Spin diffusion induced by pulsed-laser heating and the role of spin heat accumulation

We present a model for describing spin diffusion in normal-metal/ferromagnetic-metal heterostructures induced by pulsed-laser heating. The model is based on the assumptions that electronic heat currents give rise to the spin-dependent Seebeck effect and that ultrafast demagnetization generates spin accumulation with a rate proportional to the demagnetization rate measured. Spin-diffusion currents are then driven by gradients in spin accumulation and electron temperature. The model considers spin-dependent thermal conductivity and electron-phonon coupling, which can give rise to different effective temperatures for majority and minority spins, known as spin heat accumulation. We find that spin heat accumulation can significantly enhance the spin-dependent Seebeck effect.