Ultrafast dynamics in multiferroic BiFeO$_{3}$

We report the ultrafast time-resolved optical measurements of multiferroic BiFeO$_{3, }$which exhibits both magnetic and ferroelectric ordering at room temperature. The coupling between these two orders makes it an attractive material for potential data-storage devices. However, a detailed understanding of this coupling is still under debate. Ultrafast optical spectroscopy can potentially shed light on magnetoelectric coupling in BiFeO$_{3}$ by unraveling the different contributions in the time domain. Here, we use degenerate 400 nm pump-probe spectroscopy to excite and probe a BiFeO$_{3}$ thin film above its bandgap. The measured relaxation consists of a fast decay ($\sim $1 ps) followed by a slow recovery ($\sim $150 ps). We attribute the fast component to the recovery of photoexcited carriers. The slow recovery may be due to spin-lattice relaxation.