U.S. patent application number 14/946648 was filed with the patent office on 2017-05-25 for perpendicular magnetic recording media with lateral exchange control layer.
The applicant listed for this patent is HGST Netherlands B.V.. Invention is credited to Hiroyuki Katada, Miki Nishida, Masayoshi Shimizu, Shun Tonooka.
Application Number | 20170148477 14/946648 |
Document ID | / |
Family ID | 58719753 |
Filed Date | 2017-05-25 |
United States Patent
Application |
20170148477 |
Kind Code |
A1 |
Tonooka; Shun ; et
al. |
May 25, 2017 |
PERPENDICULAR MAGNETIC RECORDING MEDIA WITH LATERAL EXCHANGE
CONTROL LAYER
Abstract
A magnetic media having a lateral exchange control layer formed
on a magnetic oxide layer of a magnetic recording layer. A cap
layer is formed over the lateral exchange control layer. The
lateral exchange control layer can be an alloy comprising Co and
one or more of W, Ru, Hf, Ta, Nb and Fe. The lateral exchange
control layer has the highest magnetic saturation moment among all
the recording layers, and increases spacing between magnetic grains
(e.g. increased non-magnetic boundary width), thereby reducing
lateral exchange sigma. The presence of lateral exchange control
increases signal to noise ratio and reduces bit error rate and
increases areal density.
Inventors: |
Tonooka; Shun; (Odawara,
JP) ; Shimizu; Masayoshi; (Chigasaki, JP) ;
Nishida; Miki; (Fujisawa, JP) ; Katada; Hiroyuki;
(Odawara, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HGST Netherlands B.V. |
Amsterdam |
|
NL |
|
|
Family ID: |
58719753 |
Appl. No.: |
14/946648 |
Filed: |
November 19, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 5/656 20130101;
G11B 5/66 20130101 |
International
Class: |
G11B 5/66 20060101
G11B005/66; G11B 5/65 20060101 G11B005/65; G11B 5/73 20060101
G11B005/73 |
Claims
1. A magnetic media, comprising: a magnetically soft under-layer;
and a magnetic recording layer formed over the magnetically soft
under-layer, the magnetic recording layer further comprising: a
granular magnetic layer; a magnetic lateral exchange control layer
positioned on the granular magnetic layer; and a magnetic cap layer
formed over the lateral exchange control layer, wherein the
magnetic cap layer comprises magnetic grains separated by
non-magnetic grain boundaries; wherein the lateral exchange control
layer comprises an alloy that includes Co and at least one of W,
Ru, Hf, Ta, Nb and Fe.
2. The magnetic media as in claim 1, wherein the concentration of
non-magnetic material in the lateral exchange control layer is less
than 25 atomic percent.
3. The magnetic media as in claim 1, wherein the concentration of
non-magnetic material in the lateral exchange control layer is
greater than 10 atomic percent and less than 25 atomic percent.
4. The magnetic media as in claim 1, wherein the concentration of
one or more of W, Ru, Hf, Ta, Nb and Fe is at least 10 atomic
percent.
5. The magnetic media as in claim 1 wherein the lateral exchange
control layer has a higher magnetic saturation than the granular
magnetic layer or the cap layer.
6. The magnetic media as in claim 1 wherein the lateral exchange
control layer has a magnetic saturation of between 650 emu/cc and
800 emu/cc.
7. The magnetic media as in claim 1, wherein the lateral exchange
control layer contains no oxide.
8. The magnetic media as in claim 1, wherein the lateral exchange
control layer has a thickness of 0.1 nm to 0.5 nm.
9. The magnetic media as in claim 1, wherein the non-magnetic grain
boundaries have a thickness that gradually decreases with
increasing distance from the lateral exchange control layer.
10. The magnetic media as in claim 9 wherein the cap layer is at
least 1.0 nm thick and wherein the non-magnetic grain boundaries
have a width of at least 0.5 nm at a location 1.0 nm from the
lateral exchange control layer.
11. The magnetic media as in claim 1, wherein the lateral exchange
control layer is formed as islands on the granular magnetic
layer.
12. The magnetic media as in claim 1, wherein the lateral exchange
control layer is formed as islands separated by non-magnetic
boundary layers, and wherein the boundary layers at the location of
the lateral exchange control layer have a width of at least 1
nm.
