U.S. patent application number 13/961116 was filed with the patent office on 2013-12-05 for magnetic structure free layer stabilization.
This patent application is currently assigned to Seagate Technology LLC. The applicant listed for this patent is Seagate Technology LLC. Invention is credited to Eric Walter Singleton, Antonia Tsoukatos.
Application Number | 20130321954 13/961116 |
Document ID | / |
Family ID | 46234089 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130321954 |
Kind Code |
A1 |
Tsoukatos; Antonia ; et
al. |
December 5, 2013 |
MAGNETIC STRUCTURE FREE LAYER STABILIZATION
Abstract
A magnetic layered structure is presently disclosed comprising a
pinned layer, a first anti-ferromagnetic layer that defines a
magnetic orientation of the pinned layer, a free layer, a second
anti-ferromagnetic layer that biases the free layer to a magnetic
orientation approximately perpendicular to the magnetic orientation
of the pinned layer, and a tuning layer positioned between and in
contact with the second anti-ferromagnetic layer and the free layer
that tunes free layer bias to a desired level.
Inventors: |
Tsoukatos; Antonia; (Maple
Grove, MN) ; Singleton; Eric Walter; (Maple Plain,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seagate Technology LLC |
Cupertino |
CA |
US |
|
|
Assignee: |
Seagate Technology LLC
Cupertino
CA
|
Family ID: |
46234089 |
Appl. No.: |
13/961116 |
Filed: |
August 7, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12972182 |
Dec 17, 2010 |
8531802 |
|
|
13961116 |
|
|
|
|
Current U.S.
Class: |
360/125.01 ;
428/810 |
Current CPC
Class: |
G11B 5/127 20130101;
G11B 5/147 20130101; G11B 5/3932 20130101; Y10T 428/11
20150115 |
Class at
Publication: |
360/125.01 ;
428/810 |
International
Class: |
G11B 5/147 20060101
G11B005/147; G11B 5/127 20060101 G11B005/127 |
Claims
1. A magnetic layered structure comprising: a pinned layer; a first
anti-ferromagnetic layer that defines a magnetic orientation of the
pinned layer; a free layer; a second anti-ferromagnetic layer that
biases the free layer to a magnetic orientation approximately
perpendicular to the magnetic orientation of the pinned layer; and
a tuning layer positioned between and in contact with the second
anti-ferromagnetic layer and the free layer, wherein the tuning
layer tunes free layer bias to greater than 250 Oresteds (Oe).
2. The magnetic layered structure of claim 1, further comprising:
one or more side shields positioned adjacent the free layer along a
major plane of the free layer.
3. The magnetic layered structure of claim 2, wherein the side
shields include a soft magnetic material.
4. The magnetic layered structure of claim 2, wherein the side
shields include a non-magnetic material.
5. The magnetic layered structure of claim 1, further comprising:
two electrodes, each positioned on opposite sides of the layered
structure, configured to conduct current through the layered
structure along an axis approximately perpendicular to a major
plane of the free layer.
6. The magnetic layered structure of claim 1, further comprising: a
spacer layer that magnetically separates the pinned layer from the
free layer.
7. The magnetic layered structure of claim 1, further comprising: a
capping layer that protects the second anti-ferromagnetic layer
from post deposition damage.
8. The magnetic layered structure of claim 1, wherein the pinned
layer, first anti-ferromagnetic layer, free layer, and second
anti-ferromagnetic layer comprise a read element sensor.
9. The magnetic layered structure of claim 1, wherein approximately
perpendicular is perpendicular +/-15 degrees.
10. The magnetic layered structure of claim 1, wherein the first
and second anti-ferromagnetic layers comprise IrMn or PtMn and have
a thickness greater than or equal to 30 .ANG. and less than or
equal to 250 .ANG..
11. The magnetic layered structure of claim 1, wherein the tuning
layer decouples the free layer and the second anti-ferromagnetic
layer while reducing dispersion of a free layer magnetic
moment.
12. The magnetic layered structure of claim 1, wherein the free
layer comprises a first free layer and a second free layer.
13. A method of biasing a magnetic layered structure, comprising:
defining a magnetic orientation of a pinned layer using a first
anti-ferromagnetic layer; biasing a magnetic orientation of a free
layer using a second anti-ferromagnetic layer, wherein the defined
magnetic orientation of the pinned layer is approximately
perpendicular to the biased magnetic orientation of the free layer;
and tuning free layer bias to greater than 250 Oe using a tuning
layer positioned between and in contact with the second
anti-ferromagnetic layer and the free layer.
