Abstract
We study how the color and polarization of ultrashort pulses of visible light can be used to control the demagnetization processes of the antiferromagnetic insulator . We utilize time-resolved second harmonic generation (SHG) to probe how changes in the magnetic and structural state evolve in time. We show that varying the pump photon-energy to excite either localized transitions within the Cr or charge transfer states leads to markedly different dynamics. Through a full polarization analysis of the SHG signal, symmetry considerations, and density functional theory calculations, we show that, in the nonequilibrium state, SHG is sensitive to both lattice displacements and changes to the magnetic order, which allows us to conclude that different excited states couple to phonon modes of different symmetries. Furthermore, the spin-scattering rate depends on the induced distortion, enabling us to control the timescale for the demagnetization process. Our results suggest that selective photoexcitation of antiferromagnetic insulators allows fast and efficient manipulation of their magnetic state.
- Received 22 October 2015
- Revised 8 July 2016
DOI:https://doi.org/10.1103/PhysRevB.94.014430
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