Picosecond Magnetization Dynamics of Single-Crystal Fe $_{3}$ O $_{4}$ Thin Films

The time-resolved magnetization dynamics of epitaxial Fe ₃O ₄ ultra-thin films grown on GaAs were investigated for the first time using a field pumped TRMOKE (time-resolved magneto-optical Kerr effect) setup. The dynamic response of the sample to the field pulse was measured for different DC bias fields applied along two orthogonal crystalline directions for 3 and 6 nm films. The results show a heavily damped precessional response to the applied field pulses. By fitting the Landau-Lifshitz-Gilbert equation to the data the temporal evolution of the magnetisation can be reproduced and the damping constant determined to be around 0.1.