14. The method of claim 13, further comprising: shielding the free
layer from external electromagnetic and/or thermal interference
using one or more side shields positioned adjacent the free layer
along a major plane of the free layer.
15. The method of claim 13, further comprising: conducting current
along an axis approximately perpendicular to a major plane of the
free layer between two electrodes positioned on opposite sides of
the first anti-ferromagnetic layer, pinned layer, free layer, and
second anti-ferromagnetic layer.
16. The method of claim 13, further comprising: decoupling the free
layer and the second anti-ferromagnetic layer while reducing
dispersion of a free layer magnetic moment.
17. A transducer for a magnetic disc drive comprising: a reader,
including a pinned layer; a first anti-ferromagnetic layer that
defines a magnetic orientation of the pinned layer; a free layer; a
second anti-ferromagnetic layer that biases the free layer to a
magnetic orientation approximately perpendicular to the magnetic
orientation of the pinned layer; and a tuning layer positioned
between and in direct contact with the second anti-ferromagnetic
layer and the free layer, wherein the tuning layer tunes free layer
bias to greater than 250 Oe.
18. The transducer of claim 17, wherein the reader further includes
one or more side shields positioned adjacent the free layer along a
major plane of the free layer that shields the free layer from
external electromagnetic interference.
19. The transducer of claim 17, wherein the reader further includes
two electrodes, each positioned on opposite sides of the layered
structure, configured to conduct current through the layered
structure along an axis approximately perpendicular to a major
plane of the free layer.
20. The transducer of claim 17, wherein the tuning layer decouples
the free layer and the second anti-ferromagnetic layer while
reducing dispersion of a free layer magnetic moment.
Description
PRIORITY CLAIM
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/972,182, entitled "Magnetic Structure Free
Layer Stabilization," and filed Dec. 17, 2010, which is hereby
incorporated by reference in its entirety.
SUMMARY
[0002] Implementations described and claimed herein provide a
magnetic layered structure comprising a pinned layer, a first
anti-ferromagnetic layer that defines a magnetic orientation of the
pinned layer, a free layer, a second anti-ferromagnetic layer that
biases the free layer to a magnetic orientation approximately
perpendicular to the magnetic orientation of the pinned layer, and
a tuning layer positioned between and in contact with the second
anti-ferromagnetic layer and the free layer that tunes free layer
bias to a desired level.
[0003] Implementations described and claimed herein also provide a
method of biasing a magnetic layered structure comprising defining
a magnetic orientation of a pinned layer using a first
anti-ferromagnetic layer, biasing a magnetic orientation of a free
layer using a second anti-ferromagnetic layer, wherein the defined
magnetic orientation of the pinned layer is approximately
perpendicular to the biased magnetic orientation of the free layer,
and tuning free layer bias to a desired level using a tuning layer
positioned between and in contact with the second
anti-ferromagnetic layer and the free layer.
[0004] Implementations described and claimed herein also provide a
transducer for a magnetic disc drive comprising a reader including
a pinned layer, a first anti-ferromagnetic layer that defines a
magnetic orientation of the pinned layer, a free layer, a second
anti-ferromagnetic layer that biases the free layer to a magnetic
orientation approximately perpendicular to the magnetic orientation
of the pinned layer, and a tuning layer positioned between and in
direct contact with the second anti-ferromagnetic layer and the
free layer that tunes free layer bias to a desired level.
[0005] Other implementations are also described and recited
herein.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0006] FIG. 1 illustrates an example magnetic structure with free
layer stabilization.
[0007] FIG. 2 illustrates an air bearing surface of an example read
element with dual AFM layers and soft magnetic side shields.
[0008] FIG. 3 illustrates example operations for manufacturing a
magnetic structure according to the presently disclosed
technology.
[0009] FIG. 4 illustrates example operations for biasing a magnetic
layered structure according to the presently disclosed
technology.
[0010] FIG. 5 illustrates an air bearing surface of another example
read element with multiple AFM layers and soft magnetic side
shields.
DETAILED DESCRIPTIONS
[0011] Information and communication systems increasingly handle
huge amounts of data, placing heavy demands on magnetic media
storage capacity and performance. As areal recording densities
increase, smaller, more sensitive read element heads and
magnetic-based storage devices are desired that are effectively
shielded from noise in deciphering a read signal.
