  Ultrashort optical pulses can trigger a variety of non-equilibrium processes
in magnetic thin films affecting electrons and spins on femtosecond timescales.
In order to probe the charge and magnetic degrees of freedom simultaneously, we
developed an x-ray streaking technique that has the advantage of providing a
jitter-free picture of absorption cross section changes. In this paper, we
present an experiment based on this approach which we performed using five
photon probing energies at the Ni $M_{2,3}$-edges. This allowed us to retrieve
the absorption and magnetic circular dichroism time traces, yielding detailed
information on transient modifications of electron and spin populations close
to the Fermi level. Our findings suggest that the observed charge and magnetic
dynamics both depend on the XUV probing wavelength, and can be described, at
least qualitatively, by assuming ultrafast energy shifts of the electronic and
magnetic elemental absorption resonances, as reported in recent work. However,
our analysis also hints at more complex changes, highlighting the need for
further experimental and theoretical analysis in order to gain a thorough
understanding of the interplay of electronic and spin degrees of freedom in
optically excited magnetic thin films.
