Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-01-16
2004-06-15
Ometz, David (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06751071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head mounted on, for example, a hard magnetic disk device, or the like, and particularly to a thin film magnetic head adaptable to higher recording densities, and a method of manufacturing the same.
2. Description of the Related Art
A thin film magnetic head mounted on a hard magnetic disk device or the like is formed on a slider
51
comprising ceramic such as Al
2
O
3
—TiC or the like, as shown in FIG.
21
. The slider
51
has a substantially rectangular shape, and comprises one end surface
51
a
on which the thin film magnetic head is formed, and the magnetic disk-facing surface
51
b
substantially perpendicular to the end surface
51
a.
A conventional thin film magnetic head is a combination thin film magnetic head comprising a reproducing head h
51
and a recording head h
52
, for example, as shown in FIG.
22
. The reproducing head h
51
comprises a lower shield layer
52
comprising a soft magnetic film of a Ni—Fe alloy or the like formed on an underlying layer
65
made of alumina or the like, a lower gap layer
53
comprising a nonmagnetic material such as alumina or the like and formed to cover the lower shield layer
52
, a magnetoresistive element
54
formed on the lower gap layer
53
, an electrode layer
55
electrically connected to the magnetoresistive element
54
, an upper gap layer
56
comprising a nonmagnetic material such as alumina or the like and formed to cover the magnetoresistive element
54
and the electrode layer
55
, and an upper shield layer
57
comprising a soft magnetic Ni—Fe alloy film and formed on the upper gap layer
56
. In the reproducing head h
51
, the gap between the upper shield layer
57
and the lower shield layer
52
serves as reproducing gap G
1
.
In the combination type thin film magnetic head, the recording head h
52
comprises a lower core layer also used as the upper shield layer
57
of the reproducing head h
51
, a gap layer
58
comprising a nonmagnetic material such as alumina, SiO
2
, or the like and formed on the lower core layer, a coil layer
59
comprising a good conductive material such as Cu or the like and formed on the gap layer
58
, and an upper core layer
60
comprising a soft magnetic film of a Ni—Fe alloy and formed on the coil layer
59
with an insulating film
61
of resist or the like provided therebetween. The base end
60
a
of the upper core layer
60
is magnetically connected to the lower core layer serving as the upper shield layer
57
.
In the method of manufacturing the conventional thin film magnetic head, the method of producing the upper shield layer
57
comprising a Ni—Fe alloy film comprises the underlying film forming step of forming a Ni—Fe alloy underlying film to a thickness of 0.1 &mgr;m on the upper gap layer by sputtering deposition, and then the plating step of plating an Ni—Fe alloy film of about 3 &mgr;m thick on the underlying film by an electroplating method using the underlying film as a cathode. In the plating step, the magnitude of the current applied to a plating bath is kept at 7 mA/cm
2
.
During a drive of the hard magnetic disk device, the slider
51
flies with the magnetic disk-facing surface
51
facing the rotating magnetic disk.
In the reproducing head h
51
of the thin film magnetic head, the magnetoresistive element
54
detects a recording signal magnetic field of the magnetic disk, which is produced in the reproducing gap G
1
to reproduce a recording signal.
In the combination type thin film magnetic head, the recording head h
52
provided on the reproducing head h
51
supplies a recording signal to the magnetic disk by means of a leakage magnetic field between the core layers
57
and
60
, which is produced by a recording current of the coil layer
59
.
At this time, the upper shield layer
57
and the lower shield layer
52
play the function to cut off an extra magnetic field (a magnetic field of a recording signal outside the reproducing gap G
1
of the magnetic disk) flowing into the reproducing head h
51
from the magnetoresistive element
54
.
The upper shield layer
57
is required to prevent a magnetic disturbance from occurring due to a magnetic field from a recording signal of the magnetic disk, a magnetic field induced by the lower core layer of the recording head h
52
, or deformation due to the head generated from the coil layer
59
or the like, and to have low magnetostriction.
A graph of
FIG. 23
indicates that magnetostriction of a Ni—Fe alloy film depends upon the composition ratio of the Ni—Fe alloy film, and magnetostriction is substantially zero when the Fe composition ratio of the Ni—Fe alloy film is close to 18% by weight.
With the Ni—Fe alloy film comprising a Ni—Fe alloy underlying film formed by sputtering deposition, and a Ni—Fe alloy plating film formed by electroplating using the underlying film as a cathode like the upper shield layer
57
, the composition ratio of the Ni—Fe alloy film depends upon the density of the current applied to the plating bath used in the step of forming the Ni—Fe alloy plating film.
FIG. 24
is a graph showing the relation between the current density applied to the plating bath and the composition ratio (Fe % by weight) of the Ni—Fe alloy film when the underlying film of the Ni—Fe alloy film has a thickness of 0.1 &mgr;m, and the plating film has a thickness of about 3 &mgr;m.
This graph indicates that the Fe composition ratio of the N—Fe alloy film is 17 to 19% by weight when the magnitude of the current applied to the plating bath is 6 to 8 mA/cm
2
.
However, a recent thin film magnetic head in which the reproducing gap G
1
has been narrowed with increasing recording density has the problem of producing noise in a reproduced signal of the magnetoresistive element
54
possibly due to magnetostriction of the upper shield layer
57
.
FIG. 26
is a graph showing the results of measurement of the Fe composition ratio distribution of the Ni—Fe alloy film in the thickness direction thereof with respect to the upper shield layer
57
. The graph of
FIG. 26
indicates that even when the Fe composition ratio of the entire upper shield layer
57
of about 3 &mgr;m is 18% by weight, the plating film having a thickness of about 0.2 &mgr;m from the surface of the underlying film is a layer (Fe-rich layer) having a Fe composition ratio of over 19% by weight. As shown in the graph of
FIG. 25
, the magnetostriction of the Fe-rich layer reaches 2×10
−6
.
The possible cause of producing noise in the reproduced signal of the magnetoresistive element
54
is that the magnetoresistive element
54
comes near the upper shield layer
57
with narrowing of the gap of the thin film magnetic head, and thus the magnetoresistive element
54
is affected by a magnetic disturbance produced in the Fe-rich layer of the upper shield layer
57
.
In the formation of the Ni—Fe alloy film by sputtering deposition, the above-described Fe-rich layer is not present, but patterning of the sputtered film requires a dry etching step, and the time required for the dry etching step increases as the thickness of the sputtered film increases to deteriorate etching controllability.
When the whole upper shield layer
57
is formed by the sputtering deposition method, the excessive Ni—Fe alloy film is completely removed in the step of patterning the upper shield layer. In this case, the upper gap layer
56
, which is thinned due to gap narrowing, is also removed to damage the exposed electrode layer
55
.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a thin film magnetic head causing no noise in a reproduced signal due to magnetostriction of an upper shield layer, and adaptable to higher recording densities.
A thin film magnetic head of the present invention comprises a lower shield layer comprising a soft magnetic film, a magnetoresistive element formed on the lower shield layer with a lower gap layer formed therebetween and made of a nonmagnetic material, an electrode layer e
Kanada Yoshihiro
Sakatsume Naoki
Yazawa Hisayuki
Alps Electric Company Co., Ltd.
Brinks Hofer Gilson & Lione
Ometz David
LandOfFree
Thin film magnetic head comprising magnetoresistive element... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thin film magnetic head comprising magnetoresistive element..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thin film magnetic head comprising magnetoresistive element... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3341186