Zero-field propagation of spin waves in waveguides prepared by focused ion beam direct writing

L. Flajšman, K. Wagner, M. Vaňatka, J. Gloss, V. Křižáková, M. Schmid, H. Schultheiss, M. Urbánek

CEITEC BUT, Brno University of Technology, 61200 Brno, Czech Republic
Institute of Ion Beam Physics and Materials Research, HZDR, 01328 Dresden, Germany
Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Institute of Physical Engineering, Brno University of Technology, 61669 Brno, Czech Republic

Phys. Rev. B 101 (2020) 014436

Metastable face-centered-cubic Fe78Ni22 thin films are excellent candidates for focused ion beam direct writing of magnonic structures due to their favorable magnetic properties after ion-beam-induced transformation. The focused ion beam transforms the originally nonmagnetic fcc phase into the ferromagnetic bcc phase with additional control over the direction of uniaxial magnetic in-plane anisotropy and saturation magnetization. Local magnetic anisotropy direction control eliminates the need for external magnetic fields, paving the way towards complex magnonic circuits with waveguides pointing in different directions. In the present study, we show that the magnetocrystalline anisotropy in transformed areas is strong enough to stabilize the magnetization in the direction perpendicular to the long axis of narrow waveguides. Therefore, it is possible to propagate spin waves in these waveguides in the favorable Damon-Eshbach geometry without the presence of any external magnetic field. Phase-resolved microfocused Brillouin light scattering yields the dispersion relation of these waveguides in zero as well as in nonzero external magnetic fields.

Corresponding authors: Lukáš Flajšman and Michal Urbánek. Reprints also available from Michael Schmid (schmid at iap_tuwien_ac_at).

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A preprint is available at arxiv.org.