1. Data Storage and Nanomagnets
Magnetic Memory:
Data Storage and Nanomagnets
Mark Tuominen
Professor of Physics

2. Data Storage. Example: Advancement of the iPod
Review
Data Storage. Example: Advancement of the iPod
10 GB
2001
20 GB
2002
40 GB
2004
80 GB
2006
160 GB
2007
Hard drive
Magnetic data storage
Uses nanotechnology!

3. Ferromagnet uniform magnetization Bistable: Equivalent energy for
Electron magnetic moments ("spins")
Aligned by
"exchange interaction"
anisotropy axis
("easy" axis)
It is always useful to start the introduction with something simple such that anyone could get something out of the talk. This page introduces the concept of a single-domain nanomagnet as a basic element for data storage. Note that the animation helps to tell the story in a linear and logical way. Please add actual diagrams of the double well for the three fields shown.
Bistable:
Equivalent
energy for
"up" or "down"
states

4. 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 Mz H
hysteresis curve
“topview”
shorthand
switching field
E = K1sin2•H
It is always useful to start the introduction with something simple such that anyone could get something out of the talk. This page introduces the concept of a single-domain nanomagnet as a basic element for data storage. Note that the animation helps to tell the story in a linear and logical way. Please add actual diagrams of the double well for the three fields shown.
Bistable. Ideal for storing data - in principle, even one nanomagnet per bit.

5. Ferromagnet with unknown
Ferromagnets are used to store data
Current N S
‘0’ ?
Ferromagnet with unknown
magnetic state S
Current N
‘1’

6. Magnetic Data Storage
A computer hard drive stores your data magnetically
“Read”
Head
Signal
“Write”
Head
current S N
Disk N S 1 _
“Bits” of
information
direction of disk motion

7. 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.

8. Improving Magnetic Data Storage Technology
The UMass Amherst Center for Hierarchical Manufacturing is working to improve this technology
Granular Media
Perpendicular
Write Head
Soft Magnetic UnderLayer (SUL)
coil
1 bit
Y. Sonobe, et al., JMMM (2006)
• CHM Goal: Make "perfect" media
using self-assembled nano-templates
• Also, making new designs for storage

9. Filling the Template: Making Cobalt Nanorods by Electrochemical DepositionWE
REF
electrolyte CE
For the published part of our results, we chose another approach to electrodeposite the Co magnetic cluster for our experiments. This procedure had been studied thougrhtouly by my colleague Dr. Ursache in our lab. The deposition electrolyte is carefully tuned to pH6, And we used PRECD. the voltage we applied to the working electrode in the potentialstat ECD cell can be timed to two phases. Each of the repeating phases is 10 ms long. In the pulse phase, the voltage we put on the working electrode is 1 V to the standard reference electrode. The Co atoms are deposited into the pattern. But not all of the Co atoms can land on the perfect crystal lattice points. During the reverse cycle, the voltage we put on the working electrode is 0.35 V. This will remove the loosely bonded Co atoms back into the solution.
metal

10. Binary Representation of Data
only 2 choices
one bit
“1” or “0”
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

11. Binary representation of lower case letters
5-bit "Super Scientist" code:
ex: k = 01011 1 S N OR
(Coding Activity: Use attractive and repulsive forces to "read" the magnetic data!)

12. NEW! Multi-State Representation of Data
"CLUSTERS"
“Read”
Head
“Write”
Head 1 2 3
Disk 1 3 2 = = 1
direction of disk motion

13. (Magnetic Force Microscope)
3-Nanomagnet Cluster
Imaged with a MFM
(Magnetic Force Microscope)
M = -3
M = -1
M = +1
M = +3
Accomplished in the CHM!

14. "Multi-state" representation
of lower case letters 1 2 3
What is the word?
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