Evolution of superconductivity in PrFe1−xCoxAsO (x=0.0–1.0)

We report the synthesis and physical property characterization of PrFe1−xCoxAsO (x=0.0–1.0). The studied samples are synthesized by through the solid state reaction route via the vacuum encapsulation method. The pristine compound PrFeAsO does not show superconductivity, but rather exhibits a metallic step like transition due to spin density wave (SDW) ordering of Fe moments (FeSDW) below 150 K, followed by another upward step due to anomalous ordering of Pr moments (PrTN) at 12 K. Both the FeSDW and PrTN temperatures decrease monotonically with Co substitution at Fe site. Superconductivity appears in a narrow range of x from 0.07 to 0.25 with maximum Tc at 11.12 K for x=0.15. Samples with x≥0.25 exhibit metallic behavior right from 300 K down to 2 K, without any FeSDW or PrTN steps in resistivity. In fact, though FeSDW decreases monotonically, the PrTN disappeared even with x=0.02. The magneto transport measurements below 14 T on superconducting polycrystalline Co doped PrFeAsO lead to extrapolated values of the upper critical fields [Hc2(0)] of up to 60 T.