Regensburg 2016 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 31: Magnetization and Demagnetization Dynamics II
MA 31.12: Vortrag
Mittwoch, 9. März 2016, 12:30–12:45, H34
Nonequilibrium magnetization dynamics beyond the three temperature model — •Karel Carva1, Pavel Balaz1, Peter Oppeneer2, and Pablo Maldonado2 — 1Charles University in Prague, DCMP, Ke Karlovu 5, CZ-12116, Prague, Czech Republic — 2Uppsala University, PO Box 516, 75120 Uppsala, Sweden
Femtosecond magnetization dynamics has been commonly described employing the three temperature model, without verifying its validity. We show when it fails to describe correctly the specific subsystems.
For Gd metal we calculate from first principles exchange interaction between atomic moments, as well as the intra-atomic exchange between Gd 4f and 5d orbitals. Spin dynamics solution of the corresponding effective orbital-resolved Heisenberg Hamiltonian has shown disparate magnetization dynamics of the 4f and 5d moments, in a good agreement with the experiment [1]. The magnetic state here cannot be assigned one temperature for times up to 100 ps.
In order to study lattice behavior we calculate the electron-phonon scattering rates for systems with high electronic temperature [2], and phonon lifetimes due to phonon-phonon scattering. From this we obtain phonon population that differs sharply from the thermal one within picoseconds after the pump. This allows to understand recent experimental observations and disproves the applicability of the model based on one lattice temperature here [3].
1. Frietsch, B. et al. , Nat Commun 6, 8262 (2015).
2. Carva, K. et al., Phys. Rev. B 87, 184425 (2013).
3. Henighan T. et al., arXiv: 1509.03348