U.S. patent application number 14/486827 was filed with the patent office on 2016-03-17 for sensor structure having layer with high magnetic moment.
The applicant listed for this patent is Seagate Technology LLC. Invention is credited to Kevin McNeill, Victor Boris Sapozhnikov.
Application Number | 20160078889 14/486827 |
Document ID | / |
Family ID | 55314717 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160078889 |
Kind Code |
A1 |
Sapozhnikov; Victor Boris ;
et al. |
March 17, 2016 |
SENSOR STRUCTURE HAVING LAYER WITH HIGH MAGNETIC MOMENT
Abstract
A reader sensor having a composite shield and a sensor stack.
The composite shield includes a high magnetic moment layer having a
magnetic moment greater than 1.0 T, a low magnetic moment layer,
and a spacer therebetween. The high magnetic moment layer is closer
to the stack than the low magnetic moment layer. The high magnetic
moment layer may be a single layer or have a plurality of
layers.
Inventors: |
Sapozhnikov; Victor Boris;
(Minnetonka, MN) ; McNeill; Kevin; (Derry,
IE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seagate Technology LLC |
Cupertino |
CA |
US |
|
|
Family ID: |
55314717 |
Appl. No.: |
14/486827 |
Filed: |
September 15, 2014 |
Current U.S.
Class: |
360/319 |
Current CPC
Class: |
G11B 5/398 20130101;
G11B 5/3932 20130101; G11B 5/3912 20130101 |
International
Class: |
G11B 5/39 20060101
G11B005/39 |
Claims
1. A reader sensor comprising: a sensor stack; and a composite
shield including a high magnetic moment (HMM) layer having a
magnetic moment greater than 1.0 T, a pinned low magnetic moment
(LMM) layer, and a spacer therebetween, wherein the HMM layer is
closer to the stack than the pinned LMM layer and is in contact
with and adjacent to the stack.
2. The reader sensor of claim 1, wherein the composite shield is a
top shield.
3. The reader sensor of claim 1, wherein the composite shield is a
bottom shield.
4. (canceled)
5. The reader sensor of claim 1, the composite shield further
comprising a LMM material layer.
6. The reader sensor of claim 5, wherein the LMM material layer is
adjacent to and in contact with the HMM layer.
7. The reader sensor of claim 5, wherein the HMM layer has a
thickness of at least 1 nm.
8. The reader sensor of claim 1, wherein the HMM layer comprises a
mixture of a LMM material and a HMM material.
9. The reader sensor of claim 1, wherein the HMM layer has a
magnetic moment of at least 1.2 T.
10. The reader sensor of claim 1, wherein the HMM layer has a
thickness between about 4 nm and 30 nm.
11-17. (canceled)
18. A reader sensor comprising: a top shield; a bottom shield; and
a sensor stack between the top shield and the bottom shield;
wherein one of the top shield or the bottom shield comprises: a
reference layer, a pinned layer, a spacer between and in contact
with each of the reference layer and the pinned layer, and a high
magnetic moment (HMM) layer having a magnetic moment of at least
1.2 T and magnetically coupled to the reference layer, the HMM
layer adjacent to the sensor stack.
19. (canceled)
20. (canceled)
21. The reader sensor of claim 18, wherein the pinned layer has a
magnetic moment no greater than 1.0 T.
22. The reader sensor of claim 18, wherein the HMM layer has a
thickness no greater than 50 nm.
23. The reader sensor of claim 1, wherein the HMM layer has a
thickness no greater than 50 nm.
24. A reader sensor comprising: a top shield; a bottom shield; and
a sensor stack between the top shield and the bottom shield;
wherein one of the top shield or the bottom shield comprises: a
pinned layer, a high magnetic moment (HMM) layer having a magnetic
moment greater than 1.0 T, the HMM layer comprising a HMM material
having a magnetic moment of at least 1.2 T, and a spacer between
the pinned layer and the HMM layer, with the HMM layer in contact
with and adjacent to the sensor stack.
