U.S. patent application number 15/198691 was filed with the patent office on 2016-10-20 for underlayer for reference layer of polycrystalline cpp gmr sensor stack.
The applicant listed for this patent is HGST Netherlands B.V.. Invention is credited to Jeffrey Robinson CHILDRESS, Young-Suk CHOI, Tomoya NAKATANI, John C. READ.
Application Number | 20160307587 15/198691 |
Document ID | / |
Family ID | 55455345 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160307587 |
Kind Code |
A1 |
CHILDRESS; Jeffrey Robinson ;
et al. |
October 20, 2016 |
UNDERLAYER FOR REFERENCE LAYER OF POLYCRYSTALLINE CPP GMR SENSOR
STACK
Abstract
Embodiments disclosed herein generally relate to a magnetic head
having an amorphous ferromagnetic reference layer. The
ferromagnetic reference layer may have amorphous structure as a
result of an amorphous ferromagnetic underlayer that the
ferromagnetic reference layer is deposited thereon. The amorphous
ferromagnetic reference layer enhances magnetoresistance, leading
to an improved magnetic head.
Inventors: |
CHILDRESS; Jeffrey Robinson;
(San Jose, CA) ; CHOI; Young-Suk; (Los Gatos,
CA) ; NAKATANI; Tomoya; (San Jose, CA) ; READ;
John C.; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HGST Netherlands B.V. |
Amsterdam |
|
NL |
|
|
Family ID: |
55455345 |
Appl. No.: |
15/198691 |
Filed: |
June 30, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14488735 |
Sep 17, 2014 |
9412399 |
|
|
15198691 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 43/10 20130101;
H01L 43/08 20130101; G11B 5/3906 20130101; G11B 2005/3996 20130101;
G01R 33/093 20130101; G11B 5/3903 20130101 |
International
Class: |
G11B 5/39 20060101
G11B005/39 |
Claims
1. A magnetic head, comprising: a sensor stack, wherein the sensor
stack includes: an antiferromagnetic layer; a ferromagnetic pinned
layer disposed on the antiferromagnetic layer; a first nonmagnetic
layer disposed on the ferromagnetic pinned layer; a first
crystalline ferromagnetic underlayer disposed on the first
nonmagnetic layer; an amorphous ferromagnetic reference layer
disposed over the first crystalline ferromagnetic underlayer; a
second nonmagnetic layer disposed on the amorphous ferromagnetic
reference layer; a second crystalline ferromagnetic underlayer
disposed on the second nonmagnetic layer; and a ferromagnetic free
layer disposed over the second crystalline ferromagnetic
underlayer.
2. The magnetic head of claim 1, further comprising a first
amorphous ferromagnetic underlayer disposed between the first
crystalline ferromagnetic underlayer and the amorphous
ferromagnetic reference layer.
3. The magnetic head of claim 2, wherein the first amorphous
ferromagnetic underlayer comprises CoFeBTa, CoTiB or CoFeGe.
4. The magnetic head of claim 2, further comprising a second
amorphous ferromagnetic underlayer disposed between the second
crystalline ferromagnetic underlayer and the ferromagnetic free
layer.
5. The magnetic head of claim 4, wherein the second amorphous
ferromagnetic underlayer comprises CoFeBTa, CoTiB or CoFeGe.
6. The magnetic head of claim 1, wherein the ferromagnetic free
layer is amorphous.
7. The magnetic head of claim 1, wherein the amorphous
ferromagnetic reference layer is deposited on the first crystalline
ferromagnetic underlayer at a temperature between about 50 K to
about 100 K.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of co-pending
U.S. patent application Ser. No. 14/488,735, filed on Sep. 17,
2014, which is herein incorporated by reference.
BACKGROUND
[0002] 1. Field
[0003] Embodiments disclosed herein generally relate to a magnetic
read head for use in a hard disk drive.
[0004] 2. Description of the Related Art
[0005] The heart of a computer is a magnetic disk drive which
typically includes a rotating magnetic disk, a slider that has read
and write heads, a suspension arm above the rotating disk and an
actuator arm that swings the suspension arm to place the read
and/or write heads over selected tracks on the rotating disk. The
suspension arm biases the slider towards the surface of the disk
when the disk is not rotating but, when the disk rotates, air is
swirled by the rotating disk adjacent a media facing surface (MFS)
of the slider causing the slider to ride on an air bearing a slight
distance from the surface of 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 signal fields
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.
