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Domain wall pinning dependent on nanomagnet state

Reinier van Mourik 1,2 , Charles Rettner 1 , Bert Koopmans 2 , Stuart Parkin 1. 1. IBM Almaden Research Center, San Jose, CA 2. Eindhoven University of Technology, Eindhoven, the Netherlands. Domain wall pinning dependent on nanomagnet state. BB-03.

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Domain wall pinning dependent on nanomagnet state

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  1. Reinier van Mourik1,2, Charles Rettner1, Bert Koopmans2, Stuart Parkin1 1. IBM Almaden Research Center, San Jose, CA2. Eindhoven University of Technology, Eindhoven, the Netherlands Domain wall pinning dependent on nanomagnet state BB-03

  2. Magnetic Domain Walls for memory and logic Introduction Memory Logic • Dynamics of magnetic domain walls important for applications • Precise control of DW position required, for example by pinning Parkin, S. S. P., M. Hayashi, et al. (2008). "Magnetic domain-wall racetrack memory." Science 320(5873): 190-194. Allwood, D. A., G. Xiong, et al. (2005). "Magnetic Domain-Wall Logic." Science 309(5741): 1688-1692.

  3. Outline Introduction • Experimental setup • Domain wall pinned at and depinned from nanomagnet site • Results • Significant difference in depinning field for two nanomagnetstates • Discussion • Domain wall fine structure responsible for difference • Applications • Tunable pinning site or nanomagnet readout • Conclusions DW

  4. Experimental setup Hall bar Domain wall injection line Methods hall bar read • 1. inject DW PMA [CoNi]n nanowire, 60-140nm wide nanomagnetPy 60x90x10nm DW pulser • 3. read resistance change in AMR and Hall bar 2. propagate DW by H field AMR read • AMR and Hall bar register depinning of DW AMR Hall bar Hdep 0 H

  5. Experimental setup Hall bar Domain wall injection line Methods hall bar read • 1. inject DW PMA [CoNi]n nanowire, 60-140nm wide nanomagnetPy 60x90x10nm DW pulser • 3. read resistance change in AMR and Hall bar 2. propagate DW by H field AMR read • Depinning field is measured for both nanomagnet states AMR Hall bar Hdep 0 H

  6. Depinning field difference Results typical result wire width dependence 10 mT! • Magnetic field required to propagate DW past nanomagnet differs by 10 mT for both states. • Depinning field difference increases with wire width.

  7. 1 0.5 0 energy [aJ] -0.5 -1 -1.5 -200 -100 0 100 200 DW position [nm] Micromagnetic energy calculation Discussion top view side view • DW fine structure introduces asymmetric component in energy landscape so is higher in right-magnetized case.

  8. Application potential • Nanomagnet acts as a DW gate if the DW is propagated at a “probe field” Application Hprobe AMR high AMR low AMR high • Application as: • tunable DW pinning site • nanomagnet readout

  9. Domain wall pinning for use in NML readout Application AMR AMR AMR • In NanomagneticLogic, information is propagated along arrays of nanomagnets through magnetostatic coupling. • Output magnet can be read out by DW pinning technique • Each nanomagnet can have its own nanowire. DW injection line Imre, A., G. Csaba, et al. (2006). "Majority logic gate for magnetic quantum-dot cellular automata." Science 311(5758): 205-208.

  10. Conclusion Conclusion • In-plane nanomagnet above PMA nanowire is single-magnet domain wall pinning site where the pinning strength depends on the nanomagnet state. • The depinning field can differ by 10 mT and depends on wire width. • The DW fine structure is responsible for the depinning field asymmetry. • DW pinning can be applied in logic and memory applications. slides & contact: http://tinyurl.com/RvM-IBM

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