U.S. patent application number 13/691525 was filed with the patent office on 2014-06-05 for scissor magnetic read head with wrap-around magnetic shield.
This patent application is currently assigned to HGST Netherlands B.V.. The applicant listed for this patent is HGST NETHERLANDS B.V.. Invention is credited to Xiaozhong Dang, Quang Le, Simon H. Liao, Guangli Liu, Stefan Maat, David J. Seagle, Petrus A. Van Der Heijden.
Application Number | 20140153138 13/691525 |
Document ID | / |
Family ID | 50825229 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140153138 |
Kind Code |
A1 |
Le; Quang ; et al. |
June 5, 2014 |
SCISSOR MAGNETIC READ HEAD WITH WRAP-AROUND MAGNETIC SHIELD
Abstract
A magnetic scissor type magnetic read head having magnetic side
shielding for reduced effective track width and having side biasing
for improved stability. The read head includes first and magnetic
side shields that each include first and second magnetic layers and
an anti-parallel exchange coupling layer sandwiched there-between.
The magnetic layers of the side shields are anti-parallel coupled
with one another such that one of the magnetic layers has its
magnetization oriented in a first direction parallel with the air
bearing surface and the second magnetic layer has its magnetization
oriented in a second direction that is opposite to the first
direction and also parallel with the air bearing surface. These
magnetizations of the first and second magnetic layers provide a
bias field that stabilizes the magnetization of the free magnetic
layers of the sensor stack to prevent flipping of the
magnetizations of these layers.
Inventors: |
Le; Quang; (San Jose,
CA) ; Liao; Simon H.; (Fremont, CA) ; Liu;
Guangli; (Pleasanton, CA) ; Maat; Stefan; (San
Jose, CA) ; Dang; Xiaozhong; (Fremont, CA) ;
Seagle; David J.; (Morgan Hill, CA) ; Van Der
Heijden; Petrus A.; (Cupertino, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HGST NETHERLANDS B.V. |
Amsterdam |
|
NL |
|
|
Assignee: |
HGST Netherlands B.V.
Amsterdam
NL
|
Family ID: |
50825229 |
Appl. No.: |
13/691525 |
Filed: |
November 30, 2012 |
Current U.S.
Class: |
360/294 ;
360/319 |
Current CPC
Class: |
G11B 21/18 20130101;
G11B 5/3909 20130101; G11B 5/11 20130101; G11B 2005/3996 20130101;
B82Y 10/00 20130101 |
Class at
Publication: |
360/294 ;
360/319 |
International
Class: |
G11B 5/11 20060101
G11B005/11; G11B 21/18 20060101 G11B021/18 |
Claims
1. A magnetic read sensor, comprising: a sensor stack that includes
first and second magnetic free layers that are anti-parallel
coupled across a non-magnetic layer sandwiched there-between; a
magnetic side shield structure formed at a side of the sensor
stack; and a non-magnetic, electrically insulating layer separating
the magnetic side shield structure from the sensor stack; wherein:
the magnetic side shield structure further comprises a first and
second magnetic layers and an exchange coupling layer sandwiched
between the first and second magnetic layers; the magnetic layers
are anti-parallel coupled with one another across the exchange
coupling layer; the first magnetic layer is laterally aligned with
the first magnetic free layer of the sensor stack and provides a
magnetic bias field in a first direction parallel with an air
bearing surface; and the second magnetic layer is laterally aligned
with the second magnetic free layer of the sensor stack and
provides a magnetic bias field in a second direction that is
opposite to the first direction.
2. The magnetic read sensor as in claim 1 further comprising, a
hard bias structure located adjacent to a back edge of the sensor
stack opposite the air bearing surface, the hard bias structure
providing a magnetic bias field that is perpendicular to the air
bearing surface.
3. The magnetic read sensor as in claim 1 wherein the sensor is a
scissor type magnetic sensor.
4. The magnetic read sensor as in claim 1 wherein the exchange
coupling layer comprises a non-magnetic layer sandwiched between
first and second magnetic layers.
5. The magnetic read sensor as in claim 1 wherein the first and
second magnetic layers of the magnetic side shield structure each
comprise Ni--Fe.
6. The magnetic read sensor as in claim 1 wherein the exchange
coupling layer comprises a layer of Ru sandwiched between first and
second layers of Co--Fe.
7. The magnetic read sensor as in claim 1 wherein the exchange
coupling layer comprises a layer of Ru sandwiched between first and
second layers of Co--Fe and the first and second magnetic layers of
the magnetic side shield structure each comprise Ni--Fe.
8. The magnetic read sensor as in claim 1 further comprising a
layer of anti-ferromagnetic material that is exchange coupled with
the first magnetic layer of the magnetic side shield structure, the
exchange coupling between the layer of antiferromagnetic material
resulting in a pinning of a magnetization of the first magnetic
layer in the first direction parallel with the air bearing
surface.
9. The magnetic read sensor as in claim 1 further comprising a
layer of anti-ferromagnetic material that is exchange coupled with
the second magnetic layer of the magnetic side shield structure,
the exchange coupling between the layer of antiferromagnetic
material resulting in a pinning of a magnetization of the second
magnetic layer in the second direction.
