U.S. patent application number 16/293142 was filed with the patent office on 2020-09-10 for read head including semiconductor spacer and long spin diffusion length nonmagnetic conductive material and method of making the.
The applicant listed for this patent is SANDISK TECHNOLOGIES LLC. Invention is credited to Zhitao DIAO, Christian KAISER, Yuankai ZHENG.
Application Number | 20200286508 16/293142 |
Document ID | / |
Family ID | 1000005047093 |
Filed Date | 2020-09-10 |
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United States Patent
Application |
20200286508 |
Kind Code |
A1 |
ZHENG; Yuankai ; et
al. |
September 10, 2020 |
READ HEAD INCLUDING SEMICONDUCTOR SPACER AND LONG SPIN DIFFUSION
LENGTH NONMAGNETIC CONDUCTIVE MATERIAL AND METHOD OF MAKING
THEREOF
Abstract
A read head includes a first ferromagnetic layer, a second
ferromagnetic layer, a first diffusion-assist nonmagnetic metallic
layer located between the first ferromagnetic layer and the second
ferromagnetic layer, a second diffusion-assist nonmagnetic metallic
layer located between the first ferromagnetic layer and the second
ferromagnetic layer, and a semiconductor spacer layer located
between the first diffusion-assist nonmagnetic metallic layer and
the second diffusion-assist nonmagnetic metallic layer.
Inventors: |
ZHENG; Yuankai; (Fremont,
CA) ; KAISER; Christian; (San Jose, CA) ;
DIAO; Zhitao; (Fremont, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SANDISK TECHNOLOGIES LLC |
Addison |
TX |
US |
|
|
Family ID: |
1000005047093 |
Appl. No.: |
16/293142 |
Filed: |
March 5, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 5/02 20130101; G11B
5/187 20130101; G11B 5/70605 20130101 |
International
Class: |
G11B 5/187 20060101
G11B005/187; G11B 5/706 20060101 G11B005/706 |
Claims
1. A read head, comprising: a first ferromagnetic layer; a second
ferromagnetic layer; a first diffusion-assist nonmagnetic metallic
layer located between the first ferromagnetic layer and the second
ferromagnetic layer; a second diffusion-assist nonmagnetic metallic
layer located between the first ferromagnetic layer and the second
ferromagnetic layer; and a semiconductor spacer layer located
between the first diffusion-assist nonmagnetic metallic layer and
the second diffusion-assist nonmagnetic metallic layer; wherein
each of the first diffusion-assist nonmagnetic metallic layer and
the second diffusion-assist nonmagnetic metallic layer comprises a
metal selected from Ag, Au, Cu, or Ti; and wherein the
semiconductor spacer layer comprises a material selected from
copper-indium-gallium-selenide, copper-indium-selenide or
copper-gallium-selenide.
2. The read head of claim 1, wherein the semiconductor spacer layer
directly contacts both the first diffusion-assist nonmagnetic
metallic layer and the second diffusion-assist nonmagnetic metallic
layer.
3. The read head of claim 1, wherein: the first ferromagnetic layer
directly contacts the first diffusion-assist nonmagnetic metallic
layer; and the second ferromagnetic layer directly contacts the
second diffusion-assist nonmagnetic metallic layer.
4-5. (canceled)
6. The read head of claim 1, wherein at least one of the first
ferromagnetic layer and the second ferromagnetic layer comprises a
ferromagnetic Heusler alloy layer.
7. The read head of claim 6, wherein the first ferromagnetic layer
and the second ferromagnetic layer comprises a Co.sub.2FeAl alloy
or a Co.sub.2MnGe alloy.
8. The read head of claim 1, wherein each of the first
diffusion-assist nonmagnetic metallic layer and the second
diffusion-assist nonmagnetic metallic layer has a thickness in a
range from 1 monolayer of the metal to 3 monolayers of the
metal.
9. The read head of claim 8, wherein the semiconductor spacer layer
has a thickness in a range from 1 nm to 3 nm.
10. The read head of claim 9, wherein each of the first
ferromagnetic layer and the second ferromagnetic layer has a
thickness in a range from 0.8 nm to 3 nm.
11-12. (canceled)
13. The read head of claim 1, wherein: the first ferromagnetic
layer is a first free layer having a first magnetization having at
least two preferred magnetization directions; and the second
ferromagnetic layer is a second free layer having a second
magnetization having at least two preferred magnetization
directions.
14. The head of claim 1, further comprising a synthetic
antiferromagnetic stack, wherein one of the first and the second
ferromagnetic layers comprises a free layer and the other one of
the first and the second ferromagnetic layers comprises a pinned
reference layer.
15. The head of claim 1, further comprising a first magnetic shield
and a second magnetic shield, wherein a sensor layer stack
comprising the first ferromagnetic layer, the second ferromagnetic
layer, the first diffusion-assist nonmagnetic metallic layer, the
second diffusion-assist nonmagnetic metallic layer and the
semiconductor spacer layer is located between the first magnetic
shield and the second magnetic shield.
16. A hard disk drive, comprising: a magnetic head containing the
read head of claim 1; a slider supporting the magnetic head; an
actuator arm supporting the slider; and a motor configured to
control the actuator arm.
17-20. (canceled)
21. A read head, comprising: a first ferromagnetic layer; a second
ferromagnetic layer; a first diffusion-assist nonmagnetic metallic
layer located between the first ferromagnetic layer and the second
ferromagnetic layer; a second diffusion-assist nonmagnetic metallic
layer located between the first ferromagnetic layer and the second
ferromagnetic layer; and a semiconductor spacer layer located
between the first diffusion-assist nonmagnetic metallic layer and
the second diffusion-assist nonmagnetic metallic layer; wherein at
least one of the first ferromagnetic layer and the second
ferromagnetic layer comprises a layer stack comprising a negative
magnetostriction material layer, an amorphous nonmagnetic material
layer, an amorphous magnetic material layer and a Heusler alloy
magnetic material layer.
22. The read head of claim 21, wherein: the negative
magnetostriction material layer comprises a NiFe5% alloy; the
amorphous nonmagnetic material layer comprises amorphous tantalum
which directly contacts the negative magnetostriction material
layer; the amorphous magnetic material layer comprises an amorphous
CoFeB alloy which directly contacts the amorphous nonmagnetic
material layer; and the Heusler alloy magnetic material layer
comprises a Co.sub.2FeAl alloy or a Co.sub.2MnGe alloy which
directly contacts the amorphous magnetic material layer.
