Transcript Presentation Title Arial Bold 36pt

Future Materials Research in
Data Storage
NSF Workshop on Cyberinfrastructure for
Materials Science
Mark H. Kryder
CTO and Sr. Vice President, Research, Seagate
Technology
University Professor, Carnegie Mellon University
Outline
 Recording Overview
 Materials Problems in Future Recording Technologies
 Perpendicular Recording
 Heat Assisted Magnetic Recording
 Bit Patterned Media
 TGMR/GMR Readers
 Multiferroics
 Discussion of Modeling Needs
Mark H. Kryder
NSF Workshop 08-06
Page 2
Disc Drives Today Cover the Widest Range of Users and
Systems Ever
Handheld
Gaming
12 GB
DVR
750 GB
Notebook
Desktop
Enterprise
160 GB 750 GB 73 GB 300 GB 750 GB
Low-cost, high-capcity, disk drives are enabling new devices,
resulting in rapid growth of the storage industry and the
emergence of new industries. e.g. Apple iPod, PVR’s, X-Box,
automobile navigation systems, digital video cameras, etc.
Mark H. Kryder
NSF Workshop 08-06
Page 3
Areal Density Growth
100000
Single particle
superparamagnetic limit
(estimated)
10000
HAMR
Mark H. Kryder
NSF Workshop 08-06
100
10
Charap’s limit
(broken)
• Areal Density CAGR 40%
• Transfer Rate CAGR 20%
1
year
Page 4
19
20
17
20
15
20
13
20
11
20
09
20
07
20
05
20
03
20
01
20
99
19
97
19
93
95
19
19
91
0.1
89
• Additional
innovations
required at that
point
• heat-assisted
recording (HAMR)
• bit patterned
media (BPM)
recording
Perpendicular
19
• Perpendicular
expected to extend
to 0.5-1 Tb/in2
HAMR+
BPM
1000
gigabit / in2
• Longitudinal
recording reaching
areal density limits
19
• Late 1990s – super
paramagnetic limit
demonstrated
through modeling
Longitudinal
Recording
Perpendicular
Recording
Magnetic domains oriented in the
direction of travel of the head.
Soft underlayer “mirrors” write
head and makes it possible to
write domains much closer
together.
Mark H. Kryder
NSF Workshop 08-06
Page 5
Magnetic Media Evolution
Physical grain size below 10 nm
0.25
2
normalized frequency
0.2
2
2
45 Gbit/in
24 Gbit/in
16 Gbit/in
9 nm mean size
Std. Dev. 2.2nm
10 nm mean size
11 nm mean size
20nm
2
0.15
100 Gbit/in
9.1 nm mean size
Std. Dev. 1.7nm
2
10 Gbit/in
0.1
12 nm mean size
2
6 Gbit/in
0.05
15 nm mean size
0
0
5
10
15
20
25
30
grain size (nm)
Mark H. Kryder
NSF Workshop 08-06
Page 6
35
HAMR can theoretically extend areal density beyond 10 Tbpsi
Mark H. Kryder
NSF Workshop 08-06
Page 7
HAMR Potential

Increased resolution with
cross- and in-track
thermal gradient recording
HAMR freezing dynamics
allowing more
intergranular exchange
and unique composite
media designs.
1000
CoPt
YCo5
10 nm
800
600
Fe14Nd2B
MnAl
400
Co/Pt
FePd
Co3Pt CoPt3
Co/Pd
CoCrPt
200
0
0
2
10× AD gain potential
with FePt
6
4
7
3
Ku (10 erg/cm )
Dieter Weller
Mark H. Kryder
NSF Workshop 08-06
FePt
2

Ability to record on media
with anisotropy beyond
writability with current
perpendicular recording
technology
AD ~ 1/Dp (arb units)

