Coherent manipulation of magnetization precession in ferromagnetic   semiconductor (Ga,Mn)As with successive optical pumping
  We report dynamic control of magnetization precession by light alone. A ferromagnetic (Ga,Mn)As epilayer was used for experiments. Amplitude of precession was modulated to a large extent by tuning the time interval between two successive optical pump pulses which induced torques on magnetization through a non-thermal process. Nonlinear effect in precession motion was also discussed. 
Y. Hashimoto and H. Munekata