Regensburg 2013 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 15: Spintronics and Magnetic Semiconductors (jointly with HL)
MA 15.9: Vortrag
Dienstag, 12. März 2013, 11:30–11:45, H3
Tuning the ultrafast magnetic dynamics in Gd-Doped EuO — •A. Schroer1, M. Matsubara2, A. Schmehl3, J. Mannhart4, A. Melville5, D. G. Schlom5, M. Trujillo Martinez1, M. Fiebig2, and J. Kroha1 — 1Universität Bonn — 2ETH Zürich — 3Universität Augsburg — 4MPI-FF Stuttgart — 5Cornell University
EuO is a dense ferromagnetic semiconductor with a Curie temperature of TC=69 K. Upon Gd-doping, Eu1−xGdxO undergoes a simultaneous ferromagnetic and insulator-metal transition, with a resistivity drop of several orders of magnitude, making it an interesting material or spintronics applications. The magnetic coupling Jeff between the Eu 4f moments is mediated by a virtual magnetic exciton (Eu 4f-5d mixing), enhancing the wave function overlap of the magnetic Eu orbitals. We show by pump-probe experiments that pumping electrons resonantly into the Eu 5d conduction band in pure EuO leads to an ultrafast increase of the ferromagnetic coupling Jeff, and that this coupling can be tuned from a further increase to a decrease by Gd doping. For this pump-induced non-equilibrium situation we calculate the RKKY-like, conduction electron induced magnetic coupling. We find that the magnetic interaction is in general oscillatory and decays spatially with a power law, like the equilibrium RKKY interaction, but the power law exponent is changed. The tuning of the pump-induced change of Jeff by Gd-doping is explained by a subtle interplay of correlation-induced shift of spectral weight and of a pump-induced redistribution of the conduction electron occupation.