Ultrafast Opto-Magnetic Excitation of Magnetization Dynamics

This review summarizes the recent progress in laser-induced magnetization dynamics, in particular, the direct nonthermal opto-magnetic excitation of spin systems. Circularly polarized pulses are shown to act as strong transient magnetic field pulses originating from the nonabsorptive inverse Faraday effect. An all-optical scheme of excitation and detection of different antiferromagnetic resonance modes with frequencies of several hundred gigahertz is demonstrated, along with a straightforward method to separate the thermal and nonthermal excitation effects. Such a method could also be applied to metals, such as rare-earth-transition metal alloys. In the latter, moreover, the magnetization could be reversed in a reproducible manner by single 40 fs circularly polarized laser pulses, without any applied magnetic field. All these findings open new insights into the understanding of ultrafast magnetic excitation and, considering recent progress in the development of compact ultrafast lasers, may provide new prospects for applications of ultrafast opto-magnetic phenomena in magnetic storage and information processing technology.