Spin-wave band-gap engineering via mode hybridization in yttrium iron garnet film--Co-Fe-B nanodisk magnonic crystals with dipolar coupling
Phys. Rev. Applied 26, 044042 – Published 14 October, 2026
DOI: https://doi.org/10.1103/rd96-x9nd
Abstract
We investigate spin-wave transport in hybrid two-dimensional magnonic crystals comprising a low-damping yttrium iron garnet (YIG) film coupled to a periodic array of CoFeB nanodisks. Using propagating spin-wave spectroscopy, super-Nyquist magneto-optical Kerr effect microscopy, and micromagnetic simulations, we show that these systems host pronounced, tunable bandgaps that do not originate from conventional Bragg scattering, i.e., from standing-wave quantization restricted to a single axis by translational invariance along the propagation direction. Instead, the gaps arise from hybridization between the fundamental magnonic-crystal mode and in-plane transverse standing modes of the nanodisk array. Their spectral position and width are controlled by the array geometry and by the magnetic state of the nanodisks, including their vortex configuration, which sets both the static and dynamic dipolar coupling to the film. At larger lattice periods, additional gaps emerge from hybridization with modes quantized both transverse and parallel to the propagation direction, reflecting two-dimensional dispersion folding. Our results establish mode hybridization as a versatile mechanism for engineering spin-wave band structures beyond the constraints of conventional Bragg scattering and provide a pathway toward reconfigurable magnonic devices based on dipolar-coupled hybrid architectures.
