Elastic behavior of some manganite-based orthorhombic RMnO3 (R = Sm, Eu, Gd, Dy) multiferroics

A series of multiferroic materials with the compositional formula, RMnO3 (where R = Sm, Eu, Gd, Dy) were prepared by the well-known citrate sol-gel technique. After characterizing the samples structurally, a systematic investigation of elastic behavior has been undertaken and it has been found that the elastic moduli are increasing continuously with decreasing ionic radii of the dopant ion. Variation of longitudinal velocity with temperature for all the samples, over a temperature range 80-300 K has also been studied and the observed experimental behavior is explained using four theoretical models. It has been concluded that Lakkad's model explains the variation of Young's modulus with temperature in a better way than the other ones. (c) 2007 Elsevier B. V. All rights reserved.