Ultrafast Time-Resolved Faraday Rotation in EuO Thin Films
  We have investigated the ultrafast spin dynamics in EuO thin films by time-resolved Faraday rotation spectroscopy. The photoinduced magnetization is found to be increased in a transient manner, accompanied with subsequent demagnetization. The dynamical magnetization enhancement showed a maximum slightly below the Curie temperature with prolonged tails toward both lower and higher temperatures and dominates the demagnetization counterpart at 55 K. The magnetization enhancement component decays in ~1 ns. The realization of the transient collective ordering is attributable to the enhancement of the f-d exchange interaction. 
F. Liu, T. Makino, T. Yamazaki, K. Ueno, A. Tsukazaki, T. Fukumura, Y.   Kong, and M. Kawasaki
cond-mat.mtrl-sci