Description
FIELD
[0001] The present disclosure relates generally to the field of
hard disk drives, and particularly to a read head with a
semiconductor spacer layer and methods of manufacturing the
same.
BACKGROUND
[0002] Magnetic heads are employed to operate hard disk drives. A
magnetic head can include a reading (i.e., read) head and a
recording (i.e., writing or write) head. General structures and
method of manufacture for prior art magnetic heads are disclosed,
for example, in U.S. Patent Application Publication Nos.
2004/0097173 A1; 2007/0230063 A1; 2011/0294398 A1; and 2015/0260757
A1 and U.S. Pat. Nos. 8,291,743 B1; 8,361,541 B1; 8,443,510 B1;
8,717,709 B1; 8,735,565 B2; 8,964,333 B1; 9,153,261 B1; 9,321,146
B2; and 9,390,733 B2 the entire contents of which are incorporated
herein.
SUMMARY
[0003] According to an aspect of the present disclosure, a read
head includes a first ferromagnetic layer, a second ferromagnetic
layer, a first diffusion-assist nonmagnetic metallic layer located
between the first ferromagnetic layer and the second ferromagnetic
layer, a second diffusion-assist nonmagnetic metallic layer located
between the first ferromagnetic layer and the second ferromagnetic
layer, and a semiconductor spacer layer located between the first
diffusion-assist nonmagnetic metallic layer and the second
diffusion-assist nonmagnetic metallic layer.
[0004] According to another aspect of the present disclosure, a
method of forming read head is provided, which comprises: forming a
first magnetic shield over a substrate; forming a sensor layer
stack including, in order, a first ferromagnetic layer, a first
diffusion-assist nonmagnetic metallic layer, a semiconductor spacer
layer, a second diffusion-assist nonmagnetic metallic layer, and a
second ferromagnetic layer; forming a read sensor stripe by
patterning the sensor layer stack; and forming a second magnetic
shield over the read sensor stripe.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a top schematic view of a disk drive including a
slider including read head of an embodiment of the present
disclosure.
[0006] FIG. 2 is a side schematic view of the disk drive of FIG.
1.
[0007] FIG. 3 is an in-track vertical cross-sectional view of an
exemplary magnetic head incorporating the read head of the present
disclosure.
[0008] FIG. 4A illustrates a top-down view of an exemplary
structure for forming a magnetic head after formation of a sensor
layer stack according to an embodiment of the present
disclosure.
[0009] FIG. 4B is a vertical cross-sectional view of a sensor
region of the exemplary structure along the plane B-B' of FIG.
4A.
[0010] FIG. 5A illustrates a top-down view of the exemplary
structure after formation of a read sensor stripe by patterning the
sensor layer stack according to an embodiment of the present
disclosure.
[0011] FIG. 5B is a vertical cross-sectional view of the sensor
region of the exemplary structure along the plane B-B' of FIG.
5A.
[0012] FIG. 6A illustrates a top-down view of the exemplary
structure after formation of an electrical isolation dielectric
layer, a nonmagnetic spacer material layer, and a pair of
nonmagnetic spacers according to an embodiment of the present
disclosure.
[0013] FIG. 6B is a vertical cross-sectional view of the sensor
region of the exemplary structure along the plane B-B' of FIG.
6A.
[0014] FIG. 7A illustrates a top-down view of the exemplary
structure after formation of a pair of side shields according to an
embodiment of the present disclosure.
[0015] FIG. 7B is a vertical cross-sectional view of the sensor
region of the exemplary structure along the plane B-B' of FIG.
7A.
[0016] FIG. 8A illustrates a top-down view of the exemplary
structure after application and patterning a sensor backside edge,
after deposition of a dielectric fill material layer and a second
magnetic shield according to an embodiment of the present
disclosure.
[0017] FIG. 8B is a vertical cross-sectional view of the sensor
region of the exemplary structure along the plane B-B' of FIG.
8A.
[0018] FIG. 8C is a vertical cross-sectional view of the sensor
region of the exemplary structure along the plane C-C' of FIG.
8A.
[0019] FIG. 9A illustrates a top-down view of the exemplary
structure after performing a lapping process to form an air bearing
surface according to an embodiment of the present disclosure.
[0020] FIG. 9B is a vertical cross-sectional view of the sensor
region of the exemplary structure along the plane B-B' of FIG.
9A.
[0021] FIG. 9C is a vertical cross-sectional view of the sensor
region of the exemplary structure along the plane C-C' of FIG.
9A.
[0022] FIG. 10 is a magnified vertical cross-sectional view of a
first exemplary sensor layer stack according to an embodiment of
the present disclosure.
[0023] FIG. 11 is a magnified vertical cross-sectional view of a
second exemplary sensor layer stack according to an embodiment of
the present disclosure.
[0024] FIG. 12 is a magnified vertical cross-sectional view of a
third exemplary sensor layer stack according to an embodiment of
the present disclosure.
[0025] FIG. 13 is a graph of a magnetoresistance for various sensor
layer stacks as a function of a resistance-area (RA) product
according to embodiments of the present disclosure.
[0026] FIG. 14 is an R-H graph of a resistance of a sensor layer
stack of an embodiment of the present disclosure as a function of
an external magnetic field.
DETAILED DESCRIPTION
[0027] As described above, the present disclosure is directed to a
read head including a semiconductor spacer and long spin diffusion
length nonmagnetic conductive interlayers, (e.g., charge carrier
diffusion-assist interlayers) located between two ferromagnetic
layers and methods of manufacturing the same, the various aspects
of which are described below in detail. The charge carrier
diffusion-assist interlayers include nonmagnetic metal layers, such
as Cu, Ag, Au or Ti that have a relatively long electron diffusion
length.
[0028] The drawings are not drawn to scale. Multiple instances of
an element may be duplicated where a single instance of the element
is illustrated, unless absence of duplication of elements is
expressly described or clearly indicated otherwise. Ordinals such
as "first," "second," and "third" are employed merely to identify
similar elements, and different ordinals may be employed across the
specification and the claims of the instant disclosure. The same
reference numerals refer to the same element or similar element.
Unless otherwise indicated, elements having the same reference
numerals are presumed to have the same composition. As used herein,
a first element located "on" a second element can be located on the
exterior side of a surface of the second element or on the interior
side of the second element. As used herein, a first element is
located "directly on" a second element if there exist a physical
contact between a surface of the first element and a surface of the
second element.
