1. 1st Berkeley Symposium on Energy Efficient Electronics ● 11 June 2009
Nanomagnetic Logic
Wolfgang Porod
Center for Nano Science and Technology
University of Notre Dame
Supported by NSF, ONR, and SRC-NRI
1st Berkeley Symposium on Energy Efficient Electronics ● 11 June 2009

2. SRC-NRI Funded Centers
Notre Dame Purdue
Illinois-UC Penn State
Michigan UT-Dallas
SUNY-Albany GIT Harvard
Purdue RPI Columbia
Caltech MIT NCSU
Yale UVA
Columbia
Harvard
Purdue
UVA
Yale
UC Santa Barbara
Stanford
U. Mass
U. Arkansas
U. Oklahoma
Notre Dame
U. Nebraska/Lincoln
U. Maryland
Cornell
UT Austin
Caltech
UC Los Angeles
UC Berkeley
UC Irvine
UC Santa Barbara
Stanford
U Denver
Portland State
U Iowa
UT-Austin Rice Texas A&M
UT-Dallas ASU Notre Dame
U. Maryland NCSU Illinois UC 2

4. They posses an inherent high reliability
“Magnetic components are rather attractive to the computer designer for several reasons:
They posses an inherent high reliability
They require in most applications no power other than the power to switch their state
They are potentially able to perform all required operations, i.e., logic, storage and amplification “
H. W. Gschwind, Design of Digital Computers © 1967 by Springer-Verlag.

5. The Elliott 803 computer
The machine was compact (requiring around 400 square feet of floor-space) had undemanding power requirements (3.5 kilowatts plus at least 10 kilowatts of air conditioning) and, most importantly, offered hardware floating point arithmetic as an option, so the Elliott could be used as a low cost scientific machine.
Several aspects of the machine's technology are rather unusual.
Such as, the basic switching technology is built from germanium transistors and a large number of ferrite core logic elements used, not as memory, but as a logic gate. The most common configuration is illustrated below.

6. Quantum-Dot Cellular Automata
A Quantum-Dot Cell
Represent binary information by charge configuration
2 extra electrons
A cell with 4 dots
An Array of Cells
Neighboring cells tend to align due to direct
Coulombic coupling

7. Programmable 2-input AND or OR gate.
QCA Devices -1 1
Binary wire
Majority gate -1 1 1 -1
Inverter M A B C A B C
Out
Programmable 2-input AND or OR gate.

8. From metal-dot to molecular QCA
Metal tunnel junctions
“dot” = metal island
70 mK
Mixed valence compounds
“dot” = redox center
Metal-dot QCA established proof-of-principle.
but …low T, fabrication variations
Molecular QCA: room temp, synthetic consistency
room temperature+

9. First room temperature magnetic “quantum-dot cellular automata”
The circular dots, each of diameter 110 nm, placed on a pitch of 135 nm. The dots were 10 nm thick and were made from the common magnetic alloy supermalloy (Ni80Fe14Mo5X1, where X is other metals) by e-beam lithography and lift-off.
Evolution of a soliton propagating along a chain of coupled nanomagnets under the action of a 30Oe field applied:
R.P. Cowburn and M.E. Welland SCIENCE, VOLUME 287, 1466 (2000)
R.P. Cowburn JOURN MAGNETISM MAGNETIC MAT, VOLUME 242, 505 (2002)

10. Coupled Nanomagnets Strong Coupling Stable Patterns
Magnetostatic energy
Strong Coupling Stable Patterns

11. Gary H. Bernstein, Alexandra Imre, Zhou Ling, George Csaba
Observe Magnetic Field Coupling
Atomic-Force and Magnetic-Force Microscopy
(AFM and MFM)
Gary H. Bernstein, Alexandra Imre, Zhou Ling, George Csaba

12. Approx. 36 µm

13. Magnetite Biomineralization
Biomineralization in Magnetotactic Bacteria
Bob Kopp, 2001
Joseph L Kirschvink et al.

14. Experimental demonstration of antiferromagnetic ordering
SEM
AFM
MFM
16 dots long chain contains 30 nm thick permalloy nanomagnets made by e-beam lithography and lift-off

15. Experimental demonstration of ferromagnetic ordering with input
AFM
MFM H
16 dots long chain contains 30 nm thick permalloy nanomagnets made by EBL and lift-off

18. Majority gate geometry
M.C.B. Parish and M. Forshaw, APPL. PHYS. LETT. 83, 2046 (2003)
A different version off the majority “cross” geometry was proposed by

19. Demonstration of majority gate operation
A. Imre et al, SCIENCE, VOL. 311, 205 (2006)

21. Proposed Drive Circuitry
1 wire controls 1000s of magnets

22. We add 25% energy overhead per wire to estimate
Aggregate Energy
Sources of Energy
1. Hysteresis loss in magnets
2. Cu wire resistance, parasitics
3. Clock generation circuitry (not shown)
Nanomagnet Studies
G. Csaba, J. of Comp. Elec., vol. 4(1/2), pp. 105–11, 2005.
1010 magnets switch 108 times/s, ~ 0.1 W
Clock Wire Studies
Niemier, et. al., “Clocking structures and power analysis for nanomagnet-based logic devices,” ISLPED, pp. 26–31, 2007.
Hclock is a function of current density
Greater J [ > Hclock [ > I [ > P (as a function of I2)
Should be most significant energy
consumer in a computation
Wire Drivers
We add 25% energy overhead per wire to estimate

23. Energy Delay Product (EDP) Estimates
EDP Estimate for 32-bit CMOS Ripple Carry Adder
Magnets with feature sizes can outperform CMOS equivalents in EDP
Can also investigate materials to increase relative permeability
Pierambaram, “Enhanced Permeability Device Structures and Methods”, Dec. 17, 2007, US Patent Application US 2007/ A1
Scaling should further reduce MQCA EDP

24. Thanks to … Magnetic QCA Sponsors
Edit Varga and Tanvir Alam (NDnano) … Fabrication and MFM
Alexandra Imre (ANL) … Fabrication and MFM
George Csaba and Paolo Lugli (TUM) … Theory and Modeling
Gary Bernstein and Alexei Orlov (NDnano) … Fabrication and Testing
Michael Niemier and Sharon Hu (NDnano) … Architectures
Sponsors
Office of Naval Research
National Science Foundation
Semiconductor Research Corporation