The effect of Ga-ion irradiation on sub-micron-wavelength spin waves in yttrium-iron-garnet films

We investigate the effect of focused-ion-beam (FIB) irradiation on spin waves with sub-micron wavelengths in yttrium-iron-garnet films. Time-resolved scanning transmission x-ray microscopy was used to image the spin waves in irradiated regions and deduce corresponding changes in the magnetic parameters of the film. We find that the changes of Ga⁺ irradiation can be understood by assuming a few percent change in the effective magnetization M eff of the film due to a trade-off between changes in anisotropy and effective film thickness. Our results demonstrate that FIB irradiation can be used to locally alter the dispersion relation and the effective refractive index n eff of the film, even for submicron wavelengths. To achieve the same change in n eff for shorter wavelengths, a higher dose is required, but no significant deterioration of spin wave propagation length in the irradiated regions was observed, even at the highest applied doses.