[0029] As used herein, a "layer" refers to a material portion
including a region having a thickness. A layer may extend over the
entirety of an underlying or overlying structure, or may have an
extent less than the extent of an underlying or overlying
structure. Further, a layer may be a region of a homogeneous or
inhomogeneous continuous structure that has a thickness less than
the thickness of the continuous structure. For example, a layer may
be located between any pair of horizontal planes between, or at, a
top surface and a bottom surface of the continuous structure. A
layer may extend horizontally, vertically, and/or along a tapered
surface. A substrate may be a layer, may include one or more layers
therein, or may have one or more layer thereupon, thereabove,
and/or therebelow.
[0030] FIG. 1 is a top schematic view of a hard disk drive 300
including a slider 308 with a read head of an embodiment of the
present disclosure. FIG. 2 is a side schematic view of the slider
308 of FIG. 1 and illustrates the magnetic head 600 of the
embodiments of the present disclosure. The disk drive 300 may
include one or more of the disks/media 302 configured to store
data. The disks/media 302 reside on a spindle assembly 304 that is
mounted to a drive housing 306. Data may be stored along tracks 307
in the magnetic recording layer of disk 302. The reading and
writing of data is accomplished with the magnetic head 600 that
incorporates both the read head (i.e., a reader) 610 and a
recording head 660 (i.e., a writer or a writing head). The slider
308 is part of a head-gimbal assembly (HGA) supported by one end of
an actuator arm 309. The opposite end of the actuator arm 309 is
connected to a head stack assembly (HSA) which may include a
carriage and a voice coil motor 311. The recording head 660 is used
to alter the properties of the magnetic recording layer of disk 302
and thereby write information thereto. The read head 610 is used to
read information stored on the magnetic recording layer of the disk
302.
[0031] The read head 610 and the recording head 660 are disposed
along an air bearing surface ABS of the slider 308. The ABS is the
bottom surface of the slider 308, which is the slider surface that
is the most proximate to the media 302. The separation distance
between the ABS and the media 302 is self-limiting through the air
flow between the ABS and the read head 610 and/or the writing head
660. In operation, a spindle motor (not shown) rotates the spindle
assembly 304, and thereby rotates the disk 302 to position the
magnetic head 600 containing the read head 610 and the writing head
660 at a particular location along a desired disk track 307. The
position of the read head 610 and/or the recording head 660
relative to disk 302 may be controlled by a position control
circuitry 310 which controls the HSA to move the actuator arm
309.
[0032] Referring to FIG. 3, an in-track vertical cross-sectional
view of an exemplary magnetic head 600 of an embodiment the present
disclosure is illustrated. The magnetic head 600 is positioned over
a recording track 307 on a disc media 302. The magnetic head 600
comprises, from the leading side of the head, a read head 610 and a
recording (i.e., writing) head 660. The reading head comprises a
lower reading shield 102, a read sensor 650 (i.e., a reading
element), and an upper reading shield 104. The read sensor 650 can
include a sensor layer stack 110 (e.g., magneto-resistive (MR)
device) of the embodiments of the present disclosure, such as a
giant magneto-resistive (GMR) stack (also referred to as a current
perpendicular to plane (CPP) spin valve or CPP-GMR spin valve). The
recording head 660 can comprise an optional auxiliary pole 402, a
magnetic coil 425 that is wound around a main pole 420, a record
element 450, and a trailing shield 480 which may be integrated with
an upper pole 482. The record element 450 is formed between the
main pole 420 and the trailing shield 480. An insulating material
portion 470 is provided around the magnetic coil 425 between the
main pole 420 and the trailing shield 480.
[0033] Referring to FIGS. 4A and 4B, an exemplary structure for
forming a read head of the embodiments of the present disclosure is
illustrated. The exemplary structure includes a substrate 101,
which can be, for example, an aluminum titanium carbide substrate.
A first magnetic shield 102 is formed within a sensor region of the
exemplary structure. The first magnetic shield 102 includes a soft
magnetic material, and may have a thickness in a range from 200 nm
to 2,000 nm, although lesser and great thicknesses can also be
employed. The first magnetic shield 102 can be subsequently
patterned to provide the lower reading shield 102 of a magnetic
head 600 in a finished product. In one embodiment, the first
magnetic shield 102 can comprise, or consist essentially of, NiFe,
NiCo, CoFe, NiFeCo, CoB, CoFeB, and/or combinations thereof.
[0034] A sensor layer stack (e.g., CPP-GMR spin valve) 110 can be
deposited over the first magnetic shield 102 in the sensor region
by sequential deposition of material layers. The sensor layer stack
110 can include a first ferromagnetic layer 112, a barrier spacer
stack 114, and a second ferromagnetic layer 116. In one embodiment,
the sensor layer stack 110 can further include a nonmagnetic seed
layer 111 underneath the first ferromagnetic layer 112, and a
nonmagnetic cap layer 118 above the second ferromagnetic layer 116.
The nonmagnetic seed layer 111 is also referred to as a backside
nonmagnetic conductive layer. The nonmagnetic cap layer 118 is also
referred to as a front-side nonmagnetic conductive layer.
[0035] The nonmagnetic seed layer 111 can include a material layer
or a layer stack that facilitates growth of subsequently layers.
For example, the nonmagnetic seed layer 111 can include materials
such as a graded nickel iron alloy and/or ruthenium, and can have a
thickness in a range from 1 nm to 10 nm, such as 1-2 nm, although
lesser and greater thicknesses can also be employed. In one
embodiment, the nonmagnetic seed layer 111 can include at least one
material selected from ruthenium, silver, and titanium. The
nonmagnetic seed layer 111 is interposed between the first magnetic
shield 102 and the first ferromagnetic layer 112 and functions as
template for crystalline growth of grains of the first
ferromagnetic layer 112. The crystallographic grains of the first
ferromagnetic layer 112 can be aligned to crystallographic grains
of the nonmagnetic seed layer 111.
[0036] The first ferromagnetic layer 112 can include at least one
ferromagnetic alloy layer. In one embodiment, the first
ferromagnetic layer 112 includes a single ferromagnetic alloy
layer, such as Heusler alloy layer. The Heusler alloy layer may
include any suitable ferromagnetic alloy having a formula
M.sub.2TX, where M is a first transition metal, T is a second
transition metal different from the first transition metal and X is
an element from Groups 13 to 17 of the Periodic Table of elements.
