Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-12-29
2002-12-10
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C029S603080
Reexamination Certificate
active
06493196
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to magnetic storage of information, and particularly to a spin-valve magnetoresistive sensor and a magnetic head having such a spin-valve magnetoresistive sensor.
2. Description of the Related Art
Presently, anisotropic magnetoresistive (AMR) sensors are used extensively for a magnetic head of a hard disk drive (HDD) apparatus. Due to the tendency of increasing recording density of magnetic recording apparatuses, there is a growing need for a magnetic head having a spin-valve magnetoresistive sensor, which provides a sensitivity superior to an AMR sensor.
FIG. 1
is a partially cut-away perspective diagram of a composite magnetic head
130
including the spin-valve magnetoresistive head
100
of the related art. The composite magnetic head
130
incorporates the spin-valve magnetoresistive head
100
as a reading (reproducing) head of the hard disk drive apparatus and also incorporates a writing (recording) head.
FIG. 1
also shows a hard disk
27
as a recording medium. In the figure, the hard disk
27
is arranged so as to oppose the composite magnetic head
130
. The basic structure of the composite magnetic head
130
is substantially the same as the structure of the composite magnetic head
30
of the present invention. Therefore, further detailed description is omitted here. The structure of the composite magnetic head
130
of the related art can be understood when reading the detailed description of
FIG. 8
by replacing the spin-valve magnetoresistive head
10
with the spin-valve magnetoresistive head
100
of the related art.
FIG. 2
is a partially cut-away perspective view showing a spin-valve magnetoresistive head
100
using a spin-valve magnetoresistive sensor of the related art. Further,
FIG. 3
is a side view showing the spin-valve magnetoresistive head
100
of FIG.
2
. In the following, the spin-valve magnetoresistive head
100
will be described in detail with reference to
FIGS. 2 and 3
.
The spin-valve magnetoresistive head
100
includes a lowermost underlayer
111
of tantalum (Ta) and an uppermost capping layer
116
also of Ta, and a spin-valve magnetoresistive sensor is interposed between the underlayer
111
and the capping layer
116
. The spin-valve magnetoresistive sensor (or film) includes a free layer
112
of a ferromagnetic material, a non-magnetic layer
113
of a non-magnetic conductive material such as copper (Cu), a pinned magnetic layer
114
of a ferromagnetic material such as a cobalt-iron-boron (CoFeB) alloy, and a pinning layer
115
of an anti-ferromagnetic material, which may be formed of an ordered alloy made of palladium-platinum-manganese (PdPtMn), in the state that the layers
112
-
115
are stacked consecutively on the underlayer
111
. The free layer
112
typically includes a first ferromagnetic layer
112
a
of nickel-iron (NiFe) provided on the underlayer
111
and a second ferromagnetic layer
112
b
of a cobalt-iron-boron (CoFeB) alloy provided on the first ferromagnetic layer
112
a.
In this context, the ordered alloy used for the pinning layer
115
is understood as an anti-ferromagnetic alloy which does not exhibit magnetism when initially formed as the anti-ferromagnetic layer
115
. On the other hand, the ordered alloy exhibits a stable magnetization when its magnetization is aligned as a result of magnetizing process conducted under a suitable condition.
The above-described spin-valve magnetoresistive head is manufactured first by providing the underlayer and then providing other layers described above in the order shown in
FIGS. 2 and 3
. Then, all the layers including the spin-valve magnetoresistive sensor are patterned to form a rectangular body, and electrode terminals
117
a,
117
b
of a metal such as gold (Au) are provided on the uppermost capping layer
116
with a mutual separation from each other.
In the spin-valve magnetoresistive head
100
of
FIG. 3
, the area between the electrodes
117
a
and
117
b
and designated as S serves as the signal sensing area of the spin-valve magnetoresistive sensor. In the following text, X-, Y-, and Z-directions are defined as follows in order to make a clear explanation of, for example, the magnetizing direction of the spin-valve magnetoresistive sensor of the spin-valve magnetoresistive head
100
. Thus, the Z-direction is defined as a direction of the thickness of the spin-valve magnetoresistive sensor. The Y-direction is a direction perpendicular to the Z-direction. It should be noted that the foregoing electrodes
117
a
and
117
b
are provided at the respective opposite ends of the rectangular body forming the spin-valve magnetoresistive sensor in the cross-sectional view taken in the Y-direction. The X-direction (the height) is a direction perpendicular to the Y-Z plane.
In the following text, it is assumed that the magnetization of the free layer
112
points in the Y-direction in the state where there is no external magnetic field applied to the free layer
112
. In other words, the free layer
112
has an easy axis of magnetization pointing in the Y-direction. Also, a term “orientation” is understood to mean a predetermined direction, which may be shown by an arrow in the figures. A term “direction” can imply both opposite orientations having positive and negative signs.
During the operation of the spin-valve magnetoresistive head
100
of the related art, a sense current Is is caused to flow through the signal sensing region S between the two electrode terminals
117
a,
117
b,
and the spin-valve magnetoresistive head
100
is caused to scan over a magnetic recording medium (not shown) such as a magnetic disk. Then, the electric resistance of the spin-valve magnetoresistive sensor changes in response to a signal magnetic field Hsig originating from the magnetic recording medium in the X-direction. Thus, the signal magnetic field of the magnetic recording medium can be detected as a change of the voltage appearing across the electrodes
117
a
and
117
b.
With such a spin-valve magnetoresistive head
100
, it is preferable that the resistance of the spin-valve magnetoresistive sensor changes linearly with respect to direction of the signal magnetic field Hsig such that the resistance increases when the signal magnetic field Hsig has a first orientation and such that the resistance decreases when the signal magnetic field Hsig has a second, opposite orientation It should be noted that the resistance of the spin-valve magnetoresistive sensor becomes minimum when the magnetization Mf of the free layer
112
and the magnetization Mp of the pinned magnetic layer
114
are parallel and becomes maximum when the magnetization Mf of the layer
112
and the magnetization Mp of the layer
114
are anti-parallel. In order to achieve this, the direction of magnetization Mp of the pinned magnetic layer
114
is pinned in the X-direction by establishing an exchange coupling between the pinned magnetic layer
114
and the anti-ferromagnetic layer
115
. Then, when the signal magnetic field Hsig is zero, the direction of magnetization Mf of the free layer
112
points in the Y-direction as stated above.
Now, due to the increase in the recording density of the information recorded on a recording medium such as a hard disk, there is a tendency that the size of the individual magnetic spots formed on the magnetic disk becomes smaller and smaller, and because of this, the signal magnetic field Hsig which the spin-valve magnetoresistive head
100
is supposed to pick up tends to become very weak. In order to compensate for the weakening of the signal magnetic field Hsig, it is necessary to increase the magnetic resistance ratio (MR-ratio) &Dgr; &rgr;/&rgr; to obtain a larger signal or S/N ratio. In order to achieve this, either the thickness (Z-direction) or the height of the sensor (X-direction) of the spin-valve magnetoresistive sensor has to be reduced.
Firstly, a process of reducing the thickness (Z-direction) is considered. The layer having the greatest thickness in the spin
Aoshima Ken-ichi
Kanai Hitoshi
Kane Junichi
Noma Kenji
Fujitsu Ltd.
Greer Burns & Crain Ltd.
Klimowicz William
LandOfFree
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