[0006] One type of conventional magnetoresistive (MR) sensor used
as the read head is a "spin-valve" sensor based on the giant
magnetoresistance (GMR) effect. A GMR-spin-valve sensor has a stack
of layers that includes two ferromagnetic layers separated by a
nonmagnetic electrically conductive spacer layer. One ferromagnetic
layer, typically called the "reference" layer, has its
magnetization direction fixed, such as by being pinned by exchange
coupling with an adjacent antiferromagnetic "pinning" layer, and
the other ferromagnetic layer, typically called the "free" layer,
has its magnetization direction free to rotate in the presence of
an external magnetic field. With a sense current applied to the
sensor, the rotation of the free layer magnetization relative to
the fixed layer magnetization is detectable as a change in
electrical resistance. If the sense current is directed
perpendicularly through the planes of the layers in the sensor
stack, the sensor is referred to as
current-perpendicular-to-the-plane (CPP) sensor. Metallic CPP GMR
sensor having low magnetoresistance is beneficial to increase
signal to noise ratio, but the signal output of metallic CPP GMR
sensor using transition magnetic metals is too low. In order to
increase the signal output, Heusler alloy with high spin
polarization is used in the reference layer.
[0007] However, Heusler alloy is deposited using high temperature
and/or thick crystalline template, which may cause sensor
performance to degrade. Therefore, an improved read head is
needed.
SUMMARY
[0008] Embodiments disclosed herein generally relate to a magnetic
head having an amorphous ferromagnetic reference layer. The
ferromagnetic reference layer may have amorphous structure as a
result of an amorphous ferromagnetic underlayer that the
ferromagnetic reference layer is deposited thereon. The amorphous
ferromagnetic reference layer enhances magnetoresistance, leading
to an improved magnetic head.
[0009] In one embodiment, a magnetic head is disclosed. The
magnetic head includes a sensor stack, and the sensor stack
includes an antiferromagnetic layer, a first crystalline
ferromagnetic underlayer, an amorphous ferromagnetic reference
layer disposed over the first crystalline ferromagnetic underlayer,
a nonmagnetic layer disposed on the amorphous ferromagnetic
reference layer, a second crystalline ferromagnetic underlayer
disposed on the nonmagnetic layer, and a ferromagnetic free layer
disposed over the second crystalline ferromagnetic underlayer.
[0010] In another embodiment, a magnetic head is disclosed. The
magnetic head includes a sensor stack, and the sensor stack
includes an antiferromagnetic layer, a ferromagnetic pinned layer
disposed on the antiferromagnetic layer, a first nonmagnetic layer
disposed on the ferromagnetic pinned layer, a first crystalline
ferromagnetic underlayer disposed on the first nonmagnetic layer,
an amorphous ferromagnetic reference layer disposed over the first
crystalline ferromagnetic underlayer, a second nonmagnetic layer
disposed on the amorphous ferromagnetic reference layer, a second
crystalline ferromagnetic underlayer disposed on the second
nonmagnetic layer, and a ferromagnetic free layer disposed over the
second crystalline ferromagnetic underlayer.
[0011] In another embodiment, a hard disk drive is disclosed. The
hard disk drive includes a magnetic media, a magnetic write head,
and a magnetic read head. The magnetic read head includes a sensor
stack, and the sensor stack includes an antiferromagnetic layer, a
first crystalline ferromagnetic underlayer disposed over the
antiferromagnetic layer, a first amorphous ferromagnetic underlayer
disposed over the first crystalline ferromagnetic underlayer, an
amorphous ferromagnetic reference layer disposed over the
antiferromagnetic layer, a first nonmagnetic layer disposed over
the amorphous ferromagnetic reference layer, a second crystalline
ferromagnetic underlayer disposed over the first nonmagnetic layer,
a second amorphous ferromagnetic underlayer disposed over the
second crystalline ferromagnetic underlayer, and an amorphous
ferromagnetic free layer disposed over the second amorphous
ferromagnetic underlayer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above recited features of
the present disclosure can be understood in detail, a more
particular description of the disclosure, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this disclosure and are therefore not to be considered limiting of
its scope, for the disclosure may admit to other equally effective
embodiments in any field involving magnetic sensors.
