Effect of Eu substitution on the crystallographic and magnetic properties of the BiMn2O5 oxide obtained by urea combustion

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Processo FAPESP: 07/08072-0

Processo FAPESP: 13/07296-2

Polycrystalline oxide materials with nominal compositions BiMn2O5 and Bi0.9Eu0.1Mn2O5 were obtained by urea combustion. Crystallographic studies using X-ray diffraction and Rietveld Refinement techniques showed the formation of single-phase samples for both compositions, crystallizing in a mullite-type orthorhombic perovskite structure, space group Pbam (Z=4). Replacement of Bi+3 by Eu+3 promoted a slight distortion and a unit cell contraction due to a decrease of the c-parameter for Bi0.9Eu0.1Mn2O5. The SEM/EDX techniques confirmed the formation of single-phase materials with excellent mapping distribution. Magnetic measurements showed different behaviors: BiMn2O5 is an antiferromagnet (AFM) with a Neel temperature (T-N) of 41 K and a Curie-Weiss temperature Theta(CW) of -277 K, while Bi0.9Eu0.1Mn2O5 displayed a ferrimagnetic behavior with a T-C of 44K and Theta(CW) of 270 K. The role of Eu+3 and the mechanisms responsible for the magnetic transition are discussed on the basis of chemical bonds and exchange interactions. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.