Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1995-08-22
2001-04-03
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06212034
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head having horizontal pole pieces. It is used in magnetic recording.
2. Discussion of the Background
A known magnetic head is shown in section in FIG.
1
and in plan view in FIG.
2
. On a substrate
8
, said head has a first subassembly
10
constituted by a lower magnetic layer
12
, two magnetic pillars
14
1
,
14
2
resting on said magnetic layer
12
and a conductor winding
18
surrounding the pillars
14
1
,
14
2
. On said subassembly
10
there is a central, insulating pin or ridge
19
having two inclined sides and a flat apex. On the subassembly
10
and overlapping the central, insulating ridge
19
there is a second subassembly
20
formed from two portions, namely a first portion constituted by two magnetic flux concentrators
22
1
,
22
2
with an outer, wide end bearing on the pillars
14
1
,
14
2
and an inner, narrower end, as well as a second portion constituted by two pole pieces
24
1
,
24
2
separated by a head gap
26
and in contact with the concentrators
22
1
,
22
2
. These pole pieces have an elongated S shape with an oblique median portion covering the inclined sides of the pin
19
.
FIG. 3
shows in detailed manner the right-hand half of the second subassembly
20
. This drawing makes it possible to define a few dimensions and a few particular zones. The pole pieces have a thickness Ee at the head gap
26
and Ep remote from the head gap. The ridge or pin
19
has a half-length Lp. The concentrators
22
2
have a thickness Ec. The movement plane of the head is at a distance H from the upper surface of the concentrators. The angle formed with the horizontal by the pole piece in its inclined portion is designated &thgr;. Moreover, the point G designates the centre of the head gap, the point A marks the limit of the straight zone of a pole and point P corresponds to the zone where the pole piece leaves the movement plane and becomes inclined.
Although these heads are satisfactory in certain respects, they still suffer from disadvantages when the width of the recording track becomes small and the operating frequency high. These different disadvantages can be analyzed in the following way.
The construction of the pole pieces imposes a monolithic structure for the same. With a considerable thickness of the pole pieces, eddy currents appear and create heating, as well as a reduction of efficiency. By reducing the thicknesses Ep and Ec, this effect is reduced, but to the detriment of the overall efficiency, as well as the maximum field obtained in the head gap under saturation conditions. Thus, there is a maximum and minimum limitation for the thickness Ep.
As shown in
FIG. 4
, the reading signal, apart from the main peak Pp, has two small secondary peaks Ps
1
, Ps
2
at a distance of approximately L corresponding to point P in
FIG. 3
, where the poles are no longer in the movement plane. The height of these parasitic peaks is also dependent on the angle &thgr; obtained during the production of the ridge or pin.
In order to obtain a maximum field in the head gap on writing, it is necessary to move the point A (saturation appearance point) towards the head gap. It is then necessary to reduce the half-length Lp of the ridge without modifying the optimum angle &thgr;, which must remain small in order to ensure the quality of the magnetic deposit. This reduction is difficult for lengths below 5 &mgr;m. Moreover, the production of the head gap on a ridge of limited length also becomes very difficult.
Thus, the track width reduction and the obtaining of a larger field in the head gap require the reduction of the size of the relief and the retention of a small angle &thgr;. This leads to technological problems in producing the ridge and the head gap for small track widths.
In order to avoid parasitic rereading of adjacent tracks, the poles must have a width equal to that of the track to be read and the introduction of a concentrator with a wide section towards the pillars and a narrow section towards the head gap makes it possible to retain a good efficiency. However, a relatively large height H is necessary to avoid any rereading in the presence of the wide section of the concentrator. Moreover, at high frequency, the considerable thickness Ep+Ec of the pole pieces and the concentrator is prejudicial with respect to eddy currents and it is necessary to reduce each thickness and magnetically decouple the layers.
SUMMARY OF THE INVENTION
The object of the present invention is to obviate these disadvantages.
The invention modifies the structure of the second subassembly
20
in
FIGS. 1
to
3
in such a way that the two pole pieces are horizontal and no longer have an elongated S shape with an oblique median portion. In other words, the pole pieces are in the form of straight bars. Conversely, it is the concentrators which have an inclined portion, which bears on one of the inclined sides of the ridge or pin. These arrangements allow:
the reduction of the half-length Lp of the ridge and the moving closer of the head gap point A and thus it is possible to obtain a maximum field in the head gap,
the production of a head gap on a planar surface,
the transfer of the point P to the origin of the parasitic peaks remote from the main magnetic circuit,
a better control of the pole pieces which are produced flat, particularly with regards to the composition and orientation of the domains or fields,
the reduction of the thickness Ep of the poles (which reduces eddy currents and facilitates the orientation of the domains or fields) without reducing the overall efficiency of the head.
More specifically, the present invention relates to a magnetic head of the type described relative to
FIGS. 1 and 3
and which is characterized in that, in the second subassembly located on the upper portion of the head:
the two concentrators have their inner end bearing on the two inclined sides of the central, insulating ridge, said ends being flush with the apex of the ridge,
the two pole pieces are constituted by two straight bars bearing on the flat apex of the ridge and on the inner ends of the two concentrators, said bars being extended beyond said ends and overhang said concentrators.
REFERENCES:
patent: 2908770 (1959-10-01), Warren
patent: 4837924 (1989-06-01), Lazzari
patent: 4949207 (1990-08-01), Lazzari
patent: 4984118 (1991-01-01), Springer
patent: 4992897 (1991-02-01), Deroux-Dauphin
patent: 5195006 (1993-03-01), Morikawa
patent: 5224260 (1993-07-01), Fedeli et al.
patent: 5274520 (1993-12-01), Matsuzono et al.
patent: 5274521 (1993-12-01), Miyauchi et al.
patent: 0 472 187 (1992-02-01), None
patent: 2 676 301 (1992-11-01), None
patent: 2 687 497 (1993-08-01), None
Patent Abstracts of Japan, vol. 7, No. 121, May 25, 1983, and JP-A-58 037830, Mar. 5, 1983.
IBM Technical Disclosure Bulletin, vol. 31, No. 3, pp. 291-292, Aug. 31, 1988, “Film Head Structure Optimized for Writing”.
Patent Abstracts of Japan, vol. 18, No. 429, Aug. 10, 1994, JP-A-6 131635, May 13, 1994.
Cuchet Robert
Fedeli Jean-Marc
Germain Céline
Commissariat A l'Energie Atomique
Klimowicz William
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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