U.S. patent application number 12/502104 was filed with the patent office on 2011-01-13 for trapezoidal back bias and trilayer reader geometry to enhance device performance.
This patent application is currently assigned to SEAGATE TECHNOLOGY LLC. Invention is credited to Yonghua Chen, Beverley Craig, Kaizhong Gao, Jiaoming Qiu, Vladyslav A. Vas'ko, Zhongyan Wang.
Application Number | 20110007426 12/502104 |
Document ID | / |
Family ID | 43427288 |
Filed Date | 2011-01-13 |
United States Patent
Application |
20110007426 |
Kind Code |
A1 |
Qiu; Jiaoming ; et
al. |
January 13, 2011 |
TRAPEZOIDAL BACK BIAS AND TRILAYER READER GEOMETRY TO ENHANCE
DEVICE PERFORMANCE
Abstract
A magnetoresistive sensor having a trilayer sensor stack with
two ferromagnetic freelayers separated by a nonmagnetic spacer
layer is disclosed. The sensor is biased with a back biasing magnet
adjacent a back of the trilayer sensor. The back biasing magnet,
the trilayer sensor stack, or both have substantially trapezoidal
shapes to enhance the biasing field and to minimize noise. In some
embodiments, the trilayer sensor or back bias magnet have a shape
designed to stabilize a micromagnetic "C" shape or concentrate
magnetic flux in the trilayer sensor stack.
Inventors: |
Qiu; Jiaoming; (Saint Paul,
MN) ; Gao; Kaizhong; (Eden Prairie, MN) ;
Chen; Yonghua; (Eden Prairie, MN) ; Craig;
Beverley; (Culmore, GB) ; Wang; Zhongyan; (San
Ramon, CA) ; Vas'ko; Vladyslav A.; (Apple Valley,
MN) |
Correspondence
Address: |
KINNEY & LANGE, P.A.
312 SOUTH 3RD STREET, THE KINNEY & LANGE BUILDING
MINNEAPOLIS
MN
55415
US
|
Assignee: |
SEAGATE TECHNOLOGY LLC
Scotts Valley
CA
|
Family ID: |
43427288 |
Appl. No.: |
12/502104 |
Filed: |
July 13, 2009 |
Current U.S.
Class: |
360/313 ;
G9B/5.104 |
Current CPC
Class: |
G11B 5/127 20130101;
G11B 5/3932 20130101; G11B 5/39 20130101 |
Class at
Publication: |
360/313 ;
G9B/5.104 |
International
Class: |
G11B 5/33 20060101
G11B005/33 |
Claims
1. A magnetoresistive sensor comprising: a trilayer sensor stack
comprising two ferromagnetic freelayers separated by a nonmagnetic
spacer; and a back biasing magnet adjacent a back end of the
trilayer sensor stack; wherein at least one of the trilayer sensor
stack and the back biasing magnet has a shape that stabilizes a
micromagnetic "C" state or concentrates magnetic flux in the
trilayer sensor stack.
2. The magnetoresistive sensor of claim 1 wherein the back bias
magnet has a substantially trapezoidal shape.
3. The magnetoresistive sensor of claim 2 wherein the trilayer
sensor stacks have a substantially trapezoidal shape.
4. The magnetoresistive sensor of claim 1 wherein the trilayer
sensor stack has a substantially rectangular shape.
5. The magnetoresistive sensor of claim 1, wherein the nonmagnetic
spacer layer of the trilayer sensor stack is an insulator layer and
the trilayer sensor stack is a tunneling magnetoresistive
sensor.
6. The magnetoresistive sensor of claim 1, wherein the biasing
magnet provides vertical bias to the trilayer sensor stack.
7. The magnetoresistive sensor of claim 1, wherein the biasing
magnet is a hard magnetic material.
8. The magnetoresistive sensor of claim 7, wherein the hard
magnetic material is a cobalt-platinum based alloy or iron-platinum
based alloy.
9. The magnetoresistive sensor of claim 1, wherein the back biasing
magnet is isolated from the trilayer sensor stack by an insulating
layer.
