Disorder effects and current percolation in FeAs based superconductors

Abstract

We report the influence of atomic disorder introduced by sequential neutron irradiation on the basic superconducting properties, flux pinning and grain connectivity. Two different polycrystalline Sm-1111 samples (SmFeAsO_{1-x}F_x) and two Ba-122 single crystals (BaFe_{1.8}Co_{0.2}As_2) were investigated. The monotonous decrease of the transition temperature with neutron fluence degrades the upper critical field, at least in the investigated temperature region. Pinning on the other hand is largely improved, with a different optimal defect concentration (fluence) in the two materials. The analysis of the current flow in the polycrystalline samples reveals weak link behaviour in the majority of grain connections and the existence of stronger grain connections. The density of the latter seems to be close to the percolation threshold (i.e. the minimum fraction for a continuous current path). Both types of connections are sensitive to disorder and degrade upon neutron irradiation.

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Cited by in corpus (6)

• Mechanochemical synthesis of pnictide compounds and superconducting Ba0.6K0.4Fe2As2 bulks with high critical current density
• Evidence for electromagnetic granularity in polycrystalline Sm1111 iron-pnictides with enhanced phase purity
• Percolative superconductivity in La2CuO4.06 by lattice granularity patterns with scanning micro X-ray absorption near edge structure
• Anisotropic critical currents in FeSe0.5Te0.5 films and the influence of neutron irradiation
• Anomalous Tail Effect on Resistivity Transition and Weak-link Behavior of Iron Based Superconductor
• On the trapped magnetic moment in type-II superconductors