First observation of ferromagnetic order in an artificial 2D quasicrystal

ORAL

Abstract

Magnetic order in bulk quasicrystals is not well understood and known materials exhibit short-range, spin-glass order. We patterned ferromagnetic (FM) thin films into artificial quasicrystals, a new class of metamaterials that exhibits complex magnetic reversal and dynamics that can be controlled via tiling design.\footnote{V.S. Bhat\textit{, et al.} \textit{Phys. Rev. Lett.} \textbf{111}, 077201 (2013).} We analyzed two-dimensional SEMPA images of magnetization textures of Penrose P2 tilings (P2T) patterned into Permalloy. The diverse, asymmetric vertex coordinations drive novel, \textit{non-stochastic switching} and \textit{complex spin-ice} behaviors that reflect the influence of vertex domain wall energies. Monte Carlo and OOMMF simulation analyses of SEMPA images of slowly grown, never-field-cycled P2T reveal low energy, long-range ordered sublattices that form building blocks of a ground state. A fully ordered ground state is unresolved without long-range dipolar interactions that stabilize a magnetically ordered state with a net moment. Our P2T constitute a set of quasicrystalline metamaterials in which frustration and magnetic order among classical Ising spins can be directly studied.

*Kentucky research supported by U.S. DoE Grant DE-FG02-97ER45653 and NSF Grant EPS-0814194. ALB acknowledges support under the Cooperative Research Agreement between the University of Maryland and NIST.

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Authors

  • Barry Farmer

    • University of Kentucky
    • University of Kentucky, Department of Physics and Astronomy

  • Vinayak Bhat

    • University of Kentucky, Department of Physics and Astronomy

  • Andrew Balk

    • Center for Nanoscale Science and Technology, NIST
    • Center for Nanoscale Science and Technology, National Institute of Standards and Technology
    • Center for Nanoscale Science and Technology, National Institute of Standards and Technology. Maryland Nanocenter, University of Maryland

  • John Unguris

    • Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899
    • Center for Nanoscale Science and Technology, NIST
    • Center for Nanoscale Science and Technology, National Institute of Standards and Technology
    • Center for Nanoscale Science and Technology, National Institute of Standards and Technology.

  • L.E. DeLong

    • University of Kentucky
    • University of Kentucky, Department of Physics and Astronomy
    • Center for Advanced Materials, Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA