Reconfigurable Ferromagnetic Resonances by Engineering Inhomogeneous Magnetic Textures in Artificial Magnonic Crystals

Advanced microfabrication gives rise to an extra degree of freedom for controlling magnetic textures, which determine the spin dynamics of thin-film magnets for various spintronic devices. However, the intuitive understanding of complicated ferromagnetic resonances (FMRs) is still challenging for lacking directly observed evolution of inhomogeneous magnetic textures. This study demonstrates the reconfigurable FMRs by introducing artificial patterns of antidot lattices (namely magnonic crystals), mediated by the engineering of inhomogeneous magnetic textures. Ordered walls are observed directly in such a magnetic film using in situ Lorentz transmission electron microscopy. By applying in-plane external magnetic fields, arc-shaped domain walls can be nucleated along the edge of patterns, inducing the splitting of FMRs from a single peak to two branches (marked by low-frequency and high-frequency branches, respectively). Complementary micromagnetic simulations reconstruct the inhomogeneous magnetic textures and splitting of FMRs. It is indicated that the low-frequency branch ascribes to the confined mode excited by arc-shaped domain walls, and the high-frequency one originates from the quasi-uniform mode generated by in-plane magnetization between arc-shaped domain walls. These results offer new opportunities for designing patterned magnonic devices and understanding the unique phenomenon of spin dynamics.