Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 45: Superconductivity: Ferropnictides 2
TT 45.9: Vortrag
Freitag, 27. März 2009, 12:30–12:45, HSZ 03
Electronic properties of iron pnictides in the normal state probed by NMR — •Franziska Hammerath1, Guillaume Lang1, Hans-Joachim Grafe1, Dalibor Paar1,2, Katarina Manthey1, Nicholas Curro3, Günther Behr1, Jochen Werner1, and Bernd Büchner1 — 1IFW Dresden, Helmholtzstr. 20, D-01069 Dresden, Germany — 2Dept. of Physics, Faculty of Science, Univ. of Zagreb, P. O. Box 331, HR-10002 Zagreb, Croatia — 3Dept. of Physics, Univ. of California, Davis, CA 95616, USA
We have performed 75As, 139La, and 57Fe Nuclear Magnetic Resonance (NMR) measurements on the new LaO1−xFxFeAs superconductor. For x=0.1, NMR on all three nuclei shows that the local electronic susceptibility increases with increasing temperature in the normal state [1]. The scaling of all NMR shifts with respect to the macroscopic susceptibility indicates a single spin liquid. Relaxation measurements exhibit a similar temperature-dependence for (T1T)−1, and suggest that the dynamical susceptibility changes uniformly in q space with varying temperature. For x=0.05, in the underdoped regime, we find a Curie Weiss like increase of (T1T)−1 at low temperatures, indicating the onset of local moment fluctuations.
[1] H.-J. Grafe, G. Lang, F. Hammerath et al., arXiv:0811.4508, submitted to New Journal of Physics (invited paper, special issue on iron pnictides superconductors).