25. The reader sensor of claim 24, wherein the HMM material is one
of FeCo, FeCoN, FeSi, or FeC.
26. The reader sensor of claim 25, the HMM layer comprising the HMM
material combined with a low magnetic moment (LMM) material having
a magnetic moment no greater than 1.0 T.
27. The reader sensor of claim 26, wherein the HMM layer is not
magnetically coupled to the sensor stack.
28. The reader sensor of claim 25, wherein the HMM layer has a
thickness no greater than 50 nm.
29. The reader sensor of claim 24, further comprising a reference
layer adjacent to the HMM layer, with the spacer between the pinned
layer and the reference layer.
Description
BACKGROUND
[0001] In a magnetic data storage and retrieval system, a magnetic
read/write head includes a reader portion having a magnetoresistive
(MR) sensor for retrieving magnetically encoded information stored
on a magnetic disc. Magnetic flux from the surface of the disc
causes rotation of the magnetization vector of a sensing layer of
the MR sensor, which in turn causes a change in electrical
resistivity of the MR sensor. The change in resistivity of the MR
sensor can be detected by passing a current through the MR sensor
and measuring a voltage across the MR sensor. External circuitry
then converts the voltage information into an appropriate format
and manipulates that information to recover the information encoded
on the disc.
SUMMARY
[0002] One particular implementation described herein is a reader
sensor having a sensor stack and a composite shield. The composite
shield includes a high magnetic moment (HMM) layer having a
magnetic moment greater than 1.0 T, a low magnetic moment (LMM)
layer, and a spacer therebetween, wherein the HMM layer is closer
to the stack than the LMM layer.
[0003] Another particular implementation is a reader sensor having
a top shield, a bottom shield, and a sensor stack between the top
shield and to the bottom shield. At least one of the top shield and
the bottom shield includes a reference layer having a high magnetic
moment greater than 1.0 T, a pinned layer having a magnetic moment
no greater than 1.0 T, and a spacer therebetween. The reference
layer is closer to the stack than the pinned layer.
[0004] Yet another particular implementation is a reader sensor
having a top shield, a bottom shield, and a sensor stack between
the top shield and the bottom shield. One of the top shield or the
bottom shield comprises a reference layer, a pinned layer, a spacer
between the reference layer and the pinned layer, and a high
magnetic moment (HMM) layer magnetically coupled to the reference
layer. The HMM layer is closer to the one of the top shield or the
bottom shield than the reference layer.
[0005] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter. These and various other features and advantages
will be apparent from a reading of the following detailed
description.
BRIEF DESCRIPTIONS OF THE DRAWING
[0006] The described technology is best understood from the
following Detailed Description describing various implementations
read in connection with the accompanying drawings.
[0007] FIG. 1 is a perspective view of an example recording device
using a reader having a sensor structure disclosed herein.
[0008] FIG. 2 is a schematic an air-bearing surface (ABS) view of
an example reader sensor structure.
[0009] FIG. 3 is a schematic an air-bearing surface (ABS) view of
an example reader sensor structure.
[0010] FIG. 4 is a schematic an air-bearing surface (ABS) view of
an example reader sensor structure.
[0011] FIG. 5 is a schematic an air-bearing surface (ABS) view of
an example reader sensor structure.
[0012] FIG. 6 is a graphical representation of the effect of the
magnetic moment of a material and its thickness on PW50.
[0013] FIG. 7 is a graphical representation of the effect of the
magnetic moment of a material, its thickness, and its inclusion
with other materials on PW50.
[0014] FIG. 8 is a flowchart illustrating an example method of
forming an example reader sensor structure.
[0015] FIG. 9 is a flowchart illustrating an example method of
forming an example reader sensor structure.
