کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1331505 | 1500088 | 2015 | 6 صفحه PDF | دانلود رایگان |
• Co2+ and Y3+ occupy the same site in a disordered manner.
• Distorted coordination geometry around Co2+ results in an unusually large effective magnetic moment.
• Use of neutron diffraction and EXAFS to probe average structure and local structure, respectively.
Polycrystalline Y2CoGe4O12 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 Ge4O12 groups comprised of four corner-sharing GeO4 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 GeO4 tetrahedra distort to absorb any consequent strain. The octahedron of anions around each Co2+ cation shows a pseudo-tetragonal distortion with a strain (Co–O)eq–(Co–O)ax/(Co–O)eq=−0.173. This results in an unusually large effective magnetic moment of 6.05 µB per Co2+ cation.
A distorted coordination environment leads to an unusually large effective magnetic moment of Co2+ in Y2CoGe4O12.Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 228, August 2015, Pages 183–188