Speaker
Description
Since the discovery of quasicrystals, the effect of aperiodicity on fundamental physical phenomena has been pursued with great interest [1,2]. Using material-by-design approach and X-ray photoemission electron microscopy imaging, we studied magnetization reversal in aperiodic Penrose P3, P2, and Ammann quasicrystal lattices. The planar artificial quasicrystals consisted of ferromagnetic Ni81Fe19 nanobars of width 120 nm and thickness 25 nm. The systematic variation of exchange and dipolar interactions is achieved by keeping the intervertex spacing fixed at 810 nm, but varying the length of nanobars between 408 and 810 nm. The aperiodicity introduces both peculiar arrangements of high and low-energy magnetization configurations of nanobars as well as geometrical frustration; therefore, quasicrystals are considered for reprogrammable magnonics. Analysis of magnetization reversal in terms of nanobar reversal, charge model, and flux-closure loops, combined with micromagnetic simulations demonstrate how the variation of exchange and dipolar interactions leads to a transition from non-stochastic to stochastic switching, and to the pronounced violation of local spin ice rules in the quasicrystalline tilings. Our study indicates that aperiodicity in quasicrystal tilings gives rise to novel class of aperiodic magnonic crystals that can be reprogrammed by a global magnetic field in a better way compared to their periodic counterpart.
Acknowledgements
Research supported by SNSF via grant number 163016 and HZB, Germany.
References:
[1] A. I. Goldman et al., Nat. Mater. 12, 714 (2013).
[2] V. S. Bhat et al., Phys. Rev. Lett. 111, 077201 (2013).
