Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-08-13
2003-10-21
Letscher, George J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06636399
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistance effect device composed of a magnetic multi-layer film having giant magnetoresistance effect, a magnetic head therewith, a magnetic recording/reproducing head therewith, and a magnetic storing apparatus therewith.
2. Description of the Related Art
In magnetic recording apparatuses such as a HDD (Hard Disk Drive), the record track width is being decreased so as to increase the record density. To compensate the decrease of the reproduced output due to the decrease of the record track width, a magnetic head having a high sensitive magnetoresistance effect device (MR device) is being required. In particular, an MR head having a spin valve film with giant magnetoresistance effect is hopeful as a successor. The spin valve film is composed of a magnetic multi-layer having a ferromagnetic film whose magnetization rotates corresponding to a signal magnetic field (this film is hereinafter referred to as a magnetization free layer), a non-magnetic film, a ferromagnetic film whose magnetization is fixed with a bias magnetic field of an antiferromagnetic film (this ferromagnetic film is hereinafter referred to as a fixed magnetization layer), and an antiferromagnetic layer that fixes the magnetization of the fixed magnetization layer.
In an MR head having the spin valve film, there are large practical problems of Barkhausen noise causes by a magnetic domain wall of the magnetization free layer and a reproduction fringe in the vicinity of both edge portions of a reproduction track. To solve these problems, as shown a cross section diagram viewed from direction opposite to a medium in
FIG. 12
, a so-called abutted junction type MR head of which outer portions of both edge portions
1
a
and
1
a
of a record track width of a spin valve film
1
are etched out and instead hard magnetic films
2
are disposed thereto has been proposed.
The spin valve film
1
shown in
FIG. 12
has a magnetization free layer
4
, a non-magnetic film
5
, a fixed magnetization layer
6
, and an antiferromagnetic film
7
that are formed in the order on a substrate
3
. In addition, a pair of electrodes (reproduction electrodes)
8
that supply a sense current to the spin valve film
1
are formed on the hard magnetic film
2
.
In the MR head of abutted junction type shown in
FIG. 12
, a bias magnetic field of the hard magnetic film
2
causes a magnetic domain of the magnetization free layer
4
to disappear, thereby suppressing Barkhausen noise. In addition, since a portion other than the record track width is substituted with the hard magnetic film
2
, only record information can be read-from record track. Thus, the reproduction fringe can be remarkably reduced.
However, the MR head having the spin valve film I of the abutted junction type has the following problems. Firstly, a gap film (not shown) composed of a non-magnetic insulator such as alumina is disposed below the spin valve film
1
. Thus, the reproduction electrode
8
and the hard magnetic film
2
contact a wall surface of the spin valve film
1
that has been etched out. Consequently, the contact resistance increases or becomes unstable.
Secondly, when the magnetization free layer
4
at both the edge portions of the spin valve film
1
is etched out, since the magnetization free layer
4
is disposed at the bottom position, the gap film tends to be excessively etched out. Thus, an insulation defect of a magnetic shield layer disposed below the gap film tends to take place.
Thirdly, when the spin valve film is etched out, the lower portion of the spin valve film
1
is lesser tapered than the upper portion thereof. Thus, an exchange-coupled region of the hard magnetization film
2
and the magnetization free layer
4
increases in the taper portion. In the taper portion, since the exchange-coupled force is unstable, Barkhausen noise tends to take place.
Fourthly, since the edge wall surface of the hard magnetic film
2
inevitably contacts the edge wall surface of the fixed magnetization layer
6
, the bias magnetic field of the hard magnetic film
2
is applied to the fixed magnetization layer
6
. Thus, the magnetization of the fixed magnetization layer
6
to be fixed in the direction of the width of the spin valve film
1
(in the direction to which the signal magnetic field is applied) is inclined to the direction of the bias of the hard magnetic film
2
(the longitudinal direction of the spin valve film
1
). Consequently, a good linear response to the signal magnetic field can not be obtained.
In addition, another MR head has been proposed. in this MR head, a bias magnetic field applying film such as a hard magnetic film and an antiferromagnetic film is directly layered on edge portions of an MR film so as to exchange-couple them. Thus, Barkhausen noise is removed. However, in the conventional spin valve film of which a fixed magnetization layer or the like is disposed on a magnetization free layer, a hard magnetic film and an antiferromagnetic film should be disposed on the substrate side. When these films are patterned, the surface characteristic of a base film of the spin valve film deteriorates.
In particular, to stably exchange-couple the hard magnetic film and the antiferromagnetic film with the magnetization free layer, the film thickness of the hard magnetic film and the antiferromagnetic film should be increased. In the case that these films are thick, when they are patterned, the surface characteristic of the base layer of the spin valve film inevitably deteriorates. In addition, with the antiferromagnetic film, it is difficult to obtain a strong exchange bias. With the hard magnetic film, coercive force decreases due to the reaction of the magnetization free layer. Thus, the magnetization cannot be stably fixed at the edge portions of the track width. Consequently, the decrease of reproduction fringe and the suppression of Barkhausen noise are insufficient.
As described above, with the MR head having the conventional spin valve of the abutted junction type, the contact resistance increases or becomes unstable due to the shape thereof. Insulation defect and unstable exchange coupling of the hard magnetic film and magnetization free layer tend to take place. In addition, since the magnetization of the fixed magnetization layer is inclined, a good linear response to a signal magnetic field cannot be obtained.
On the other hand, with the MR head of which the bias magnetic field applying film such as a hard magnetic film and an antiferromagnetic film is directly layered on a spin valve film, the surface characteristic of the base film of the spin valve film deteriorates. Moreover, the magnetization cannot be stably fixed at the edge portions of the track width. Thus, the decrease of reproduction fringe and the suppression of Barkhausen noise are insufficient.
Furthermore, a magnetic storing apparatus such as a magnetoresistance effect random access memory (MRAM) having a spin valve film has been studied. In this case, a sufficient bias is required.
SUMMARY OF THE INVENTION
Thus, an object of the present invention is to provide a magnetoresistance effect device that suppresses reproduction fringe and Barkhausen noise and that accomplishes the decrease of contact resistance, suppression of insulation defect, and good linear response. Another object of the present invention is provide a magnetic head having the magnetoresistance effect device so as to improve characteristics, a magnetic recording/reproducing head thereof, and a magnetic storing apparatus thereof.
A first aspect of the present invention is a magnetoresistance effect device, comprising a substrate having a main surface, a magnetoresistance effect film composed of a magnetic multi-layer film having at least an antiferromagnetic film, a first ferromagnetic film, a non-magnetic film, and a second ferromagnetic film formed in the order above the main surface portion of the substrate, the magnetic multi-layer film having giant magnetoresistance effect, the second ferr
Fuke Hiromi
Iwasaki Hitoshi
Kamiguchi Yuzo
Sahashi Masashi
Saito Kazuhiro
Kabushiki Kaishia Toshiba
Letscher George J.
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