Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-03-19
2003-12-16
Watko, Julie Anne (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06665143
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims benefit of priority under 35USC § 119 to Japanese Patent Application No. 2000-95082, filed on Mar. 30, 2000, the contents of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a magnetic head and a method for producing the same, and magnetic recording and/or reproducing system.
2. Description of Related Art
It is generally known that the efficiency of a magnetic head is rapidly improved as the magnetic path length of a magnetic circuit decreases. For example, as shown in
FIG. 18A
, the efficiency is rapidly improved as the magnetic path length decreases to 2 &mgr;m (=2000 nm) or less. As shown in
FIG. 18B
, the magnetic path length means the length of a magnetic circuit passing through a magnetic substance portion
52
a
, magnetic substance portion
53
a
, magnetoresistance effect element (e.g., GMR (giant magnetoresistance effect) element), magnetic substance portion
53
b
and magnetic substance portion
52
b
of a magnetic head.
The construction of a first example of a conventional magnetic head is shown in FIG.
19
. This conventional magnetic head comprises a pair of magnetic substance portions
51
a
and
51
b
which are constructed so as to form two different gaps G
1
and G
2
, and a magnetoresistance effect element
56
which is provided in the gap G
2
. The construction of a second example of a conventional magnetic head is shown in FIG.
20
. The magnetic head in this second example comprises a pair of magnetic substance portions
52
a
and
52
b
which are arranged so as to be spaced from each other by a gap G
1
, a pair of magnetic substance portions
53
a
and
53
b
which are arranged so as to be spaced from each other by a gap G
2
which is greater than the gap G
1
, and a magnetoresistance effect element
56
which is formed as a bridge between the magnetic substance portions
53
a
and
53
b
. In the first and second examples, the gap G
1
is formed so as to be more close to a medium facing surface than the gap G
2
.
The magnetic substance portions
51
a
and
51
b
of the magnetic head in the first example are formed by lithography at separate steps, respectively, and the pair of the magnetic substance portions
52
a
and
52
b
and the pair of magnetic substance portions
53
a
and
53
b
of the magnetic head in the second example are formed by lithography at separate steps, respectively.
Therefore, there is a limit to the formation of a fine magnetic path due to an alignment error and the resolution of a photolithography system. For example, even if an advanced stepper is used, there is an alignment error due to the mechanical alignment precision (50 nm) of the stepper and the deformation of the substrate, so that an error of 400 nm is caused. In order to decrease the producing costs, an inexpensive excimer laser is often used for lithography. When the excimer laser is used, the resolution is about 200 nm. As can be seen from
FIG. 21
, the alignment error expresses a shift from the center of the gap G
1
, so that the whole alignment error is 800 nm (=400 nm×2). For that reason, it is not possible to form a magnetic head having a magnetic path length which is equal to or less than a value (2000 nm) obtained by doubling a value (1000 nm) obtained by adding the resolution of 200 nm to the alignment error of 800 nm.
As shown in
FIG. 21
, in order to form a small magnetic path having a high efficiency, it is required to decrease both of the length G
2
of a magnetic gap on the opposite side to a medium facing surface
58
and the height H from the medium facing surface
58
to a magnetoresistance effect element
58
. In order to increase the line resolution, it is also required to decrease the length G
1
of a magnetic gap on the side of the medium facing surface (about 50 nm).
However, in conventional magnetic head structures and conventional methods for producing the same, these requirements can not be satisfied.
Ironically, as can be seen from
FIG. 18A
, the efficiency of a magnetic head is rapidly improved when the magnetic path length is about 2000 nm or less which can not be formed in the prior art. Even if a small magnetic path is formed by a conventional magnetic head structure, the efficiency is rapidly lowered in the reproduction of a shorter wavelength signal (0.1 &mgr;m or less) required in recent years although the reason for this is not clear, so that it can not be used as a high-density recording head. This is the same during a recording operation, not only during a reproducing operation. In conventional recording heads, the efficiency is greatly lowered in the recording at a shorter wavelength although the reason for this is not clear, so that it is not possible to record on low noise medium for a high density, which exceeds 50 Gbpsi (Giga bit per square inch), using current which can be supplied by a recording IC (Integrated Circuit).
It was found that the lowering of the recording/reproducing efficiency in a shorter wavelength region was remarkable when the length of a magnetic path approaches the order of the thickness (100 nm) of a magnetic domain wall of a magnetically soft substance.
As described above, in all of the conventional head structures, a thin-film is patterned by lithography to form a magnetic circuit. Therefore, even if a small magnetic circuit is intended to be formed, there is a limit to the increase of the efficiency of the head. Moreover, even if a desired head can be available with low yields, there is a problem in that the recording/reproducing efficiency at a shorter wavelength is greatly lowered so that it is not possible to record/reproduce at a high density.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a magnetic head capable of recording or reproducing with a high efficiency even in the case of a shorter magnetic path length and a shorter wavelength signal, a method for producing the same, and a magnetic recording and/or reproducing system using the same.
In order to decrease the magnetic path length as short as possible, a magnetic head shown in, e.g.,
FIG. 17
, is considered. That is, a pair of magnetic substance portions
54
a
and
54
b
are arranged so as to spaced from each other by a predetermined gap G, and a magnetoresistance effect element
56
is provided so as to construct a bridge between the magnetic substance portions
54
a
and
54
b.
This magnetic head can not be used as a high-density magnetic head since it has a low reproducing efficiency or a bad reproducing resolution although it is suited to decrease the magnetic path length. That is, when the magnetic gap length G is small, most of magnetic fluxes from the medium flow into the magnetic gap, and only part of magnetic fluxes flow into the magnetoresistance effect element, so that it is not possible to obtain a great output. On the other hand, when the magnetic gap length is great, the line resolution is extremely bad, so that the magnetic head is not worth being used as a tip magnetic head for high density.
Therefore, in order to accomplish the aforementioned and other objects, the inventors have invented a magnetic head having the following construction and a method for producing the same.
According to a first aspect of the present invention, a magnetic head comprises: a pair of magnetic bodies comprising respective first and second medium facing surfaces, respective first and second rear surfaces opposite to the medium facing surfaces, and respective inner side surfaces, the inner side surfaces facing each other; and a magnetic gap disposed between the inner side surfaces and comprising third medium facing surface coplanar with the first and the second medium facing surfaces and third rear surface coplanar with the first and second rear surfaces; one of the inner side surfaces satisfying relationships of
x=G
1
/2 with respect to 0≦
y≦TH
, and
0.1·tan{2(
x−G
Funayama Tomomi
Osawa Yuichi
Yoda Hiroaki
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