For example, M may be Co, Ni, Fe, Pd and/or Mn, T may be Fe, Mn
and/or V and X may be Si, Al, Ge, Sb, Ga and/or Sn. For example,
the ferromagnetic alloy may consist essentially a
cobalt-iron-aluminum (e.g., Co.sub.2FeAl) alloy or a
cobalt-manganese-germanium (Co.sub.2MnGe) alloy.
[0037] In another embodiment, the first ferromagnetic layer 112
includes a ferromagnetic layer stack including at least two
ferromagnetic material sublayers configured to tune the
magnetostriction. For example, the multi-layer stack can include a
stack of a NiFe5% layer and an amorphous CoFeBTa layer and/or a
stack of a Ta layer and a CoFeB layer. The above described Heusler
alloy layer can be deposited on the multi-layer stack in one
embodiment. In yet another embodiment, the first ferromagnetic
layer 112 can comprise a layer or a layer stack including various
materials such as NiFe, NiCo, CoFe, Fe, NiFeCo, CoB, CoFeB, and/or
combinations thereof.
[0038] The thickness of the first ferromagnetic layer 112 can be in
a range from 0.8 nm to 3 nm, such as 1 nm to 2 nm, although lesser
and greater thicknesses can also be employed. In one embodiment,
the first ferromagnetic layer 112 can be a first free layer having
a first magnetization having at least two preferred magnetization
directions. The at least two preferred magnetization directions can
be an up direction and a down direction if the first ferromagnetic
layer 112 has positive axial magnetic anisotropy.
[0039] In another embodiment, the first ferromagnetic layer 112 can
be a pinned layer having a fixed magnetization direction that does
not change during operation of the device. In this case, a
synthetic antiferromagnetic stack (not shown) can be interposed
between the first magnetic shield 102 and the first ferromagnetic
layer 112. For example, the synthetic antiferromagnetic stack can
be located between the nonmagnetic seed layer 111 and the first
ferromagnetic layer 112. The fixed magnetization of the first
ferromagnetic layer 112 can be is pinned to a magnetization within
the synthetic antiferromagnetic stack.
[0040] The barrier spacer stack 114 includes, from bottom to top, a
first diffusion-assist nonmagnetic metallic layer 114A, a
semiconductor spacer layer 114B, and a second diffusion-assist
nonmagnetic metallic layer 114C.
[0041] In one embodiment, the diffusion-assist nonmagnetic metallic
layers 114A and 114C comprise an electrically conductive,
nonmagnetic layers which have a relatively long electron diffusion
length, and which optionally can function as diffusion barriers
which prevent or reduce diffusion of atoms therethrough. In one
embodiment, each of the first diffusion-assist nonmagnetic metallic
layer 114A and the second diffusion-assist nonmagnetic metallic
layer 114C comprises an elemental metal having a
face-centered-cubic (FCC) lattice structure. The FCC lattice
structure of layers 114A and 114C, which when rotated 45 degrees,
can lattice match the Heusler alloy of the first ferromagnetic
layer 112 (e.g., a Heusler alloy having a L21, B2 lattice
structure) and the semiconductor material of the semiconductor
spacer layer 114B (e.g., CIGS semiconductor material having a
chalcopyrite structure).
[0042] In one embodiment, each of the first diffusion-assist
nonmagnetic metallic layer 114A and the second diffusion-assist
nonmagnetic metallic layer 114C can have a thickness in a range
from 1 monolayer of the elemental metal to 3 monolayers of the
elemental metal. In one embodiment, each of the first
diffusion-assist nonmagnetic metallic layer 114A and the second
diffusion-assist nonmagnetic metallic layer 114C comprises a metal
selected from Ag, Au, Cu, or Ti.
[0043] The semiconductor spacer layer 114B comprises semiconductor
material, such as a compound semiconductor material. In one
embodiment, the semiconductor spacer layer 114B includes a compound
semiconductor material containing copper and selenium. In one
embodiment, the semiconductor spacer layer 114B includes a material
selected from a copper-indium-gallium-selenide (CIGS) material, a
copper-indium-selenide (CIS) material, or a copper-gallium-selenide
(CGS) material. Other suitable semiconductor materials may also be
used. In an illustrative example, the semiconductor spacer layer
114B can include a material selected from
Cu(In.sub.xGa.sub.1-x)Se.sub.2 where 0<x<1, CuInSe.sub.2, or
CuGaSe.sub.2.
[0044] In an illustrative example, a copper-indium-gallium-selenide
material in a bulk form has a chalcopyrite crystal structure or
zincblende crystal structure. In one embodiment, the semiconductor
spacer layer 114B has a thickness in a range from 1 nm to 3 nm,
such as 1.5 nm to 2.5 nm.
[0045] The second ferromagnetic layer 116 can include at least one
ferromagnetic alloy layer. In one embodiment, the second
ferromagnetic layer 116 include the same or different material from
the first ferromagnetic layer 112. In one embodiment, the second
ferromagnetic layer 116 includes a single ferromagnetic alloy
layer, such as Heusler alloy layer. The Heusler alloy layer may
include any suitable ferromagnetic alloy having a formula
M.sub.2TX, where M is a first transition metal, T is a second
transition metal different from the first transition metal and X is
an element from Groups 13 to 17 of the Periodic Table of elements.
For example, M may be Co, Ni, Fe, Pd and/or Mn, T may be Fe, Mn
and/or V and X may be Si, Al, Ge, Sb, Ga and/or Sn. For example,
the ferromagnetic alloy may consist essentially a
cobalt-iron-aluminum (e.g., Co.sub.2FeAl) alloy or a
cobalt-manganese-germanium (Co.sub.2MnGe) alloy.
[0046] In another embodiment, the second ferromagnetic layer 116
includes a ferromagnetic layer stack including at least two
ferromagnetic material sublayers configured to tune the
magnetostriction. For example, the multi-layer stack can include a
stack of a NiFe5% layer and an amorphous CoFeBTa layer, and/or a
stack of a Ta layer and a CoFeB layer. The above described Heusler
alloy layer can be deposited under the multi-layer stack in one
embodiment. In yet another embodiment, the second ferromagnetic
layer 116 can comprise a layer or a layer stack including various
materials such as NiFe, NiCo, CoFe, Fe, NiFeCo, CoB, CoFeB, and/or
combinations thereof.
[0047] The thickness of the second ferromagnetic layer 116 can be
in a range from 0.8 nm to 3 nm, such as 1 nm to 2 nm, although
lesser and greater thicknesses can also be employed. In one
embodiment, the second ferromagnetic layer 116 can be a free layer
having a magnetization having at least two preferred magnetization
directions. The at least two preferred magnetization directions can
be an up direction and a bottom direction if the second
ferromagnetic layer 116 has positive axial magnetic anisotropy.
