New ferromagnetic La3Co2TaO9 double perovskite: Structural and magnetic properties

The new double perovskite La3Co2TaO9 has been prepared by a solid-state procedure. The crystal and magnetic structures have been studied from X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD) data. Rietveld refinements were performed in the monoclinic space group P2(1)/n. The structure consists of an ordered array of alternating B'O-6 and B '' O-6 octahedra sharing corners, tilted along the three pseudocubic axes according to the Glazer notation a(-)b(-)c(+). Rietveld refinements show that at RT the cell parameters are a = 5.6005(7)angstrom. b = 5.6931(7)angstrom, c = 7.9429(9)angstrom and beta = 89.9539(7)degrees, and the refined crystallographic formula of this double perovskite can be written as La-2(Co)(2d)(Co1/3Ta2/3)(2c)O-6. Magnetization measurements and low-temperature NPD data show that the perovskite is a ferromagnet with T-C = 72 K. At high Tit follows the Curie-Weiss law with an effective magnetic moment of 3.82 mu(B) per Co ion which is very close to spin only Co2+ (HS). (C) 2009 Elsevier B.V. All rights reserved.