Lower Critical Fields and the Anisotropy in PrFeAsO1-y Single Crystals

By utilizing miniature Hall-sensor array, we evaluated the lower critical fields H_c1 in Fe-based oxipnictide PrFeAsO_1-y single crystals for Hc and Hab-planes. The temperature dependence of H_c1 for Hc is well scaled by the in-plane penetration depth and is consistent with a full-gap superconducting state. The anisotropy of penetration depths at low temperatures is estimated to be ∼ 3, which is much smaller than that of coherence lengths. This indicates the multiband superconductivity, in which the active band for the superconductivity is more anisotropic.