DETAILED DESCRIPTION
[0016] There is an increasing demand for high data densities and
sensitive sensors to read data from a magnetic media. Giant
Magnetoresistive (GMR) sensors that have increased sensitivity
consist of two soft magnetic layers separated by a thin conductive,
non-magnetic spacer layer such as copper. Tunnel Magnetoresistive
(TMR) sensors provide an extension to GMR in which the electrons
travel with their spins oriented perpendicularly to the layers
across a thin insulating tunnel barrier. An antiferromagnetic (AFM)
material (often called a "pinning layer") is placed adjacent to the
first soft magnetic layer to prevent it from rotating. With its
rotation inhibited, the first soft layer is termed the "pinned
layer" (PL). AFM materials exhibiting this pinning property are
termed "pinning materials". The second soft magnetic layer rotates
freely in response to an external field and is called the "free
layer" (FL).
[0017] To operate the MR sensor properly, the sensor is preferably
stabilized against the formation of edge domains because domain
wall motion results in electrical noise that makes data recovery
difficult. A common way to achieve stabilization is with a
permanent magnet abutted junction design. In this scheme, permanent
magnets with high coercive field (i.e., hard magnets) are placed at
each end of the sensor. The field from the permanent magnets
stabilizes the sensor and prevents edge domain formation, as well
as provides proper bias. In order to increase the stiffness of the
PL, a synthetic antiferromagnetic (SAF) material is used in the PL.
The use of the AFM/PL allows for consistent and predictable
orientation of the SAF structure. Furthermore, the use of the
AFM/PL also provides stable structure to enable high amplitude
linear response for a reader using the MR sensor.
[0018] The assembly of the various layers the GMR/TMR sensors, as
discussed above, is also referred to as a sensor stack. Such sensor
stack may be surrounded by a bottom shield and a top shield to
shield the sensor from any magnetic influences that are generated
from other components of the transducer head; these shields can be
referred to as bulk shields. In such an implementation, the
distance between the top shield and the bottom shield is referred
to as the shield-to-shield spacing (SSS). PW50, which is the pulse
width of a magnetic element at 50% of the pulse amplitude, is
indicative of the spatial resolution of the sensor. The pulse width
PW50 of magnetic sensors, which determine the signal-to-noise (SNR)
ratio in a recording system, depend on the SSS of the head.
Specifically, a reduction in the SSS leads to reduction in the
value of the PW50 and therefore, an increase in the value of the
SNR for the recording system. However, using SSS reduction to
achieve lower PW50 has its limits.
[0019] The PW50 performance of a shield can be improved by
increasing its magnetic moment. However, higher-moment materials
tend to have higher coercivity and magnetic non-uniformity, which
creates shield instability and a decrease in the SNR. A top shield
has two main functions: shielding for PW50 and MT metrics
improvement, and support of the side shields. However, supporting
the side shields precludes PW50 reduction by using thin layers
decoupled from the bulk shields.
[0020] An example sensor assembly disclosed herein provides PW50
improvement while having shield material coercivity and magnetic
non-uniformity significantly less than in a high-moment shield.
Specifically an example sensor assembly disclosed herein provides
alternative methods for reducing the PW50 of a sensor without
reducing the SSS of the sensor and without increasing significantly
the coercivity and magnetic non-uniformity of the shields.
Specifically, the sensor assembly includes a reader sensor or
"stack" surrounded by a bottom shield and a top shield in
down-track direction, where one of the shields has a layer,
magnetically coupled to the rest of the shield, having a high
magnetic moment (higher than 1.0 T) close to the sensor stack. By
providing a high magnetic moment material close to the sensor
stack, the stability of the sensor is maintained, due to a small
increase in coercivity and magnetic non-uniformity, if any, while
the PW50 of the sensor stack is greatly decreased. The result is
improved SNR of the recording system using such sensor
assembly.
