Spin Oscillations in Antiferromagnetic NiO Triggered by Circularly Polarized Light

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.