13. A magnetic media, comprising: a magnetic recording layer formed
as a plurality of magnetic structures separated by non-magnetic
boundary layers extending vertically between the magnetic
structures, the magnetic structures comprising; a magnetic oxide
structure; a magnetic lateral exchange control layer having a
surface energy higher than that of Co causing it to be formed as an
island on the magnetic oxide structure; and a magnetic cap layer
formed over the magnetic oxide structure.
14. The magnetic media as in claim 13, wherein the lateral exchange
control layer is an alloy comprising Co and at least one of W, Ru,
Hf, Ta, Nb and Fe.
15. The magnetic media as in claim 13, wherein the lateral exchange
control layer has a higher magnetic saturation than the magnetic
oxide structure or the magnetic cap layer.
16. The magnetic media as in claim 13, wherein the lateral exchange
control layer has a magnetic saturation of between 650 emu/cc and
800 emu/cc.
17. The magnetic media as in claim 13, wherein the non-magnetic
boundary layers have a width of at least 1 nm at the location of
the lateral exchange control layer.
18. The magnetic media as in claim 13, wherein the non-magnetic
boundary layers have a width of at least 0.5 nm at a location
within the cap layer that is 1.0 nm above the lateral exchange
control layer.
19. A magnetic data recording system, comprising: a housing; a
magnetic media mounted within the housing; and a magnetic read
write transducer mounted within the housing for movement adjacent
to a surface of the magnetic media; wherein the magnetic media
comprises: a magnetically soft under-layer; a magnetic recording
layer formed over the magnetically soft under-layer, the magnetic
recording layer further comprising: a granular magnetic layer; a
magnetic lateral exchange control layer positioned on the granular
magnetic layer; and a magnetic cap layer formed over the lateral
exchange control layer wherein the magnetic cap layer comprises
magnetic grains separated by non-magnetic grain boundaries; wherein
the lateral exchange control layer comprises an alloy that includes
Co and at least one of W, Ru, Hf, Ta, Nb and Fe.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to magnetic data recording and
more particularly to a magnetic media having a lateral exchange
control layer in a magnetic recording layer for increased lateral
exchange and reduced magnetic exchange sigma.
BACKGROUND
[0002] At the heart of a computer is an assembly that is referred
to as a magnetic disk drive. The magnetic disk drive includes a
rotating magnetic disk, write and read heads that are suspended by
a suspension arm adjacent to a surface of the rotating magnetic
disk and an actuator that swings the suspension arm to place the
read and write heads over selected tracks on the rotating disk. The
read and write heads are directly located on a slider that has an
air bearing surface (ABS). The suspension arm biases the slider
into contact with the surface of the disk when the disk is not
rotating, but when the disk rotates air is swirled by the rotating
disk. When the slider rides on the air bearing, the write and read
heads are employed for writing magnetic impressions to and reading
magnetic impressions from the rotating disk. The read and write
heads are connected to processing circuitry that operates according
to a computer program to implement the writing and reading
functions.
[0003] The write head includes at least one coil, a write pole and
one or more return poles. When current flows through the coil, a
resulting magnetic field causes a magnetic flux to flow through the
coil, which results in a magnetic write field emitting from the tip
of the write pole. This magnetic field is sufficiently strong that
it locally magnetizes a portion of the adjacent magnetic media,
thereby recording a bit of data. The write field then, travels
through a magnetically soft under-layer of the magnetic medium to
return to the return pole of the write head.
[0004] A magnetoresistive sensor such as a Giant Magnetoresistive
(GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can
be employed to read a magnetic signal from the magnetic media. The
magnetoresistive sensor has an electrical resistance that changes
in response to an external magnetic field. This change in
electrical resistance can be detected by processing circuitry in
order to read magnetic data from the magnetic media.
[0005] In a perpendicular magnetic recording system, the magnetic
media on which data is written can be formed with a soft magnetic
under-layer and a magnetic recording layer formed over the soft
magnetic recording layer. The magnetic recording layer can be
formed as individual magnetic grains that are separated by
non-magnetic oxide layers. In order to increase data density, it is
desirable to decrease the size of the magnetic grains. However
certain engineering constraints have made it difficult to further
reduce the size of magnetic grains and increase the magnetic data
density while also maintaining high signal resolution and data
integrity.
