New germanates RCrGeO5 (R=Nd-Er, Y): Synthesis, structure, and properties |
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Authors: | Roman V Shpanchenko Alexander A Tsirlin Evgeny V Antipov Joke Hadermann Hiroya Sakurai |
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Institution: | a Department of Chemistry, Moscow State University, Leninskie Gory, Moscow 119992, Russia b Nanophysique et Semiconducteurs Group, CNRS-Institut Néel and CEA-INAC-SP2M, 17 rue des martyrs, 38054 Grenoble Cedex 9, France c EMAT, University of Antwerp, Groenenborgerlaan 171, Antwerp B-2020, Belgium d NIMS, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan |
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Abstract: | 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. |
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Keywords: | Chromium germanium oxide Crystal structure Magnetic properties |
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