[0048] In one embodiment, the first ferromagnetic layer 112 can be
a first free layer having a first free magnetization and the second
ferromagnetic layer 116 can be a second free layer having a second
free magnetization. In this case, the first ferromagnetic layer 112
and the second ferromagnetic layer 116 can have the same type of
axial anisotropy, i.e., positive axial anisotropy or negative axial
anisotropy. In another embodiment, the second ferromagnetic layer
116 can be a pinned layer having a fixed magnetization direction
that does not change during operation of the device. In this case,
a synthetic antiferromagnetic stack (not shown) can located over
the second ferromagnetic layer 116.
[0049] Thus, in one embodiment, one of the first ferromagnetic
layer 112 and the second ferromagnetic layer 116 may be a free
layer and the other can be a pinned (e.g., reference) layer. In
another embodiment both the first and the second ferromagnetic
layers 112 and 116 may be free layers.
[0050] The nonmagnetic cap layer 118 can comprise, or consist
essentially of, Ag, Ru, Ta, Ti, and/or combinations thereof. The
thickness of the nonmagnetic cap layer 118 can be in a range from 1
nm to 10 nm, such as 1-2 nm, although lesser and greater
thicknesses can also be employed. The nonmagnetic cap layer 118 can
be interposed between the second ferromagnetic layer 116 and a
second magnetic shield to be subsequently formed.
[0051] The sensor layer stack 110 can be deposited by a series of
layer deposition processes such as chemical vapor deposition,
atomic layer deposition, and/or physical vapor deposition. In other
embodiments, other suitable materials known in the art can be used
for any layer within the sensor layer stack 110.
[0052] Thermal processing steps can be used during formation of the
sensor layer stack 110 to increase the grain size and/or to
stabilize the crystal structure in the various material layers of
the sensor layer stack 110. For example, an in-situ post-deposition
thermal anneal process can be performed after deposition of the
first ferromagnetic layer 112. A cryogenic cooling treatment (for
example, down to at least the boiling point of liquid nitrogen) can
be subsequently performed to reduce surface roughness and to
enhance film uniformity for the deposited material layers up to the
first ferromagnetic layer 112. The anneal may also cause
discontinuities in the first ferromagnetic layer 112. The cryogenic
cooling may remove the discontinuities and may the first
ferromagnetic layer 112 continuous.
[0053] FIGS. 5A to 9C illustrate optional patterning steps and
additional optional layers used to form the read head 610. It
should be noted that other patterning steps may be used and that
some of the optional layers may omitted or replaced with other
layers.
[0054] Referring to FIGS. 5A and 5B, the sensor layer stack 110 is
patterned to provide a read sensor stripe 110S between a pair of
recess cavities. The read sensor stripe 110S can have a
substantially uniform vertical cross-sectional view along planes
parallel to the air bearing surface to be subsequently formed,
which are parallel to the vertical cross-sectional plane of FIG.
5B. The read sensor stripe 110S can have a tapered profile such
that upper layers within the patterned sensor layer stack 110 have
lesser areas than lower layers within the patterned sensor layer
stack 110.
[0055] The patterning of the sensor layer stack 110 can be
performed, for example, by applying a photoresist layer 119 over
the blanket (unpatterned) sensor layer stack 110, lithographically
patterning the photoresist layer 119 to form a pair of openings
separated by a rectangular area having parallel edges that are
perpendicular to the air bearing surface to be subsequently formed,
and performing a continuous ion milling process on the layers of
the sensor layer stack 110 to provide a pair of openings through
the sensor layer stack 110 with tapered sidewalls. The photoresist
layer 119 can protect covered regions of the sensor layer stack 110
during the continuous ion milling and subsequent processes. The
taper angle on the sidewalls of the patterned sensor layer stack
110 provides continuous reduction of the width of the layers in the
sensor layer stack 110 within the read sensor stripe 110S.
[0056] Referring to FIGS. 6A and 6B, an electrical isolation
dielectric layer 120 can be formed on the physically exposed top
surfaces of the first magnetic shield 102 and on the sidewalls of
the sensor layer stack 110, which include the sidewalls of the read
sensor stripe 110S. The electrical isolation dielectric layer 120
includes a dielectric material that provides electrical isolation,
and may be formed by a conformal deposition process. For example,
the electrical isolation dielectric layer 120 can comprise, or
consist essentially of, aluminum oxide, magnesium oxide, silicon
nitride, silicon oxide, and/or combinations or stacks thereof.
[0057] A nonmagnetic spacer material layer can be deposited on the
electrical isolation dielectric layer 120. In one embodiment, the
nonmagnetic spacer material layer can comprise, or consist
essentially of, NiFeCr, NiCr, Ta, Ru, Cr, oxides thereof, and/or
combinations thereof.
[0058] An angled milling process can be performed to remove
vertical and tapered portions of the nonmagnetic spacer material
layer. Specifically, the vertical and tapered portions of the
nonmagnetic spacer material layer can be removed along the angled
sides of the sensor layer stack 110. In one embodiment, the angled
milling process removes portions of the nonmagnetic spacer material
layer along the angled sides of the sensor layer stack 110 located
at and above the second ferromagnetic layer 116. Each remaining
portion of nonmagnetic spacer material layer underlying the
horizontal plane including the bottom surface of the second
ferromagnetic layer 116 constitutes a nonmagnetic spacer 122. A
pair of nonmagnetic spacers 122 is formed on the sidewalls of the
read sensor stripe 110S over planar (horizontal) portions of the
electrical isolation dielectric layer 120 that contact the first
magnetic shield 102. Each nonmagnetic spacer 122 has a respective
top surface below the horizontal plane including the bottom surface
of the second ferromagnetic layer 116. The pair of nonmagnetic
spacers 122 is laterally spaced from the read sensor stripe 110S by
tapered portions of the electrical isolation dielectric layer 120.
A remaining portion of the nonmagnetic spacer material layer
overlying the photoresist layer 119 constitutes a nonmagnetic
material layer 122'.
[0059] Referring to FIGS. 7A and 7B, a ferromagnetic side shield
material layer can be anisotropically deposited. The ferromagnetic
side shield material layer can include iron, cobalt, or a
cobalt-iron alloy. A top surface of the ferromagnetic side shield
material layer overlying the nonmagnetic spacers 122 can be at the
level of the interface between the electrical isolation dielectric
layer 120 and the photoresist layer 119.
