Lower Critical Fields and the Anisotropy in PrFeAsO$_{1-y}$ 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 {\boldmath $H$}$\parallel c$ and {\boldmath $H$}$\parallel ab$-planes. The temperature dependence of $H_{c1}$ for {\boldmath $H$}$\parallel c$ 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 $\simeq$ 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.