Local antiferromagnetic correlations in the iron pnictide superconductors LaFeAsO1-xFx and Ca(Fe1-xCox)(2)As-2 as seen via normal-state susceptibility

We have studied the interplay of magnetism and superconductivity in LaFeAsO1-xFx and Ca(Fe1-xCox)(2)As-2. While antiferromagnetic spin-density wave formation is suppressed and superconductivity evolves, all samples show a doping-independent strong increase in the normal-state susceptibility upon heating which appears a general feature of iron pnictides. The data provide evidence for robust local antiferromagnetic correlations persisting even in the superconducting regime of the phase diagram.