SUMMARY
[0006] The present invention provides a magnetic data recording
media that includes a magnetically soft under-layer and a magnetic
recording layer formed over the magnetically soft under-layer. The
magnetic recording layer includes a granular magnetic layer, a
lateral exchange control layer positioned on the granular magnetic
layer and a cap layer formed over the lateral exchange control
layer, wherein the lateral exchange control layer comprises an
alloy that includes Co and at least one of W, Ru, Hf, Ta, Nb and
Fe.
[0007] The presence of the lateral exchange control layer
advantageously increases the magnetic saturation moment while also
increasing the non-magnetic boundary width. This provides reduced
bit error rate and also increased signal to noise ratio, thereby
allowing for increased areal density.
[0008] The lateral exchange control layer can be formed as islands
over magnetic grains of the granular magnetic layer. The material
of the lateral exchange control layer has a high surface energy
which causes it to deposit on the individual grains of the granular
magnetic layer, but not on the non-magnetic boundary material.
[0009] These and other features and advantages of the invention
will be apparent upon reading of the following detailed description
of the embodiments taken in conjunction with the figures in which
like reference numeral indicate like elements throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a fuller understanding of the nature and advantages of
this invention, as well as the preferred mode of use, reference
should be made to the following detailed description read in
conjunction with the accompanying drawings which are not to
scale.
[0011] FIG. 1 is a schematic illustration of a disk drive system in
which the invention might be embodied;
[0012] FIG. 2 is cross-sectional view of a portion of a magnetic
media;
[0013] FIG. 3 is an enlarged view of a portion of the magnetic
media showing individual grains structures and individual islands
of lateral exchange control material therein;
[0014] FIG. 4 is a view similar to that of FIG. 3 showing an
alternate possible embodiment;
[0015] FIG. 5 is a graph illustrating a relationship between
lateral exchange coupling and grain boundary width;
[0016] FIG. 6 is a graph showing cluster size sigma vs. cluster
size in nm;
[0017] FIG. 7 is a table illustrating performance parameters for
various magnetic media with and without a lateral exchange
layer;
[0018] FIG. 8 is a graph showing Hc vs. thickness of a lateral
exchange control layer;
[0019] FIG. 9 is a graph illustrating a relationship between Hn and
lateral exchange control layer thickness;
[0020] FIG. 10 is a graph illustrating a relationship between Hs
and lateral exchange control layer thickness;
[0021] FIG. 11 is a graph illustrating a relationship between
switching field distribution (SFD) and lateral exchange coupling
layer thickness;
[0022] FIG. 12 is a graph illustrating a relationship between bit
error rate and lateral exchange control layer thickness for various
media with and without a lateral exchange control layer; and
[0023] FIG. 13 is a graph illustrating a relationship between
signal to noise ratio and lateral exchange coupling layer thickness
for various media with and without a lateral exchange control
layer.
DETAILED DESCRIPTION
[0024] The following description is of the best embodiments
presently contemplated for carrying out this invention. This
description is made for the purpose of illustrating the general
principles of this invention and is not meant to limit the
inventive concepts claimed herein.
[0025] Referring now to FIG. 1, there is shown a disk drive 100.
The disk drive 100 includes a housing 101. At least one rotatable
magnetic disk 112 is supported on a spindle 114 and rotated by a
disk drive motor 118. The magnetic recording on each disk may be in
the form of annular patterns of concentric data tracks (not shown)
on the magnetic disk 112.
[0026] At least one slider 113 is positioned near the magnetic disk
112, each slider 113 supporting one or more magnetic head
assemblies 121. As the magnetic disk rotates, slider 113 moves in
and out over the disk surface 122 so that the magnetic head
assembly 121 can access different tracks of the magnetic disk where
desired data are written. Each slider 113 is attached to an
actuator arm 119 by way of a suspension 115. The suspension 115
provides a slight spring force which biases the slider 113 against
the disk surface 122. Each actuator arm 119 is attached to an
actuator means 127. The actuator means 127 as shown in FIG. 1 may
be a voice coil motor (VCM). The VCM comprises a coil movable
within a fixed magnetic field, the direction and speed of the coil
movements being controlled by the motor current signals supplied by
the controller 129.
