High Spin-Wave Propagation Length Consistent with Low Damping in a Metallic Ferromagnet

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.