Crystal Structures and Magnetic Properties of Ordered Perovskites Ba2LnNbO6 (Ln=Lanthanide Elements)

✍ Scribed by Kou Henmi; Yukio Hinatsu; Nobuyuki M. Masaki

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 218 KB
• Volume: 148
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8460

✦ Synopsis

A series of double-perovskite oxides Ba 2 LnNbO 6 (Ln ‫؍‬ lanthanide elements) were synthesized. Their powder X-ray di4raction measurements and Rietveld analysis show that they are monoclinic with space group P2 1 /n and that Ln 3؉ and Nb 5؉ ions are structurally ordered. Although the average Ln+O bond length increases with the ionic radius of Ln 3؉ , the average Nb+O bond length is nearly constant for all the Ba 2 LnNbO 6 . Magnetic susceptibility measurements show that they are paramagnetic down to 2 K. The 151 Eu MoK ssbauer spectrum for Ba 2 EuNbO 6 indicates that the Eu ion is in the trivalent state and a quadrupole interaction exists in this compound. Both the magnetic susceptibility and the electron paramagnetic resonance (EPR) spectrum measurements show that the Gd 3؉ ion is in the 8 S 7/2 state. In addition, the anisotropic EPR spectrum indicates that the six oxygen coordination around the Gd 3؉ ion has no longer a perfect octahedral symmetry.