We examined the photo-induced dynamics of ferromagnetic Co/Pt thin films
demonstrating perpendicular magnetic anisotropy with element specificity using
resonant polar magneto-optical Kerr effect measurements at Pt~N${}_{6,7}$ and
Co~M${}_{2,3}$ edges with an x-ray free electron laser. The obtained results
showed a clear element dependence of photo-induced demagnetization time scales:
$\tau_\textrm{demag.}^\textrm{Co}=80\pm60~\textrm{fs}$ and
$\tau_\textrm{demag.}^\textrm{Pt}=640\pm140~\textrm{fs}$. This dependence is
explained by the induced moment of the Pt atom by current flow from the Co
layer through the interfaces. The observed magnetization dynamics of Co and Pt
can be attributed to the characteristics of photo-induced Co/Pt thin film
phenomena including all-optical switching.