Influence of nonmagnetic dielectric spacers on the spin-wave response of one-dimensional planar magnonic crystals

Abstract

One-dimensional planar magnonic crystals are usually fabricated as a sequence of stripes intentionally or accidentally separated by nonmagnetic spacers. The influence of spacers on shaping the spin-wave spectra is complex and still not completely clarified. We perform detailed numerical studies of the one-dimensional single- A nd bicomponent magnonic crystals comprised of a periodic array of thin ferromagnetic stripes separated by nonmagnetic spacers. We show that the dynamic dipolar interactions between the stripes, mediated even by ultranarrow nonmagnetic spacers, lead to a significant increase in the frequency of the ferromagnetic resonance mode, while simultaneously reducing the spin-wave group velocity. We attribute these spectral deformations to the modifications of dipolar pinning and shape anisotropy, both of which are dependent on the width of the spacers and the thickness of the stripes, as well as changes with the dynamical magnetic volume charges formed due to inhomogeneous spin-wave amplitude.