Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 2: Superconductivity: Fe-based Superconductors - 1111, LiFeAs & As-free Pnictides

TT 2.3: Vortrag

Montag, 26. März 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 T_c and the −dH_c2/dT at T_c. 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.