Configurational anisotropic spin waves in cross-shaped Ni₈₀Fe₂₀ nanoelements

Optically induced spin waves in Ni₈₀Fe₂₀ (permalloy) cross-shaped nanoelements are studied by time-resolved magneto-optical Kerr effect microscope. A strong anisotropy in the spin wave modes are observed with the orientation angle (ϕ) of the in-plane bias magnetic field. As ϕ deviates from 0° a single resonant mode splits into a numbers of modes, while the powers of the higher frequency modes increase as ϕ increases from 0 to 45°. The lowest frequency mode shows a four-fold configurational anisotropy. The mode of a single cross remains unaffected by the magnetostatic interaction of the neighbouring elements for ϕ = 0°, while the effect increases with ϕ and becomes maximum at 45°, making these elements interesting candidates as building blocks for magnonic devices.