The magnetic linear dichroism of the Gd 4f core-level is studied in a time-resolved photoemission experiment employing laser pump- and synchrotron-radiation probe-pulses. Upon optical excitation of the 5d6s valence electrons with femtosecond laser pulses the magnetic order in the 4f spin-system is reduced. Remarkably, the linear dichroism remains at 80% of the equilibrium contrast while the lattice temperature increases above the Curie temperature due to electron-phonon scattering. Contrasting itinerant ferromagnets, this shows that equilibration between the lattice and spin subsystems takes in Gd longer than 50 ps and is established in parallel with heat diffusion.
The original publication is available at www.springerlink.com by link DOI: 10.1103/PhysRevLett.100.107202