Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-12-03
2003-07-29
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S125330
Reexamination Certificate
active
06600629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording element mounted on, for example, a hard disk device or the like, and particularly to a thin film magnetic head which can be improved in corrosion resistance, smoothness and demagnetization near the interface between a gap layer and a lower pole layer (or a lower core layer), and a method of manufacturing the thin film magnetic head.
2. Description of the Related Art
FIG. 14
is a partial front view showing the structure of a conventional thin film magnetic head.
In
FIG. 14
, reference numeral
1
denotes a lower core layer made of a magnetic material such as permalloy or the like, an insulating layer
9
being formed on the lower core layer
1
.
The insulating layer
9
has a trench
9
a
formed in the height direction (the Y direction shown in the drawing) from a surface facing a recording medium to have an internal width dimension corresponding to a track width Tw.
In the trench
9
a,
a lower pole layer
2
magnetically connected to the lower core layer
1
, a gap layer
4
, and an upper pole layer
5
magnetically connected to an upper core layer
6
are formed by plating in turn from the bottom. Furthermore, the upper core layer
6
is formed on the upper pole layer
5
by plating.
Furthermore, a coil layer (not shown in the drawing) is patterned in a spiral shape on the portion of the insulating layer
9
, which is behind the trench
9
a
formed in the insulating layer
9
in the height direction (the Y direction).
In the inductive head shown in
FIG. 14
, when a recording current is supplied to the coil layer, a recording magnetic field is induced in the lower core layer
1
and the upper core layer
6
. As a result, a magnetic signal is recorded on a recording medium such as a hard disk or the like by a leakage magnetic field from the gap between the lower pole layer
2
and the upper pole layer
5
magnetically connected to the lower core layer
1
and the upper core layer
6
, respectively.
The gap layer
4
is made of, for example, NiP which can be plated. A NiP film is conventionally formed by electroplating using a DC current.
However, it was found that when the NiP film was grown from the interface with the lower pole layer
2
by electroplating with a DC current, the content of element P was very low near the interface. For example, it was found from the experimental results described below that the content of element P was less than 8% by mass within a distance of about 2.5 nm from the interface in the thickness direction.
In electroplating with a DC current, the density of the current supplied to the NIP film during plating has a nonuniform distribution, and the current concentrates in a certain plating surface and continuously flows through the surface. The nonuniform current distribution possibly causes a significant decrease in the content of element P near the interface because element Ni, which easily produces lattice matching with the crystalline lower pole layer
2
, is epitaxially grown and crystallized. Also, the epitaxial growth of Ni worsens surface roughness at the interface.
The above-described NIP film having a very low content of element P near the interface and surface roughness exhibits low corrosion resistance and low resistance to neutral to alkali aqueous solutions. Therefore, the NIP film is readily corroded with a cleaning liquid used in the cleaning step of a slider manufacturing process to cause the problem of cracking, as shown in
FIG. 15
(schematic drawing). Thus, recording properties such as an overwrite performance deteriorate.
Also, when the content of element P is decreased near the interface, the vicinity of the interface is readily magnetized, and thus the gap length G
1
determined by the thickness of the gap layer
4
varies, thereby failing to manufacture a thin film magnetic head having predetermined recording properties in high yield.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been achieved for solving the above problem, and an object of the present invention is to provide a thin film magnetic head which is increased in the content of element P near the interface to improve corrosion resistance and smoothness of a gap layer and promote demagnetization at the interface, as compared with a conventional magnetic head.
Another object of the present invention is to provide a method of manufacturing a thin film magnetic head which comprising forming a gap layer by electroplating with a pulsed current to suppress crystallization of element Ni due to epitaxial growth near the interface and increase the content of a nonmagnetic element (for example, element P).
In order to achieve the objects of the present invention, a thin magnetic element comprises a lower core layer, a gap layer formed on the lower core layer directly or through a lower pole layer, and an upper core layer formed on the gap layer directly or through an upper pole layer which determined a track width, wherein the gap layer is formed by plating NiP, and the content of element P is 8% by mass to 15% by mass within a distance of 10 nm from the interface with the lower pole layer or the lower core layer in the thickness direction.
Therefore, the gap layer does not have a region in which Ni is crystallized by epitaxial growth from the interface with the lower pole layer or the lower core layer in the thickness direction. Thus, in the present invention, the vicinity of the interface is in an amorphous state containing 8% by mass to 15% by mass of element P, while in a conventional magnetic head, Ni is crystallized.
In this way, the interface is brought into the amorphous state containing more element P than the conventional magnetic head, thereby improving corrosion resistance and smoothness of the gap layer. Therefore, the gap layer is not corroded with a cleaning liquid used in a cleaning step of a slider manufacturing process, and thus the problem of cracking the gap layer can be prevented, unlike the conventional magnetic head. Furthermore, the region within a distance of 10 nm from the interface in the thickness direction contains 8% by mass to 15% by mass of element P, and thus the region can be demagnetized, thereby permitting high-yield manufacture of a thin film magnetic element with a predetermined value of gap length G
1
.
In the present invention, the content of element P is preferably 8% by mass to 15% by mass within a distance of 40 nm from the interface.
In the present invention, the content of element P is preferably 10% by mass to 15% by mass, and more preferably 11% by mass to 15% by mass.
With the content of element P within the above range, crystallization of element Ni by epitaxial growth can be further suppressed to further improve corrosion resistance of the gap layer, and promote demagnetization near the interface of the gap layer, thereby permitting manufacture of a thin film magnetic head having good recording properties.
In the present invention, the average content of element P of the gap layer over its entire thickness is preferably 11% by pass to 15% by mass.
By controlling not only the content of element P within the distance of at least 10 nm, preferably 40 nm, from the interface, but also the average content of element P of the gap layer over its entire thickness within the above-described ranges, the corrosion resistance of the entire gap layer can be improved, and demagnetization of the entire gap layer can be promoted, thereby enabling the secure occurrence of a leakage magnetic field neat the gap layer.
The content of element P is measured by using an X-ray analysis apparatus. Since only a relative value of the content of element P can be obtained by the X-ray analysis apparatus, the content of element P obtained by the X-ray analysis apparatus is corrected to an absolute value by wet analysis. The thus-obtained value is the content of element P of the present invention.
The distance from the interface with the lower pole layer or the lower core layer is measured by using a transmission electron microsc
Kanada Yoshihiro
Yazawa Hisayuki
Alps Electric Co. ,Ltd.
Tupper Robert S.
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