Effect of Ga substitution on the superconducting properties of the electron-doped system: Nd-Ce-Cu-O.

Abstract

We are reporting on results of dc magnetization measurements of the new electron-doped ${\mathrm{Nd}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ce}}_{\mathrm{x}}$${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Ga}}_{\mathit{y}}$${\mathrm{O}}_{4}$ superconductors. The effect of ${\mathrm{Ga}}^{3+}$ on ${T}_{c}$ is similar to that of ${\mathrm{Ce}}^{4+}$, although the extra electron of the former comes from the Cu-O planes. For example, for x=0.12 the undoped compound (y=0) is not superconducting; but by the addition of Ga (y=0.03), the material becomes superconducting at ${T}_{c}$=20 K, and the Meissner fraction and the critical current density are improved compared to ${\mathrm{Nd}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_{4}$. The irreversibility line ${T}_{\mathrm{irr}(\mathrm{H})}$ for doped and undoped samples scales with the applied field as ${H}^{p}$, with p\ensuremath{\simeq}0.6, but for the Ga-doped sample it is pushed to higher temperatures.