U.S. patent application number 15/156035 was filed with the patent office on 2017-11-16 for polycrystalline dielectric coating for cobalt iron alloy thin films.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Robert G. Biskeborn, Calvin S. Lo, Teya Topuria.
Application Number | 20170330588 15/156035 |
Document ID | / |
Family ID | 60295448 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170330588 |
Kind Code |
A1 |
Biskeborn; Robert G. ; et
al. |
November 16, 2017 |
POLYCRYSTALLINE DIELECTRIC COATING FOR COBALT IRON ALLOY THIN
FILMS
Abstract
In one general embodiment, an apparatus includes a magnetic
transducer having a CoFe layer and an at least partially
polycrystalline alumina-containing coating on a media facing side
of the CoFe layer. A graded layer comprising Co, Fe, Al and oxygen
is positioned between the alumina-containing coating and the CoFe
layer, wherein a ratio of Co to Al in the graded layer decreases
from the CoFe layer toward the alumina-containing coating. In
another general embodiment, an apparatus includes a magnetic
transducer having a CoFe layer and an at least partially
polycrystalline alumina-containing coating on a media facing side
of the CoFe layer. CoFe-oxide crystallites are present at an
interface region of the CoFe layer and the alumina-containing
coating and the CoFe layer. Fabrication methods are also
presented.
Inventors: |
Biskeborn; Robert G.;
(Hollister, CA) ; Lo; Calvin S.; (Saratoga,
CA) ; Topuria; Teya; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
60295448 |
Appl. No.: |
15/156035 |
Filed: |
May 16, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 5/00813 20130101;
G11B 5/255 20130101; G11B 5/1871 20130101; G11B 5/3106
20130101 |
International
Class: |
G11B 5/21 20060101
G11B005/21; G11B 5/187 20060101 G11B005/187; G11B 5/008 20060101
G11B005/008 |
Claims
1. An apparatus, comprising: a magnetic transducer having a CoFe
layer and an at least partially polycrystalline alumina-containing
coating on a media facing side of the CoFe layer, wherein a graded
layer comprising Co, Fe, Al and oxygen is positioned between the
alumina-containing coating and the CoFe layer, wherein a ratio of
Co to Al in the graded layer decreases from the CoFe layer toward
the alumina-containing coating.
2. The apparatus as recited in claim 1, wherein the
alumina-containing coating is comprised primarily of alumina,
wherein the alumina-containing coating also includes cobalt oxide
and iron oxide.
3. The apparatus as recited in claim 1, wherein the graded layer
forms an interface between the CoFe layer and the
alumina-containing coating.
4. The apparatus as recited in claim 1, wherein the graded layer is
partially crystalline.
5. The apparatus as recited in claim 1, wherein the
alumina-containing coating is formed on an entire area of the media
facing side of the magnetic transducer.
6. The apparatus as recited in claim 1, comprising a write
transducer comprised of at least a Co, Fe, and Ni alloy
portion.
7. The apparatus as recited in claim 1, comprising a read
transducer shield comprised of at least a Co, Fe, and Ni alloy
portion.
8. The apparatus as recited in claim 1, wherein a thickness of the
graded layer is at least 3 nanometers.
9. The apparatus as recited in claim 1, wherein a thickness of the
graded layer is less than 50 nanometers and greater than 0
nanometers.
10. The apparatus as recited in claim 1, further comprising: a
drive mechanism for passing a magnetic medium over the transducer;
and a controller electrically coupled to the transducer.
11. An apparatus, comprising: a magnetic transducer having a CoFe
layer and an at least partially polycrystalline alumina-containing
coating on a media facing side of the CoFe layer, wherein
CoFe-oxide crystallites are present at an interface region of the
CoFe layer and the alumina-containing coating and the CoFe
layer.
12. The apparatus as recited in claim 11, wherein a graded layer
comprising Co, Fe, Al and oxygen is positioned between the
alumina-containing coating and the CoFe layer, wherein a ratio of
Co to Al in the graded layer decreases from the CoFe layer toward
the alumina-containing coating.
13. The apparatus as recited in claim 12, wherein the graded layer
is partially crystalline.
14. The apparatus as recited in claim 12, wherein a thickness of
the graded layer is at least 3 nanometers.
15. The apparatus as recited in claim 12, wherein a thickness of
the graded layer is less than 50 nanometers and greater than 0
nanometers.
16. The apparatus as recited in claim 11, wherein the
alumina-containing coating is comprised primarily of alumina,
wherein the alumina-containing coating also includes cobalt oxide
and iron oxide.
17. The apparatus as recited in claim 11, wherein the
alumina-containing coating is formed on an entire area of the media
facing side of the magnetic transducer.
18. The apparatus as recited in claim 11, further comprising: a
drive mechanism for passing a magnetic medium over the transducer;
and a controller electrically coupled to the transducer.
19. A method for fabricating the magnetic transducer of claim 1,
the method comprising: performing a reducing operation for reducing
a native oxide along a surface of the CoFe layer of the magnetic
transducer; after performing the reducing operation, performing an
oxidation operation for oxidizing the surface of the CoFe layer;
and after performing the oxidation operation, forming the layer of
at least partially crystalline alumina-containing coating on the
oxidized surface of the CoFe layer.
20. The method as recited in claim 19, wherein the oxidized surface
of the CoFe layer has CoFe-oxide crystallites therein.
Description
BACKGROUND
[0001] The present invention relates to data storage systems, and
more particularly, this invention relates to polycrystalline
dielectric coating for cobalt iron alloy thin films useable with
magnetic heads.
[0002] In magnetic storage systems, magnetic transducers read data
from and write data onto magnetic recording media. Data is written
on the magnetic recording media by moving a magnetic recording
transducer to a position over the media where the data is to be
stored. The magnetic recording transducer then generates a magnetic
field, which encodes the data into the magnetic media. Data is read
from the media by similarly positioning the magnetic read
transducer and then sensing the magnetic field of the magnetic
media. Read and write operations may be independently synchronized
with the movement of the media to ensure that the data can be read
from and written to the desired location on the media.
