Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-11-30
2003-10-21
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S690000, C428S690000, C428S900000, C360S112000, C338S03200R, C338S03200R, C324S252000
Reexamination Certificate
active
06635366
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to spin valve thin film magnetic elements and thin film magnetic heads. In particular, the present invention relates to spin valve thin film magnetic elements in which shunt losses of sensing currents are reduced and rates of change in magnetoresistance are increased.
2. Description of the Related Art
Among magnetoresistive effect type magnetic heads, there are MR (Magnetoresistive) heads, providing an element showing a magnetoresistive effect, and GMR (Giant Magnetoresistive) heads, providing an element showing a giant magnetoresistive effect. In the MR head, the element showing a magnetoresistive effect is made to have a single-layer structure made of magnetic materials. On the other hand, in the GMR head, the element showing a magnetoresistive effect is made to have a multi-layer structure composed of laminated plural materials. There are several kinds of structures generating giant magnetoresistive effects, and the spin valve thin film magnetic element is the one having a relatively simple structure, and having a high rate of change in resistance to an external magnetic field.
Recently, requirements for further increase in the magnetic recording density have been even more intensified, and the spin valve thin film magnetic elements, which have the potential to fulfill further demands for increases in magnetic recording density, have attracted great amounts of attention.
Next, a conventional spin valve thin film magnetic element is explained referring to the drawings.
FIG. 15
is a schematic sectional view of a conventional spin valve thin film magnetic element
101
viewed from a magnetic recording medium side.
FIG. 16
is a schematic sectional view of the spin valve thin film magnetic element
101
viewed from a track width direction.
On the top and bottom of the spin valve thin film magnetic element
101
, shield layers are formed via gap layers, and a reproducing thin film magnetic head is composed of the spin valve thin film magnetic element
101
, gap layers, and shield layers. A recording inductive head may be laminated on said thin film magnetic head.
The thin film magnetic head is provided on an end portion of a trailing side of a floating slider, etc., together with an inductive head, to constitute a thin film magnetic head, and to detect recording magnetic fields of magnetic recording media such as hard disks.
In
FIGS. 15 and 16
, the Z direction shown in the drawings is a moving direction of the magnetic recording medium, the Y direction shown in the drawings is a direction of a leakage magnetic field from the magnetic recording medium, and the X
1
direction shown in the drawings is a direction of the track width of the spin valve thin film magnetic element
101
.
The spin valve thin film magnetic element
101
, shown in FIG.
15
and
FIG. 16
, is a bottom type single spin valve thin film magnetic element constituted by orderly laminating an antiferromagnetic layer
103
, a pinned magnetic layer
104
, a nonmagnetic conductive layer
105
, and a free magnetic layer
111
.
In FIG.
15
and
FIG. 16
, the numeral
100
shows an insulating layer formed from Al
2
O
3
, etc., and the numeral
102
shows a substrate layer made of Ta, etc., laminated on the insulating layer
100
. The antiferromagnetic layer
103
, the pinned magnetic layer
104
, the nonmagnetic conductive layer
105
formed from Cu, etc., and the free magnetic layer
111
are laminated in order on the substrate layer
102
, and a cap layer
120
formed from Ta, etc., is laminated on the free magnetic layer
111
.
Thus, each layer from the substrate layer
102
to the cap layer
120
is laminated in order to constitute a laminate
121
having a width meeting the track width, and having a sectional view of nearly trapezoidal shape.
The pinned magnetic layer
104
formed from, for example, Co, is laminated in contact with the antiferromagnetic layer
103
, and an exchange coupling magnetic field (an exchange anisotropic magnetic field) is generated on the boundary of the antiferromagnetic layer
103
and the pinned magnetic layer
104
; then, the direction of magnetization of the pinned magnetic layer
104
is pinned in the Y direction shown in the drawings.
The free magnetic layer
111
is composed of a nonmagnetic intermediate layer
109
, and the first free magnetic layer
110
and the second free magnetic layer
108
holding said nonmagnetic intermediate layer between these. The first free magnetic layer
110
is provided on the cap layer
120
side of the nonmagnetic intermediate layer
109
, and the second free magnetic layer
108
is provided on the nonmagnetic conductive layer
105
side of the nonmagnetic intermediate layer
109
. The thickness t
1
of the first free magnetic layer
110
is slightly greater than the thickness t
2
of the second free magnetic layer
108
.
The first free magnetic layer
110
is formed from a ferromagnetic material such as a NiFe alloy, and the nonmagnetic intermediate layer
109
is formed from a nonmagnetic material such as Ru.
The second free magnetic layer
108
is composed of a diffusion preventing layer
106
and a ferromagnetic layer
107
. The diffusion preventing layer
106
and the ferromagnetic layer
107
are both made of ferromagnetic materials, the diffusion preventing layer
106
is formed from, for example, Co, and the ferromagnetic layer
107
is formed from the NiFe alloy. The first free magnetic layer
110
and the ferromagnetic layer
107
are preferably composed of the same material.
The diffusion preventing layer
106
is provided to prevent the mutual diffusion of the ferromagnetic layer
107
and the nonmagnetic conductive layer
105
, and to increase the GMR effect (&Dgr;MR) generated at the interface of the nonmagnetic conductive layer
105
.
When saturation magnetizations of the first free magnetic layer
110
and the second free magnetic layer
108
are shown by M
1
and M
2
, respectively, the magnetic film thickness of the first free magnetic layer
110
and the second free magnetic layer
108
become M
1
·t
1
and M
2
·t
2
, respectively.
Then, the free magnetic layer
111
is constituted so that the magnetic film thickness of the first free magnetic layer
110
and the magnetic film thickness of the second free magnetic layer
108
are made to meet the relation M
1
·t
1
>M
2
·t
2
.
The first free magnetic layer
110
and the second free magnetic layer
108
are antiferromagnetically coupled to each other. That is, when the direction of magnetization of the first free magnetic layer
110
is oriented in the X
1
direction shown in the drawings by bias layers
132
and
132
, the direction of magnetization of the second free magnetic layer
108
is oriented in the direction opposite to the X
1
direction.
The relationship of the magnetic film thickness of the first free magnetic layer
110
and the magnetic film thickness of the second free magnetic layer
108
is specified as being M
1
·t
1
>M
2
·t
2
, to create a state in which the magnetization of the first free magnetic layer
110
remains, and to orient the direction of magnetization of the free magnetic layer
111
, as a whole, in the X
1
direction shown in the drawings. At this time, a magnetic effective film thickness of the free magnetic layer
111
becomes (M
1
·t
1
−M
2
·t
2
).
Thus, because the first free magnetic layer
110
and the second free magnetic layer
108
are antiferromagnetically coupled to make each direction of magnetization antiparallel, and the relation of each magnetic film thickness is specified as being M
1
·t
1
>M
2
·t
2
, these are made to become the artificial ferrimagnetic state (synthetic ferrimagnetic state).
Therefore, the direction of magnetization of said free magnetic layer
111
and the direction of magnetization of said pinned magnetic layer
104
are cross each other.
The bias layers
132
and
132
are formed on both sides of the laminate
121
. These bias layers
132
and
132
orient the direction of magnetization of the first free ma
Hasegawa Naoya
Ide Yosuke
Saito Masamichi
Tanaka Ken'ichi
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kiliman Leszek
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