[0021] It is noted that the technology disclosed herein may be used
in conjunction with a variety of different types of magnetic
sensors (e.g., anisotropic magnetoresistive (AMR) sensors, TMR
sensors, GMR sensors, etc.). Accordingly, the implementations
discussed may also be applicable to new sensor designs that are
based on new physical phenomena such as lateral spin valve (LSV),
spin-hall effect (SHE), spin torque oscillation (STO), etc.
[0022] In the following description, reference is made to the
accompanying drawing that forms a part hereof and in which are
shown by way of illustration at least one specific implementation.
The following description provides additional specific
implementations. It is to be understood that other implementations
are contemplated and may be made without departing from the scope
or spirit of the present disclosure. The following detailed
description, therefore, is not to be taken in a limiting sense.
While the present disclosure is not so limited, an appreciation of
various aspects of the disclosure will be gained through a
discussion of the examples provided below. In some instances, a
reference numeral may have an associated sub-label consisting of a
lower-case letter to denote one of multiple similar components.
When reference is made to a reference numeral without specification
of a sub-label, the reference is intended to refer to all such
multiple similar components.
[0023] FIG. 1 illustrates a perspective view of an example
recording device 100 using a reader disclosed herein. Recording
device 100 includes a disc 102, which rotates about a spindle
center or a disc axis of rotation 104 during operation. The disc
102 includes an inner diameter 106 and an outer diameter 108
between which are a number of concentric data tracks 110,
illustrated by circular dashed lines. The data tracks 110 are
substantially circular and are made up of regularly spaced
patterned bits 112, indicated as dots or ovals on the disc 102. It
should be understood, however, that the described technology may be
employed with other types of storage media, including continuous
magnetic media, discrete track (DT) media, etc.
[0024] Information may be written to and read from the bits 112 on
the disc 102 in different data tracks 110. A transducer head 124 is
mounted on an actuator assembly 120 at an end distal to an actuator
axis of rotation 122 and the transducer head 124 flies in close
proximity above the surface of the disc 102 during disc operation.
The actuator assembly 120 rotates during a seek operation about the
actuator axis of rotation 122 positioned adjacent to the disc 102.
The seek operation positions the transducer head 124 over a target
data track of the data tracks 110.
[0025] An exploded view 140 illustrates an expanded view of the
transducer head 124, with a reader sensor 150 illustrated by a
schematic block diagram that illustrates an air-bearing surface
(ABS) view of the reader sensor 150. In the illustrated
implementation, the reader sensor 150 is illustrated to include a
top shield 152 and a bottom shield 154, with a sensor stack 156
between the shields 152, 154 along the down-track direction of the
reader 150. The top shield 152 and the bottom shield 154 protect
the sensor stack 156 from flux from adjacent data tracks 110 on the
disc 102. The details of which are not shown, sensor stack 156
includes multiple layers, including a free layer that has a
switchable magnetic orientation. Also between the top shield 152
and the bottom shield 154, bounding the sensor stack 156 in the
cross-track directions, are side shields 158. In accordance with
this disclosure, at least one of the top shield 152 and the bottom
shield 154 is a composite shield, that includes a high magnetic
moment (HMM) material that has a magnetic moment greater than 1.0
T. In some implementations, the magnetic moment is at least 1.2 T,
or at least 1.4 T, or at least 1.8 T, or even at least 2.4 T.
[0026] FIG. 2 illustrates an ABS view of an example implementation
of a sensor structure, particularly, of a reader 200. The reader
200 includes a top shield 202 and a base or bottom shield 204
around a sensor stack 206 that has multiple layers, one of which is
a free layer with a switchable magnetic orientation. The
particulars of the sensor stack 206 are not detailed herein, and
other layers that may be in the sensor stack 206 include an AFM
layer, a pinned layer, a spacer layer, a reference layer, etc.
