The sign of quadrupole interaction and the Goldanskii–Karyagin effect in 57Fe impurity centers in YBa2Cu3O7−<i>δ</i>
V. D. ChecherskiĭPhysicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Kharkov 1V. V. EremenkoPhysicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Kharkov 1V. A. FinkelPhysicotechnical Institute, Academy of Sciences of the Ukrainian SSR, Kharkov 2N. KanerPhysicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Kharkov 1
ABI
Abstract
Mössbauer effect measurements have been carried out on 57Fe impurity nuclei in texturized and powdered YBa2Cu3O7−δ samples with different oxygen concentrations. It is found that Fe atoms occupy three nonequivalent positions at Cu1 sites with coordination numbers 2, 4, and 6, respectively. The sign of the quadrupole interaction constants for the Fe nuclei in positions Cu1 and Cu2 is determined and found to be negative. Anisotropy data for the mean square displacements of impurity atoms in these positions are obtained. It is shown that a direct observation of the Goldanskii–Karyagin effect is hampered by the presence of textures in the powder.
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