U.S. patent application number 14/484442 was filed with the patent office on 2015-01-29 for wrap-around shielded writer with highly homogeneous shield material.
The applicant listed for this patent is Headway Technologies, Inc.. Invention is credited to Zhigang Bai, Cherng Chyi Han, Moris Dovek, Yan Wu.
Application Number | 20150029616 14/484442 |
Document ID | / |
Family ID | 43898697 |
Filed Date | 2015-01-29 |
United States Patent
Application |
20150029616 |
Kind Code |
A1 |
Bai; Zhigang ; et
al. |
January 29, 2015 |
Wrap-Around Shielded Writer with Highly Homogeneous Shield
Material
Abstract
A perpendicular magnetic recording (PMR) head is fabricated with
a main pole shielded laterally by a pair of side shields, shielded
above by a trailing shield and shielded optionally below by a
leading shield. The shields and the seed layers on which they are
formed are formed of materials having substantially the same
physical characteristics including the same material composition,
the same hardness, the same response to processes such as ion beam
etching (IBE), chemical mechanical polishing (CMP), mechanical
lapping, such as the slider ABS lapping, the same coefficient of
thermal expansion (CTE) as well as the same B.sub.s. Optionally,
the trailing shield may be formed on a high B.sub.s seed layer to
provide the write head with improved down-track performance.
Inventors: |
Bai; Zhigang; (Milpitas,
CA) ; Wu; Yan; (Cupertino, CA) ; Dovek;
Moris; (San Jose, CA) ; Chyi Han; Cherng; (San
Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Headway Technologies, Inc. |
Milpitas |
CA |
US |
|
|
Family ID: |
43898697 |
Appl. No.: |
14/484442 |
Filed: |
September 12, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12589597 |
Oct 26, 2009 |
8842389 |
|
|
14484442 |
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Current U.S.
Class: |
360/236.5 |
Current CPC
Class: |
G11B 5/3163 20130101;
Y10T 428/1171 20150115; G11B 5/315 20130101; G11B 5/1278 20130101;
G11B 5/112 20130101; G11B 5/6082 20130101 |
Class at
Publication: |
360/236.5 |
International
Class: |
G11B 5/60 20060101
G11B005/60; G11B 5/11 20060101 G11B005/11; G11B 5/127 20060101
G11B005/127 |
Claims
1. A PMR write head comprising: a main pole; a magnetic shield at
least partially surrounding said main pole and formed in the ABS
plane of said pole tip, wherein said shield includes a trailing
shield portion and a portion including two side shields, wherein
said trailing and side shield portions are formed of the same
magnetic material and are formed using the same seed layers and
form a substantially continuous structure, and wherein said
trailing and side shield portions are separated from said main pole
by a substantially continuous non-magnetic layer, wherein said
non-magnetic layer forms a write gap layer extending laterally
between inner edges of said side shields and along a trailing edge
of said main pole and wherein said non-magnetic layer forms a side
gap between side edges of said main pole and inner edges of said
side shields.
2. The PMR write head of claim 1 further including a leading edge
shield portion formed beneath a leading edge of said main pole and
continuous with said trailing edge shield portion and said side
shield portions and thereby completely surrounding said main pole
and wherein said leading edge shield portion is separated from said
main pole by a leading edge gap that is formed as a portion of said
non-magnetic layer.
3. The PMR write head of claim 1 wherein said main pole is formed
of material having a high B.sub.s, ranging from 2.2 T to 2.4 T.
4. The PMR write head of claim 3 wherein said main pole is formed
of NiFe, CoFe, CoNiFe, CoFePd, or CoFeN.
5. The PMR write head of claim 1 wherein said leading and trailing
shields and their seed layers, are formed of material having a
B.sub.s ranging from 1.5 T to 2.2 T.
6. The PMR write head of claim 5 wherein said material is NiFe,
CoFe, CoNiFe, CoFePd, or CoFeN.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to the fabrication of a perpendicular
magnetic recording (PMR) write head whose main pole is surrounded
on all sides by shields formed of magnetic material. In particular
it relates to the formation of such shields using layers of the
same magnetic material so that a consistent fabrication process can
be employed and so that a corresponding consistent performance can
be obtained.
