  X-ray magnetic circular dichroism spectroscopy using an X-ray free electron
laser is demonstrated with spectra over the Fe L$_{3,2}$-edges. This new
ultrafast time-resolved capability is then applied to a fluence-dependent study
of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in
a GdFeCo thin film above its magnetization compensation temperature. At the
magnetic switching fuence, we corroborate the existence of a transient
ferromagnetic-like state. The timescales of the dynamics, however, are longer
than previously observed below the magnetization compensation temperature.
Above and below the switching fluence range, we observe secondary
demagnetization with about 5 ps timescales. This indicates that the spin
thermalization takes longer than 5 ps.
