  By comparing the photo-induced magnetization dynamics in simple layered
systems we show how light-induced modifications of the magnetic anisotropy
directly enhance the magnetization. It is observed that the spin precession in
(CH3NH3)2CuCl4, initiated by a light pulse, increases in amplitude at the
critical temperature TC. The phenomenon is related to the dependence of the
critical temperature on the axial magnetic anisotropy. The present results
underline the possibility and the importance of the optical modifications of
the anisotropy, opening new paths toward the control of the magnetization state
for ultrafast memories.
