Photoinduced magnetization enhancement in two-dimensional weakly anisotropic Heisenberg magnets

By comparing the photoinduced 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)(2)CuCl4, initiated by a light pulse, increases in amplitude at the critical temperature T-C. 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 different paths toward the control of the magnetization state for ultrafast memories.