Magnetic structure of the quasi-two-dimensional compound CoTa2O6

We report on a detailed investigation of magnetic properties of CoTa2O6 using several techniques: neutron and X-ray diffraction, specific-heat, magnetic susceptibility, and magnetization measurements. The compound shows quasi-two-dimensional behavior due to its layered structure of alternating Co-O and Ta-O planes. We find that all magnetic moments lie entirely in the Co-O planes, along easy axes determined by the orientations of oxygen octahedra that surround the Co ions. The easy axes in successive magnetic planes have relative orientations that differ by 90 degrees. Antiferromagnetic ordering is observed below 6.6 K, with propagation vectors (+/-1/4,1/4,1/4) associated to the two non-equivalent sets of Co2+ ions, whose magnetic moments are perpendicularly oriented. (C) 2009 Elsevier B.V. All rights reserved.