Magnetic ordering in CoTa2O6 and NiTa2O6

Magnetic measurements on CoTa2O6 and NiTa2O6 are reported. The samples were obtained by a chemical transport reaction using chlorine as the transporting agent. Susceptibility data show, in contrast to former investigations, long-range magnetic ordering at Tc = 6.64 K (Co) and 10.3 K (Ni). Broad maxima in the magnetic susceptibility above Tc are attributed to low-dimensional short-range magnetic ordering. The relevancy of these observations for the chemistry of the title compounds is discussed.