Bafe3.39(5)Ru2.61(5)O11 And BaCo1.85(6)Ru4.15(6)O11. Preparation, Crystal Structures, And Magnetic And Transport Properties Of Quaternary Transition Metal Oxoruthenates

Abstract

Black plate-like single crystals of BaFe3.39(5)Ru2.61(5)O11 and BaCo1.85(6)Ru4.15(6)O11 were grown from a BaCl2 flux [hexagonal, space group P63/mmc (No. 194), Fe: a = 5.856(1), c = 13.587(1) Å , R1 = 0.029, wR2 = 0.084; Co: a = 5.842(1), c = 13.573(3) Å, R1 = 0.033, wR2 = 0.075]. The crystal structures contain two crystallographic sites with mixed Ru and Fe/Co occupation of different level in octahedral coordination and one site purely occupied by the respective 3d metal. The latter position is in trigonal bipyramidal coordination, with some indication for a displacement of the metal atom towards tetrahedral coordination. According to the charge balance, the ruthenium atoms are incorporated with different electronic situations in the two Ru containing sites. The Co compound may be described as containing Co2+ and Ru5+ next to Ru3+. Magnetic susceptibility data support this assignment. According to magnetization measurements on oriented crystals, BaCo1.85(6)Ru4.15(6)O11 is a soft ferromagnetic material with low coercive field and a spontaneous magnetization below Tc = 105 K. It behaves as an electric conductor. However, BaFe3.39(5)Ru2.61(5)O11 is a narrow band semiconductor material with ferrimagnetic ordering at Tc = 440 K