[0060] An angled milling process can be performed to selectively
remove vertical and tapered portions of the ferromagnetic side
shield material layer. Specifically, the vertical and tapered
portions of the ferromagnetic side shield material layer can be
removed along the angled sides of the sensor layer stack 110. In
one embodiment, the angled milling process removes portions of the
ferromagnetic side shield material layer along the angled sides of
the sensor layer stack 110 located above the nonmagnetic cap layer
118. Each remaining portions of ferromagnetic side shield material
layer underlying filling a pair of cavities in the sensor layer
stack 110 constitutes a pair of side shields 130. The pair of side
shields 130 is formed on the sidewalls of the electrical isolation
dielectric layer 120 over the horizontal plane including the bottom
surfaces of the second ferromagnetic layer 116. The pair of side
shields 130 is laterally spaced from the read sensor stripe 110S by
the electrical isolation dielectric layer 120, and overlies the
pair of nonmagnetic spacers 122.
[0061] Vertical portions of the electrical isolation dielectric
layer 120 that overlie the pair of side shields 130 can be removed
by the angled milling process. The photoresist layer 119, the
nonmagnetic material layer 122', and a remaining portion of the
ferromagnetic side shield material layer overlying the photoresist
layer 119 can be subsequently removed, for example, by a lift-off
process that lifts off the photoresist layer 119. For example, a
wet etch process employing a solvent that dissolves, and/or lifts
off, the photoresist layer 119 may be employed. The pair of side
shields 130 is formed on the electrical isolation dielectric layer
120 on both sides of the read sensor stripe 110S.
[0062] The pair of side shields 130 is spaced from the first
magnetic shield 102 by a planar (horizontal) portion of the
electrical isolation dielectric layer 120 having a planar surface
that is parallel to an interface between the first magnetic shield
102 and the sensor layer stack 110. The pair of side shields 130
can be formed directly on the pair of nonmagnetic spacers 122.
Further, the pair of side shields 130 can be formed directly on a
respective tapered sidewall of the electrical isolation dielectric
layer 120. A top surface of the nonmagnetic cap layer 118 can be
physically exposed, which may be coplanar with, raised above, or
recessed below, top surfaces of the pair of side shields 130. The
pair of side shields 130 provides a magnetic bias to the second
ferromagnetic layer 116 and/or in the first ferromagnetic layer 112
along the horizontal direction, which is the cross-track direction
during operation of the magnetic head 600.
[0063] Referring to FIGS. 8A-8C, a photoresist layer (not shown)
for patterning the backside edge of each magnetic sensor is applied
and patterned over the exemplary structure. The photoresist layer
is applied and patterned to form an opening having a straight edge
that is parallel to the air bearing surface. The straight edge can
overlie a back side of the read sensor stripe 110S and back sides
of the pair of side shields 130. As used herein, a "backside" or
"back side" refers to a side that is distal from the air bearing
surface to be subsequently formed, and a "front side" refers to a
side that is proximal to the air bearing surface to be subsequently
formed. In one embodiment, the opening in the photoresist layer can
have a substantially rectangular shape.
[0064] Unmasked portions of the material layers overlying the first
magnetic shield 102 are patterned by transferring the pattern of
the photoresist layer therethrough. In one embodiment, a first ion
milling process can be performed employing the photoresist layer as
an ion milling mask layer. A backside edge of the sensor layer
stack 110 (e.g., the read sensor stripe 110S) is formed, which is
herein referred to as a sensor backside edge SBE. The sensor
backside edge SBE is formed at a periphery of a recess cavity that
underlies the opening in the photoresist layer.
[0065] A dielectric material, such as aluminum oxide, tantalum
oxide, silicon oxide or silicon nitride is deposited in the
recessed region and over the patterned read sensor stack 110.
Excess portions of the dielectric material is removed from above
the horizontal plane including the top surface of the patterned
read sensor stack 110. A remaining portion of the dielectric
material forms a dielectric fill layer 280 behind patterned read
sensor stack 110. The dielectric fill layer 280 includes a
dielectric material such as aluminum oxide, tantalum oxide, silicon
oxide, silicon nitride, or combinations thereof.
[0066] A second magnetic shield 104 is then formed on the sensor
layer stack 110 and the pair of side shields 130. The second
magnetic shield 104 includes a soft magnetic material, and may have
a thickness in a range from 200 nm to 2,000 nm, although lesser and
great thicknesses can also be employed. The second magnetic shield
104 can be subsequently patterned to provide the upper reading
shield 104 of a magnetic head 600 in a finished product.
[0067] Referring to FIGS. 9A-9C, the writing head 660 is then
formed over the read head 610. A lapping process is then performed
on the exemplary structure to provide an air bearing surface
(ABS).
[0068] Referring to FIG. 10, a first exemplary sensor layer stack
110 according to an embodiment of the present disclosure is
illustrated, which includes, and in one embodiment may consist only
of, from bottom to top, a nonmagnetic seed layer 111, a first
ferromagnetic layer 112, a barrier spacer stack 114, a second
ferromagnetic layer 116, and a nonmagnetic cap layer 118. The
barrier spacer stack 114 includes, from bottom to top, a first
diffusion-assist nonmagnetic metallic layer 114A, a semiconductor
spacer layer 114B, and a second diffusion-assist nonmagnetic
metallic layer 114C. The first ferromagnetic layer 112 can be a
first free layer, and the second ferromagnetic layer 116 can be a
second free layer.
[0069] Referring to FIG. 11, a second exemplary sensor layer stack
110 according to an embodiment of the present disclosure is
illustrated, which is configured to provide tunable
magnetostriction. At least one magnetostriction modulation layer
stack (113, 117) may be included within the sensor layer stack 110.
Specifically, the sensor layer stack 110 can include at least one
of a seed-side magnetostriction modulation layer stack 113 and/or a
cap-side magnetostriction modulation layer stack 117. Thus, the
sensor layer stack 110 can include, from bottom to top, a
nonmagnetic seed layer 111, an optional seed-side magnetostriction
modulation layer stack 113, a first ferromagnetic layer 112, a
barrier spacer stack 114, a second ferromagnetic layer 116, an
optional cap-side magnetostriction modulation layer stack 117, and
a nonmagnetic cap layer 118. The barrier spacer stack 114 includes,
from bottom to top, a first diffusion-assist nonmagnetic metallic
layer 114A, a semiconductor spacer layer 114B, and a second
diffusion-assist nonmagnetic metallic layer 114C. The first
ferromagnetic layer 112 can be a first free layer, and the second
ferromagnetic layer 116 can be a second free layer.
