Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films

We experimentally investigate to what extent superdiffusive spin transport contributes to the ultrafast demagnetization of ferromagnets by pumping Ni thin films from the front side and back side of the sample. Within the experimental accuracy, the temporal evolution of the magnetization for front-side and back-side pumping is identical, hence no influence of transport was detected. Furthermore, adding a conducting buffer layer to enhance spin transport does not alter the magnetization dynamics significantly either. In order to explain the experimental results, angular momentum has to be locally dissipated on femtosecond timescales, supporting heating of the spin system as the main driving force for ultrafast demagnetization in the investigated ferromagnetic films. (C) 2013 AIP Publishing LLC.