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

Journal Article · Sat Aug 15 00:00:00 EDT 2015 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2015.04.033· OSTI ID:22486735

Liu, Xiao-Qiang ^[1]; Ridout, Joe; Xu, Diming ^[2]; Ramos, Silvia ^[3]

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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)

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 in an unusually large effective magnetic moment. • Use of neutron diffraction and EXAFS to probe average structure and local structure, respectively.

• OSTI ID: 22486735
• Journal Information: Journal of Solid State Chemistry, Vol. 228; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

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