[0012] A read element may include an anti-ferromagnetic (AFM)
layer, a pinned layer, a spacer layer, and a free layer. The AFM
layer emits an exchange-coupling field that fixes the magnetization
orientation of the pinned layer. Magnetization orientation of the
free layer rotates according to a detected signal from a magnetic
media. The spacer layer serves to separate the magnetic orientation
of the pinned layer from the free layer. As the read element passes
over magnetic bits on a magnetic media, the magnetic orientation of
the bits causes the magnetic orientation of the free layer to
shift.
[0013] Electrical resistance of the read element is low when the
magnetization orientation of the pinned layer and the free layer
are parallel. Electrical resistance of the read element is high
when the magnetization orientation of the pinned layer and the free
layer are anti-parallel. Sense current flows into the read element
sensor through the electrodes and a change in resistance affects a
readback voltage. As a result, orientation of bits on the magnetic
media or sensing of bits stored in a memory cell can be detected by
changes in the readback voltage.
[0014] A source of noise interference on read element sensors are
edge effects. Edge effects can be the result of side reading or
geometry features created during fabrication of the read element
sensor. To counteract the edge effects, hard magnetic side shields
are placed on each side of the laminated metallic layers of the
read element. The hard magnetic side shields shield the free layer
from the edge effects and bias the free layer to either a parallel
or anti-parallel magnetization orientation. The magnetization bias
prevents relatively small interference signals from changing the
magnetization orientation of the read element while still allowing
the magnetic field from the data bits to affect magnetization
orientation of the read element. However, as read elements become
smaller and smaller, hard magnetic side shields cannot practically
be placed on each side of the laminated metallic layers of the read
element. Further, the interface of the hard magnetic side shields
with the read element may also be a source of noise.
[0015] In one implementation, a read element according to the
presently disclosed technology allows for soft magnetic side
shielding, which results in a narrower track width of the read
element than a corresponding read element with hard magnetic side
shielding. The soft magnetic side shielding may be narrower because
junction/permanent magnetic interactions are eliminated. Further,
the presently disclosed read element provides a detection
resolution increase and reduction of noise interference. These
advantages mitigate an incremental shield-to-shield spacing
increase caused by the additional top AFM layer as compared to a
conventional read element.
[0016] FIG. 1 illustrates an example magnetic structure 100 with
free layer stabilization. First and second electrical leads 158,
160 electrically connect the magnetic structure 100 to a power
source (not shown) and conduct a sense current through the magnetic
structure 100 perpendicular to the major planes of the layers of
the magnetic structure 100. In one implementation, the magnetic
structure 100 is implemented as a magnetic memory cell.
[0017] The magnetic structure 100 includes a free layer 134 and a
pinned layer 138 with a nonmagnetic electrically conductive or
nonconductive spacer layer 144 there between. Polarity of the
pinned layer 138 is pinned by a bottom AFM layer 130. The bottom
AFM layer 130 sets the polarity of the pinned layer 138 (shown
schematically by symbol 146) approximately perpendicular to the
depicted magnetic structure 100 in a direction toward the depicted
magnetic structure 100 and parallel to the major planes of the
various magnetic structure 100 (e.g., in the negative
z-direction).
[0018] A top AFM layer 132 biases the polarity of the free layer
134 (shown schematically by symbols 150) approximately parallel to
the depicted magnetic structure 100 and approximately parallel to
the major planes of the various magnetic structure 100 layers
(e.g., in the x-direction). In some implementations, it is
difficult to align the polarity bias of the free layers 134 exactly
parallel to the depicted magnetic structure 100 and major planes of
the various magnetic structure 100 layers. In one embodiment, the
polarity bias of the free layers 134 is within 15 degrees of
parallel to the depicted magnetic structure 100 and 15 degrees of
parallel to the major planes of the various magnetic structure 100
layers. A greater range may still allow the magnetic structure 100
to function sufficiently, as well.
[0019] When the magnetic polarity of the free layer 134 is rotated
into the negative z-direction, the symbols 146 and 150 become more
anti-parallel which illustrates an increase in the resistance of
the magnetic structure 100 to a sense current passing between the
first and second electrical leads 158, 160. Conversely, when the
magnetic polarity of the free layer 134 is rotated in the positive
z-direction, the symbols 146 and 150 become more parallel, which
illustrates a decrease in the resistance of the magnetic structure
100 to the sense current passing between the first and second
electrical leads 158, 160.
