Regensburg 2016 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 10: Thyssen-Krupp Electrical Steel Ph. D. Thesis Award (Dissertationspreis)

MA 10.1: Hauptvortrag

Montag, 7. März 2016, 15:00–15:25, H32

Magnetization Dynamics of Itinerant and Localized Electrons in Lanthanide Metals — •Björn Frietsch — Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin

Magnetization Dynamics of Itinerant and Localized Electrons in Lanthanide Metals Laser induced magnetization dynamics is a very active field of research, not only because of its technological importance but also based on the insights it offers into the fundamental processes that contribute to the transfer of angular momentum from and to the spin system.

To investigate these processes during laser-driven demagnetization we chose the lanthanide metal gadolinium. Using time- and angle-resolved photoelectron spectroscopy we are able to follow the evolution of the exchange-split split valence band-structure which is a measure of the short-range magnetic order of the itinerant 5d6s electrons as well as the magnetization of the localized 4f core level via magnetic linear dichroism. This way we found strikingly different demagnetization time constants of 0.8 ps and 14 ps for the 5d6s and the 4f electrons, respectively. This remarkable difference demonstrates a perturbation even beyond the strong intra-atomic exchange interaction which -- thus far -- was believed to act on a timescale of a few femtoseconds.

Spin dynamics simulations based on an orbital-resolved Heisenberg Hamiltonian combined with first-principles calculations explain the particular dynamics of 5d6s and 4f spin moments well and suggest that the slow demagnetization of the 4f spin system is almost exclusively driven by phonon-magnon scattering.