[0003] An important and continuing goal in the data storage
industry is that of increasing the density of data stored on a
medium. For tape storage systems, that goal has led to increasing
the track and linear bit density on recording tape, and decreasing
the thickness of the magnetic tape medium. However, the development
of small footprint, higher performance tape drive systems has
created various problems in the design of a tape head assembly for
use in such systems.
[0004] In a tape drive system, the drive moves the magnetic tape
over the surface of the tape head at high speed. Usually the tape
head is designed to minimize the spacing between the head and the
tape. The spacing between the magnetic head and the magnetic tape
is crucial and so goals in these systems are to have the recording
gaps of the transducers, which are the source of the magnetic
recording flux in near contact with the tape to effect writing
sharp transitions, and to have the read elements in near contact
with the tape to provide effective coupling of the magnetic field
from the tape to the read elements.
SUMMARY
[0005] An apparatus according to one embodiment includes a magnetic
transducer having a CoFe layer and an at least partially
polycrystalline alumina-containing coating on a media facing side
of the CoFe layer. A graded layer comprising Co, Fe, Al and oxygen
is positioned between the alumina-containing coating and the CoFe
layer, wherein a ratio of Co to Al in the graded layer decreases
from the CoFe layer toward the alumina-containing coating.
[0006] An apparatus according to another embodiment includes a
magnetic transducer having a CoFe layer and an at least partially
polycrystalline alumina-containing coating on a media facing side
of the CoFe layer. CoFe-oxide crystallites are present at an
interface region of the CoFe layer and the alumina-containing
coating and the CoFe layer.
[0007] A method according to yet another embodiment includes
performing a reducing operation for reducing a native oxide along a
surface of a CoFe layer of a magnetic transducer. After performing
the reducing operation, an oxidation operation for oxidizing the
surface of the CoFe layer is performed. After performing the
oxidation operation, a layer of at least partially crystalline
alumina is formed on the oxidized surface of the CoFe layer.
[0008] Any of these embodiments may be implemented in a magnetic
data storage system such as a tape drive system, which may include
a magnetic head, a drive mechanism for passing a magnetic medium
(e.g., recording tape) over the magnetic head, and a controller
electrically coupled to the magnetic head.
[0009] Other aspects and embodiments of the present invention will
become apparent from the following detailed description, which,
when taken in conjunction with the drawings, illustrate by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is a schematic diagram of a simplified tape drive
system according to one embodiment.
[0011] FIG. 1B is a schematic diagram of a tape cartridge according
to one embodiment.
[0012] FIG. 2 illustrates a side view of a flat-lapped,
bi-directional, two-module magnetic tape head according to one
embodiment.
[0013] FIG. 2A is a tape bearing surface view taken from Line 2A of
FIG. 2.
[0014] FIG. 2B is a detailed view taken from Circle 2B of FIG.
2A.
[0015] FIG. 2C is a detailed view of a partial tape bearing surface
of a pair of modules.
[0016] FIG. 3 is a partial tape bearing surface view of a magnetic
head having a write-read-write configuration.
[0017] FIG. 4 is a partial tape bearing surface view of a magnetic
head having a read-write-read configuration.
[0018] FIG. 5 is a side view of a magnetic tape head with three
modules according to one embodiment where the modules all generally
lie along about parallel planes.
[0019] FIG. 6 is a side view of a magnetic tape head with three
modules in a tangent (angled) configuration.
[0020] FIG. 7 is a side view of a magnetic tape head with three
modules in an overwrap configuration.
[0021] FIG. 8A is a partial cross sectional view of a magnetic head
according to one embodiment.
[0022] FIG. 8B is a detailed view taken from Circle 8B of FIG.
8A.
[0023] FIG. 9 is a flow diagram of a process according to one
embodiment.
[0024] FIG. 10A is a magnified view of amorphous Co oxide and Fe
oxide at a CoFe surface of a comparative example.
[0025] FIG. 10B is a magnified view of a portion of FIG. 10A.
[0026] FIG. 10C is an electron energy loss spectroscopy (EELS) scan
across the layer interface shown in FIGS. 10A and 10B.
[0027] FIG. 11A is a magnified view of a comparative example.
[0028] FIG. 11B is a magnified view of a portion of FIG. 11A.
[0029] FIG. 11C is an electron energy loss spectroscopy (EELS) scan
across the layer interface shown in FIGS. 11A and 11B.
[0030] FIG. 12A is a magnified view of an embodiment of the present
invention.
[0031] FIG. 12B is a magnified view of a portion of FIG. 12A.
[0032] FIG. 12C is an electron energy loss spectroscopy (EELS) scan
across the layer interface shown in FIGS. 12A and 12B.
[0033] FIG. 13A is a Transmission Electron Microscopy (TEM) image
of an embodiment of the present invention.
[0034] FIG. 13B is a diffractogram of the structure shown in FIG.
13A.
DETAILED DESCRIPTION
[0035] The following description is made for the purpose of
illustrating the general principles of the present invention and is
not meant to limit the inventive concepts claimed herein. Further,
particular features described herein can be used in combination
with other described features in each of the various possible
combinations and permutations.
[0036] Unless otherwise specifically defined herein, all terms are
to be given their broadest possible interpretation including
meanings implied from the specification as well as meanings
understood by those skilled in the art and/or as defined in
dictionaries, treatises, etc.
[0037] It must also be noted that, as used in the specification and
the appended claims, the singular forms "a," "an" and "the" include
plural referents unless otherwise specified.
[0038] The following description discloses several preferred
embodiments of magnetic storage systems, as well as operation
and/or component parts thereof.
[0039] In one general embodiment, an apparatus includes a magnetic
transducer having a CoFe layer and an at least partially
polycrystalline alumina-containing coating on a media facing side
of the CoFe layer. A graded layer comprising Co, Fe, Al and oxygen
is positioned between the alumina-containing coating and the CoFe
layer, wherein a ratio of Co to Al in the graded layer decreases
from the CoFe layer toward the alumina-containing coating.
[0040] In another general embodiment, an apparatus includes a
magnetic transducer having a CoFe layer and an at least partially
polycrystalline alumina-containing coating on a media facing side
of the CoFe layer. CoFe-oxide crystallites are present at an
interface region of the CoFe layer and the alumina-containing
coating and the CoFe layer.
