Crystal structures and magnetic properties of 6H-perovskites Ba3MRu2O9 (M = Y, In, La, Sm, Eu, and Lu)

Magnetic properties of quaternary oxides Ba3MRu2O9 (M = Y, In, La, Sm, Eu, and Lu) are reported. Rietveld analyses of the X-ray diffraction data indicate that they adopt the 6H-perovskite structure and have the valence state of Ba3M3+ Ru24.5+O9. All compounds are nonmetallic at least over the temperature range of 100-400 K. The magnetic susceptibilities show a broad maximum at 135-370 K except for the La compound, which shows a plateau around 22 K. In addition, another magnetic anomaly is observed at 4.5-12.5 K by the magnetic susceptibility and specific heat measurements for any compound. It is considered that this magnetic behavior is ascribed to the antiferromagnetic coupling between two Ru ions in a Ru2O9 dimer and to the magnetic interaction between the Ru2O9 dimers. (C) 2002 Elsevier Science (USA).