SmCo5
Page 8
8
HAMR Head Disc Interface Material Needs
• Media Overcoat (< 2 nm) and Lubricant must be able to
withstand the repeated exposure to the high writing
temperature.
120mJ/cm2
• New media overcoat materials will be needed.
• Carbon overcoat can be damaged and/or graphitized at
much lower temperature than its 560°C oxidation
temperature.
Media DLC is removed
5.0
Zdol 2000
Lubricant 1
Lubricant 2
100
4.0
80
Weight (%)
Anisotropy (10^7 erg/cc)
• New Disc Lubricant materials will be required.
3.0
60
40
20
2.0
0
In Air
10 K/min heating rate
0
1.0
0.0
400
100 200 300 400 500 600 700 800 900
Temperature (Degree C)
HDI
500
600
700
800
Curie Temperature (K)
Mark H. Kryder
NSF Workshop 08-06
Page 9
Bit Patterned Media
Lithography vs. Self Organization
Lithographically Defined
FePt Self-Organizing Media
“9 Tb/in2“
6 nm FePt particles
Direct E-Beam Write or Di-Block Co-Polymer
Major obstacle is finding low cost means of
making media
• At 1 Tbpsi, assuming a square bit cell and
equal lines and spaces, 12.5 nm lithography
would be required
• Semiconductor Industry Association roadmap
does not provide such linewidths within the
next decade
Mark H. Kryder
NSF Workshop 08-06
Idea:
Use Pattern Assisted Assembly to
establish circumferential tracks on discs
Page 10
Di-Block Co-polymer Template
Block-copolymers form naturally ordered nano-structures
Lo
A
•
•
•
•
•
A-B block copolymer
precursor
substrate
B
control of vertical orientation on any substrate
improve long-range order and uniformity
selective removability of one component
reduce L0 without losing uniformity, order
use of “environmentally safe” chemicals
Mark H. Kryder
NSF Workshop 08-06
Guiding patterns
can provide long
range order
• controlled 2D alignment to
guiding patterns
• balance polymer-interface vs
polymer-substrate interactions
Use as a template for pattern transfer
• additive process (fill in holes by plating):
- ensure open contact to metal substrate
- ensure all pores get filled equally
• subtractive process (transfer down by RIE):
- etching requires high etch-resistive resist
Page 11
Self Organized Magnetic Array Media
Dp: smallest possible thermally
stable magnetic grain core size!
Exam ples of som e
h=20nm
Uniaxial Ferrom agnetic Materials
7
Kux10
Material
S. Sun, Ch. Murray, D.
Weller, L. Folks, A. Moser,
Science 287, 1989 (2000).
Solvent
Evaporation
(ergs/cc)
Ms
Tc
(emu/cc)
(K)
Vp
3
Sphere
Cylinder
CoCrPt
Dp
Dp
Dp
Dp
(kOe)
(nm )
(nm)
(nm)
(nm)
(nm)
0.3
330
18.2
966
9.9
12.3
7.8
11.1
Co3Pt
2
1100
36.4
145
5.3
6.5
3.0
4.3
CoPt3
0.5
300
600
33.3
580
8.3
10.3
6.1
8.6
Co
0.45
1422
1393
6.3
644
8.6
10.7
6.4
9.1
#DIV/0!
#DIV/0!
#DIV/0!
Co2/Pt9
1
360
500
55.6
290
6.6
8.2
4.3
6.1
Co2/Pd9
0.6
360
500
33.3
483
7.8
9.7
5.5
7.8
#DIV/0!
#DIV/0!
#DIV/0!
#DIV/0!
L10
#DIV/0!
#DIV/0! #DIV/0!
#DIV/0! #DIV/0!
FePd
1.8
1100
760
32.7
161
5.4
6.7
3.2
4.5
FePt
6.6
1140
750
115.8
44
3.5
4.4
1.7
2.4
CoPt
4.9
800
840
122.5
59
3.9
4.8
1.9
2.7
#DIV/0!
#DIV/0!
#DIV/0!
Rare Earth
#DIV/0!
#DIV/0! #DIV/0!
Fe14Nd2B
4.6
1270
585
72.4
63
4.0
4.9
2.0
2.8
SmCo5
20
910
1000
439.6
14
2.4
3.0
1.0
1.4
Important Research Topics:
• Particle Size and Distribution Control
• Eliminate Sintering / Coarsening during
anneal e.g. FCC-FCT (A1 – L10) Phase
Transformation
• Magnetic Easy Axis Orientation
• Registered Large Scale Assembly
