  Coherent spin oscillations were non-thermally induced by circularly polarized
pulses in fully compensated antiferromagnetic NiO. This effect is attributed to
an entirely new mechanism of the action, on the spins, of the effective
magnetic field generated by an inverse Faraday effect. The novelty of this
mechanism is that spin oscillations are driven by the time derivative of the
effective magnetic field acting even on "pure" antiferromagnets with zero net
magnetic moment in the ground state. The measured frequencies (1.07 THz and 140
GHz) of the spin oscillations correspond to the out-of-plane and in-plane modes
of antiferromagnetic magnons.
