Abstract
AbstractPolycrystalline samples of La2MMnO6(M= Co and Mg) were prepared by a combined gel‐combustion and high temperature reaction method. The samples were annealed in different oxygen partial pressure (pO2) and characterized by powder XRD, SQUID magnetometry,acimpedance spectroscopy, and electron paramagnetic resonance techniques. Monoclinic (P21/n) and rhombohedral (R$\bar{3}$) lattices were observed for La2CoMnO6and La2MgMnO6, respectively. On annealing in inert atmosphere, La2MgMnO6partially converted to monoclinic La2CoMnO6type structure, whereas no structural change was observed in La2CoMnO6. Dielectric studies of La2CoMnO6indicated relaxor like behavior with polaronic conduction, which systematically decreased with the increase inpO2of the annealing atmosphere. Magnetic studies indicated multiple ferromagnetic phase transitions in La2CoMnO6and a spin‐glass like phase transition in La2MgMnO6. The fraction of ferromagnetic phases of La2CoMnO6was significantly dependent on the annealing environments. The variations of magnetic and dielectric properties of samples were related to the fluctuation of oxidation state of transition metal ions and oxygen vacancies in the samples.
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