• Packing density
• Tribology
Mark H. Kryder
NSF Workshop 08-06
Cylinder
Co hcp alloy
Multilayer
e.g. 6 nm FePt particles
1 particle/bit~“9 Tb/in2“
Hk
h=10nm
Cube
Page 12
TGMR/GMR Reader
Materials
Reader Development Approaches
 Alternate Barrier TGMR
(MgO)
Sensitivity (slope)
 Improved amplitude, and lower
RA
 Potential to extend TGMR reader
to area density
 Current problem – Maintaining
soft magnetic property
of free layer, while keeping high
DR/R and low RA.
Output
Voltage
 CCP Design (current confined
path)
Flux from the media rotates reader free
layer magnetization thus changing spin
polarized electron tunneling conduction.
Top Shield
FL
FL-RL is determined by TMR
Tunneling
Barrier
RL
FL
Magnet
FL
Magnet
AFM/SAF/RL
Current
Electron
Flow
Flow
Insulator
Bottom Shield
Linear
Range
Operate in the
linear range of
transfer function.
Media
Field
FL-RL
 A discontinuous oxide buried in
metal
 Higher DR/R and RA as
compared to CPP Spin Value
 Potential to use for area density of
400~ 600Gb/In2.
 Current problem – Reducing
variation of RA, and DR/R,
and increasing DR/R.
 CPP Spin Valve With Metal or
Half Metal Spacer
 Could offer better reliability, and
SNR at very high KTPI
 Potential to use for area density
of 600Gb/In2 and behind
 Current problem – Concept not
proven, and processing half
metals at temperature magnetic
head can tolerate difficult
Mark H. Kryder
NSF Workshop 08-06
Page 13
Free Layer
MgO
Ref. Layer
Ru
Pinned Layer
AFM
Free Layer
Ref. Layer
Ru
Pinned Layer
AFM
Free Layer
Cu
Ref. Layer
Ru
Pinned Layer
AFM
Multiferroic Data Storage System
 Readback is difficult from PE media, due to free charges, but not from FM media.
 Generating enough magnetic field to write to thermally stable FM media is difficult.
 An electric field can be used to assist writing by by using a media that is both PE and FM
(Multiferroic). The data could then be read back using an MR head.
 Both single phase and multiferroic materials exist, but composite materials are most
interesting due to their higher transition temperatures (both PE & FM above RT).
• A composite material is achieved by combining MS and PE materials [ex. BiFeO3CoFe2O4 or BaTiO3-CoFe2O4]. An electric field applied to the composite will induce
strain in the PE constituent which is passed along to the MS constituent, where it
induces a change in the magnetic anisotropy.
Diagram of an Example Recording System
V+
P
M
P
P
M
I
V+
P
P
M
V-
VMark H. Kryder
NSF Workshop 08-06
P
P
Page 14
M
P
Computing Needs in Magnetic Recording
Technology







Micromagnetic models of media structure with 3-10 nm grain size
and variable exchange coupling at the grain boundaries that allow us
to understand the recording of 10’s to 1000’s of bits involving 50-100
grains each.
Models which enable prediction of magnetic materials properties and
processes for making them that enable growth of materials with
variable grain sizes, variable magnetic parameters, and variable
exchange coupling across grain boundaries.
Models of tribological properties of thin film (<2 nm) materials.
Models of self organization in diblock copolymers and in magnetic
nanoparticle arrays.
Predictions of improved giant and tunneling magnetoresistive
materials.
Predictions and understanding of multiferroic materials.
NUMEROUS OTHERS!!
Mark H. Kryder
NSF Workshop 08-06
Page 15