Femtosecond inverse Faraday effect in magnetic ionic liquid [bmim]FeCl4

The nonthermally photoinduced magnetization in a magnetic ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate ([bmim]FeCl(4)) is investigated via the inverse Faraday effect on the subpicosecond time scale at room temperature. The pump beam induced the ellipticity changes of probe beam are revealed to arise from the contributions of both the inverse Faraday effect and the optical Kerr effect. The formation of about 1.8 THz coherent superposition between magnetic sublevels of the Fe(3+)-ion's ground-state multiplet is observed with a circular pump polarization, which is assigned to the allowed impulsively stimulated Raman scattering in the magnetic ion liquid. (C) 2011 American Institute of Physics. [doi:10.1063/1.3574442]