title: Intrinsic and extrinsic pinning in NdFeAs(O,F): vortex trapping and lock-in by the layered structure.
abstract: Fe-based superconductors (FBS) present a large variety of compounds whose properties are affected to different extents by their crystal structures. Amongst them, the REFeAs(O,F) (RE1111, RE being a rare-earth element) is the family with the highest critical temperature Tcbut also with a large anisotropy and Josephson vortices as demonstrated in the flux-flow regime in Sm1111 (Tc∼ 55 K). Here we focus on the pinning properties of the lower-TcNd1111 in the flux-creep regime. We demonstrate that for H//c critical current density Jcat high temperatures is dominated by point-defect pinning centres, whereas at low temperatures surface pinning by planar defects parallel to the c-axis and vortex shearing prevail. When the field approaches the ab-planes, two different regimes are observed at low temperatures as a consequence of the transition between 3D Abrikosov and 2D Josephson vortices: one is determined by the formation of a vortex-staircase structure and one by lock-in of vortices parallel to the layers. This is the first study on FBS showing this behaviour in the full temperature, field, and angular range and demonstrating that, despite the lower Tcand anisotropy of Nd1111 with respect to Sm1111, this compound is substantially affected by intrinsic pinning generating a strong ab-peak in Jc.
authors: Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, Tallahassee FL 32310, USA.
authors: C
authors: C
authors: Tarantini
authors: Institute for Metallic Materials, IFW Dresden, 01171 Dresden, Germany.|Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
authors: K
authors: K
authors: Iida
authors: Institute for Metallic Materials, IFW Dresden, 01171 Dresden, Germany.|Institute for Technical Physics, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany.
authors: J
authors: J
authors: Hänisch
authors: Institute for Metallic Materials, IFW Dresden, 01171 Dresden, Germany.|Dresden University of Technology, Faculty for Natural Science and Mathematics, 01062 Dresden, Germany.
authors: F
authors: F
authors: Kurth
authors: Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, Tallahassee FL 32310, USA.
authors: J
authors: J
authors: Jaroszynski
authors: Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
authors: N
authors: N
authors: Sumiya
authors: Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
authors: M
authors: M
authors: Chihara
authors: Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
authors: T
authors: T
authors: Hatano
authors: Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
authors: H
authors: H
authors: Ikuta
authors: Friedrich-Schiller-University Jena, Institute of Solid State Physics, 07743 Jena, Germany.
authors: S
authors: S
authors: Schmidt
authors: Friedrich-Schiller-University Jena, Institute of Solid State Physics, 07743 Jena, Germany.
authors: P
authors: P
authors: Seidel
authors: Institute for Technical Physics, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany.
authors: B
authors: B
authors: Holzapfel
authors: Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, Tallahassee FL 32310, USA.
authors: D C
authors: DC
authors: Larbalestier