Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-08-23
2003-03-25
Heinz, A. J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06538860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistive element used for a magnetic head and the like, and more particularly, the invention relates to a magnetoresistive element utilizing a spin-valve effect and to a method of making the same.
2. Description of the Related Art
Magnetoresistive elements are increasingly used for magnetic heads in magnetic disk units and the like because of their high magnetic field sensitivity.
FIG. 8
is a sectional view of a magnetic core of a magnetic head using a conventional magnetoresistive element, viewed from the surface facing a magnetic disk. A magnetic core
31
, which includes a read head
32
and a write head
33
, is provided on the trailing end of a slider
34
. The magnetic core
31
and the slider
34
constitute a magnetic head
35
.
In the read head
32
, an underlying layer
36
, a lower shielding layer
37
, a lower gap layer
38
, an underlying layer
39
, an antiferromagnetic layer
40
, a first ferromagnetic layer
41
, a nonmagnetic conductive layer
42
, and a second ferromagnetic layer
43
are deposited in that order on the trailing end of the slider
34
, and a pair of bias layers
44
are placed on both sides of the second ferromagnetic layer
43
with a distance corresponding to a track width T of the magnetic disk therebetween. An electrode layer
45
is formed on each bias layer
44
, and an upper gap layer
46
is deposited so as to cover the electrode layers
45
and the second ferromagnetic layer
43
located therebetween. An upper shielding layer
47
which also acts as a lower core layer of the write head
33
is deposited on the upper gap layer
46
.
In the write head
33
, a gap layer
48
is formed on the lower core layer
47
, and an upper core layer
49
is formed thereon.
The antiferromagnetic layer
40
, the first ferromagnetic layer
41
, the nonmagnetic conductive layer
42
, the second ferromagnetic layer
43
, the pair of bias layers
44
, and the pair of electrode layers
45
constitute a magnetoresistive element
50
.
The first ferromagnetic layer
41
is composed of, for example, a Co film, an NiFe alloy, a CoNiFe alloy, a CoFe alloy, or a CoNi alloy. The antiferromagnetic layer
40
is composed of a PtMn alloy or the like. The bias layers
44
are composed of a conductive antiferromagnetic material, such as an IrMn alloy or an FeMn alloy.
The first ferromagnetic layer
41
shown in
FIG. 8
is magnetized by an exchange anisotropic magnetic field due to exchange coupling occurring at the interface with the antiferromagnetic layer
40
, and the antiferromagnetic layer
40
and the first ferromagnetic layer
41
are magnetically coupled to each other. The magnetization direction of the first ferromagnetic layer
41
is fixed in the Y direction in the drawing, i.e., in the direction crossing to the magnetic disk (in the height direction) by the coupling.
The second ferromagnetic layer
43
is magnetized by an exchange anisotropic magnetic field of the pair of bias layers
44
, is magnetically coupled to the pair of bias layers
44
in regions in which the second ferromagnetic layer
43
is in direct contact with the pair of bias layers
44
, and is aligned in a single-domain state as a whole. The magnetization direction of the second ferromagnetic layer
43
is aligned in the direction opposite to the X
1
direction in the drawing, i.e., in the direction crossing to the magnetization direction of the first ferromagnetic layer
41
. Due to the single-domain state, in the regions in which the second ferromagnetic film
43
and the pair of bias layers
44
are in direct contact with each other, the magnetization direction of the second ferromagnetic layer
43
is fixed in the direction opposite to the X
1
direction in the drawing, and domain walls are inhibited from appearing in the second ferromagnetic layer
43
, and thus Barkhausen noise is prevented from occurring.
In the magnetoresistive element
50
, a sensing current (steady-state current) is applied from the electrode layer
45
to the second ferromagnetic layer
43
, the nonmagnetic conductive layer
42
, and the first ferromagnetic layer
41
, and when a fringing magnetic field from a magnetic disk which rotates and travels in the Z direction is applied in the Y direction in the drawing, the magnetization direction of a portion of the second ferromagnetic layer
43
which is not in direct contact with the pair of bias layers
44
changes from the direction opposite to the X
1
direction in the drawing to the Y direction. Because of the relationship between the change in the magnetization direction in the second ferromagnetic layer
43
and the magnetization direction of the first ferromagnetic layer
41
, the electrical resistance changes, and the fringing magnetic field from the magnetic disk is detected by a voltage change based on the change in the electrical resistance.
In order to fabricate the magnetoresistive element
50
shown in
FIG. 8
, as shown in
FIG. 9
, the individual layers from the antiferromagnetic layer
40
to the second ferromagnetic layer
43
are formed in a vacuum, and by performing heat treatment (annealing) in a magnetic field, an exchange anisotropic magnetic field is produced at the interface between the first ferromagnetic layer
41
and the antiferromagnetic layer
40
, and the magnetization direction of the first ferromagnetic layer
41
is fixed in the Y direction in the drawing. The above structure is then taken out into air, and a lift-off resist layer
51
having a width substantially corresponding to the track width T is formed as shown in FIG.
10
. Next, as shown in
FIG. 11
, the bias layer
44
and the electrode layer
45
are formed on the surface of the second ferromagnetic layer
43
including the lift-off resist layer
51
, and then the lift-off resist layer
51
is removed, and by aligning the magnetization direction of the second ferromagnetic layer
43
in the track width direction, the magnetoresistive element
50
shown in
FIG. 8
is obtained.
However, in the conventional magnetoresistive element
50
described above, in order to form the lift-off resist layer
51
shown in
FIG. 10
, after the individual layers from the antiferromagnetic layer
40
to the second ferromagnetic layer
43
are formed in a vacuum and the magnetization direction of the first ferromagnetic layer
41
is fixed in the Y direction by performing heat treatment in a magnetic field, the structure must be taken out into air. Consequently, the surface of the second ferromagnetic layer
43
is brought into contact with air, and foreign matter, such as dust in air and contamination, adheres to the surface. As a result, it is not possible to sufficiently bring the second ferromagnetic layer
43
and the pair of-bias layers
44
into close contact with each other, and magnetic coupling between the second ferromagnetic layer
43
and the pair of bias layers
44
becomes insufficient, resulting in the occurrence of domain walls. Thereby, it is not possible to avoid Barkhausen noise which is caused by irregular movement of domain walls.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a magnetoresistive element and a method of making the same in which a second ferromagnetic layer and a bias layer can be magnetically coupled to each other satisfactorily, and Barkhausen noise can be prevented from occurring.
In accordance with one aspect of the present invention, a magnetoresistive element includes a nonmagnetic conductive layer, first and second ferromagnetic layers which are conductive and which sandwich the nonmagnetic conductive layer, an antiferromagnetic layer magnetically coupled to the first ferromagnetic layer for fixing the magnetization direction of the first ferromagnetic layer, a bias layer magnetically coupled to the second ferromagnetic layer for aligning the magnetization direction of the second ferromagnetic layer in a direction crossing to the magnetization direction of the first ferromagnetic layer, and a pair of ele
Kakihara Yoshihiko
Sato Kiyoshi
Alps Elctric Co., Ltd.
Brinks Hofer Gilson & Lione
Heinz A. J.
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