  We report the experimental observation of Snell's law for magneto-static spin
waves in thin ferromagnetic Permalloy films by imaging incident, refracted and
reflected waves. We use a thickness step as the interface between two media
with different dispersion relation. Since the dispersion relation for
magneto-static waves in thin ferromagnetic films is anisotropic, deviations
from the isotropic Snell's law known in optics are observed for incidence
angles larger than 25\textdegree{} with respect to the interface normal between
the two magnetic media. Furthermore, we can show that the thickness step
modifies the wavelength and the amplitude of the incident waves. Our findings
open up a new way of spin wave steering for magnonic applications.
