Crystal Structure and Magnetic Properties of the Novel Hollandite Ba_1.3Co_1.3Ti_6.7O₁₆

Abstract

Single crystals of the new barium hollandite Ba 1.3 Co 1.3 Ti 6.7 O 16 were obtained from a BaCl 2 flux (I2/m, Z = 1, a = 9.9470(4), b = 2.9714(2), c = 10.2260(5)Å, β = 90.906(2) • ). In the crystal structure piles of Ba atoms are situated within a framework of edge-and vertex-sharing octahedra (Co,Ti)O 6 . The composition was deduced from microprobe analyses, structure refinements and charge balance arguments in agreement with the observed magnetic properties. The temperature dependence of the magnetic susceptibility χ(T ) of Ba 1.3 Co 1.3 Ti 6.7 O 16 single crystals reveals paramagnetism down to 2 K. The value of the Co magnetic moment deduced from the Curie-Weiss law agrees well with the theoretical value of the high-spin state spin-only moment of µ eff = 3.87 µ B for Co 2+ (S = 3/2).

Inducing Ferrimagnetism in Insulating Hollandite Ba1.2Mn8O16

“…The ferrimagnetic behavior of the BCMO sample contrasts with the Co-doped analogue of a titanium hollandite, Ba 1.3 Co 1.3 Ti 6.7 O 16 , studied by Shlyk et al, which did not demonstrate any long-range magnetic order down to 2 K. Extrapolation of the high-temperature paramagnetic fit for the titanate hollandite produced a Curie–Weiss constant of θ CW = 6.4 K, indicative of very weak ferromagnetic coupling between the Co ions . Likewise, the study by Moetakef et al revealed no long-range magnetic ordering in the hollandite K 1.4 Co 0.75 Ti 7.25 O 16 .…”