Magnetic phase transition in DyFe _0.6 Mn _0.4 O ₃ crystal investigated with ultrafast spectroscopy

Abstract

By use of optical pump-probe spectroscopy, we report the ultrafast carrier dynamics in a DyFe0.6Mn0.4O3 (DFMO) single crystal. We find that the photo-excited electrons firstly relax through a fast electron-phonon coupling , followed by intermediate relaxation (tens of ps) and slow nanosecond relaxation processes. Meanwhile, a photo-induced coherent acoustic phonon with frequency of 36.3 GHz is detected, and the sound velocity with magnitude of is determined. Moreover, the time constants in intermediate relaxation are found to increase significantly in the vicinity of the Morin-like phase transition temperature and the Néel temperature, which are interpreted as the coexisting of collinear- and canted-antiferromagnetic properties in DFMO, and the spectroscopic results are consistent with the temperature-dependent magnetic-moment measurements.