[0027] Also between the top shield 202 and the bottom shield 204,
in the crosstrack or lateral direction to the sensor stack 206, are
side shields 208. In the illustrated implementations, the side
shields 208 encompass all layers of the sensor stack 206, however
in other implementations, the side shields 208 may not encompass
one or more of the layers that form the sensor stack 206. The side
shields 208 may be hard magnetic or permanent magnets (PM), and may
have high magnetic moment (i.e., greater than 1.0 T) or low
magnetic moment (i.e., 1.0 T or less). The side shields 208 provide
a magnetic biasing field on the free layer in the sensor stack 206.
The side shields 208 can be directly magnetically coupled with the
top shield 202.
[0028] The top shield 202 is a composite shield, composed of at
least three layers; in this implementation, the top shield 202 has
a pinned layer 210, a reference layer 212, a spacer 211
therebetween, and a high magnetic moment (HMM) layer 215 having a
high magnetic moment. The pinned layer 210 is a magnetic layer that
has a pinned (or not readily switchable) magnetic orientation, a
low magnetic moment (i.e., 1.0 T or less) and low coercivity
(usually on the order of a few Oersteads (Oe)), and low magnetic
non-uniformity; the pinned layer 210 can be referred to as a low
magnetic moment (LMM) layer. In some implementations, the reference
layer 212 is a magnetic layer that also has a low magnetic moment
of 1.0 T or less and a low coercivity and low magnetic
non-uniformity. Together, in some implementations layers
210/211/212 are referred to as a synthetic antiferromagnetic layer,
or SAF layer.
[0029] The HMM layer 215 is magnetically coupled to the reference
layer 212 and is separated from the pinned layer 210 by the spacer
layer 211 and by the reference layer 212. The HMM layer 215 is
closer to the sensor stack 206 than the reference layer 212, and in
the illustrated implementation, the HMM layer 215 is directly in
contact with and adjacent to the sensor stack 206. In some
implementations, the HMM layer 215 is not magnetically coupled to
the stack 206. This can be due to a non-magnetic cap layer present
between the stack 206 and the HMM layer 215. In some
implementations, such a cap layer extends across the sensor stack
206 and the side shields 208, so that the side shields 208 contact
the cap layer.
[0030] As indicated above, the HMM layer 215 is formed from a
magnetic material having a magnetic moment greater than 1.0 T. In
some implementations, the magnetic moment of the HMM layer 215 is
at least 1.2 T, or at least 1.4 T, or at least 1.8 T, or even at
least 2.4 T. General examples of high magnetic moment alloys
include FeCo, FeCoN, FeSi, and FeC. Particular examples of high
magnetic moment alloys include
Fe.sub.44-46Co.sub.39-42Ni.sub.14.5-15 (2.1 T),
Fe.sub.54-56Ni.sub.27-29Co.sub.16-18 (1.8 T),
Fe.sub.86-90Cr.sub.10-14 (1.8 T),
Fe.sub.52-62Co.sub.26-36Cr.sub.10-14 (1.9 T),
Ni.sub.40-60Fe.sub.50-60 including Ni.sub.45Fe.sub.55 (1.6 T), and
"sendust" (Al.sub.5.4Fe.sub.65Si.sub.9.6 (1.1 T)), where the
subscripts indicate the range of atomic percentages for each
element in the alloy. "Permalloy" (Ni.sub.81Fe.sub.19) is not a
high magnetic moment material, as it has a magnetic moment of 1.0
T.
[0031] The HMM layer 215 may have a coercivity (e.g., a few tens of
Oersteads) similar to or slightly higher than the coercivity of the
pinned layer 210. The HMM layer 215 is sufficiently thin so that
the SSS is increased slightly, if at all, over a comparable
structure having no HMM layer. Because it is thin, its contribution
to the total coercivity of the top shield 202 is relatively low. In
some implementations, the HHM layer 215 has a thickness of at least
1 nm and in other implementations at least 2 nm. The HHM layer 215
is, in some implementations, no greater than 50 nm thick and in
other implementations no greater than 30 nm. Example thicknesses of
a discrete HMM layer, such as HMM layer 215, include 1 nm, 2 nm, 4
nm, 6 nm, 10 nm, 20 nm, and 30 nm.
