Dynamic magnetic information storage or retrieval – General recording or reproducing – Thermomagnetic recording or transducers
Reexamination Certificate
2001-03-20
2004-02-10
Hudspeth, David (Department: 2697)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Thermomagnetic recording or transducers
C360S321000
Reexamination Certificate
active
06690526
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an information recording and reproducing apparatus which is designed such that a recording medium for retaining information by means of reversed magnetic domains of the magnetic recording film formed on the surface of substrate is employed, that an information is recorded by forming a reversed magnetic domain in the recording medium, and that the information is reproduced by detecting a leaky magnetic flux from the recording medium. The present invention relates also to a magnetic head to be mounted on the information recording and reproducing apparatus.
Due to the recent trend to further increase the recording density of magnetic recording disk drive, the track size of recording bit is now increasingly miniaturized. FIG.
2
(
a
) illustrates a schematic view of a conventional magnetic reproducing head wherein a giant magneto-resistive effect (hereinafter abbreviated as GMR) film is employed as a magnetic sensor. According to this conventional magnetic reproducing head, the GMR film consisting of a laminate comprising a soft-magnetic free layer
203
, a non-magnetic metallic intermediate layer
204
, a ferromagnetic pinned layer
205
and an anti-ferromagnetic layer
206
for fixing the magnetization direction of the ferromagnetic pinned layer
205
is formed on an insulating film
202
which has been formed in advance on a lower shielding film
201
. The GMR film thus formed is then patterned, after which permanent magnets
207
for stabilizing the magnetic properties of the GMR film and electrodes
208
for passing electric current to the GMR film are formed on both sides of this patterned GMR film. The width of track in this case is determined depending on the distance Twr between the electrodes
208
.
As described in a publication, “Proceeding of International Symposium On Future Magnetic Storage”, pages 313-319, a magnetic reproducing head employing a tunneling magneto-resistive effect (hereinafter abbreviated as TMR) film is recently attracting many attentions as an ultra-high sensitive magnetic sensor of the next generation. As shown in FIG.
2
(
b
), this magnetic reproducing head is constructed such that a permanent magnet film
210
for stabilizing the magnetic properties of the TMR film is formed on the surface of a lower electrode
209
and then, patterned. Thereafter, the TMR film consisting of a laminate comprising a soft-magnetic free layer
211
, a non-magnetic insulating intermediate layer
212
, a ferromagnetic pinned layer
213
and an anti-ferromagnetic layer
214
for fixing the magnetization direction of the ferromagnetic pinned layer
213
is formed on the patterned permanent magnet film
210
. Then, after an upper electrode
215
is formed on the TMR film and patterned, an insulating film
216
is formed on both sides of the TMR film. After flattening the surface of the insulating film
216
, additional upper electrode
217
is formed on this flattened surface. The width of track in this case is determined depending on the width Twr between the TMR film.
FIG. 3
illustrates a schematic view of a conventional magnetic recording head. In the case of this magnetic recording head, an upper magnetic core
303
is formed via a gap film
302
on a lower magnetic core
301
, wherein the lower magnetic core
301
is magnetically connected through a back contact
304
with the upper magnetic core
303
. Around this back contact
304
, there is disposed a coil
305
for generating a magnetic flux in a magnetic circuit constituted by the lower magnetic core
301
, the back contact
304
and the upper magnetic core
303
, the magnetic flux being utilized for executing the recording by means of the recording medium. In this case, the tip end
306
of the upper magnetic core
303
is narrowed as shown in
FIG. 3
for the purpose of executing the recording with a narrow track width. The width of track in this case is determined depending on the width Tww of the tip end of the upper magnetic core
303
.
However, if the track size is narrowed as mentioned above, there will be raised various problems that it becomes difficult to execute the patterning of the GMR film itself, and that since the influence of manufacturing error in distance between the permanent magnetic film
207
and the electrode film
208
would become proportionally enlarged, it becomes difficult to manufacture a magnetic reproducing head exhibiting a high precision in track width. Furthermore, the GMR film is now demanded to have an increasingly high sensitivity as the track size is increasingly narrowed. However, according to the aforementioned prior art, since the permanent magnets
207
are disposed on both sides of the GMR film, the magnetization is caused to be fixed on both sides of the GMR film, thereby raising the problem that the sensitivity of the GMR film to a magnetic field is deteriorated.
On the other hand, in the case of the magnetic reproducing head utilizing the TMR film as a magnetic sensor, there is the problem, in addition to the problem that the patterning of the TMR film becomes more difficult as the track size is increasingly narrowed, that since the electric resistance of the sensor is inversely proportional to the area thereof, the electric resistance of the track becomes greater as the track size is narrowed.
Even in the case of the magnetic recording head, the width Tww of the tip end of the upper magnetic core
303
is required to be narrowed still more as the track size is increasingly narrowed. However, as the track size is increasingly narrowed, the recording area of magnetic recording medium is also miniaturized, so that the demagnetization of the magnetic recording medium due to thermal demagnetization thereof becomes a serious problem now. With a view to prevent this demagnetization, measures to enhance the coercive force of magnetic recording medium are now studied. If the coercive force of magnetic recording medium is to be enhanced, a larger recording magnetic field is required to be produced. However, if it is desired to feed a large recording magnetic field from the narrowed upper magnetic core
303
, it is required to make the magnetic core somewhat larger in volume. For this purpose, it is required to manufacture an upper magnetic core having a larger film thickness. However, it is difficult to precisely control the manufacturing error of the width Tww of the tip end of upper magnetic core
303
.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforementioned problems of the prior art, and therefore, an object of the present invention is to provide a magnetic reproducing head and a magnetic recording head, which are easy to manufacture and suited for executing the recording and reproducing by means of magnetic recording medium of narrow track size.
Another object of the present invention is to provide a magnetic recording method and a magnetic reproducing method, which are suited for executing the recording and reproducing by means of magnetic recording medium of narrow track size.
With a view to achieve the aforementioned objects, the present inventors have developed an optical-assisted type magnetic reproducing head and an optical-assisted type magnetic recording head.
Namely, this optical-assisted type magnetic reproducing head is constituted by a GMR or TMR magnetic sensor, and a flux guide for introducing a magnetic flux into the magnetic sensor, wherein at least a portion of the flux guide is constituted by a material which is capable of permitting the magnetic flux to pass therethrough at a temperature of not lower than a predetermined temperature Tp, but not permitting the magnetic flux to pass therethrough at a temperature of lower than Tp. Furthermore, this optical-assisted type magnetic reproducing head is featured in that light is irradiated to only a portion of the flux guide to cause the temperature of the irradiated portion to rise up to Tp or more, thereby permitting a magnetic flux being fed from the magnetic recording medium to pass only through the irradia
Ito Kenchi
Soeya Susumu
Hudspeth David
Rodriguez Glenda P.
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