[0070] Each of the first ferromagnetic layer 112 and the second
ferromagnetic layer 116 can have large positive magnetostriction.
The seed-side magnetostriction modulation layer stack 113 and/or
the cap-side magnetostriction modulation layer stack 117 can
include a negative magnetostriction material layer (113A, 117A)
that can provide negative magnetostriction to reduce the positive
magnetostriction provided by the first ferromagnetic layer 112 and
the second ferromagnetic layer 116. The negative magnetostriction
material layers (113A, 117A) can be spaced from the first
ferromagnetic layer 112 and the second ferromagnetic layer 116 by a
combination of an amorphous nonmagnetic material layer (113B, 117B)
and an amorphous magnetic material layer (113C, 117C). In one
embodiment, the seed-side magnetostriction modulation layer stack
113 can include, from bottom to top (i.e., in a direction toward
the barrier spacer stack 114), a seed-side negative
magnetostriction material layer 113A, a seed-side amorphous
nonmagnetic material layer 113B, and a seed-side amorphous magnetic
material layer 113C. The cap-side magnetostriction modulation layer
stack 117 can include, from bottom to top (i.e., in a direction
away from the barrier spacer stack 114), a cap-side amorphous
magnetic material layer 117C, a cap-side amorphous nonmagnetic
material layer 117B, and a cap-side negative magnetostriction
material layer 117A. In an illustrative example, the negative
magnetostriction material layers (113A, 117A) can include NiFe5%,
the amorphous nonmagnetic material layers (113B, 117B) can include
amorphous tantalum, and the amorphous magnetic material layers
(113C, 117C) can include amorphous CoFeB alloy.
[0071] Referring to FIG. 12, a third exemplary sensor layer stack
110 according to an embodiment of the present disclosure is
illustrated, which can be derived from the second exemplary sensor
layer stack 110 by inserting a synthetic antiferromagnetic (SAF)
structure (212, 214, 216) between the nonmagnetic seed layer 111
and the first ferromagnetic layer 112. The first ferromagnetic
layer 112 becomes a pinned (i.e., reference) layer having a fixed
magnetization direction, and sensing of magnetization can be
performed by the second ferromagnetic layer 116 that becomes the
only free layer within the third exemplary sensor layer stack
110.
[0072] The SAF structure (212, 214, 216) can include an
antiferromagnetic pinning layer 212, a ferromagnetic pinned layer
214, and a nonmagnetic spacer layer 216. The anti-ferromagnetic
pinning layer 212 can comprise, or consist essentially of, IrMn,
IrMnCr, and/or combinations thereof. The ferromagnetic pinned layer
214 can comprise CoFe, CoB, CoFeB, and/or combinations thereof. The
nonmagnetic spacer layer 216 includes a nonmagnetic material such
as ruthenium. The SAF structure (212, 214, 216) fixes the direction
of magnetization of the first ferromagnetic layer 112, causing the
first ferromagnetic layer 112 to function as a pinned magnetization
layer.
[0073] In one embodiment, at least one of the seed-side
magnetostriction modulation layer stack 113 and/or the cap-side
magnetostriction modulation layer stack 117 may be present within
the third exemplary sensor layer stack 110. If the seed-side
magnetostriction modulation layer stack 113 is present within the
third exemplary sensor layer stack 110, then the SAF structure
(212, 214, 216) can be provided between the nonmagnetic seed layer
111 and the seed-side magnetostriction modulation layer stack
113.
[0074] In another embodiment, if the cap-side magnetostriction
modulation layer stack 117 is present within the third exemplary
sensor layer stack 110, then the negative magnetostriction material
layer 113A such as NiFe5% can be replaced with a cobalt layer.
[0075] Referring to FIG. 13, the relationship between a
resistance-area (RA) product (e.g., in units of Ohm-microns square)
and MR ratio is calculated and plotted for three sensor layer
stacks. The first curve 1310 represents the relationship between RA
and MR ratio for a first comparative example sensor layer stack
that is derived from the first exemplary sensor layer stack 110 of
FIG. 10 by removing the first diffusion-assist nonmagnetic metallic
layer 114A and the second diffusion-assist nonmagnetic metallic
layer 114C. In other words, only the semiconductor spacer layer
114B remains out of the barrier spacer layer stack 114 of the first
exemplary sensor layer stack 110 of FIG. 10.
[0076] The second curve 1320 represents the relationship between RA
and MR ratio for a second exemplary sensor layer stack 110 of FIG.
10 which includes copper first diffusion-assist nonmagnetic
metallic layer 114A and copper second diffusion-assist nonmagnetic
metallic layer 114C. The third curve 1330 represents the
relationship between RA and MR ratio for a third exemplary sensor
layer stack 110 of FIG. 10 which includes a silver first
diffusion-assist nonmagnetic metallic layer 114A and a silver
second diffusion-assist nonmagnetic metallic layer 114C.
[0077] The use of copper layers as the first diffusion-assist
nonmagnetic metallic layer 114A and the second diffusion-assist
nonmagnetic metallic layer 114C within a barrier spacer layer stack
114 improves MR ratio compared to the comparative example,
especially for low RA values. The use of silver layers as the first
diffusion-assist nonmagnetic metallic layer 114A and the second
diffusion-assist nonmagnetic metallic layer 114C within a barrier
spacer layer stack 114 improves the MR ratio for low RA values even
more than use of the copper layers. Thus, MR can be detected (e.g.,
has a value between 15 and 39%) for low RA values (e.g., below 0.2,
such as between 0.1 and 0.15 Ohm-microns square) for the second and
third exemplary sensor layer stacks, but essentially cannot be
detected (e.g., MR value below 3%) for the comparative example
sensor layer stack.
[0078] Without being bound by any particular theory, the long
electron diffusion length of the first diffusion-assist nonmagnetic
metallic layer 114A and the second diffusion-assist nonmagnetic
metallic layer 114C is believed to be a factor in increasing the MR
ratio in the barrier spacer layer stack 114 of the embodiments of
the present disclosure by reducing interlayer coupling between the
first and the second ferromagnetic layers (112, 116). Thus, the
long spin diffusion length of the diffusion-assist nonmagnetic
metallic layers (114A, 114C) can keep the high spin polarization of
the ferromagnetic layers, such as the Heusler alloy ferromagnetic
layers (112, 116) and reduce the interlayer coupling to achieve
ultra-low RA with reasonable MR value.
