Raman scattering study and electrical properties characterization of elpasolite perovskites Ln2(BB′)O6 (Ln = La, Sm... Gd and B,B′= Ni, Co, Mn)

Two series of elpasolite perovskites Ln(2)CoMnO(6) and Ln(2)NiMnO(6) (Ln = La, Pr, Nd, Sm, Gd) have been prepared. The electronic band gap and magnetic Curie temperature vary systematically as a function of the rare earth cation size within both series. Here we used Raman scattering spectroscopy along with the results of previous structural studies to show that there is little change in octahedral distortion but significant changes in the octahedral tilting angle upon decreasing lanthanide ionic radius. The data indicate differences in the orbital overlap and bond strengths between the two series of materials that allow us to understand variations in the magnetic and electrical properties within and between the two perovskite series. (C) 2004 Elsevier Inc. All rights reserved.