Nakai Yusuke, Ishida Kenji, Kamihara Yoichi, Hirano Masahiro, Hosono Hideo
Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Phys Rev Lett. 2008 Aug 15;101(7):077006. doi: 10.1103/PhysRevLett.101.077006.
We report 31P and 139La NMR studies of (La0.87Ca0.13)FePO, which is a family member of the recently discovered superconductor LaFeAs(O1-xFx). In the normal state, Knight shift and nuclear spin-lattice relaxation rate divided by T (1/T1T) show that a Fermi-liquid state with moderate ferromagnetic fluctuations emerges below 30 K. From 1/T1T of 31P and 139La, a quasi-two- dimensional electronic structure is suggested, in which the FeP layer is more conductive than the LaO layer. In the superconducting (SC) state, although a clear Meissner signal was observed, 1/T1T increases below Tc, in contrast to a decrease of 1/T1T due to the opening of a SC gap, suggesting that novel low-energy spin dynamics develop in the SC state.
