Berlin 2012 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 2: Superconductivity: Fe-based Superconductors - 1111, LiFeAs & As-free Pnictides
TT 2.3: Talk
Monday, March 26, 2012, 10:00–10:15, H 2053
Physics of defect induced local moments in pnictide superconductors — •Vadim Grinenko1, Stefan-Ludwig Drechsler1, Konstatin Kikoin2, Mahmoud Abdel-Hafiez1, Saicharan Aswartham1, Anja Wolter-Giraud1, Christian Hess1, Manoj Kumar1, Sabine Wurmehl1, Guenter Fuchs1, Konstantin Nenkov1, Franziska Hammerath1, Guillaume Lang1, Hans-Joachim Grafe1, Bernhard Holzapfel1, Jeroen van den Brink1, Bernd Buechner1, and Ludwig Schultz1 — 1IFW-Dresden, D-01171 Dresden, Germany — 2School of Physics and Astronomy, Tel-Aviv University , Tel-Aviv, Israel
Many unusual physical properties of Fe-pnictide superconductors are related to the presence of local magnetic moments induced by point-defects, e.g. As-vacancies. In the La-1111 system they improve the superconducting properties as compared with As-stoichiometric samples enhancing Tc and the −dHc2/dT at Tc. But they also enhance strongly the spin susceptibility, which governs the Pauli limiting behavior of the As-deficient La-1111. In heavily hole doped K-122 superconducting single crystals the local moments leads to a complex phase diagram with a Griffith and a spin glass phase. The local moments picture explains also the observed non-Fermi-liquid behavior and the large effective mass enhancement of the quasi-particles in K-122. In Co-doped Ba-122 superconducting single crystals the local moments form also a spin glass state and lead to a strong Pauli limiting behavior.