Atomic and magnetic long-range orderings in BaLaMRuO6 (M = Mg and Zn)

The crystal structures of double perovskite BaLaMRuO6 (M = Mg, Zn) obtained from the refinements on both X-ray and neutron diffraction data, different from those reported previously that used either X-ray or neutron diffracti on data alone, are reported. The room temperature X-ray and neutron data we re refined with a model in the tetragonal space group I4/m (a = 5.6230(4), c = 7.964(1) Angstrom, V = 251.81(4) Angstrom(3) for M = Mg; 5.6521(3), c = 7.9987(9) Angstrom, V = 255,53(3) Angstrom(3) for M = Zn), The low-tempera ture neutron diffraction data of the two compounds are also refined in the same space group (a = 5.6156(4), 7.953(1) Angstrom, V = 250.80(4) Angstrom( 3) for M = Mg at 13 K; a = 5.6418(4), c = 7.981(1) Angstrom, V = 254.03(4) Angstrom(3) for M = Zn at 10 K). Both compounds show almost complete orderi ng of B-site atoms (M/Ru), For both compounds, the low-temperature neutron diffraction data below about 20 K showed magnetic diffraction peaks that co uld be accounted for with a Type I antiferromagnetic ordering of Ru spins i n an atomically ordered double perovskite structure. These compounds showed discrepancies between field cooled and zero field cooled magnetization dat a below the antiferromagnetic ordering temperatures. (C) 2000 Academic Pres s.