Ultrafast thermoelastic dynamics of HoMnO₃ single crystals derived from femtosecond optical pump-probe spectroscopy

In this paper, the photo-induced ultrafast thermoelastic dynamics of hexagonal HoMnO₃ single crystals has been studied by using optical pump-probe spectroscopy. The thermoelastic effect in the ab-plane of hexagonal HoMnO₃, associated with giant magnetoelastic coupling around the Néel temperature (T_N), is intimately correlated to the emergence of a negative component in the transient reflectivity changes (ΔR/R) obtained in temperaturedependent pump-probe experiments. Moreover, the variation in the oscillation period in ΔR/R caused by a strain pulse propagating along the c-axis exhibits an abrupt drop around T_N, presumably due to the antiferromagnetic-orderinginduced changes in ferroelectricity.