10. The magnetoresistive sensor of claim 1, wherein the
ferromagnetic layers in the trilayer sensor stack are selected from
the group consisting of nickel-iron, copper-iron, and
nickel-iron-copper alloys.
11. The magnetoresistive sensor of claim 1, and further comprising:
lateral side shields adjacent both sides of the trilayer sensor
stack and the back biasing magnet.
12. The magnetoresistive sensor of claim 11, wherein the lateral
side shields are isolated from the trilayer sensor stack and the
vertical biasing magnet by a side shield insulating layer
comprising aluminum oxide.
13. A magnetoresistive sensor comprising: a trilayer sensor stack
comprising two ferromagnetic layers separated by a nonmagnetic
spacer layer, and having a front width proximate an air bearing
surface and a back width distal from the air bearing surface; and a
back biasing magnet adjacent the back width of the trilayer sensor
stack, the back biasing magnet having a front width that is about
the same as the back width of the trilayer stack, and a back width;
wherein at least the back biasing magnet has a trapezoidal
shape.
14. The magnetoresistive sensor of claim 13 wherein the back width
of the trilayer sensor stack is larger than the front width of the
trilayer stack.
15. The magnetoresistive sensor of claim 13 wherein the back
biasing magnet provides bias to the trilayer sensor stack in a
direction generally perpendicular to the air bearing surface.
16. The magnetoresistive sensor of claim 13 wherein the back width
of the biasing magnet is larger than its front width.
17. The magnetoresistive sensor of claim 13 and further comprising:
lateral side shields adjacent both sides of the trilayer sensor
stack and the back biasing magnet.
18. The magnetoresistive sensor of claim 13 wherein the back width
of the trilayer sensor stack is about the same as the front width
of the trilayer sensor stack.
19. A magnetoresistive sensor comprising: a trilayer sensor stack
comprising first and second free layers separated by a nonmagnetic
spacer; a permanent magnet located on an opposite side of the
trilayer sensor stack as an air bearing surface, the permanent
magnet having a front side width less than a back side width
wherein a front side is closest to the trilayer sensor stack; a
first and second side shield adjacent the trilayer sensor stack and
permanent magnet; a top shield adjacent the first free layer; and a
bottom shield adjacent the second free layer.
20. The magnetoresistive sensor of claim 19, wherein the trilayer
sensor stack has a front side width less than the back side width
and a front side is closest to the air bearing surface.
Description
BACKGROUND
[0001] In a magnetic data storage and retrieval system, a magnetic
recording head typically 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 or layers of the MR sensor, which in turn causes a
change in electrical resistivity of the MR sensor. The sensing
layers are often called "free" layers, since the magnetization
vectors of the sensing layers are free to rotate in response to
external magnetic flux. 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 as necessary to recover the
information encoded on the disc.
[0002] MR sensors have been developed that can be characterized in
three general categories: (1) anisotropic magnetoresistive (AMR)
sensors, (2) giant magnetoresistive (GMR) sensors, including spin
valve sensors and multilayer GMR sensors, and (3) tunneling giant
magnetoresistive (TGMR) sensors.
[0003] Tunneling GMR (TGMR) sensors have a series of alternating
magnetic and non-magnetic layers similar to GMR sensors, except
that the magnetic layers of the sensor are separated by an
insulating film thin enough to allow electron tunneling between the
magnetic layers. The resistance of the TGMR sensor depends on the
relative orientations of the magnetization of the magnetic layers,
exhibiting a minimum for a configuration in which the
magnetizations of the magnetic layers are parallel and a maximum
for a configuration in which the magnetizations of the magnetic
layers are anti-parallel.
