Effects of Zn substitution for Cu on superconducting and normal-state properties of (La,Sr)2CuO4, (Nd,Ce,Sr)2CuO4, and (Nd,Ce)2CuO4.

Abstract

Superconducting and normal-state properties of Zn-doped samples of ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Zn}}_{\mathit{x}}$${\mathrm{O}}_{4\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (T phase), ${\mathrm{Nd}}_{1.4}$${\mathrm{Ce}}_{0.2}$${\mathrm{Sr}}_{0.4}$${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Zn}}_{\mathit{x}}$${\mathrm{O}}_{4\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (${\mathit{T}}^{\mathrm{*}}$ phase), and ${\mathrm{Nd}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Zn}}_{\mathit{x}}$${\mathrm{O}}_{4\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (T' phase) are investigated for Zn content x in the range of 0--0.04. Zn doping alters the lattice parameters for the T and ${\mathit{T}}^{\mathrm{*}}$ phases but does not for the T' phase. For all of the T, ${\mathit{T}}^{\mathrm{*}}$, and T' phases, ${\mathit{T}}_{\mathit{c}}$, the Meissner signal, and the shielding signal monotonically decrease for increasing x. From the magnetic-susceptibility measurement, it is suspected that isolated Cu spins are induced around doped Zn in the T phase. As the Zn content increases, the magnitude of the Hall coefficient decreases in both T and T' phases, while the carrier density, estimated from a chemical analysis, remains constant. Possible mechanisms for this are discussed.