Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
1997-04-16
2001-08-28
Miller, Brian E. (Department: 2754)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
C360S125330
Reexamination Certificate
active
06282061
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head used in a magnetic disk apparatus for recording information on and reproducing information from a recording medium.
Recently, as the size of a magnetic disk apparatus has been reduced and the storage capacity thereof has been enlarged, the recording density of a recording medium has become high, and thus a magnetic head which floats low over the disk (small clearance) is required. However, because of the requirement that the magnetic head be resistant to shock, there is also a need to reduce occurrences of contact between the magnetic head and the disk.
2. Description of the Related Art
FIGS. 1A
,
1
B and
1
C show a construction of a conventional magnetic head. Referring to
FIG. 1A
, two rail surfaces
13
a
and
13
b
are formed on the surface of a core slider
12
of a magnetic head
11
, which surface faces a magnetic disk (recording medium). The rail surfaces
13
a
and
13
b
are made to extend in the direction in which air flows. Tapered surfaces
14
a
and
14
b
which allow the head to float are formed on the side at which air enters the space between the head and the disk.
On an end face of the rail surface
13
a
at which face air exits the space between the head and the disk, a thin-film element
15
for writing and reading information is provided. As shown in
FIG. 1B
, the thin-film element
15
is formed such that an insulating film (alumina)
16
is formed on the end face of the core slider
12
(rail surface
13
a
), and a magnetic film
17
is formed on the insulating film
16
. An insulating film
18
is formed on the magnetic film
17
, and a coil
19
is provided in the insulating film
18
. A magnetic film
20
is formed on the insulating film
18
. Recording and reproduction are performed in a gap
22
formed between the magnetic film
17
and the magnetic film
20
. A protective film (insulating film)
21
is formed on the magnetic film
20
in the thin-film element
15
. The shaded area indicates that portion of the protective film which is susceptible to temperature increase.
The rail surfaces
13
a
and
13
b
are chamfered (applied with a lapping process) as indicated by broken lines in
FIG. 1C
so as to allow air to flow smoothly. Both the width and height of the chamfering are 0-10 &mgr;m. A distance L between the end face of the core slider
12
and the end of the protective film
21
is set such that L≧0.025 mm. A distance S (thickness of the protective film) between the magnetic film
20
and the end of the protective film
21
is set such that S≈0.015-0.02 mm.
The magnetic head
11
is enabled to float over the magnetic disk by receiving an air flow generated by the rotating magnetic disk. In order that damage caused by the contacting of the magnetic head
11
with the magnetic disk be minimized, a thin film of DLC (diamond-like carbon) or the like may be provided on the rail surfaces
13
a
and
13
b
(including the tapered surfaces
14
a
and
14
b
) and/or on the magnetic disk, or burrs created by the chamfering of the rail surfaces
13
a
and
13
b
may be removed.
FIG. 2
explains thermal expansion of the protective film of the conventional magnetic head. Referring to
FIG. 2
, when the magnetic head
11
is driven for a recording operation, the temperature of the thin-film element
15
rises because a current is fed to the coil
19
, with the result that the protective film
21
swells due to thermal expansion, as indicated by a shaded end part
21
′ in FIG.
2
. For example, it was experimentally found that a swelling of the protective film
21
of alumina measured 6 nm per temperature rise of 10° C.
Hence, the narrowest achievable separation (clearance) between the magnetic head
11
and the magnetic disk depends on the magnitude of the swelling of the protective film
21
and on the spacing between the head and the disk. Accordingly, frequent contacts between the head and the disk may occur. Powder created from abrasion damages the thin-film element
15
and the disk. Therefore, it becomes difficult to secure small clearance.
Further, the chamfering of the rail surfaces
13
a
and
13
b
of the core slider
12
is done after a wafer having the thin-film element
15
formed thereon is cut and the rail surfaces
13
a
and
13
b
are formed. If the chamfering process is applied to the thin-film element
15
, a variation in the quality of the produced head results. For example, the electromagnetic transducing property may deteriorate.
Furthermore, the conventional magnetic head is liable to be affected by a fine projection located on the magnetic disk. If the magnetic head is affected by such a fine projection, an abnormal signal will be superimposed on the read signal, as will be described in detail later.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful magnetic head in which the aforementioned problems of the prior art are eliminated.
A more specific object of the present invention is to provide a magnetic disk apparatus equipped with a MR head that therefor; has an improved structure which makes it possible for a fine projection on the magnetic disk to hit the MR head without causing an abnormal reproduction signal therefor.
The above objects of the present invention are achieved by an MR head comprising: a slider; and a film structure part which is located on an air outflow side of the slider and includes an MR element for reproducing, the film structure part having an end sign surface located on an identical side as a floating surface of the slider, the end surface of the film structure part and the floating surface of the slider forming a step-like recess which has a depth making it possible to prevent a fine projection on a magnetic disk from hitting the end surface of the film structure part.
The MR head may be configured so that the depth of the step-like recess an end of the MR element on the end surface of the film structure part to be located on or above an imaginary line which passes through a rear edge of the slider and the end of the MR head when the MR head is in a floating state at a given floating angle.
The MR head may be configured so that: the depth of the step-like recess has a length equal to or greater than a sum of a first length and a second length; the first length causes an end of the MR element on the end surface of the film structure part to be located on an imaginary line which passes through a read edge of the slider that is in a floating state at a given angle and which is parallel to the magnetic disk; and the second length corresponds to a magnitude of a swelling of the end surface of the film structure part, the swelling being formed when the film structure part is thermally deformed.
The MR head may be configured so that: the depth of the step-like recess has a length equal to or greater than a sum of a first length and a second length; the first length causes an end of the MR element on the end surface of the film structure part to be located on an imaginary line which passes through a read edge of the slider that is in a floating state at a given angle and which is parallel to the magnetic disk; and the second length corresponds to a descending movement of the MR head after the MR head is pushed upwardly by the fine projection, the descending movement including an overshooting movement.
The MR head may be configured so that: the depth of the step-like recess causes has a length equal to or greater than a sum of a first length, a second length, and a third length; the first length causes an end of the MR element on the end surface of the film structure part to be located on an imaginary line which passes through a read edge of the slider that is in a floating state at a given angle and which is parallel to the magnetic disk; the second length corresponds to a magnitude of a swelling of the end surface of the film structure part, the swelling being formed when the film structure part is thermally deformed; and the thir
Kamiguchi Muneo
Kanda Koki
Kiuchi Katsumi
Koshikawa Takao
Sone Katsuhide
Fujitsu Limited
Greer Burns & Crain Ltd.
Miller Brian E.
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