Coherent acoustic phonons in hexagonal HoMnO(3) probed by femtosecond spectroscopy

Abstract

We have observed the coherent acoustic phonons in the hexagonal manganite HoMnO(3) single crystals using wavelength-dependent femtosecond pump-probe spectroscopy. The oscillatory component of the photoinduced transient reflectivity change (Delta R/R) at various pump-probe wavelengths is consistent with the model of strain pulse propagation. Furthermore, the oscillation period of the oscillation is strong temperature- and wavelength-dependent. In particular, the period of all oscillations in Delta R/R for various wavelengths are very similar in the vicinity of the Neel temperature (T(N)), which associates with the appearance of the antiferromagnetic (AFM) long-range ordering.