Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-12-29
2004-07-13
Chen, Tianjie (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06762916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head and to a floating-type magnetic head provided with the thin-film magnetic head.
2. Description of the Related Art
As magnetoresistive-type thin-film magnetic heads, magnetoresistive (MR) heads provided with elements exhibiting a magnetoresistive effect, and giant magnetoresistive (GMR) heads provided with elements exhibiting a giant magnetoresistive effect, are known.
In the GMR head, the element exhibiting the giant magnetoresistive effect has a multilayered structure. There are several types of multilayered structure for producing the giant magnetoresistive effect. One example thereof is a spin-valve thin-film magnetic element provided with at least a free magnetic layer, a pinned magnetic layer, and a nonmagnetic layer, in which the structure is relatively simple, and the resistance variation ratio in an external magnetic field is increased. Examples of spin-valve thin-film magnetic elements are a single spin-valve thin-film magnetic element and a dual spin-valve thin-film magnetic element.
In order to align the magnetization direction of the free magnetic layer, a hard bias method or an exchange bias method is used. Recently, as the magnetic recording density is increased, the exchange bias method which is suitable for track narrowing is predominantly used.
FIG. 17
shows a thin-film magnetic head
501
provided with a conventional single spin-valve thin-film magnetic element
502
using the exchange bias method.
The thin-film magnetic head
501
is a read-only head, in which a pair of shielding layers
507
and
508
is deposited on both sides in the thickness direction of the spin-valve thin-film magnetic element
502
with insulating layers
505
and
506
therebetween, respectively.
Additionally, in
FIG. 17
, the Z direction corresponds to the traveling direction of a magnetic recording medium, the Y direction corresponds to the direction of a fringing magnetic field from the magnetic recording medium, and the X
1
direction is the track width direction of the thin-film magnetic head
501
.
The spin-valve thin-film magnetic element
502
is a so-called “bottom-type” single spin-valve thin-film magnetic element, in which one each of an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer are deposited in that order.
In the spin-valve thin-film magnetic element
502
, the insulating layer
506
composed of Al
2
O
3
or the like is deposited on the lower shielding layer
508
, and an antiferromagnetic layer
512
, a pinned magnetic layer
513
, a nonmagnetic conductive layer
514
composed of Cu or the like, and a free magnetic layer
515
are deposited on the insulating layer
506
in that order.
A pair of bias layers
516
is deposited on the free magnetic layer
515
with a separation therebetween in the X
1
direction.
A pair of conductive layers
517
composed of Cu or the like is further deposited on the bias layers
516
, and the insulating layer
505
composed of Al
2
O
3
or the like is deposited over the conductive layers
517
and the free magnetic layer
515
.
The upper shielding layer
507
is deposited on the insulating layer
505
.
The antiferromagnetic layer
512
is composed of an antiferromagnetic material, such as a PtMn alloy, and an exchange coupling magnetic field (exchange anisotropic magnetic field) is produced at the interface between the pinned magnetic layer
513
and the antiferromagnetic layer
512
, thus pinning the magnetization direction of the pinned magnetic layer
513
in the Y direction.
The bias layers
516
are composed of an antiferromagnetic material, such as an IrMn alloy, and an exchange coupling magnetic field (exchange anisotropic magnetic field) is produced at the interface between the bias layers
516
and the free magnetic layer
515
. The exchange coupling magnetic field aligns the magnetization direction of the free magnetic layer
515
in the X
1
direction, i.e., the free magnetic layer
515
is aligned in a single-domain state, thus suppressing Barkhausen noise.
Accordingly, the magnetization direction of the free magnetic layer
515
and the magnetization direction of the pinned magnetic layer
513
are orthogonal to each other.
Since the pair of bias layers
516
are formed with a separation therebetween, a portion of the free magnetic layer
515
is not covered by the bias layer
516
, and this portion corresponds to a track section G
2
of the thin-film magnetic head
501
.
In the thin-film magnetic head
501
, the magnetization direction of the free magnetic layer
515
, which is aligned in the X
1
direction, is changed due to a fringing magnetic field from a recording medium, such as a hard disk, and the electrical resistance of the spin-valve thin-film magnetic element
502
is changed because of the relationship between the magnetization direction of the free magnetic layer
515
and the magnetization direction of the pinned magnetic layer
513
, which is pinned in the Y direction, and thus the fringing magnetic field from the magnetic medium is detected by a change in voltage due to the change in the electrical resistance.
However, in the conventional thin-film magnetic head
501
, since the conductive layers
517
for applying a sensing current to the free magnetic layer
515
are deposited on the pair of bias layers
516
, the sensing current flows in the bias layers
516
. Since the bias layers
516
, which are composed of the antiferromagnetic material, such as an IrMn alloy, have a high resistivity, when the sensing current flows in the bias layers
516
, the temperature of the spin-valve thin-film magnetic element
502
may be increased.
If the temperature of the spin-valve thin-film magnetic element
502
is increased, the magnetization of the free magnetic layer
515
which is aligned by the bias layers
516
becomes disordered, resulting in an increase in Barkhausen noise.
Since the sensing current flows in the high-resistivity bias layers
516
, the resistance of the spin-valve thin-film magnetic element
502
itself is increased, resulting in a decrease in reading output of the thin-film magnetic head
501
.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a thin-film magnetic head, in which Barkhausen noise is decreased and reading output is increased by preventing a rise in the temperature of a spin-valve thin-film magnetic element, and it is another object of the present invention to provide a floating-type magnetic head provided with the thin-film magnetic head.
In one aspect, a thin-film magnetic head, in accordance with the present invention, includes a spin-valve thin-film magnetic element, and includes a first insulating layer and a second insulating layer each deposited on a side in the thickness direction of the spin-valve thin-film magnetic element, and a first shielding layer and a second shielding layer in contact with the first insulating layer and the second insulating layer, respectively. The spin-valve thin-film magnetic element includes a free magnetic layer, a nonmagnetic conductive layer in contact with the free magnetic layer, the nonmagnetic conductive layer being located on one side in the thickness direction of the free magnetic layer, a pinned magnetic layer in contact with the nonmagnetic conductive layer, an antiferromagnetic layer in contact with the pinned magnetic layer, the antiferromagnetic layer pinning the magnetization direction of the pinned magnetic layer, a pair of bias layers for aligning the magnetization direction of the free magnetic layer, and a pair of conductive layers for applying a sensing current to the free magnetic layer. The pair of conductive layers is located on one side in the thickness direction of the free magnetic layer. The pair of bias layers is located on the other side in the thickness direction of the free magnetic layer, is disposed on both sides in the track width direction of at least a portion of the second insulating layer, and
Aoki Daigo
Kakihara Yoshihiko
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Chen Tianjie
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