[0003] 2. Description of the Related Art
[0004] The increasing need for high recording area densities (up to
500 Gb/in.sup.2) is making the perpendicular magnetic recording
head (PMR head) a replacement of choice for the longitudinal
magnetic recording head (LMR head).
[0005] By means of fringing magnetic fields that extend between two
emerging pole pieces, longitudinal recording heads form small
magnetic domains within the surface plane of the magnetic medium
(hard disk). As recorded area densities increase, these domains
must correspondingly decrease in size, eventually permitting
destabilizing thermal effects to become stronger than the magnetic
interactions that tend to stabilize the domain formations. This
occurrence is the so-called superparamagnetic limit. Recording
media that accept perpendicular magnetic recording, allow domain
structures to be formed within a magnetic layer, perpendicular to
the disk surface, while a soft magnetic underlayer (SUL) formed
beneath the magnetic layer acts as a stabilizing influence on these
perpendicular domain structures. Thus, a magnetic recording head
that produces a field capable of forming domains perpendicular to a
disk surface, when used in conjunction with such perpendicular
recording media, is able to produce a stable recording with a much
higher area density than is possible using standard longitudinal
recording.
[0006] Since their first use, the PMR head has evolved through
several generations. Initially, the PMR head was a monopole, but
that design was replaced by a shielded head design with a trailing
edge shield (TS), which provides a high field gradient in the
down-track direction to facilitate recording at high linear
densities. Side shields (SS) then began to be used in conjunction
with the trailing edge shields, because it was necessary to
eliminate the fringing side fields in order to increase writing
density still further. To further reduce the fringing in the
down-track direction, thus reducing the length of the "write
bubble" (the iso-field contour) down the track and improving write
performance at a skew angle, a leading edge shield (LS) was also
proposed, making the write head four-side shielded.
[0007] Despite the aforementioned advantages for the four-sided
shielded design, it does require additional design optimizations
for all the shield layers. It is believed that a high saturation
magnetic moment (B.sub.s) seed layer, such as CoFe with a B, of 2.4
T (Tesla), for the TS would improve the down-track field gradient.
It is also traditionally believed that the LS and TS are somewhat
"non-critical" layers and they are often formed of very low moment
material such as permalloy. As a result, there will be a
significant mismatch in material compositions and moments for these
layers, all of which are exposed at the ABS (air bearing surface)
of the write head.
[0008] Several issues may arise as a result of materials and moment
mismatches. First, the pole tip recession/protrusion may be very
different between the layers, as a result of hardness differences
between the materials and lapping rate variations during the slider
lapping process that defines the final ABS. This may affect the
magnetic spacing between the write pole and media during write
operation, thereby adversely affecting performance. For example,
AFM (atomic force microscopy) images show higher protrusion of the
TS/SS seed layer relative to the surrounding materials. The seed
layer has a B.sub.s=2.2 T, whereas for the TS/SS shield materials
themselves B.sub.s=1.9 T. Another downside of higher seed layer
protrusion could be erasures from the shield corners due to
closeness of the seed layers to the media.
[0009] Another issue associated with the material/moment mismatches
between different shield layers is the formation of domain walls at
the layer interfaces that may cause wide area track erasures
(WATE). This could be a result of different material
magnetostrictions causing different domain configurations in
neighboring layers, which, in turn create domain walls at the
interfaces, or it could just be due to the moment mismatches
producing magnetic charges at the interfaces which produce stray
fields.
[0010] Magnetic force microscopy applied to shield configurations
with WS1 (trailing shield) and PP3 (plated top layer) layers formed
of materials having B.sub.s=1.8 T and 1.0 T show evidence of domain
walls propagating from the MP region upward and stopping at the
interface between the materials. On the other hand, wrap-around
shield configurations with all shields, SS, WS1 and PP3 made of the
same B, material, show no such domain walls on the ABS and there is
no WATE.
[0011] An additional disadvantage of using low B, materials in the
LS and pole yoke layers is that in order to conduct the same amount
of magnetic flux as a material with twice the value of B.sub.s,
would require twice the thickness. For example, the use of low
B.sub.s Ni.sub.80Fe.sub.20 vs. a NiFe, CoFe or CoNiFe alloy with a
B.sub.s of about 2.0 T. Larger metal volumes required of the lower
B.sub.s metals will cause larger protrusions during temperature
increases either due to ambient increases or the heat generated by
energizing currents.
