Magnetoresistance device and production method thereof

Details Magnetoresistance device and production method thereof Magnetoresistance device and production method thereof

2000-06-13

2001-12-04

Kiliman, Leszek (Department: 1773)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S654000, C428S654000, C428S654000, C428S634000, C428S900000, C360S112000, C360S125020, C360S125330, C338S03200R, C324S252000

Reexamination Certificate

active

06326092

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Related Art
The present invention relates to a magnetoresistance device for use in a magnetic head, a position sensor, rotation sensor or the like, and also to a method of producing such a magnetoresistance device. The present invention also relates to a magnetic head provided with such a magnetoresistance device.
2. Description of the Related Art
Magnetoresistance reading heads (MR heads) are known in the art. They include an AMR (anisotropic magnetoresistance) head utilizing the anisotropic magnetoresistance effect, and a GMR (giant magnetoresistance) head utilizing spin-dependent scattering of conduction electrons. An example of a GMR head is a spin-valve head disclosed in U.S. Pat. No. 5,159,513. This spin-valve head shows a high magnetoresistance effect in response to a low external magnetic field.
FIGS. 17 and 18
are simplified schematic diagrams illustrating the structure of an AMR head.
In the AMR head shown in
FIG. 17
, an electrically insulating layer
2
and a ferromagnetic layer (AMR material layer)
3
are successively formed on a soft magnetic layer
1
, and antiferromagnetic layers
4
are formed on either end of the ferromagnetic layer
3
in such a manner that the antiferromagnetic layers
4
are spaced by an amount corresponding to the track width. Furthermore, an electrically conductive layer
5
is formed on each antiferromagnetic layer
4
. On the other hand, the AMR head shown in
FIG. 18
comprises: a multilayer structure including a soft magnetic layer
1
, an electrically insulating layer
1
, and a ferromagnetic layer
3
; magnet layers
6
formed at either side of the multilayer structure in such a manner that the multilayer structure is located between the two magnet layers
6
; and an electrically conductive layer
5
formed on each magnet layer
6
.
To operate AMR heads of the types described above under optimum conditions, it is required to apply two magnetic bias fields to the ferromagnetic layer
3
having the AMR property.
A first magnetic bias field serves to make the ferromagnetic layer
3
change linearly in resistance in response to a magnetic flux from a magnetic medium. The first magnetic bias field is applied in a direction at a right angle with respect to the surface of the magnetic medium (in the Z direction in
FIG. 17
) and parallel to the film plane of the ferromagnetic layer
3
. The first bias magnetic field is generally called a transverse bias field, and is produced by passing a detection current from the electrically conductive layer
5
into the AMR head.
The second magnetic bias field is generally called a longitudinal bias field, and is applied in a direction parallel to both the film plane of the magnetic medium and the ferromagnetic layer
3
(in the X direction in FIG.
17
). The longitudinal bias field serves to suppress Barkhausen noise due to formation of a large number of magnetic domains in the ferromagnetic layer
3
, thereby obtaining a smooth and low-noise resistance change in response to the magnetic flux from the magnetic medium.
To suppress the Barkhausen noise, it is required to make the ferromagnetic layer
3
into the form of a single domain. To this end, there are two known methods of applying a longitudinal bias field. In a first method, the magnetic head structure shown in
FIG. 18
is employed, and leakage of magnetic flux from the magnet layers
6
disposed at either side of the ferromagnetic layer
3
is used. In the second method, the magnetic head structure shown in
FIG. 17
is employed, and an exchange anisotropic magnetic field produced at the interfacial boundary between the antiferromagnetic layer
4
and the ferromagnetic layer
3
is used.
A specific example of a magnetoresistance device utilizing the exchange anisotropic coupling of the antiferromagnetic layer is the exchange bias type device shown in FIG.
19
. Another example is shown in
FIG. 20
, which is knows as the spin-valve type device.
The magnetic head shown in
FIG. 19
has a structure similar to that shown in
FIG. 17
, and comprises a lower insulating layer
21
, a ferromagnetic layer
22
, a non-magnetic layer
23
, and a ferromagnetic layer
24
having the magnetoresistance property wherein these layers are formed into a multilayer structure. Furthermore, antiferromagnetic layers
25
and a lead layer
26
are formed in such a manner that they are spaced by an amount corresponding to the track width TW.
In the structure shown in
FIG. 19
, as a result of the exchange anisotropic coupling at the interfacial boundary between the ferromagnetic layer
24
and the antiferromagnetic layer
25
, a longitudinal bias field is applied to the ferromagnetic layer
24
thereby converting a region B shown in
FIG. 19
(where the ferromagnetic layer
24
and the antiferromagnetic layer
25
are in contact with each other) into a single domain directed in the X direction. This induces the ferromagnetic layer
24
in a region A with a width corresponding to the track width to be converted into a single domain in the X direction. A steady-state current is passed from the lead layer
26
into the ferromagnetic layer
24
via the antimagnetic layer
25
. When the steady-state current is passed through the ferromagnetic layer
24
, a longitudinal bias field in the Z direction caused by magnetostatic coupling energy from the ferromagnetic layer
22
is applied to the ferromagnetic layer
24
. If a magnetic leakage field from the magnetic medium is applied to the ferromagnetic layer
24
magnetized by the transverse and longitudinal magnetic bias fields, the electric resistance against the steady-state current varies linearly in proportion to the magnitude of the magnetic leakage field. Therefore, it is possible to detect the magnetic leakage field by detecting the change in the electric resistance.
In the structure shown in
FIG. 20
, a free ferromagnetic layer
28
, a non-magnetic and electrically conductive layer
29
, and a ferromagnetic layer
24
are successively formed on a lower insulating layer
21
wherein the free ferromagnetic layer
28
, the non-magnetic and electrically conductive layer
29
, and the ferromagnetic layer
24
make up a magnetoresistance element. Furthermore, an antiferromagnetic layer
25
and an upper insulating layer
27
are successively formed on the ferromagnetic layer
24
.
In the structure shown in
FIG. 20
, a steady-state current in passed through the magnetoresistance element
19
. The magnetization of the ferromagnetic layer
24
is fixed into the Z direction due to the exchange anisotropic coupling with the antiferromagnetic layer
25
. If a magnetic leakage field from the magnetic medium moving in the Y direction is applied, the magnetization direction of the free ferromagnetic layer
28
varies, and thus the electric resistance of the magnetoresistance element
19
varies. Therefore, it is possible to detect the magnetic leakage field from the magnetic medium by detecting the change in the electric resistance.
The exchange anisotropic magnetic field generally arises from the exchange interaction of magnetic moments at the interfacial boundary between a ferromagnetic layer and an antiferromagnetic layer. FeMn is well known as an antiferromagnetic material which interacts with a ferromagnetic layer such as a NiFe layer and creates an exchange anisotropic magnetic field. However, FeMn is so poor in corrosion resistance that great degradation in the exchange anisotropic magnetic field occurs due to corrosion which occurs during a production process of a magnetic head and also during the operation of the magnetic head. In some cases, the corrosion damages a magnetic medium. It is known that the temperature in the vicinity of the FeMn layer easily rises to about 120° C. during the operation of the magnetic head due to heat generated by the steady-state detection current. The exchange anisotropic magnetic field produced by the FeMn layer is very sensitive to the change in temperature. That is, the exchange anisotropic magnetic field decreases substantially linearly

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