Footprints of the specific artificial spin ice microstate on the dynamic properties of its spin waves

We show the results of micromagnetic simulations, where the dynamic properties of the spin wave (SW) resonances (at zero wavevector) in an artificial spin ice (ASI) are studied as a function of the magnetic microstate at remanence (H=0). In particular, we select a few microstates with specific magnetic charge at an ASI vertex (including a flux-closure vortex one), and, after calculations by Fourier analysis, look to the corresponding spin wave spectrum and spin wavefunction profiles [1]. We discuss: (1) the modification of the nodal lines as a function of the macrospin separation and width, recognizing the phase-shift peculiar to the magnetic charge at vertex (Fig. 1); (2) the frequency gap between the edge mode and the fundamental mode; (3) the role of macrospin density in the array, as well as the macrospin width; (4) the role of the absolute size of a macrospin (in units of the exchange length) in determining how rich of modes (and peaks) is the spectrum [2]. We suggest a few experimental techniques (micro-focused Brillouin light scattering [3], X-ray microscopy [4]), to prove the described predictions. Our results aim to understand the footprints left in the dynamics by the specific orientation of the macrospin magnetization at the ASI vertices, so that a direct control of the SW propagation properties, particularly phaseshifts, might be pursued through specific macrospin reversals. This control is of crucial importance in the context of interferometric processing of SW information carriers, for magnonic logic devices and spin wave computing. [1] R. Negrello, F. Montoncello, M.T. Kaffash, M.B. Jungfleisch, G. Gubbiotti, APL Mater. 10, 091115 (2022). [2] Pietro Micaletti and Federico Montoncello, magnetochemistry 9, 158 (2023). [3] T. Sebastian, K. Schultheiss, B. Obry, B. Hillebrands and H. Schultheiss, Front. Phys. 3, 35 (2015). [4] Nick Träger, Felix Groß, Johannes Förster, Korbinian Baumgaertl, Hermann Stoll, Markus Weigand, Gisela Schütz, Dirk Grundler and Joachim Gräfe, Scientific Reports 10, 18146 (2020).