Preparation, characterization, and magnetic properties of the solid solution series: Ca4−xNixIrO6 (x = 0.1, 0.2, 0.3, 0.4)

The new one-dimensional oxides Ca4− xNixIrO6 (x = 0.1, 0.2, 0.3, 0.4) have been synthesized by standard solid-state reactions. The compounds crystallize with trigonal (rhombohedral) symmetry in the space group R3̄c, Z = 6, for Ca3.9Ni0.1IrO6 a = 9.32009(7) Å, c = 11.19945(9) Å; for Ca3.8Ni0.2IrO6 a = 9.30830(7) Å, c = 11.1688(1) Å; for Ca3.7Ni0.3IrO6 a = 9.30142(7) Å, c = 11.1509(1) Å; for Ca3.6Ni0.4IrO6 a = 9.29038(7) Å, c = 11.12126(9) Å. Ca4− xNixIrO6 (x = 0.1, 0.2, 0.3, 0.4) are isotypic to compounds of the A4PtO6 (A = Ca, Sr, Ba) structure type. All the structures have been determined by Rietveld refinement of powder X-ray diffraction data. The structure consists of infinite one-dimensional chains of alternating face-sharing IrO6 octahedra and (Ca/Ni)O6 trigonal prisms. The chains are separated by the calcium cations, which are in a distorted square antiprismatic coordination. Magnetic measurements revealed that the samples of Ca4−xNixIrO6 (x = 0.1, 0.2, 0.3, 0.4) follow Curie-Weiss behavior at temperatures above 100 K, with μeff values consistent with an oxidation state of +4 for Ir and +2 for Ni. The compounds Ca4−xNixIrO6 (x = 0.1, 0.2, 0.3) undergo a single antiferromagnetic transition between TN = 5 and 10 K. Ca4−xNixIrO6 (x = 0.4) undergoes two antiferromagnetic transitions at approximately TN1 = 13 K and TN2 = 5 K.