[0079] Further, it is believed that lattice matching between the
crystal structure of the semiconductor spacer layer 114B and the
thin films of the first diffusion-assist nonmagnetic metallic layer
114A and the second diffusion-assist nonmagnetic metallic layer
114C may contribute to improved semiconductor spacer layer 114B
grain size and interface properties by improving grain growth
during deposition of the semiconductor spacer layer 114B and/or by
reducing or preventing interdiffusion between the semiconductor
spacer layer 114B and the ferromagnetic layers (112, 116).
[0080] Referring to FIG. 14, an R-H curve of resistance (in Ohms)
as a function of an applied magnetic field (in Oe) is plotted for a
sensor layer stack 110 of an embodiment of the present disclosure
that includes silver first diffusion-assist nonmagnetic metallic
layer 114A and silver second diffusion-assist nonmagnetic metallic
layer 114C. A resistance-area product of 0.098 Ohm-.mu.m.sup.2 with
MR ratio of 39% is used in FIG. 14.
[0081] Referring to all embodiments described above, a read head
610 includes a first ferromagnetic layer 112, a second
ferromagnetic layer 116, a first diffusion-assist nonmagnetic
metallic layer 114A located between the first ferromagnetic layer
and the second ferromagnetic layer, a second diffusion-assist
nonmagnetic metallic layer 114C located between the first
ferromagnetic layer and the second ferromagnetic layer, and a
semiconductor spacer layer 114B located between the first
diffusion-assist nonmagnetic metallic layer and the second
diffusion-assist nonmagnetic metallic layer.
[0082] In one embodiment, the semiconductor spacer layer 114B
directly contacts both the first diffusion-assist nonmagnetic
metallic layer 114A and the second diffusion-assist nonmagnetic
metallic layer 114C. In one embodiment, the first ferromagnetic
layer 112 directly contacts the first diffusion-assist nonmagnetic
metallic layer 114A, and the second ferromagnetic layer 116
directly contacts the second diffusion-assist nonmagnetic metallic
layer 114C.
[0083] In one embodiment, each of the first diffusion-assist
nonmagnetic metallic layer 114A and the second diffusion-assist
nonmagnetic metallic layer 114C comprises a metal selected from Ag,
Au, Cu, or Ti. The semiconductor spacer layer 114B comprises a
material selected from copper-indium-gallium-selenide,
copper-indium-selenide or copper-gallium-selenide. At least one of
the first ferromagnetic layer 112 and the second ferromagnetic
layer 116 comprises a ferromagnetic Heusler alloy layer, such as a
Co.sub.2FeAl alloy or a Co.sub.2MnGe alloy layer
[0084] In one embodiment, each of the first diffusion-assist
nonmagnetic metallic layer 114A and the second diffusion-assist
nonmagnetic metallic layer 114C comprises an elemental metal
selected from Ag, Cu, Au or Ti which has a thickness in a range
from 1 monolayer of the elemental metal to 3 monolayers of the
elemental metal, the semiconductor spacer layer 114B has a
thickness in a range from 1 nm to 3 nm, and each of the first
ferromagnetic layer 112 and the second ferromagnetic layer 116 has
a thickness in a range from 0.8 nm to 3 nm.
[0085] In another embodiment shown in FIG. 11, at least one of the
first ferromagnetic layer and the second ferromagnetic layer
comprises a layer stack comprising a negative magnetostriction
material layer (113A, 117A), an amorphous nonmagnetic material
layer (113B, 117B), an amorphous magnetic material layer (113C,
117C) and a Heusler alloy magnetic material layer (112, 116). In
one embodiment, the negative magnetostriction material layer
comprises a NiFe5% alloy, the amorphous nonmagnetic material layer
comprises amorphous tantalum which directly contacts the negative
magnetostriction material layer, the amorphous magnetic material
layer comprises an amorphous CoFeB alloy which directly contacts
the amorphous nonmagnetic material layer, and the Heusler alloy
magnetic material layer comprises a Co.sub.2FeAl alloy or a
Co.sub.2MnGe alloy which directly contacts the amorphous magnetic
material layer.
[0086] In some embodiments shown in FIGS. 10 and 11, the first
ferromagnetic layer 112 is a first free layer having a first
magnetization having at least two preferred magnetization
directions, and the second ferromagnetic layer 116 is a second free
layer having a second magnetization having at least two preferred
magnetization directions.
[0087] In another embodiment shown in FIG. 12, a synthetic
antiferromagnetic stack (212, 214, 216) is provided, such that one
of the first and the second ferromagnetic layers (112, 116)
comprises a free layer and the other one of the first and the
second ferromagnetic layers (112, 116) comprises a pinned reference
layer.
[0088] In one embodiment the read head further comprises a first
magnetic shield 102 and a second magnetic shield 104. A sensor
layer stack 110 comprising the first ferromagnetic layer, the
second ferromagnetic layer, the first diffusion-assist nonmagnetic
metallic layer, the second diffusion-assist nonmagnetic metallic
layer and the semiconductor spacer layer is located between the
first magnetic shield 102 and the second magnetic shield 104.
[0089] The various sensor layer stacks 110 of the embodiments of
the present disclosure can be included in a read head of a magnetic
head of a hard disk drive, such as a hard disk drive 300 shown in
FIGS. 1 and 2. As described above, the hard disk drive 300 can
include a slider 308 supporting the magnetic head 600, an actuator
arm 309 supporting the slider, a motor 310 configured to control
the actuator arm, and a magnetic disk 302. The first
diffusion-assist nonmagnetic metallic layer 114A and/or the second
diffusion-assist nonmagnetic metallic layer 114C can significantly
increase magnetoresistance for a layer stack having a low
resistance-area product, thereby increasing the sensitivity of the
read head.
[0090] Although the foregoing refers to particular preferred
embodiments, it will be understood that the disclosure is not so
limited. It will occur to those of ordinary skill in the art that
various modifications may be made to the disclosed embodiments and
that such modifications are intended to be within the scope of the
disclosure. Where an embodiment employing a particular structure
and/or configuration is illustrated in the present disclosure, it
is understood that the present disclosure may be practiced with any
other compatible structures and/or configurations that are
functionally equivalent provided that such substitutions are not
explicitly forbidden or otherwise known to be impossible to one of
ordinary skill in the art. All of the publications, patent
applications and patents cited herein are incorporated herein by
reference in their entirety.
* * * * *