[0041] In yet another general embodiment, a method includes
performing a reducing operation for reducing a native oxide along a
surface of a CoFe layer of a magnetic transducer. After performing
the reducing operation, an oxidation operation for oxidizing the
surface of the CoFe layer is performed. After performing the
oxidation operation, a layer of at least partially crystalline
alumina is formed on the oxidized surface of the CoFe layer.
[0042] FIG. 1A illustrates a simplified tape drive 100 of a
tape-based data storage system, which may be employed in the
context of the present invention. While one specific implementation
of a tape drive is shown in FIG. 1A, it should be noted that the
embodiments described herein may be implemented in the context of
any type of tape drive system.
[0043] As shown, a tape supply cartridge 120 and a take-up reel 121
are provided to support a tape 122. One or more of the reels may
form part of a removable cartridge and are not necessarily part of
the system 100. The tape drive, such as that illustrated in FIG.
1A, may further include drive motor(s) to drive the tape supply
cartridge 120 and the take-up reel 121 to move the tape 122 over a
tape head 126 of any type. Such head may include an array of
readers, writers, or both.
[0044] Guides 125 guide the tape 122 across the tape head 126. Such
tape head 126 is in turn coupled to a controller 128 via a cable
130. The controller 128, may be or include a processor and/or any
logic for controlling any subsystem of the drive 100. For example,
the controller 128 typically controls head functions such as servo
following, data writing, data reading, etc. The controller 128 may
include at least one servo channel and at least one data channel,
each of which include data flow processing logic configured to
process and/or store information to be written to and/or read from
the tape 122. The controller 128 may operate under logic known in
the art, as well as any logic disclosed herein, and thus may be
considered as a processor for any of the descriptions of tape
drives included herein, in various embodiments. The controller 128
may be coupled to a memory 136 of any known type, which may store
instructions executable by the controller 128. Moreover, the
controller 128 may be configured and/or programmable to perform or
control some or all of the methodology presented herein. Thus, the
controller 128 may be considered to be configured to perform
various operations by way of logic programmed into one or more
chips, modules, and/or blocks; software, firmware, and/or other
instructions being available to one or more processors; etc., and
combinations thereof.
[0045] The cable 130 may include read/write circuits to transmit
data to the head 126 to be recorded on the tape 122 and to receive
data read by the head 126 from the tape 122. An actuator 132
controls position of the head 126 relative to the tape 122.
[0046] An interface 134 may also be provided for communication
between the tape drive 100 and a host (internal or external) to
send and receive the data and for controlling the operation of the
tape drive 100 and communicating the status of the tape drive 100
to the host, all as will be understood by those of skill in the
art.
[0047] FIG. 1B illustrates an exemplary tape cartridge 150
according to one embodiment. Such tape cartridge 150 may be used
with a system such as that shown in FIG. 1A. As shown, the tape
cartridge 150 includes a housing 152, a tape 122 in the housing
152, and a nonvolatile memory 156 coupled to the housing 152. In
some approaches, the nonvolatile memory 156 may be embedded inside
the housing 152, as shown in FIG. 1B. In more approaches, the
nonvolatile memory 156 may be attached to the inside or outside of
the housing 152 without modification of the housing 152. For
example, the nonvolatile memory may be embedded in a self-adhesive
label 154. In one preferred embodiment, the nonvolatile memory 156
may be a Flash memory device, ROM device, etc., embedded into or
coupled to the inside or outside of the tape cartridge 150. The
nonvolatile memory is accessible by the tape drive and the tape
operating software (the driver software), and/or other device.
[0048] By way of example, FIG. 2 illustrates a side view of a
flat-lapped, bi-directional, two-module magnetic tape head 200
which may be implemented in the context of the present invention.
As shown, the head includes a pair of bases 202, each equipped with
a module 204, and fixed at a small angle a with respect to each
other. The bases may be "U-beams" that are adhesively coupled
together. Each module 204 includes a substrate 204A and a closure
204B with a thin film portion, commonly referred to as a "gap" in
which the readers and/or writers 206 are formed. In use, a tape 208
is moved over the modules 204 along a media (tape) bearing surface
209 in the manner shown for reading and writing data on the tape
208 using the readers and writers. The wrap angle .theta. of the
tape 208 at edges going onto and exiting the flat media support
surfaces 209 are usually between about 0.1 degree and about 3
degrees.
[0049] The substrates 204A are typically constructed of a wear
resistant material, such as a ceramic. The closures 204B may be
made of the same or similar ceramic as the substrates 204A.
[0050] The readers and writers may be arranged in a piggyback or
merged configuration. An illustrative piggybacked configuration
comprises a (magnetically inductive) writer transducer on top of
(or below) a (magnetically shielded) reader transducer (e.g., a
magnetoresistive reader, etc.), wherein the poles of the writer and
the shields of the reader are generally separated. An illustrative
merged configuration comprises one reader shield in the same
physical layer as one writer pole (hence, "merged"). The readers
and writers may also be arranged in an interleaved configuration.
Alternatively, each array of channels may be readers or writers
only. Any of these arrays may contain one or more servo track
readers for reading servo data on the medium.
[0051] FIG. 2A illustrates the tape bearing surface 209 of one of
the modules 204 taken from Line 2A of FIG. 2. A representative tape
208 is shown in dashed lines. The module 204 is preferably long
enough to be able to support the tape as the head steps between
data bands.
[0052] In this example, the tape 208 includes 4 to 32 data bands,
e.g., with 16 data bands and 17 servo tracks 210, as shown in FIG.
2A on a one-half inch wide tape 208. The data bands are defined
between servo tracks 210. Each data band may include a number of
data tracks, for example 1024 data tracks (not shown). During
read/write operations, the readers and/or writers 206 are
positioned to specific track positions within one of the data
bands. Outer readers, sometimes called servo readers, read the
servo tracks 210. The servo signals are in turn used to keep the
readers and/or writers 206 aligned with a particular set of tracks
during the read/write operations.
