Micromagnetic study of spin-wave dispersion engineering and magnon confinement in YIG magnonic crystals

Abstract

This work investigates magnonic crystals based on nanostructured Yttrium Iron Garnet (YIG) waveguides through micromagnetic simulations performed with mumax3. Two main objectives are addressed: engineering controllable spin-wave band structures and spatially confining magnons in a cavity. The structures consist of a YIG waveguide patterned with a one-dimensional periodic array of holes of varying geometry. For rectangular holes, a lower flat band emerges whose frequency decreases with increasing hole width, providing a geometric tuning knob; this tunability is exploited to design a magnon cavity that confines magnons at a defect site via a quadratic taper. Concave and elliptical geometries yield quasi-gapless, thin-film-like dispersions, identified as the most suitable candidates for magnon Rayleigh–Jeans condensation, which preliminary parametric-pumping simulations did not yet achieve.