10. The magnetic read sensor as in claim 8 wherein the layer of
antiferromagnetic material is between the first magnetic layer and
the exchange coupling layer.
11. The magnetic read sensor as in claim 8 wherein the layer of
antiferromagnetic material contacts the first magnetic layer at a
location that is opposite the exchange coupling layer.
12. The magnetic read sensor as in claim 9 wherein the layer of
antiferromagnetic material is located between the second magnetic
layer and the exchange coupling layer.
13. The magnetic read sensor as in claim 9 wherein the layer of
antiferromagnetic material contacts the second magnetic layer at a
location that is opposite the exchange coupling layer.
14. The magnetic read sensor as in claim 1 wherein the sensor stack
is sandwiched between a leading magnetic shield and a trailing
magnetic shield.
15. The magnetic read sensor as in claim 14 further comprising a
non-magnetic decoupling layer between the trailing magnetic shield
and the side shield structure, the non-magnetic decoupling layer
being sufficiently thick so as to magnetically de-couple the
trailing magnetic shield from the magnetic side shield
structure.
16. The magnetic read sensor as in claim 1 further comprising: a
trailing magnetic shield; a layer of antiferromagnetic material
that is exchange coupled with the trailing magnetic shield; and a
second exchange coupling layer located between the trailing
magnetic shield and the side shield structure and being configured
to anti-parallel couple the trailing magnetic shield with the
second magnetic layer of the magnetic side shield structure.
17. The magnetic read sensor as in claim 1 wherein at least one of
the magnetic layer of the side shield structure comprises: a layer
of NiFe having about 55 atomic percent Fe: a layer of NiFe having
about 20 atomic percent Fe; a layer of NiFe having about 19 atomic
percent Fe; a layer of NiFe having about 12.5 atomic percent Fe; a
layer of NiFe having about 4 atomic percent Fe; and a layer of
Ni--Fe--Mo having about 17 atomic percent Fe and about 5 atomic
percent Mo.
18. The magnetic read sensor as in claim 1 wherein the
non-magnetic, electrically insulating layer separating the magnetic
side shield structure from the sensor stack comprises one or more
of AlOx, MgO, SiN, TaO and SiOxNy.
19. A magnetic read head, comprising: a trailing magnetic shield; a
leading magnetic shield; a sensor stack that includes first and
second magnetic free layers that are anti-parallel coupled across a
non-magnetic layer sandwiched there-between, the sensor stack
having first and second laterally opposed sides sandwiched between
the leading magnetic shield and the trailing magnetic shield; first
and second magnetic side shield structures adjacent to and
separated from each of the first and second sides of the sensor
stack by a non-magnetic, electrically insulating layer, each of the
first and second magnetic side shield structures including a first
magnetic layer, a second magnetic layer and an exchange coupling
layer sandwiched between the first and second magnetic layer and
configured to anti-parallel couple the first and second magnetic
layers; an exchange coupling layer sandwiched between the trailing
magnetic shield and each of the first and second magnetic side
shield structures and configured to anti-parallel couple the
trailing magnetic shield with the second magnetic layer of the
magnetic side shield structure; wherein the first magnetic layer is
laterally aligned with the first magnetic free layer of the sensor
stack and provides a magnetic bias field in a first direction
parallel with an air bearing surface; and the second magnetic layer
is laterally aligned with the second magnetic free layer of the
sensor stack and provides a magnetic bias field in a second
direction that is opposite to the first direction; and a layer of
anti-ferromagnetic material, exchange coupled with the trailing
magnetic shield so as to pin a magnetization of the trailing
magnetic shield in a direction parallel with an air bearing surface
of the sensor stack.
20. The magnetic read head as in claim 19 wherein the layer of
anti-ferromagnetic material contacts the trailing magnetic shield
at a location that is opposite the magnetic side shield
structure.
21. The magnetic read head as in claim 19 wherein the exchange
coupling layer of the first and second magnetic side shield
structures and the exchange coupling layer of located between the
trailing magnetic shield and the magnetic side shield structures
each comprise a layer of Ru sandwiched between first and second
layers of Co--Fe.
22. The magnetic read head as in claim 19 wherein at least one of
the leading and trailing magnetic shields comprises: a layer of
NiFe having about 55 atomic percent Fe: a layer of NiFe having
about 20 atomic percent Fe; a layer of NiFe having about 19 atomic
percent Fe; a layer of NiFe having about 12.5 atomic percent Fe; a
layer of NiFe having about 4 atomic percent Fe; and a layer of
Ni--Fe--Mo having about 17 atomic percent Fe and about 5 atomic
percent Mo.
