Magnonic crystals with complex geometry

Abstract

Magnonic crystals offer a wide playground to study the emergent properties of spin waves, and ferromagnetic antidot lattices are leading candidates for magnonic devices due to the faster propagation of spin waves combined with wide frequency tunability. Despite having a broad range of studies on periodic and quasiperiodic systems, a combination of quasiperiodic lattice with a complex basis is absent in the literature. The quasi-periodicity of octagonal lattice, along with a complex triangular antidot basis lacking reflection symmetry provides newer and richer spin-wave dynamics. Such complex magnonic crystal exhibits a strong eight-fold anisotropy superposed with a weak threefold anisotropy. This is in contrast to a strong four-fold symmetry superposed with a weak threefold symmetry observed in a square lattice with triangular antidot basis. The spatial profiles of spin waves revealed the presence of resonant modes with both even and odd mode quantization number, besides a mode conversion from extended to quantized mode with the systematic variation of the in-plane bias magnetic field orientation. These are in consonance with the strong anisotropic behaviour of the spin-wave modes. The strong modifications of the asymmetric potential energy landscape in these magnonic crystals lead to the stark modulation of the rich spin-wave dynamics, thus opening new avenues to reprogrammable magnonics with complex geometry.