Mossbauer Spectroscopy of La_<0.87>Ca_<0.13>FePO and LaFeAsO_<0.93>F_<0.07> under External Magnetic Field and Nuclear Resonant Inelastic Scattering of La_<0.87>Ca_<0.13>FePO(Condensed matter: electronic structure and electrical, magnetic, and optical prop

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An ^<57>Fe Mossbauer spectroscopic study of iron-based layered superconductors La_<0.87>Ca_<0.13>FePO and LaFeAsO_<0.93>F_<0.07> under external magnetic fields of up to 14T was performed. Our results suggest that hyperfine fields induced by local magnetic moments are, if any, small and that the magnetic feature of Fe in La_<0.87>Ca_<0.13>FePO and LaFeAsO_<0.93>F_<0.07> is most likely to be paramagnetism with itinerant electrons. This feature is confirmed both above and below the transition temperature for LaFeAsO_<0.93>F_<0.07> Furthermore, the temperature dependence of the iron-specific phonon density of states in La_<0.87>Ca_<0.13>FePO was measured by using the nuclear resonant inelastic scattering of synchrotron radiation. We have found that the temperature-dependent change in the iron-specific phonon density of states of La_<0.87>Ca_<0.13>FePO was smaller than that of LaFeAsO_<0.89>F_<0.11>.
社団法人日本物理学会の論文
2009-02-15