Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-10-04
2003-11-04
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S324120, C360S322000
Reexamination Certificate
active
06643107
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to a spin valve thin film magnetic element in which electric resistance changes with the relation between the pinned magnetization direction of a pinned magnetic layer and the magnetization direction of a free magnetic layer affected by an external magnetic field, a method of manufacturing the spin valve thin film magnetic element, and a thin film magnetic head comprising the spin valve thin film magnetic element. Particularly, the invention relates to a technique suitable for a spin valve thin film magnetic element capable of decreasing asymmetry and the occurrence of Barkhausen noise, improving the stability of the element, and permitting sufficient control of the magnetic domain of a free magnetic layer.
2. Description of the Related Art
A spin valve thin film element is a GMR (giant magnetoresistive) element exhibiting a giant magnetoresistive effect, and usually is adapted to detect a recording magnetic field from a recording medium such as a hard disk or the like.
As a GMR element, the spin valve thin film magnetic element has a relatively simple structure, excellent properties of a high rate of change in resistance with an external magnetic field, and a change in resistance with a weak magnetic field.
FIG. 29
is a sectional view illustrating the structure of an example of a conventional spin valve thin film element, as viewed from the air bearing surface (ABS) facing a recording medium.
The spin valve thin film magnetic element shown in
FIG. 29
is a bottom-type single spin valve thin film element comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer.
In the spin valve thin film element, the moving direction of a magnetic recording medium such as hard disk coincides with the Z direction shown in FIG.
29
. The direction of a leakage magnetic field from the magnetic recording medium coincides with the Y direction.
The conventional spin valve thin film element shown in
FIG. 29
has a lamination
109
comprising a base layer
106
, an antiferromagnetic layer
101
, a pinned magnetic layer
102
, a nonmagnetic conductive layer
103
, a free magnetic layer
104
, and a protecting layer
107
, which are laminated in turn on a substrate. The conventional spin valve thin film element also has a pair of hard bias layers
105
formed on both sides of the lamination
109
and a pair of electrode layers
108
respectively formed on the hard bias layers
105
.
The base layer
106
is made of Ta (tantalum). The antiferromagnetic layer
101
is made of a NiO (nickel oxide) alloy, a FeMn (ferro-manganese) alloy, a NiMn (nickel manganese) alloy, or the like. Each of the pinned magnetic layer
102
and the free magnetic layer
104
is made of Co (colbalt), a NiFe (nickel iron) alloy, or the like. The nonmagnetic conductive layer
103
comprises a Cu (copper) film. Each of the hard bias layers
105
is made of Co—Pt (cobalt-platinum) alloy. Each of the electrode layers
108
is made of Cu or the like.
The pinned magnetic layer
102
is formed in contact with the antiferromagnetic layer
101
to produce an exchange coupling magnetic field (exchange anisotropic magnetic field) in the interface between the pinned magnetic layer
102
and the antiferromagnetic layer
101
. The pinned magnetization of the pinned magnetic layer
102
is pinned in the Y direction shown in the drawing.
The hard bias layers
105
are magnetized in the X
1
direction shown in the drawing to orient variable magnetization of the free magnetic layer
104
in the X
1
direction. As a result, the variable magnetization of the free magnetic layer
104
crosses the pinned magnetization of the pinned magnetic layer
102
.
The electrode layers
108
respectively comprise overlay portions
108
a
, which extend to the portions of the lamination
109
outside the sensing track width Tw. The overlay portions
108
a
may solve the problem of decreasing reproduced output due to dead regions formed near both edges of the lamination
109
.
In the spin valve thin film element, a sensing current is supplied to the pinned magnetic layer
102
, the nonmagnetic conductive layer
103
, and the free magnetic layer
104
from the electrode layers
108
formed on the hard bias layers
105
. The moving direction of the magnetic recording medium such as a hard disk coincides with the Z direction shown in the drawing. When a leakage magnetic field from the magnetic recording medium is applied in the Y direction, magnetization of the free magnetic layer
104
is changed from the X
1
direction to the Y direction. The electric resistance value changes with the relation between the change in the magnetization direction of the free magnetic layer
104
and the pinned magnetization direction of the pinned magnetic layer
102
. This is referred to as “magnetoresistive (MR) effect”. The leakage magnetic field from the magnetic recording medium is detected by a change in voltage based on the change in the electric resistance value.
The central portion of the lamination
109
, except the overlay portions
108
a
, substantially contributes to reproduction of the recording magnetic field from the magnetic recording medium. The control portion comprises a sensitive region exhibiting the magnetoresistive effect, and defines the sensing track width Tw. The both-side regions below the overlay portions
108
a
are the dead regions, which substantially do not contribute to reproduction of the recording magnetic field from the magnetic recording medium.
In the spin valve thin film element, the asymmetry of output is desired to be as small as possible and is defined by the relation between the variable magnetization direction of the free magnetic layer
104
and the pinned magnetization direction of the pinned magnetic layer
102
. Therefore, the relation between the variable magnetization of the free magnetic layer
104
and the pinned magnetization of the pinned magnetic layer
102
is desired to be as close to 90° as possible, and in theory 90°.
The variable magnetization direction of the free magnetic layer
104
that affects the asymmetry of output is described below based on the drawings.
FIG. 30
is a schematic drawing illustrating a state in which the direction of variable magnetization M
f
of the free magnetic layer
104
is defined.
The magnetic fields that influence the direction of variable magnetization M
f
of the free magnetic layer
104
include three magnetic fields—a sensing current magnetic field H
j
due to a sensing current J, a demagnetizing (dipole) magnetic field H
d
due to the pinned magnetization of the pinned magnetic layer
102
, and an interaction magnetic field H
int
due to the layer interaction between the free magnetic layer
104
and the pinned magnetic layer
102
.
When these magnetic fields contribute less to the variable magnetization M
f
of the free magnetic field
104
, asymmetry is decreased. In order to decrease asymmetry, when no external magnetic field is applied, the following condition is satisfied.
H
j
+H
d
+H
int
=0
With the spin valve thin film element not operating, i.e., with no sensing current J supplied, no sensing current magnetic field H
j
occurs. In this state, the direction of the variable magnetization M
f
of the free magnetic layer
104
is oriented by the magnetic field of the hard bias layers
105
. With no sensing current J supplied, the variable magnetization M
f
of the free magnetic layer
104
defined by the hard bias layers
105
does not cross perpendicularly to the pinned magnetization M
p
of the pinned magnetic layer
102
. Therefore, a setting is performed in anticipation of contribution of the sensing current J so that these magnetization directions do not cross each other at right angles unless the sensing current J flows.
With no sensing current J supplied, no sensing current magnetic field H
j
is produced and the variable magnetization M
f
of the free magnetic field
104
tends to be opposite to the pinned mag
Hasegawa Naoya
Honda Kenji
Sato Kiyoshi
Alps Electric Co. ,Ltd.
Evans Jefferson
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