[0004] For all types of MR sensors, magnetization rotation occurs
in response to magnetic flux from the disc. As the recording
density of magnetic discs continues to increase, the width of the
tracks as well as the bits on the disc must decrease. This
necessitates increasingly smaller MR sensors as well as narrower
shield-to-shield spacings. As MR sensors become smaller in size,
particularly for sensors with dimensions less than about 0.1
micrometers (.mu.m), the sensors have the potential to exhibit an
undesirable magnetic response to applied fields from the magnetic
disc. MR sensors must be designed in such a manner that even small
sensors are free from magnetic noise and provide a signal with
adequate amplitude for accurate recovery of the data written on the
disc.
[0005] GMR and TGMR readers can use the resistance between the
freelayer and a reference layer to detect media stray fields so as
to read back stored information. Magnetization of the reference
layer is fixed through an antiferromagnetic coupling interaction by
a ferromagnetic pinned layer which is again pinned by
antiferromagnetic (AFM) material. The reference and the pinned
layer, together with the antiferromagnetic coupling layer between
them, are the so-called synthetic antiferromagnetic (SAF)
structure. This kind of configuration has two major disadvantages.
The first one is high shield-to-shield spacing due to the
complicated multi-layer structure. The continued reduction of the
shield-to-shield spacing requirement is limited by the emerging
instability of individual layers in the sensor as they become
thinner. For example, the pinning strength of the AFM materials
decreases with a reduction in their thickness. As a consequence,
weakly pinned SAF structures lead to an increase of sensor noise
when the reference layer is not satisfactorily pinned. The second
disadvantage of traditional GMR and TGMR sensors is their low
sensitivity because the freelayer is the only response layer.
Reducing the free layer thickness correspondingly reduces the
sensitivity.
[0006] Trilayer readers with dual free-layers are one solution to
address these issues. In a trilayer structure, two free-layers with
easy axes of magnetization in a scissor orientation are used to
detect media magnetic flux. Synthetic antiferromagnetic (SAF) and
antiferromagnetic (AFM) layers are not needed and free layer
biasing comes from the combination of backend permanent magnet and
demagnetization fields when both freelayers have ends at the air
bearing surface. However, the biasing field from the back end
magnet decays rapidly away from the magnet. The freelayer portion
of the trilayer sensor in the vicinity of the air bearing surface
(ABS) suffers from insufficient bias and the magnetization scissor
angle is open too much.
SUMMARY
[0007] A magnetoresistive sensor includes a trilayer sensor stack
comprising two ferromagnetic freelayers separated by a nonmagnetic
spacer layer with a front width proximate an ABS, and a back width
distal from an ABS and a back biasing magnet with a trapezoidal
shape with a front width and a back width. The front width of the
biasing magnet is adjacent the back width of the trilayer sensor
stack and is about the same as the back width of the sensor stack.
The back width of the biasing magnet is larger than the front
width. The trilayer sensor stack can have a rectangular shape or a
trapezoidal shape wherein the back width is larger than the front
width. The trapezoidal shape concentrates the magnetic field at the
front of the biasing magnet in the vicinity of the sensor stack.
The trapezoidal shape also encourages "C" type micromagnetic
magnetization patterns in the trilayer sensor stack, minimizing
signal noise due to "C" to "S" switching during sensor
operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1A is a schematic diagram showing micromagnetic
magnetization patterns in a rectangular sample.
[0009] FIG. 1B is a schematic diagram showing a "C" type
micromagnetic magnetization pattern in the sample of FIG. 1A.
[0010] FIG. 1C is a schematic diagram showing an "S" type
micromagnetic magnetization pattern in the sample of FIG. 1A.
[0011] FIG. 1D is a schematic showing a "C" type micromagnetic
magnetization pattern in a trapezoidal sample.
[0012] FIG. 2 is a top view of a first example of a read head in
accord with the present invention.
[0013] FIG. 3 is an ABS view of the read head in FIG. 2 in accord
with the present invention.
[0014] FIG. 4A is a schematic top view of the trilayer sensor in
FIG. 2 showing biasing in the absence of external bit flux.
[0015] FIG. 4B is a schematic top view of the trilayer sensor in
FIG. 4A under the influence of a first state of data.
[0016] FIG. 4C is a schematic top view of the trilayer sensor in
FIG. 4A under the influence of a second state of data.
