Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-09-21
2002-05-21
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S122000
Reexamination Certificate
active
06392851
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a complex head consisting of a reading head making use of a magnetroresistance effect and an inductive recording head. The complex head is used for, for example, a magnetic recording and reproducing apparatus.
2. Description of the Prior Art
Heretofore, there is a tendency that a size of a record bit on a magnetic record medium rapidly becomes small in size as magnetic record mediums become small in size and vast in capacity. In order to deal with such tendency, a magnetroresistance effect type head (hereinafter, referred to as “MR head”) which has a high-level output has been put to practical use. An MR head is discussed in “A Magnetroresistivity Readout Transducer” (IEEE Transaction on Magnetics, MAG 7 (1971), p.150).
FIGS. 1A
,
1
B, and
2
show magnetroresistance effect type complex head (hereinafter, referred to as “MR complex head”) consisting of an MR head for reading and an inductive head (hereinafter, referred to as “ID head”) for recording as a first prior art.
FIG. 1A
is a plan view,
FIG. 1B
is a cross-sectional view taken along line A-A′ in
FIG. 1A
, and
FIG. 2
is a front elevation.
FIG. 2
is taken from the left of
FIG. 1A
or
1
B. A plane shown in
FIG. 2
confronts a record medium and referred to as an air-bearing plane.
Referring to
FIGS. 1A and 1B
, members indicated by reference numerals
31
and
32
are insulators, a number indicated by reference numeral
33
is a coil pattern. Coil pattern
33
is visible in
FIG. 1A
because insulator
31
is semi-transparent.
Referring to
FIG. 2
, the MR head comprises two face-to-face magnetic shield films S
1
indicated by
10
and S
2
indicated by
17
, magnetic separators
11
and
16
comprising insulators, and magnetroresistance effect element (hereinafter, referred to as “MR element”)
15
disposed between magnetic shield film S
1
(
10
) and magnetic shield film S
2
(
17
) with interposition of magnetic separators
11
and
16
. The ID head comprises a magnetic pole film P
1
indicated by
17
, magnetic pole film P
2
indicated by
19
, and magnetic gap
18
. Therefore, the portion indicated by
17
is magnetic shield film S
2
as well as magnetic pole film P
1
.
The MR complex head causes a considerably strong side fringe magnetic field while recording. This side fringe magnetic field is caused by a leakage of a magnetic flux to a portion of magnetic pole film P
1
(
17
) over a width of magnetic pole film P
2
(
19
) because magnetic pole film P
1
(
17
) is wider than magnetic pole film P
2
(
19
). This side fringe magnetic field restricts an allowable minimum track width and therefore a track density. Therefore, it is necessary to reduce this side fringe magnetic field in order to attain a high-density magnetic recording with an MR complex head.
A conventional ID head for recording/reading caused a weak side fringe magnetic field because the conventional ID head was so designed that a lateral side of magnetic pole film P
1
and a lateral side of magnetic pole film P
2
are substantially disposed on a same plane at and near to an air bearing surface at both lateral sides. The lateral sides determines a track width. On the other hand, as to an MR complex head, magnetic pole film P
1
(
17
) is considerably wider than magnetic pole film P
2
(
19
) of which width determines a track width because magnetic pole film P
1
(
17
) needs to have a function to shield an MR element
15
. This difference in width causes a side fringe magnetic field which extends over a width of magnetic pole film P
2
(
19
) laterally.
A second prior art is an MR complex head disclosed in JPA 7-262519 and shown in
FIG. 3
, and it causes as weak a side fringe magnetic field as an ID head. Referring to
FIG. 3
, the second prior art MR complex head comprises magnetic pole film P
3
which is indicated by
17
′. Magnetic pole film P
3
(
17
′) is disposed between magnetic pole film P
1
(
17
) and magnetic gap G (
18
) and parallel to a surface of magnetic pole film P
1
(
17
), and magnetically continues with magnetic pole film P
1
(
17
). Each of two lateral sides of magnetic pole film P
3
(
17
′) is disposed on the same plane with each of two lateral sides of magnetic pole film P
2
(
19
) which determines a width of magnetic pole film P
2
(
19
). Also, each of two lateral sides of magnetic pole film P
3
(
17
′) is perpendicular to a surface of magnetic pole film P
1
(
17
). On such structure, a magnetic field for recording is caused between magnetic pole film P
2
(
19
) and magnetic pole film P
3
(
17
′), and therefore a side fringe magnetic field is suppressed as a conventional ID head.
The method for manufacturing magnetic pole film P
3
(
17
′) is shown in FIG.
4
. Referring to
FIG. 4
, magnetic gap G (
18
) is formed on magnetic pole film P
1
(
17
) which is also used as a magnetic shield S
2
of an MR head. Then, a coil insulated by a photoresist is formed. Then, magnetic pole film P
2
(
19
) having a prescribed width is formed by frame plating process with restriction by photo resist frame
23
. Then, magnetic pole film P
3
(
17
′) is formed to a desired edged depth by an ion beam milling using magnetic pole film P
2
(
19
) as a mask. When forming magnetic pole film P
3
(
17
′), it is possible to make lateral sides of magnetic pole film P
2
(
19
) and P
3
(
17
′) perpendicular to an upper surface of magnetic pole film P
1
(
17
). By setting a depth of magnetic pole film P
3
(
17
′) to the desired value, a recording magnetic flux is substantially restricted by magnetic pole films P
2
(
19
) and P
3
(
17
′), and therefore a side fringe magnetic field is suppressed as a conventional ID head.
As explained above, in the method for manufacturing the MR complex head according to the second prior art, the ion beam milling is heavily used for forming magnetic pole film P
3
(
17
′). A thickness of magnetic pole film P
2
(
19
) decreases as the milling continues because magnetic pole film P
2
(
19
) serves as a mask during the milling. Therefore, an initial thickness of magnetic pole film P
2
(
19
) must be set in consideration of the decrease due to the milling in order to obtain a desired final thickness of magnetic pole film P
2
(
19
). In addition, in the method for manufacturing the MR complex head according to the second prior art, a height of frame
23
must be set considerably high as compared to a conventional method for forming initial magnetic pole film P
2
(
19
) by the frame plating process. That is, magnetic pole film P
2
(
19
) before the milling must be considerably thick in order to obtain a thickness of magnetic pole film P
2
(
19
) after the milling which ensures recording characteristics because the thickness of magnetic pole film P
2
(
19
) after the milling is considerably decreased as compared with the thickness thereof before the milling. However, if a height of frame
23
is set high in order to form a magnetic pole film P
2
(
19
) of a sufficient thickness, it is difficult to narrow a distance between two parts of frame
23
. The lower limit of the distance between the two parts of frame
23
is 2 &mgr;m in the second prior art. That is, it was difficult to manufacture an MR complex head which realizes a high recording density of a track width of under 2 &mgr;m according to the method for manufacturing the MR complex head according to the second prior art.
As explained above, when the structure for reducing a side fringe of a recording magnetic field generated by an ID head is selected for an MR complex head comprising an MR head and an ID head, it paradoxically becomes difficult to manufacture the structure for a narrow track.
One of methods for solving such dilemma is setting a width of magnetic pole film P
2
and forming magnetic pole film P
3
in combination by a ion beam edging from an air bearing surface during a bar process after having finished a wafer process instead of setting the width of magnetic
Ishi Tsutomu
Ishiwata Nobuyuki
Foley & Lardner
Klimowicz William
NEC Corporation
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