Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 23: Spinabh
ängiger Transport III
MA 23.4: Vortrag
Dienstag, 8. März 2005, 11:15–11:30, TU H1028
Disorder-induced resistive anomaly near ferromagnetic phase transitions — •Carsten Timm1, M.E. Raikh2, and Felix von Oppen1 — 1Institut für Theoretische Physik, Freie Universität Berlin — 2Department of Physics, University of Utah, Salt Lake City, U.S.A.
The resistive anomaly in disordered itinerant ferromagnets has a long history, dating back to the first observation by Gerlach in 1932. In 1968, Fisher and Langer proposed a theory for this anomaly based on anomalous scaling. We show that the resistivity ρ(T) can exhibit a stronger singularity than predicted in that work. Close to the Curie temperature Tc the correlation length becomes large compared to the mean free path. Then, the quenched disorder is probed by diffusive carriers, which requires one to go beyond the Boltzmann description used in all previous works. Our approach combines ideas from the theory of random media and from mesoscopic physics. Specifically, we find that dρ/dT scales as |T−Tc|−1/2 assuming Gaussian magnetic fluctuations. Our results are relevant for ferromagnets with low Tc, such as SrRuO3 or diluted magnetic semiconductors, whose mobility near Tc is limited by disorder.