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Title: Structural chemistry and magnetic properties of Y{sub 2}CoGe{sub 4}O{sub 12}

Polycrystalline Y{sub 2}CoGe{sub 4}O{sub 12} has been prepared by standard ceramic methods. The crystal structure (space group P4/nbm; a=9.8465(2), c=4.92986(9) Å) consists of metal-rich layers separated from each other by Ge{sub 4}O{sub 12} groups comprised of four corner-sharing GeO{sub 4} tetrahedra. Two cation sites lie within the layers; an eight-coordinate site occupied by yttrium and a six-coordinate site occupied by a 1:1 disordered distribution of yttrium and cobalt. Neutron diffraction revealed two-fold disorder on the oxide sublattice; this has been elucidated using Co K-edge EXAFS spectroscopy. The availability of two sites allows each oxide ion to accommodate the coordination preferences of its single Co/Y neighbour; the GeO{sub 4} tetrahedra distort to absorb any consequent strain. The octahedron of anions around each Co{sup 2+} cation shows a pseudo-tetragonal distortion with a strain (Co–O){sub eq}–(Co–O){sub ax}/(Co–O){sub eq}=−0.173. This results in an unusually large effective magnetic moment of 6.05 µ{sub B} per Co{sup 2+} cation. - Graphical abstract: A distorted coordination environment leads to an unusually large effective magnetic moment of Co{sup 2+} in Y{sub 2}CoGe{sub 4}O{sub 12}. - Highlights: • Co{sup 2+} and Y{sup 3+} occupy the same site in a disordered manner. • Distorted coordination geometry around Co{sup 2+} results inmore » an unusually large effective magnetic moment. • Use of neutron diffraction and EXAFS to probe average structure and local structure, respectively.« less
Authors:
 [1] ;  [2] ; ;  [2] ;  [3]
  1. Department of Materials Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027 (China)
  2. Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QR (United Kingdom)
  3. School of Physical Sciences, Ingram Building, University of Kent, Canterbury, Kent CT2 7NH (United Kingdom)
Publication Date:
OSTI Identifier:
22486735
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 228; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; CERAMICS; CHEMISTRY; COBALT COMPOUNDS; COBALT IONS; CRYSTAL STRUCTURE; FINE STRUCTURE; GERMANATES; LATTICE PARAMETERS; LAYERS; MAGNETIC MOMENTS; MAGNETIC PROPERTIES; NEUTRON DIFFRACTION; POLYCRYSTALS; STRAINS; X-RAY SPECTROSCOPY; YTTRIUM COMPOUNDS; YTTRIUM IONS