[0053] FIG. 2B depicts a plurality of readers and/or writers 206
formed in a gap 218 on the module 204 in Circle 2B of FIG. 2A. As
shown, the array of readers and writers 206 includes, for example,
16 writers 214, 16 readers 216 and two servo readers 212, though
the number of elements may vary. Illustrative embodiments include
8, 16, 32, 40, and 64 active readers and/or writers 206 per array,
and alternatively interleaved designs having odd numbers of reader
or writers such as 17, 25, 33, etc. An illustrative embodiment
includes 32 readers per array and/or 32 writers per array, where
the actual number of transducer elements could be greater, e.g.,
33, 34, etc. This allows the tape to travel more slowly, thereby
reducing speed-induced tracking and mechanical difficulties and/or
execute fewer "wraps" to fill or read the tape. While the readers
and writers may be arranged in a piggyback configuration as shown
in FIG. 2B, the readers 216 and writers 214 may also be arranged in
an interleaved configuration. Alternatively, each array of readers
and/or writers 206 may be readers or writers only, and the arrays
may contain one or more servo readers 212. As noted by considering
FIGS. 2 and 2A-B together, each module 204 may include a
complementary set of readers and/or writers 206 for such things as
bi-directional reading and writing, read-while-write capability,
backward compatibility, etc.
[0054] FIG. 2C shows a partial tape bearing surface view of
complementary modules of a magnetic tape head 200 according to one
embodiment. In this embodiment, each module has a plurality of
read/write (R/W) pairs in a piggyback configuration formed on a
common substrate 204A and an optional electrically insulative layer
236. The writers, exemplified by the write transducer 214 and the
readers, exemplified by the read transducer 216, are aligned
parallel to an intended direction of travel of a tape medium
thereacross to form an R/W pair, exemplified by the R/W pair 222.
Note that the intended direction of tape travel is sometimes
referred to herein as the direction of tape travel, and such terms
may be used interchangeably. Such direction of tape travel may be
inferred from the design of the system, e.g., by examining the
guides; observing the actual direction of tape travel relative to
the reference point; etc. Moreover, in a system operable for
bi-direction reading and/or writing, the direction of tape travel
in both directions is typically parallel and thus both directions
may be considered equivalent to each other.
[0055] Several R/W pairs 222 may be present, such as 8, 16, 32
pairs, etc. The R/W pairs 222 as shown are linearly aligned in a
direction generally perpendicular to a direction of tape travel
thereacross. However, the pairs may also be aligned diagonally,
etc. Servo readers 212 are positioned on the outside of the array
of R/W pairs, the function of which is well known.
[0056] Generally, the magnetic tape medium moves in either a
forward or reverse direction as indicated by arrow 220. The
magnetic tape medium and head assembly 200 operate in a transducing
relationship in the manner well-known in the art. The piggybacked
MR head assembly 200 includes two thin-film modules 224 and 226 of
generally identical construction.
[0057] Modules 224 and 226 are joined together with a space present
between closures 204B thereof (partially shown) to form a single
physical unit to provide read-while-write capability by activating
the writer of the leading module and reader of the trailing module
aligned with the writer of the leading module parallel to the
direction of tape travel relative thereto. When a module 224, 226
of a piggyback head 200 is constructed, layers are formed in the
gap 218 created above an electrically conductive substrate 204A
(partially shown), e.g., of AlTiC, in generally the following order
for the R/W pairs 222: an insulating layer 236, a first shield 232
typically of an iron alloy such as NiFe (--), cobalt zirconium
tantalum (CZT) or Al-Fe-Si (Sendust), a sensor 234 for sensing a
data track on a magnetic medium, a second shield 238 typically of a
nickel-iron alloy (e.g., .about.80/20 at % NiFe, also known as
permalloy), first and second writer pole tips 228, 230, and a coil
(not shown). The sensor may be of any known type, including those
based on MR, GMR, AMR, tunneling magnetoresistance (TMR), etc.
[0058] The first and second writer poles 228, 230 may be fabricated
from high magnetic moment materials such as .about.45/55 NiFe. Note
that these materials are provided by way of example only, and other
materials may be used. Additional layers such as insulation between
the shields and/or pole tips and an insulation layer surrounding
the sensor may be present. Illustrative materials for the
insulation include alumina and other oxides, insulative polymers,
etc.
[0059] The configuration of the tape head 126 according to one
embodiment includes multiple modules, preferably three or more. In
a write-read-write (W-R-W) head, outer modules for writing flank
one or more inner modules for reading. Referring to FIG. 3,
depicting a W-R-W configuration, the outer modules 252, 256 each
include one or more arrays of writers 260. The inner module 254 of
FIG. 3 includes one or more arrays of readers 258 in a similar
configuration. Variations of a multi-module head include a R-W-R
head (FIG. 4), a R-R-W head, a W-W-R head, etc. In yet other
variations, one or more of the modules may have read/write pairs of
transducers. Moreover, more than three modules may be present. In
further approaches, two outer modules may flank two or more inner
modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. For
simplicity, a W-R-W head is used primarily herein to exemplify
embodiments of the present invention. One skilled in the art
apprised with the teachings herein will appreciate how permutations
of the present invention would apply to configurations other than a
W-R-W configuration.
[0060] FIG. 5 illustrates a magnetic head 126 according to one
embodiment of the present invention that includes first, second and
third modules 302, 304, 306 each having a tape bearing surface 308,
310, 312 respectively, which may be flat, contoured, etc. Note that
while the term "tape bearing surface" appears to imply that the
surface facing the tape 315 is in physical contact with the tape
bearing surface, this is not necessarily the case. Rather, only a
portion of the tape may be in contact with the tape bearing
surface, constantly or intermittently, with other portions of the
tape riding (or "flying") above the tape bearing surface on a layer
of air, sometimes referred to as an "air bearing". The first module
302 will be referred to as the "leading" module as it is the first
module encountered by the tape in a three module design for tape
moving in the indicated direction. The third module 306 will be
referred to as the "trailing" module. The trailing module follows
the middle module and is the last module seen by the tape in a
three module design. The leading and trailing modules 302, 306 are
referred to collectively as outer modules. Also note that the outer
modules 302, 306 will alternate as leading modules, depending on
the direction of travel of the tape 315.
