Mössbauer spectroscopy of La _0.87Ca _0.13FePO and LaFeAsO _0.93F _0.07 under external magnetic field and nuclear resonant inelastic scattering of La _0.87Ca _0.13FePO

An ⁵⁷Fe Mössbauer spectroscopic study of iron-based layered superconductors La _0.87Ca _0.13FePO and LaFeAsO _0.93F _0.07 under external magnetic fields of up to 14 T 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 _0.87Ca _0.13FePO and LaFeAsO _0.93F _0.07 is most likely to be paramagnetism with itinerant electrons. This feature is confirmed both above and below the transition temperature for LaFeAsO _0.93F _0.07. Furthermore, the temperature dependence of the iron-specific phonon density of states in La _0.87Ca _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 _0.87Ca _0.13FePO was smaller than that of LaFeAsO _0.89F _0.11.