Antiferromagnetic ordering in Li2MnO3 single crystals with a two-dimensional honeycomb lattice

Li2MnO3 consists of a layered Mn honeycomb lattice separated by a single layer of LiO6 octahedra along the c-axis. By using single crystal Li2MnO3 samples, we have examined the physical properties and carried out both powder and single crystal neutron diffraction studies to determine that Mn moments order antiferromagnetically at T-N = 36 K with an ordered magnetic moment of 2.3 mu(B) perpendicular to the ab plane. We have also discovered that about 35% of the full magnetic entropy is released in the supposedly simple paramagnetic phase, indicative of unusual spin dynamics at higher temperature.