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MA: Fachverband Magnetismus

MA 27: Magnetization / Demagnetization Dynamics I

MA 27.11: Vortrag

Mittwoch, 18. März 2015, 12:15–12:30, EB 301

Mechanisms of ultrafast phonon-driven demagnetization of a ferrimagnetic insulator — •Pablo Maldonado¹, Sebastian Mährlein², Ilie Radu³, Alex Paarmann², Michael Gensch⁴, Alexandra M. Kalashnikova⁵, Roman V. Pisarev⁵, Martin Wolf², Tobias Kampfrath², and Peter M. Oppeneer¹ — ¹Uppsala University, Sweden — ²Fritz Haber Institute of the Max Planck Society, Berlin — ³Helmholtz-Zentrum Berlin BESSY II, Berlin — ⁴Helmholtz-Zentrum Dresden-Rossendorf, Dresden — ⁵A.F. Ioffe Physical Technical Institute, St. Petersburg, Russia

We observe that the magnetization of the insulating ferrimagnet Y3Fe5O12 (YIG) is quenched following a resonant phonon excitation by a THz electromagnetic pulse. As electronic degrees of freedom are not excited, we expect that the complexity of the subsequent dynamics is considerably reduced as compared to ultrafast demagnetization of ferromagnetic metals. To gain more insight into microscopic processes leading to a phonon-driven demagnetization in YIG, we perform an ab initio study of the electronic structure and phonon modes of the system. We discuss possible microscopic mechanisms leading to ultrafast demagnetization, by considering two fundamental processes that couple lattice and magnetic order: i) direct coupling, where phonons decay into magnons through the spin-orbit coupling, and ii) phonon anharmonicities driving the system into a metastable state in which the structural changes trigger a modification of the orbital angular momenta.