23. A magnetic data recording system, comprising: a housing; a
magnetic media mounted within the housing; a slider; an actuator
mounted within the housing for moving the slider adjacent to the
magnetic media; a magnetic read sensor formed on the slider, the
magnetic read sensor further comprising: a sensor stack that
includes first and second magnetic free layers that are
anti-parallel coupled across a non-magnetic layer sandwiched
there-between; a magnetic side shield structure formed at a side of
the sensor stack; and a non-magnetic, electrically insulating layer
separating the magnetic side shield structure from the sensor
stack; wherein: the magnetic side shield structure further
comprises a first and second magnetic layers and an exchange
coupling layer sandwiched between the first and second magnetic
layers; the magnetic layers are anti-parallel coupled with one
another across the exchange coupling layer; the first magnetic
layer is laterally aligned with the first magnetic free layer of
the sensor stack and provides a magnetic bias field in a first
direction parallel with an air bearing surface; and the second
magnetic layer is laterally aligned with the second magnetic free
layer of the sensor stack and provides a magnetic bias field in a
second direction that is opposite to the first direction.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to magnetic data recording and
more particularly to a scissor style magnetic read sensor with a
wrap around shield for reduced track width and reduced gap
thickness.
BACKGROUND OF THE INVENTION
[0002] The heart of a computer is an assembly that is referred to
as a magnetic disk drive. The magnetic disk drive includes a
rotating magnetic disk, write and read heads that are suspended by
a suspension arm adjacent to a surface of the rotating magnetic
disk and an actuator that swings the suspension arm to place the
read and write heads over selected circular tracks on the rotating
disk. The read and write heads are directly located on a slider
that has an air bearing surface (ABS). The suspension arm biases
the slider into contact with the surface of the disk when the disk
is not rotating, but when the disk rotates air is swirled by the
rotating disk. When the slider rides on the air bearing, the write
and read heads are employed for writing magnetic impressions to and
reading magnetic impressions from the rotating disk. The read and
write heads are connected to processing circuitry that operates
according to a computer program to implement the writing and
reading functions.
[0003] The write head includes at least one coil, a write pole and
one or more return poles. When a current flows through the coil, a
resulting magnetic field causes a magnetic flux to flow through the
write pole, which results in a magnetic write field emitting from
the tip of the write pole. This magnetic field is sufficiently
strong that it locally magnetizes a portion of the adjacent
magnetic disk, thereby recording a bit of data. The write field,
then, travels through a magnetically soft under-layer of the
magnetic medium to return to the return pole of the write head.
[0004] A magnetoresistive sensor such as a Giant Magnetoresistive
(GMR) sensor or a Tunnel Junction Magnetoresisive (TMR) sensor can
be employed to read a magnetic signal from the magnetic media. The
magnetoresistive sensor has an electrical resistance that changes
in response to an external magnetic field. This change in
electrical resistance can be detected by processing circuitry in
order to read magnetic data from the adjacent magnetic media.
[0005] As the need for data density increases there is an ever
present need to decrease the track width of the system as well as
well as the bit length. With regard to the magnetic head, this
means reducing the effective track width of the read head and
reducing the magnetic spacing of the read head. However, physical
limitations as well as manufacturing limitations have constrained
the amount by which the track width and gap thickness of the
magnetic read head can be reduced. Therefore, there remains a need
for a magnetic read head that can provide such reduced track width
and gap thickness and for a manufacturing process capable of
producing such a system. In addition, there is a need for a
magnetic sensor to be reliable and robust in a variety of operating
environments.
SUMMARY OF THE INVENTION
[0006] The present invention provides a magnetic read sensor that
includes a sensor stack having first and second magnetic free
layers that are anti-parallel coupled across a non-magnetic layer
sandwiched there-between. A magnetic side shield structure is
formed at a side of the sensor stack, a non-magnetic, electrically
insulating layer separates the magnetic side shield structure from
the sensor stack. The magnetic side shield structure further
includes first and second magnetic layers and an exchange coupling
layer sandwiched between the first and second magnetic layers. The
magnetic layers are anti-parallel coupled with one another across
the exchange coupling layer. The first magnetic layer is laterally
aligned with the first magnetic free layer of the sensor stack and
provides a magnetic bias field in a first direction parallel with
an air bearing surface, and the second magnetic layer is laterally
aligned with the second magnetic free layer of the sensor stack and
provides a magnetic bias field in a second direction that is
opposite to the first direction.
[0007] The magnetic side shield advantageously provides magnetic
side shielding that reduces the effective track-width for improved
track density and data density. In addition, the side shield
provides a magnetic biasing that biases each of the free layers of
the sensor stack in opposite directions so as to prevent flipping
of the magnetizations of the magnetic free layers. This greatly
improves the stability of the sensor.
[0008] The sensor can be a scissor type sensor with the two
magnetic free layers being anti-parallel coupled with one another,
and with a bias structure at the back edge of the sensor stack
(opposite the air bearing surface) that cants the magnetizations of
the free layer away from being anti-parallel, making them
orthogonal to one another. In the presence of a magnetic field the
relative angle of the magnetizations of the two free layers
changes, resulting in a measurable change in electrical
resistance.
[0009] These and other features and advantages of the invention
will be apparent upon reading of the following detailed description
of preferred embodiments taken in conjunction with the figures in
which like reference numerals indicate like elements
throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a fuller understanding of the nature and advantages of
this invention, as well as the preferred mode of use, reference
should be made to the following detailed description read in
conjunction with the accompanying drawings which are not to
scale.