[0013] FIG. 1 illustrates a disk drive system, according to
embodiments described herein.
[0014] FIG. 2A is a cross sectional side view of a read/write head
and magnetic disk of the disk drive of FIG. 1, according to
embodiments described herein.
[0015] FIG. 2B is a schematic cross sectional view of a portion of
the read magnetic head according to one embodiment.
[0016] FIG. 3 is a schematic cross sectional view of a sensor stack
according to one embodiment.
[0017] FIG. 4 is a schematic cross sectional view of a sensor stack
according to one embodiment.
[0018] FIG. 5 is a schematic cross sectional view of a sensor stack
according to one embodiment.
[0019] FIG. 6 is a schematic cross sectional view of a sensor stack
according to one embodiment.
[0020] FIG. 7 is a schematic cross sectional view of a sensor stack
according to one embodiment.
[0021] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0022] In the following, reference is made to embodiments. However,
it should be understood that the disclosure is not limited to
specific described embodiments. Instead, any combination of the
following features and elements, whether related to different
embodiments or not, is contemplated to implement and practice the
claimed subject matter. Furthermore, although embodiments may
achieve advantages over other possible solutions and/or over the
prior art, whether or not a particular advantage is achieved by a
given embodiment is not limiting of the disclosure. Thus, the
following aspects, features, embodiments and advantages are merely
illustrative and are not considered elements or limitations of the
appended claims except where explicitly recited in a claim(s).
[0023] Embodiments disclosed herein generally relate to a magnetic
head having an amorphous ferromagnetic reference layer. The
ferromagnetic reference layer may have amorphous structure as a
result of an amorphous ferromagnetic underlayer that the
ferromagnetic reference layer is deposited thereon. The amorphous
ferromagnetic reference layer enhances magnetoresistance, leading
to an improved magnetic head.
[0024] FIG. 1 illustrates a disk drive 100 according to one
embodiment disclosed herein. As shown, at least one rotatable
magnetic media 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 any suitable patterns of data tracks, such as annular
patterns of concentric data tracks (not shown) on the magnetic
media 112.
[0025] At least one slider 113 is positioned near the magnetic
media 112, each slider 113 supporting one or more magnetic head
assemblies 121. As the magnetic disk rotates, the slider 113 moves
radially in and out over the disk surface 122 so that the magnetic
head assembly 121 may access different tracks of the magnetic media
112 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 the slider 113 towards
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
control unit 129.
[0026] During operation of the disk drive 100, the rotation of the
magnetic media 112 generates an air bearing between the slider 113
and the disk surface 122 which exerts an upward force or lift on
the slider 113. The air bearing thus counter-balances the slight
spring force of suspension 115 and supports slider 113 off and
slightly above the media 112 surface by a small, substantially
constant spacing during normal operation.
[0027] The various components of the disk drive 100 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 media 112. Write and read signals are
communicated to and from write and read heads on the assembly 121
by way of recording channel 125.
[0028] 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.
[0029] FIG. 2A is a fragmented, cross sectional side view through
the center of a read/write head 200 mounted on the slider 113 and
facing magnetic media 112. In some embodiments, the magnetic media
112 may be a "dual-layer" medium that includes a perpendicular
magnetic data recording layer (RL) 204 on a "soft" or relatively
low-coercivity magnetically permeable underlayer (PL) 206 formed on
a disk substrate 208. The read/write head 200 includes a MFS 202, a
magnetic write head 210 and a magnetic read head 211, and is
mounted such that the MFS 202 is facing the magnetic media 112. In
FIG. 2A, the media 112 moves past the write head 210 in the
direction indicated by the arrow 232, so the portion of the
read/write head 200 that is opposite the slider 113 is often called
the "trailing" end 203.
[0030] In some embodiments, the magnetic read head 211 is a MR read
head that includes a MR sensing element 230 located between MR
shields S1 and S2. The RL 204 is illustrated with perpendicularly
recorded or magnetized regions, with adjacent regions having
magnetization directions, as represented by the arrows located in
the RL 204. The magnetic fields of the adjacent magnetized regions
are detectable by the MR sensing element 230 as the recorded
bits.