[0032] The HMM layer 215 improves the PW50 of the reader 200
because the coercivity of the entire top shield 202 is the weighted
average of the coercivity of the HMM layer 215 versus the rest of
the top shield 202 (e.g., the pinned layer 210, the spacer layer
211 and the reference layer 212). The coercivity and magnetic
non-uniformity of the shield 202 is increased minimally by the
addition of the HMM layer 215, whereas the PW50 improves (i.e.,
decreases) significantly. The improved PW50 increases the
capability of the sensor 200 to read data with higher linear
density, thus allowing a recording device using the sensor 200 to
provide higher linear data density and thus more cost effective
data storage capabilities.
[0033] The particulars of the specific construction of the reader
sensor 200 are not of particular relevance to composite shield and
the HMM layer in the reader sensor 200, and a detailed discussion
of the other elements of sensor 200 is not provided herein.
[0034] FIG. 3 illustrates another schematic block diagram of an ABS
view of an example implementation of a reader 300. Various elements
or features of reader 300 are the same as or similar to the
corresponding element or feature of reader 200, unless indicated
otherwise. The reader 300 includes a top shield 302 and a base or
bottom shield 304 around a sensor stack 306. Also between the top
shield 302 and the bottom shield 304, in the crosstrack or lateral
direction to the sensor stack 306, are side shields 308.
[0035] Similar to the previous figure, the top shield 302 is a
composite shield, composed of at least three layers; however in
this implementation, the top shield 302 has a pinned layer 310, a
spacer layer 311, and a reference layer 315 having a high magnetic
moment. The composite HMM/reference layer 315 has a magnetic moment
greater than 1.0 T, and is formed from a mixture or combination
(e.g., an alloy) of a magnetic material having a magnetic moment
greater than 1.0 T and a second magnetic material having a magnetic
moment of 1.0 T or less. The ratio of the materials should be such
that the resulting material has a magnetic moment greater than 1.0
T, in some implementations, at least 1.2 T, or at least 1.4 T, or
at least 1.8 T, or even at least 2.4 T
[0036] In other implementations, the HMM/reference layer 315 is a
mixture or combination (e.g., an alloy) of multiple magnetic
materials, at least one of which has a magnetic moment greater than
1.0 T. The pinned layer 310 is a low magnetic moment (LMM) layer,
having a magnetic moment no greater than 1.0 T.
[0037] The HMM/reference layer 315 typically has a thickness
similar to or equal to the thickness the reference layer would be
if no HMM material were present. In some implementations, the
HMM/reference layer 315 has a thickness of at least 5 nm, 10 nm, 20
nm and in other implementations at least 30 nm.
[0038] The HMM/reference layer 315 is separated from the pinned
layer 310 by the spacer layer 311. The HMM/reference layer 315 is
closer to the sensor stack 306 than the pinned layer 310, and in
the illustrated implementation, the HMM/reference layer 315 is The
HMM/reference layer 315 is not magnetically coupled to stack.
[0039] FIG. 4 illustrates another schematic block diagram of an ABS
view of an example implementation of a reader 400. Various elements
or features of reader 400 are the same as or similar to the
corresponding element or feature of readers 200, 300, unless
indicated otherwise. This reader 400 includes a top shield 402 and
a base or bottom shield 404 around a sensor stack 406. Also between
the top shield 402 and the bottom shield 404, in the crosstrack or
lateral direction to the sensor stack 406, are side shields
408.
[0040] In this implementation, the bottom shield 404 is a composite
shield, composed of at least three layers; in this implementation,
the bottom shield 404 has a pinned layer 410, a reference layer
412, a spacer layer 411 therebetween, and a HMM layer 415 having a
high magnetic moment. The HMM layer 415 has a magnetic moment
greater than 1.0 T, whereas the pinned layer 410 has a low magnetic
moment (LMM) no greater than 1.0 T.