[0011] FIG. 1 is a schematic illustration of a disk drive system in
which the invention might be embodied;
[0012] FIG. 2 is an ABS view of a slider illustrating the location
of a magnetic head thereon;
[0013] FIG. 3 is an air bearing surface view of a prior art
magnetic read sensor;
[0014] FIG. 4 is a top down, exploded, schematic view of a portion
of the read element of FIG. 3;
[0015] FIG. 5 is an air bearing surface view of a magnetic read
element according to an embodiment of the invention;
[0016] FIG. 6 is an air bearing surface view of a magnetic read
element according to another embodiment of the invention;
[0017] FIG. 7 is an air bearing surface view of a magnetic read
sensor according to yet another embodiment of the invention;
[0018] FIG. 8 is an air bearing surface view of a magnetic read
sensor according to still another embodiment of the invention;
[0019] FIG. 9 is an air bearing surface view of a magnetic read
sensor according to yet another embodiment of the invention;
[0020] FIG. 10 is an air bearing surface view of a magnetic read
sensor according to yet another embodiment of the invention;
and
[0021] FIG. 11 is a top down, exploded, schematic view of a portion
of a read sensor, illustrating magnetic biasing of a scissor type
magnetic read sensor according to an embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The following description is of the best embodiments
presently contemplated for carrying out this invention. This
description is made for the purpose of illustrating the general
principles of this invention and is not meant to limit the
inventive concepts claimed herein.
[0023] Referring now to FIG. 1, there is shown a disk drive 100
embodying this invention. As shown in FIG. 1, at least one
rotatable magnetic disk 112 is supported on a spindle 114 and
rotated by a disk drive motor 118. The magnetic recording on each
disk is in the form of annular patterns of concentric data tracks
(not shown) on the magnetic disk 112.
[0024] At least one slider 113 is positioned near the magnetic disk
112, each slider 113 supporting one or more magnetic head
assemblies 121. As the magnetic disk rotates, slider 113 moves
radially in and out over the disk surface 122 so that the magnetic
head assembly 121 can access different tracks of the magnetic disk
where desired data are written. Each slider 113 is attached to an
actuator arm 119 by way of a suspension 115. The suspension 115
provides a slight spring force which biases slider 113 against the
disk surface 122. Each actuator arm 119 is attached to an actuator
means 127. The actuator means 127 as shown in FIG. 1 may be a voice
coil motor (VCM). The VCM comprises a coil movable within a fixed
magnetic field, the direction and speed of the coil movements being
controlled by the motor current signals supplied by controller
129.
[0025] During operation of the disk storage system, the rotation of
the magnetic disk 112 generates an air bearing between the slider
113 and the disk surface 122 which exerts an upward force or lift
on the slider. The air bearing thus counter-balances the slight
spring force of suspension 115 and supports slider 113 off and
slightly above the disk surface by a small, substantially constant
spacing during normal operation.
[0026] The various components of the disk storage system are
controlled in operation by control signals generated by control
unit 129, such as access control signals and internal clock
signals. Typically, the control unit 129 comprises logic control
circuits, storage means and a microprocessor. The control unit 129
generates control signals to control various system operations such
as drive motor control signals on line 123 and head position and
seek control signals on line 128. The control signals on line 128
provide the desired current profiles to optimally move and position
slider 113 to the desired data track on disk 112. Write and read
signals are communicated to and from write and read heads 121 by
way of recording channel 125.
[0027] With reference to FIG. 2, the orientation of the magnetic
head 121 in a slider 113 can be seen in more detail. FIG. 2 is an
ABS view of the slider 113, and as can be seen the magnetic head
including an inductive write head and a read sensor, is located at
a trailing edge of the slider. The above description of a typical
magnetic disk storage system and the accompanying illustration of
FIG. 1 are for representation purposes only. It should be apparent
that disk storage systems may contain a large number of disks and
actuators, and each actuator may support a number of sliders.
[0028] FIG. 3 shows a view of a magnetic read head 300 as viewed
from the air bearing surface. The read head 300 is a scissor type
magnetoresistive sensor having a sensor stack 302 that includes
first and second free layers 304, 306 that are anti-parallel
coupled across a non-magnetic layer 308 that can be a non-magnetic,
electrically insulating barrier layer such as MgOx or an
electrically insulating spacer layer such as AgSn. A capping layer
structure 310 can be provided at the top of the sensor stack 302 to
protect the layers of the sensor stack. The sensor stack 302 can
also include a seed layer structure 312 at its bottom to promote a
desired grain growth in the above formed layers.
[0029] The first and second magnetic layers 304, 306 can be
constructed of multiple layers of magnetic material. For example,
the first magnetic layer 304 can be constructed of: a layer of
Ni--Fe; a layer of Co--Hf deposited over the layer of Ni--Fe; a
layer of Co--Fe--B deposited over the layer of Co--Hf; and a layer
of Co--Fe deposited over the layer of Co--Fe--B. The second
magnetic layer 306 can be constructed of: a layer of Co--Fe; a
layer of Co--Fe--B deposited over the layer of Co--Fe; a layer of
Co--Hf deposited over the layer of Co--Fe--B; and a layer of Ni--Fe
deposited over the layer of Co--Hf. The capping layer structure 310
can also be constructed as a multi-layer structure and can include
first and second layers of Ru with a layer of Ta sandwiched
there-between. The seed layer structure 312 can include a layer of
Ta and a layer of Ru formed over the layer of Ta.