[0020] A tuning layer 152 is positioned between the top AFM layer
132 and the free layer 134. The thickness of the tuning layer 152
is tuned or optimized to provide a desired bias level (i.e.,
magnetic coupling) to the free layer 134. In other words, the bias
level of the free layer 134 is tuned to a desired level by
selecting a material and/or thickness of the tuning layer 152. For
example, a particularly thin tuning layer 152 will place the top
AFM layer 132 and the free layer 134 close together, thus the
polarity bias from the top AFM layer 132 on the free layer 134 will
be particularly strong (or stiff). Conversely, a particularly thick
tuning layer 152 will place the top AFM layer 132 and the free
layer 134 not as close together, thus the polarity bias from the
top AFM layer 132 on the free layer 134 will not be as strong (or
more flexible). Strength of the bias level is selected to obtain a
desired sensitivity of the magnetic structure 100 while allowing
the magnetic structure 100 to remain sufficiently stable. In other
words, the turning layer 152 decouples the free layer 134 from the
top AFM layer 132 and reduces dispersion of the free layer magnetic
moment.
[0021] As compared to an implementation without a spacer layer,
incorporation of the tuning layer 152 in the magnetic structure 100
allows a high pinning field strength of the top AFM layer 132 to be
maintained while reducing dispersion of the pinning field. Further,
the tuning layer 152 reduces coercivity of the pinning field of the
top AFM layer 132. Low coercivity is desirable to reduce effects of
external thermal and/or magnetic signals on the polarity of the top
AFM layer 132. Different materials and thicknesses of the tuning
layer 152 affect pinning field strength, dispersion of the pinning
field, and coercivity of the tuning layer 152.
[0022] FIG. 2 illustrates an air bearing surface of an example read
element 200 with dual AFM layers 230, 232 and soft magnetic side
shields 222. The read element 200 is shown as viewed from a
magnetic media looking upwards at the air bearing surface (ABS) of
the read element 200. The read element 200 is located between first
and second shields 216, 218 that also serve as first and second
electrical lead layers. The first and second shields 216, 218
conduct a sense current through the read element 200 perpendicular
to the major planes of the layers of the read element 200. The read
element 200, in this implementation, includes first and second free
layers 234, 236 laminated together. In other implementations, there
is only one free layer or more than two free layers laminated
together.
[0023] The read element 200 also includes a pinned layer lamination
including first and second pinned layers 238, 240 and an interlayer
242 between the pinned layers 238, 240. The interlayer 242 is a
nonmagnetic electrically conductive anti-parallel coupling (APC)
that interfaces the two pinned layers 238, 240 together. In some
implementations, layers 238, 240, 242 together form a synthetic
anti-ferromagnet (SAF). A nonmagnetic electrically conductive or
nonconductive spacer or barrier layer 244 is located between the
free layer lamination 234, 236 and the pinned layer lamination.
[0024] Polarity of the pinned layers 238, 240 is pinned by a bottom
AFM layer 230. The bottom AFM layer 230 sets the polarity of pinned
layer 238 (shown schematically by symbol 246) approximately
perpendicular to the depicted ABS plane in a direction toward the
depicted ABS and parallel to the major planes of the various read
element 200 layers (e.g., in the negative z-direction). Polarity of
AFM layer 232 (shown schematically by symbol 248) is oriented
anti-parallel (e.g., in the z-direction) to polarity 246 by a
strong anti-parallel coupling between the pinned layers 238, 240
provided by the interlayer 242. In another implementation, polarity
of the pinned layer 238 is oriented away from the depicted ABS and
polarity of the AFM layer 232 is oriented toward the depicted ABS.
In yet another implementation, the polarities of pinned layers 238,
240 are parallel to the depicted ABS plane.
[0025] The top AFM layer 232 biases the polarity of the laminated
free layers 234, 236 (shown schematically by symbols 250)
approximately parallel to the depicted ABS and approximately
parallel to the major planes of the various read element 200 layers
(e.g., in the x-direction). In some implementations, it is
difficult to align the polarity bias of the laminated free layers
234, 236 exactly parallel to the depicted ABS and major planes of
the various read element 200 layers. In one embodiment, the
polarity bias of the laminated free layers 234, 236 is within 15
degrees of parallel to the depicted ABS and 15 degrees of parallel
to the major planes of the various read element 200 layers. A
greater range may still allow the read element 200 to function
sufficiently, as well.
