Excitation and Tuning of Spin Waves in Magnonic Crystals by Magnetic Coupling

Abstract

Magnonic crystals with artificial micro/nanomagnetic pattern act as low‐loss information carriers in many microwave devices. The excitation and control of spin waves inside is essential and fundamental in magnonic crystal applications. Herein, permalloy micro‐disk patterns are constructed on a continuous permalloy film, and they succeed in exciting spin waves in this bilayer‐structured magnonic crystal. The spin‐wave modes can be effectively tuned by varying the periodic parameter (P) of upper‐layer disk pattern, which is confirmed by the transition from single‐peak to multi‐peak in ferromagnetic resonance (FMR) spectra with P decreased from 4 to 0.5 μm. The split in FMR spectra is reconstructed by micromagnetic simulation, revealing that three spin‐wave modes are respectively excited by the domain walls of below‐layer continuous film, geometrical restriction of permalloy micro‐disk, and magnetic coupling between neighboring permalloy micro‐disks. The tunable spin‐wave behavior in this bilayer‐structured magnonic crystal presents broad application prospect in programmable spintronic devices at micro/nanoscale.