[0030] The sensor stack 302 is sandwiched between leading and
trailing magnetic shields 314, 316, each of which can be
constructed of a magnetic material such as Ni--Fe, of a composition
having a high magnetic saturation constant (high Bsat) to provide
effective magnetic shielding. In addition, the structure 300
includes first and second magnetic side shields 318, 320 which are
also constructed of a soft magnetic material such as Ni--Fe, and
which can be constructed to have a high or low Bsat. The side
shields 318 and 320 are separated from the sensor stack 302 by
non-magnetic, electrically insulation layers 322, 324 which can be
a material such as alumina. The insulation layers 322, 324 prevent
electrical sense current from being shunted through the side
shields 318, 320.
[0031] It can be seen that the side shields, 318, 320 are
functionally magnetically connected with the trailing shield 316 so
that together the side shields 318, 320 and trailing shield 316
form a wrap-around magnetic shield. The presence of the side
shields improves track-width definition and helps to reduce the
track-width of the sensor 300.
[0032] FIG. 4 shows an exploded, top-down view of the magnetic
layers 304, 306 with the non-magnetic layer 308 there-between. The
presence of the non-magnetic layer 308 between the first and second
magnetic layers 304, 306 causes the magnetic layers 304, 306 to be
magnetically anti-parallel coupled with one another. In addition, a
hard magnetic bias structure 402 is provided at the back edge of
the sensor layers (not shown in FIG. 3). The hard bias layer 402
has a magnetization perpendicular to the air bearing surface ABS,
which is represented by arrow 404. The magnetic layers 304, 306
have a magnetic anisotropy that is parallel with the ABS, so that
in the absence of a magnetic field 404 from the hard bias layer
402, the magnetizations of the layers 304, 306 would be oriented
anti-parallel to one another in directions that are parallel with
the ABS. However, the presence of the a bias field from the
magnetization 404 of the bias layer 402 cants the magnetizations of
the magnetic layers 304, 306 to a direction that is not parallel
with the ABS. The direction of magnetizations of the magnetic
layers 304, 306 are represented by arrows 406, 408, with the arrow
406 representing the direction of magnetization of the layer 304
and the arrow 408 representing the direction of magnetization of
the layer 308. However, the magnetizations 406, 408, can move
relative to one another in response to a magnetic field, such as
from a magnetic media. This change in the directions of
magnetizations 406, 408 relative to one another changes the
electrical resistance across the barrier layer 308, and this change
in resistance can be detected as a signal for reading magnetic data
from a media such as the media 112 of FIG. 1.
[0033] In the above described example, the presence of the side
magnetic shields 318, 320 (shown in FIG. 3) improves the reduction
of and definition of the track width of the sensor. However, with
reference again to FIG. 4, with this embodiment it is possible that
the directions of the magnetizations 406, 408 can flip. This would
result in the magnetic sensor being inoperable.
[0034] FIG. 5 shows an air bearing surface view of a magnetic
sensor according to an embodiment of the invention. A read element
500 includes a sensor stack 502 that is sandwiched between a lower
or leading shield 504 and an upper or trailing shield 506. As with
the previously described embodiment, the sensor stack 502 can
include first and second free layers 508, 510 and a non-magnetic
layer 512 sandwiched there-between that can be an electrically
insulating barrier layer such as MgO or can be an electrically
conductive spacer layer such as AgSn. A seed layer 514 can be
provided at the bottom of the sensor stack 502 to promote a desired
grain growth in the above layers of the sensor stack 502. A capping
layer 516 can be provided at the top of the sensor stack 502.
[0035] The read head 500 includes anti-parallel coupled magnetic
side shields 518, 520 that include first and second soft magnetic
layers 522, 524 that are anti-parallel coupled across an
anti-parallel exchange coupling layer 526. The soft magnetic layers
522, 524 can be constructed of a material such as Ni--Fe that has
soft magnetic properties with low magnetic coercivity. The magnetic
layers 522, 524 can each have saturation magnetizations (Bsat) that
are the same as one another or different from one another and that
can be high or low. The magnetic side shield structures 518, 520
are separated from the sensor stack 502 and from the bottom shield
504 by a layer of non-magnetic, electrically insulating material
528, which can be one or more of AlOx, MgO, SiN, TaOx or
SiOxNy.
[0036] The upper or trailing magnetic shield 506 can be constructed
of a soft magnetic material such as Ni--Fe. Because the trailing
shield 506 is constructed of a soft magnetic material having a low
coercivity such as Ni--Fe, it can function well as a magnetic
shield. The trailing magnetic shield 506 is separated from the
sensor stack 502 and from the side shields 518, 520 by a layer of
non-magnetic material such as Ru 534 that is sufficiently thick
that it breaks the exchange coupling between the trailing shield
506 and the magnetic layers 524.
