Berlin 2024 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 46: Poster II

MA 46.51: Poster

Donnerstag, 21. März 2024, 15:00–18:00, Poster C

Changes of the spin-spin and spin-lattice interaction induced by a ultrashort laser pulse — •Sergiy Mankovsky, Svitlana Polesya, and Hubert Ebert — Dept. Chemistry, LMU Munich, Butenandtstr. 11, D-81377 Munich, Germany

Ultrafast demagnetization implies complex dynamics concerning the electron, spin, and lattice degrees of freedom, coupled to each other and all being out-of-equilibrium after the laser pulse. The pure electron dynamics induced by a ultrashort laser pulse is well described within the time-dependent density functional theory (TD-DFT). However, spin and lattice excitations as well as interactions between all degrees of freedom are usually described making use of model Hamiltonians. The evolution of the spin system described using the Landau-Lifshitz-Gilbert equations is determined by the torque on the magnetic moments, stemming from different types of interactions entering the spin and spin-lattice Hamiltonian. The corresponding interaction parameters are determined by the electronic structure and can be calculated on a first-principles level. This implies that they should change together with the laser induced changes of the electronic structure. We will discuss the possible impact of such changes on the demagnetization dynamics, focusing on the isotropic exchange and different types of spin-lattice interactions. Their calculations have been performed employing 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. As is demonstrated for various systems, a strong modification of the parameters is found.

Keywords: ultrafast demagnetization; LLG equation; TD-DFT; exchange coupling; spin-lattice interactions