Fe-site assignments in Y1Ba2Cu3O7 revisited |
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Authors: | P Boolchand D McDaniel C Blue Y Wu R Enzweiler K Elgaid R Burrows |
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Institution: | (1) Department of Electrical and Computer Engineering, University of Cincinnati, 45221-0030 Cincinnati, OH, USA;(2) Department of Chemistry, University of Cincinnati, 45221-0172 Cincinnati, OH, USA |
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Abstract: | A new symmetric Fe3+ site (labelled E) (δ=0.28(2) mm/s and Δ=0.15 mm/s) is observed in the R1Ba2Cu3O7 family of superconductors for R=Y and Eu. The decay and growth of site E are established in two seemingly unrelated experiments,
one as a function of room temperature aging for R=Y, and the other as a function of oxygen loading at elevated temperatures
and pressures for R=Eu. In each experiment, the results show that site E is genetically related to the well documented chainsites
A(Δ=1.9 mm/s), C(Δ=1.1 mm/s) and D(Δ=1.6 mm/s). We propose that site E represents a quasi-octahedral chain-site having pairs
of O(1), O(4) and O(5) nearestneighbor oxygen sites. The two remaining doublets, B(Δ≈0.4 mm/s) and B′(Δ=0.78 mm/s) represent
Fe3+ dopant sites present in the all-important CuO2 planes, possessing coordination numbers of 6 and 5, respectively. |
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