Shape dependent high frequency spin-wave dynamics in nanoscale magnonic crystals

Abstract Efficient tunability of magnetization dynamics in two-dimensional circular and triangular-shaped Ni 80 Fe 20 antidots arranged in hexagonal lattice is demonstrated using a combination of all-electrical and all-optical detection techniques. A broad band of modes is observed for both the lattices. A strong variation in the spin-wave spectra is obtained with the strength and orientation of the bias magnetic field. A crossover between two higher frequency branches is observed with the variation of bias magnetic field strength in circular antidot lattice, whereas no such crossover is observed in the triangular antidot lattice. In addition, the spin-wave modes in both lattices show strong six-fold anisotropic behaviour presumably due to the variation of internal field distribution originating from a combination of the lattice arrangement and the shape of the antidots as a function of the bias magnetic field orientation. Micromagnetic simulations qualitatively reproduce the experimentally observed spin-wave modes and the simulated mode profiles reveal the presence of extended and quantized standing spin-wave modes in these lattices. Also, some lower frequency localized edge modes, obtained in the triangular antidot lattice due to the asymmetric demagnetized regions at sharp corners, are not observed in the circular antidot lattice. These observations are significant for large tunability and anisotropic propagation of spin waves in GHz frequency magnetic devices.