[0031] The write head 210 includes a magnetic circuit made up of a
main pole 212 and a yoke 216. The write head 210 also includes a
thin film coil 218 shown in the section embedded in non-magnetic
material 219 and wrapped around yoke 216. In an alternative
embodiment, the yoke 216 may be omitted, and the coil 218 may wrap
around the main pole 212. A write pole 220 is magnetically
connected to the main pole 212 and has an end 226 that defines part
of the MFS 202 of the magnetic write head 210 facing the outer
surface of media 112.
[0032] Write pole 220 may be a flared write pole and may include a
flare point 222 and a pole tip 224 that includes the end 226. The
flare may extend the entire height of write pole 220 (i.e., from
the end 226 of the write pole 220 to the top of the write pole
220), or may only extend from the flare point 222, as shown in FIG.
2A. In one embodiment the distance between the flare point 222 and
the ABS is between about 30 nm and about 150 nm.
[0033] The write pole 220 includes a tapered surface 271 which
increases the width of the write pole 220 from a first width W1 at
the MFS 202 to a second width W2 away from the MFS 202. In one
embodiment, the width W1 may be between around 60 nm and 200 nm,
and the width W2 may be between around 120 nm and 350 nm. While the
tapered region 271 is shown with a single straight surface in FIG.
2A, in alternative embodiment, the tapered region 271 may include a
plurality of tapered surfaces with different taper angles with
respect to the MFS 202.
[0034] The tapering improves magnetic performance. For example,
reducing the width W1 at the MFS 202 may concentrate a magnetic
field generated by the write pole 220 over portions of the magnetic
media 112. In other words, reducing the width W1 of the write pole
220 at the MFS 202 reduces the probability that tracks adjacent to
a specified track are erroneously altered during writing
operations.
[0035] In operation, write current passes through the coil 218 and
induces a magnetic field (shown by dashed line 228) from the write
pole 220 that passes through the RL 204 (to magnetize the region of
the RL 204 beneath the write pole 220), through the flux return
path provided by the PL 206, and back to an upper return pole 250.
In one embodiment, the greater the magnetic flux of the write pole
220, the greater the probability of accurately writing to specified
regions of the RL 204.
[0036] FIG. 2A further illustrates one embodiment of the upper
return pole 250 may be a magnetic shield that is separated from
write pole 220 by a nonmagnetic gap layer 256. In some embodiments,
the upper return pole 250 may be a trailing shield wherein
substantially all of the shield material is on the trailing end
203. Alternatively, in some embodiments, the upper return pole 250
may be a wrap-around shield wherein the shield covers the trailing
end 203 and also wraps around the sides of the write pole 220. As
FIG. 2A is a cross section through the center of the read/write
head 200, it represents both trailing and wrap-around
embodiments.
[0037] Near the MFS 202, the nonmagnetic gap layer 256 has a
reduced thickness and forms a shield throat gap 258. The throat gap
width is generally defined as the distance between the write pole
220 and the upper return pole 250 at the MFS 202. The upper return
pole 250 is formed of magnetically permeable material (such as Ni,
Co and Fe alloys) and the gap layer 256 is formed of nonmagnetic
material (such as Ta, TaO, Ru, Rh, NiCr, SiC or Al.sub.2O.sub.3). A
taper 260 in the gap material provides a gradual transition from
the throat gap width at the MFS 202 to a maximum gap width above
the taper 260. This gradual transition in width forms a tapered
bump in the nonmagnetic gap layer 256 that allows for greater
magnetic flux density from the write pole 220, while avoiding
saturation of the upper return pole 250.
[0038] FIG. 2B is a schematic cross sectional view of a portion of
the magnetic head 211 according to one embodiment. The thickness
and the width of each layer, are for example only, and each layer
may be thicker/thinner and/or wider/narrower. The magnetic head 211
includes a first shield layer 231 and a second shield layer 246.
The first and second shield layers 231, 246 may be the MR shields
S1, S2 described in FIG. 2A. The first and second shield layers
231, 246 may each comprise a ferromagnetic material. Suitable
ferromagnetic materials that may be utilized include Ni, Fe, Co,
NiFe, NiFeCo, NiCo, CoFe and combinations thereof.
