  Ultrafast magnetization dynamics in metallic heterostructures consists of a
combination of local demagnetization in the ferromagnetic constituent and
spin-dependent transport contributions within and in between the constituents.
Separation of these local and non-local contributions is essential to obtain
microscopic understanding and for potential applications of the underlying
microscopic processes. By comparing the ultrafast changes of the polarization
rotation and ellipticity in the magneto-optical Kerr effect (MOKE) we observe a
time-dependent magnetization profile M(z,t) in Co/Cu(001) films by exploiting
the effective depth sensitivity of the method. By analyzing the spatio-temporal
correlation of these profiles we find that on time scales before hot electron
thermalization (<100 fs) the transient magnetization of Co films is governed by
spin-dependent transport effects, while after hot electron thermalization (>200
fs) local spin-flip processes dominate.
