Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-01-25
2004-03-02
Nguyen, Hoa T. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S324110
Reexamination Certificate
active
06700750
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spin-valve thin-film magnetic element including a free magnetic layer and laminates of pinned magnetic layers and antiferromagnetic layers formed on two surfaces of the free magnetic layer, and to a method for making the spin-valve thin-film magnetic element.
2. Description of the Related Art
Magnetoresistive magnetic heads are classified into anisotropic magnetoresistive (AMR) heads provided with elements having anisotropic magnetoresistive effects and giant magnetoresistive (GMR) heads provided with elements having giant magnetoresistive effects. An AMR head has a single layer structure of a magnetic element exhibiting a magnetoresistive effect. In contrast, a GMR head is provided with a multi-layered element composed of a plurality of layers exhibiting an anisotropic magnetoresistive effect. Several structures have been proposed to produce giant magnetoresistive effects. A spin-valve thin-film magnetic element has a simple structure and a high rate of change of resistance to a weak external magnetic field. Spin-valve thin-film magnetic elements are classified into single spin-valve thin-film magnetic elements and dual spin-valve thin-film magnetic elements.
FIGS. 12 and 13
are schematic cross-sectional views of a conventional spin-valve thin-film element.
Shielding layers are formed above and below the spin-valve thin-film element with gap layers therebetween, and a GMR head for reading is composed of the spin-valve thin-film element, the gap layers, and the shielding layers. An inductive head for recording may be deposited on the GMR head for reading.
The GMR head and the inductive head are provided at a trailing end of a floating slider and constitute a thin-film magnetic head. The GMR head detects recorded magnetic fields on magnetic recording media, such as hard disks. In
FIGS. 12 and 13
, a magnetic recording medium moves in the Z direction and a fringing magnetic field is generated in the Y direction from the recording magnetic medium.
The spin-valve thin-film magnetic element
3
shown in
FIG. 12
is a so-called dual spin-valve thin-film magnetic element in which a nonmagnetic conductive layer, a pinned magnetic layer, and an antiferromagnetic layer are deposited on each of two surfaces of a free magnetic layer.
The dual spin-valve thin-film magnetic element includes two groups of triple-layer configurations, each including a free magnetic layer, a nonmagnetic conductive layer, and a pinned magnetic layer. Thus, this element has a large rate of change of resistance compared to a single spin-valve thin-film magnetic element having a single group of the triple-layer configuration including the free magnetic layer, the nonmagnetic conductive layer, and the pinned magnetic layer, and can be used in high-density recording.
In the spin-valve thin-film magnetic element
3
shown in
FIGS. 12 and 13
, an underlying layer
10
, a second antiferromagnetic layer
11
, a second pinned magnetic layer
12
, a nonmagnetic conductive layer
13
, a free magnetic layer
14
composed of Co films
15
and
17
and a NiFe alloy film
16
, a nonmagnetic conductive layer
18
, a first pinned magnetic layer
19
, a first antiferromagnetic layer
20
, and a protective layer
21
are deposited in that order from the bottom of the drawings.
As shown in
FIG. 13
, biasing layers
130
and conductive layers
131
are formed on two sides of the laminate over the underlying layer
10
to the protective layer
21
.
The first and second pinned magnetic layers
19
and
12
, respectively, are formed of, for example, a Co film, a NiFe alloy, a CoNiFe alloy, or a CoFe alloy.
The first and second antiferromagnetic layers
20
and
11
, respectively, are formed of a PtMn alloy, an XMn alloy wherein X is at least one metal selected from Pd, Ir, Rh, Ru and Os, or a PtMnZ alloy wherein Z is at least one element selected from Pd, Ir, Rh, Ru, Os, Au, Ag, Cr, Ni, Ne, Ar, Xe and Kr.
The first pinned magnetic layer
19
and the second pinned magnetic layer
12
in
FIG. 12
are magnetized at interfaces with the first and second antiferromagnetic layers
20
and
11
, respectively, by exchange anisotropic magnetic fields by exchange coupling (unidirectional exchange coupling magnetic fields), and the magnetization vectors are fixed in the Y direction in the drawing, that is, a direction (height direction) away from the recording medium.
The free magnetic layer
14
is aligned in a single-domain state by a magnetic flux from the biasing layers
130
, and the magnetization is aligned in the X direction in the drawing, which is perpendicular to the magnetization vector of the first and second pinned magnetic layers
19
and
12
, respectively.
Since the free magnetic layer
14
is aligned to a single-domain state by the biasing layers
130
, the generation of Barkhausen noise is avoidable.
In the spin-valve thin-film magnetic element
3
, when stationary currents flow from one conductive layer
131
to the free magnetic layer
14
, the nonmagnetic conductive layers
18
and
13
, respectively, and the first and second pinned magnetic layers
19
and
12
, and when a fringing magnetic field is applied in the Y direction from the magnetic recording medium, which moves in the Z direction, the magnetization of the free magnetic layer
14
changes from the X direction to the Y direction. Such a change in magnetization vector in the free magnetic layer
14
causes a change in electrical resistance of the element in relation to the magnetization vector of the first and second pinned magnetic layers
19
and
12
, respectively. The fringing magnetic field from the magnetic recording medium is detected as a change in voltage based on the change in electrical resistance.
In the production of this spin-valve thin-film magnetic element
3
, individual layers from the underlying layer
10
to the protective layer
21
are deposited in that order, and are annealed in a magnetic field to generate exchange anisotropic fields at an interface between the first pinned magnetic layer
19
and the first antiferromagnetic layer
20
and at an interface between the second pinned magnetic layer
12
and the second antiferromagnetic layer
11
so that the first and second pinned magnetic layers
19
and
12
, respectively, have the same magnetization vector (Y direction in the drawing).
In the conventional spin-valve thin-film magnetic element
3
, as shown in
FIG. 14
, it is preferable that the magnetization vector (H
3
) of the free magnetic layer
14
be perpendicular to the magnetization vectors (H
1
and H
2
) of the first and second pinned magnetic layers
19
and
12
, respectively, when an external magnetic field is not applied from the recording medium. However, dipolar magnetic fields (H
4
and H
5
) leaking from the first and second pinned magnetic layers
19
and
12
, respectively, enter the free magnetic layer
14
from the opposite direction to the Y direction. These dipolar magnetic fields (H
4
and H
5
) tilt the magnetization vector (H
3
) toward the vector (H
6
) opposite to the Y direction, and thus preclude biasing adjustment for orienting the magnetization vector of the free magnetic layer
14
. As a result, the magnetization vector (H
6
) of the free magnetic layer
14
cannot be perpendicular to the magnetization vectors (H
1
and H
2
) of the first and second pinned magnetic layers
19
and
12
, respectively, and the regenerated waveform is inevitably asymmetric.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a spin-valve thin-film magnetic element which has no tilt of the magnetization vector of a free magnetic layer and can suppress asymmetry of the regenerated waveform.
It is another object of the present invention to provide a thin-film magnetic head having the spin-valve thin-film magnetic element.
It is a still another object of the present invention to provide a method for making the spin-valve thin-film magnetic element.
In a first aspect of the present invention, a spin-valve thin-fil
Alps Electric Co. ,Ltd.
Nguyen Hoa T.
Watko Julie Anne
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