Local structural analysis on the parent compound of iron-based superconductor PrFeAsO by atomic pair distribution function

Kodama, Katsuaki   ; Ishikado, Motoyuki*; Ikeda, Kazutaka*; Shamoto, Shinichi  ; Otomo, Toshiya*

We have performed neutron diffraction measurement on the parent compound PrFeAsO to investigate the local structure by using the atomic pair distribution function (PDF). The broad Pr-As atomic correlation peak observed in the PDF at 20 K cannot be reproduced by the averaged structure with space group , and can be reproduced by the structure model with space group , indicating the existence of the local lattice distortion with symmetry . In this work, the local structures of the parent compounds of other R1111 systems (R=rare earth) with different -values in the superconducting phases will be also studied to reveal the relationship between the local structure of the parent phase and the -value in the superconducting phase in the iron-based superconductor.