Spin-flip processes and ultrafast magnetization dynamics in Co -   unifying the microscopic and macroscopic view of femtosecond magnetism
  The femtosecond magnetization dynamics of a thin cobalt film excited with ultrashort laser pulses has been studied using two complementary pump-probe techniques, namely spin-, energy- and time-resolved photoemission and time-resolved magneto-optical Kerr effect. Combining the two methods it is possible to identify the microscopic electron spin-flip mechanisms responsible for the ultrafast macroscopic magnetization dynamics of the cobalt film. In particular, we show that electron-magnon excitation does not affect the overall magnetization even though it is an efficient spin-flip channel on the sub-200 fs timescale. Instead we find experimental evidence for the relevance of Elliott-Yafet type spin-flip processes for the ultrafast demagnetization taking place on a time scale of 300 fs. 
M. Cinchetti, M. S\'anchez Albaneda, D. Hoffmann, T. Roth, J.-P.   W\"ustenberg, M. Krau{\ss}, O. Andreyev, H.C. Schneider, ...