"Hot-Electron-Driven Enhancement of Spin-Lattice Coupling in Gd and Tb 4f Ferromagnets Observed by Femtosecond X-Ray Magnetic Circular Dichroism"

Marko Wietstruk: Alexey Melnikov, Christian Stamm, Torsten Kachel, Niko Pontius, Muhammad Sultan, Cornelius Gahl, Martin Weinelt, Hermann A. Dürr, and Uwe Bovensiepen; Phys. Rev. Lett. , 03/21/11.

Additional Authors: Alexey Melnikov, Christian Stamm, Torsten Kachel, Niko Pontius, Muhammad Sultan, Cornelius Gahl, Martin Weinelt, Hermann A. Dürr, and Uwe Bovensiepen

Abstract:

Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent magnetic moment of 4f electrons in the ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast demagnetization time of 750 fs identical for both systems and slower times which differ sizeably with 40 ps for Gd and 8 ps for Tb. We conclude that spin-lattice coupling in the electronically excited state is enhanced up to 50 times compared to equilibrium.