  We report on an element- and time-resolved investigation of femtosecond laser
induced ultrafast dynamics of 3d and 4f spins in a ferrimagnetic Co80Dy20 alloy
as a function of temperature. We observe an increase of the Co3d characteristic
demagnetization time and a decrease of the Dy4f demagnetization time when the
temperature is approaching the Curie temperature. It suggests that the critical
slowing down regime, which affects the laser induced ultrafast dynamics in pure
3d transition metals and 4f rare-earth ferromagnetic layers, vanishes for the
Dy sublattice in the CoDy alloy, in line with the theoretical predictions of
the Landau-Lifshitz-Bloch model.
