High spin-wave propagation length consistent with low damping in a metallic ferromagnet

We report ultralow intrinsic magnetic damping in Co₂₅Fe₇₅ heterostructures, reaching the low 10⁻⁴ regime at room temperature. By using a broadband ferromagnetic resonance technique in out-of-plane geometry, we extracted the dynamic magnetic properties of several Co₂₅Fe₇₅-based heterostructures with varying ferromagnetic layer thicknesses. By measuring radiative damping and spin pumping effects, we found the intrinsic damping of a 26 nm thick sample to be $α0≲3.18×10−4$⁠. Furthermore, using Brillouin light scattering microscopy, we measured spin-wave propagation lengths of up to (21 ± 1) μm in a 26 nm thick Co₂₅Fe₇₅ heterostructure at room temperature, which is in excellent agreement with the measured damping.