[0039] The magnetic head 211 also includes a sensor stack 234
(discussed in detail below). The sensor stack 234 may be the
sensing element 230 described in FIG. 2A. Following the formation
of the sensor stack 234, an insulating layer 240 may be deposited
on the first shield layer 231 as well as the sidewalls of the
sensor stack 234. The insulating layer 240 may comprise an
insulating material such as aluminum oxide. The insulating layer
240 may be deposited by well known deposition methods such as
atomic layer deposition (ALD), chemical vapor deposition (CVD),
sputtering, etc. After the insulating layer 240 is deposited, a
hard bias layer 242 is then deposited. The hard bias layer 242 may
comprise a material having a high magnetic moment such as CoFe.
[0040] Once the hard bias layer 242 is deposited, a hard bias
capping structure 244 may be formed. In one embodiment, the hard
bias capping structure 244 may comprise a multiple layer structure
comprising a first tantalum layer, an iridium layer, and a second
tantalum layer. The sensor stack 234, the insulating layer 240, the
hard bias layer 242 and the hard bias capping structure 244 may be
disposed between the first and second shield layers 231, 246.
[0041] FIG. 3 is a schematic cross sectional view of a sensor stack
300 according to one embodiment. The sensor stack 300 may be the
sensor stack 234 described in FIG. 2B. The sensor stack 300 may
include one or more seed layers 302 to promote the optimal grain
size and texture of an antiferromagnetic layer 304, which may be
deposited on the one or more seed layers 302. The one or more seed
layers 302 may comprise Ta, Ru, NiFe, NiFeCr, CoFe, CoFeB, CoHf, Cu
or combinations thereof. The antiferromagnetic layer 304 may
comprise Pt, Ir, Rh, Ni, Fe, Mn, or combinations thereof such as
PtMn, PtPdMn, NiMn or IrMn. A ferromagnetic reference layer 306 may
be deposited over the antiferromagnetic layer 304. The word over,
as used in this application, means that a first layer is disposed
above a second layer, and may or may not be in direct contact with
the second layer. There may or may not be additional layers
disposed between the first and second layers. The word on, as used
in this application, means that a first layer is disposed on and
directly contacting a second layer, and there may not be any
additional layers disposed between the first and second layers. The
word over has a broader scope when describing the layers comparing
to the word on. The ferromagnetic reference layer 306 may be
amorphous, which enhances magnetoresistance. A crystalline
ferromagnetic underlayer 305 may be disposed between the amorphous
ferromagnetic reference layer 306 and the antiferromagnetic layer
304 in order to enhance the pinning strength. The crystalline
ferromagnetic underlayer 305 may include Co, Fe, Ni, or any
combinations thereof.
[0042] Conventionally, the reference layer is made of a Heusler
alloy, which has crystalline structure, and is formed under high
temperature such as greater than 150 degrees Celsius and/or using a
thick crystalline template. The high temperature process can damage
various magnetic coupling and thick crystalline template increases
the read gap. In order to form the amorphous ferromagnetic
reference layer 306, the deposition temperature of the reference
layer 306 may be very low, such as between about 50 K to about 100
K. In one embodiment, the substrate on which the crystalline
ferromagnetic underlayer 305 is deposited is placed on a cryogenic
stage when the reference layer 306 is deposited on the crystalline
ferromagnetic underlayer 305 by physical vapor deposition (PVD).
Another method for forming the amorphous ferromagnetic reference
layer 306 is to flow an oxygen containing gas into the deposition
chamber before depositing the reference layer 306. As a result, an
oxygen surfactant layer may be formed on the crystalline
ferromagnetic underlayer 305, which causes the ferromagnetic
reference layer 306 that is deposited thereon to have an amorphous
structure. Another method for forming the amorphous ferromagnetic
reference layer 306 is to dope the Heusler alloy that would be used
for the reference layer 306 with one or more glass forming dopants,
such as boron. The glass forming dopants do not have solid
solubility with the Heusler alloy and after post anneal the dopants
diffuse out from the Heusler alloy, leading to an amorphous
ferromagnetic reference layer 306. The amorphous ferromagnetic
reference layer 306 may comprise any Heusler alloy.
