Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-11-29
2003-12-16
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S632000, C428S650000, C360S324120, C360S327240
Reexamination Certificate
active
06663987
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spin-valve thin film element in which an electric resistance varies with, for example, the magnetization vector in a pinned magnetic layer and the a magnetization vector in a free magnetic layer affected by an external magnetic field. Specifically, the present invention relates to a magnetoresistive element which allows a sensing current to effectively flow into a multilayer film, as well as a process for manufacturing the electromagnetic element.
2. Description of the Related Art
FIG. 14
is a sectional view of the structure of a conventional magnetoresistive element taken from an air bearing surface (ABS).
The magnetoresistive element shown in
FIG. 14
is a spin-valve thin film element and detects a recording magnetic field from a recording medium such as a hard disk. The spin-valve thin film element is a type of giant magnetoresistive element utilizing a giant magnetoresistive effect. This type of element.
The spin-valve thin film element includes a multilayer film
9
comprising an underlayer
6
, an antiferromagnetic layer
1
, a pinned magnetic layer
2
, a nonmagnetic layer
3
, a free magnetic layer
4
, and a protective layer
7
layered in this order from the bottom, and a pair of hard bias layers
5
and
5
formed on both sides of the multilayer film
9
, and a pair of electrode layers
8
and
8
formed on the hard bias layers
5
and
5
. The underlayer
6
and the protective layer
7
are each made of, for example, a Ta (tantalum) film. The width of a top surface of the multilayer film
9
defines a track width Tw.
Generally, the antiferromagnetic layer
1
is made of an Fe—Mn (iron-manganese) alloy film or a Ni—Mn (nickel-manganese) alloy film, the pinned magnetic layer
2
and the free magnetic layer
4
are each made of a Ni—Fe (nickel-iron) alloy film, the nonmagnetic layer
3
is made of a Cu (copper) film, the hard bias layers
5
and
5
is made of a Co—Pt (cobalt-platinum) alloy film, and the electrode layers
8
and
8
are each made of a Cr (chromium) film.
As shown in
FIG. 14
, the magnetization vector in the pinned magnetic layer
2
is put into a single magnetic domain state in the Y direction (direction of a leakage magnetic field from a recording medium; height direction) through an exchange anisotropic magnetic field with the antiferromagnetic layer
1
. In contrast, the magnetization vector in the free magnetic layer
4
is aligned in the X direction by the effect of a bias magnetic field from the hard bias layers
5
and
5
.
Specifically, the magnetization vector in the pinned magnetic layer
2
is set so as to be orthogonal to the magnetization vector in the free magnetic layer
4
.
In the spin-valve thin film element, the electrode layers
8
and
8
formed on the hard bias layers
5
and
5
supply a sensing current to the pinned magnetic layer
2
, the nonmagnetic layer
3
and the free magnetic layer
4
. The magnetic recording medium, such as a hard disk, moves in the Z direction. When a leakage magnetic field from the magnetic recording medium is applied to the free magnetic layer
4
in the Y direction, the magnetization vector in the free magnetic layer
4
varies from the X direction to the Y direction. The electrical resistance depends on the variation in the magnetization vector in the free magnetic layer
4
and the magnetization vector in the pinned magnetic layer
2
(this is called as “magnetoresistive effect”), hence the leakage magnetic field from the magnetic recording medium is detected by the variation in the voltage due to the variation in the electrical resistance.
However, the conventional magnetoresistive element shown in
FIG. 14
has the following problems.
The electrode layers
8
and
8
of the magnetoresistive element shown in
FIG. 14
have a decreasing thickness as they approach to front end faces
8
a
and
8
a
which are in contact with the multilayer film
9
. A sensing current at a constant level cannot be always significantly allowed to flow even to the front end faces
8
a
and
8
a
of the electrode layers
8
and
8
, and the sensing current is shunted on the way, part of which flows into the hard bias layers
5
and
5
, to thereby reduce a read output.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a magnetoresistive element free from the above problems, in which electrode layers have some thickness even in regions where the electrode layers are in contact with a multilayer film and thereby can allow a sensing current to flow into a multilayer film of the magnetoresistive element always at a constant level to improve the reproducing characteristics, as well as to provide a process for manufacturing the magnetoresistive element.
Specifically, the present invention provides, in an aspect, a magnetoresistive element which includes a multilayer film including an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer, the magnetization vector in the pinned magnetic layer is fixed by an exchange anisotropic magnetic field with the antiferromagnetic layer, and a free magnetic layer formed on the pinned magnetic layer through the interposition of a nonmagnetic layer; a pair of bias layers formed on both sides of the multilayer film and aligning the magnetization vector in the free magnetic layer to a direction crossing the magnetization vector of the pinned magnetic layer; and a pair of electrode layers formed on the bias layers and supplying a sensing current to the pinned magnetic layer, the nonmagnetic layer and the free magnetic layer. In this element, an insulating layer is formed on the multilayer film between the electrode layers, and the electrode layers formed on both sides of the multilayer film are in contact with the sides of the insulating layer directly or through the interposition of another layer.
According to the present invention, front end faces of the electrode layers on the multilayer film side are laminated so as to be along the sides of the insulating layer, and the electrode layers have a large thickness even in regions where the electrode layers are in contact with the multilayer film, owing to the thickness of the insulating layer. Accordingly, a sensing current can be allowed to flow in the multilayer film of the magnetoresistive element always at a constant level to thereby improve the reproducing characteristics.
Preferably, the multilayer film includes a lamination of the antiferromagnetic layer, the pinned magnetic layer, the nonmagnetic layer, and the free magnetic layer in this order from the bottom, and the antiferromagnetic layer extends toward the portions on both sides of each of the layers formed on the antiferromagnetic layer, and a pair of the bias layers and a pair of the electrode layers are laminated on the antiferromagnetic layer in the portions on both sides through the interposition of a metallic film.
The present invention provides, in another aspect, a magnetoresistive element which includes a multilayer film including a free magnetic layer, nonmagnetic layers formed on and under the free magnetic layer, pinned magnetic layers formed on one nonmagnetic layer and under the other nonmagnetic layer where magnetization vectors in the pinned magnetic layers are fixed, and antiferromagnetic layers formed on one pinned magnetic layer and under the other pinned magnetic layer; a pair of bias layers formed on both sides of the multilayer film and aligning the magnetization vector in the free magnetic layer in a direction crossing the magnetization vectors in the pinned magnetic layers; a pair of electrode layers formed on the bias layers and supplying a sensing current to the pinned magnetic layers, the nonmagnetic layers, and the free magnetic layer. In the magnetoresistive element, an insulating layer is formed on the multilayer film between the electrode layers, and the electrode layers formed on both sides of the multilayer film are in contact with sides of the insulating layer directly or t
Alps Electric Co. ,Ltd.
Brinls Hofer Gilson & Lione
Falasco Louis
Resan Stevan A.
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