title: Spin dynamics in iron-based layered superconductor (La0.87Ca0.13)FePO revealed by 31P and 139La NMR studies.
abstract: 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.
authors.affiliation: Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan. nakai@scphys.kyoto-u.ac.jp
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nakai
authors.forename: Kenji
authors.initials: K
authors.lastname: Ishida
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kamihara
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hirano
authors.forename: Hideo
authors.initials: H
authors.lastname: Hosono