Establishing the Magnetoelastic Origin of Spin-Wave Routing through Focused Ion Beam Patterning

Abstract

Spin waves are promising information carriers for analog and wave-based computing, requiring compact and precisely engineered scattering landscapes. Focused ion beam (FIB) irradiation enables such control by locally modifying the spin-wave dispersion in yttrium iron garnet (YIG), yet the underlying crystallographic mechanisms remain unclear. Here, we present an experimentally validated framework that attributes FIB-induced spin-wave steering to magnetoelastic effects arising from irradiation-induced lattice dislocations. Following FIB irradiation and wet-chemical etching, local height profiles were obtained by atomic force microscopy (AFM) and used as fixed geometric constraints in fits of spin-wave dispersion relations measured by time-resolved magneto-optical Kerr effect (trMOKE) microscopy. The dispersion relation was extended by an explicit magnetoelastic field term, treated as a fit parameter. Its evolution reveals three successive deformation regimes, elastic, plastic, and partial amorphization, explaining the observed non-monotonic dependence of the spin-wave wavelength on ion dose. A three-phase deformation scenario based on SRIM simulations reproduces the extracted magnetoelastic field trends, validating the fitting approach. Micromagnetic simulations incorporating strain tensors derived from the experimental magnetoelastic field reproduce the characteristic non-monotonic wavelength behavior. These results establish a physical basis for FIB-engineered graded-index (GRIN) spin-wave landscapes and magnetoelastically programmable magnonic devices.