Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-05-30
2002-08-13
Ometz, David L. (Department: 2651)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06433969
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a compound thin-film magnetic head formed as a laminate of a playback head using a magnetoresistive effect and a recording head using a magneto-inductive effect, and to a method for manufacturing such a compound head, and more particularly to a thin-film compound magnetoresistive effect head in which it is possible to achieve sufficient insulation between magnetic shields.
2. Description of the Related Arts
In the past, compound magnetoresistive effect heads have been widely used in the writing and reading of information with respect to a magnetic recording medium.
Because of a reduction in the relative velocity between the magnetic head and the magnetic recording medium that has accompanied a reduction in size and increase in capacity of magnetic recording media, magnetoresistive effect heads (hereinafter abbreviated MR heads), in which the playback output is not dependent upon the speed, have gained attention in recent years.
MR heads are discussed in “A Magnetoresistivity Readout Transducer,” IEEE Trans. on Magnetics MAG-7 (1970), 150.
The most practical MR head, as shown in
FIG. 6
, is a compound magnetoresistive effect head formed by an MR head having two opposing magnetic shield films S
1
and S
2
, and a magnetoresistive effect (MR) element
8
provided between the magnetic shield films S
1
and S
2
with intervening magnetic gap layers
3
and
4
, i.e., magnetic separation layers made of insulation films, therebetween, and an inductive head (hereinafter abbreviated ID head) formed by one of the magnetic shield S
2
of the opposing magnetic shields S
1
and S
2
as one magnetic pole film P
1
and, on a surface of the magnetic pole film P
1
opposite from the magnetoresistive effect element
8
, a coil
90
held between an insulator and another magnetic pole film P
2
, these being laminated in parallel with the magnetic pole film P
1
, magnetic recording being performed by a magnetic field generated in a magnetic gap
95
provided between the magnetic pole films P
1
and P
2
.
FIG. 2
shows a plan view of the above-noted compound magnetoresistive effect head, viewed from the magnetic recording medium surface (air bearing surface; ABS surface).
In an MR head, because the playback track width becomes narrow with an increase in the recording density, a head was disclosed in Japanese Unexamined Patent Publication (KOKAI) No.7-57223, wherein to suppress the side fringe effect a magnetoresistive effect element is disposed only in the playback track part, a ferromagnetic film (hereinafter referred to as a magnetization stabilizer film) for the purpose of stabilizing the magnetization of the magnetoresistive effect element is disposed adjacent to the magnetoresistive effect element.
The above-noted magnetization stabilizer film is used for the purpose of stabilizing the magnetization of the magnetoresistive effect film used as a magnetoresistive effect element in one direction, thickness of this magnetization stabilizer film being determined by the saturation magnetization and thickness of the magnetoresistive effect film.
The dimension of the magnetoresistive effect element in the direction perpendicular to the medium surface (hereinafter referred to as the element height) is made small so as to correspond to the playback track width, and the magnetoresistive effect element is substantially square in shape.
The improvement of recording density is accompanied by a reduction in both the playback track width and the linear recording width.
The linear recording density is dependent upon the spacing between the magnetic shields S
1
and S
2
(hereinafter referred to as the playback gap).
With a narrowing of the playback gap, there is a reduction of the thickness of the magnetic separation film, which is an insulation film, between the magnetoresistive effect element and the magnetic shields.
In the past, in one method of establishing the element height, ion milling or the like was generally used to perform patterning to an approximate height, after which lapping was performed to establish the final element height.
When the above is done, in performing patterning by ion milling or the like, a step occurs at the etched part.
For this reason, in the past by forming a magnetic separation layer made of an insulation film before forming the magnetic shield S
2
, this step was covered, thereby preventing an electrical short circuit between the magnetoresistive effect element and the magnetic shield S
2
.
However, with an increase in the recording density, the magnetic separation layer thickness is decreased, making it difficult to completely cover the step part, so that it is not possible to maintain insulation between the magnetic shield S
2
and the magnetoresistive effect element.
The problems accompanying prior art are described below, with reference being made to FIG.
6
.
Specifically,
FIG. 6
is a cross-section view of a known compound magnetoresistive effect head (MR head) of the seen in the direction of the cutting line A—A shown in FIG.
2
and in the direction of right angle to a paper surface of this FIG.
6
.
As one of structures of the magnetoresistive effect element
8
in the above-noted MR head, a surface
50
, not in opposition to the recording medium and having a prescribed element height, is established by being patterned with ion milling or the like.
The magnetoresistive effect film (MR film)
5
generally is made of an NiFe film, and a soft magnetic layer is further laminated for applying a vertical bias to the magnetic separation layers G
1
and G
2
as well as the magnetoresistive effect film
8
.
In the case of a spin valve film, the structure is one in which a magnetization fixing layer, a magnetization free layer, and a copper film or the like are laminated.
In either case, the total thickness of the magnetoresistive effect element is approximately 50 nm. By etching the magnetoresistive effect element in the process that performs patterning so as to establish the element height, a step approximately the size of the film thickness of the magnetoresistive effect element is formed.
The resolution of the playback head in the linear density direction is dependent upon the playback gap length, and to achieve high-density recording and playback, it is necessary to make the playback gap length short.
The magnetoresistive effect element
8
is disposed between the lower magnetic shield S
1
and the upper magnetic shield S
2
, and to prevent the current flowing in the magnetoresistive effect element
8
from being divided by the magnetic shields S
1
and S
2
it is necessary to provide electrical insulation between the magnetic shields S
1
and S
2
.
For this reason, insulation films are provided between the magnetic shield S
1
and the magnetoresistive effect element
8
and between the magnetic shield S
2
and the magnetoresistive effect element
8
.
Note that, a lower magnetic gap G
1
is provided between the lower magnetic shield S
1
and the magnetoresistive effect element
8
, while the upper magnetic gap G
2
is provided between the upper magnetic shield S
2
and the magnetoresistive effect element
8
, so as to serve as insulation films therebetween.
Thus, with an increase in the linear density, the film thickness of these insulation films inevitably becomes smaller.
For this reason, because of the insulation films laminated between the magnetic shields and the magnetoresistive effect element, it is difficult to completely cover the step that is formed by the step of patterning the magnetoresistive effect element so as to establish the prescribed element height, the result being the risk that it will not be possible to maintain the insulation between the magnetic shields and the magnetoresistive effect element.
More specifically, in a conventional MR head as shown in
FIG. 6
, by restricting one of the heights of the magnetoresistive effect element by performing patterning with ion milling or the like, a step
60
occurs at the edge part of the magnetoresistive effect element
McGinn & Gibb PLLC
NEC Corporation
Ometz David L.
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