[0061] In one embodiment, the tape bearing surfaces 308, 310, 312
of the first, second and third modules 302, 304, 306 lie on about
parallel planes (which is meant to include parallel and nearly
parallel planes, e.g., between parallel and tangential as in FIG.
6), and the tape bearing surface 310 of the second module 304 is
above the tape bearing surfaces 308, 312 of the first and third
modules 302, 306. As described below, this has the effect of
creating the desired wrap angle .alpha..sub.2 of the tape relative
to the tape bearing surface 310 of the second module 304.
[0062] Where the tape bearing surfaces 308, 310, 312 lie along
parallel or nearly parallel yet offset planes, intuitively, the
tape should peel off of the tape bearing surface 308 of the leading
module 302. However, the vacuum created by the skiving edge 318 of
the leading module 302 has been found by experimentation to be
sufficient to keep the tape adhered to the tape bearing surface 308
of the leading module 302. The trailing edge 320 of the leading
module 302 (the end from which the tape leaves the leading module
302) is the approximate reference point which defines the wrap
angle .alpha..sub.2 over the tape bearing surface 310 of the second
module 304. The tape stays in close proximity to the tape bearing
surface until close to the trailing edge 320 of the leading module
302. Accordingly, read and/or write elements 322 may be located
near the trailing edges of the outer modules 302, 306. These
embodiments are particularly adapted for write-read-write
applications.
[0063] A benefit of this and other embodiments described herein is
that, because the outer modules 302, 306 are fixed at a determined
offset from the second module 304, the inner wrap angle
.alpha..sub.2 is fixed when the modules 302, 304, 306 are coupled
together or are otherwise fixed into a head. The inner wrap angle
.alpha..sub.2 is approximately tan.sup.-1(.delta./W) where .delta.
is the height difference between the planes of the tape bearing
surfaces 308, 310 and W is the width between the opposing ends of
the tape bearing surfaces 308, 310. An illustrative inner wrap
angle .alpha..sub.2 is in a range of about 0.3.degree. to about
1.1.degree., though can be any angle required by the design.
[0064] Beneficially, the inner wrap angle .alpha..sub.2 on the side
of the module 304 receiving the tape (leading edge) will be larger
than the inner wrap angle .alpha..sub.3 on the trailing edge, as
the tape 315 rides above the trailing module 306. This difference
is generally beneficial as a smaller .alpha..sub.3 tends to oppose
what has heretofore been a steeper exiting effective wrap
angle.
[0065] Note that the tape bearing surfaces 308, 312 of the outer
modules 302, 306 are positioned to achieve a negative wrap angle at
the trailing edge 320 of the leading module 302. This is generally
beneficial in helping to reduce friction due to contact with the
trailing edge 320, provided that proper consideration is given to
the location of the crowbar region that forms in the tape where it
peels off the head. This negative wrap angle also reduces flutter
and scrubbing damage to the elements on the leading module 302.
Further, at the trailing module 306, the tape 315 flies over the
tape bearing surface 312 so there is virtually no wear on the
elements when tape is moving in this direction. Particularly, the
tape 315 entrains air and so will not significantly ride on the
tape bearing surface 312 of the third module 306 (some contact may
occur). This is permissible, because the leading module 302 is
writing while the trailing module 306 is idle.
[0066] Writing and reading functions are performed by different
modules at any given time. In one embodiment, the second module 304
includes a plurality of data and optional servo readers 331 and no
writers. The first and third modules 302, 306 include a plurality
of writers 322 and no data readers, with the exception that the
outer modules 302, 306 may include optional servo readers. The
servo readers may be used to position the head during reading
and/or writing operations. The servo reader(s) on each module are
typically located towards the end of the array of readers or
writers.
[0067] By having only readers or side by side writers and servo
readers in the gap between the substrate and closure, the gap
length can be substantially reduced. Typical heads have piggybacked
readers and writers, where the writer is formed above each reader.
A typical gap is 20-35 microns. However, irregularities on the tape
may tend to droop into the gap and create gap erosion. Thus, the
smaller the gap is the better. The smaller gap enabled herein
exhibits fewer wear related problems.
[0068] In some embodiments, the second module 304 has a closure,
while the first and third modules 302, 306 do not have a closure.
Where there is no closure, preferably a hard coating is added to
the module. One preferred coating is diamond-like carbon (DLC).
[0069] In the embodiment shown in FIG. 5, the first, second, and
third modules 302, 304, 306 each have a closure 332, 334, 336,
which extends the tape bearing surface of the associated module,
thereby effectively positioning the read/write elements away from
the edge of the tape bearing surface. The closure 332 on the second
module 304 can be a ceramic closure of a type typically found on
tape heads. The closures 334, 336 of the first and third modules
302, 306, however, may be shorter than the closure 332 of the
second module 304 as measured parallel to a direction of tape
travel over the respective module. This enables positioning the
modules closer together. One way to produce shorter closures 334,
336 is to lap the standard ceramic closures of the second module
304 an additional amount. Another way is to plate or deposit thin
film closures above the elements during thin film processing. For
example, a thin film closure of a hard material such as Sendust or
nickel-iron alloy (e.g., 45/55) can be formed on the module.
[0070] With reduced-thickness ceramic or thin film closures 334,
336 or no closures on the outer modules 302, 306, the write-to-read
gap spacing can be reduced to less than about 1 mm, e.g., about
0.75 mm, or 50% less than commonly-used LTO tape head spacing. The
open space between the modules 302, 304, 306 can still be set to
approximately 0.5 to 0.6 mm, which in some embodiments is ideal for
stabilizing tape motion over the second module 304.
