Magnetoresistance of metallic perovskite oxide LaNiO3−δ

We report a study of the magnetoresistance (MR) of the metallic perovskite oxide LaNiO3−δ as a function of the oxygen stoichiometry δ (δ ≤ 0.14), magnetic field ( H ≤ 6T ) and temperature (1.5K ≤ T ≤ 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, δ increases). Some of the samples which are more resistive, show a resistivity minima at Tmin ≈ 20K. We find that in these samples the MR is positive at T ¿ Tmin and negative for T ¡ Tmin. We conclude that in the absence of strong magnetic interaction, the negative MR in these oxides can arise from weak localisation effects. [email protected] On lien to National Physical Laboratory, New Delhi 110012, India.