The synthesis, structural characterization and magnetic properties of compounds in the Ln2O3-SrO-NiO-CuO system for Ln = La, Nd, Gd, Dy, Ho and Er

An investigation of the quaternary Ln2O3-SrO-NiO-CuO system has shown that compounds of the formula Ln2−xSrxNi0.8Cu0.2O4−δ (0 < x < 2) with Ln = La, Nd and Gd adopt the K2NiF4-type structure, but a new phase of stoichiometric composition is formed only at x = 1.67 (LnSr5Ni2.4Cu0.6O11) with the smaller lanthanides cations Dy, Ho and Er. All the samples have been prepared at 1150 °C in 1 atm of O2 gas flow using conventional solid state methods. Rietveld refinement of their crystal structures from powder X-ray diffraction data confirms that they adopt the tetragonal structure (space group I4/mmm, Z = 2). Magnetic susceptibility data for Ln2−xSrxNi0.8Cu0.2O4−δ (0 < x < 2) with Ln = La, Nd, Gd, Dy, Ho and Er between 2 and 350 K show Curie-Weiss behavior at higher temperatures characteristic of Ln3+ cation.