Magnetic Memory:

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Magnetic Memory Data Storage and Nanomagnets
Mark Tuominen Professor of Physics
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Review
Data Storage. Example Advancement of the iPod
Uses nanotechnology!
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Ferromagnet
uniform magnetization

• Electron magnetic moments ("spins")
• Aligned by
• "exchange interaction"

Bistable Equivalent energy for "up" or
"down" states
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Ferromagnets are used to store data
?
Ferromagnet with unknown magnetic state
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Magnetic Data Storage
A computer hard drive stores your data
magnetically
Write Head
current
N
S
Disk
N
S
direction of disk motion
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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
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Improving Magnetic Data Storage Technology

• The UMass Amherst Center for Hierarchical
  Manufacturing is working to improve this
  technology

1 bit
Y. Sonobe, et al., JMMM (2006)
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Filling the Template Making Cobalt Nanorods by
Electrochemical Deposition
metal
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Binary Representation of Data
only 2 choices
one bit
1 or 0
n bits has 2n choices
For example, 5 bits has 25 32 choices... more
than enough to represent all the letters of the
alphabet
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Binary representation of lower case letters
5-bit "Super Scientist" code ex k
01011
OR
N
N
N
S
S
S
S
S
(Coding Activity Use attractive and repulsive
forces to "read" the magnetic data!)
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NEW! Multi-State Representation of Data
"CLUSTERS"
Write Head
Disk
1
0
3
2


1
0
direction of disk motion
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3-Nanomagnet Cluster Imaged with a MFM (Magnetic
Force Microscope)
M -3
M -1
M 1
M 3
Just accomplished summer 2007 in the CHM!
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"Multi-state" representation of lower case letters
1
0
3
2
What is the word?
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The Bistable Magnetization of a Nanomagnet
A single-domain nanomagnet with a single easy
axis (uniaxial anisotropy) has two stable
magnetization states
Mz
Mz
z
or
H
hysteresis curve
topview shorthand
switching field
E K1sin2????H?
Bistable. Ideal for storing data - in principle,
even one nanomagnet per bit.