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

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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.

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.

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

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.

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+

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)

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

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

Approx. 36 µm

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

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

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

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

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

Proposed Drive Circuitry 1 wire controls 1000s of magnets

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

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 2007/0284683 A1 Scaling should further reduce MQCA EDP

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