Anisotropy in Superconductivity and Magnetism of PrFeAsO1−δ Single Crystal

The magnetic torque of a high-quality PrFeAsO1−δ single crystal has been investigated at temperatures from 2 to 200 K in 1 and 5 T. The superconducting anisotropy in PrFeAsO1−δ can well be approximated by the single-band Kogan torque theory. The superconducting anisotropy of PrFeAsO1−δ determined by analyzing the torque curve is weakly dependent upon changing temperature. The magnetism contribution to the torque from magnetic Pr ions becomes appreciable compared to the superconducting component. We argue that the Pr ions in the superconducting PrFeAsO1−δ single crystal show an antiferromagnetic spin ordering at 14 K. The spin structure thus reduced from the torque measurements is different from what neutron diffraction measurements predicted using polycrystalline specimen.