Sub-100 femtosecond time scale spin dynamics in epitaxial Fe3O4 thin film

Abstract We have investigated the ultrafast laser-induced magnetization and reflectivity dynamics in the Fe3O4 thin film using all-optical pump-probe measurements. The high-quality of our sample is verified by the temperature-dependent static magnetic properties, showing a clear Verwey transition. Although the Fe3O4 is predicted to be a half-metal, the demagnetization process upon laser incident shows a transition-metal-like behavior. The demagnetization characteristic time has been found to be in sub-100 femtosecond (fs) time scale, suggesting the dominant interaction of hole spin-flip processes. The spin relaxation process has been found to be around 600 fs, which is attributed to the electron-phonon coupling in accordance to the observed two electron-phonon coupling modes in reflectivity dynamics. Our results provide new insight into the ultrafast laser-induced spin dynamics in half-metallic ferrimagnet.