[0026] When a field signal from a magnetic media rotates the
magnetic polarity of the laminated free layers 234, 236 into the
depicted ABS (e.g., in the negative z-direction), the symbols 248
and 250 become more anti-parallel which illustrates an increase in
the resistance of the read element 200 to a sense current passing
between the first and second shields 216, 218. Conversely, when a
field signal from the magnetic media rotates the magnetic polarity
of the laminated free layers 234, 235 out of the depicted ABS
(e.g., in the z-direction), the symbols 248 and 250 become more
parallel, which illustrates a decrease in the resistance of the
read element 200 to the sense current passing between the first and
second shields 216, 218.
[0027] Tuning layer 252 is positioned between the top AFM layer 232
and the free layers 234, 236. The thickness of the tuning layer 252
is tuned or optimized to provide a desired bias level (i.e.,
magnetic coupling) to the free layers 234, 236. In other words, the
bias level of the free layers 234, 236 is tuned to a desired level
by selecting a material and/or thickness of the tuning layer 252.
For example, a particularly thin tuning layer 252 will place the
top AFM layer 232 and free layers 234, 236 close together, thus the
polarity bias from the top AFM layer 232 on the free layers 234,
236 will be particularly strong (or stiff). Conversely, a
particularly thick tuning layer 252 will place the top AFM layer
232 and free layers 234, 236 not as close together, thus the
polarity bias from the top AFM layer 232 on the free layers 234,
236 will not be as strong (or more flexible). Strength of the bias
level is selected to obtain a desired sensitivity of the read
element 200 while allowing the read element 200 to remain
sufficiently stable.
[0028] An AFM cap 254 is placed on the AFM layer 232 to protect the
AFM layer 232 from corrosion and subsequent processing steps. In
some implementations, an additional seed layer is placed between
the AFM layer 232 and second shield 218 that prepares the read
element 200 for application of the second shield 218. For example,
the seed layer is adapted to accept a plating operation that places
the second shield 218 on the read element 200.
[0029] As compared to an implementation without a spacer layer,
incorporation of the tuning layer 252 in the read element 200
allows a high pinning field strength of the top AFM layer 232 to be
maintained while reducing dispersion of the pinning field. Further,
the tuning layer 252 reduces coercivity of the pinning field of the
top AFM layer 232. Low coercivity is desirable to reduce effects of
external thermal and/or magnetic signals on the polarity of the top
AFM layer 232. Different materials and thicknesses of the tuning
layer 252 affect pinning field strength, dispersion of the pinning
field, and coercivity of the tuning layer 252. In some
implementations the tuning layer 252 is sandwiched between two
layers of an AFM layer rather than adjacent top AFM layer 232 as
shown in FIG. 2. In other implementations, there are multiple
spacer layers (soft magnetic and/or nonmagnetic) to maximize
pinning field strength while minimizing dispersion of the pinning
field. The tuning layer 252 may decrease dispersion of the pinning
field by as much as 50% without causing major degradation of the
pinning field.
[0030] Sides of the read element 200 are surrounded by a
non-magnetic, non-conductive filler material 220 (e.g., alumina).
Further, soft magnetic side shields 222 are used on the sides of
the read element 200 to reduce electromagnetic interference (e.g.,
side reading consideration and stray field noise), primarily
x-direction interference and/or z-direction interference. The soft
magnetic side shields 222 are separated from the top shield 218 by
side shield caps 256 and bottom shield 216 by the filler material
220. Use of soft magnetic side shields 222 (as opposed to hard
magnetic side shields) allows for sub-100 nm thickness of the read
element 200 and shields 216, 218 collectively, as discussed above.
In one implementation, the side shields 222 are NiFe. In other
implementations, the side shields 222 are non-magnetic. In still
other implementations, the side shields 222, top shield 218, and
bottom shield 216 are made of the same soft magnetic material. In
yet other implementations, the shields 222, top shield 218, and
bottom shield 216 are made of a non-magnetic material.
