Ultra-broadband spin wave propagation in Co₂(Mn_0.6Fe_0.4)Si thin films

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 Co₂(Mn_0.6Fe_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 up 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.