Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-08-21
2003-07-01
Ometz, David L. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06587316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spin-valve type thin film magnetic element whose electric resistance changes in accordance to the relation between a fixed direction of magnetization of a fixed magnetic layer (pinned magnetic layer) and a direction of magnetization of a free magnetic layer being that are affected by an external magnetic field, and a thin film magnetic head comprising the spin-valve type thin film magnetic element. Particularly, the present invention relates to a technology suitable for use in a spin-valve type thin film magnetic element having an electrode layer comprising an overlay part extending on the surface of a laminated body from each side to the center of the laminated body.
2. Description of the Related Art
The spin-valve type thin film magnetic element is a kind of GMR (Giant Magnetic Electroresistive) element that senses recording magnetic fields from a recording medium such as a hard disk.
The spin-valve type thin film magnetic element has some excellent features such that it has a relatively simple structure among the GMR elements and a high rate of change of magnetoresistance against external magnetic fields, and the electrical resistance can be altered by a relatively weak magnetic field.
FIG. 24
shows a cross-sectional structure of one example of a conventional spin-valve type thin film magnetic element viewed from the face (ABS) side opposed to a recording medium.
The spin-valve type thin film magnetic element shown in
FIG. 24
is a so-called bottom-type single spin-valve type thin film element in which one layer each of an antiferromagnetic layer, a pinned magnetic layer, a non-magnetic conductive layer and a free magnetic layer are laminated.
The travel direction of the magnetic recording medium such as the hard disk is in the Z-direction, and the direction of leak magnetic field from the magnetic recording medium is in the Y-direction in this spin-valve type thin film magnetic element.
The conventional spin-valve type thin film magnetic element shown in
FIG. 24
comprises a laminated body
109
, a pair of hard bias layers
105
formed at both sides of the laminated body
109
, and a pair of electrode layers
108
formed on the hard bias layers
105
, wherein the laminated body
109
comprises, from the bottom to the top on a substrate, an underlayer
106
, an antiferromagnetic layer
101
, a pinned magnetic layer
102
, a non-magnetic conductive layer
103
, a free magnetic layer
104
and a protective layer
107
. The electrode layer
108
comprises an overlay part
108
a
extending over the surface of the laminated body
109
from each side toward the center of the laminated body.
The underlayer
106
comprises Ta (tantalum), and the antiferromagnetic layer
101
is made of an alloy such as a NiCo alloy, a FeMn alloy and a NiMn alloy. The pinned magnetic layer
102
and free magnetic layer
104
is made of Co or a NiFe alloy, Cu is used for the non-magnetic conductive layer
103
, the hard bias layer
105
is made of a Co—Pt (cobalt-platinum) alloy, and the electrode layer
108
is made of Cu.
An exchange coupling magnetic field (a coupling anisotropic magnetic field) is generated at the interface between the pinned magnetic layer
102
and antiferromagnetic layer
101
, by forming the pinned magnetic layer
102
in contact with the antiferromagnetic layer
101
. The direction of magnetization of the pinned magnetic layer
102
is fixed, for example, in the Y-direction.
The direction of variable magnetization of the free magnetic layer
104
is aligned in the X
1
-direction by magnetizing the hard bias layer
105
in the X
1
-direction. As a result, the direction of variable magnetization of the free magnetic layer
104
is made to be approximately perpendicular to the direction of magnetization of the pinned magnetic layer
102
.
In this spin-valve type thin film magnetic element, a sense current flows from the electrode layer
108
formed on the hard bias layer
105
through the pinned magnetic layer
102
, non-magnetic conductive layer
103
and free magnetic layer
104
. The travel direction of the magnetic recording medium such as the hard disk is in the Z-direction, and the direction of magnetization of the free magnetic layer
104
changes from the X
1
-direction to the T-direction when a leak magnetic field from the magnetic recording medium is applied in the Y-direction. Electrical resistance changes in relation to directional changes of magnetization in the free magnetic layer
104
and in the pinned magnetic layer
102
(referred as magnetoresistive effect MR), and the leak magnetic field from the magnetic recording medium is sensed by utilizing the voltage changes based on this electrical resistance change.
As shown in
FIG. 24
, each electrode layer
108
has an overlay part
108
a
extending on the laminated body
109
in this spin-valve type thin film magnetic element. Accordingly, almost all the part of a sense current J flows into the laminated body
109
from the tip of the overlay part
108
a
of the electrode layer
108
, when a sense current as a detection current is allowed to flow into the pinned magnetic layer
102
, non-magnetic conductive layer
103
and free magnetic layer
104
from the electrode layer
108
.
Consequently, a center part
104
a,
through which almost all the sense current J flows, and side parts (electrode overlay parts)
104
, through which few sense current flows, are formed in the free magnetic layer
104
.
The central part of the laminated body
109
located between the overlay parts
108
a
of each electrode layer
108
substantially contributes to regeneration of the recording magnetic field from the magnetic recording medium in this spin-valve type thin film magnetic element, and serves as a sensitive zone manifesting a magnetoresistive effect. Each side part of the laminated body
109
located at under each overlay part
108
a
serves as a dead zone that does not substantially contribute to regeneration of the recording magnetic field from the magnetic recording medium.
The sensitive zone and dead zone are thus provided by forming an overlay parts
108
a
of each electrode layer
108
. The width of this sensitive zone corresponds to a track width Tw of the spin-valve type thin film magnetoresistive element. Consequently, the track width Tw can be narrowed by providing the overlay part
108
a
in each electrode layer
108
, thereby enabling to comply with narrow track width for high density recording.
However, when the electrode layer
108
is thin and has high resistivity, or when the junction part between each electrode layer
108
and laminated body
109
has a large junction resistance, for example, the sense current J flowing from the overlay part
108
a
encounters large resistance, and the magnitude of a shunt current J′ of the sense current J flowing in through the hard bias layer
105
turns out to be substantially large.
As a result, the sense current J flows through the region represented by symbols D in
FIG. 24
that are located under each overlay part
108
a
of the laminated body
109
. When the sense current J flows through the regions D that should be naturally the dead zones, voltage changes based on magnetoresistance changes against the external magnetic field appear in the region D, and signals in the recording track of the magnetoresistive recording medium corresponding to the region D is regenerated due to expressed voltage changes in the region D based on the magnetoresistance change against the external magnetic field.
In the case of the narrowing the tack width for attaining high density recording on the magnetic recording medium, in particular, a side-reading phenomenon occurs whereby a line of information on the adjoining magnetic recording track is read in the region D in place of another line of information on the magnetic recording track that should be naturally read in the sensitive zone. This side-reading phenomenon arises noises to the output signal, and may serve as error sources.
In addit
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Ometz David L.
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