Ultrafast Dynamics of BiFeO3 Thin Films Studied by Dual-Color Femtosecond Spectroscopy

Abstract

The ultrafast dynamics in (100)-oriented BiFeO3 thin films were studied from 20 K to 300 K by using the dual-color femtosecond pump-probe spectroscopy, which were performed by the 400 nm (3.1 eV) pump pulses above the energy gap of 2.67 eV and the 800 nm (1.55 eV) probe pulses below the energy gap of 2.67 eV. From the temperature-dependent transient reflectivity changes (Delta R/R), the anomalous changes were clearly observed below 200 K caused by magnons. Thus, the femtosecond pump-probe spectroscopy could unambiguously reveal the magnetization dynamics in BiFeO3 with strong magnetoelectric coupling.