Abstract
Abstract The synthesis, crystal structure, and magnetic properties of quaternary oxides Ba3Ln2MO9 (Ln = Y, Sm–Gd, Dy–Lu for M = Mo; Ln = Y, Sm–Lu for M = W) are reported. Their powder X-ray diffraction measurements and Rietveld analysis showed that they have a “disordered” perovskite structure, i.e., BaLn2/3M1/3O3 except for Ba3Tb2WO9, and that their structures are monoclinic with space group I2/c (Ln = Y, Sm–Gd, Dy–Yb for M = Mo; Ln = Y, Sm–Lu for M = W) or cubic with space group Pmm (Ln = Lu for M = Mo). Powder neutron diffraction measurements showed that Ba3Tb2WO9 has an ordered perovskite structure and is monoclinic with space group P21/n. Magnetic susceptibility measurements showed that all the Ba3Ln2MO9 compounds are paramagnetic down to 1.8 K. The Tb ions of Ba3Tb2WO9 are in the mixed valence state (+3, +4). Through 151Eu Mössbauer measurements on Ba3Eu2MoO9 and Ba3Eu2WO9, it was found that the Eu ion is in the trivalent state, and that the symmetry of the Eu site is distorted from the octahedral symmetry.
Published Version
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