[0027] During operation of the disk storage system, the rotation of
the magnetic disk 112 generates an air bearing between the slider
113 and the disk surface 122, which exerts an upward force or lift
on the slider. The air bearing thus counter-balances the slight
spring force of the suspension 115 and supports the slider 113 off
and slightly above the disk surface by a small, substantially
constant spacing during normal operation.
[0028] The various components of the disk storage system are
controlled in operation by control signals generated by control
unit 129, such as access control signals and internal clock
signals. Typically, the control unit 129 comprises logic control
circuits, and a microprocessor. The control unit 129 generates
control signals to control various system operations such as drive
motor control signals on line 123 and head position and seek
control signals on line 128. The control signals on line 128
provide the desired current profiles to optimally move and position
the slider 113 to the desired data track on the media 112. Write
and read signals are communicated to and from write and read heads
121 by way of recording channel 125.
[0029] FIG. 2 shows a cross section of a portion of the magnetic
media 112. As shown in FIG. 2, the magnetic media 112 includes a
substrate such as glass and an adhesion layer 204 formed on the
substrate 202. A magnetically soft under-layer 206 is formed on the
adhesion layer 204. An exchange break layer 208 is formed over the
magnetically soft under-layer 208, and a magnetic recording layer
218 is formed over the exchange break layer. The adhesion layer 204
can be a Ni alloy, and the magnetically soft under-layer 206 can be
an alloy of Co, Fe and some other component X. The exchange break
layer 208 can be a non-magnetic material such as Ru or Ru alloy and
is sufficiently thick to prevent magnetic exchange coupling between
the soft magnetic under-layer 206 and the magnetic recording layer
218.
[0030] The magnetic recording layer includes a granular oxide layer
210 and a non-oxide top layer 219 formed over the granular oxide
layer 210. The non-oxide top layer 219 includes a novel lateral
exchange control layer 212 formed over the magnetic oxide layer
210, and a magnetic cap layer 214 formed over the lateral exchange
control layer 212. The magnetic recording layer and its grain
structure are shown in greater detail in FIG. 3. In FIG. 3 it can
be seen that the granular oxide layer 210 includes magnetic grains
302 that are separated from one another by non-magnetic oxide
boundary layers 304.
[0031] It can also be seen in FIG. 3 that the lateral exchange
control layer 212 is formed as islands over the magnetic oxide
grains 302, with little or no lateral exchange layer 212 being
formed in or on the magnetic oxide boundary layer 304. This
advantageously results from the high surface energy of the lateral
exchange control layer. 212. To this effect, the lateral exchange
control layer 212 includes at least 10% of high surface energy
elements which can include one or more of W, Ru, Hf, Ta, Nb, or Fe.
The lateral exchange control layer has high magnetic saturation
moment and thereby advantageously increases the lateral (side to
side) exchange coupling. The lateral exchange control layer 212
preferably has a higher magnetic saturation moment than the
granular magnetic layer 210 or the cap layer 214. More preferably,
the lateral exchange control layer 212 has a magnetic saturation
moment of between 650 emu/cc and 800 emu/cc. The lateral exchange
control layer can be formed of an alloy of Co or Fe and X, where X
is non-magnetic material, and wherein the concentration of X is
less than 25 atomic percent. In addition, the presence of the
lateral exchange layer 212 also advantageously increases the width
of the non-magnetic oxide boundary in the location between the
grains of the cap layer 214. As a result, the lateral exchange
control layer reduces magnetic exchange sigma. The non-magnetic
boundary 304 can have a width w at a height h from the top of the
lateral exchange control layer 212, where w is greater than or
equal to 0.5 nm and h is greater than or equal to 1.0 nm. The
boundary layers 304 at the location of the lateral exchange control
layer preferably have a width of at least 1 nm.
[0032] FIG. 4 illustrates another possible embodiment of a magnetic
media 400 having a slightly modified magnetic oxide layer 210. The
magnetic oxide layer 210 includes one or more vertical exchange
control layers. In this case, the magnetic oxide layer includes
three vertical exchange control layers 402a, 402b, 402c, that
divide the magnetic oxide into sections 302a, 302b, 302c, 302d. The
vertical exchange control layers 402a-c control a vertical exchange
coupling. The vertical exchange coupling can be controlled by
changing the thickness of the vertical exchange control layers.
