Magnetoresistance of metallic perovskite oxide LaNiO${}_{3-\delta }$

Abstract

We report a study of the magnetoresistance (MR) of the metallic perovskite oxide LaNiO${}_{3-\delta }$ as a function of the oxygen stoichiometry $\delta$ ($\delta \le$ 0.14), magnetic field (H $\le 6T$) and temperature (1.5K $\le$ T $\le$ 25K). We find a strong dependence of the nature of MR on the oxygen stoichiometry. The MR at low temperatures change from positive to negative as the sample becomes more oxygen deficient (i.e, $\delta$ increases). Some of the samples which are more resistive, show a resistivity minima at $T_{min}$ $\approx$ 20K. We find that in these samples the MR is positive at T > $T_{min}$ and negative for T < $T_{min}$. We conclude that in the absence of strong magnetic interaction, the negative MR in these oxides can arise from weak localisation effects.

10 pages in REVTeX format, 4 eps figs