[0071] Depending on tape tension and stiffness, it may be desirable
to angle the tape bearing surfaces of the outer modules relative to
the tape bearing surface of the second module. FIG. 6 illustrates
an embodiment where the modules 302, 304, 306 are in a tangent or
nearly tangent (angled) configuration. Particularly, the tape
bearing surfaces of the outer modules 302, 306 are about parallel
to the tape at the desired wrap angle .alpha..sub.2 of the second
module 304. In other words, the planes of the tape bearing surfaces
308, 312 of the outer modules 302, 306 are oriented at about the
desired wrap angle .alpha..sub.2 of the tape 315 relative to the
second module 304. The tape will also pop off of the trailing
module 306 in this embodiment, thereby reducing wear on the
elements in the trailing module 306. These embodiments are
particularly useful for write-read-write applications. Additional
aspects of these embodiments are similar to those given above.
[0072] Typically, the tape wrap angles may be set about midway
between the embodiments shown in FIGS. 5 and 6.
[0073] FIG. 7 illustrates an embodiment where the modules 302, 304,
306 are in an overwrap configuration. Particularly, the tape
bearing surfaces 308, 312 of the outer modules 302, 306 are angled
slightly more than the tape 315 when set at the desired wrap angle
.alpha..sub.2 relative to the second module 304. In this
embodiment, the tape does not pop off of the trailing module,
allowing it to be used for writing or reading. Accordingly, the
leading and middle modules can both perform reading and/or writing
functions while the trailing module can read any just-written data.
Thus, these embodiments are preferred for write-read-write,
read-write-read, and write-write-read applications. In the latter
embodiments, closures should be wider than the tape canopies for
ensuring read capability. The wider closures may require a wider
gap-to-gap separation. Therefore a preferred embodiment has a
write-read-write configuration, which may use shortened closures
that thus allow closer gap-to-gap separation.
[0074] Additional aspects of the embodiments shown in FIGS. 6 and 7
are similar to those given above.
[0075] A 32 channel version of a multi-module head 126 may use
cables 350 having leads on the same or smaller pitch as current 16
channel piggyback LTO modules, or alternatively the connections on
the module may be organ-keyboarded for a 50% reduction in cable
span. Over-under, writing pair unshielded cables may be used for
the writers, which may have integrated servo readers.
[0076] The outer wrap angles .alpha..sub.1 may be set in the drive,
such as by guides of any type known in the art, such as adjustable
rollers, slides, etc. or alternatively by outriggers, which are
integral to the head. For example, rollers having an offset axis
may be used to set the wrap angles. The offset axis creates an
orbital arc of rotation, allowing precise alignment of the wrap
angle .alpha..sub.1.
[0077] To assemble any of the embodiments described above,
conventional u-beam assembly can be used. Accordingly, the mass of
the resultant head may be maintained or even reduced relative to
heads of previous generations. In other approaches, the modules may
be constructed as a unitary body. Those skilled in the art, armed
with the present teachings, will appreciate that other known
methods of manufacturing such heads may be adapted for use in
constructing such heads. Moreover, unless otherwise specified,
processes and materials of types known in the art may be adapted
for use in various embodiments in conformance with the teachings
herein, as would become apparent to one skilled in the art upon
reading the present disclosure.
[0078] In magnetic head structures, it may be desirable to
incorporate sensor protection for a reader and/or writer
transducers to provide high wear resistance and adhesion. Moreover,
durable cobalt-iron-based (CoFe-based) layers that are part of the
pinned and/or free layers in the magnetic tunnel junctions (MTJ)
may improve performance of the tape head. CoFe-based layers without
protection may not be durable and may corrode when exposed to
running magnetic media. Corrosion may adversely affect head-medium
spacing and head stability, and may degrade head writing and
reading performance. In preferred embodiments, protection may be
provided by coating the CoFe-based layers of the reader and/or
writer transducers with a durable material.
[0079] A preferred coating technology for tape heads with alloys of
nickel and iron may be polycrystalline aluminum oxide, according to
various embodiments. CoFe-based layers of the TMR tape heads may
benefit from additional processing for durable coating adhesion. In
preferred embodiments, an improved CoFe-Aluminum (Al) oxide
interface may provide a durable at least partial polycrystalline
coating on the CoFe layer.
[0080] FIG. 8A depicts a magnetic head 800 in accordance with
various illustrative embodiments. As an option, the present
magnetic head 800 may be implemented in conjunction with features
from any other embodiment listed herein, such as those described
with reference to the other FIGS. Of course, however, such magnetic
head 800 and others presented herein may be used in various
applications and/or in permutations, which may or may not be
specifically described in the illustrative embodiments listed
herein. Further, the magnetic head 800 presented herein may be used
in any desired environment.
[0081] As shown in FIG. 8A according to one approach, the magnetic
head 800 may include a module 802. In one embodiment, the magnetic
head 800 may include a second and/or third module having a
configuration similar or identical to the module 802. For example,
the magnetic head 800 may be similar to any of the magnetic heads
described herein.
[0082] In another embodiment, the magnetic head 800 may be
configured to operate with tape media. In yet another embodiment,
the magnetic head 800 may include a slider that may be used, e.g.
with a magnetic disk.
[0083] Additionally, the magnetic head 800 may include one or more
read transducers 810 and one or more write transducers 812, as well
as conventional layers such as insulating layers, leads, coils,
etc. as would be apparent to one skilled in the art upon reading
the present description. In one approach, the one or more read
transducers 810 and the one or more write transducers 812 may be
positioned towards the media facing side 808 of the module 802. In
another approach, the one or more read transducers 810 and the one
or more write transducers 812 may be sandwiched in a gap portion
between the closure 804 and the substrate 806. In yet another
approach, the one or more read transducers 810 and the one or more
write transducers 812 may be present in an array of transducers
extending along the media facing side 808 of the module 802.
[0084] The one or more read transducers 810 and the one or more
write transducers 812 may be selected from the group consisting of
piggyback read-write transducers, merged read-write transducers,
and interleaved read and write transducers, according to various
embodiments. For example, in one approach the one or more read
transducers 810 and the one or more write transducers 812 may be
piggyback read-write transducers, such as those depicted in FIG.
2C.
[0085] In another approach, as depicted in FIG. 8A, the one or more
read transducers 810 and the one or more write transducers 812 may
be merged read-write transducers, where an upper sensor shield acts
as a pole of the writer as well as a sensor shield.