[0031] One implementation of the presently disclosed technology
utilizes the following materials and thicknesses. The bottom AFM
layer 230 may be made of IrMn and/or PtMn and have a thickness
ranging from 30-250 Angstrom (.ANG.). Each of the pinning layers
238, 240 may also be made of high coercivity materials such as
CoPt, CoPtCr, FePt, CoPtCrTa, and/or various materials derived from
CoPt, CoPtCr, FePt, and/or CoPtCrTa and have a thickness ranging
from 20-150 A. In other implementations, each of the pinning layers
238, 240 may be made of low coercivity materials such as CoFe,
CoNiFe, and/or CoFeB. The interlayer 242 may be made of chromium,
ruthenium, and/or rhodium and have a thickness ranging up to 10 A.
In some implementations, there is no interlayer 242. The spacer
layer 244 may be made of titanium oxide, alumina, magnesium oxide,
and/or a conductive material (e.g., copper or a copper alloy) and
have a thickness ranging up to 30 A.
[0032] The free layer(s) 234, 236 may be made of NiFe and/or CoFe
and have thicknesses ranging from 20-50 A. The tuning layer 252 may
be made of chromium, ruthenium, tantalum, and/or rhodium and have a
thickness ranging up to 10 A. In some implementations, there is no
tuning layer 252. The top AFM layer 232 may be made of IrMn and/or
PtMn and have a thickness ranging from 30-100 A. The AFM cap 254
may be made of chromium, ruthenium, and/or rhodium and have a
thickness ranging up to 50 A. In some implementations, there is no
AFM cap 254. The soft magnetic side shields 222 may be made of NiFe
alloys and have a thickness ranging from 50-200 A. The side shield
caps 256 may be made of chromium, ruthenium, and/or rhodium and
have a thickness ranging up to 100 A. In some implementations,
there are no side shield caps 256. Each of the first and second
shields 216, 218 may be made of NiFe alloys and have a thickness
ranging from 1-2 microns.
[0033] In various implementations, the presently disclosed
technology is applicable to high density perpendicular media,
discrete track recording (DTR), and/or bit patterned media (BPM).
Further, the presently disclosed technology is capable of thermal
reliability up to at least 200.degree.-250.degree. C.
[0034] FIG. 3 illustrates example operations 300 for manufacturing
a read element according to the presently disclosed technology. In
a deposition operation 310, a bottom shield, seed AFM layer, first
pinned layer, interlayer, second pinned layer, spacer layer, and
free layer(s) are sequentially deposited on a semiconductor wafer
(e.g., an AlTiC wafer) using conventional transducer processing
techniques. In a second deposition operation 315, a tuning layer is
deposited on the free layer(s) of the read element. In many
implementations, the second deposition operation 315 is performed
at a temperature ranging between 20.degree. C. and 400.degree.
C.
[0035] In a third deposition operation 320, a second AFM layer and
an AFM capping layer are sequentially deposited on the tuning
layer. Substrate temperature during deposition and thickness of the
second AFM layer control bias in the free layer(s). In one
implementation, the objective for the second AFM pinning of the
free layers is to establish a free layer bias in the order of
250-800 Oe in a direction perpendicular to the first AFM pinning
direction. Further, thickness of the tuning layer also affects the
pinning in the free layers. The thicknesses of the free layer(s)
and AFM layers, and substrate temperatures during deposition are
also optimized to maintain thermal stability, repeatability, and
bias on the read element.
[0036] In a read element definition operation 325, photolithography
and ion beam etch processing set the reader geometry for a desired
read track width. Further, an alumina material is deposited over
exposed sides of the aforementioned layers. The alumina material
electrically isolates the aforementioned layers from electrical
transmission in a direction coplanar to the aforementioned layers
(e.g., to adjacent soft magnetic material deposited in a fourth
deposition operation 330). As a result, the alumina material
facilitates electrical conduction between the top and bottom
shields, allowing for efficient read element operation.
[0037] In the fourth deposition operation 330, a soft magnetic
material is deposited adjacent to the alumina material. The soft
magnetic material serves to magnetically shield the free layer(s)
from external magnetic interference. In one implementation, soft
magnetic material is coplanar to at least the free layer(s), tuning
layer, and second AFM layer. The soft magnetic material may also be
coplanar with one or more of the seed AFM layer, first pinned
layer, interlayer, second pinned layer, spacer layer, and AFM
capping layer. In some implementations, an additional capping layer
is applied over the soft magnetic material. The capping layer(s)
have adequate thickness to maintain the top exchange bias integrity
through the definition process, post deposition.
