A reexamination of19F NMR in selected solids, the conductor Ag2F and Reference Insulators for studies of YBa2Cu3O7-type superconductors

Abstract

NMR signals of ~gF have been measured in the polycrystalline inorganic conductor Ag2F and in the polycrystalline insulators AgF, YOF, EuOF, YF3, CuF2, BaF 2 and KF to compare them to the signals found in the so-called ~~l-2-3-type~~ compounds with claimed formulas RBa2Cu3OT.xF ~ (R=Y and Eu). No evidence for a Knight-shifted, built-in fluorine-signal was found in the 1-2-3-type superconductors, whereas Ag2F shows a clearly downfield shifted ~gF peak with reference to AgF.