Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-06-12
2004-06-29
Rickman, Holly (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S693100, C428S611000, C428S629000, C428S900000, C360S313000, C360S324100, C360S324110
Reexamination Certificate
active
06756135
ABSTRACT:
BACKGROUND
The present invention relates to spin valve thin-film magnetic elements having an electrical resistance that is defined by the relationship between the fixed magnetization direction of a pinned magnetic layer and the magnetization direction of a free magnetic layer that is influenced by an external magnetic field. The present invention also relates to thin-film magnetic heads having spin valve thin-film magnetic elements. In particular, the present invention relates to a technique in which the soft magnetic characteristics of the free magnetic layer and the rate of change in resistance of a spin valve thin magnetic element is improved.
A spin valve thin-film magnetic element is a giant magnetoresistive (GMR) element having giant magnetoresistance effects. A spin valve thin film can detect magnetic fields recorded in a recording medium, such as a hard disk.
The spin valve thin-film magnetic element has a relatively simple structure among the GMR elements. Since the rate of change in resistance of a spin valve thin-film magnetic element is high in response to an external magnetic field, the spin valve thin-film magnetic element has superior characteristics in which its resistance changes in accordance with a weak magnetic field applied thereto.
FIG. 10
is a schematic cross-sectional view showing the structure of a conventional spin valve thin-film magnetic element observed from a side air bearing surface opposing a recording medium. Shield layers are formed on the upper and the lower sides of the spin valve thin-film magnetic element with gap layers disposed therebetween. The spin valve thin-film magnetic element, the gap layers, and the shield layers constitute a reproducing GMR head. In addition, on the reproducing GMR head, a recording inductive head may be provided. This GMR and inductive head on a trailing edge side portion of a floating type slider detects magnetic fields recorded in a magnetic recording medium, such as a hard disk.
The conventional spin valve thin-film magnetic element shown in
FIG. 10
is a bottom type hard bias single spin valve thin-film magnetic element comprising a laminate composed of an antiferromagnetic layer
122
, a pinned magnetic layer
123
, a non-magnetic conductive layer
124
, a free magnetic layer
125
; and hard bias layers
129
positioned on the two sides of the laminate.
In this spin valve thin-film magnetic element, the moving direction of a magnetic recording medium, such as a hard disc, is in a Z direction in the figure, the direction of a leakage magnetic field is in a Y direction, and an X1 direction in the figure is a track width direction of the spin valve thin-film magnetic element.
The spin valve thin-film magnetic element shown in
FIG. 10
is made of a laminate
120
having an underlying layer
121
, the antiferromagnetic layer
122
, the pinned magnetic layer
123
, the non-magnetic conductive layer
124
, the free magnetic layer
125
, and a protective layer
127
layered from a bottom side in order. A pair of hard bias layers (permanent magnetic layers)
129
are positioned at the two sides of the laminate
120
and a pair of electrode layers
128
disposed on the hard bias layers
129
respectively. In general, a iron-manganese (Fe—Mn) alloy film, a nickel-manganese (Ni—Mn) alloy film, or a platinum-manganese (Pt—Mn) alloy film can be used for the antiferromagnetic layer
122
. A nickel-iron (Ni—Fe) alloy film can be used for the pinned magnetic layer
123
and the free magnetic layer
125
. A copper (Cu) film can be used for the non-magnetic conductive layer
124
. A cobalt-platinum (Co—Pt) alloy film can be used for the hard bias layers
129
. A chromium (Cr) film or a tungsten (w) film can be used for the electrode layers
128
. In addition, the underlying layer
121
and the protective layer
127
can be made of a tantalum (Ta) film. In this spin valve, a magnetic recording track width Tw is determined by the width of the upper surface of the laminate
120
.
The magnetization of the pinned magnetic layer
123
is placed in a single domain state in the Y direction (the direction of the leakage magnetic field from the recording medium, the height direction), as shown in
FIG. 10
, by the exchange anisotropic magnetic field generated by the exchange coupling at the interface with the antiferromagnetic layer
122
. In addition, the magnetization of the free magnetic layer
125
is aligned in a direction opposite to the X1 direction by the influence of the bias magnetic field of the hard bias layers
129
. That is, the magnetization of the pinned magnetic layer
123
and the magnetization of the free magnetic layer
125
are aligned perpendicular to each other.
In this spin valve thin-film magnetic element, a sense current is applied to the pinned magnetic layer
123
, the non-magnetic conductive layer
124
, and the free magnetic layer
125
from the electrode layers
128
formed on the hard bias layers
129
. The leakage magnetic field is applied from the magnetic recording medium. When the magnetization of the free magnetic layer
125
is changed from the direction opposite to the X1 direction to the Y direction due to the relationship of the change in magnetization direction of the free magnetic layer
125
and the fixed magnetization direction of the pinned magnetic layer
123
, the electrical resistance is changed (this change is called magnetoresistance (MR) effect), whereby the leakage magnetic field from the recording medium is detected by a change in voltage in accordance with the change in electrical resistance. In the spin valve thin-film magnetic element described above, the rate of change in resistance by an applied external magnetic field is approximately 8%.
For a recording medium, such as a hard disc, a higher recording density can be required. However, to improve the recording density, the magnetic recording track width can be decreased. That is, a narrower track can be required for the spin valve thin-film magnetic element. When the magnetic recording track width Tw is decreased, the track width for detecting an external magnetic field is decreased, and hence, the change in resistance (&Dgr;R) by the GMR effect is decreased. Consequently, the detection sensitivity of the spin valve thin-film magnetic element is decreased, and a problem may arise in which a higher recording density is difficult to achieve. Accordingly, there is a need for a spin-valve thin film magnetic element having an 8% rate of change of resistance that has an improved detection sensitivity. In addition to the narrower track, there is a need for an improved sensitivity without increasing a gap size, i.e., without increasing the dimension in the Z direction shown in FIG.
10
.
SUMMARY OF THE INVENTION
A spin valve thin-film magnetic element comprises a substrate; an antiferromagnetic layer disposed on the substrate, and a pinned magnetic layer disposed on the antiferromagnetic layer. Preferably, the magnetization direction of the pinned magnetic layer is fixed by an exchange coupling magnetic field with the antiferromagnetic layer. A non-magnetic conductive layer is positioned between the pinned magnetic layer and a free magnetic layer such that the magnetization direction of the free magnetic layer is aligned in a direction substantially perpendicular to the magnetization direction of the pinned magnetic layer. A pair of electrode layers supply a sense current to the pinned magnetic layer, the non-magnetic conductive layer, and the free magnetic layer and a bias layer to align the magnetization direction of the free magnetic layer in the direction substantially perpendicular to the magnetization direction of the pinned magnetic layer. A specular-reflection layer is positioned further from the non-magnetic conductive layer than the free magnetic layer which increases the free mean paths of conduction electrons by a specular effect. In a preferred embodiment, the film thickness of the free magnetic layer is preferably in the range of about 15 to about 45 Å.
The antiferromagnetic layer preferably comprises one of an
Hasegawa Naoya
Honda Kenji
Kakihara Yoshihiko
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Rickman Holly
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