[0038] In a fifth deposition operation 335, a seed layer and top
shield are deposited on the AFM capping layer. In an annealing
operation 340, the AFM layers are annealed to set the magnetic
orientation of the AFM layers. In many implementations, the
magnetic orientation of the second AFM layer is set perpendicular
to the magnetic orientation of the first AFM layer in a direction
co-planar to on or more of the aforementioned layers. In some
implementation, the annealing operation 340 is performed between
1-5 kGauss at a temperature ranging from 215-235 degrees Celsius.
In operation, electricity is conducted between the bottom shield
and the top shield. Polarity of the free layer(s) changes with
proximity to magnetic bits. As the polarity of the free layer(s)
changes, overall resistance of the aforementioned layered structure
changes. Changes in the resistance of current flowing in a
direction perpendicular to the aforementioned layers affects a
voltage differential between the bottom shield and the top shield.
As a result, changes in the voltage differential are used to detect
the presence and/or orientation of magnetic bits. Upon completion
of the aforementioned stack deposition, photolithography and etch
processes may follow without changes to customary processing of the
transducer.
[0039] FIG. 4 illustrates example operations 400 for biasing a
magnetic layered structure according to the presently disclosed
technology. A defining operation 410 defines a magnetic orientation
of a pinned layer using a first anti-ferromagnetic layer in the
magnetic layered structure. A biasing operation 415 biases a
magnetic orientation of a free layer in a direction perpendicular
to the magnetic orientation of the pinned layer defined in
operation 410 using a second anti-ferromagnetic layer in the
magnetic layered structure.
[0040] A tuning operation 420 tunes the free layer magnetic
orientation to a desired level using a tuning layer. The tuning
operation 420 balances reduction of noise interference with
detection resolution within the magnetic layered structure. At
least the material composition and thickness of the tuning layer
affects the amount of tuning in operation 420. An optional
decoupling operation 425 decouples the free layer and the second
anti-ferromagnetic layer from one another. In one implementation, a
spacer layer positioned between the free layer and the second
anti-ferromagnetic layer provides the decoupling of the operation
425. An optional shielding operation 430 shields the free layer
from external interference. In one implementation, one or more side
shields placed adjacent the free layer along a major plane of the
free layer provides the shielding of operation 430.
[0041] FIG. 5 illustrates an air bearing surface of an example read
element 500 with three AFM layers 530, 532, and 558. The read
element 500 is shown as viewed from a magnetic media looking
upwards at the air bearing surface (ABS) of the read element 500.
The read element is located between first and second shields 516
and 518. The read element 500 includes first and second free layers
534 and 536 laminated together. The read element 500 also includes
a pinned layer lamination including first and second pinned layers
538, 540, and an interlayer 542 between the pinned layers 538, 540.
A nonmagnetic electrically conductive or nonconductive spacer or
barrier layer 544 is located between the free layer lamination 534,
536, and the pinned layer lamination.
[0042] Polarity of the pinned layers 538, 540 is pinned by a bottom
AFM layer 530. The top AFM layer 552 and a middle AFM layer 558
biases the polarity of the laminated free layers 534, 536. The
polarity of the pinned layers 538, 540, free layers 534, 536, and
top and bottom AFM layers 530 and 552 may be the same or similar to
such layers illustrated and described with respect to FIG. 2.
[0043] A tuning element 552 is sandwiched between the top AFM layer
532 and the middle AFM layer 558. The thickness of the tuning layer
552 may be tuned or optimized to provide a desired bias level
(i.e., magnetic coupling) to the free layers 534, 536. Such tuning
may be performed in a same or a similar manner to that described
above with respect to FIG. 2.
[0044] Sides of the read element 500 are surrounded by a
non-magnetic, non-conductive filler material 520 (e.g., alumina).
Soft magnetic side shields 522 are used on the side of the read
element 500. The soft magnetic side shields 522 are separated from
the top shield 518 by side shield caps 556 and bottom shield 516 by
the filler material 520.
[0045] The above specification, examples, and data provide a
complete description of the structure and use of exemplary
embodiments of the invention. Since many embodiments of the
invention can be made without departing from the spirit and scope
of the invention, the invention resides in the claims hereinafter
appended. Furthermore, structural features of the different
embodiments may be combined in yet another embodiment without
departing from the recited claims.
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