SKM 2023 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 8: Ultrafast Magnetization Effects I

MA 8.3: Vortrag

Montag, 27. März 2023, 15:45–16:00, HSZ 04

Variation of magnetic model parameters during ultrafast demagnetisation — •S. Polesya, S. Mankovsky, and H. Ebert — Department Chemie, Ludwig Maximilian University, Munich, Germany

Recent developments in time-dependent density functional theory (TD-DFT) paved the way towards investigating the ultrafast demagnetisation caused by a strong laser pulse on an ab initio level. However, the relaxation processes after a pump pulse still require to use phenomenological models that allow to account for different types of relaxation mechanisms on the basis of model parameters, that can be calculated from first principles. A stumbling block for such schemes is that the electronic structure is strongly out of equilibrium after the laser pulse and changes with time due to the relaxation. In the present work, we explore whether the parameters which determine the magnetization dynamics in this time regime can indeed be described on a first-principles level. This concerns first of all the exchange coupling, magnetic anisotropy and the Gilbert damping parameters that have been calculated for several transition metals using the spin-polarized relativistic Korringa-Kohn-Rostoker method. To account for the time evolution of the system, the calculations have been performed employing the TD-DFT potentials and occupation numbers generated by the Elk code [http://elk.sourceforge.net] for different time steps during the laser pulse and shortly after it, i.e. in the non-relaxed situation. In all cases a strong modification of the parameters compared to the equilibrium situation is found.