Critical Current Characteristics and Flux Pinning in Fe-Based Pnictide Superconductor

Abstract:

The superconducting Ba_1-xK_xFe₂As₂ (x = 0.4) single crystals were prepared by the so-called FeAs self-flux method. The critical temperature by ac susceptibility measurement was estimated to be about 36 K. The magnetic field and temperature dependences of critical current densities were investigated by an ac inductive measurement (Campbell’s method). Unlike the phenomenon of co-existence of the global and local critical current densities observed in many polycrystalline Fe-based superconducting pnictides, it was found that only a uniform critical current density (J_c) flows through the whole sample. The value of J_c at 20 K and 1 T was about 5×10⁸ A/m², which is much smaller than the local critical current density observed in polycrystalline samples. This result implies that a dissimilarity of flux pinning mechanism exists between these two kinds of materials. The force-displacement characteristic of fluxoids in sample was investigated. The Labusch parameter was found to increase monotonously with increasing magnetic field, while the interaction distance was proportional to the fluxoid spacing. These results are consistent with the prediction based on a simple flux pinning mechanism.

• Periodical: Materials Science Forum (Volume 750)
• Pages: 288-292
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.750.288
• Online since: March 2013
• Authors: Bao Rong Ni, Edmund S. Otabe, Masaru Kiuchi, Yan Wei Ma
• Keywords: Ba-122 Single Crystal, Critical Current Density, Flux Pinning, Interaction Distance, Labusch Parameter

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