Magnetic, thermal, and neutron diffraction studies of a coordination polymer: bis(glycolato)cobalt(ii)

Abstract

The two-dimensional quadratic lattice magnet, bis(glycolato)cobalt(II) ([Co(HOCH₂CO₂)₂]), showed antiferromagnetic ordering at 15.0 K and an abrupt increase in magnetisation at H = 22 600 Oe and 2 K, thereby acting as a metamagnet. Heat capacity measurements revealed that the associated entropy change ΔS around the transition temperature was evaluated to be 6.20 J K⁻¹ mol⁻¹ and that the Co(II) ion had the total angular momentum of J = 1/2 at low temperatures. Neutron diffraction studies suggested that the magnetic moment vectors of the Co(II) ions had an amplitude of 3.59μ_B and were not aligned in a fully antiparallel fashion to those of their neighbours, which caused canting between the magnetic moment vectors in the sheet. The canting angle was determined to be 7.1°. Canting induced net magnetisation in the sheet, but this magnetisation was cancelled between sheets. The magnetisations in the sheets were oriented parallel to the magnetic field at the critical magnetic field.