[0041] The HMM layer 415 is magnetically coupled to the reference
layer 412 and is separated from the pinned layer 410 by the spacer
layer 411 and by the reference layer 412. The HMM layer 415 is
closer to the sensor stack 406 than the pinned layer 410 and the
reference layer 412, and in the illustrated implementation, the HMM
layer 415 is directly in contact with and adjacent to the sensor
stack 406.
[0042] FIG. 5 illustrates another schematic block diagram of an ABS
view of an example implementation of a reader 500. Various elements
or features of reader 500 are the same as or similar to the
corresponding element or feature of readers 200, 300, 400, unless
indicated otherwise. The reader 500 includes a top shield 502 and a
base or bottom shield 504 around a sensor stack 506. Also between
the top shield 502 and the bottom shield 504, in the crosstrack or
lateral direction to the sensor stack 506, are side shields
508.
[0043] Similar to the previous figure, the bottom shield 504 is a
composite shield, composed of at least three layers; however in
this implementation, the bottom shield 504 has a pinned layer 510,
a spacer layer 511, and a reference layer 515 having a high
magnetic moment. The HMM/reference layer 515 has a magnetic moment
greater than 1.0 T, and is formed from a mixture or combination
(e.g., an alloy) of multiple materials, at least one of which has a
magnetic moment greater than 1.0 T. The pinned layer 510 is a low
magnetic moment (LMM) layer, having a magnetic moment no greater
than 1.0 T.
[0044] The HMM/reference layer 515 is separated from the pinned
layer 510 by the spacer layer 511. The HMM/reference layer 515 is
closer to the sensor stack 506 than the pinned layer 510, and in
the illustrated implementation, the HMM/reference layer 515 is in
direct contact with and adjacent to the sensor stack 506.
[0045] Various implementations of reader sensors were modeled, with
a sensor stack having a 30 nm thick pinned layer and a reference
layer and HMM layer that both varied in thickness. FIG. 6 shows the
theoretical improvement (i.e., reduction) of PW50 due to the HMM
material proximate to the sensor stack and directly magnetically
coupled to the rest of the composite shield. The baseline sensor
had a 30 nm reference layer with no HMM layer. The modeled sensor
stacks were: 26 nm reference layer+4 nm HMM, 24 nm reference
layer+6 nm HMM, 20 nm reference layer+10 nm HMM, 12 nm reference
layer+18 nm HMM, and 4 nm reference layer+26 nm HMM. Two HMM
materials were used for the models, a 1.8 T HMM and a 2.4 T HMM. As
another baseline, a 1.0 T material was used.
[0046] As can be seen in FIG. 6, presence of the HMM layer reduces
the PW50. The PW50 improves as the magnetic moment increased (i.e.,
1.0 T versus 1.8 T versus 2.4 T). For example, a 10 nm HMM (1.8 T)
improves the PW50 by 0.6 nm, and a 10 nm HM (2.4 T) improves the
PW50 by 0.9 nm. The PW50 also improves as the thickness of the HMM
layer increases. For example, a 10 nm HMM (2.4 T) improves the PW50
by 0.9 nm and an 18 nm HMM (2.4 T) improves the PW50 by 1.2 nm.
Decreased PW50 improves linear density capabilities of the
reader.
[0047] Having the HMM alloyed with a lower magnetic moment
material, as in the implementations shown and described in respect
to FIGS. 3 and 5, also improves the PW50, although not as much as a
discrete layer of HMM. As can be seen in FIG. 7, the PW50 decreases
with both a discrete HMM layer or an HMM alloy layer, although the
discrete HMM layer reduces PW50 more effectively.
[0048] A composite shield, either top shield or bottom shield,
having a layer with a high magnetic moment greater than 1.0 T,
improves PW50 while providing acceptable increase in coercivity and
magnetic non-uniformity, all which enhances linear density
capabilities of the reader.
