Transport and localization in Nd2−xCexCuO4−y crystals at low doping

Abstract

We report in-plane transport properties of ${\mathrm{Nd}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Ce}}_{\mathit{x}}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$ crystals prepared in low-doped (x∼0.01–0.11), nonsuperconducting compositions. The large negative Hall coefficient ${\mathit{R}}_{\mathit{H}}$ and thermopower S in these samples confirm the presence of a small density of n-type carriers. At low T we find a highly anisotropic negative magnetoresistance which, together with the behavior of ρ, S, and ${\mathit{R}}_{\mathit{H}}$, demonstrates two-dimensional weak localization of these carriers occurring as Ce content decreases. Analysis of the magnetoresistance data reveals an anomalously weak T dependence of the electron inelastic-scattering rate 1/${\mathrm{\tau }}_{\mathit{i}}$.