Abstract
We report the synthesis and characterization of new oxypnictides of the type Ce1−xYbxO0.9F0.1FeAs (‘x’=0.3, 0.4 and 0.5) for the first time. All these compounds crystallize in the tetragonal ZrCuSiAs type structure (space group: P4/nmm). Reduction in both the lattice parameters (a and c) was observed on substitution of smaller Yb ions at Ce sites in CeO0.9F0.1FeAs. All these compounds were found to be superconducting with maximum Tc of 48.7K for ‘x’=0.5 composition which is highest among Ce(O/F)FeAs based superconductors. Temperature dependence of resistivity under magnetic field has been studied to evaluate the upper critical field (Hc2(0)) of these superconductors. Enhancement in upper critical field (Hc2) was observed for these Yb doped Ce1−xYbxO0.9F0.1FeAs superconductors (max Hc2(0)=∼142T for ‘x’=0.3). The average coherence length of all Yb doped samples was estimated to be ∼23Å.
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