[0012] Issues relevant to shield materials are described in the
prior arts. For example, Terris et al. (U.S. Pat. No. 7,068,453)
discloses side and trailing shields formed of a soft magnetic
material.
[0013] Gao et al. (U.S. Pat. No. 7,441,325) discloses a trailing
shield formed of NiFe. Nix et al. (U.S. Pat. No. 7,367,112) teaches
the formation of a main pole with trailing and side shields.
[0014] Guan et al. (U.S. Pat. No. 7,322,095, assigned to the
present assignee) teaches a wrap-around shield, as do Jiang et al.
(US Patent Application 2009/0154026) and Hsiao et al. (US Patent
Application 2009/0154019).
[0015] None of the prior art cited above address the problem
addressed by the present invention nor do they disclose the
structures and materials of the present invention.
SUMMARY OF THE INVENTION
[0016] A first object of this invention is to reduce the local
protrusion of a shield layer due to mismatches in the materials
used to form the layers and used to form various structures in the
head itself.
[0017] A second object of the present invention is to eliminate the
formation of domain walls at the interfaces between the TS, SS and
LS portions of a four sided magnetic shield due to mismatches in
either the materials or their moments, thereby eliminating wide
area track erasures (WATE) that are associated with such domain
walls.
[0018] A third object of the present invention is to reduce the
pole tip protrusion for a magnetic writer that uses a low B.sub.s
high thickness combination for certain shield layers, such as the
LS and TS.
[0019] A fourth object of the present invention is to achieve the
above stated objects without diminishing the on-track and off-track
performance of the head.
[0020] A fifth object of the present invention is to use the head
so formed and provided within a hard disk drive incorporating a
slider mounted read/write head whose head is the head of the
present invention, where the slider is mounted on a head gimble
assembly within the hard disk drive.
[0021] These objects will be achieved by means of a wrap-around
shielded write head whose main pole (MP) is surrounded by a TS
(trailing shield), an optional LS (leading shield) and two SS's
(side shields). Note that in some figures, particularly in an ABS
view, the trailing shield, TS is shown as two portions, which are
labeled WS1 and PP3. The WS1 (write shield 1) portion is the main
part of the TS, whereas the portion labeled PP3 is the ABS portion
of the return yoke that completes the magnetic circuit with the
main pole.
[0022] The non-magnetic write gap (WG) between the MP and the TS,
the non-magnetic side gap (SG) between the MP and the SS, and the
leading gap (LG) between the MP and the LS, are separately
optimized and controlled. The WG is typically 15 to 50 nm, the SG
is typically one to ten times the width of the WG and the LG is
typically one to twenty times the WG. An important feature of the
invention is that all shield layers, LS, TS and SS, including WS1
and PP3, an their respective seed layer, have substantially the
same material composition, the same hardness, the same response
(eg. removal rate) to processes such as ion beam etching (IBE),
chemical mechanical polishing (CMP), mechanical lapping, such as
the slider ABS lapping, and the same coefficient of thermal
expansion (CTE) as well as the same B.sub.s. By "substantially the
same," is meant the fact that the physical characteristics (removal
rate, CTE, B.sub.s) among the various layers and their seeds may
have small variations on, the order of 10%, of their respective
nominal values. For example, a nominal B, of 2.0 T could have
+/-0.1 T.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Fig. la is a schematic representation of a first embodiment
of the present invention showing a side cross-sectional view of an
inductive-type write head in which is seen a main pole surrounded
by the shields of the present invention at its trailing edge and
leading edge, the side shields being there as well, but not visible
in this view.
[0024] FIG. 1b is a schematic ABS view of the write head of FIG. 1a
showing the main pole tip surrounded by the shields of the present
invention at its trailing edge, leading edge and sides.
[0025] FIG. 2a is a schematic representation of a second embodiment
of the present invention showing a side cross-sectional view of an
inductive-type write head in which is seen a main pole surrounded
by the shields of the present invention at its trailing edge and
leading edge. This figure also shows a high B, seed layer that
resides at the bottom of the trailing edge shield (WS1) just above
the write gap (WG) layer. The side shields are also present, but
not visible.
