Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-03-23
2004-05-25
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06741430
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head, and, more particularly, to a technology which is suitable for preventing smearing of a surface of the thin-film magnetic head which slides with respect to a medium or a surface of the thin-film magnetic head which opposes the medium, and which is suitable for preventing smearing in a lapping process in a method of producing the thin-film magnetic head.
2. Description of the Related Art
Since, in thin-film magnetic heads having a magnetoresistive element, tracks can be made even more narrower than those in conventional bulk-type magnetic heads, thin-film magnetic heads are used in various forms, such as sliding magnetic heads which are constructed so as to slide relative to a tape having a high recording density, and flying magnetic heads which move relative to a magnetic disk while they are separated therefrom.
A sliding magnetic head which has a conventional thin-film magnetic head structure will be described with reference to
FIGS. 19
to
23
.
FIG. 19
is a perspective view of a conventional sliding magnetic head.
FIG. 20
is a schematic plan view of a main portion of the sliding magnetic head as viewed from a side of a surface of the sliding magnetic head opposing a medium.
FIG. 21
is a sectional view taken along line XXI—XXI of FIG.
20
.
FIG. 22
is an enlarged plan view of an MR element
105
shown in FIG.
20
and the vicinity thereof.
A sliding magnetic head B shown in
FIG. 19
is formed in the following way. Side end surfaces of block-shaped core bases
202
and
203
are adhered together through a core-incorporated layer
205
to form an integral structure which is block-shaped as a whole. Then, one of the side surfaces of each of the core bases
202
and
203
(which are adhered together) are adhered and secured to a base plate
201
so that one side of each of the core bases
202
and
203
protrudes slightly outwardly from an end of the base plate
201
.
One surface of the sliding magnetic head B protruding outwardly from the base plate
201
is formed into a protruding, curved shape. As shown by the phantom lines in
FIG. 19
, this surface is formed as a surface
206
which slides with respect to a magnetic recording medium such as a magnetic tape.
As shown in
FIGS. 20 and 21
, a write head (hereinafter referred to as “inductive head”)
210
used to perform a recording operation and a thin-film magnetic read head
211
which includes a magnetoresistive element are incorporated in the core-incorporated layer
205
.
The thin-film magnetic read head
211
is formed by successively placing upon the core base
202
a lower shield layer
101
, a lower insulating layer
104
, a magnetoresistive (MR) element
105
, an upper insulating layer
106
, and an upper shield layer
107
.
As shown in
FIG. 20
, ends of the lower shield layer
101
, the lower insulating layer
104
, the MR element
105
, the upper insulating layer
106
, and the upper shield layer
107
are exposed at the surface
206
.
Here, a read magnetic gap G is formed by the lower insulating layer
104
and the upper insulating layer
106
. The upper shield layer
107
and the lower shield layer
101
are formed of, for example, an alloy of nickel and iron, and the upper insulating layer
106
and the lower insulating layer
104
are formed of, for example, Al
2
O
3
.
In the structures shown in
FIGS. 20 and 21
, the upper shield layer
107
is also a lower core layer of the inductive head
210
which is formed thereabove. A write gap layer
110
is formed above the lower core layer (or the upper shield layer)
107
. A coil layer
111
which is formed into a pattern so as to form a spiral in a plane is formed on the write gap layer
110
, and is surrounded by a coil insulating layer
112
. On the surface
206
, an end
113
a
of an upper core layer
113
formed on the coil insulating layer
112
opposes the lower core layer
107
through the write insulating layer
110
so as to be separated by a very small distance from the lower core layer
107
. A base end
113
b
of the upper core layer
113
is magnetically connected to the lower core layer
107
. A protective layer
116
is formed on the upper core layer
113
. In
FIG. 21
, reference numeral
108
denotes a detecting electrode which is connected to the MR element
105
. The electrode
108
is wired on both sides of the MR element
105
.
More specifically, as shown in
FIG. 22
, the MR element
105
comprises a magnetoresistive film (MR film)
105
a
and bias layers
105
b
and
105
b
. The MR film
105
a
is used to read out magnetically recorded data from a medium by the magnetoresistive effect. The bias layers
105
b
and
105
b
are provided on both the left and right sides of the magnetoresistive film
105
a
so as to cover ends of the magnetoresistive film
105
a.
Edges
105
c
and
105
c
are formed on both sides of the MR element
105
. Therefore, as shown in
FIG. 22
, the thickness of the upper insulating layer
106
is S
1
, but the thickness of the portions of the upper insulating layer
106
corresponding to the locations of these edges
105
c
and
105
c
are S
2
, which are smaller than S
1
.
When the sliding magnetic head B slides with respect to a medium, such as a magnetic tape, which moves in the direction of arrow T
1
shown in
FIG. 22
, magnetically recorded data is read out from the medium. When a guard bandless recording operation is carried out using a helical scanning type magnetic recording/reproducing device, what is called an azimuthal recording/reproducing operation (which is carried out by tilting a magnetic gap by a predetermined angle (that is, an azimuthal angle in the widthwise direction of a track) is carried out. Therefore, the medium, such as a magnetic tape, moves in the direction of arrow T
2
shown in FIG.
22
.
The sliding magnetic head B is produced, for example, in the following way.
Using a technique for forming a thin layer, the thin-film magnetic head
211
(which comprises the MR element
105
) and the inductive head
210
are successively formed on the core base
202
in order to form the core-incorporated layer
205
.
Here, as shown in
FIG. 23
, a method of producing the MR element
105
and the vicinity thereof is carried out to form the lower insulating layer
104
, bias layers
105
b
′ and
105
b
′, and MR films
105
a
′ and
105
a
″ on the lower shield layer
101
. A pattern, such as a resist pattern, is used to cover the bias layers
105
b
′ and
105
b
′ and the MR films
105
a
′ and
105
a
″. After removing the MR film
105
a
″ and part of the bias layers
105
b
′ and
105
b
′ by milling, the upper insulating layer
106
is placed thereon, as shown in FIG.
22
. Here, the MR film
105
a
″ is completely removed by use of ion milling process, so that the bias layers
105
b
′ and
105
b
′ are formed with the corresponding edges
105
c
, as shown in FIG.
22
.
A different core base, that is, the core base
203
is joined to the core-incorporated layer
205
in order to form a core block. One surface of the core block is lapped by, for example, a lapping tape which has diamond grains distributed thereon in order to process the protruding, curved shaped surface
206
, whereby the sliding magnetic head B is formed.
Even non-contact, flying magnetic heads used with, for example, hard disks, are constructed so as to include an MR element such as that described above. Accordingly, even in producing such flying magnetic heads, the lapping process is carried out after the formation of the MR element. In the lapping process, a lapping tape, such as that described above, is used in order to lap the surface of the magnetic head which faces the magnetic recording medium.
However, in the sliding magnetic head B, the upper shield layer
107
and the lower shield layer
101
which sandwich the upper insulating layer
106
and the lower insulating layer
104
are formed of an alloy of nickel and iron which has r
Alps Electric Co. ,Ltd.
Cao Allen
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