Sub-50 nm wavelength spin waves excited by low-damping Co25Fe75 nanowires

Spin waves are considered as a promising candidate for next-generation logic devices with low power dissipation. Exchange spin waves are particularly attractive for high-speed data processing and scaling down the size of magnonic logic devices. Here, we achieve the excitation of short-wavelength propagating spin waves with wavelengths as short as 45 nm in a 20 nm-thick yttrium iron garnet film covered by 70 nm-wide Co25Fe75 nanowires with low magnetic damping and high saturation magnetization, and the ferromagnetic resonance of Co25Fe75 nanowires is excited by a 200 nm-wide nano-strip line. From our measurements, we extrapolate a group velocity for exchange spin waves of up to 1.9 km/s close to the zero magnetic field (0.5 mT).