Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2002-11-12
2003-11-18
Dinh, Tan (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C360S324100
Reexamination Certificate
active
06650598
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording/reproducing head and a recording/reproducing apparatus incorporating the recording/reproducing head. More particularly, the present invention relates to a recording/reproducing head, a recording/reproducing apparatus, and a fabrication method thereof which are capable of higher-density recording than conventional hard disks and magneto-optical disk apparatuses.
2. Description of the Related Art
A hard disk drive (HDD)
1000
represented in
FIG. 11
or a magneto-optical disk (MO) apparatus
2000
represented in
FIG. 12
can record information signal in high density. These apparatuses include a magnetic head
1019
and a magneto-optical head
2020
, respectively, as a recording/reproducing head.
When the magnetic head
1019
as shown in
FIG. 11
is used to attempt to obtain high-density recording/reproducing which exceeds about 40 Gb/inch
2
, reproducing is feasible if a giant magnetoresistive (GMR) device
1014
is provided between shields
1015
. In a structure of the magnetic head
1019
in which a surface of the GMR device
1014
is exposed, friction or noise occurs due to the GMR device
1014
. When a tunnel type GMR (TMR) device is used instead of the GMR device
1014
, a short circuit is likely to occur. Such a problem may be avoided by means of a so-called yoke-type head (not shown). In a conventional yoke-type head, however, a gap needs to be provided between the GMR device
1014
(or the TMR device) and the yoke, e.g., an insulating film or the like is provided in the gap. Such a gap, however, leads to a reduction in reproduced output. As to the recording, the width of a track needs to be on the order of less than a micron (<0.3 &mgr;m) while the film thickness of the magnetic head
1019
is held on the order of microns. This leads to an extraordinarily large aspect ratio and thus difficulty in processing. In the future, the length of a recorded bit in a recording medium is expected to be about 50 nm or less. In a recording medium having such a small bit size, thermal fluctuation must be taken into consideration. When an in-plane recording medium is used as a recording medium
1016
, the coercive force of the recording medium
1016
needs to be significantly large. A recording magnet
1017
of the magnetic head
1019
is required to include a magnetic film having a saturated magnetization of about 2.5 T (tesla) or more so as to magnetize such a recording medium. At the present time, there exists substantially no such magnetic film.
On the other hand, in the magneto-optical head
2020
shown in
FIG. 12
, a recording medium
2016
is heated by laser light condensed by a condenser
2018
up to a temperature such that reversal of magnetization is likely to occur. In addition, a magnetization modulation technique using a magnetic head
2019
is utilized to record information into a bit which is smaller than the wavelength of laser light.
The magneto-optical head
2020
having the above-described structure shown in
FIG. 12
can provide the same level of high-density recording as that of the HDD. Upon reproducing, however, the recorded bit needs to be enlarged up to as much as the wavelength of laser light. To this end, various methods have been proposed, but there still remains challenges insofar as practical use.
In such situations, a new recording/reproducing apparatus
3000
as shown in
FIG. 13
has been proposed. The recording/reproducing apparatus
3000
includes a magneto-optical head
2020
and a GMR head
3019
. Recording is performed using the magneto-optical head
2020
. Reproducing is performed using the GMR head
3019
. That is, two different heads are used for recording and reproducing, respectively. A recording medium
2016
for a magneto-optical disk is used as a recording medium.
On the other hand, in a recording/reproducing apparatus
4000
shown in
FIG. 14
, a magnetic head
1019
for HDD is used. A recording medium
4016
is irradiated by laser light at a side thereof opposite to the magnetic head
1019
. This allows facilitation of reversal of magnetization in recording and facilitation of reading in reproducing.
However, the recording/reproducing apparatus
3000
shown in
FIG. 13
requires two heads for recording and reproducing. There is a problem in that recording and reproducing are performed by the separate heads. Moreover, the recording/reproducing apparatus
4000
shown in
FIG. 14
requires a servo technique to bring laser light to a region recorded on a recording medium. There is a problem in that the higher the density of recording, the greater the technical difficulty. In this case, there is also a significant problem with the processing of the small-width track in the HDD recording head as described above. In both the recording/reproducing apparatuses
3000
and
4000
, the magnetic head and the laser irradiating section need to be provided on the upper and lower sides of the recording medium, respectively. For that reason, it is impossible to provide heads on the upper and lower sides of a disk and utilize both sides of the disk as recording surfaces. In terms of space-saving, such a structure is disadvantageous to the recording/reproducing apparatus.
Further, the magnetic head needs to be moved to a target position on a recording medium for recording or reproducing. In addition to the above-described problems, the higher the density of recording, the greater the difficulty in servo tracking when only one magnetic head driving section is provided in a conventional recording/reproducing apparatus.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a magnetic head for reproducing a signal recorded on a recording medium, includes a substrate; a magnetic head core provided on the substrate, having a magnetic gap; and a first magnetoresistance device provided on the magnetic head core. The magnetic head core is provided in such a manner that a thickness direction of the magnetic head core around the magnetic gap is substantially the same as a track width direction of the recording medium.
In one embodiment of this invention, the magnetic head further includes a second magnetoresistance device provided on the magnetic head core. The first magnetoresistance device and the second magnetoresistance device are provided symmetrically with respect to the magnetic gap.
In one embodiment of this invention, the magnetic head further includes a coil. The coil is provided in such a manner that at least a portion of the magnetic head core is surrounded by the coil; and a signal is recorded onto the recording medium by a magnetic field from the magnetic head core generated by the coil.
In one embodiment of this invention, the first magnetoresistance device includes a first insulating layer provided on the magnetic head core; and a first pinned layer provided on a side opposite to the magnetic head core of the first insulating layer, in which a magnetization direction is not easily rotated in the first pinned layer. The magnetic head core includes a first soft magnetic layer provided at a position corresponding to the first insulating layer; and the first soft magnetic layer functions as a first free layer of the first magnetoresistance device, in which a magnetization direction is easily rotated in the first free layer.
In one embodiment of this invention, the second magnetoresistance device includes a second insulating layer provided on the magnetic head core; and a second pinned layer provided on a side opposite to the magnetic head core of the second insulating layer, in which a magnetization direction is not easily rotated in the second pinned layer. The magnetic head core includes a second soft magnetic layer provided at a position corresponding to the second insulating layer; and the second soft magnetic layer functions as a second free layer of the second magnetoresistance device, in which a magnetization direction is easily rotated in the second free layer.
In one embodiment of this invention, the first soft magnetic
Birukawa Masahiro
Hiramoto Masayoshi
Sakakima Hiroshi
Yokoyama Kazuo
Dinh Tan
Renner Otto Boisselle & Sklar
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