Crystal structure, magnetic and dielectric behavior of h-LuMnxO3±δ ceramics (0.95≤x≤1.04)

Abstract

Lattice constants, magnetic properties and dielectric behavior of h-LuMnxO3±δ solid solution (0.95≤x≤1.04) of bulk ceramic samples prepared by the solid state reaction method were studied to determine the role of stoichiometry changes on the crystalline structure and magneto-electric coupling. It is found that increasing of Mn content results in reduction of cell volume of h-LuMnxO3±δ ceramics mostly due to shrinkage of a-axis length. The antiferromagnetic interactions of Mn3+ ions weaken with cell volume contraction. A weak ferromagnetic contribution appeared in all samples and extends up to the Neel temperature, TN. Irreversibility in temperature dependent magnetic measurements already reported for stoichiometric compositions of hexagonal RMnO3 oxides appears for all h-LuMnxO3±δ samples right below Neel ordering transition. An increase of magnetic coercive field and magnetization on cooling below TN in samples is observed in field dependent magnetization and rises as x increases. In addition to the antiferromagnetic ordering transition at TN, two anomalies of the temperature dependent magnetic susceptibility and dielectric constant are identified below TN, centered at 69K and 31K respectively, being probably due to inhomogeneity of the crystalline structure inside ceramic grains. Changes of the dielectric constant at TN can be attributed to magneto-electric coupling in the off-stoichiometric hexagonal LuMnxO3±δ lattice. The behavior of the dielectric relaxation follows a thermally activated mechanism with activation energy values characteristic of polaron hoping.