Structure and Magnetic Properties of Gd_2-xSr_xNiO₄, a Ruddlesden-Popper type solid solution

Gd_2-xSr_xNiO₄ complex oxide of the Ruddlesden-Popper series, was first prepared by James, M. et al.[1] Several compositions of the Gd_2-xSr_xNiO₄ system were prepared by the complex polymeric route (Pechini). In this work we report the Sr composition stability range for this solid solution. Crystal structure of samples in the 0.75≤x≤1.25 range, were studied by Rietveld structure refinements. Magnetic measurements of samples (2-300 K) show a Curie-Weiss paramagnetic behavior for all x compositions, with a weak antiferromagnetic coupling. Electrical properties were measured in the 20-300 K range and we found that this system displays a metal-insulator transition for x≥1.0. Spectroscopic data (UV-Vis-NIR) at room temperature and magnetic moment measurements of this system reveal the nature of Ni oxidation states of this system.

[1] M. James, J.P. Attfield, Synthesis, crystal structure and magnetic properties of Ln_2–xSr_xNiO_4±δ solid solutions (Ln = La, Nd, Sm and Gd; 1.0≤x≤1.67), J. Mater. Chem. 6 (1996) 57–62.