magnetic memory: data storage and nanomagnets
DESCRIPTION
Magnetic Memory: Data Storage and Nanomagnets. Mark Tuominen Professor of Physics. 20 GB. 40 GB. 10 GB. 2001. 2002. 2004. Hard drive Magnetic data storage. 80 GB. 160 GB. 2006. 2007. Review. Data Storage. Example: Advancement of the iPod. Uses nanotechnology!. anisotropy axis - PowerPoint PPT PresentationTRANSCRIPT
Magnetic Memory:Data Storage and Nanomagnets
Mark Tuominen Professor of Physics
10 GB2001
20 GB2002
40 GB2004
80 GB2006
160 GB2007
Data Storage. Example: Advancement of the iPod
Hard driveMagnetic data storage
Uses nanotechnology!
Review
Ferromagnetuniform magnetization
anisotropy axis("easy" axis)
Electron magnetic moments ("spins")
Aligned by "exchange interaction"
Bistable:Equivalentenergy for "up" or "down"states
Ferromagnets are used to store data
?
Ferromagnet with unknown magnetic state
Current
N
S‘0’
S
Current
N‘1’
Magnetic Data StorageA computer hard drive stores your data magnetically
Disk
N S
direction of disk motion
“ Write”Head
0 0 1 0 1 0 0 1 1 0 _ _
“ Bits” ofinformation
NS
“ Read”Head
Signalcurrent
Scaling Down to the Nanoscale
Increases the amount of data stored on a fixed amount of “real estate” !
Now ~ 100 billion bits/in2, future target more than 1 trillion bits/in2
25 DVDs on a disk the size of a quarter.
Improving Magnetic Data Storage Technology
• The UMass Amherst Center for Hierarchical Manufacturing is working to improve this technology
Granular Media
PerpendicularWrite Head
Soft Magnetic UnderLayer (SUL)
coil
Y. Sonobe, et al., JMMM (2006)
1 bit
• CHM Goal: Make "perfect" mediausing self-assembled nano-templates• Also, making new designs for storage
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Filling the Template: Making Cobalt Nanorods by Electrochemical
Deposition
WE REF
electrolyte
CE
Co2+
Co
metal
Binary Representation of Data
one bit “ 1” or “0” only 2 choices
two bits 00, 01, 10, 11 4 choices
three bits 000, 001, 010, 011,100, 101, 110, 111 8 choices
n bits has 2n choices
For example, 5 bits has 25 = 32 choices...more than enough to represent all the letters of the alphabet
Character "SS"codea 00001b 00010c 00011d 00100e 00101f 00110g 00111h 01000i 01001j 01010k 01011l 01100
m 01101n 01110o 01111p 10000q 10001r 10010s 10011t 10100u 10101v 10110w 10111x 11000y 11001z 11010
Binary representationof lower case letters
5-bit "Super Scientist" code: ex: k = 01011
0 1 0 1 1
S
N
S
N
S
N
N
S
N
SOR
(Coding Activity: Use attractive and repulsive forces to "read" the magnetic data!)
NEW! Multi-State Representation of Data
Disk
“ Write”Head
“ Read”Head
= =0 1
direction of disk motion
1 0 3 2
0
123
"CLUSTERS"
M = -3 M = -1 M = +1 M = +3
3-Nanomagnet ClusterImaged with a MFM
(Magnetic Force Microscope)
Just accomplished summer 2007 in the CHM!
Character "SS"codea 001b 002c 003d 010e 011f 012g 013h 020i 021j 022k 023l 030
m 031n 032o 033p 100q 101r 102s 103t 110u 111v 112w 113x 120y 121z 122
"Multi-state" representationof lower case letters
— — — — — —
10 32
What is the word?
The Bistable Magnetization of a Nanomagnet• A single-domain nanomagnet with a
single “easy axis” (uniaxial anisotropy) has two stable magnetization states
“topview”shorthand
zor H
Mz Mz
Mz
H
Bistable. Ideal for storing data - in principle, even one nanomagnet per bit.
hysteresis curve
E = K1sin2•H switching field