A COMPARATIVE-STUDY OF THE CRYSTALLOGRAPHIC, MAGNETIC AND ELECTRICAL-PROPERTIES OF THE ND1-XLAXNIO3-DELTA SYSTEM

The synthesis and physical characterization of Nd1-xLaxNiO3-delta (from x = 0 to 1) samples are reported. Nd1-xLaxNiO3-delta samples are orthorhombic for x less-than-or-equal-to 0.4 and rhombohedral for x > 0.4. Resistivity and magnetic susceptibility measurements from 4.2 K to 300 K are also reported. The increase of La content up to x = 0.4 induces the decrease of metal-insulator (MI) phase transition temperature and compounds with x greater-than-or-equal-to 0.5 are metallic. The distortion degree of the ideal perovskite structure, directly related to the Ni-O-Ni angle, is correlated with the MI phase transition temperature. The metallic phase is characterized by a linear dependence of rho(T) with a residual resistivity that decreases with x, being near zero for LaNiO3. The conductivity in the semiconducting phases at low temperatures follows a variable-range hopping mechanism. The magnetic susceptibility shows a Curie-Weiss contribution from the Nd sublattice and a Pauli susceptibility of similar magnitude for all samples. The analysis of the experimental data shows large electronic correlations in these compounds.