Control of spin relaxation anisotropy by spin-orbit-coupled diffusive spin motion

Spatiotemporal spin dynamics under spin-orbit interaction is investigated in a (001) GaAs two-dimensional electron gas using magneto-optical Kerr rotation microscopy. Spin-polarized electrons are diffused away from the excited position, resulting precession because of diffusion-induced field. Near cancellation between field and external magnetic field, induced frequency depends nonlinearly on diffusion velocity, which unexpected conventional linear relation velocity. This behavior originates an enhancement relaxation anisotropy by velocity perpendicular to direction. We demonstrate that anisotropy, has been regarded as material constant, can be controlled via diffusive motion.