[0037] The anti-parallel exchange coupling layer 526 is a
multi-layer structure that includes a layer of Ru 527 sandwiched
between first and second layers of CoFe 529, 531. The anti-parallel
exchange coupling layer structure 526 is exchange coupled with the
adjacent magnetic layers 522, 524 and sets the magnetizations of
these layers anti-parallel to one another as indicated by arrows
533, 535.
[0038] One or both of the magnetic layers 522, 524 can be
constructed of multiple magnetic layers. Preferably these layers
include: a layer of Ni--Fe having about 55 atomic percent Fe; a
layer of Ni--Fe having about 20 atomic percent Fe; a layer of
Ni--Fe having about 19 atomic percent Fe; a layer of Ni--Fe having
about 12.5 atomic percent Fe; a layer of Ni--Fe having about 4
atomic percent Fe and a layer of Ni--Fe--Mo having about 17 atomic
percent Fe and about 5 atomic percent Mo. In addition, one or more
of the leading and trailing shields 504, 506 can be constructed of
these materials. Use of this combination of materials provides
improved magnetic stability.
[0039] With reference now to FIG. 6, a read sensor 600 according to
another embodiment of the invention is described. Like the
previously described embodiments, the read sensor 600 includes a
sensor stack 602 that is sandwiched between first and second
magnetic shields 604, 606. The first shield 604 is a bottom or
leading shield, and the second shield 606 is an upper or trailing
shield. Both the first and second shields 604, 606 can be
constructed of a low magnetic coercivity, soft magnetic material
such as NiFe. The sensor stack 602 can include first and second
free magnetic layers 608, 610 with a non-magnetic antiparallel
coupling layer such as Ru 612 sandwiched there-between. The sensor
stack 602 can also include a seed layer 614 and a capping layer
616.
[0040] The second or trailing shield 606 is exchange coupled with
an exchange coupling layer structure 618 that can include a layer
of antiferromagnetic material such s Ir--Mn 620 sandwiched between
first and second magnetic layers 622, 624 that are preferably
Co--Fe. The exchange coupling layer structure 618 is exchange
coupled with the trailing magnetic shield 606 and sets the
magnetization of the magnetic layer in a direction parallel with
the air bearing surface as indicated by arrow 626.
[0041] The read element 600 includes magnetic side shield
structures 622, 624 that are separated from the sensor stack 602
and from the leading shield 604 by a layer of non-magnetic,
electrically insulating material 626. The trailing magnetic shield
606 is separated from the side shields 622, 624 (and from the
sensor stack 602) by a non-magnetic anti-parallel exchange coupling
layer 628. The anti-parallel exchange coupling layer 626 can be
constructed as a layer of Ru 628 sandwiched between first and
second magnetic layers 630, 632, which are preferably Co--Fe.
[0042] Each of the side shield structures 622, 624 can include
first and second magnetic layers 634, 636. The magnetic layers 634,
636 are anti-parallel coupled across another anti-parallel exchange
coupling layer 638. The anti-parallel exchange coupling layer 638
can be constructed of a layer of Ru 640 sandwiched between first
and second magnetic layers 642, 644 which are preferably
Co--Fe.
[0043] The anti-parallel exchange coupling structure 626 sets the
magnetization of the upper magnetic layer 636 in a direction that
is opposite (e.g. anti-parallel with) the magnetization direction
626 of the trailing shield 606, as indicated by arrows 646. The
anti-parallel exchange coupling layer 638 sets the magnetization of
the lower magnetic layer 634 in a direction that is opposite to
(anti-parallel to) the magnetization 646 of the upper magnetic
layer 634 as indicated by arrow 648.
[0044] The magnetizations of the magnetic free layers 608, 610 are
similar to that described above with reference to FIG. 4. Magnetic
bias fields from the layers 634, 636 stabilize the magnetizations
of the sensor layers 608, 610 in order to prevent flipping of the
magnetization of these layers, thereby stabilizing the sensor 600
and making it more reliable.
[0045] With reference now to FIG. 7, another embodiment of the
invention includes a magnetic read element 700 having a sensor
stack 702 that is sandwiched between a leading magnetic shield 704
and a trailing magnetic shield 706. The sensor stack 702 includes
first and second magnetic free layers 708, 710 that are
anti-parallel coupled across a non-magnetic anti-parallel coupling
layer such as alumina 712. The sensor stack can also include a seed
layer structure 714 and a capping layer structure 716.
[0046] Side shield structures 718, 720 are provided at the sides of
the sensor stack 702 and are separated from the sensor stack 702
and from the leading magnetic shield 704 by non-magnetic,
electrically insulating insulation layers 722. Like the previously
described embodiment, each of the side shield structures 718, 720
includes first and second magnetic layers 724, 726 that are
anti-parallel coupled across an anti-parallel exchange coupling
layer 728. The magnetic layers 724, 726 can be constructed of
materials that have the same magnetic saturation (Bsat) as one
another, or can be constructed of materials having different Bsat
values. The anti-parallel exchange coupling layer 728 can be
constructed of a layer of Ru 730 sandwiched between first and
second magnetic layers 732, 734 that are preferably Co--Fe. The
anti-parallel exchange coupling layer 728 is preferably of such as
thickness as to anti-parallel couple the first and second magnetic
layers 724, 726.