[0026] FIG. 2b is a schematic ABS view of the write head of FIG. 2a
showing the main pole tip surrounded by the shields of the present
invention at its trailing edge, leading edge and sides as well as
the high B, seed layer..
[0027] FIG. 3a is a schematic representation of a third embodiment
of the present invention showing a side cross-sectional view of an
inductive-type write head in which is seen a main pole surrounded
by the shields of the present invention at its trailing edge but
not at its leading edge. Side shields are present, but not visible
in this view.
[0028] FIG. 3b is a schematic ABS view of the write head of FIG. 3a
showing the main pole tip surrounded by the shields of the present
invention at its trailing edge and sides.
[0029] FIG. 4a is a schematic representation of a fourth embodiment
of the present invention showing a side cross-sectional view of an
inductive-type write head in which is seen a main pole surrounded
by the shields of the present invention at its trailing edge and
leading edge. As in the second embodiment, a high B.sub.s seed
layer is below the trailing edge shield WS1.
[0030] FIG. 4b is a schematic ABS view of the write head of FIG. 4a
showing the main pole tip surrounded by the shields of the present
invention at its trailing edge, leading edge and sides.
[0031] FIGS. 5a-5h are a series of schematic illustrations
displaying the process flow that can be employed for fabricating
any of the embodiments illustrated above.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The preferred embodiment of the present invention is a
shielded pole structure for use within a perpendicular magnetic
recording (PMR) head, in which the shields are all formed of
materials having substantially the same physical characteristics
including the same material composition, the same hardness, the
same response (eg. removal rate) to processes such as ion beam
etching (IBE), chemical mechanical polishing (CMP), mechanical
lapping, such as the slider ABS lapping, and the same coefficient
of thermal expansion (CTE) as well as the same B.sub.s. By
"substantially the same," is meant the fact that the physical
characteristics (removal rate, CTE, B.sub.s) among the various
layers and their seeds may have small variations on, the order of
10%, of their respective nominal values. For example, a nominal B,
of 2.0 T could have +1-0.1 T.
[0033] Referring first to FIG. 1 a, there is shown a schematic side
cross-sectional view of a typical inductive type PMR write head
that is shielded in the manner provided by the present invention.
This view shows rectangular cross-sections of the inductive coil
windings as well as an upper yoke (16). The MP (10) is preferably
formed of material having a high B.sub.s ranging from 2.2 T to 2.4
T and can be formed of magnetic materials such as NiFe, CoFe,
CoNiFe, CoFePd, or CoFeN. The materials for the leading (LS) and
trailing (WS1; PP3) shields (LS (20)), (WS1 (30); PP3(16)),
including their seed layers, can also be made of any of these
alloys and it is preferred that the material have a B.sub.s ranging
from 1.5 T to 2.2 T. By using materials in these ranges, as
compared to prior art materials in the range of approximately 1.0
T, the thicknesses of the TS and SS can be reduced by half, which
will result in reduced pole tip protrusion (PTP) and improved
head-media spacing margin.
[0034] Referring next to FIG. 1b, there is shown the fabrication of
FIG. 1a from the ABS perspective. There can now be clearly seen the
symmetrically disposed side shields (SS) (40) and the side gap
layers (45) separating the outside edge of the main pole (10) from
the inner edge of the side shields. There is also clearly seen the
write gap layer (25) separating the upper surface of the main pole
(10) from the lower edge of the trailing shield, WS1 (30).
Correspondingly, a lower gap layer (15) separates the upper edge of
the leading shield (20) from the lower edge of the main pole (10).
In this embodiment, each shield layer has a seed layer (not shown)
that is formed of the same material as the shield layer itself.
[0035] Referring now to FIG. 2a, there is shown a schematic side
view of the same inductive type PMR write head of FIG. 1a that is
now shielded in the manner provided by a second embodiment of the
present invention. This embodiment differs from that described in
FIG. 1a by the presence of a high B.sub.s (>2.0T) seed layer
(35) that is patterned to be just wide enough (in its lateral
extent) to cover the write gap layer (25) as it extends laterally
between the inner edge surfaces of the two side shields (see FIG.
2b).