[0043] A nonmagnetic spacer layer 308 may be deposited on the
amorphous ferromagnetic reference layer 306. The spacer layer 308
may comprise Cu, Ag, or AgSn. A crystalline ferromagnetic
underlayer 309 may be deposited on the spacer layer 308. The
crystalline ferromagnetic underlayer 309 may comprise the same
materials as the crystalline ferromagnetic underlayer 305. A
ferromagnetic free layer 310 may be deposited over the nonmagnetic
spacer layer 308, such as on the crystalline ferromagnetic
underlayer 309. The ferromagnetic free layer 310 may be amorphous
or crystalline. Having an amorphous ferromagnetic free layer 310
may further enhance magnetoresistance. Similar methods may be
performed to form the amorphous ferromagnetic free layer 310 on the
crystalline ferromagnetic underlayer 309, such as having a low
deposition temperature, forming an oxygen surfactant layer and
doping with one or more glass forming dopants. The amorphous
ferromagnetic free layer 310 may comprise any Heusler alloy. In one
embodiment, the ferromagnetic free layer 310 is crystalline, and is
deposited directly on the nonmagnetic spacer layer 308. The
crystalline ferromagnetic underlayer 309 may not be present in the
stack if the ferromagnetic free layer 310 is crystalline. A capping
layer 312 may be deposited on the ferromagnetic free layer 310. The
capping layer 312 may comprise Hf, Ru, Ta or combination
thereof.
[0044] FIG. 4 is a schematic cross sectional view of a sensor stack
400 according to one embodiment. The sensor stack 400 may be the
sensor stack 234 described in FIG. 2B. The sensor stack 400 may
include one or more seed layers 402, which may comprise the same
materials as the one or more seed layers 302 described in FIG. 3.
An antiferromagnetic layer 404 may be deposited on the one or more
seed layers 402, and the antiferromagnetic layer 404 may comprise
the same materials as the antiferromagnetic layer 304 described in
FIG. 3. A crystalline ferromagnetic underlayer 405 may be deposited
on the antiferromagnetic layer 404. The crystalline ferromagnetic
underlayer 405 may comprise the same materials as the crystalline
ferromagnetic underlayer 305 described in FIG. 3. An amorphous
ferromagnetic underlayer 406 may be deposited on the crystalline
ferromagnetic underlayer 405. The amorphous ferromagnetic
underlayer 406 may comprise an alloy of one or more of Co, Fe, Ni,
Ta, Ti, Zr, Nb, Si, W, Ge and B. In one embodiment, the amorphous
ferromagnetic underlayer 406 is a CoFeBTa layer, a CoTiB layer or a
CoFeGe layer. A ferromagnetic reference layer 408 may be deposited
on the amorphous ferromagnetic underlayer 406, and the
ferromagnetic reference layer 408 may be amorphous due to the
amorphous structure of the underlayer 406. The reference layer 408
may comprise one or more magnetic materials such as, for example
NiFe, CoFe, CoFeB, or diluted magnetic alloys. In one embodiment,
the reference layer 408 is made of the same material as the
amorphous ferromagnetic underlayer 406.
[0045] A nonmagnetic spacer layer 410 may be deposited on the
amorphous ferromagnetic reference layer 408 and the nonmagnetic
spacer layer 410 may comprise the same materials as the nonmagnetic
spacer layer 308 described in FIG. 3. A crystalline ferromagnetic
underlayer 411 may be deposited on the spacer layer 410, and the
crystalline ferromagnetic underlayer 411 may comprise the same
materials as the crystalline ferromagnetic underlayer 305 described
in FIG. 3. Another amorphous ferromagnetic underlayer 412 may be
deposited over the nonmagnetic spacer layer 410, such as on the
crystalline ferromagnetic underlayer 411. The amorphous
ferromagnetic underlayer 412 may comprise the same materials as the
amorphous ferromagnetic underlayer 406. A ferromagnetic free layer
414 may be deposited on the amorphous ferromagnetic underlayer 412,
and the ferromagnetic free layer 414 may be amorphous due to the
amorphous structure of the underlayer 412. The amorphous
ferromagnetic free layer 414 may comprise Co, Fe, B, Co, CoFe,
CoFeB, NiFe, CoHf or combinations thereof. Alternatively, the
amorphous ferromagnetic free layer 414 may be made of the same
material as the amorphous ferromagnetic underlayer 412. In one
embodiment, the ferromagnetic free layer 414 is crystalline, and is
deposited directly on the nonmagnetic spacer layer 410. The
crystalline ferromagnetic underlayer 411 and the amorphous
ferromagnetic underlayer 412 may not be present in the stack if the
ferromagnetic free layer 414 is crystalline. Again the amorphous
ferromagnetic reference and free layers 408, 414 enhance
magnetoresistance. A capping layer 416 may be deposited on the
amorphous ferromagnetic free layer 414, and the capping layer 416
may comprise the same materials as the capping layer 312 described
in FIG. 3.
