Coherent control of magnetization via inverse Faraday effect

Recent experiments have demonstrated the possibility of ultrafast non-thermal control of magnetization in rare-earth orthoferrites and ferrimagnetic garnet films via circularly polarized femtosecond laser pulses. Single and double pump pulses set up ultrafast magnetic fields via the inverse Faraday effect, thereby non-thermally exciting spin dynamics. A theoretical study of coherent control of the magnetization in rare-earth orthoferrites is performed by considering the effect of multiple pulses. The investigation is based on a model for orthoferrites recently proposed for the study of the inverse Faraday effect in the case of a single pump pulse. In the linear regime without damping, interferential effects take place: in-phase pulses induce a coherent enhancement of magnetization. The role of relaxation and nonlinearity is studied in relation to their capability of hampering coherent manipulation of magnetization. After many pulses, the effect of damping induces a stationary behaviour with a periodicity determined by the separation time between successive pulses. Due to nonlinear effects, the magnetization can be characterized by complex beating patterns whose amplitude and periodicity depend on the intensity of exciting pulses