Metal-insulator transition and magnetic properties of La(1-x)Eu(x)NiO₃ (0 ≤ x ≤ 1)

This paper reports X-ray diffraction patterns, Rietveld fit profiles, electrical resistivity dc magnetic susceptibility, and electron paramagnetic resonance (EPR) measurements of La(1-x)EU(x)NiO₃ (0 ≤ x ≤ 1). A shift to high temperature of the metal-insulator transition temperature with x and hysteresis in the electrical resistivity and magnetization versus temperature at intermediate concentration of the compound are observed. The antiferromagnetic order of the Ni sublattice can be observed after subtracting the magnetic contribution of the rare earth ions. A change in space group from R-3c to Pbnm for x ≥ 0.4 was detected, as was the appearance of magnetic order. Samples with 1% Gd³⁺ probe were studied by EPR. Drastic changes were observed in the shape of the lines with x, though the crystal field symmetry of the Gd sites remained constant in all the samples studied. We observed that when Eu substitution increases, the number of Gd ions that contribute to the crystal-field spectrum diminishes. A possible cause of this effect is a previously reported increase in the Ni-O covalence in the neighborhood of the Eu sites. (C) 2000 Academic Press.