Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-12-14
2002-04-23
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S690000, C428S900000, C360S112000, C324S252000
Reexamination Certificate
active
06376108
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority of Japanese Patent Applications Nos. Hei 10-354305 and Hei 11-308827, filed, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a magnetic material, magnetic head and magnetic storage device and particularly to a magnetic material, magnetic head and magnetic storage device having the characteristic for composition to improve high frequency characteristic of induction type head and MR head forming a composite type thin film magnetic head to be used in the magnetic storage device such as a Hard Disk Drive (HDD) or magnetic tape device.
b) Description of the Related Art
Because of growing of request in these years for reduction in size and expansion of capacity of a hard disk drive as an external storage device of computer, the recording frequency is reaching 100 MHz (10
8
Hz). In such magnetic storage device, the magnetic heads for writing and reading recording data are always integrally structured in such a manner that the write head for recording and the read head for reproducing are individually arranged. Namely, these heads are sequentially laminated as the layers in a series of filming process so that the recording head and reading heads are accurately arranged adjacently with less positional deviation in the narrow pitch for the write and read operation of magnetic recording medium in order to realize high density recording.
The upper magnetic pole layer of such a thin film magnetic head is often formed using a permalloy alloy such as Ni
82
Fe
18
or the like which has been integrally formed by the mask plating method. Here, however, an example of the composite type thin film magnetic head of the related art will be explained with reference to FIG.
6
.
FIG. 6
is a schematic perspective view of the essential portion of a composite type thin film magnetic head of the related art. A lower shield layer
41
consisting of NiFe alloy or the like is provided, through the Al
2
O
3
film (not illustrated), on the Al
2
O
3
-TiC substrate (not illustrated) as the mother material of slider, a magnetic resistance effect element
42
consisting of a laminated structure, etc. of NiFe, Ti, NiFeCr is provided via a lower lead gap layer (not illustrated) such as Al
2
O
3
or the like, these are then patterned in the predetermined shape and thereafter a read electrode
43
is formed by depositing a conductive film consisting of Au, etc. to both ends of the magnetic resistance effect element
42
.
Next, a lower magnetic pole layer
44
, which also works as the upper shield layer, consisting of NiFe alloy or the like is provided again via the upper lead gap layer (not illustrated) such as Al
2
O
3
or the like and a write gap layer (not illustrated) consisting of Al
2
O
3
or the like is provided thereon, a horizontal spiral type write coil
45
is formed via a lower inter-layer insulating film (not illustrated) such as resist, etc., a write electrode
46
is provided to both ends of such coil, and thereafter an upper magnetic pole layer
47
in such a shape as providing a narrow write pole
48
at the end part is provided via the upper interlayer insulating film (not illustrated) consisting of resist, etc.
Next, after the Al
2
O
3
film is provided to the entire surface as a protection film (not illustrated), a substrate is cut, and machining and slider process including the grinding are performed for adjusting the length of write pole
48
, namely the depth of gap. Thereby, a composite type thin film magnetic head in which the MR head for reproducing, namely for reading and an induction type thin film magnetic head for recording, namely for writing utilizing the magnetic resistance effect element
42
can be obtained.
In this case, a magnetic flux generated when a signal current flows into the write coil
44
from a write electrode
46
is guided to a magnetic pole core consisting of the lower magnetic pole layer
44
and upper magnetic pole layer
47
, the magnetic flux leaks to the outside by the recording gap formed by the write gap layer at the area near the write pole
48
at the end part of the upper magnetic pole layer
47
and thereby signal is recorded to a recording medium. Moreover, on the contrary, the signal can also be reproduced by detecting the magnetic flux from the recording medium with the magnetic pole core, width of the write pole
48
at the end of the upper magnetic pole layer
47
becomes the track width and the surface recording density can be restricted by this track width.
On the other hand, the reproducing principle of the MR head utilizes the phenomenon that when a constant sense current flows from a read electrode
43
, electrical resistance of magnetic thin film forming the magnetic resistance effect element
42
changes depending on the magnetic field from the recording medium.
However, there is a problem that the shield effect for magnetic field noise and drive magnetic field in the frequency of 10 MHz to several tens of MHz and magnetic recording capability in the magnetic shield and upper and lower magnetic pole layers in a composite type thin film magnetic head are largely lowered due to an eddy current loss and thereby recording defect may easily be generated. This problem may be generated because when the frequency becomes higher, an eddy current loss also increases and recording magnetic field intensity is lowered by the surface effect. In order to control such eddy current loss, it is enough that the specific resistance &rgr; is raised because the eddy current loss is inversely proportional to the specific resistance &rgr;.
Namely, when a radius of magnetic thin film, namely thickness is &tgr; [m], frequency is f [MHz], intensity of magnetization is Bm[Wb/m
2
] and specific resistance is &rgr; [&OHgr;·m], an eddy current loss We per unit volume flowing a magnetic material when a coil is wound around the column type magnetic material of radius 5[m] and a coil current is impressed thereto can be expressed as follow.
We=&pgr;
2
·&tgr;
2
·f
2
·Bm
2
/4&rgr; (1)
Therefore, when the specific resistance &rgr; is large or when radius &tgr; is small, an eddy current loss We becomes small.
Moreover, when specific resistance &rgr;, thickness of magnetic film is &tgr;, vacuum permeability is &mgr;o and permeability of magnetic film is &mgr;d, the limit frequency fg is expressed as follow.
fg=
4&rgr;/(&pgr;·&mgr;o·&mgr;d·
t
2
) (2)
Therefore, when the specific resistance &rgr; is large or thickness t is small, the limit frequency fg becomes large.
However, since the upper magnetic pole layer
47
and write pole
48
in the related art are themselves formed of permalloy such as Ni
82
Fe
18
or the like, the specific resistance &rgr; is as small as about 20 &mgr;&OHgr;cm and moreover since it is integrally formed of comparatively thick film by the plating, here rises a problem that values of &tgr; or t become large, eddy current loss We unnecessarily becomes large and thereby the limit frequency fg unnecessarily becomes small.
On the other hand, when thickness t of magnetic film is set to a small value, eddy current loss We can be made small and the limit frequency fg can be made large. However, in this case, another problem that total magnetic flux becomes small is also generated.
In view of solving such problems, development is now being continued to attain the material having higher &rgr; than that of permalloy such as Ni
82
Fe
18
or the like. For example, it has been proposed to use, as the high frequency magnetic pole material, the NiFeMo alloy film having the magnetic characteristic almost identical to that of permalloy and specific resistance &rgr; (≧20 &mgr;&OHgr;cm) (if necessary, refer to Japanese Published Unexamined Patent Application No.: HEI 9-63016).
SUMMARY OF THE INVENTION
In the above, the NiFeMo alloy film proposed as the magnetic strain &lgr;s as large as exceeding 5×10
&mi
Miyake Yuko
Otagiri Mitsuru
Takefusa Sanae
Fujitsu Limited
Greer Burns & Crain Ltd.
Kiliman Leszek
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