Rettig, L.; Dornes, C.; Thielemann-Kuehn, N.; Pontius, N.; Zabel, H.; Schlagel, D. L.; Lograsso, T. A.; Chollet, M.; Robert, A.; Sikorski, M.; Song, S.; Glownia, J.M.; Schüßler-Langeheine, C.; Johnson, S.L.; Staub, U.: Itinerant and Localized Magnetization Dynamics in Antiferromagnetic Ho. Physical Review Letters 116 (2016), p. 257202/1-6

Using femtosecond time-resolved resonant magnetic x-ray diffraction at the Ho L3 absorption edge, we investigate the demagnetization dynamics in antiferromagnetically ordered metallic Ho after femtosecond optical excitation. Tuning the x-ray energy to the electric dipole (E1, 2p→5d) or quadrupole (E2, 2p→4f) transition allows us to selectively and independently study the spin dynamics of the itinerant 5d and localized 4f electronic subsystems via the suppression of the magnetic (2 1 3−τ) satellite peak. We find demagnetization time scales very similar to ferromagnetic 4f systems, suggesting that the loss of magnetic order occurs via a similar spin-flip process in both cases. The simultaneous demagnetization of both subsystems demonstrates strong intra-atomic 4f−5d exchange coupling. In addition, an ultrafast lattice contraction due to the release of magneto-striction leads to a transient shift of the magnetic satellite peak.