Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-10-01
2001-06-19
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06249407
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a magnetoresistive device having a magnetoresistive element (MR element) and, more particularly, to a thin-film magnetoresistive device having an MR element through which a current flows in a direction perpendicular to a plane of the MR element.
2. Description of the Related Art
FIG. 1
is an illustration of a conventional magnetic reproducing head formed as a thin-film device having an MR element, viewed from a side of a magnetic recording medium from which information is read by the magnetic reproducing head. In
FIG. 1
, a side-to-side direction corresponds to the direction of width of a track formed on the magnetic recording medium.
The magnetic reproducing head shown in
FIG. 1
comprises an MR element
100
, an upper shielding layer
101
, a lower shielding layer
102
, an upper gap layer
103
and a lower gap layer
104
. The MR element
100
is interposed between the lower gap layer
104
and the upper gap layer
103
. The upper shielding layer
101
is formed on a surface of the upper gap layer
103
which surface is opposite to the MR element
100
, and the lower shielding layer
102
is formed on a surface of the lower gap layer
104
which surface is opposite to the MR element
100
. Each of the upper shielding layer
101
and the lower shielding layers
102
is formed from a soft magnetic material such as NiFe. Each of the upper gap layer
103
and the lower gap layer
104
is formed from an insulating material such as alumina (aluminum oxide).
Additionally, lead wires
105
A and
105
B are provided on the left side and the right side of the MR element
100
, respectively, so as to electrically detect a change in a magnetoresistance of the MR element
100
. Further, hard magnet layers
106
A and
106
B are formed between the lower gap layer
104
and each of the lead wires
105
A and
105
B, respectively. Each of the hard magnet layers
106
A and
106
B is formed from a material such as CoPt which has hard magnetic properties so as to eliminate a Balkhausen noise.
In the above-mentioned magnetic reproducing head, a change in the magnetoresistance of the MR element
100
can be sensed as a change in a voltage across the MR element
100
by providing a current flowing between the lead wires
105
A and
105
B connected to the MR element
100
. Accordingly, when the magnetic reproducing head (magnetoresistive device) is positioned close to a magnetic recording medium such as a hard disk, a change occurs in the magnetoresistance of the MR element
100
in the magnetoresistive device due to a change in an electric field generated by the magnetic recording medium. Thus, such a change in the magnetoresistance can be sensed as a change in the voltage across the MR element
100
.
It should be noted that the magnetic reproducing head shown in
FIG. 1
is referred to as a current-in-plane (CIP) type thin-film magnetic head since a current flows from the lead wire
105
A to the lead wire
105
B along a plane of the MR element
100
.
Japanese Laid-Open Patent Application No.9-288807 discloses another thin-film magnetic head as shown in FIG.
2
. This thin-film magnetic head has a structure different from that of the thin-film head shown in
FIG. 1
, and is referred to as a current perpendicular (CPP) type thin-film magnetic head in which a current flows in a direction perpendicular to a plane of the MR element. That is, a current flows in a longitudinal direction in FIG.
2
.
The thin-film magnetic head shown in
FIG. 2
comprises an MR element
110
, an upper shielding layer
111
, a lower shielding layer
112
, an upper gap layer
113
and a lower gap layer
114
. The MR element
110
is interposed between the lower gap layer
114
and the upper gap layer
113
. The upper shielding layer
111
is formed on a surface of the upper gap layer
113
which surface is opposite to the MR element
110
, and the lower shielding layer
112
is formed on a surface of the lower gap layer
114
which surface is opposite to the MR element
110
. Each of the upper shielding layer
111
and the lower shielding layers
112
is formed of a metallic, magnetic material having good conductivity. Each of the upper gap layer
113
and the lower gap layer
114
is formed from a conductive material such as Cu. Additionally, insulating layers
117
A and
117
B are provided on the left side and right side of the MR element
110
, respectively, so as to fill a gap between the lower shielding layer
112
and the upper shielding layer
111
. Each of the insulating layers
117
A and
117
B is formed from an insulating material such as alumina.
In the thin-film magnetic head shown in
FIG. 2
, a current flows from the upper shielding layer
111
to the upper gap layer
113
, traverses the MR element
110
and finally reaches the lower shielding layer
112
via the lower gap layer
114
.
In recent years, density of data recorded on a recording medium is greatly increased. In order to read the high-density data on the recording medium, a gap of the device must be reduced. Accordingly, in the conventional magnetic reproducing head shown in
FIG. 1
, a thickness of each of the upper and lower gap layers
103
and
104
has been reduced. However, in order to maintain sufficient insulation, the thickness of each of the upper and lower gap layers
103
and
104
must be maintained to be about 30 nm, and it is difficult to further reduce the gap.
The thin-film magnetic head shown in
FIG. 1
is the CIP type in which a current flows along a plane of the MR element. Recently, a giant magnetoresistive (GMR) element has been developed. It is found that the sensitivity of the GMR element of a spin valve type can be increased by providing a current to flow in a direction perpendicular to the plane of the GMR element. However, such an attempt cannot be made to the thin-film magnetic head shown in
FIG. 1
since the thin-film magnetic head shown in
FIG. 1
is of the CIP type. Additionally, a tunnel type GMR element requires a current flowing in a direction perpendicular to a plane of the GMR element, and, thus, the tunnel type GMR element cannot be used in the thin-film magnetic head shown in FIG.
1
.
In the CPP type thin-film magnetic head shown in
FIG. 2
, the gap between the shielding layers is reduced further than the CIP type thin-film magnetic head. Additionally, the CPP type thin-film magnetic head shown in
FIG. 2
has a structure in which a current flows in a direction perpendicular to a plane of the MR element. However, the thin-film magnetic head shown in
FIG. 2
does not satisfy the requirement to use the MR element by efficiently supplying a current in a direction perpendicular to a plane of the MR element. Additionally, the thin-film device has a problem in that a free layer of the MR element may be deteriorated by an underlayer material.
It appears that a Balkhausen noise can be reduced by applying the hard magnet layer of the thin-film device shown in
FIG. 1
to the thin-film device shown in FIG.
2
. However, the structure of the hard magnetic layer shown in
FIG. 1
has a problem in that a yield rate is decreased due to a short-circuit between the MR element and the upper gap layer. Thus, mere application of the hard magnetic layer to the thin-film device shown in
FIG. 2
cannot provide a preferred effect.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful magnetoresistive device in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a current perpendicular type magnetoresistive device in which a current efficiently flows in a direction perpendicular to a plane of an MR element and the sensitivity of the MR element is increased.
Another object of the present invention is to provide a current perpendicular type magnetoresistive device which prevents generation of a leak current while reducing a Balkhausen noise.
In order to achieve the above-mentioned objects, there is provided according to
Aoshima Ken-ichi
Noma Kenji
Fujitsu Limited
Greer Burns & Crain Ltd.
Renner Craig A.
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