[0047] The upper or trailing-most magnetic layer 726 contacts and
is exchange coupled with a layer of anti-ferromagnetic material
736, which is preferably Ir--Mn. The antiferromagnetic layer 736 in
this embodiment is located at the top or trailing most edge of the
magnetic layer 726, between the magnetic layer 726 and the trailing
magnetic shield 706. The exchange coupling between the
antiferromagnetic layer 736 and the magnetic layer 726 pins the
magnetization of the magnetic layer 726 in a first direction
parallel with the air bearing surface. The anti-parallel coupling
between the magnetic layer 726 and magnetic layer 724 pins the
magnetization of the magnetic layer 724 in a second direction that
is also parallel with the ABS and which is opposite (anti-parallel)
with the direction of magnetization of the layer 726.
[0048] A decoupling layer 737 separates the trailing magnetic
shield from the anti-ferromagnetic layer side shields structures
718, 710 and sensor stack 702. The decoupling layer 737 is located
at the leading most edge of the trailing magnetic shield 706. The
decoupling layer 737 can be constructed of Ru and is sufficiently
thick so as to magnetically decouple the trailing magnetic shield
706 from the antiferromagnetic layers 736 and side shield
structures 718, 720.
[0049] With reference now to FIG. 8, another embodiment of the
invention provides a magnetic element 800 that includes a sensor
stack 802 that is sandwiched between leading and trailing magnetic
shields 804, 806. The sensor stack 802 includes first and second
magnetic free layers 808, 810 that are separated by and
anti-parallel coupled across a non-magnetic barrier layer 812. A
seed layer 814 may be provided at the bottom of the sensor stack
802 and a capping layer 816 may be provided at the top of the
sensor stack.
[0050] The read element includes first and second magnetic side
shield structures 818, 820 formed at either side of the sensor
stack 802. The side magnetic shield structures a 818, 820 are
separated from the sensor stack 802 and from the leading shield 804
by non-magnetic, electrically insulating layers 822.
[0051] Each of the side shield structures can include first and
second magnetic layers 824, 826. As with the previously described
embodiments, the side shield structure includes an anti-parallel
exchange coupling layer 828 that includes a layer of Ru 830
sandwiched between first and second magnetic layers 832, 834 that
are preferably Co--Fe.
[0052] In this embodiment, a layer of anti-ferromagnetic material
836 is located at the bottom of the upper magnetic layer 826,
between the exchange coupling layer 828 and the magnetic layer 826.
This layer of anti-ferromagnetic material is preferably Ir--Mn and
is exchange coupled with the upper or trailing-most magnetic layer
826 so that it pins the magnetization of the magnetic layer 826 in
a first direction that is parallel with the air bearing surface.
Anti-parallel coupling between the magnetic layer 826 and the
magnetic layer 824 causes the magnetization of the lower magnetic
layer 824 to be oriented in a second direction that is parallel
with the air bearing surface and anti-parallel with the first
direction (e.g. anti-parallel with the direction of magnetization
of the magnetic layer 826).
[0053] With continued reference to FIG. 8, a decoupling layer 838
can be provided between the trailing magnetic shield 806 and the
side shield structures 818, 820 and sensor stack 802. This
decoupling layer 838 is a constructed of a non-magnetic material
such as Ru and is sufficiently thick to magnetically decouple (e.g.
break the exchange coupling between) the tailing magnetic shield
806 and the magnetic layer 826.
[0054] With reference now to FIG. 9, still another embodiment of
the invention is described. FIG. 9 shows a magnetic read element
900 having a sensor stack 902 that is sandwiched between a leading
magnetic shield 904 and a trailing magnetic shield 906. The sensor
stack 900 includes first and second magnetic layers 908, 910 and a
non-magnetic barrier layer 912 sandwiched there-between. A seed
layer 914 may be provided at the bottom of the sensor stack 902 and
a capping layer 916 may be provided at the top of the sensor
stack.
[0055] The read element 900 also includes magnetic side shields
918, 920 at either side of the sensor stack 902 that are separated
from the sensor stack 902 and from the leading magnetic shield 904
by non-magnetic, electrically insulating layers 922. A non-magnetic
de-coupling layer 924 is provided at the bottom of the trailing
shield 906, separating the trailing shield 906 from the side
shields 918, 920 and sensor stack 902. The de-coupling layer 924
can be constructed of Ru and is sufficiently thick to break
exchange coupling between the trailing shield 906 and side shield
structures 918, 920.
[0056] With continued reference to FIG. 9, the magnetic side
shields include first and second magnetic layers 926, 928, and an
anti-parallel exchange coupling layer 930 located between the
magnetic layers 926, 928. As with the previously described
embodiments, the exchange coupling layer can include a layer of Ru
932 sandwiched between first and second magnetic layers such as
CoFe 934, 936.
[0057] In addition, a layer of antiferromagnetic material 938 is
located between the antiparallel exchange coupling layer 930 and
the bottom magnetic layer 926. The layer of antiferromagnetic
material 938 is preferably IrMn and is exchange coupled with the
lower magnetic layer 926 so as to pin the magnetization of the
lower magnetic layer 926 in a first direction parallel with the air
bearing surface. Anti-parallel coupling between the magnetic layers
926, 928 orients the magnetization of the upper magnetic layer 928
in a second direction that is anti-parallel to the first
direction.
