Superconducting and critical properties of PrOFe_0.9Co_0.1As: effect of P doping

PrOFe_0.9Co_0.1As is known to be a superconductor with a T_C of ∼ 14 K. In an attempt to induce charge transfer and also induce chemical pressure between the FeAs and PrO layers we have synthesized for the first time oxypnictides of the type PrOFe_0.9Co_0.1As_{1 − x}P_x (P doping at As sites). All the compounds crystallize in the tetragonal ZrCuSiAs-type structure (space group = P4/nmm). The lattice parameters (a and c) decrease as expected on substitution of smaller phosphorus at the arsenic site in PrOFe_0.9Co_0.1As and a decrease in T_C was observed on substitution of P ions at a low rate of 0.13 K/at.% of P for x > 0.1. The irreversibility field (H_irr) and critical current density (J_C), obtained using the AC susceptibility measurements, were found to decrease monotonically with increasing P concentration. H_irr is observed to be much smaller than H_C2, pointing to a very low pinning energy. The pinning potential obtained using both in-field transport and AC susceptibility measurements indicates a low value of ∼ 40 meV and shows no significant variation with P substitution.