[0046] FIGS. 3 and 4 illustrate simple pinned sensor stacks each
having at least one amorphous ferromagnetic layer. FIGS. 5, 6 and 7
illustrate antiparallel (AP) pinned sensor stacks each having at
least one amorphous ferromagnetic layer. FIG. 5 is a schematic
cross sectional view of a sensor stack 500 according to one
embodiment. The sensor stack 500 may be the sensor stack 234
described in FIG. 2B. The sensor stack 500 may include one or more
seed layers 502, and the one or more seed layers 502 may comprise
the same materials as the one or more seed layers 302 described in
FIG. 3. An antiferromagnetic layer 504 may be deposited on the one
or more seed layers 502, and the antiferromagnetic layer 504 may
comprise the same materials as the antiferromagnetic layer 304
described in FIG. 3.
[0047] A ferromagnetic pinned layer 506 may be deposited on the
antiferromagnetic layer 504. The ferromagnetic pinned layer 506 may
comprise one or more magnetic materials such as, for example NiFe,
CoFe, CoFeB, or diluted magnetic alloys. A nonmagnetic coupling
layer 508 may be deposited on the ferromagnetic pinned layer 506.
The coupling layer 508 may comprise Ru, Cr, Ir, Rh or combinations
thereof. A crystalline ferromagnetic underlayer 509 may be
deposited on the coupling layer 508. The crystalline ferromagnetic
underlayer 509 may comprise the same materials as the crystalline
ferromagnetic underlayer 305 described in FIG. 3. A ferromagnetic
reference layer 510 may be deposited on the crystalline
ferromagnetic underlayer 509. The ferromagnetic reference layer 510
may comprise the same materials as the amorphous ferromagnetic
reference layer 306 and may be deposited by one of the three
methods described above. The amorphous ferromagnetic reference
layer 510 again enhances magnetoresistance.
[0048] A nonmagnetic spacer layer 512 may be deposited on the
amorphous ferromagnetic reference layer 510, and the nonmagnetic
spacer layer 512 may be the nonmagnetic spacer layer 308 described
in FIG. 3. A crystalline ferromagnetic underlayer 513 may be
deposited on the nonmagnetic spacer layer 512, and the crystalline
ferromagnetic underlayer 513 may comprise the same materials as the
crystalline ferromagnetic underlayer 305 described in FIG. 3. A
ferromagnetic free layer 514 may be deposited over the nonmagnetic
spacer layer 512, such as on the crystalline ferromagnetic
underlayer 513. The ferromagnetic free layer 514 may comprise the
same materials as the ferromagnetic free layer 310 described in
FIG. 3, and may be deposited by one of the three methods described
above. In one embodiment, the ferromagnetic free layer 514 is
crystalline, and is deposited directly on the nonmagnetic spacer
layer 512. The crystalline ferromagnetic underlayer 513 may not be
present in the stack if the ferromagnetic free layer 514 is
crystalline. A capping layer 516 may be deposited on the
ferromagnetic free layer 514, and the capping layer 516 may
comprise the same materials as the capping layer 312 described in
FIG. 3.
[0049] FIG. 6 is a schematic cross sectional view of a sensor stack
600 according to one embodiment. The sensor stack 600 may be the
sensor stack 234 described in FIG. 2B. The sensor stack 600 may
include one or more seed layers 602, and the one or more seed
layers 602 may comprise the same material as the one or more seed
layers 302 described in FIG. 3. An antiferromagnetic layer 604 may
be deposited on the one or more seed layers 602, and the
antiferromagnetic layer 604 may comprise the same material as the
antiferromagnetic layer 304 described in FIG. 3. A ferromagnetic
pinned layer 606 may be deposited on the antiferromagnetic layer
604, and the ferromagnetic pinned layer 606 may comprise the same
material as the ferromagnetic pinned layer 506 described in FIG. 5.
