NMR study of local structure in metallicLa2CuO4+δ

Abstract

We employ ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$ NMR spectroscopy as a structural probe of metallic ${\mathrm{La}}_2$ ${\mathrm{CuO}}_{4+\mathrm{\delta }}$. We find a distribution of lateral displacements of the oxygen atoms which form the apices of the oxygen octahedra. We directly observe a wide distribution of structures of the La-O layer; this distribution is strongly temperature dependent. We present copper NQR spectra which reveal a second, unexplained, copper site in the ${\mathrm{CuO}}_2$ planes. We show that these features are not manifestations of disturbances of the lattice by interstitial dopants, but are the intrinsic response of ${\mathrm{La}}_2$ ${\mathrm{CuO}}_{4+\mathrm{\delta }}$ to doped holes.