Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-05-31
2003-08-12
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06606225
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic head and a magnetic recording/reproduction device, and, more specifically, to a magnetic head and a magnetic recording/reproduction device wherein Barkhausen noise is suppressed and high-density recording is enabled.
It is expected that magnetic recording/reproduction devices, such as hard disk drives (HDDs), will achieve even greater densities in the future as the recent trends towards smaller sizes and higher densities proceeds. To increase densities in magnetic recording, it is necessary to increase the recording track density by narrowing the “recording track width” and also to increase the recording density in the longitudinal direction, in other words, the “linear recording density.”
To ensure that a sufficiently large reproduction signal output is obtained even when the recording track width has been reduced and also the magnitude of the magnetization used for recording has been reduced, the anisotropic magneto-resistance effect (AMR) is utilized to develop AMR heads, which have high reproduction sensitivity and are now in use. Giant magneto-resistance (GMR) has recently been utilized to develop even more sensitive spin-valve GMR heads for use, which has been realized to enable even higher reproduction sensitivities. Research is also progressing into magnetic heads that utilize tunnelling magneto-resistance (TMR).
The development and use of magnetic heads with such high levels of reproduction sensitivity has made it possible to reproduce recording signals even from extremely narrow recording track widths.
However, in order to increase the linear recording density, which is the density in the longitudinal direction of a recording track, it is necessary to reduce the gap of the magnetic head. In a prior-art magnetic head that uses a magneto-resistance effect element, a magneto-resistance effect element is inserted within a head gap. The thickness of the magneto-resistance effect element must be 20-30 nm, even with an AMR head or a spin-valve GMR head, and it is necessary to provide a distance of about 100 nm between the two shields, from consideration of insulation between the sensing element and the shields. This means that there is a large limitation on increases in linear recording density.
This problem can be solved by using a structure called a “magnetic yoke.”
A schematic view of the structure of a yoke-type magnetic head is shown in FIG.
22
. This yoke-type magnetic head has a pair of magnetic yokes
202
with a magnetic field detection sensor
204
connected therebetween. A gap
206
is provided in the close vicinity of the ends of the magnetic yokes
202
. A magneto-resistance effect element can be used as the magnetic field detection sensor
204
, by way of example.
In other words, the magneto-resistance effect element
204
is moved away from the gap
206
of the magnetic head to make it possible to ensure that the head gap is sufficiently narrow. The signal flux F from the recording medium is taken in by the head gap portion and is guided by the magnetic yokes
202
, then is transferred to the magneto-resistance effect element
204
that is located at a rear portion of the magnetic head, so that the reproduction signal can be obtained from this magneto-resistance effect element
204
.
Since this yoke-type magnetic head makes it possible to ensure that the head gap is sufficiently small, it is possible to increase the resolution of reproduction and thus respond to a high linear recording density. With respect to track density, the reproduction track width in the prior-art device is determined by the spacing of leads disposed on either the of the magneto-resistance effect element
204
, to supply a sense current thereto, but with a yoke-type device it is possible to determine the track width by the film thickness of the magnetic yokes
202
and thus it is simpler to reduce the track width than in the prior-art device. This feature is another reason why the yoke-type magnetic head can be expected to enable sufficient respond to higher recording densities in the future.
With a yoke-type magnetic head, however, the magnetic domain walls within the magnetic material used for the magnetic yokes
202
move discontinuously. As a result, the transfer of magnetic flux is passed on to the magneto-resistance effect element
204
in a discontinuous manner, which therefore leads to large amounts of Barkhausen noise in the reproduction output from the magneto-resistance effect element
204
. This noise is so great, it creates a large obstacle to the implementation of a magnetic head using such magnetic yokes
202
.
With a magnetic head that uses the magnetic field detection sensor
204
, it is necessary to supply a sense current to the magnetic field detection sensor
204
. However, with a yoke-type device, the flow of this sense current tends to shunt into the magnetic yokes
202
from the magnetic field detection sensor
204
, leading to a deterioration in sensitivity. If an insulating film of a material such as alumina is disposed between the magnetic yokes
202
and the magnetic field detection sensor
204
in order to prevent this, the “propagation” of magnetic flux through that portion will worsen, which causes a problem in that the same sort of deterioration insensitivity occurs.
As described above, the yoke-type magnetic head of the prior art has problems in that Barkhausen noise is generated by discontinuous movement of the magnetic domain walls in the magnetic yokes
202
, and sensitivity deteriorates, either due to the worsening of the “propagation” of magnetic flux between the magnetic yokes
202
and the magnetic field detection sensor
204
or due to shunting of the flow of sense current.
The present invention was devised in recognition of these technical problems. In other words, an objective of this invention is to provide a magnetic head and a magnetic recording/reproduction device that uses the same, wherein the generation of Barkhausen noise is suppressed while, at the same time, there is no deterioration of sensitivity.
SUMMARY OF THE INVENTION
In other words, a magnetic head in accordance with the present invention comprises:
a magnetic yoke taking in a signal flux from a magnetic recording medium, the magnetic yoke having a first yoke member, a second yoke member and a magnetic gap, the magnetic gap being located between the first and second yoke members; and
a magneto-resistance effect element detecting the signal flux transferred from the magnetic yoke,
wherein the signal flux is transferred to the magneto-resistance effect element via a granular magnetic film.
In this case, a “granular magnetic film” is a thin film of a material that has a granular structure wherein minute magnetic metal particles are surrounded by a material having non-magnetic properties.
Another magnetic head in accordance with the present invention relates to a magnetic head comprising:
a magnetic yoke taking in a signal flux from a magnetic recording medium, the magnetic yoke having a first yoke member, a second yoke member and a magnetic gap, the magnetic gap being located between the first and second yoke members; and
a magneto-resistance effect element detecting the signal flux transferred from the magnetic yoke,
wherein the first and second yoke members have a plurality of magnetic domains, each of the magnetic domains having a main magnetization direction parallel or antiparallel to a first direction.
A preferred embodiment of the present invention is provided with magnetic yokes having a magnetic gap interposed therebetween on a medium-facing surface thereof, and a magneto-resistance effect element formed at a position that is a predetermined distance further backward than the medium-facing surface, wherein the magnetic yokes comprise a granular magnetic film or a granular magnetic film is interposed between the magnetic yokes and the magneto-resistance effect element.
The “medium-facing surface” corresponds to the “air-bearing surface” if the magnetic head is of a “floating sliding” type, and corresp
Funayama Tomomi
Osawa Yuichi
Yoda Hiroaki
Yoshikawa Masatoshi
Davis David
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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