Impact of mode hybridization on spin-wave profiles in bi-component magnonic crystals

The study investigates mode hybridisation in two-dimensional permalloy–cobalt magnonic crystals. Calculations were performed using the plane-wave method, with particular emphasis on the effects accompanying hybridisation. A distinctive feature revealed in this work is the exchange, between hybridising modes, of the excitation concentration coefficient in the constituent materials (e.g. in cobalt). This coefficient describes the fraction of spin-wave energy concentrated within one of the components of the composite. Its analysis enables the identification of hybridisation even when other manifestations—such as profile swapping or clear branch repulsion—are only weakly pronounced. We demonstrate cases in which the exchange of the concentration coefficient occurs between hybridising modes without the typical swapping of spin-wave profiles, or with only minimal repulsion between their branches in the frequency spectrum.