[0036] Referring to schematic FIG. 2b, there is shown the high
B.sub.s seed layer that is wide enough to cover the entire width
(lateral extent) of the write gap layer (25). The write gap layer
extends over the trailing edge of the main pole and the trailing
edge surfaces of the two side gaps (45). This higher B.sub.s seed
layer is first deposited along the entire write gap layer surface
and the upper surfaces of the two side shields (40), which have all
been properly planarized by a CMP process. The higher B.sub.s seed
layer is then patterned by an IBE to form an extremely narrow layer
as shown in the figure, extending only a short, lateral distance of
approximately +/-0.3 microns to either side of the main pole. The
use of a high B.sub.s seed layer in this position provides a high
B.sub.s within a region of the trailing edge shield, WS1, layer
precisely where it is required to improve the on-track field
gradient along the trailing edge side of the track. The advantages
of the identical shield layer and seed layer materials at all other
locations except for this small portion (35) still hold true, but
the additional advantages of the improved on-track field gradient
can also be obtained. It should be noted that, while strictly
speaking, the presence of the small high B.sub.s region of the
trailing edge shield might be said to contradict the designation of
the entire shield as being of the same material, the volume of
shield material with high B.sub.s is so small compared to the
volume of the entire shield, that all of the advantages and objects
of the invention that result from the same shield materials being
used are still met.
[0037] As in the embodiment of FIGS. 1a and 1b, the MP (10) is
preferably formed of material having a high B.sub.s ranging from
2.2 T to 2.4 T and can be formed of magnetic materials such as
NiFe, CoFe, CoNiFe, CoFePd, or CoFeN. The leading and trailing
shields (LS (20)), (WS1 (30)) materials, including their seed
layers, can also be made of any of these alloys and it is preferred
that the material have a B, ranging from 1.5 T to 2.2 T. By using
materials in these ranges, as compared to prior art materials in
the range of approximately 1.0 T, the thicknesses of the TS and SS
can be reduced by half, which will result in reduced pole tip
protrusion (PTP) and improved head-media spacing margin.
[0038] Referring next to FIG. 3a, there is shown the PMR write head
of FIGS. 1a and 2a, except that there is no leading shield in this
embodiment.
[0039] Referring now to FIG. 3b, there is shown the fabrication of
FIG. 3a from the ABS perspective where the leading edge shield is
no longer formed. There can now be clearly seen the trailing edge
shield (30), the write gap layer (35) that separates the main pole
(10) from the trailing edge shield, WS1, (30), the side shields
(SS) (40) and the two side gaps (45) separating the outside edge of
the main pole (10) from the inner edge of the side shields.
[0040] Referring next to FIG. 4a, there is shown schematically the
fabrication of FIG. 2a, except that there is no longer formed a
leading shield.
[0041] Referring next to FIG. 4b, there is shown schematically the
fabrication of FIG. 4a, from an ABS perspective, where the leading
edge shield is no longer formed. The "Hi-B, seed" layer, which is
the seed layer of of high B.sub.s material (35) is still present,
as are all other elements of FIG. 2b.
[0042] Referring now to schematic FIG. 5a, there is shown the first
of a series of process steps through which the embodiments of the
present invention can be fabricated. First, there is shown a
substrate (100), which can be a layer of non-magnetic metal such as
Ru or Ta, on which has been formed a dielectric layer (200) of
Al.sub.2O.sub.3 to a thickness of between approximately 0.2 and 0.6
microns. The dielectric layer will be used as a form in which to
plate the main pole of the write head.
[0043] Referring to schematic FIG. 5b, there is shown the formation
of a cavity in layer (200). The cavity is etched by a
photolithographic and etching process, which can be an IBE. The
shape of the cavity is congruent with the desired shape of the main
pole to be plated within it. As we shall see, below, in FIG. 5f,
the cavity can terminate at the substrate, which will enable the
formation of a shielded pole that lacks the leading edge shield, or
in this case, it can terminate within the body of the dielectric
layer, to leave space for the formation of a leading edge
shield.