[0017] FIG. 5 is a top view of a second example of a read head in
accord with the present invention.
[0018] FIG. 6 is an ABS view of the read head in FIG. 5 in accord
with the present invention.
[0019] FIG. 7A is a schematic top view of the trilayer sensor in
FIG. 5 showing biasing in the absence of external bit flux.
[0020] FIG. 7B is a schematic top view of the trilayer sensor in
FIG. 7A under the influence of a first state of data.
[0021] FIG. 7C is a schematic top view of the trilayer sensor in
FIG. 7A under the influence of a second state of data.
[0022] FIGS. 8A-8K illustrate the fabrication steps to produce the
read head illustrated in FIGS. 2 and 3.
[0023] FIGS. 9A-9K illustrate the fabrication steps to produce the
read head illustrated in FIGS. 5 and 6.
DETAILED DESCRIPTION
[0024] The inventive shapes disclosed herein increase the
performance of a reader by increasing the bias field at the front
of a back bias magnet and by decreasing signal noise. The origin of
these effects is shown in FIGS. 1A-1C. FIG. 1A illustrates possible
micromagnetic magnetization patterns in a rectangular magnetic
sample under a magnetization oriented generally from the left to
right. Magnetization vectors 12' and 14' originate at the corners
of the sample and are directed to the center where they converge at
magnetization vector 10'. Magnetization vector 10' diverges into
vectors 16' and 18' as it approaches the right side of the sample.
FIG. 1 shows all possible micromagnetic magnetization patterns. Two
patterns are energetically favored. FIG. 1B illustrates a "C"
pattern comprised of vectors 12', 10' and 16'. An alternative "C"
pattern comprises vectors 14', 10' and 18'. FIG. 1C illustrates an
"S" pattern comprised of vectors 12', 10' and 18' or alternatively
vectors 14', 10' and 16'. The energy difference between the "C"
state and the "S" state is very small and during magnetic
switching, thermally activated transitions between both patterns
contribute to measurable sensor noise.
[0025] By changing the geometry of a magnetic element, one or the
other of the "C" and "S" states can be energetically favored. FIG.
1D illustrates how the "C" state can be favored by a trapezoidal
shape of the micromagnetic element. This shape will be used in what
follows to tailor magnetization in the back bias permanent magnet
of a trilayer reader as well as in the freelayers of the reader
itself. Although trapezoidal geometries are discussed herein to
favor "C" shape micromagnetic magnetization patterns, it should be
noted that other geometries such as half moon shapes can be used to
obtain similar beneficial results.
[0026] FIGS. 2 and 3 illustrate one aspect of the trilayer reader
of the present invention. FIG. 2 is a top view of trilayer read
head 10, and FIG. 3 is an ABS view of read head 10. Read head 10
comprises rectangular trilayer reader stack 20 (comprising
ferromagnetic freelayers 22 and 24 and spacer layer 26) in front of
trapezoidal back bias magnet 30. Magnetic side shields 40 and 42
abut both sides of bias magnet 30 and trilayer reader stack 20.
Trilayer reader stack 20, bias magnet 30, and side shields 40 and
42 are separated from each other by insulating layer 50. Side
shields 40 and 42 may also be replaced by an insulator preferably
an oxide of aluminum.
[0027] The ABS view of trilayer read head 10 in FIG. 3 shows top
shield 60, bottom shield 70 and side shields 40 and 42 adjacent
trilayer reader stack 20 and insulator layer 50. Ferromagnetic
freelayers 22 and 24 of trilayer reader stack 20 are separated by
spacer layer 26. If spacer layer 26 is a nonmagnetic electrical
conductor, read head 10 is a GMR head. If spacer layer 26 is a
nonmagnetic electrical insulator, read head 10 is a TGMR head. Read
head 10 can be a current perpendicular to plane (CPP) head wherein
electrical contact is made to trilayer reader stack 20 through top
shield 60 and bottom shield 70.
