Probing optically induced spin currents using terahertz spin waves in noncollinear magnetic bilayers

Optically induced spin currents have proven to be useful in spintronics applications, allowing for sub-ps all-optical control of magnetization. However, the mechanism responsible their generation is still heavily debated. Here we use excitation spin-current THz spin-waves noncollinear bilayer structures directly study optical spin-currents time domain. We measure a significant laser-fluence dependence spin-wave phase, which can quantitatively explained assuming current proportional derivative Measurements absolute supported by theoretical calculations and micromagnetic simulations, suggest that simple ballistic transport picture sufficient properly explain our experiments damping-like STT dominates generation. Our findings laser-induced demagnetization share same microscopic origin.