Terahertz-driven ultrafast magnetization dynamics in canted antiferromagnetic YFeO3

We investigate the coherent precessional motion of the magnetic moment in the canted antiferromagnetic YFeO3 single crystal after excitation by the transient magnetic field of an ultra-short THz pulse. Time-resolved measurements of the magneto-optical response in the presence of external magnetic fields confirm the exclusive magnetic origin of the interaction between THz pulse and the spin system.. By tuning the spectral component of the input THz pulse around the quasi-ferromagnetic mode located near 0.3 THz, we have experimentally verified that the THz control of the spin state requires resonant excitation. We could confirm these results from the simulation based on the Landau-Lifshitz-Gilbert equation with two sub-lattice model for the canted antiferromagnet. Furthermore, we demonstrate that the spin state can be switched all-optically on a picosecond timescale using THz pulses of square and oscillating shapes. Whereas the oscillating THz pulse with a spectral component resonant with the magnetic excitations is necessary for an efficient magnetization switching, we study the possibility for a further reduction of the necessary THz field strength by examining influences of variations in the anisotropy energy and Dzyaloshinskii-Moriya interaction upon the switching behaviors.