Terahertz Spectroscopy of Femtosecond Spin Dynamics in Orthoferrites

Here we report experiments performed on orthoferrites by means of THz time-domain emission spectroscopy. We show that the femtosecond laser pulses excite both iron and rare-earth sub-systems on sub-picosecond timescale. In particular, the novel route to the optical control of the exchange interaction has been discovered