Antiferromagnetic ordering in Li2MnO3single 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 TN = 36 K with an ordered magnetic moment of 2.3 μB 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.