[0028] If spacer layer 26 is nonmagnetic, and electrically
conducting, it may be fabricated from, for example, copper. If
spacer layer 26 is nonconducting, it may be fabricated from, for
example, aluminum oxide (Al.sub.2O.sub.3 or Al.sub.xO where x may
or may not be an integer) or magnesium oxide. Ferromagnetic layers
22 and 24 may be fabricated from magnetic material such as, for
example, nickel-iron-cobalt (Ni--Fe--Co) compositions. The shield
layers may be fabricated from, for example, a soft magnetic
material such as nickel-iron (Ni--Fe). Back bias magnet 30 may be
fabricated from a permanent magnet material such as, for example, a
cobalt-platinum (Co--Pt) alloy.
[0029] The operation of read head 10, according to one aspect of
the invention is described in conjunction with FIGS. 4A-4C. FIGS.
4A, 4B and 4C show top views of read head 10 with magnetization
vector 30' of back bias layer 30 oriented with respect to
magnetization vectors 22' and 24' of freelayers 22 and 24 to
achieve optimum response of freelayers 22 and 24 to external
magnetic fields. In the absence of back bias magnetization,
freelayer magnetization vectors 22' and 24' would be antiparallel
and commonly parallel to the ABS. Under the bias of magnetization
vector 30', they arrange in a scissor orientation for optimum
sensitivity. One benefit of the trapezoidal shape of back bias
magnet 30 is that the smaller base near the back of trilayer reader
stack 20 results in magnetic flux concentration in that region
resulting in deeper penetration of the biasing field into reader
stack 20 in the direction of the ABS.
[0030] FIGS. 4A-4C illustrate the effect of varying bit
magnetization on recorded media on the magnetization directions 22'
and 24' of first freelayer 22 and second freelayer 24 respectively.
FIG. 4A shows trilayer reader stack 10 in a quiescent magnetic
state when it is not under the influence of magnetic flux emanating
from recording media. The angle of magnetization between first
ferromagnetic freelayer 22 and second ferromagnetic freelayer 24 at
the ABS is in a scissors relation for optimum sensor response. FIG.
4B is a top view of read head 10 showing trilayer reader stack 20
under the influence of a first state of data D1 corresponding to a
positive bit. This first state of data causes the angle of
magnetization between first freelayer 22 and second freelayer 24 to
increase at the ABS. When this occurs, the resistance across
trilayer reader stack 20 changes and is detected when a sense
current is passed through trilayer reader stack 20. FIG. 4C is a
top view of read head 10 showing trilayer reader stack 20 under the
influence of a second state of data D2 corresponding to a negative
bit. This second state of data causes the angle of magnetization
between first freelayer 22 and second freelayer 24 to decrease at
the ABS. As with the first state of data, the second state of data
causes a change in resistance across trilayer reader stack 20 and
is detected when a sense current is passed through trilayer reader
stack 20.
[0031] FIGS. 5 and 6 illustrate another aspect of the invention.
FIG. 5 is a top view of trilayer reader head 110, and FIG. 6 is an
ABS view of read head 110. Read head 110 comprises trapezoidal
trilayer reader stack 120 comprising ferromagnetic freelayers 122
and 124 and spacer layer 126 in front of trapezoidal back bias
magnet 130. Magnetic side shields 140 and 142 are adjacent both
sides of back bias magnet 130 and freelayer stack 120. Trilayer
reader stack 120, back bias magnet 130, and side shields 140 and
142 are separated from each other by insulating layer 150. Side
shields 140 and 142 may also be replaced by an insulator,
preferably an oxide of aluminum. In this aspect of the invention,
trilayer reader stack 120 has a trapezoidal shape. A benefit of the
trapezoidal shape is that a "C" pattern of micromagnetic
magnetization in reader stack 120 is preferred. The ABS view of
trilayer read head 110 in FIG. 6 shows top shield 160, bottom
shield 170 and side shields 140 and 142 adjacent trilayer reader
stack 120 and insulator layer 150. Ferromagnetic freelayers 122 and
124 of trilayer reader stack 120 are separated by spacer layer 126.
