Ferromagnetic Heusler alloys with low magnetic damping are highly promising materials for magnonic devices, which rely on excitation and detection of spin waves. Using all-electrical spin wave spectroscopy we report spin wave propagation in sputtered Co 2 (Mn 0.6 ,Fe 0.4 )Si Heusler alloy thin films with thickness of 50 nm. We integrated a nanostructured microwave antenna to locally excite and detect propagating spin waves in a Damon-Eshbach configuration. We estimate the group velocity to be

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... to 12.0 km/s and we observe spin wave propagation with a frequency band as broad as 15 GHz. From the experimental frequency dependence of group velocity we calculate the spin wave dispersion. Our results show that all-electrical measurements are a powerful method for determining the fundamental spin wave characteristics of Heusler alloys, over a broad and tunable range of frequencies, and with group velocities an order of magnitude higher than in conventional materials. a) These authors contributed equally to this work b) Electronic