  Magnetic Heusler materials with very low Gilbert damping are expected to show
novel magnonic transport phenomena. We report nonlinear generation of higher
harmonics leading to the emission of caustic spin-wave beams in a low-damping,
micro-structured Co2Mn0.6Fe0.4Si Heusler waveguide. The source for the higher
harmonic generation is a localized edge mode formed by the strongly
inhomogeneous field distribution at the edges of the spin-wave waveguide. The
radiation characteristics of the propagating caustic waves observed at twice
and three times the excitation frequency are described by an analytical
calculation based on the anisotropic dispersion of spin waves in a magnetic
thin film.
