  We report ultra-low intrinsic magnetic damping in
Co$_{\text{25}}$Fe$_{\text{75}}$ heterostructures, reaching the low $10^{-4}$
regime at room temperature. By using a broadband ferromagnetic resonance
technique, we extracted the dynamic magnetic properties of several
Co$_{\text{25}}$Fe$_{\text{75}}$-based heterostructures with varying
ferromagnetic layer thickness. By estimating the eddy current contribution to
damping, measuring radiative damping and spin pumping effects, we found the
intrinsic damping of a 26\,nm thick sample to be $$\alpha_{\mathrm{0}} \lesssim
3.18\times10^{-4}$. Furthermore, using Brillouin light scattering microscopy we
measured spin-wave propagation lengths of up to $(21\pm1)\,\mathrm{\mu m}$ in a
26 nm thick Co$_{\text{25}}$Fe$_{\text{75}}$ heterostructure at room
temperature, which is in excellent agreement with the measured damping.
