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

Abstract

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 Néel temperature (TN) of 41K and a Curie–Weiss temperature ΘCW of −277K, while Bi0.9Eu0.1Mn2O5 displayed a ferrimagnetic behavior with a TC of 44K and ΘCW of −270K. The role of Eu+3 and the mechanisms responsible for the magnetic transition are discussed on the basis of chemical bonds and exchange interactions.