In a pioneering experiment at the European XFEL, we found that in 4f rare-earth metals, the optical pump-pulse together with electron scattering processes can affect the 4f electronic state on ultrashort time scales (XFEL annual report 2020).

The 4f electronic state is connected with spin and orbital magnetic momenta that define the coupling of the magnetic system to the environment. Manipulating such parameter on ultrafast timescales gives a new dimension to the discussion about ultrafast magnetic response to optical excitation.