, when the magnetic thickness (saturation magnetization Ms×thickness t) of the second free magnetic sub-layer
5
c
is larger than that of the first free magnetic sub-layer
5
a
, the magnetization direction of the second free magnetic sub-layer
5
c
with no external magnetic field applied thereto is oriented in the track width direction (the X direction shown in the drawing) and put into a single magnetic domain state by a longitudinal bias magnetic field from each hard bias layer
8
. On the other hand, the magnetization direction of the first free magnetic sub-layer
5
a
is oriented antiparallel to the track width direction. The magnetization direction of the whole free magnetic layer
5
coincides with the magnetization direction of the second free magnetic sub-layer
5
c
having a larger magnetic thickness. With an external magnetic field applied, magnetizations of the first and second free magnetic sub-layers
5
a
and
5
c
rotate while maintaining a synthetic ferrimagnetic state to change the electric resistance of the multilayer film
6
. The change in the electric resistance is taken as a change in voltage or a change in current to detect the external magnetic field.
When a current flows through a magnetic material, the magnetic material has different values of resistivity for majority conduction electrons and for minority conduction electrons.
In the magnetic material, the magnetic moment of a constituent magnetic atom is mainly defined by the orbital magnetic moment and spin magnetic moment of a
3
d
-or
4
f
-orbit electron. Basically, the number of
3
d
-or
4
f
-orbit spin-up electrons is different from the number of
3
d
-or
4
f
-orbit spin-down electrons. Of the 3d- or
4
f
-orbit spin-up electrons and spin-down electrons, the spin of a larger number of the electrons is referred to as a “majority spin”, and the spin of a smaller number of the electrons is referred to as a “minority spin”.
On the other hand, a current flowing through the magnetic material contains substantially the same number of spin-up and spin-down conduction electrons. Of the spin-up and spin-down conduction electrons, the conduction electrons having the same spin as the majority spin of the magnetic material are referred to as “majority conduction electrons”, and the conduction electrons having the same spin as the minority spin are referred to as “minority conduction electrons”.
Assuming that a resistivity value of a magnetic material for the minority conduction electrons is &rgr;↓, and a resistivity value for the majority conduction electrons is &rgr;↑, a &bgr; value inherent to the magnetic material can be defined by the following relational expression:
&rgr;↓/&rgr;↑=(1+&bgr;)/(1−&bgr;)(−1≦&bgr;≦1)
Namely, when the &bgr; value of the magnetic material is positive (&bgr;>0), &rgr;↓>&rgr;↑ is established, and thus the majority conduction electrons easily flow through the magnetic material. On the other hand, when the &bgr; value of the magnetic material is negative (&bgr;<0), &rgr;↓<&rgr;↑ is established, and thus the minority conduction electrons easily flow through the magnetic material.
In a laminate of a magnetic layer made of a magnetic material and a nonmagnetic layer made of a nonmagnetic material, an interface resistance occurs at the interface between the magnetic layer and the nonmagnetic layer.
The interface resistance also shows different values for the majority conduction electrons and the minority conduction electrons.
Assuming that the interface resistance value for the minority conduction electrons is r↓, and the interface resistance value for the majority conduction electrons is r↑, a &ggr; value inherent to a combination of a magnetic material and a nonmagnetic material can be defined by the following relational expression:
r↓/r↑=(1+&ggr;)/(1−&ggr;)(−1≦&ggr;≦1)
Namely, when the &ggr; value is positive (&ggr;>0), r↓>r↑ is established, and thus the majority conduction electrons easily flow at the interface. On the other hand, when the y value is negative (&ggr;<0), r↓<r↑ is established, and thus the minority conduction electrons easily flow at the interface.
In the magnetic detecting element shown in
FIG. 10
, the pinned magnetic layer
2
, and the first and second free magnetic sub-layers
5
a
and
5
c
are made of magnetic materials CoFe having the same composition. CoFe shows a positive &bgr; value. Namely, the majority conduction electrons easily flow through each of the pinned magnetic layer
2
and the first and second free magnetic sub-layers
5
a
and
5
c.
The nonmagnetic material layer
4
is made of Cu. Also, both the interface between the nonmagnetic material layer
4
and the pinned magnetic layer
3
and the interface between the nonmagnetic material layer
4
and the first free magnetic sub-layer
5
a
show positive &ggr; values.
The nonmagnetic intermediate layer
5
b
is made of Ru. Also, both the interface between the first free magnetic sub-layer
5
a
and the nonmagnetic intermediate layer
5
b
and the interface between the second free magnetic sub-layer
5
c
and the nonmagnetic intermediate layer
5
b
show negative &ggr; values.
FIG. 11
shows a relation between &bgr; and &ggr; values and each magnetic layer.
FIG. 11
schematically shows the layers related to the magnetoresistive effect of the magnetic detecting element shown in FIG.
10
. In
FIG. 11
, the magnetization direction of each of the pinned magnetic layer
3
and the first and second free magnetic sub-layers
5
a
and
5
c
is shown by an arrow. The majority spin of the electrons related to magnetization of a magnetic layer showing a rightward mag
Hasegawa Naoya
Ide Yosuke
Saito Masamichi
Alps Electronics Co., Ltd.
Brinks Hofer Gilson & Lione
Poker Jennifer A.
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