Impact of cationic vacancies on the physical characteristics of multiferroic GdMnO3

The effects of cationic vacancies on the structural, dielectric, and magnetic properties are investigated in polycrystalline GdMnO3 samples. Samples with reduced cationic vacancies are synthesized by annealing under the forming gas atmosphere. The x-ray photoelectron spectroscopy studies show evidence for excess oxygen in terms of the Mn4+ content and reveal the increase in the Mn3+/Mn4+ ratio with increase in annealing time under forming gas conditions. Dielectric studies reveal two thermally activated relaxations in the low and high temperature regimes. Notably, the near stoichiometric Mn3+ rich samples show a negative temperature coefficient of ac conductivity in a certain temperature region along with better insulating properties. The magnetic measurements exhibit a gradual increase in the onset of weak ferromagnetic transition temperature with increase in the Mn3+ content in the sample and coincides with the Neel temperature (42 K) near stoichiometric composition. The studies demonstrate the effect of subtle change in oxygen non-stoichiometry on the dielectric and magnetic properties and bring out the importance of controlling stoichiometry in GdMnO3. Published by AIP Publishing.