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Emerging Technologies of Computation

Emerging Technologies of Computation. Montek Singh COMP790-084 Sep 6, 2011. Today: Magnetic Quantum Dot Cellular Automata (MQCA). Basics of magnetism Nanomagnets and their coupling Next class: Challenges and Benefits Open questions. Basics of magnetism. Magnetic domains

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Emerging Technologies of Computation

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  1. Emerging Technologies of Computation Montek Singh COMP790-084 Sep 6, 2011

  2. Today: Magnetic Quantum Dot Cellular Automata (MQCA) • Basics of magnetism • Nanomagnets and their coupling • Next class: • Challenges and Benefits • Open questions

  3. Basics of magnetism • Magnetic domains • regions within magnetic material with uniform magnetization… • … separated by “domain walls” • magnetic moments all exactly aligned • responsible for magnetic behavior of “ferromagnetic” materials: iron, nickel, etc. • What causes them? • magneto-static energy is minimized • Other energy terms: • magnetoelastic anisotropy • magnetocrystalline anisotropy • Zeeman energy Magnetic domains

  4. Basics of magnetism • Magnetic domains • more domains reduces magnetostatic energy • but increases wall energy • Single Domain (SD) • 10 to 100nm is a good size

  5. Basics of magnetism • Magnetization • … under externally applied magnetic field (H) • domains change shape and magnetic moments re-orient • walls shift or disappear • even physical shape of material can change somewhat! • called magnetostriction • useful in actuators and sensors • in strong enough field, all domains aligned • minimizes Zeeman energy

  6. Basics of magnetism • Shape-induced magnetic anisotropy • long grains tend to have magnetic moments along the longer dimension • magnetized grain produces internal magnetic field that counters external field • internal field is anisotropic • Magnetization axis can be determined by fabricated shape • gives us two states! • comes in handy for magnetic storage!

  7. Nanomagnets

  8. Nanomagnets • Two types of coupling • ferromagnetically ordered coupling • collinear along the long axes • states line up • antiferromagnetically ordered coupling • side-by-side, in parallel • favors antiparallel: up-down-up-down…

  9. MQCA: majority gate

  10. MQCA: majority gate

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