A nonmagnetic coupling layer 608 may be deposited on the
ferromagnetic pinned layer 606, and the nonmagnetic coupling layer
608 may comprise the same material as the nonmagnetic coupling
layer 508 described in FIG. 5. A crystalline ferromagnetic
underlayer 609 may be deposited on the coupling layer 608. The
crystalline ferromagnetic underlayer 609 may comprise the same
materials as the crystalline ferromagnetic underlayer 305 described
in FIG. 3.
[0050] An amorphous ferromagnetic underlayer 610 may be deposited
on the crystalline ferromagnetic underlayer 609. The amorphous
ferromagnetic underlayer 610 may comprise the same material as the
amorphous ferromagnetic underlayer 406 described in FIG. 4. A
ferromagnetic reference layer 612 may be deposited on the amorphous
ferromagnetic underlayer 610, and the ferromagnetic reference layer
612 may be amorphous due to the amorphous structure of the
underlayer 610. The ferromagnetic reference layer 612 may comprise
the same material as the amorphous ferromagnetic reference layer
408 described in FIG. 4. A nonmagnetic spacer layer 614 may be
deposited on the amorphous ferromagnetic reference layer 612, and
the nonmagnetic spacer layer 614 may comprise the same material as
the nonmagnetic spacer layer 308 described in FIG. 3. A crystalline
ferromagnetic underlayer 615 may be deposited on the nonmagnetic
spacer layer 614, and the crystalline ferromagnetic underlayer 615
may comprise the same materials as the crystalline ferromagnetic
underlayer 305 described in FIG. 3. A ferromagnetic free layer 616
may be deposited over the nonmagnetic spacer layer 614, such as on
the crystalline ferromagnetic underlayer 615. The ferromagnetic
free layer 616 may be amorphous and comprise the same materials as
the ferromagnetic free layer 310 described in FIG. 3, and may be
deposited by one of the three methods described above. In one
embodiment, the ferromagnetic free layer 616 is crystalline, and is
deposited directly on the nonmagnetic spacer layer 614. The
crystalline ferromagnetic underlayer 615 may not be present in the
stack if the ferromagnetic free layer 616 is crystalline. A capping
layer 618 may be deposited on the ferromagnetic free layer 616, and
the capping layer 618 may comprise the same material as the capping
layer 312 described in FIG. 3.
[0051] FIG. 7 is a schematic cross sectional view of a sensor stack
700 according to one embodiment. The sensor stack 700 may be the
sensor stack 234 described in FIG. 2B. The sensor stack 700 may be
similar to the sensor stack 600, except that the ferromagnetic free
layer 616 shown in FIG. 6 is an amorphous ferromagnetic free layer
704 and an amorphous ferromagnetic underlayer 702 is disposed
between the crystalline ferromagnetic underlayer 615 and the
amorphous ferromagnetic free layer 704. The amorphous ferromagnetic
underlayer 702 may comprise the same materials as the amorphous
ferromagnetic underlayer 610 described in FIG. 6. The amorphous
structure of the underlayer 702 causes the ferromagnetic free layer
704 to be amorphous. Having amorphous reference and free layers
612, 704 enhance magnetoresistance, leading to an improved
sensor.
[0052] In summary, a magnetic head having enhanced
magnetoresistance is disclosed. The enhanced magnetoresistance is
the result of having an amorphous ferromagnetic reference layer.
The ferromagnetic reference layer may be amorphous by certain
deposition methods, or by having an amorphous ferromagnetic
underlayer. The ferromagnetic reference layer is deposited on the
amorphous ferromagnetic underlayer, and the amorphous structure of
the underlayer causes the ferromagnetic reference layer to be
amorphous.
[0053] While the foregoing is directed to embodiments, other and
further embodiments of the disclosure may be devised without
departing from the basic scope thereof, and the scope thereof is
determined by the claims that follow.
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