The Role of the Demagnetizing Fields in the Transition from Thin Films to Magnonic Crystals


The Role of the Demagnetizing Fields in the Transition from Thin Films to Magnonic Crystals

Lenz, K.; Langer, M.; Röder, F.; Gallardo, R. A.; Schneider, T.; Stienen, S.; Gatel, C.; Hübner, R.; Lindner, J.; Landeros, P.; Fassbender, J.

The transition from a film to a full magnonic crystal is studied by sequentially ion-milling a periodic stripe pattern into a 40 nm thick Ni$_{80}$Fe$_{20}$ film. The spin-wave resonances of each milling stage are detected by ferromagnetic resonance for both in-plain main field axes, i.e. parallel and perpendicular to the stripe pattern. Theoretical calculations and micromagnetic simulations yield the individual mode profiles, which are analyzed in order to track changes of the mode character. The latter is strongly linked to the evolution of the internal demagnetizing field. It’s role is further studied and imaged by electron holography measurements on a hybrid magnonic crystal, which is made with a 10 nm deep surface modulation. The complex effects of mode coupling, mode localization, and anisotropy-like contributions by the internal field are unraveled. Simple transition rules from the $𝑛^_\mathrm{th}$ film mode to the $𝑚\mathrm{th}$ mode of the full magnonic crystal are formulated.
This work has been supported by DFG grant KL2443/5-1.

Keywords: Ferromagnetic resonance; magnonic crystals; demagnetizing fields

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Publ.-Id: 26618