[0049] All of the read sensors described above, readers 200, 300,
400, 500 and variations thereof, can be fabricated by conventional
methods, including plating, deposition, etching, milling, and other
conventional processing techniques.
[0050] In reference now to FIG. 8, a flowchart illustrates an
example method for forming a read sensor having a composite top
shield with a discrete HMM layer, such as the sensor 200 of FIG. 2.
The method involves operation 802 of forming a bottom shield layer
on a substrate. This operation does not require forming the bottom
shield directly on the substrate, as intervening materials/layers
may be present between the bottom shield and substrate. A sensor
stack is formed on the bottom shield in operation 804. This
operation does not require forming the sensor stack directly on the
substrate, as intervening materials/layers may be present between
the bottom shield and sensor stack. In operation 806, side shields
are formed on the bottom shield around the sensor stack. A
composite top shield is formed on the sensor stack in operations
808 through 812. In operation 808, a layer of HMM material (i.e.,
having a magnetic moment of greater than 1.0 T) is formed. In this
particular method, the HMM layer is formed directly on and in
contact with the sensor stack. In operation 810, a reference layer
is formed, in this particular method, on and in contact with the
HMM layer. A spacer layer and then a pinned layer are formed in
operation 812 on the reference layer.
[0051] An alternate example method for forming a read sensor is
illustrated in FIG. 9, the read sensor having a composite top
shield with an alloy HMM layer, such as the sensor 300 of FIG. 3.
The method involves operation 902 of forming a bottom shield layer
on a substrate. This operation does not require forming the bottom
shield directly on the substrate, as intervening materials/layers
may be present between the bottom shield and substrate. A sensor
stack is formed on the bottom shield in operation 904. This
operation does not require forming the sensor stack directly on the
substrate, as intervening materials/layers may be present between
the bottom shield and sensor stack. In operation 906, side shields
are formed on the bottom shield around the sensor stack. A
composite top shield is formed on the sensor stack in operations
908 through 910. In operation 908, a HMM layer (i.e., having a
magnetic moment of greater than 1.0 T) is formed; the HMM layer is
composed of multiple magnetic materials, at least one of which has
a magnetic moment greater than 1.0 T. In this particular method,
the HMM layer is formed directly on and in contact with the sensor
stack. In operation 910, a spacer layer and then a pinned layer are
formed on the reference layer.
[0052] The above specification and examples provide a complete
description of the structure and use of exemplary implementations
of the invention. The above description provides specific
implementations. It is to be understood that other implementations
are contemplated and may be made without departing from the scope
or spirit of the present disclosure. The above detailed
description, therefore, is not to be taken in a limiting sense.
While the present disclosure is not so limited, an appreciation of
various aspects of the disclosure will be gained through a
discussion of the examples provided.
[0053] Unless otherwise indicated, all numbers expressing feature
sizes, amounts, and physical properties are to be understood as
being modified by the term "about." Accordingly, unless indicated
to the contrary, the numerical parameters set forth are
approximations that can vary depending upon the desired properties
sought to be obtained by those skilled in the art utilizing the
teachings disclosed herein.
[0054] As used herein, the singular forms "a", "an", and "the"
encompass implementations having plural referents, unless the
content clearly dictates otherwise. As used in this specification
and the appended claims, the term "or" is generally employed in its
sense including "and/or" unless the content clearly dictates
otherwise.
[0055] Spatially related terms, including but not limited to,
"bottom," "lower", "top", "upper", "beneath", "below", "above", "on
top", "on," etc., if used herein, are utilized for ease of
description to describe spatial relationships of an element(s) to
another. Such spatially related terms encompass different
orientations of the device in addition to the particular
orientations depicted in the figures and described herein. For
example, if a structure depicted in the figures is turned over or
flipped over, portions previously described as below or beneath
other elements would then be above or over those other
elements.
[0056] Since many implementations 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 implementations may be
combined in yet another implementation without departing from the
recited claims.
* * * * *