title: 75As NMR study of overdoped CeFeAsO0.8F0.2.
abstract: We report on the results from a (75)As nuclear magnetic resonance (NMR) study of the overdoped iron pnictide superconductor CeFeAsO0.8F0.2. We find two As sites with different shifts at temperatures as high as 100 K, which is above the superconducting transition temperature of 39 K, and hence they cannot be attributed to the effect of vortices in the superconducting state as previously suggested (Ghoshray et al 2009 Phys. Rev. B 79 144512). The much larger spin-lattice relaxation rate compared with that found in other pnictides without magnetic rare earth ions, and the temperature dependence of the (75)As NMR shifts for the two central lines, are consistent with the hyperfine coupling from magnetic Ce to As. The low temperature spectra indicate that there are As ions with two different quadrupole splittings. Our findings appear to be consistent with an electronic phase segregation into regions with two different F dopings or the presence of a correlated spatial charge and spin density variations.
authors.affiliation: Faculty of Physics and Earth Science, University of Leipzig, Leipzig, Germany. rybicki@physik.uni-leipzig.de
authors.forename: Damian
authors.initials: D
authors.lastname: Rybicki
authors.forename: Thomas
authors.initials: T
authors.lastname: Meissner
authors.forename: Grant V M
authors.initials: GV
authors.lastname: Williams
authors.forename: Shen V
authors.initials: SV
authors.lastname: Chong
authors.forename: Marc
authors.initials: M
authors.lastname: Lux
authors.forename: Jürgen
authors.initials: J
authors.lastname: Haase