New germanates RCrGeO5 (R = Nd-Er, Y): Synthesis, structure, and properties

The new complex germanates RCrGeO5 (R = Nd-Er, Y) have been synthesized and investigated by means of X-ray powder diffraction, electron microscopy, magnetic Susceptibility and specific heat measurements. All the compounds are isostructural and crystallize in the orthorhombic symmetry, space group Pbam, and Z = 4. The crystal structure of RCrGeO5, as refined using X-ray powder diffraction data, includes infinite chains built by edge-sharing Cr+3O6 octahedra with two alternating Cr-Cr distances. The chains are combined into a three-dimensional framework by Ge2O8 groups consisting of two edge-linked square pyramids oriented in opposite directions. The resulting framework contains pentagonal channels where rare-earth elements are located, Thus, RCrGeO5 germanates present new examples of RMn2O5-type compounds and show ordering of Cr+3 and Ge+4 cations. Electron diffraction as well as high-resolution electron microscopy confirm the Structure solution. Magnetic susceptibility data for R = Nd, Sm, and Eu are qualitatively consistent with the presence of isolated 3d (antiferromagnetically Coupled Cr+3 cations) and 4f(R+3) spin Subsystems in the RCrGeO5 Compounds. NdCrGeO5 undergoes long-range magnetic ordering at 2.6 K, while SmCrGeO5 and EuCrGeO5 do not show any phase transitions down to 2 K. (C) 2008 Elsevier Inc. All rights reserved.