[0086] In yet another approach, as depicted in FIG. 8A, the one or
more read transducers 810 and the one or more write transducers 812
may be interleaved read and write transducers, where the read and
write transducers alternate along the array.
[0087] According to another embodiment, the one or more write
transducers 812 may be flanked by servo read transducers, e.g. as
in FIG. 2B.
[0088] With continued reference to FIG. 8A, the one or more write
transducers 812 may include write poles 814 having media facing
sides that may be recessed a depth d.sub.1 from a plane 824
extending along the media facing side 808 of the module 802,
according to one embodiment.
[0089] As shown in FIG. 8A, according to yet another embodiment,
one or more write transducers 812 may include write poles 814 that
maybe be comprised of CoFe-based layers. In other embodiments, the
pinned layer and/or free layer in the TMR and GMR of at least one
sensor 822 of one or more read transducers 810 may be comprised of
CoFe-based layers. In some approaches the AFM stabilized magnetic
shield 816 may be comprised of CoFe-based layers.
[0090] In continued reference to FIG. 8A, according to one
embodiment, a magnetic transducer 810 and/or 812 may have a CoFe
layer and an at least partially polycrystalline alumina-containing
coating 820 on a media facing side of the CoFe layer, in which a
graded layer 824 comprising Co, Fe, Al and oxygen (O) may be
positioned between the alumina-containing coating 820 and the CoFe
layer. In other embodiments, a magnetic transducer 810 and/or 812
may have a CoFe layer and an at least partially polycrystalline
alumina-containing coating 820 on a media facing side of the CoFe
layer, such that CoFe-oxide crystallites may be present at the
interface region 825 of the CoFe layer and the alumina-containing
coating 820 and the CoFe layer.
[0091] In various embodiments, an interface region 825 of the CoFe
layers and/or graded layer 824 above the CoFe layers may be present
at the reader transducer(s) 810 and/or the writer transducer(s)
812. In some approaches, a graded layer 824 may be present above
each of the CoFe layers in the module 802. In other approaches, an
interface region 825 is present in one or more of the CoFe layers.
As shown in the exemplary embodiment of FIG. 8A, a graded layer 824
is present above the shields 816 while interface regions 825 are
present in the write poles 814. In yet another approach, an
interface region 825 may be present along the surface of the CoFe
layer and a graded layer 824 is present above the interface region
825 as shown in FIG. 8B.
[0092] In some approaches, the ratio of Co to Al in the graded
layer 824 may decrease from the CoFe layer toward the
alumina-containing coating 820. In other embodiments, the
alumina-containing coating 820 may be comprised primarily of
alumina, where the alumina-containing coating also includes cobalt
oxide and iron oxide. Particularly, the alumina based coating 820
has more alumina than any other component, as well as some cobalt
oxide and iron oxide. In yet other approaches, the graded layer 824
comprising Co, Fe, Al and O may form an interface between the CoFe
layer and the alumina-containing coating. In other embodiments, the
graded layer 824 comprising Co, Fe, Al, and oxygen may be partially
crystalline.
[0093] In a preferred embodiment, the alumina-containing coating
820 may be formed on an entire media facing side 808 of the
magnetic transducer 810, 812, e.g., the media facing side of reader
and/or writer portion of the head, but not necessarily the media
facing side of the entire head 800. Moreover, in some approaches
the write transducer 812 may be comprised of at least a Co, Fe, and
Ni alloy portion. In other embodiments, the read transducer shield
816 may be comprised of at least a Co, Fe, and Ni alloy
portion.
[0094] In some approaches, the thickness of the graded layer 824
comprising Co, Fe, Al, and O may be less than 50 nanometers (nm),
but greater than zero nm. Preferably, the graded layer 824 is least
3 nm thick.
[0095] Now referring to FIG. 9, a flowchart of a method 900 is
shown according to one embodiment. The method 900 may be used to
create any of the various embodiments depicted in FIGS. 1-8, among
others, in various embodiments. Of course, more or less operations
than those specifically described in FIG. 9 may be included in
method 900, as would be understood by one of skill in the art upon
reading the present descriptions.
[0096] Each of the steps of the method 900 may be performed using
known techniques according to the teachings herein.
[0097] Referring to step 902 of FIG. 9, an optional cleaning
operation may be performed prior to a reducing operation. Known
cleaning techniques may be used. Preferred embodiments implement a
cleaning operation that involves ion milling, e.g. sputter
cleaning, bombarding with ionized argon, etc. the CoFe-based layer
at a low incidence angle of between about 5 and about 20 degrees
from normal to the surface of the CoFe layer. The sputtering energy
during the milling may be in a range of about 250 to about 500 eV.
Moreover, the duration of cleaning may facilitate fragmentation of
the carbonaceous contaminants from the surface of the CoFe layer.
In general, the cleaning step may take 2 to about 15 minutes.
[0098] While the cleaning step 902 removes carbonaceous
contaminants, it is also desirable to remove amorphous Co oxides
and/or Fe oxides from the CoFe surface upon which the alumina layer
will be formed. FIG. 10A is a magnified view of amorphous Co oxide
and Fe oxide at a CoFe surface of a comparative example. The
composition of the amorphous Co oxide (CoOx) and Fe oxide (FeOx) is
shown in the direction of the arrow of FIG. 10B, which is a
Z-contrast image of the structure in FIG. 10A with the spectral
scan direction being indicated by the arrow. FIG. 10C is an
electron energy loss spectroscopy (EELS) scan across the layer
interface shown in FIGS. 10A and 10B. The EELS scan shows the
presence of the amorphous CoOx and FeOx before the reducing
operation 904, described below.
[0099] Referring to step 904 of FIG. 9, following the cleaning
operation if it was performed, a reducing operation is performed.