If spacer layer 126 is nonmagnetic, read head 110 is a GMR head. If
spacer layer 126 is an insulator, read head 110 is a TGMR head.
Read head 110 can be a current perpendicular to plane (CPP) head
wherein electrical contact is made to trilayer reader stack 120
through top shield 160 and bottom shield 170.
[0032] If spacer layer 126 is nonmagnetic and electrically
conducting, it may be fabricated from, for example, copper. If
spacer layer 126 is nonconducting, it may be fabricated from, for
example, aluminum oxide (Al.sub.2O.sub.3 or Al.sub.xO where x may
be not be an integer) or magnesium oxide. Ferromagnetic layers 122
and 124 may be fabricated from magnetic materials, such as, for
example, nickel-iron-cobalt (Ni--Fe--Co) compositions. The shield
layers may be fabricated from, for example, a soft magnetic
material such as nickel-iron (Ni--Fe). Back bias magnet 130 may be
fabricated from a permanent magnet material such as, for example, a
cobalt-platinum (Co--Pt) alloy.
[0033] The operation of read head 110 according to one aspect of
the invention is described in conjunction with FIGS. 7A-7C. FIGS.
7A, 7B and 7C show top views of read head 110 with magnetization
vector 130' of back bias layer 130 oriented with respect to
magnetization vectors 122' and 124' of freelayers 122 and 124 to
achieve optimum response of freelayers 122 and 124 to external
magnetic fields. In the absence of back bias magnetization 130',
freelayer magnetization vectors 122' and 124' would be antiparallel
and parallel to ABS 160. Under the back bias of magnetization 130',
they arrange in a scissor orientation for optimum sensitivity. A
benefit of the trapezoidal shape of back bias magnet 130 is that
the smaller base at trilayer reader stack 120 results in magnetic
flux concentration in that region resulting in deeper penetration
of the biasing field into reader stack 120 in the direction of the
ABS.
[0034] FIGS. 7A-7C illustrate the effect of varying bit
magnetizations on recorded media on the magnetization directions
122' and 124' of first freelayer 122 and second freelayer 124
respectively. FIG. 7A shows trilayer reader stack 120 in a
quiescent magnetic state when it is not under the influence of
magnetic flux emanating from recording media. The angle of
magnetization between first ferromagnetic freelayer 122 and second
ferromagnetic freelayer 124 at the ABS is in a scissors relation
for optimum sensor response. FIG. 7B is a front view of read head
110 showing trilayer reader stack 120 under the influence of a
first state of data D1 corresponding to a positive bit. This first
state of data causes the angle of magnetization between first
freelayer 122' and second freelayer 124' to increase at the ABS.
When this occurs, the resistance across trilayer reader stack 120
changes and is detected when a sense current is passed through
trilayer reader stack 120. FIG. 7C is a top view of read head 110
showing trilayer reader stack 120 under the influence of a second
state of data D2 corresponding to a negative bit. This second state
of data causes the angle of magnetization between first freelayer
122' and second freelayer 124' to decrease at the ABS. As with the
first state of data, the second state of data causes a change in
resistance across trilayer reader stack 120 and is detected when a
sense current is passed through trilayer reader stack 120.
[0035] The operation of read head 110 is similar to that discussed
for read head 10 and schematically illustrated in FIG. 4A-4C, with
one exception. The trapezoidal shape of trilayer reader stack 120
encourages a "C" type of micromagnetic magnetization in freelayers
124 and 126. This forces the magnetization vectors into
orientations parallel to the ABS and discourages the formation of
"S" type micromagnetic magnetization patterns in the freelayers,
thereby minimizing noise resulting from "C" type to "S" type
switching behavior during operation.
[0036] The formation of reader 10 with trapezoidal back bias magnet
30 shown in FIGS. 2 and 3 is schematically illustrated in FIGS.
