We have synthesized superconductive and nonsuperconductive samples of the n-type high-${\mathit{T}}_{\mathit{c}}$ superconducting system ${\mathrm{Nd}}_2$${\mathrm{CuO}}_{4\mathrm{-}\mathit{x}}$${\mathrm{F}}_{\mathit{y}}$ from the same batch. They give very similar normal state ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ NMR results, with decreasing spin-lattice relaxation time (${\mathit{T}}_1$) and the spin-spin relaxation time (${\mathit{T}}_{2\mathit{E}}$) and increasing negative line shift on decreasing temperature. Our results seem to indicate that the fluorine is more likely to be substituted into the O(2) sites between the Nd planes in this system. © 1996 The American Physical Society.

• Received 13 September 1995

DOI:https://doi.org/10.1103/PhysRevB.53.2265