[0058] FIG. 10 shows an air bearing surface view of another
embodiment of the invention. FIG. 10 shows a magnetic read element
1000 that is similar to the sensor 900 described above with
reference to FIG. 9. However, the read element 1000 has a layer of
antiferromagnetic material 938 that is located at the bottom of the
first magnetic layer 926 rather than at the top. The layer of
antiferromagnetic material 938 is located between the first
magnetic layer 926 and the insulation layer and leading shield 922,
904. As with the previously described embodiment, the layer 938
contacts and is exchange coupled with the first magnetic layer 926,
and this exchange coupling pins the magnetization of the layer 926
in first direction parallel with the air bearing surface.
Anti-parallel coupling between the first and second magnetic layers
926, 928 orients the magnetization of the second magnetic layer 928
in a second direction that is opposite to the first direction and
which is also parallel with the air bearing surface.
[0059] With reference now to FIG. 11, the effects of the bias
structures on the magnetic free layers of the various previously
discussed embodiments can more clearly understood. The top down
exploded view shown in FIG. 101will be discussed with reference to
the structure described above with regard to FIG. 5. However, the
magnetic biasing and stabilization describe in FIG. 11 applies to
any of the structures described with regard to any of the FIGS.
6-10 as well.
[0060] FIG. 11 shows a top down, exploded, schematic view of the
magnetic layers 508, 510 and barrier layer 512 described above with
reference to FIG. 5. The edge denoted "ABS" indicates the location
and orientation of the air bearing surface. A back edge hard bias
structure 1102 (which was not shown in FIG. 5) is located at the
back or stripe height edge of the layer (opposite the air bearing
surface) and would be separated from the layers 508, 510, 512 by a
non-magnetic, electrically insulating layer (not shown) in a manner
similar to that by which the side shields 518, 520 are in FIG.
5.
[0061] The back edge hard bias structure 1102 has a magnetization
that is oriented perpendicular to the air bearing surface as
indicated by arrow 1104. The anti-parallel coupling of the layers
508, 510 across the barrier layer 512, as well as magnetic
anisotropy of the layers 508, 510 would tend to align the
magnetizations of the layers 508, 510 in opposite directions that
are parallel with the air bearing surface. However, the
magnetization 1104 of the hard bias structure 1102 results in a
magnetic bias field oriented perpendicular to the air bearing
surface that cants the magnetizations of the layers 508, 510 away
from being parallel with the air bearing surface. These
magnetizations of the layers 508, 510 are represented by arrows
1106, 1108, with arrow 1106 being the magnetization of the layer
508 and arrow 1108 representing the magnetization of the layer 510.
The Arrow 1106 is shown in dashed line to indicate that layer 508
is located beneath layers 510, 512 in FIG. 10.
[0062] As discussed above with reference to FIGS. 3 and 4, should
the magnetizations flip direction, (e.g 1108 pointed to the left
and 1106 pointed to the right) the sensor would become inoperable.
This would be possible, because the magnetic anisotropy of the
layers 508, 510 and back edge biasing from the magnetization 1104
of the back edge bias structure 1102 do not have provide a
preference for a particular orientation of the layers 1106, 1108
either to the right or to the left.
[0063] However, side magnetic bias fields from the magnetic layers
522, 524 do prevent this flipping by providing side magnetic bias
fields for each of the magnetic layers 508, 510. With reference to
both FIGS. 5 and 10, it can be seen that the magnetic layer 522 has
a magnetization 535 that is oriented in a first direction that is
parallel with the ABS and that the magnetic layer 524 has a
magnetization that is oriented in a second anti-parallel direction.
It can also be seen that the magnetic layer 522 is aligned with the
first magnetic layer 508 whereas the magnetic layer 524 is aligned
with the second magnetic layer 510.
[0064] In FIG. 11, the magnetization 1106 of the magnetic layer 508
points to the left and the magnetization 1108 of the magnetic layer
510 points to the left. The bias layer 522 generates a magnetic
bias field that pulls the magnetization 1106 further to the left,
to stabilize the magnetization 1106 of the magnetic layer 508.
Similarly, the magnetic bias layer 524 generates a magnetic bias
field that pulls the magnetization 1108 further to the right to
bias the magnetization 1108. This biasing from the layers 522, 524
ensures that the magnetization 1106, 1108 of the magnetic layers
508, 510 cannot possibly flip directions. Therefore, the biasing
from the magnetic layers 522, 524 greatly improves the reliability
of the sensor. It should be pointed out again that, while this
discussion of the magnetic side biasing provided by the present
invention has been discussed with reference to the embodiment of
FIG. 5, this biasing applies to all of the embodiments including
those described above with reference to FIGS. 6-9.
[0065] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only and not limitation. Other embodiments falling within
the scope of the invention may also become apparent to those
skilled in the art. Thus, the breadth and scope of the invention
should not be limited by any of the above-described exemplary
embodiments, but should be defined only in accordance with the
following claims and their equivalents.
* * * * *