Synthesis and characterization of calcium-doped lanthanium nickelates La2-xCaxNiO4+delta (x=0, 0.02, 0.1, 0.275, 0.333, 0.5)

摘要

We have investigated the influence of Ca doping on chemical and physical properties of the La2NiO4+delta compounds. Several Ca-doped compounds were then prepared by the citrate method. The X-ray diffraction analysis indicates that all the obtained compounds are pure with no presence of secondary phases. All compounds adopt a tetragonal structure with 14/mmm space group. As x increases, the excess oxygen delta decreases. Magnetic susceptibility shows anomaly below 200 K, which was attributed to charge ordering. Magnetization measurements displayed prominently the presence of weak ferromagnetism below 200 K. Most probably, the ferromagnetic component modifies the anti ferromagnetic fluctuations in the NiO2 planes. The origin of the ferromagnetic component must be related to a presence of kind of bond-centered stripes. (c) 2005 Elsevier SAS. All rights reserved.