Spin-signal propagation in time-dependent noncollinear spin transport

Using a macroscopic analysis, we show that time-dependent noncollinear spin transport possesses a wavelike character. This leads to modifications of pure spin-diffusion dynamics and allows one to extract a finite spin-signal propagation velocity. We numerically study the dynamics of a pure spin current pumped into a nonmagnetic layer for precession frequencies ranging from GHz to THz.