STRUCTURE, MAGNETIC AND ELECTRICAL-PROPERTIES IN ND1-XLAXNIO3 SYSTEM

The phase diagram of the Nd1-xLaNiO3 system has been studied. The samples were synthesized using a sol-gel method and low sintering temperatures under oxygen. They have been characterized as pure phases by means of X-ray diffraction patterns. The crystal structure of the LaNiO3 is the known rhombohedral perovskite while NdNiO3 crystallizes in the GdFeO3 orthorhombic structure. The structural transition in the intermediate solutions occurs for compositions between Nd0.5La0.5NiO3 (rhombohedral) and Nd0.6La0.4NiO3 (orthorhombic). The ac susceptibility performed on these samples from 4.2 K to 300 K, shows a continuous variation from the Pauli paramagnetic behaviour of LaNiO3 to the like Curie-Weiss paramagnetic behaviour of NdNiO3. Resistivity measurements from 4.2 K to 300 K were carried out using the standard four-probe method. Samples with x = 1 to 0.6 show metallic behaviour in the whole temperature range. The resistivity curves of the samples with x = 0. 5 and x = 0.4 exhibits a minimum at low temperatures (T almost-equal-to 10 K), while the samples with x less-than-or-equal-to 0.3 show a semiconductor-metal phase transition with a large thermal hysteresis. The transition temperature and extent of the hysteresis cycle increases with the Nd content.