Insular superconductivity in Co-doped iron pnictide CaFe1-xCoxAsF
Abstract
The presence of macroscopic phase separation between the superconducting and magnetic phases in is demonstrated by muon spin rotation (muSR) measurements conducted across their phase boundaries (x=0.05-0.15). The magnetic phase tends to retain the high transition temperature (Tm > Tc), while Co-doping induces strong randomness. The volumetric fraction of superconducting phase is nearly proportional to the Co content x with constant superfluid density. These observations suggest the formation of superconducting "islands" (or domains) associated with Co ions in the Fe2As2 layers, indicating a very short coherence length.
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