Known reducing procedures may be used. Preferred embodiments
involving ion milling, e.g. sputter cleaning, bombarding with
ionized argon, etc. at a high incidence angle of between about 50
and about 70 degrees from normal to the surface of the CoFe-based
layer for at least one of removing any remaining carbonaceous
contaminants and reducing the native oxides on the surface of the
CoFe layer. Moreover, the duration of the reducing operation is
preferably sufficient to remove substantially all of an amorphous
native Co and Fe oxides sublayer from the CoFe layer, e.g.,
reducing an amorphous CoFeO.sub.x layer where x in this and other
layers represents a potential deviation from an approximately
stoichiometric ratio. As used herein, "substantially all" of the
amorphous native oxide sublayer is at least 95% thereof. In
general, the reducing operation may take 5 to about 20 minutes at a
sputtering energy during the milling in the range of about 250 to
about 500 eV.
[0100] Because it is expected that the importance of removing all
of the amorphous native oxides would not be readily apparent to one
skilled in the art, a comparative example showing the importance of
removing all of the amorphous native oxides in step 904 is made
with reference to FIGS. 11A-11C, and an embodiment shown in FIGS.
12A-12C. FIG. 11A is a magnified view of a CoFeAlO.sub.x transition
layer in which the amorphous native oxides, CoOx and FeOx, have not
been completely removed (yellow arrow). The direction of the arrow
of FIG. 11B, which is a Z-contrast image of the structure in FIG.
11A with the spectral scan direction being indicated by the arrow.
FIG. 11C is an EELS scan across the layer interface shown in FIGS.
11A and 11B. The EELS scan shows the presence of a CoFeAlOx layer,
but the interface no longer provides adequate bonding of the
alumina coating to the CoFe layer.
[0101] Referring to step 906 of FIG. 9, following the reducing
operation and prior to forming a layer of at least partially
crystalline alumina, an oxidation operation is performed to
reoxidize reduced metal oxides. Known oxidation techniques may be
used, such as exposure to an oxygen-containing atmosphere,
application of a liquid oxidant, etc. According to a preferred
approach, the oxidation operation involves applying an oxygen
plasma for oxidizing the surface of the CoFe layer, e.g., to
reoxidize reduced metal oxides. The sputtering energy during the
ion milling may be in a range of about 250 to about 500 eV. Where
the layer is CoFe, for example, reoxidation is exothermic and
promotes CoFe-oxide recrystallization on the underlying CoFe
grains. Newly formed oxide crystallites act as template for
subsequent alumina coating crystallization. The cleaning and
reducing followed by the oxidizing operations may promote formation
of a graded layer between the CoFe layer and the
subsequently-formed crystalline alumina layer thereabove. In some
embodiments, the oxidation operation may overlap with the reducing
operation, e.g., portions of the operations may be performed
concurrently and/or the operations may transition from one to the
other in a continuous manner.
[0102] Referring to Step 908 of FIG. 9, forming the alumina coating
involves depositing alumina, e.g., via sputtering, for forming a
layer of at least partially crystalline alumina on the oxidized
surface of the CoFe layer. The at least partially crystalline
alumina on the oxidized surface of the CoFe layer can be formed at
a temperature of between about 20 and about 50 degrees centigrade,
which is advantageous where the head is sensitive to higher
temperatures. Alumina deposition may be performed in the same
chamber as ion milling, without breaking the vacuum. Highly
energetic aluminum ions from the reactive sputtering of alumina in
the oxygen atmosphere may initiate thermite-like reactions with the
CoFeOx crystallites and may promote coating crystallization and
adhesion with the underlying CoFe layer. Without wishing to be
bound by any theory, the inventors believe the thermite-like
reaction between the CoFeOx crystallites and the alumina may
trigger Co and Fe diffusion upwards toward the alumina coating
thereby resulting in formation of a graded layer of Co, Fe, Al, and
O. Moreover, the inventors believe the final layer of the at least
partially crystalline alumina on the oxidized surface of the CoFe
layer may include one or more of the cubic allotropes of alumina.
The coating may transition to amorphous state once the Co and Fe
concentrations are reduced to less than 1% and at a level
undetectable by EELS
[0103] FIG. 12A is a magnified view of a properly formed, graded,
CoFeAlO.sub.x graded layer, with substantially no amorphous CoFeO
at the CoFe surface. The composition of the CoFeAlO.sub.x graded
layer thus transitions from a higher CoFe content at the left side
to a higher alumina content on the right side in the direction of
the arrow of FIG. 12B, which is a Z-contrast image of the structure
in FIG. 12A with the spectral scan direction being indicated by the
arrow. FIG. 12C is an EELS scan across the layer surface shown in
FIGS. 12A and 12B. The EELS scan shows the presence of the graded
layer.
[0104] According to the tested embodiment, the alumina coating on
the CoFe layer with a CoFeAlOx graded layer may be at least
partially polycrystalline. FIG. 13A is a Transmission Electron
Microscopy (TEM) image of the alumina coating on the CoFe layer and
the resulting crystallization. It was also discovered that the
depth of crystallization of the alumina coating could be as much as
50 nm as shown in FIG. 13A. The alumina layer formed on the
CoFeAlOx graded layer, sampled from FIG. 13A, exhibits a high
degree of crystallinity as shown in the diffractogramm shown in
FIG. 13B, where the bright spots indicate crystallinity.
[0105] Furthermore, the tape-based data storage system may include
a drive mechanism for passing a magnetic medium over the
transducer, and a controller electrically coupled to the transducer
of the magnetic head. According to various approaches, the
controller may be electrically coupled to the magnetic head via a
wire, a cable, wirelessly, etc.
[0106] It will be clear that the various features of the foregoing
systems and/or methodologies may be combined in any way, creating a
plurality of combinations from the descriptions presented
above.
[0107] It will be further appreciated that embodiments of the
present invention may be provided in the form of a service deployed
on behalf of a customer.
[0108] The inventive concepts disclosed herein have been presented
by way of example to illustrate the myriad features thereof in a
plurality of illustrative scenarios, embodiments, and/or
implementations. It should be appreciated that the concepts
generally disclosed are to be considered as modular, and may be
implemented in any combination, permutation, or synthesis thereof.
In addition, any modification, alteration, or equivalent of the
presently disclosed features, functions, and concepts that would be
appreciated by a person having ordinary skill in the art upon
reading the instant descriptions should also be considered within
the scope of this disclosure.
[0109] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only, and not limitation. Thus, the breadth and scope of an
embodiment of the present invention 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.
* * * * *