Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-03-16
2001-12-25
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S046000
Reexamination Certificate
active
06333840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording apparatus using a magnetoresistance reproducing head.
2. Description of the Related Art
An MR head using magnetoresistance (MagnetoResistance; hereinafter referred to as MR) is expected as one which can be used for a high density magnetic recording apparatus. The MR head has such a structure that upper and lower magnetic shielding films are disposed above and below a magnetoresistance element through magnetic gap films, respectively. The MR head is stacked with an induction type recording head using the upper magnetic shielding film as its lower recording magnetic pole, and this stacked head is known as a recording/reproduction composite magnetic head.
FIG. 15
is a side view of a medium facing surface: ABS (Air Baring Surface), which shows the structure of a conventional recording/reproduction composite magnetic head. As shown in
FIG. 15
, an MR film
4
is formed through a lower magnetic gap film
3
of an alumina film or the like on a lower magnetic shielding film
2
of CoZrNb amorphous alloy, or the like, formed on a substrate
1
of altic (A
1
2
O
3
. TiC) with alumina.
The MR film
4
is patterned in stripe shape, and as shown in
FIG. 15
, a pair of lead electrodes
5
are connected to both ends thereof. The lead electrodes
5
are made of good conductive films with a thickness of about 100 nm. As shown in
FIG. 15
, an upper magnetic shielding film
8
is formed through an upper magnetic gap film
7
on an MR element
6
including the MR film
4
and the lead electrodes
5
. A reproducing MR head
9
is constituted by the MR element
6
, the upper and lower gap films
3
and
7
, and the upper and lower magnetic shielding films
2
and
8
.
An induction type recording head
10
includes, as shown in
FIG. 15
, a recording magnetic pole serving also as the upper magnetic shielding film
8
, a recording magnetic gap film
11
made of an alumina film or the like, and an upper recording magnetic pole
12
, and further includes a recording coil (not shown) for applying a recording magnetic field to the recording magnetic poles
8
and
12
at the rear of the ABS.
The increase of recording density of a magnetic recording apparatus, such as a HDD, has been achieved by narrowing a track, narrowing a gap, shortening a bit length of a recording signal, or the like. For example, for the purpose of achieving the high recording density such as 4 Gbpsi (Giga-bits/inch
2
), in addition to shortening of a track width, it is necessary to shorten a bit length by making a reproducing gap length between the upper and lower magnetic shielding films
2
and
8
(distance from the film thickness center of the magnetic field detecting film to the upper and lower magnetic shielding films) to have a length of about 160 nm. For the purpose of achieving such a narrow gap, it is necessary to provide stable insulation coating on the lead electrodes
5
having a thickness of about 100 nm while using the thin upper magnetic gap film
7
having a thickness of about 60 nm at one side.
In the present film forming technique, it is difficult to achieve high recording density such as 10 Gbpsi or more and to secure excellent insulation between the lead electrodes
5
and the upper magnetic shielding film
8
.
In addition, the width of an isolated reproduction signal as an index of a reproduction resolution is 280 nm even in the present level of about 4 Gbpsi, and its fluctuation is about 70 nm. For such a width of an isolated reproduction wave output, a desirable gap length becomes almost zero.
On the other hand, Japanese Patent Unexamined Publication No. Hei. 9-138918 discloses an MR head in which an operation point is adjusted by making upper and lower gap lengths different from each other.
As described above, in a conventional magnetic recording apparatus, it becomes difficult to realize a gap length meeting a high recording density system such as 10 Gbpsi or more.
SUMMARY OF THE INVENTION
The present invention has been made to solve such problems, and an object of the invention is to provide a magnetic recording apparatus which meets the increase of recording density and can perform signal reproduction with high accuracy while using an MR head with upper and lower gap lengths different from each other.
In order to solve the foregoing problems, according to a first aspect of the invention, a magnetic recording apparatus comprises a magnetic recording medium having a plurality of recording bits; a magnetoresistance head for detecting a signal magnetic field from the magnetic recording medium, the magnetoresistance head including a magnetic field detecting film, and upper and lower magnetic shielding films provided above and below the magnetic field detecting film through upper and lower magnetic gap films, a distance between the upper magnetic shielding film and a film thickness center of the magnetic field detecting film being different from a distance between the lower magnetic shielding film and the film center; and a signal processing circuit for processing an electric signal from the magnetoresistance head, the signal processing circuit obtaining a reproduction signal of a present bit by subtracting a correction value obtained by multiplying a signal value of a bit prior to the present bit by a predetermined coefficient from a signal value of the bit as a present identification object.
Moreover, in order to solve the foregoing problems, according to a second aspect of the invention, a magnetic recording apparatus comprises a magnetic recording medium with a plurality of recording bits; a magnetoresistance head for detecting a signal magnetic field from the magnetic recording medium, the magnetoresistance head including a magnetic field detecting film, and upper and lower magnetic shielding films provided above and below the magnetic field detecting film through upper and lower magnetic gap films, a distance between the upper magnetic shielding film and a film thickness center of the magnetic field detecting film being different from a distance between the lower magnetic shielding film and the film thickness center; and a signal processing circuit for processing an electric signal from the magnetoresistance head, the signal processing circuit using a partial response system.
The first and second aspects of the invention adopt the magnetoresistance head using the upper and lower magnetic gap films which have the distances from the film thickness center of the magnetic field detecting film being different from each other, so that it is possible to control the increase of an S/N ratio due to an inflow magnetic field from another bit adjacent to the present bit.
That is, since the magnetoresistance head of each of the first and second aspects of the invention has asymmetric gaps, that is, the upper and lower magnetic gap films having the distances from the film thickness center of the magnetic field detecting film being different from each other. Thus, at a wider gap side, that is, at a side where the distance from the film thickness center of the magnetic field detecting film is farther between the upper and lower magnetic shielding films, the inflow magnetic field from the adjacent bit is added, as a noise component, to a signal magnetic field from the present bit, so that the electric signal of the magnetoresistance head detecting this is degraded in S/N ratio, unlike actual recorded information of the present bit, which has been clarified by diligent studies of the present inventors. The magnetic recording apparatus of each of the first and second aspects of the invention adopts the signal processing circuit capable of suppressing the noise component, so that it becomes possible to obtain a reproduction signal with a high S/N ratio.
A recording bit length is fitted to the narrow gap positioned at the opposite side to the wide gap side of the magnetoresistance head of each of the first and second aspects of the invention, and signal reproduction with high density in a track length direction c
Kobayashi Tadahiko
Sakata Hiromi
Tateyama Kohichi
Yoda Hiroaki
Davidson Dan I.
Hudspeth David
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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