Femtosecond electron and spin dynamics of the Gd(0001) surface are investigated by time-resolved
photoemission and second harmonic generation. Upon optical excitation the spin polarization of the
surface state is reduced by half while its exchange splitting remains nearly unchanged. Electron-
Magnon interaction is proposed to facilitate electron spin flip scattering among spin-mixed surface
and bulk states which provides a mechanism for ultrafast demagnetization.
The publication is available at link DOI: 10.1103/PhysRevLett.95.137402