Fig. 4. Selection rules for the excitation of the in-plane magnetic mode.

(A) Pump-induced rotation of the probe polarization plane as a function of pump-probe delay time Δt for different orientations of the linear polarization of the pump. The pump photon energy is 1.0 eV. (B) The amplitude of the oscillations as a function of the azimuthal angle ϕ between the pump polarization plane and the a crystal axis. (C) Schematics showing that the electric field of light acts as an instantaneous photomagnetic anisotropy (dashed line) with a direction along the light polarization plane, resulting in a torque and subsequent oscillations of the Néel vector L and net magnetization M.