Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-10-06
2003-05-13
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S319000
Reexamination Certificate
active
06563678
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head having a magnetoresistive effect element using the magnetoresistive effect of a spin valve film or the like. More particularly, the present invention relates to a thin-film magnetic head giving an improved electrical insulation between the electrode layer of the, magnetoresistive effect element and the lower shielding layer, and a manufacturing method thereof.
2. Description of the Related Art
FIG. 21
is an enlarged sectional view illustrating a conventional thin-film magnetic head as viewed from the opposite side of a recording medium (i.e., from the “ABS” or air bearing surface plane). In
FIG. 21
, symbols X, Y and Z represent an X coordinate axis, a Y coordinate axis, and a Z coordinate axis, respectively.
This thin-film magnetic head is a read head using the magnetoresistive effect, formed on a trailing side end surface of a slider constituting, for example, a floating-type head. The thin-film magnetic head may be a head formed by laminating a write inductive magnetic head on the aforementioned read head, known generally as an MR(magnetoresistive)/inductive composite thin-film magnetic head.
In
FIG. 21
, the reference numeral
1
represents a lower shielding layer formed from Sendust or an NiFe alloy (permalloy), and a lower gap layer
4
made of a non-magnetic material such as Al
2
O
3
(alumina) is formed on the lower shielding layer
1
. A magnetoresistive effect element
5
is formed in the form of a film on the above-mentioned lower gap layer
4
. A multilayer film
6
using the magnetoresistive effect is formed at the center of the magnetoresistive effect element
5
.
The aforementioned multilayer film
6
comprises a spin-valve film (a kind of GMR type of “GmR” or giant magnetoresistive element having, for example, an anti-ferromagnetic layer, a fixed magnetic layer, a non-magnetic conductive layer, and a free magnetic layer. In this spin-valve film, magnetization of the fixed magnetic layer is fixed in a direction perpendicular to the plane of the drawing (Y-direction: height direction), and magnetization of the free magnetic layer is aligned with the track transverse direction (X-direction). When the magnetic field from the recording medium penetrates in the direction perpendicular to the plane of drawing, magnetization of the free magnetic layer varies, and electric resistance varies under the effect of the relationship between fixed magnetization of the fixed magnetic layer and varying magnetization of the free magnetic layer, thus reproducing the magnetic field of the recording.
As shown in
FIG. 21
, a hard bias layer
7
and an electrode layer
8
made of a non-magnetic conductive material having a low electric resistance such as Cr (chromium) or Ta (tantalum) are formed as a longitudinal bias layer on each side of the multilayer film
6
.
An upper gap layer
9
is formed on the magnetoresistive effect element
5
, and further, an upper shielding layer
10
is formed on the upper gap layer
9
.
Also as shown in
FIG. 21
, the lower gap length GL
1
is determined from the thickness of the lower gap layer
4
formed under the magnetoresistive effect element
5
, and the upper gap length GL
2
is determined from the thickness of the upper gap layer
9
formed on the magnetoresistive effect element
5
. The read gap length GL is set from the thickness of the magnetoresistive effect element
5
, the lower gap length GL
1
and the upper gap length GL
2
.
FIG. 22
is a plan view of the magnetoresistive effect element
5
formed on the lower gap layer
4
. As shown in
FIG. 22
, the multilayer film
6
and the electrode layer
8
forming the magnetoresistive effect element
5
are exposed to the ABS plane serving as an opposite surface to the recording medium, and the electrode layer
8
extends to the rear side (Y-direction: height direction) from the multilayer film
6
. The electrode layer
8
is formed so as to become larger in width toward the rear side.
Along with the recent tendency toward a higher recording density, it is necessary to form the lower gap length GL
1
and the upper gap length GL
2
shown in
FIG. 21
into smaller sizes.
However, when the gap layers
4
and
9
are formed into smaller thickness with a view to reducing the sizes of the lower gap length GL
1
and the upper gap length GL
2
, defects such as pinholes are produced in the gap layers
4
and
9
(which serve to maintain insulation between the shielding layers
1
and
10
and the magnetoresistive effect element
5
), resulting in electric connection between the shielding layers
1
and
10
and the magnetoresistive effect element
5
.
Particularly, the above-mentioned problem tends to be created between the electrode layer
8
having a large width formed on the rear side from the ABS plane and the shielding layers
1
and
10
as shown in
FIG. 22
, resulting in a lower reproducing property due to electric connection between the shielding layers
1
and
10
and the electrode layer
8
.
Upon manufacturing a thin-film magnetic head, the ABS plane of the multilayer film
6
is ground (height-making fabrication in the height direction (Y-direction in FIG.
22
), until a specified DC resistance of the multilayer film
6
(shown in FIG.
22
): s obtained. This height-making fabrication causes smearing between the shielding layers
1
and
10
and the electrode layer
8
, tending to make electric connection between the shielding layers
1
and
10
and the electrode layer
8
.
When the shielding layers
1
and
10
and the electrode layer
8
are electrically connected, the height-making fabrication cannot be applied because of inaccurate measuring of the DC resistance of the multilayer film
6
.
SUMMARY OF THE INVENTION
The present invention was developed for the purpose of solving the conventional problems as described above, and relates to a thin-film magnetic shead which can maintain an appropriate electric insulation between the shielding layer and electrode layer of the magnetoresistive effect element even for a small gap length and permits obtaining a stable reproducing property, thereby coping with the tendency toward a higher recording density, and a manufacturing method thereof.
The present invention provides a thin-film magnetic head comprising a lower shielding layer and a lower gap layer formed thereon, a magnetoresistive element comprising a multilayer film displaying magnetoresistive effect and formed on said lower gap layer and an electrode layer connected to said multilayer film, and an upper shielding layer formed on the magnetoresistive effect element via the upper gap layer; wherein an insulating layer is formed in addition to the lower gap layer between the electrode layer and the lower shielding layer.
In the invention, the insulating layer should preferably be arranged at least on each side of the multilayer film or a reproducing track width.
In the invention, furthermore, the lower gap layer and the insulating layer should preferably have a total thickness of at least 700 Å.
In a detailed structure in the invention, an insulating layer should preferably be formed on the lower shielding layer, and the electrode layer should preferably be formed on the insulating layer with the lower gap layer interposed therebetween.
A slant should preferably be formed on each of the sides of the insulating layer.
In the invention, the insulating layer should preferably be formed with one or more insulating materials selected from the group consisting of SiO
2
, Al
2
O
3
, Ta
2
O
5
, TiO, Ti
2
O
3
, Ti
3
O
5
, WO
3
, Si
3
N
4
and AlN.
In a detailed structure in the invention, a recess should preferably be formed on the surface of the lower shielding layer, with an insulating layer formed in the recess, and the electrode should preferably be formed on the insulating layer with the lower gap layer interposed therebetween.
In this case, the surface of the lower shielding layer should preferably be flush with the surface of the insulating layer formed in the recess of
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Renner Craig A.
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