SYNTHESIS, CRYSTAL-STRUCTURE AND MAGNETISM OF SR3SB2NIO9 - A FERRIMAGNETIC PEROVSKITE

A new nickel(II) oxide, Sr3Sb2NiO9, has been synthesised at 1200 degre es C. Rietveld fits to the powder synchrotron X-ray diffraction patter n show that this compound has orthorhombic symmetry [a = 5.6237(1), b = 5.6442(1), c = 7.9574(1) Angstrom at 300 K] and adopts a pseudo-doub le perovskite structure with Sb:Ni ratios of 40:60 and 93:7 at alterna te cation sites. Powder neutron refinements demonstrate that space gro up symmetry is Pnnm between 1.5 and 300 K due to partly disordered rot ations of the Sb/NiO6 octahedra. Sr3Sb2NiO9 behaves as a Curie-Weiss p aramagnet at high temperatures with mu(eff) = 3.25(1) BM per Ni2+ ion and Theta = -119(1) K reflecting dominant antiferromagnetic spin-spin interactions, but a weak ferromagnetic component observed below the or dering temperature of 20 K suggests overall ferrimagnetic behaviour.