Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-04-04
2004-04-13
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S324200
Reexamination Certificate
active
06721147
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetoresistance effect magnetic head that uses a magnetoresistance effect element. More particularly, the invention relates to a magnetoresistance effect magnetic head in which a sense current flows in a direction perpendicular to the surface of the magnetoresistance effect element and accurately reproduces the signal magnetic field from a magnetic recording medium.
FIG. 1
shows a well-known magnetoresistance effect magnetic head
100
(hereinafter called the magnetic head). The magnetic head
100
is shown in cross-section as viewed from a magnetic recording medium (not shown). A magnetoresistance effect element
101
for sensing a signal magnetic field from the magnetic recording medium, such as a hard disk, is shown in the center portion of the magnetic head
100
in
FIG. 1. A
well-known magnetoresistance effect (MR) element
101
is a spin valve magnetoresistance effect (SVMR) element. This spin valve magnetoresistance effect element
101
is typically formed from multiple deposited thin-film layers including a first magnetic layer, a nonmagnetic layer, a second magnetic layer, and an antiferromagnetic layer (not shown).
The magnetoresistance effect element
101
has ends
101
A,
101
B connected to electrically conductive lead terminals
102
A,
102
B. The magnetoresistance effect element
101
, the lead terminals
102
A,
102
B, and hard films
103
A,
103
B are electrically insulated on both upper and lower sides by an electrically insulating upper gap material
104
and a lower gap material
105
. A top
104
A of the upper gap material
104
and a bottom
105
A of the lower gap material
105
are shielded by respective soft magnetic shields
106
,
107
.
Recently, there has been considerable demand for higher density recording in magnetic recording/reproducing equipment. To increase the sensitivity of the magnetic head
100
to detect information (signal magnetic field) magnetically recorded at high densities, the width of the gap W
1
between the shields
106
,
107
was narrowed and the film thickness of the entire magnetic head
100
was thinned. However, the gap materials
104
,
105
must maintain a minimum film thickness to maintain insulating characteristics, and forming thinner gap materials
104
,
105
is difficult and costly.
Referring to
FIG. 2
, a known magnetic head
200
further narrows a gap width W
2
without narrowing the gap material, as disclosed in unexamined Patent Publication (Kokai) No H 9-28807. In the magnetic head
200
, also viewed from a magnetic recording medium (not shown), a magnetoresistance effect element
201
is electrically connected to an upper shield
206
and a lower shield
207
that also function as lead terminals. This configuration eliminates the need for a gap material
204
between the shield
206
and electrically insulating film
202
A, and between the shield
206
and electrically insulating film
202
B, and also eliminates the need for gap material
205
between the shield
207
and hard film
209
A, and between the shield
207
and hard film
209
B, to thereby further narrow the gap width W
2
. This enables a narrower gap to be fabricated.
The upper and lower gap materials
204
,
205
, placed above and below a magnetoresistance effect element
201
, are formed from electrically conductive materials. The electrically insulating films
202
A,
202
B are provided on ends
201
A,
201
B of the magnetoresistance effect element
201
.
Referring to
FIGS. 1-2
, the flow direction of a sense current for magnetic head
100
is different from the flow direction of a sense current for magnetic head
200
. In the magnetic head
100
, a sense current flows from the lead terminal
102
A through the magnetoresistance effect element
101
to the lead terminal
102
B (or in the reverse direction) in a direction parallel to a generally planar surface
108
of element
101
(only shown in cross-section) hereinafter “planar direction”. In the magnetic head
200
, a sense current flows from the upper shield
206
through the magnetoresistance effect element
201
to the lower shield
207
(or in the reverse direction) in a direction perpendicular to a surface
208
of the element
201
, hereinafter “perpendicular direction”. The magnetic head
100
, in which a sense current flows in the planar direction, is called a CIP (current in plane) magnetic head. The magnetic head
200
, in which a sense current flows in the perpendicular direction, is called a CPP (current perpendicular to plane) magnetic head.
Since a sense current in the CIP magnetic head
100
described above flows in the plane of the MR element, this head cannot use an MR element, for example, that requires a sense current to flow in a direction perpendicular to the plane of the MR element, as in a tunnel magnetoresistance effect (TMR) element. In contrast, magnetic heads using CPP are expected to become popular because of the ability to use a TMR element and to narrow the gap W
2
as described above. However, the magnetic head
200
leaks current at both ends
201
A,
201
B of the magnetoresistance effect element
201
, and therefore has difficulty in producing an efficient flow in the perpendicular direction.
To control the magnetic domain of the magnetoresistance effect element
201
, it has been proposed that hard films
209
A,
209
B be formed on both ends
201
A,
201
B of the magnetoresistance effect element
201
for applying a longitudinal bias magnetic field. In this case, however, if the hard films
209
A,
209
B are electrically conductive materials such as CoPt or CoCrPt, electrical shorts develop with the upper gap material
204
, the current usage rate decreases markedly, and adequate magnetoresistance effect cannot be obtained, which in turn lowers manufacturing yield.
To prevent shorts and current leakage, it has also been proposed that an electrically insulating film, such as alumina, be inserted between the ends
201
A,
201
B of the magnetoresistance effect element
201
and the hard films
209
A,
209
B, but even with the use of alumina it is difficult to maintain sufficient electrical insulation. Also, since the magnetoresistance effect element is then magnetically separated from the hard film by the alumina, the longitudinal bias magnetic field applied to the magnetoresistance effect element decays, giving rise to problems of unsatisfactory magnetic domain control and noise generation.
Thus, a main object of the present invention is to provide an improved magnetoresistance effect magnetic head that does not have substantial leakage of current at the ends of the magnetoresistance effect element.
Another object of the present invention is to provide an improved magnetoresistance effect magnetic head capable of applying a sufficiently stable longitudinal bias magnetic field to the magnetoresistance effect element.
Yet another object of the present invention is to provide an improved magnetic recording/reproducing apparatus with the improved magnetic head.
SUMMARY OF THE INVENTION
In accordance with the present invention, a magnetoresistance effect magnetic head has an insulating antiferromagnetic layer placed next to ends of a magnetoresistance element to suppress leakage currents at the ends of the magnetoresistance effect element. A magnetic layer is placed in contact with the antiferromagnetic layer, so that exchange coupling generates a unidirectional anisotropic magnetic field that is applied as a stable longitudinal bias magnetic field to the magnetoresistance effect element. In this manner, a signal magnetic field from a recording medium can efficiently be detected using the magnetoresistance effect without encountering problems such as Barkhausen noise, and an efficient flow of a sense current occurs through the magnetoresistance effect element.
In one aspect of the present invention, a magnetoresistance effect magnetic head has a biasing portion at ends of a magnetoresistance effect element for applying a longitudinal bias magnetic field to the magnetoresistance effect element. T
Aoshima Ken-ichi
Ito Jun-ichi
Noma Kenji
Evans Jefferson
Fujitsu Limited
Greer Burns & Crain Ltd.
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