Ultrafast magneto-optical response of iron thin films

Optical pump probe techniques are utilized to measure the time-resolved magneto-optical Kerr effect (TRMOKE) of a ferromagnetic iron film at room temperature in air. We focus on the interpretation of the TRMOKE signal, and find the experimental data to be consistent with a simple phenomenological model. Nonmagnetic contributions are present in the TRMOKE signal up to 100 ps after excitation. Without making further assumptions, this prevents a determination of the true magnetization dynamics. The initial magnetization does not change its direction, and within the first picoseconds there is no detectable dependence of the magnetization dynamics on the external magnetic field.