Spin accumulation on Cu driven by ultrafast demagnetization of Fe, Co, and Ni*

Generation of spin currents out of ferromagnets is an essential requirement for spintronics. Recently, measurement of dynamics of magnetization of ferromagnets revealed the existence of ultrafast spin currents during ultrafast demagnetization of metallic ferromagnets. Here, we report direct measurements of transient spin accumulation on a non-magnetic Cu layer driven by ultrafast demagnetization of Fe, Co, and Ni layers. Dynamic behaviors of spin accumulation explicitly shows a close correlation between demagnetization of a ferromagnet and spin accumulation on a non-magnet. Magnitudes of spin accumulation have increased by an order magnitude compared to previous results with [Co/Pt] and [Co/Ni] multilayers.