CoSe2O5 has a crystal structure consisting of zig-zag chains of edge shared CoO6 octahedra running along the c axis, with the chains separated by Se2O52− units. Magnetic susceptibility measurements indicate a transition at 8.5 K to an ordered state. We investigate here the nature of this magnetic ordering using magnetization and specific heat measurements in addition to powder neuttron diffraction. A transition to long-range antiferromagnetic order is found below TN = 8.5 K as identified by magnetic susceptibility measurements and magnetic Bragg reflections, with a propagation vector k = 0. The magnetic structure shows that the moments align perpendicular to the c-axis, but with the spins canting with respect to the a axis by, alternately, +8∘ and −8∘. Interestingly, the low-field magnetic susceptibility does not show the anticipated cusp-like behavior expected for a well-ordered antiferromagnet. When the susceptibility is acquired under field-cooling conditions under a 10 kOe field, the the usual downturn expected for antiferromagnetic ordering is obtained. Heat capacity measurements at low temperatures indicate the presence of gapped behavior with a gap of 6.5 K.
@article{arxiv.0903.2513,
title = {Magnetic Structure and Susceptibility of CoSe$_2$O$_5$: A Low Dimensional Antiferromagnet},
author = {Brent C. Melot and Brian Paden and Ram Seshadri and Ambesh Dixit and Gavin Lawes and Emmanuelle Suard},
journal= {arXiv preprint arXiv:0903.2513},
year = {2012}
}