Abstract:
In this work, we investigate – using numerical simulations – the physical mechanisms of interaction between surface magnetostatic waves and a conducting medium in a hybrid structure composed of a bilayer yttrium iron garnet (YIG) film and a metallic magnonic crystal. Particular attention is paid to analyzing the transformation of the dispersion spectrum of surface magnetostatic waves as a function of the metal's electrical conductivity and its spatial position relative to the ferromagnetic layers. The interaction is physically underpinned by eddy currents induced in the metallic screen by the oscillating magnetic field of the spin wave. These eddy currents generate their own magnetic field, which in turn perturbs the original wave, modifying its dipolar field and consequently altering its dispersion characteristics. It is demonstrated that reducing the metal's conductivity weakens the screening effect, manifesting as a smoothing of the anti-crossing between dispersion modes and a narrowing of Bragg bandgaps. A threshold behavior of conductivity is identified: below this threshold, the system behaves essentially like an unshielded bilayer YIG film. Furthermore, the effect exhibits strong dependence on the screen's position, explained by the varying degree of spatial overlap between the surface magnetostatic wave fields – localized at different interfaces - and the region of induced eddy currents. These results contribute to the fundamental understanding of spin-wave electrodynamics in ferrite-metal hybrid structures.
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