This vertical exchange coupling is fundamentally different from the
lateral exchange coupling that is enhanced by the presence of the
lateral exchange control layer 212. Whereas the vertical exchange
coupling provided by the layers 402a-c is oriented in a vertical
direction (up and down in FIG. 4), the exchange coupling enhanced
by the lateral exchange control layer is in a lateral direction
(side to side in FIG. 4). The advantages provided by the lateral
exchange control layer 212 will be better understood in light of
the following discussion with reference to FIGS. 5-14.
[0033] FIG. 5 shows a graph illustrating a relationship between
lateral exchange coupling and grain boundary width. In FIG. 5, the
curve 502 shows this relationship for a media that does not have
the lateral exchange control layer 212 of FIGS. 2-4. Dashed line
506 shows a level of lateral exchange coupling desired for good
writeability and thermal stability of recorded data. A magnetic
media has an inevitable amount of variation in non-magnetic
boundary width. This variation in non-magnetic boundary width is
represented by the horizontal distance 508a for line 502, and 508b
for line 504. As can be seen, the variation in boundary width
results in a corresponding variation lateral exchange coupling,
referred to as lateral exchange sigma, which is represented by
vertical distances 510a for line 502 and 510b for line 504.
[0034] For line 502 (the case without the lateral exchange control
layer) it can be seen that, achieving the desired amount of lateral
exchange coupling puts the media in a relatively steep portion of
the curve, causing a very high lateral exchange coupling sigma for
a given amount of boundary layer thickness variation. It is
desirable to have a low amount of lateral exchange sigma, and this
could be achieved by increasing the grain boundary width. However,
this would result in an unacceptably low lateral exchange coupling,
resulting in poor writeability and thermal stability.
[0035] For line 504 however, the presence of the lateral exchange
control layer increases the average saturation magnetization Ms of
non-oxide top layer 219 (FIG. 2-4) because the lateral exchange
control layer has high Ms, thereby effectively raising the entire
curve 504. This means that grain boundary width can be increased
while still achieving the desired amount of lateral exchange
coupling (line 506). Therefore, this desired location is at a
flatter portion of the curve 504. This leads to a reduced lateral
exchange sigma 510b for the same given grain boundary width
variation 508b. Therefore, the presence of the lateral exchange
control layer 212 (FIGS. 2-4) allows for an advantageous reduction
in lateral exchange sigma due to the increased Ms of the non-oxide
top layer 219 (FIGS. 2-4).
[0036] This effect is further verified by FIG. 6, which shows
cluster size sigma verses cluster size in nm. The cluster size
sigma correlates with lateral exchange sigma. Region 602 shows the
cluster size sigma for a magnetic media having no lateral exchange
control layer and region 604 shows the cluster size sigma for a
magnetic media having a lateral exchange control layer as described
above. As can be seen, cluster size sigma is reduced while
maintaining the cluster size for the media having the lateral
exchange control layer.
[0037] The table of FIG. 7 shows experimental results of test
samples for a sample having no lateral exchange control layer (row
702) as compared with two samples having a lateral exchange control
layer as described above (rows 704, 706). Column 708 shows the
areal density capability in Gb/in.sup.2 for each of the samples. As
can be seen in column 710, the presence of the lateral exchange
control layer resulted in a data density gain of 1.2 percent for
the sample of row 704 and 2.5 percent for the sample of row 706, as
compared with the sample having no lateral exchange control layer
(row 702). Column 712 shows the linear density in bits per inch. As
can be seen, the presence of the lateral exchange control layer
resulted in an increase in linear data density.
[0038] In order to form a lateral exchange control layer 212 (FIG.
2) having a high surface energy as well as a high saturation
magnetization, it becomes advantageous to employ certain alloying
elements to an alloy containing Co. A lateral exchange control
layer includes at least one element which has high surface energy.
From this point of view, Fe, Nb, Ta, Hf, Ru and W are suitable to
be included in the lateral exchange control layer 212 because the
surface energy of Fe, Nb, Ta, Hf, Ru, and W is higher than that of
Co. The concentration of high surface energy elements, Fe, Nb, Ta,
Hf, Ru, and W should be more than 10% to realize advantageously
high enough surface energy for the lateral exchange control
layer.
