Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 27: Superconductivity: Fe-based Superconductors - 122
TT 27.12: Vortrag
Dienstag, 12. März 2013, 12:45–13:00, H18
Intrinsic ab-Plane Pinning in Epitaxial Pnictide Thin Films — •Jens Haenisch1, Kazumasa Iida1, Fritz Kurth1, Michael Schulze1, Sabine Wurmehl1, Shinya Ueda2, Michio Naito2, Chiara Tarantini3, Jan Jaroszynski3, Ludwig Schultz1, and Bernhard Holzapfel1 — 1IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany — 2Tokyo University A & T, Koganei, Tokyo 184-8588, Japan — 3NHMFL, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA
In type II superconductors with short coherence lengths ξ and large uniaxial crystallographic anisotropy, the order parameter may be modulated along the c-axis or even be restricted to superconducting planes. In such a case, flux lines may be pinned intrinsically by this modulation. This is well known for the high-Tc cuprates. The pnictides as well full-fill the conditions for intrinsic pinning. However, up to now it has not been reported. FeSe0.5Te0.5 thin films have been grown by PLD in a temperature series between 350 ∘C and 550 ∘C. For the film deposited at 450 ∘C we found clear signature of intrinsic pinning for B > 7 T and T < 4 K. Jc(B) is constant in this region and the V(I) exponent n shows a strong dip in its angular dependence for field orientations near ab. For the lowest T, n is rising again. This behavior is explained by trapping and lock-in of flux lines and the presence of double-kink excitations. An MBE-grown SmFeAs(O,F) thin film with very clean microstructure and a Tc of 55.7 K has been investigated in high static magnetic fields. This compound shows the same intrinsic-pinning behaviour for B > 35 T: constant Jc and a change of n(B,θ).