Berlin 2015 – scientific programme
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MA: Fachverband Magnetismus
MA 27: Magnetization / Demagnetization Dynamics I
MA 27.11: Talk
Wednesday, March 18, 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.