Chromatic Aberration Effect in Refraction of Spin Waves

We numerically investigated the refraction property of spin waves (SWs) at thickness step in films with out-ofplane magnetization, in which the SWs propagate isotropically in the film plane. It was confirmed the isotropic SWs were refracted at a thickness step by following the Snell's law. We also found that the refraction angle of SWs of the dipole-exchange mode depends on the resonant frequency, indicating that the chromatic aberration effect should be taken into account in designing magnonic devices.