8A-8K. FIG. 8A shows a substrate coated with reader stack 220. The
reader stack can be a GMR or a TGMR stack. In the next step,
photoresist (PR) layer 260, covering the center portion of reader
stack 220, is deposited as shown in FIG. 8B. In the next step,
shown in FIG. 8C, exposed reader stack 220 has been removed by ion
beam machining or etching or by other means known in the art.
Following removal of exposed reader stack 220, insulating layer 250
is deposited on each side of reader stack 220 and PR layer 260 as
shown in FIG. 8D. Insulating layer 250, as mentioned earlier, is
preferably aluminum oxide and is preferably deposited by atomic
layer deposition (ALD). In the next step permanent bias magnet 230
is then deposited as shown in FIG. 8E comprising reader stack 220
with bias magnets 230 above and below reader stack 220 separated
from reader stack 220 by insulating layers 250. The structure in
FIG. 8E is then covered with PR layer 260b with a narrow center
width and wider ends as shown in FIG. 8F. The exposed structure not
covered with PR layer 260b is then removed by ion beam machining or
etching or other means known in the art as shown in FIG. 8G.
Insulator layer 250 is then deposited on each side of the structure
covered with PR layer 260b as shown in FIG. 8H. Side shields 240
and 242 are deposited to form the structure shown in FIG. 8I. Side
shields 240 and 242 could be replaced with insulator layer 250 if
needed. Removing PR layer 260b in FIG. 8I reveals the structure
shown in FIG. 8J comprising rectangular reader stack 220 separated
from side shields 240 and 242 and trapezoidal bias magnets 230 by
insulating layer 250. Masking the top half of the structure shown
in FIG. 8J and removing the remainder creates reader structure 10
shown in FIG. 8K comprising rectangular reader stack 220, side
shields 240 and 242 and trapezoidal back bias magnet 230 separated
from each other by insulating layer 250. Air bearing surface ABS is
indicated in FIG. 8K.
[0037] The formation of reader 110 with trapezoidal back bias
magnet 130 and trapezoidal reader stack 120 shown in FIGS. 5 and 6
is schematically illustrated in FIGS. 9A-9K. FIG. 9A shows a
substrate coated with reader stack 320. The reader stack can be a
GMR or a TGMR stack. Photoresist (PR) layer 360, covering the
center portion of reader stack 320, is deposited as shown in FIG.
9B. In the next step, shown in FIG. 9C, exposed reader stack 320
has been removed by ion beam machining or etching or by other means
known in the art. Following removal of exposed reader stack 320,
insulating layer 350 is deposited on each side of reader stack 320
and PR layer 360 as shown in FIG. 9D. Insulating layer 350, as
mentioned earlier, is preferably aluminum oxide and is preferably
deposited by atomic layer deposition (ALD). In the next step,
permanent bias magnet 330 is then deposited as shown in FIG. 9E
comprising reader stack 320 with bias magnets 330 above and below
reader stack 320 separated from reader stack 320 by insulating
layer 350. The structure in FIG. 9E is then covered with PR layer
360b with a narrow center width and asymmetrically wider ends as
shown in FIG. 9H. The exposed structure not covered with PR layer
360b is then removed by ion beam machining or etching or other
means known to produce the structure shown in FIG. 9G. Insulator
layer 350 is then deposited on each side of the structure in FIG.
9G to produce the structure shown in FIG. 9H. Side shields 340 and
342 are deposited on each side to form the structure shown in FIG.
9I. Side shields 340 and 342 could be replaced with insulator layer
350 if needed. Removing PR layer 360b in FIG. 9K reveals the
structure shown in FIG. 9J comprising trapezoidal reader stack 320,
side shields 340 and 342 and trapezoidal bias magnet 330. All are
separated by insulating layer 350. Masking the top half of the
structure shown in FIG. 9J and removing the remainder creates
reader structure 110 shown in FIG. 9K comprising trapezoidal
trilayer reader stack 320, side shields 340 and 342, and
trapezoidal back bias magnet 330 separated from each other by
insulating layer 350. Air bearing surface ABS is indicated in FIG.
9K.
[0038] While the invention has been described with reference to an
exemplary embodiment(s), it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
* * * * *