Ultrafast all-optical manipulation of the antiferromagnetic order

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In the past year employed the established experimental set-up to perform experiments on CuB2O4. An extensive experimental investigation of the photo-induced optical and magnetic dynamics of this material has been performed. In particular, measurements as a function of the laser intensity and polarization were carried on and the effect of an externally applied magnetic field was investigated as well. The main goal of the investigation was establishing the optical and spin dynamics induced by laser pulses, since under the particular experimental conditions chosen the sample could have undergone a laser-induced phase transition. To be more specific: before illumination the sample was in a non-magnetoelectric phase. However, the phase diagram and the absorption spectrum suggest that the optical excitation in the near-infrared spectral range may induced the magneto-electricity. Tracking the peculiar optical fingerprint of the magneto-electricity in CuB2O4, I studied this phenomenon. Our experiment was successful, since it revealed a novel phenomenon: the magneto-electricity in CuB2O4 was activated by light on the ultrafast time-scale (i.e. 600 fs). This evidence was confirmed by a thorough series of measurements performed as a function of the magnetic field, temperature, polarization and intensity of the pump beam. Such an unprecedented optical manipulation of solids establishes novel possibilities to control magnets with electric voltages, which are much cheaper and easier to generate than magnetic fields.