RE L3 X-ray absorption study of REO1−xFxFeAs

Rare-earth L3-edge X-ray absorption near edge structure (XANES) spectroscopy has been used to study REOFeAs (RE=La, Pr, Nd, Sm) oxypnictides. The Nd L3 XANES due to 2p3/2 →5d transition shows a substantial change in both white line (WL) spectral weight and the higher energy multiple scattering resonances with the partial substitution of O by F. A systematic change in the XANES features is seen due to varying lattice parameters with ionic radius of the rare earth. On the other hand, we hardly see any change across the structural phase transition. The results provide timely information on the local atomic correlations showing importance of local structural chemistry of the REO spacer layer and interlayer coupling in the competing superconductivity and itinerant striped magnetic phase of the oxypnictides. PACS numbers: 61.05 Cj;74.62 Bf;74.81-g a