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Magnetic Memory: Data Storage and Nanomagnets

Magnetic Memory: Data Storage and Nanomagnets. Mark Tuominen Professor of Physics. 20 GB. 40 GB. 10 GB. 2001. 2002. 2004. Hard drive Magnetic data storage. 80 GB. 160 GB. 2006. 2007. Review. Data Storage. Example: Advancement of the iPod. Uses nanotechnology!. anisotropy axis

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Magnetic Memory: Data Storage and Nanomagnets

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

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

  3. anisotropy axis ("easy" axis) Ferromagnet uniform magnetization • Electron magnetic moments ("spins") • Aligned by • "exchange interaction" Bistable: Equivalent energy for "up" or "down" states

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

  5. “Read” Head Signal 0 0 1 0 1 0 0 1 1 0 _ _ “Bits” of information Magnetic Data Storage A computer hard drive stores your data magnetically “Write” Head current S N Disk N S direction of disk motion

  6. 25 DVDs on a disk the size of a quarter. 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

  7. coil Perpendicular Write Head Granular Media Soft Magnetic UnderLayer (SUL) • CHM Goal: Make "perfect" media using self-assembled nano-templates • Also, making new designs for storage 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)

  8. electrolyte CE WE REF Co2+ Co Filling the Template: Making Cobalt Nanorods by Electrochemical Deposition metal

  9. 4 choices two bits 00, 01, 10, 11 000, 001, 010, 011, 100, 101, 110, 111 three bits 8 choices 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

  10. Binary representation of lower case letters N N 1 0 0 1 1 5-bit "Super Scientist" code: ex: k = 01011 OR N N S S N S S S (Coding Activity: Use attractive and repulsive forces to "read" the magnetic data!)

  11. “Read” Head 3 2 1 0 NEW! Multi-State Representation of Data "CLUSTERS" “Write” Head Disk 1 0 3 2 = = 1 0 direction of disk motion

  12. 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!

  13. "Multi-state" representation of lower case letters — — — — — — 0 1 2 3 What is the word?

  14. Mz H 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.

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