[0039] In order to exhibit high Ms as well as a high surface
energy, the lateral exchange control layer can be formed of an
alloy of Co or Fe and X, where X is a non-magnetic material, and
wherein the concentration of X is less than 25%. If the
concentration of non-magnetic material in the lateral exchange
control layer is more than 25%, magnetic saturation moment will not
be sufficiently high. A specific preferable example of an
advantageous alloy for use as the lateral exchange layer is
Co--Cr--Ru--W where the combined concentration of Ru and W is at
least 10 atomic percent and the combined concentration of
non-magnetic elements (i.e. Ru, Cr and W) is less than 25 atomic
percent.
[0040] Therefore, the lateral exchange control layer includes at
least 10 atomic percent of an material having a high surface
energy, which can be one or more of W, Ru, Hf, Ta, Nb, and Fe, and
also includes a non-magnetic material in a concentration of up to
25 atomic percent. More preferably, the concentration of
non-magnetic material is more than 10% because it is difficult to
sputter deposit thin films if the concentration of non-magnetic
material is less than 10%. The capping layer 214 (FIGS. 2-4) can be
formed of an alloy of Co, Cr, Pt and B.
[0041] FIGS. 8-11 graphically show how various magnetic properties
of the recording media vary with the thickness of the lateral
exchange layer 212 (FIG. 2). FIG. 8 shows that magnetic coercivity
Hc drops with increasing lateral exchange layer thickness. FIG. 9
shows that Hn actually rises slightly with increasing exchange
layer thickness. The increase in Hn indicates an increase in
lateral exchange coupling. FIG. 10 shows that Hs decreases with
increasing lateral exchange layer thickness, and FIG. 11 shows that
the switching field distribution (SFD) also decreases with
increasing lateral exchange layer thickness. All behaviors of the
magnetic properties described above indicate that lateral exchange
coupling increases with increasing lateral exchange control layer
thickness.
[0042] FIG. 12 shows a graph of trim Bit Error Rate (BER) as a
function of lateral exchange control layer thickness. As those
skilled in the art will appreciate, a lower bit error rate is
desirable and translates into an advantageous increase in areal
data density. The horizontal line 1302 represents the bit error
rate for a media having no lateral exchange control layer at all.
Lines 1304 and 1306 represent the bit error rate for two different
samples of media having the above described lateral exchange
control layer. Line 1304 represents the bit error rate for a media
having a 2.5 nm thick cap layer 214 (FIGS. 2-4), and line 1306
represents the bit error rate for a media having a 3.5 nm thick cap
layer 214 (FIGS. 2-4). As can be seen, the bit error rate is
affected by thickness of the cap layer 214 and the thickness of the
exchange control layer 212 (FIGS. 2-4). The bit error rate drops
with increasing lateral exchange control layer thickness up to a
thickness of about 0.15 nm for the media of line 1304 and about 0.2
nm for the case of line 1306, and then gradually begins to increase
again. It can be seen from FIG. 12 that a significant reduction in
bit error rate can be achieved through the use of a lateral
exchange control layer, especially when the lateral exchange
control layer is at an optimal thickness.
[0043] FIG. 13 shows the how the signal to noise ratio varies with
varying thickness of lateral exchange control layer. As those
skilled in the art will appreciate, a high signal to noise ratio is
very desirable. Line 1402 shows the signal to noise ratio when no
lateral exchange control layer at all is used. Line 1404 shows how
the signal to noise ratio varies with lateral exchange control
layer thickness for a media having a 2.5 nm thick cap layer 214
(FIGS. 2-4). Line 1406 shows how the signal to noise ratio varies
with lateral exchange control layer thickness for a media having a
3.5 nm thick cap layer 214 (FIGS. 2-4). As can be seen the presence
of the lateral exchange control layer, especially at optimal
thickness, provides a significant increase in signal to noise
ratio.
[0044] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only and not limitation. Other embodiments falling within
the scope of the invention may also become apparent to those
skilled in the art. Thus, the breadth and scope of the invention
may also become apparent to those skilled in the art. Thus, the
breadth and scope of the inventions should not be limited by any of
the above-described exemplary embodiments, but should be defined
only in accordance with the following claims and their
equivalents.
* * * * *