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

Ceramics International Volume: 40 Issue: 8 Pages: 13643-13648 Published: 2014

a) Scanning electron micrograph of a representative samples of BiMn2O5 manganite powders obtained by the urea combustion method, followed by heat treatment in air at 800 ºC for 4 h. b) Scanning elements analysis of the BiMn2O5 sample showing a homogenous elements distribution for Bismuth, Manganese and Oxygen. c) Scanning electron micrograph of representative samples of Bi0.9Eu0.1Mn2O5 powders obtained by the urea combustion method, followed by heat treatment in air at 900 ºC for 4 h. d) Scanning elements analysis of the Bi0.9Eu0.1Mn2O5 sample showing a homogenous elements distribution for Europium, Bismuth, Manganese and Oxygen.

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Writers: Rafael A. Ferreira, Maria E. dos Santos, Cássio Morilla-Santos, Ronan Lebullenger, Octavio Peña, Paulo N. Lisboa-Filho

Keywords: : Powders: chemical preparation; X-ray methods; Magnetic properties; Perovskites

Abstract: Polycrystalline oxide materials with nominal compositions BiMn2O5 and Bi0.9Eu0.1Mn2O5were 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 Néel temperature (TN) of 41 K and a Curie–Weiss temperature ΘCW of −277 K, while Bi0.9Eu0.1Mn2O5 displayed a ferrimagnetic behavior with a TC of 44 K and ΘCW 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.

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