Intrinsic and extrinsic pinning in NdFeAs(O,F): vortex trapping and lock-in by the layered structure

Abstract

The Fe-based superconductors (FBS) present a large variety of compounds whose properties are affected to different extents by their crystal structures. Amongst them, the $RE$FeAs(O,F) ($RE$1111, where $RE$ is a rare earth element) is the family with the highest critical temperature $T_c$ but also with a large anisotropy and Josephson vortices as demonstrated in the flux-flow regime in Sm1111 ($T_c$ $\sim$ 55 K). Here we focus our attention on the pinning properties of the lower-$T_c$ Nd1111 in the flux-creep regime. We demonstrate that for H//c critical current density $J_c$ at 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 the vortices parallel to the layers. This is the first study on FBS showing this behaviour in a full temperature, field, and angular range and it demonstrates that, despite the lower $T_c$ and anisotropy of Nd1111 with respect to Sm1111, this compound is substantially affected by intrinsic pinning generating a strong $ab$-peak in $J_c$.

Final version available on Scientific Reports (Open access)

References in corpus (11)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• High-temperature superconductivity in iron-based materials
• Very High Field Two-Band Superconductivity in LaFeAsO_0.89F_0.11
• Upper critical fields and thermally-activated transport of Nd(O_0.7F_0.3)FeAs single crystal
• Critical Fields and Anisotropy of NdO0.82F0.18FeAs Single Crystals
• Scaling behaviour of the critical current in clean epitaxial Ba(Fe1-xCox)2As2 thin films
• Critical current scaling and anisotropy in oxypnictide superconductors
• Intrinsic pinning and the critical current scaling of clean epitaxial Fe(Se,Te) thin films
• Evidence for two distinct anisotropies in the oxypnictide superconductors SmFeAsO_(0.8)F_(0.2) and NdFeAsO_(0.8)F_(0.2)
• Development of very high Jc in Ba(Fe1-xCox)2As2 thin films grown on CaF2
• Artificial and self-assembled pinning centers in Ba(Fe1-xCox)2As2 thin films as a route to very high current density

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• New scaling laws for pinning force density in superconductors
• Nanoscale Texture and Microstructure in NdFeAs(O,F)/IBAD-MgO Superconducting Thin Film with Superior Critical Current Properties
• High $J_{\mathrm{c}}$ and low anisotropy of hydrogen doped NdFeAsO superconducting thin film
• Status of Iron Based Superconductors: characteristics and relevant properties for applications
• Intrinsic pinning of FeSe${}_1$${}_{-}$${}_x$S${}_x$ single crystals probed by torque magnetometry
• Grain boundary characteristics of oxypnictide NdFeAs(O,F) superconductors