Detailed measurements of the global and local electromagnetic properties of Ba(Fe0.93Co0.07)2As2 single crystals are reported. Analysis of the irreversible magnetic response provides strong evidence for similar vortex physics in this Fe-based pnictide superconductor to the high-Tc cuprates, such as Y-Ba-Cu-O or Nd-Ce-Cu-O. In particular, we have found a nonmonotonic "fishtail" magnetization in M(H,T=const) loops and its signature is also present in M(H=const,T) scans. The supercurrent density is evaluated by using several techniques, including direct transport measurements. At 5 K we estimate its value to be a moderate j≈2.6±0.2×105 A/cm2. Analysis of the magnetic relaxation is consistent with the collective pinning and creep models (weak pinning and fast creep) and suggests a crossover from the collective to the plastic creep regime in fields exceeding the value corresponding to the maximum in fishtail magnetization.
@article{arxiv.0810.1338,
title = {Vortex phase diagram of Ba(Fe0.93Co0.07)2As2 single crystals},
author = {R. Prozorov and N. Ni and M. A. Tanatar and V. G. Kogan and R. T. Gordon and C. Martin and E. C. Blomberg and P. Prommapan and J. Q. Yan and S. L. Bud'ko and P. C. Canfield},
journal= {arXiv preprint arXiv:0810.1338},
year = {2009}
}