Ultrafast demagnetization dynamics of thin Fe/W(110) films: Comparison of time- and spin-resolved photoemission with time-resolved magneto-optic experiments

We report the results of time- and spin-resolved photoemission (TR-SPES) and time-resolved magneto-optical Kerr effect experiments on iron thin films. In particular, the extracted demagnetization times for both techniques are compared. It is shown that while for the Kerr measurements the demagnetization times are always limited by our time resolution ($250\ifmmode\pm\else\textpm\fi{}30$ fs), for the TR-SPES measurements this situation occurs only for relative quenching below $30%$. Above this value, the measured TR-SPES demagnetization time exceeds 500 fs. Different demagnetization probes can hence track different demagnetization times.