Chandra Shekhar, Amit Srivastava, Pramod Kumar, Pankaj Srivastava, O. N. Srivastava
In this paper, we report the synthesis, structure, transition temperature,
upper critical field, critical current density and thermally activated flux
flow in CaFFe0.9Co0.1As superconductor. Superconductivity arises at 23 K by Co
substitution at the site of Fe atoms and upper critical field is estimated 102
T by using the Werthamer-Helfand-Hohenberg formula. The flux-flow activation
energy (U0/kB) varies from 3230 K and 4190 K in the field of 1 T and 9 T
respectively. At 2K, the Jc is found to be approximately 4x10^3A/cm^2 and
0.3x10^3 A/cm&^2 in zero and 6T field, respectively. Transmission electron
microscopy analysis shows an amorphous region surrounding around most of the
grains which is likely to be present in the form of amorphous and weak link
grain boundaries in this compound. It seems that most of the current is
hindered by miss aligned grains, amorphous grain boundaries and impurities,
which are invariably found between the grains. Presence of the weakly linked
granules and their weakly pinned intergranular Josephson vortices are
responsible for both low Jc and the Arrhenius temperature dependence of
resistivity
View original:
http://arxiv.org/abs/1202.1473
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