[0044] The cavity is then lined on bottom and sides with a layer
(400) of non-magnetic metal such as Ru or Ta. A main pole (10) is
then plated within the lined cavity and the upper surface of the
fabrication is planarized by a CMP process or the like. The main
pole is preferably formed of material having a high B.sub.s,
ranging from 2.2 T to 2.4 T and it can be formed of magnetic
materials such as NiFe, CoFe, CoNiFe, CoFePd, or CoFeN.
[0045] Referring next to schematic FIG. 5c, there is shown the
fabrication of FIG. 5b, wherein the dielectric material layer
((200) in FIG. 5b), laterally disposed from the main pole (10) and
beneath the main pole is removed by a wet etch, leaving behind the
uncovered metallic substrate (100). The partially lined pole tip
(lined on its sides and bottom), as shown, floats over the
substrate, although it is supported behind the plane of the figure.
Although it is not shown in the figure, the upper surface of the
already plated pole can be protected by a mask during this wet etch
process so that it is not damaged.
[0046] Referring next to schematic FIG. 5d, there is shown the
fabrication of FIG. 5c in which any protective mask layer has been
removed and an atomic layer deposition (ALD) process has been used
to deposit a continuous gap layer (500), that is contiguous with
the partially lined main pole. This layer, which can be a layer of
Ru or Al.sub.2O.sub.3 will ultimately form (with its upper portion)
a write gap layer ((25) in FIG. 5e) between the trailing shield and
the main pole (10), side gap layers (45) in FIG. 5e) between the
side shields and the main pole and a leading gap layer ((15) in
FIG. 5e), between the leading shield and the main pole, if a
leading shield is formed.
[0047] Referring now to FIG. 5e, there is shown schematically the
result of a single plating step on the substrate (100) that forms
the completely surrounding and continuous shield configuration.
This shield configuration includes two side shield portions (40), a
trailing shield portion (30) and a leading shield portion (20). The
shield is separated from the main pole (10) by side gap layers
(45), a write gap layer (25) and a leading gap layer (15), when the
leading shield is present, as it is here.
[0048] As already noted, the MP (10) has been preferably formed of
material having a high B.sub.s, ranging from 2.2 T to 2.4 T and is
formed of magnetic materials such as NiFe, CoFe, CoNiFe, CoFePd, or
CoFeN. The materials forming the leading and trailing shields,
including their seed layers, can also be made of any of these
alloys and it is preferred that the material have a B, ranging from
1.5 T to. 2.2 T. The shield configuration is substantially of
uniform thickness (in the dimension normal to the ABS) because of
the use of the same material in all of its portions.
[0049] In an embodiment in which a leading edge shield is not to be
formed, the fabrication can proceed by substituting FIG. 5f for
FIG. 5a, forming the lined cavity for the MP plating in the layer
(200) of so that it directly contacts the substrate material (100)
(eg. the Ru or Ta metallic substrate).
[0050] In an alternative embodiment, where it is desired to utilize
a high B, seed layer as shown in FIGS. 2a and 2b and described
above, it can be deposited on the top surface of the write gap
layer at a point in the fabrication process before the completed
plating as shown in FIG. 5e. This can be done as follows. Referring
to FIG. 5g, there is shown the fabrication of FIG. 5e where the
plating of the leading and side shields has been terminated where
the side shields (40) have reached their correct height. At that
point, the upper surface of the fabrication is planarized. Then a
high B.sub.s seed layer is deposited over the upper surface and is
patterned using an IBE (ion beam etch) to remove outer (shaded)
portions (350) and to leave only a narrow central portion (35)
extending laterally to each side of the main pole by, for example,
+1-0.3 microns.
[0051] After the formation of the patterned seed layer (35) in FIG.
5g, the plating process is continued, as in FIG. 5h, to form the
trailing edge shield (30) above and continuous with the side
shields (40) and to thereby complete the surrounding shield
configuration. It is understood that in this embodiment, also, the
leading edge shield is optional.
[0052] As is understood by a person skilled in the art, the
preferred embodiment of the present invention is illustrative of
the present invention rather than limiting of the present
invention. Revisions and modifications may be made to methods,
materials, structures and dimensions employed in forming and
providing a PMR head having a main pole-tip surrounded by a
magnetic shield configuration formed of the same magnetic
materials, while still forming and providing such a PMR head and
pole and its method of formation in accord with the spirit and
scope of the present invention as defined by the appended
claims.
* * * * *